Sample records for y-ti complex oxides

  1. Stability of Y-Ti-O nanoparticles during laser deposition of oxide dispersion strengthened steel powder

    Euh, Kwangjun; Arkhurst, Barton; Kim, Il Hyun; Kim, Hyun-Gil; Kim, Jeoung Han


    This study investigated the feasibility of a direct energy deposition process for fabrication of oxide dispersion strengthened steel cladding. The effect of the laser working power and scan speed on the microstructural stability of oxide nanoparticles in the deposition layer was examined. Y-Ti-O type oxide nanoparticles with a mean diameter of 45 nm were successfully dispersed by the laser deposition process. The laser working power significantly affected nanoparticle size and number density. A high laser power with a low scan speed seriously induced particle coarsening and agglomeration. Compared with bulk oxide dispersion strengthened steel, the hardness of the laser deposition layer was much lower because of a relatively coarse particle and grain size. Formation mechanism of nanoparticles during laser deposition was discussed.

  2. Complex oxides useful for thermoelectric energy conversion

    Majumdar, Arunava [Orinda, CA; Ramesh, Ramamoorthy [Moraga, CA; Yu, Choongho [College Station, TX; Scullin, Matthew L [Berkeley, CA; Huijben, Mark [Enschede, NL


    The invention provides for a thermoelectric system comprising a substrate comprising a first complex oxide, wherein the substrate is optionally embedded with a second complex oxide. The thermoelectric system can be used for thermoelectric power generation or thermoelectric cooling.

  3. Electron transport across complex oxide heterointerfaces

    Rana, Kumari Gaurav


    Deze these is het eerste verschenen werk dat het gebruik van BEEM om heet elektron transport in complexe oxide heterostructuren te bestuderen, demonstreert. Belangrijke transportparameters van LSMO zoals de hete elektron attenuatie-lengte en de energieafhankelijkheid zijn succesvol verkregen. Dit we

  4. Oxidation Chemistry of Inorganic Benzene Complexes.

    Fleischmann, Martin; Dielmann, Fabian; Balázs, Gábor; Scheer, Manfred


    The oxidation of the 28 VE cyclo-E6 triple-decker complexes [(Cp(R) Mo)2 (μ,η(6) :η(6) -E6 )] (E=P, Cp(R) =Cp(2 a), Cp*(2 b), Cp(Bn) (2 c)=C5 (CH2 Ph)5 ; E=As, Cp(R) =Cp*(3)) by Cu(+) or Ag(+) leads to cationic 27 VE complexes that retain their general triple-decker geometry in the solid state. The obtained products have been characterized by cyclic voltammetry (CV), EPR, Evans NMR, multinuclear NMR spectroscopy, MS, and structural analysis by single-crystal X-ray diffraction. The cyclo-E6 middle decks of the oxidized complexes are distorted to a quinoid (2 a) or bisallylic (2 b, 2 c, 3) geometry. DFT calculations of 2 a, 2 b, and 3 persistently result in the bisallylic distortion as the minimum geometry and show that the oxidation leads to a depopulation of the σ-system of the cyclo-E6 ligands in 2 a-3. Among the starting complexes, 2 c is reported for the first time including its preparation and full characterization.

  5. Modeling Electronic Properties of Complex Oxides

    Krishnaswamy, Karthik

    Complex oxides are a class of materials that have recently emerged as potential candidates for electronic applications owing to their interesting electronic properties. The goal of this dissertation is to develop a fundamental understanding of these electronic properties using a combination of first-principles approaches based on density functional theory (DFT), and Schr odinger-Poisson (SP) simulation (Abstract shortened by ProQuest.

  6. Dual phase TiO(x)N(y)/TiN charge trapping layer for low-voltage and high-speed flash memory application.

    Zhang, Gang; Yoo, Won Jong


    Flash memory using a dual phase TiO(x)N(y)/TiN charge trapping layer has been fabricated and its electrical properties were investigated. The TiO(x)N(y)/TiN layer was formed by partial oxidation of a pre-deposited TiN layer, and the formation of TiO(x)N(y)/SiO(x)N(y) was confirmed by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. The enlarged conduction (deltaphi(c) = 3.6 eV) and valence (deltaphi(v) = 2.5 eV) band offsets of the TiO(x)N(y)/TiN to SiO2 enabled low-voltage (+/- 6 V) and fast programming/erasing (P: 2.7 x 10(4) V/s and E: -5.1 x 10(4) V/s) operations, while the transition layer suppressed the trapped charge leakage, giving rise to good 10-year data retention with less than 35% V(th) decay.

  7. Low Dimensionality Effects in Complex Magnetic Oxides

    Kelley, Paula J. Lampen

    Complex magnetic oxides represent a unique intersection of immense technological importance and fascinating physical phenomena originating from interwoven structural, electronic and magnetic degrees of freedom. The resulting energetically close competing orders can be controllably selected through external fields. Competing interactions and disorder represent an additional opportunity to systematically manipulate the properties of pure magnetic systems, leading to frustration, glassiness, and other novel phenomena while finite sample dimension plays a similar role in systems with long-range cooperative effects or large correlation lengths. A rigorous understanding of these effects in strongly correlated oxides is key to manipulating their functionality and device performance, but remains a challenging task. In this dissertation, we examine a number of problems related to intrinsic and extrinsic low dimensionality, disorder, and competing interactions in magnetic oxides by applying a unique combination of standard magnetometry techniques and unconventional magnetocaloric effect and transverse susceptibility measurements. The influence of dimensionality and disorder on the nature and critical properties of phase transitions in manganites is illustrated in La0.7 Ca0.3MnO3, in which both size reduction to the nanoscale and chemically-controlled quenched disorder are observed to induce a progressive weakening of the first-order nature of the transition, despite acting through the distinct mechanisms of surface effects and site dilution. In the second-order material La0.8Ca0.2MnO3, a strong magnetic field is found to drive the system toward its tricritical point as competition between exchange interactions in the inhomogeneous ground state is suppressed. In the presence of large phase separation stabilized by chemical disorder and long-range strain, dimensionality has a profound effect. With the systematic reduction of particle size in microscale-phase-separated (La, Pr

  8. Integration of functional complex oxide nanomaterials on silicon

    Jose Manuel eVila-Fungueiriño


    Full Text Available The combination of standard wafer-scale semiconductor processing with the properties of functional oxides opens up to innovative and more efficient devices with high value applications that can be produced at large scale. This review uncovers the main strategies that are successfully used to monolithically integrate functional complex oxide thin films and nanostructures on silicon: the chemical solution deposition approach (CSD and the advanced physical vapor deposition techniques such as oxide molecular beam epitaxy (MBE. Special emphasis will be placed on complex oxide nanostructures epitaxially grown on silicon using the combination of CSD and MBE. Several examples will be exposed, with a particular stress on the control of interfaces and crystallization mechanisms on epitaxial perovskite oxide thin films, nanostructured quartz thin films, and octahedral molecular sieve nanowires. This review enlightens on the potential of complex oxide nanostructures and the combination of both chemical and physical elaboration techniques for novel oxide-based integrated devices.

  9. Electrocatalytic water oxidation with a copper(II) polypeptide complex.

    Zhang, Ming-Tian; Chen, Zuofeng; Kang, Peng; Meyer, Thomas J


    A self-assembly-formed triglycylglycine macrocyclic ligand (TGG(4-)) complex of Cu(II), [(TGG(4-))Cu(II)-OH(2)](2-), efficiently catalyzes water oxidation in a phosphate buffer at pH 11 at room temperature by a well-defined mechanism. In the mechanism, initial oxidation to Cu(III) is followed by further oxidation to a formal "Cu(IV)" with formation of a peroxide intermediate, which undergoes further oxidation to release oxygen and close the catalytic cycle. The catalyst exhibits high stability and activity toward water oxidation under these conditions with a high turnover frequency of 33 s(-1).

  10. Electrochemical water oxidation with carbon-grafted iridium complexes.

    deKrafft, Kathryn E; Wang, Cheng; Xie, Zhigang; Su, Xin; Hinds, Bruce J; Lin, Wenbin


    Hydrogen production from water splitting provides a potential solution to storing harvested solar energy in chemical fuels, but this process requires active and robust catalysts that can oxidize water to provide a source of electrons for proton reduction. Here we report the direct, covalent grafting of molecular Ir complexes onto carbon electrodes, with up to a monolayer coverage. Carbon-grafted Ir complexes electrochemically oxidize water with a turnover frequency of up to 3.3 s(-1) and a turnover number of 644 during the first hour. Electrochemical water oxidation with grafted catalysts gave enhanced rates and stability compared to chemically driven water oxidation with the corresponding molecular catalysts. This strategy provides a way to systematically evaluate catalysts under tunable conditions, potentially providing new insights into electrochemical water oxidation processes and water oxidation catalyst design.

  11. Thermodynamic Ground States of Complex Oxide Heterointerfaces

    Gunkel, F.; Hoffmann-Eifert, S.; Heinen, R. A.


    The formation mechanism of 2-dimensional electron gases (2DEGs) at heterointerfaces between nominally insulating oxides is addressed with a thermodynamical approach. We provide a comprehensive analysis of the thermodynamic ground states of various 2DEG systems directly probed in high temperature...... equilibrium conductivity measurements. We unambiguously identify two distinct classes of oxide heterostructures: For epitaxial perovskite/perovskite heterointerfaces (LaAlO3/SrTiO3, NdGaO3/SrTiO3, and (La,Sr)(Al,Ta)O3/SrTiO3), we find the 2DEG formation being based on charge transfer into the interface...

  12. Catalytic Oxidation and Deoxygenation of Renewables with Rhenium Complexes

    Korstanje, T.J.; Klein Gebbink, R.J.M.


    Transformation of renewables has received major research interest in recent years, opening up completely new research areas, in particular in the field of oxidation and deoxygenation. For the oxidation reaction, rhenium complexes, in particular methyltrioxorhenium, are well known for their potential

  13. Instrumentation for Epitaxial Growth of Complex Oxides


    P.O. Box 12211 Research Triangle Park, NC 27709-2211 epitaxy, molecular beam epitaxy, oxide heterostructures REPORT DOCUMENTATION PAGE 11. SPONSOR...The installation of this shielding was founded to dramatically increase the beam stability and mitigate intensity fluctuations. The RHEED source has

  14. Patterning of high mobility electron gases at complex oxide interfaces

    Trier, Felix; Prawiroatmodjo, G. E. D. K.; von Soosten, Merlin


    Oxide interfaces provide an opportunity for electronics. However, patterning of electron gases at complex oxide interfaces is challenging. In particular, patterning of complex oxides while preserving a high electron mobility remains underexplored and inhibits the study of quantum mechanical effects...... where extended electron mean free paths are paramount. This letter presents an effective patterning strategy of both the amorphous-LaAlO3/SrTiO3 (a-LAO/STO) and modulation-doped amorphous-LaAlO3/La7/8Sr1/8MnO3/SrTiO3 (a-LAO/LSM/STO) oxide interfaces. Our patterning is based on selective wet etching...... of amorphous-LSM (a-LSM) thin films, which acts as a hard mask during subsequent depositions. Strikingly, the patterned modulation-doped interface shows electron mobilities up to ∼8 700 cm2/V s at 2 K, which is among the highest reported values for patterned conducting complex oxide interfaces that usually...

  15. Hydrogen Bonding in Phosphine Oxide/Phosphate-Phenol Complexes

    Cuypers, R.; Sudhölter, E.J.R.; Zuilhof, H.


    To develop a new solvent-impregnated resin (SIR) system for the removal of phenols and thiophenols from water, complex formation by hydrogen bonding of phosphine oxides and phosphates is studied using isothermal titration calorimetry (ITC) and quantum chemical modeling. Six different computational m

  16. Molecularly imprinted Ru complex catalysts integrated on oxide surfaces.

    Muratsugu, Satoshi; Tada, Mizuki


    Selective catalysis is critical for the development of green chemical processes, and natural enzymes that possess specialized three-dimensional reaction pockets with catalytically active sites represent the most sophisticated systems for selective catalysis. A reaction space in an enzyme consists of an active metal center, functional groups for molecular recognition (such as amino acids), and a surrounding protein matrix to prepare the reaction pocket. The artificial design of such an integrated catalytic unit in a non-enzymatic system remains challenging. Molecular imprinting of a supported metal complex provides a promising approach for shape-selective catalysis. In this process, an imprinted cavity with a shape matched to a template molecule is created in a polymer matrix with a catalytically active metal site. In this Account, we review our studies on molecularly imprinted metal complex catalysts, focusing on Ru complexes, on oxide surfaces for shape-selective catalysis. Oxide surface-attached transition metal complex catalysts not only improve thermal stability and catalyst dispersion but also provide unique catalytic performance not observed in homogeneous precursors. We designed molecularly imprinted Ru complexes by using surface-attached Ru complexes with template ligands and inorganic/organic surface matrix overlayers to control the chemical environment around the active metal complex catalysts on oxide surfaces. We prepared the designed, molecularly imprinted Ru complexes on SiO(2) surfaces in a step-by-step manner and characterized them with solid-state (SS) NMR, diffuse-reflectance (DR) UV-vis, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller isotherm (BET), X-ray fluorescence (XRF), and Ru K-edge extended X-ray absorption fine structure (EXAFS). The catalytic performances of these Ru complexes suggest that this process of molecular imprinting facilitates the artificial integration of catalytic functions at surfaces. Further advances such

  17. Isocyanide and Phosphine Oxide Coordination in Binuclear Chromium Pacman Complexes.

    Stevens, Charlotte J; Nichol, Gary S; Arnold, Polly L; Love, Jason B


    The new binuclear chromium Pacman complex [Cr2(L)] of the Schiff base pyrrole macrocycle H4L has been synthesized and structurally characterized. Addition of isocyanide, C≡NR (R = xylyl, (t)Bu), or triphenylphosphine oxide donors to [Cr2(L)] gives contrasting chemistry with the formation of the new coordination compounds [Cr2(μ-CNR)(L)], in which the isocyanides bridge the two Cr(II) centers, and [Cr2(OPPh3)2(L)], a Cr(II) phosphine oxide adduct with the ligands exogenous to the cleft.

  18. Catalytic performance of cerium iron complex oxides for partial oxidation of methane to synthesis gas

    LI Kongzhai; WANG Hua; WEI Yonggang; LIU Mingchun


    The cerium iron complex oxides oxygen carder was prepared by the co-precipitation method. The reactions between methane and lattice oxygen from the complex oxides were investigated in a fixed micro-reactor system. The reduced oxygen carrier could be re-oxidized by air and its initial state could be restored. The characterizations of the oxygen carriers were studied using XRD, O2-TPD, and H2-TPR. The results showed that the bulk lattice oxygen of CeO2-Fe2O3 was found to be suitable for the partial oxidation of methane to synthesis gas. There were two kinds of oxygen species on the oxygen carder: the stronger oxygen species that was responsible for the complete oxidation of methane, and the weaker oxygen species (bulk lattice oxygen) that was responsible for the selective oxidation of methane to CO and H2 at a higher temperature. Then, the lost bulk lattice oxygen could be selectively supplemented by air re-oxidation at an appropriate reaction con-dition. CeFeO3 appeared on the oxygen carrier after 10 successive redox cycles, however, it was not bad for the selectivity of CO and H2.

  19. Vanadyl cationic complexes as catalysts in olefin oxidation.

    Nunes, Carla D; Vaz, Pedro D; Félix, Vítor; Veiros, Luis F; Moniz, Tânia; Rangel, Maria; Realista, Sara; Mourato, Ana C; Calhorda, Maria José


    Three new mononuclear oxovanadium(IV) complexes [VO(acac)(R-BIAN)]Cl (BIAN = 1,2-bis{(R-phenyl)imino}acenaphthene, R = H, 1; CH3, 2; Cl, 3) were prepared and characterized. They promoted the catalytic oxidation of olefins such as cyclohexene, cis-cyclooctene, and styrene with both tbhp (tert-butylhydroperoxide) and H2O2, and of enantiopure olefins (S(-)- and R(+)-pinene, and S(-)- and R(+)-limonene) selectively to their epoxides, with tbhp as the oxidant. The TOFs for styrene epoxidation promoted by complex 3 with H2O2 (290 mol mol(-1)V h(-1)) and for cis-cyclooctene epoxidation by 2 with tbhp (248 mol mol(-1)V h(-1)) are particularly good. Conversions reached 90% for several systems with tbhp, and were lower with H2O2. A preference for the internal C=C bond, rather than the terminal one, was found for limonene. Kinetic data indicate an associative process as the first step of the reaction and complex [VO(acac)(H-BIAN)](+) (1(+)) was isolated in an FTICR cell after adding tbhp to 1. EPR studies provide evidence for the presence of a V(IV) species in solution, until at least 48 hours after the addition of tbhp and cis-cyclooctene, and cyclic voltammetry studies revealed an oxidation potential above 1 V for complex 1. DFT calculations suggest that a [VO(H-BIAN)(MeOO)](+) complex is the likely active V(IV) species in the catalytic cycle from which two competitive mechanisms for the reaction proceed, an outer sphere path with an external attack of the olefin at the coordinated peroxide, and an inner sphere mechanism starting with a complex with the olefin coordinated to vanadium.

  20. Final technical report. Bimetallic complexes as methanol oxidation catalysts

    McElwee-White, Lisa


    Our work on the electrocatalyzed oxidation of methanol was initially motivated by the interest in methanol as an anodic reactant in fuel cells. The literature on electrochemical oxidation of alcohols can be roughly grouped into two sets: fuel cell studies and inorganic chemistry studies. Work on fuel cells primarily focuses on surface-catalyzed oxidation at bulk metal anodes, usually Pt or Pt/Ru alloys. In the surface science/electrochemistry approach to these studies, single molecule catalysts are generally not considered. In contrast, the inorganic community investigates the electrooxidation of alcohols in homogeneous systems. Ruthenium complexes have been the most common catalysts in these studies. The alcohol substrates are typically either secondary alcohols (e.g., isopropanol) such that the reaction stops after 2 e{sup -} oxidation to the aldehyde and 4 e{sup -} oxidation to the carboxylic acid can be observed. Methanol, which can also undergo 6 e{sup -} oxidation to CO{sub 2}, rarely appears in the homogeneous catalysis studies. Surface studies have shown that two types of metal centers with different functions result in more effective catalysts than a single metal; however, application of this concept to homogeneous systems has not been demonstrated. The major thrust of the work is to apply this insight from the surface studies to homogeneous catalysis. Even though homogeneous systems would not be appropriate models for active sites on Pt/Ru anodes, it is possible that heterobimetallic catalysts could also utilize two metal centers for different roles. Starting from that perspective, this work involves the preparation and investigation of heterobinuclear catalysts for the electrochemical oxidation of methanol.

  1. Oxidation of cuprous stellacyanin by aminopolycarboxylatocobaltate(III) complexes.

    Yoneda, G S; Mitchel, G L; Blackmer, G L; Holwerda, R A


    Rate parameters are reported for the oxidation of cuprous stellacyanin by Co(PDTA)-(k(25.0 degrees) = 17.9 M(-1)sec(-1), deltaH not equal to = 8.5 kcal/mol, deltaH not equal to = 8.5 kcal/mol, deltaS not equal to = -24 cal/mol-deg; pH 7.0, Mu 0.5 M) and Co(CyDTA)-(k(25.1 degrees) = 17.0 M(-1)sec(-1), deltaH not equal to = 8.7 kcal/mol, deltaS not equal to = -24 cal/mol-deg; pH 7.0 mu 0.5 M). The first order Co(PDTA)- and Co(CyDTA)- dependences observed over wide concentration ranges contrast with the saturation behavior reported previously for Co(EDTA)- as the oxidant. It is concluded that the- CH3 and -(CH2)4-substituents of PDTA and CyDTA, respectively, prevent the alkylated derivatives of Co(EDTA)- from hydrogen bonding with the reduced blue protein, causing precursor complex formation constants to fall far below that of 149M(-1) (25.1 degrees) observed for the EDTA complex. The similarity between deltaH not equal to and deltaS not equal to values for the oxidation of stellacyanin by Co(PDTA)- and Co(CyDTA)- indicates that the size of alkyl substituents linked to the carbon atoms of the EDTA ethylenediamine backbone has little influence on activation requirements for Cu(I) to Co(III) electron transfer. The electron transfer reactivity of aminopolycarboxylatocobalt(III) complexes with cuprous stellacyanin therefore appears to be linked to the accessibility of one or more of the ligated acetate groups to outer-sphere contact with the type 1 Cu(I) center. Saturation in kobsd vs. [oxidant] plots found for the reactions of Co(PDTA)- and Co(CyDTA)- with stellacyanin at pH 6 and at pH 7 in the presence of EDTA is attributed to the formation of "dead-end" oxidant-protein complexes.

  2. Pneumococcal gene complex involved in resistance to extracellular oxidative stress.

    Andisi, Vahid Farshchi; Hinojosa, Cecilia A; de Jong, Anne; Kuipers, Oscar P; Orihuela, Carlos J; Bijlsma, Jetta J E


    Streptococcus pneumoniae is a gram-positive bacterium which is a member of the normal human nasopharyngeal flora but can also cause serious disease such as pneumonia, bacteremia, and meningitis. Throughout its life cycle, S. pneumoniae is exposed to significant oxidative stress derived from endogenously produced hydrogen peroxide (H(2)O(2)) and from the host through the oxidative burst. How S. pneumoniae, an aerotolerant anaerobic bacterium that lacks catalase, protects itself against hydrogen peroxide stress is still unclear. Bioinformatic analysis of its genome identified a hypothetical open reading frame belonging to the thiol-specific antioxidant (TlpA/TSA) family, located in an operon consisting of three open reading frames. For all four strains tested, deletion of the gene resulted in an approximately 10-fold reduction in survival when strains were exposed to external peroxide stress. However, no role for this gene in survival of internal superoxide stress was observed. Mutagenesis and complementation analysis demonstrated that all three genes are necessary and sufficient for protection against oxidative stress. Interestingly, in a competitive index mouse pneumonia model, deletion of the operon had no impact shortly after infection but was detrimental during the later stages of disease. Thus, we have identified a gene complex involved in the protection of S. pneumoniae against external oxidative stress, which plays an important role during invasive disease.

  3. Selective oxidations of a dithiolate complex produce a mixed sulfonate/thiolate complex.

    Chohan, Balwant S; Maroney, Michael J


    Oxygenation or peroxidation of a planar, tetracoordinate, low-spin nickel(II) complex of a N2S2-donor ligand, (N,N'-dimethyl-N,N'-bis(2-mecaptoethyl)-1, 3-propanediaminato)nickel(II), proceeds via the formation of a mixed sulfinate/thiolate complex and leads to the production of a novel dimeric complex containing both sulfonate and thiolate ligands. Thus, reaction proceeds via selective oxidation of the sulfinate sulfur atom, leaving the thiolate reduced. The novel sulfonate/thiolate complex has been isolated and characterized by electospray ionization mass spectrometry and single-crystal X-ray diffraction. Crystals form in the monoclinic space group P2(1)/c with cell dimensions a = 8.4647(12) A, b = 12.592(3) A, and c = 12.531(2) A, angles alpha = gamma = 90 degrees and beta = 106.645(11) degrees , and Z = 2. The structure was refined to R = 5.20% and R(w) = 12.86% [I > 2sigma(I)]. The isolation of this mixed sulfonate/thiolate complex from oxidation of a mixed sulfinate/thiolate complex provides experimental evidence for the formation of a sulfonate ligand via a Ni-O-O-SO2R intermediate, as suggested by recent density functional theory calculations.

  4. Comparison of topotactic fluorination methods for complex oxide films

    E. J. Moon


    Full Text Available We have investigated the synthesis of SrFeO3−αFγ (α and γ ≤ 1 perovskite films using topotactic fluorination reactions utilizing poly(vinylidene fluoride as a fluorine source. Two different fluorination methods, a spin-coating and a vapor transport approach, were performed on as-grown SrFeO2.5 films. We highlight differences in the structural, compositional, and optical properties of the oxyfluoride films obtained via the two methods, providing insight into how fluorination reactions can be used to modify electronic and optical behavior in complex oxide heterostructures.

  5. Oxidative peptide /and amide/ formation from Schiff base complexes

    Strehler, B. L.; Li, M. P.; Martin, K.; Fliss, H.; Schmid, P.


    One hypothesis of the origin of pre-modern forms of life is that the original replicating molecules were specific polypeptides which acted as templates for the assembly of poly-Schiff bases complementary to the template, and that these polymers were then oxidized to peptide linkages, probably by photo-produced oxidants. A double cycle of such anti-parallel complementary replication would yield the original peptide polymer. If this model were valid, the Schiff base between an N-acyl alpha mino aldehyde and an amino acid should yield a dipeptide in aqueous solution in the presence of an appropriate oxidant. In the present study it is shown that the substituted dipeptide, N-acetyl-tyrosyl-tyrosine, is produced in high yield in aqueous solution at pH 9 through the action of H2O2 on the Schiff-base complex between N-acetyl-tyrosinal and tyrosine and that a great variety of N-acyl amino acids are formed from amino acids and aliphatic aldehydes under similar conditions.

  6. New nitric oxide donors based on ruthenium complexes

    C.N. Lunardi


    Full Text Available Nitric oxide (NO donors produce NO-related activity when applied to biological systems. Among its diverse functions, NO has been implicated in vascular smooth muscle relaxation. Despite the great importance of NO in biological systems, its pharmacological and physiological studies have been limited due to its high reactivity and short half-life. In this review we will focus on our recent investigations of nitrosyl ruthenium complexes as NO-delivery agents and their effects on vascular smooth muscle cell relaxation. The high affinity of ruthenium for NO is a marked feature of its chemistry. The main signaling pathway responsible for the vascular relaxation induced by NO involves the activation of soluble guanylyl-cyclase, with subsequent accumulation of cGMP and activation of cGMP-dependent protein kinase. This in turn can activate several proteins such as K+ channels as well as induce vasodilatation by a decrease in cytosolic Ca2+. Oxidative stress and associated oxidative damage are mediators of vascular damage in several cardiovascular diseases, including hypertension. The increased production of the superoxide anion (O2- by the vascular wall has been observed in different animal models of hypertension. Vascular relaxation to the endogenous NO-related response or to NO released from NO deliverers is impaired in vessels from renal hypertensive (2K-1C rats. A growing amount of evidence supports the possibility that increased NO inactivation by excess O2- may account for the decreased NO bioavailability and vascular dysfunction in hypertension.

  7. Stoichiometry control of complex oxides by sequential pulsed-laser deposition from binary-oxide targets

    Herklotz, A. [ORNL, Materials Science and Technology Division, Bethel Valley Road, Oak Ridge, Tennessee 37831-6056 (United States); Martin Luther University Halle-Wittenberg, Institute for Physics, Von-Danckelmann-Platz 3, 06120 Halle (Germany); Dörr, K. [Martin Luther University Halle-Wittenberg, Institute for Physics, Von-Danckelmann-Platz 3, 06120 Halle (Germany); Ward, T. Z.; Eres, G. [ORNL, Materials Science and Technology Division, Bethel Valley Road, Oak Ridge, Tennessee 37831-6056 (United States); Christen, H. M.; Biegalski, M. D. [ORNL, Center for Nanophase Materials Sciences, Bethel Valley Road, Oak Ridge, Tennessee 37831-6496 (United States)


    To have precise atomic layer control over interfaces, we examine the growth of complex oxides through the sequential deposition from binary targets by pulsed laser deposition. In situ reflection high-energy electron diffraction (RHEED) is used to control the growth and achieve films with excellent structural quality. The growth from binary oxide targets is fundamentally different from single target growth modes and shows more similarities to shuttered growth by molecular beam epitaxy. The RHEED intensity oscillations of non-stoichiometric growth are consistent with a model of island growth and accumulation of excess material on the surface that can be utilized to determine the correct stoichiometry for growth. Correct monolayer doses can be determined through an envelope frequency in the RHEED intensity oscillations. In order to demonstrate the ability of this growth technique to create complex heterostructures, the artificial n = 2 and 3 Sr{sub n+1}Ti{sub n}O{sub 3n+1} Ruddlesden-Popper phases are grown with good long-range order. This method enables the precise unit-cell level control over the structure of perovskite-type oxides, and thus the growth of complex materials with improved structural quality and electronic functionality.

  8. Strain-induced phenomenon in complex oxide thin films

    Haislmaier, Ryan

    Complex oxide materials wield an immense spectrum of functional properties such as ferroelectricity, ferromagnetism, magnetoelectricity, optoelectricity, optomechanical, magnetoresistance, superconductivity, etc. The rich coupling between charge, spin, strain, and orbital degrees of freedom makes this material class extremely desirable and relevant for next generation electronic devices and technologies which are trending towards nanoscale dimensions. Development of complex oxide thin film materials is essential for realizing their integration into nanoscale electronic devices, where theoretically predicted multifunctional capabilities of oxides could add tremendous value. Employing thin film growth strategies such as epitaxial strain and heterostructure interface engineering can greatly enhance and even unlock novel material properties in complex oxides, which will be the main focus of this work. However, physically incorporating oxide materials into devices remains a challenge. While advancements in molecular beam epitaxy (MBE) of thin film oxide materials has led to the ability to grow oxide materials with atomic layer precision, there are still major limitations such as controlling stoichiometric compositions during growth as well as creating abrupt interfaces in multi-component layered oxide structures. The work done in this thesis addresses ways to overcome these limitations in order to harness intrinsic material phenomena. The development of adsorption-controlled stoichiometric growth windows of CaTiO3 and SrTiO3 thin film materials grown by hybrid MBE where Ti is supplied using metal-organic titanium tetraisopropoxide material is thoroughly outlined. These growth windows enable superior epitaxial strain-induced ferroelectric and dielectric properties to be accessed as demonstrated by chemical, structural, electrical, and optical characterization techniques. For tensile strained CaTiO3 and compressive strained SrTiO 3 films, the critical effects of

  9. Electronic phenomena at complex oxide interfaces: insights from first principles

    Pentcheva, Rossitza [Department of Earth and Environmental Sciences, University of Munich, Theresienstrasse 41, D-80333 Munich (Germany); Pickett, Warren E [Department of Physics, University of California Davis, Davis, CA 95616 (United States)


    Oxide interfaces have attracted considerable attention in recent years due to the emerging novel behavior which does not exist in the corresponding bulk parent compounds. This opens possibilities for future applications in oxide-based electronics and spintronics devices. Among the different materials combinations, heterostructures containing the two simple band insulators LaAlO{sub 3} and SrTiO{sub 3} have advanced to a model system exhibiting unanticipated properties ranging from conductivity, to magnetism, even to superconductivity. Electronic structure calculations have contributed significantly towards understanding these phenomena and we review here the progress achieved in the past few years, also showing some future directions and perspectives. A central issue in understanding the novel behavior in these oxide heterostructures is to discover the way (or ways) that these heterostructures deal with the polar discontinuity at the interface. Despite analogies to polar semiconductor interfaces, transition metal oxides offer much richer possibilities to compensate the valence mismatch, including, for example, an electronic reconstruction. Moreover, electronic correlations can lead to additional complex behavior like charge disproportionation and order, magnetism and orbital order. We discuss in some detail the role of finite size effects in ultrathin polar films on a nonpolar substrate leading to another intriguing feature-the thickness-dependent insulator-to-metal transition in thin LaAlO{sub 3} films on a SrTiO{sub 3}(001) substrate, driven by the impending polar catastrophe. The strong and uniform lattice polarization that emerges as a response to the potential build-up enables the system to remain insulating up to a few layers. However, beyond a critical thickness there is a crossover from an ionic relaxation to an electronic reconstruction. At this point two bands of electron and hole character, separated both in real and in reciprocal space, have been

  10. 3D stereolithography printing of graphene oxide reinforced complex architectures.

    Lin, Dong; Jin, Shengyu; Zhang, Feng; Wang, Chao; Wang, Yiqian; Zhou, Chi; Cheng, Gary J


    Properties of polymer based nanocomposites reply on distribution, concentration, geometry and property of nanofillers in polymer matrix. Increasing the concentration of carbon based nanomaterials, such as CNTs, in polymer matrix often results in stronger but more brittle material. Here, we demonstrated the first three-dimensional (3D) printed graphene oxide complex structures by stereolithography with good combination of strength and ductility. With only 0.2% GOs, the tensile strength is increased by 62.2% and elongation increased by 12.8%. Transmission electron microscope results show that the GOs were randomly aligned in the cross section of polymer. We investigated the strengthening mechanism of the 3D printed structure in terms of tensile strength and Young's modulus. It is found that an increase in ductility of the 3D printed nanocomposites is related to increase in crystallinity of GOs reinforced polymer. Compression test of 3D GOs structure reveals the metal-like failure model of GOs nanocomposites.

  11. Applications of STEM-EELS to complex oxides

    Gázquez, Jaume


    In this chapter we will review a few examples of applications of atomic resolution aberration corrected scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) to complex oxide materials. These are most challenging systems where subtle changes in structure or chemistry may result in colossal responses in macroscopic physical behavior. Here, we will review how atomic resolution compositional mapping can be achieved in manganite thin films and single crystals, highlighting the importance of considering artifacts during quantification. Besides, minor changes in near edge fine structure may take place when the crystalline environment, and hence nearest neighbor configuration, is modified. These can also be tracked by atomic resolution EELS, as will be shown through the study of binary Fe oxides. Also, examples regarding the study of distributions of point defects such as O vacancies in cobaltite thin films will be discussed. In these materials, a combination of epitaxial strain and defects may promote physical behaviors not present in bulk, such as the stabilization of unexpected spin state superlattices. Last, a study of extended defects such as dislocation lines will be reviewed. In particular, we will show how chemical segregation at dislocation cores in yttria-stabilized zirconia grain boundaries results in the generation of static O vacancies that affect the local electrostatic potential and hence, the macroscopic ionic conduction properties. © 2016.

  12. Magnetism in Complex Oxide Heterostructures Determined with Neutron Scattering

    Te Velthuis, Suzanne G. E.


    With the creation of high quality superlattices consisting of complex oxide materials novel materials exhibiting a wide range of interesting phenomena are emerging. Due to the diverse physical properties of complex oxides, (e.g., ferromagnetism, antiferromagnetism, superconductivity), some of which can be varied by doping, the versatility in their applications is large. The physical properties in these new materials, often is tied to the behavior at the interfaces between the different components of the superlattice, and therefore requires detailed knowledge of the relationship between the chemical and electronic composition. Polarized neutron reflectometry (PNR) provides access to the depth-dependent magnitude and orientation of the magnetization and can therefore link the magnetic to the electronic and chemical properties, especially close to these interfaces. Several examples of our work will be presented, including that on La0.7Ca0.3MnO3/ YBa2Cu3O7-δ/ La0.7Ca0.3MnO3 trilayers which exhibit the inverse superconducting spin switch behavior, and where suppression of the magnetization close to the interface, as well as a varying anisotropy axis have been determined [1]. Another example is work on digitally layered analogs of La1-xSrxMnO3, where PNR reveals an asymmetric distribution of the magnetization across the two components (antiferromagnetic) LaMnO3and SrMnO3, which has been linked to structural properties at the interfaces [2]. [4pt] [1] V. Peña, Z. Sefrioui, D. Arias, C. Leon, J. Santamaria, J. L. Martinez, S. G. E. te Velthuis, A. Hoffmann, Phys. Rev. Lett. 94 (2005) 057002. [0pt] [2] S. J. May, A. B. Shah, S. G. E. te Velthuis, M. R. Fitzsimmons, J. M. Zuo, X. Zhai, J. N. Eckstein, S. D. Bader, and A. Bhattacharya, Phys. Rev. B 77 (2008) 174409.


    Yi-jun Huang; Guo-rong Qi; Guan-xi Chen


    Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by 13C-NMR and IR spectra. 1H-NMR analysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecular weight copolymers with various EO content were obtained and their values of molecular weight distribution (MWD) fell in the range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio ofEO + PO to initiator moles used. The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.

  14. Complexation facilitated reduction of aromatic N-oxides by aqueous Fe(II)-tiron complex: reaction kinetics and mechanisms.

    Chen, Yiling; Zhang, Huichun


    Rapid reduction of carbadox (CDX), olaquindox and several other aromatic N-oxides were investigated in aqueous solution containing Fe(II) and tiron. Consistent with previous work, the 1:2 Fe(II)-tiron complex, FeL2(6-), is the dominant reactive species as its concentration linearly correlates with the observed rate constant kobs under various conditions. The N-oxides without any side chains were much less reactive, suggesting direct reduction of the N-oxides is slow. UV-vis spectra suggest FeL2(6-) likely forms 5- or 7-membered rings with CDX and olaquindox through the N and O atoms on the side chain. The formed inner-sphere complexes significantly facilitated electron transfer from FeL2(6-) to the N-oxides. Reduction products of the N-oxides were identified by HPLC/QToF-MS to be the deoxygenated analogs. QSAR analysis indicated neither the first electron transfer nor N-O bond cleavage is the rate-limiting step. Calculations of the atomic spin densities of the anionic N-oxides confirmed the extensive delocalization between the aromatic ring and the side chain, suggesting complex formation can significantly affect the reduction kinetics. Our results suggest the complexation facilitated N-oxide reduction by Fe(II)-tiron involves a free radical mechanism, and the subsequent deoxygenation might also benefit from the weak complexation of Fe(II) with the N-oxide O atom.

  15. New class of phosphine oxide donor-based supramolecular coordination complexes from an in situ phosphine oxidation reaction or phosphine oxide ligands.

    Shankar, Bhaskaran; Elumalai, Palani; Shanmugam, Ramasamy; Singh, Virender; Masram, Dhanraj T; Sathiyendiran, Malaichamy


    A one-pot, multicomponent, coordination-driven self-assembly approach was used to synthesize the first examples of neutral bridging phosphine oxide donor-based supramolecular coordination complexes. The complexes were self-assembled from a fac-Re(CO)3 acceptor, an anionic bridging O donor, and a neutral soft phosphine or hard phosphine oxide donor.

  16. Serum and salivary oxidative analysis in Complex Regional Pain Syndrome.

    Eisenberg, Elon; Shtahl, Shalom; Geller, Rimma; Reznick, Abraham Z; Sharf, Ordi; Ravbinovich, Meirav; Erenreich, Adam; Nagler, Rafael M


    Although both inflammatory and neural mechanisms have been suggested as potential contributors to Complex Regional Pain Syndrome type I (CRPS-I), the pathogenesis of the syndrome is still unclear. Clinical trials have shown that free radical scavengers can reduce signs and symptoms of CRPS-I, indirectly suggesting that free radicals and increased oxidative stress are involved in the pathogenesis of CRPS-I. This study investigated this premise by determining the levels of antioxidants in the serum and saliva of 31 patients with CRPS-I and in a control group of 21 healthy volunteers. Serum lipid peroxidation products (MDA) and all antioxidative parameters analyzed were significantly elevated in CRPS-I patients: median salivary peroxidase and superoxide dismutase (SOD) activity values, uric acid (UA) concentration and total antioxidant status (TAS) values were higher in CRPS-I patients by 150% (p=0.01), 280% (p=0.04), 60% (p=0.0001), and 200% (p=0.0003), respectively, as compared with controls. Similar although not as extensive pattern of oxidative changes were found in the serum: mean serum UA and MDA concentrations and TAS value in the CRPS-I patients were higher by 16% (p=0.04), 25% (p=0.02), and 22% (p=0.05), respectively, than in the controls. Additionally, median salivary albumin concentration and median salivary LDH activities in the patients were 2.5 times (p=0.001) and 3.1 (p=0.004) times higher than in the controls. The accumulated data show that free radicals are involved in the pathophysiology of CRPS-I, which is reflected both in serum and salivary analyses. These data could be used for both diagnostic and therapeutic purposes in CRPS-I patients.

  17. Efectos de fotodegradación propiciados por recubrimientos de TiO2 y TiO2-SiO2 obtenidos por Sol-Gel

    Rodriguez Paez, J. E.


    Full Text Available Photodegradation effect is widely used for water purification this contributes to preservation and protection of environment. Titanium oxide, (TiO2, is a compound that shows up this phenomenon. TiO2 is a semiconductor which may degradate pollutants through of a oxidation process. It permit the treatment of the residual water. It this work we has conformed coatings of TiO2 y TiO2-SiO2, utilized Sol-Gel method and investigated the degradation of the blue Methylene. For this, we introduced these coatings in the blue methylene solution which was illuminated with radiation of λ=365nm to activate its photocatilist properties. The structures of the coatings were characterized using Atomic Force Microscopy (AFM and X-ray Photoelectron Spectroscopy (XPS.El efecto de fotodegradación es ampliamente utilizado para la purificación del agua, acción que contribuye a la conservación y protección del medio ambiente; el óxido de titanio (TiO2 es uno de los semiconductores que pueden degradar contaminantes mediante procesos de oxidación, lo que lo hace apto para el tratamiento de aguas residuales. En este trabajo se conformaron recubrimientos de TiO2 y TiO2-SiO2, por el método Sol-Gel, y se estudio la degradación que experimentaba una solución de azul de metileno al introducirle estos recubrimientos e iluminarlos con una radiación de λ=365nm para activar su propiedad fotocatalítica. Los recubrimientos fueron caracterizados microestructuralmente utilizando Microscopía de Fuerza Atómica (MFA y Espectroscopía de Fotoelectrones de rayos X (XPS. Los resultados obtenidos de los ensayos de fotodegradación indican que los recubrimientos con una cantidad pequeña de silicio presentan un mayor efecto de fotodegradación indicando que el silicio puede generar puntos de anclaje que facilitan las reacciones de fotocatálisis. Por otro lado, la formación de centros activos, constituidos principalmente por carbono, también contribuyeron al desarrollo de estas

  18. Baeyer-Villiger oxidation of ketones with hydrogen peroxide catalyzed by Sn-aniline complex

    Qing Hua Zhang; Shou Feng Wang; Zi Qiang Lei


    Sn-aniline complex was prepared by a simple procedure. Cyclic and acyclic ketones were oxidized into lactones or esters with very high selectivity and yield with 30% hydrogen peroxide in the presence of Sn-aniline complex.

  19. Highly efficient oxidation of alcohols using Oxone(R) as oxidant catalyzed by ruthenium complex under mild reaction conditions

    Zi Qiang Lei; Jian Qiang Wang; Peng Hua Yan


    Aromatic and alkyl alcohols were oxidized to the corresponding aldehydes or ketones at room temperature with high conversion and selectivity using Oxone (2KHSO5·KHSO4·K2SO4) as oxidant catalyzed by ruthenium complex Quin-Ru-Quin (where Quin = 8-hydroxyquinoline). The reaction time is very short and the preparation of complex is simple. 2008 Zi Qiang Lei. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

  20. Local probe investigation of emergent phenomena in complex oxide heterointerfaces

    Huang, Mengchen

    Complex oxide heterointerfaces exhibit rich physics as well as many veiled puzzles. LaAlO3/SrTiO3 (LAO/STO) is one of the prototype of such heterointerfaces. In 2004, Ohtomo and Hwang first reported a conducing interface emerged between perovskite oxide insulators LaAlO3 and SrTiO3. Following this seminal discovery, many emergent phenomena like metal-insulator transition, piezoresponse, superconductivity, magnetism, strong spin-orbit coupling and coexistence of superconductivity and magnetism were reported in the fascinating LAO/STO system. However, the origin of the conducting interface is still the subject of intense debate, and the physics behind these emergent phenomena remains a wild space to be explored. My Ph.D. study focused on the emergent phenomena in LAO/STO by using "local probes" -- nanostructures created by conductive atomic force microscope (c-AFM) lithography and the AFM itself. I used piezoresponse force microscope (PFM) to study the electromechanical response in LAO/STO and developed a high-resolution, non-destructive PFM imaging technique to visualize nanostructures at LAO/STO interface. The results indicate that the PFM signal is related to a carrier density mediated interfacial lattice distortion, and surface adsorbates can affect the PFM signal via coupling to the electrons at the interface. I integrated graphene on LAO/STO, created field-effect devices in graphene/LAO/STO and collaborated with Dr. Giriraj Jnawali to investigate the transport properties. The high quality single layer graphene on LAO/STO exhibited the half-integer quantum Hall effect and room temperature weak antilocalization behavior. I performed transport measurements in (110)-oriented LAO/STO to investigate anisotropic quasi one-dimensional superconductivity in nanowires. Based on the results I proposed a plausible explanation related to the Lifshitz transition and anisotropic band structures of nanowires in (110)-oriented LAO/STO. Co-worked with Dr. Keith Brown, I studied

  1. Growth-induced non-stoichiometry in complex oxide systems

    Breckenfeld, Eric

    Complex perovskite oxides have been studied extensively over the past few decades due to their wide range of functional properties and relative ease of epitaxial synthesis. These two factors have allowed such oxide systems to see a multitude of applications including sensors, memory, thermal management, and energy harvesting. The ability to access so many different functionalities is owed largely to the chemical diversity available to the perovskite unit cell, opening the door for metal-insulator-transitions, ferroelectricity, and superconductivity, to name a few. However, the same chemical diversity that enables so many potential applications also opens the door for a myriad of chemistry-related defects. Separating out the relative contributions of such extrinsic (or defect-driven) effects from the intrinsic material properties is crucial to enabling the use of these materials in high-performance, next-generation devices. In this work, we examine several model systems in order to explore the relationship between the pulsed laser deposition growth process, the film chemistry, and the subsequent effects on the defect landscape and film properties. We show that small changes to the laser fluence can have a marked impact on the chemical composition of the film, leading to cation stoichiometry deviations as large as 10% in SrTiO3, LaAlO3, and NdNiO3 systems. We demonstrate that such chemical deviations can lead to significant changes in the bulk thermal and dielectric properties of SrTiO3 and LaAlO3 films. We have also investigated the interface between SrTiO3 and LaAlO3, which has been studied extensively over the past 8 years due to the supposed presence of a 2-dimensional electron gas (2DEG). Our results indicate that the presence of cation defects in the LaAlO3 has a profound impact on the electronic properties of the 2DEG interface. Finally, we have similarly shown that cation non-stoichiometry can cause the metal-insulator-transition material NdNiO3 to behave

  2. Quantitative Mapping of Reversible Mitochondrial Complex I Cysteine Oxidation in a Parkinson Disease Mouse Model*

    Danielson, Steven R.; Held, Jason M.; Oo, May; Riley, Rebeccah; Gibson, Bradford W.; Andersen, Julie K.


    Differential cysteine oxidation within mitochondrial Complex I has been quantified in an in vivo oxidative stress model of Parkinson disease. We developed a strategy that incorporates rapid and efficient immunoaffinity purification of Complex I followed by differential alkylation and quantitative detection using sensitive mass spectrometry techniques. This method allowed us to quantify the reversible cysteine oxidation status of 34 distinct cysteine residues out of a total 130 present in muri...

  3. Preparation of rare-earth metal complex oxide catalysts for catalytic wet air oxidation

    LI Ning; LI Guangming; YAO Zhenya; ZHAO Jianfu


    Catalytic wet air oxidation(CWAO)is one of the most promising technologies for pollution abatement.Developing catalysts with high activity and stability is crucial for the application of the CWAO process.The Mn/Ce complex oxide catalyrsts for CWAO of high concentration phenol containing wastewater were prepared by coprecipitation.The catalyst preparation conditions were optimized by using an orthogonal layout method and single-factor experimental analysis.The Mn/Ce serial catalysts were characterized by Brunauer-Emmett-Teller(BET)analysis and the metal cation leaching was measured by inductively coupled plasma torch-atomic emission spectrometry(ICP-AES).The results show that the catalysts have high catalytic activities even at a low temperature(80℃)and low oxygen partial pressure(0.5 MPa)in a batch reactor.The metallic ion leaching is comparatively low(Mn<6.577 mg/L and Ce<0.6910 mg/L,respectively)in the CWAO process.The phenol,CODCD and TOC removal efficiencies in the solution exceed 98.5% using the optimal catalyst(named CSP).The new catalyst would have a promising application in CWAO treatment of high concentration organic wastewater.

  4. Interband electronic transitions and phase transformation of multiferroic Bi{sub 1−x}La{sub x}Fe{sub 1−y}Ti{sub y}O{sub 3} ceramics revealed by temperature-dependent spectroscopic ellipsometry

    Xu, L. P.; Jiang, P. P.; Duan, Z. H.; Hu, Z. G., E-mail:; Zhu, Z. Q.; Chu, J. H. [Key Laboratory of Polar Materials and Devices (MOE), Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Zhang, L. L.; Yu, J. [Functional Material Research Laboratory, Tongji University, Shanghai 200092 (China)


    Optical properties and phase transition of Bi{sub 1−x}La{sub x}Fe{sub 1−y}Ti{sub y}O{sub 3} (BLFTO) ceramics with different composition (0.02 ≤ x ≤ 0.10, 0.01 ≤ y ≤ 0.06) have been investigated by spectroscopic ellipsometry (SE) in the temperature range of −70–450 °C. The real part of the complex dielectric function ε{sub 1} increases with the temperature. Meanwhile, the imaginary part ε{sub 2} in the low-energy region decreases with the temperature and has an opposite trend in the high-energy side. Four typical interband transitions (E{sub a} ∼ 2.50 eV, E{sub b} ∼ 2.70 eV, E{sub c} ∼ 3.60 eV, and E{sub d} ∼ 4.25 eV) can be observed from the second derivative of the complex dielectric functions with aid of the standard critical point model. The critical point (CP) transition becomes broadening and shifts to a lower energy side as La and Ti compositions increase. Moreover, the CP transition energies show a red-shift trend with increasing the temperature until 320 °C, due to the lattice thermal expansion and electron-phonon interaction. The typical interband transitions and partial spectral weight present anomalies in the proximity of antiferromagnetic transition owing to the coupling between magnetic and ferroelectric order parameters and spin-lattice coupling for BLFTO multiferroic materials. It was found that the Néel temperature of BLFTO ceramics decreases from 364 to 349 °C with increasing doping composition of La and Ti elements. These phenomena can be attributed to the modification of electronic structure and magnetic order because the differences of electronegativity and ionic radii between Bi and La, Fe and Ti induce the variations on the bond angle and bond length between cations and anions. Moreover, the substitution for magnetic Fe{sup 3+} ions with nonmagnetic Ti{sup 4+} ions can reduce the exchange interaction between adjacent magnetic moments. Therefore, SE technique can be sensitive for

  5. SchiffBase Dinuclear Complex Catalyst for Oxidation of Cyclohexene with Molecular Oxygen

    SHAO; DongXu


    In the past decades, the oxidation of hydrocarbons by transition metal complexes has been studied extensively. The current progress of the research on synthetic quasiporphyrin catalysts has led to the development of several systems that are able to reproduce the hene-enzyme mediated oxygenation and oxidation reactions[1]. In our group[2,51, the mononuclear complexes of amino acid Schiff base have been synthesized and their catalytic oxidation has been studied. In this paper, two dinuclear complexes, such as Salicylidence-β-alanine-Co(II)-Cu(II) and Salicylidence-β-alanine-Co(II)Mn(II), were prepared with amino acid Schiff bases and metal ions. In the presence of these dinuclear complexes, cyclohexene was effectively oxidized under 1 atm of molecular oxygen without any coreductants. The allylic hydroperoxide was obtained as an important product, which suggested a clear allylic pathway of oxidation of cyclohexene.  ……

  6. Scanning probe microscopy investigation of complex-oxide heterostructures

    Bi, Feng

    Advances in the growth of precisely tailored complex-oxide heterostructures have led to new emergent behavior and associated discoveries. One of the most successful examples consists of an ultrathin layer of LaAlO 3 (LAO) deposited on TiO2-terminated SrTiO3 (STO), where a high mobility quasi-two dimensional electron liquid (2DEL) is formed at the interface. Such 2DEL demonstrates a variety of novel properties, including field tunable metal-insulator transition, superconductivity, strong spin-orbit coupling, magnetic and ferroelectric like behavior. Particularly, for 3-unit-cell (3 u.c.) LAO/STO heterostructures, it was demonstrated that a conductive atomic force microscope (c-AFM) tip can be used to "write" or "erase" nanoscale conducting channels at the interface, making LAO/STO a highly flexible platform to fabricate novel nanoelectronics. This thesis is focused on scanning probe microscopy studies of LAO/STO properties. We investigate the mechanism of c-AFM lithography over 3 u.c. LAO/STO in controlled ambient conditions by using a vacuum AFM, and find that the water molecules dissociated on the LAO surface play a critical role during the c-AFM lithography process. We also perform electro-mechanical response measurements over top-gated LAO/STO devices. Simultaneous piezoresponse force microscopy (PFM) and capacitance measurements reveal a correlation between LAO lattice distortion and interfacial carrier density, which suggests that PFM could not only serve as a powerful tool to map the carrier density at the interface but also provide insight into previously reported frequency dependence of capacitance enhancement of top-gated LAO/STO structures. To study magnetism at the LAO/STO interface, magnetic force microscopy (MFM) and magnetoelectric force microscopy (MeFM) are carried out to search for magnetic signatures that depend on the carrier density at the interface. Results demonstrate an electronicallycontrolled ferromagnetic phase on top-gated LAO


    HUANG Meiyu; HUANG Li; ZHENG Qingyao; WANG Dianxun; JIANG Yingyan


    Two kinds of polymer-platinum complexes: silica-supported poly-γ-diphenylphosphinopropyl-siloxane-platinum complex and silica-supported polyphenylsilazane-platinum complex, have been found very active and selective in catalyzation of oxidation of methanol to formaldehyde at room temperature and under an atmospheric oxygen pressure. Their catalytic activities are greatly affected by P or N/Pt gram atomic ratio.

  8. Complexation of Nitrous Oxide by Frustrated Lewis Pairs

    Otten, Edwin; Neu, Rebecca C.; Stephan, Douglas W.


    Frustrated Lewis pairs comprised of a basic yet sterically encumbered phosphine with boron Lewis acids bind nitrous oxide to give intact PNNOB linkages. The synthesis, structure, and bonding of these species are described.

  9. Alkane oxidation with porphyrins and metal complexes thereof having haloalkyl side chains

    Wijesekera, Tilak; Lyons, James E.; Ellis, Jr., Paul E.; Bhinde, Manoj V.


    Transition metal complexes of meso-haloalkylporphyrins, wherein the haloalkyl groups contain 2 to 8 carbon atoms have been found to be highly effective catalysts for oxidation of alkanes and for the decomposition of hydroperoxides.

  10. Ruthenium or osmium complexes and their uses as catalysts for water oxidation

    Corbea, Javier Jesus Concepcion; Chen, Zuofeng; Jurss, Jonah Wesley; Templeton, Joseph L.; Hoertz, Paul; Meyer, Thomas J.


    The present invention provides ruthenium or osmium complexes and their uses as a catalyst for catalytic water oxidation. Another aspect of the invention provides an electrode and photo-electrochemical cells for electrolysis of water molecules.

  11. Ruthenium or osmium complexes and their uses as catalysts for water oxidation

    Corbea, Javier Jesus Concepcion; Chen, Zoufeng; Jurss, Jonah Wesley; Templeton, Joseph L.; Hoertz, Paul; Meyer, Thomas J.


    The present invention provides ruthenium or osmium complexes and their uses as a catalyst for catalytic water oxidation. Another aspect of the invention provides an electrode and photo-electrochemical cells for electrolysis of water molecules.

  12. Eu(Ⅲ) complexes involving 1,3,5-triazine diphosphine oxides

    O.Pietraszkiewicz; M.Pietraszkiewicz; J.Karpiuk; M.Jesie(n)


    The 1,3,5-triazine diphosphine oxide ligands with donor-acceptor properties formed strong complexes with europium(Ⅲ) ion in acetonitrile.Spectrophotometric titrations and mass spectra indicated that two ligands coordinated to one europium ion.The stability constants varied from 11.64 to 14.60 (log β).Binary complexes exhibited rather weak luminescence in solution.1,3,5-triazine diphosphine oxides engaged as co-ligands in Eu(Ⅲ) (2-thenoyltrifluoroacetonate)3 complex contributed to the overall photoluminescence and allowed for excitation with longer wavelengths than the parent complex.

  13. Homogeneous Photocatalytic Water Oxidation with a Dinuclear Co(III)-Pyridylmethylamine Complex.

    Ishizuka, Tomoya; Watanabe, Atsuko; Kotani, Hiroaki; Hong, Dachao; Satonaka, Kenta; Wada, Tohru; Shiota, Yoshihito; Yoshizawa, Kazunari; Ohara, Kazuaki; Yamaguchi, Kentaro; Kato, Satoshi; Fukuzumi, Shunichi; Kojima, Takahiko


    A bis-hydroxo-bridged dinuclear Co(III)-pyridylmethylamine complex (1) was synthesized and the crystal structure was determined by X-ray crystallography. Complex 1 acts as a homogeneous catalyst for visible-light-driven water oxidation by persulfate (S2O8(2-)) as an oxidant with [Ru(II)(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer affording a high quantum yield (44%) with a large turnover number (TON = 742) for O2 formation without forming catalytically active Co-oxide (CoO(x)) nanoparticles. In the water-oxidation process, complex 1 undergoes proton-coupled electron-transfer (PCET) oxidation as a rate-determining step to form a putative dinuclear bis-μ-oxyl Co(III) complex (2), which has been suggested by DFT calculations. Catalytic water oxidation by 1 using [Ru(III)(bpy)3](3+) as an oxidant in a H2(16)O and H2(18)O mixture was examined to reveal an intramolecular O-O bond formation in the two-electron-oxidized bis-μ-oxyl intermediate, prior to the O2 evolution.

  14. Pneumococcal Gene Complex Involved in Resistance to Extracellular Oxidative Stress

    Andisi, Vahid Farshchi; Hinojosa, Cecilia A.; de Jong, Anne; Kuipers, Oscar P.; Orihuela, Carlos J.; Bijlsma, Jetta J. E.; Weiser, J.N.


    Streptococcus pneumoniae is a Gram-positive bacterium which is a member of the normal human nasopharyngeal flora but can also cause serious disease such as pneumonia, bacteremia, and meningitis. Throughout its life cycle, S. pneumoniae is exposed to significant oxidative stress derived from endogeno

  15. Oxidative effect of several intravenous iron complexes in the rat.

    Bailie, George R; Schuler, Catherine; Leggett, Robert E; Li, Hsin; Li, Hsin-Dat; Patadia, Hiten; Levin, Robert


    The objective of this study was to compare the oxidative stress induced in rat internal organs by the administration of the following clinically used intravenous (IV) iron (Fe) containing compounds: iron sucrose (IS), iron dextran (ID), ferric carboxymaltose and ferumoxytol. Groups of six adult rats received 1 mg/kg of each compound weekly for 5 doses. Seven days following the last dose, animals were euthanized and tissue samples of heart, lung, liver, and kidney were obtained, washed in warmed saline and frozen under liquid nitrogen and stored at -80 °C for analysis for nitrotyrosine (NT) and dinitro phenyl (DNP) as markers of oxidative stress. All tissues showed a similar pattern of oxidative stress. All Fe products stimulated an increase in the tissue concentration of both NT and DNP. In general, DNP was stimulated significantly less than NT except for IS. DNP was stimulated to an equal degree except for ID where NT was significantly higher than the NT concentrations in all other Fe compounds. ID produced over 10-fold the concentration of NT than any other Fe. IV Fe compounds present a risk of oxidative stress to a variety of internal organs. However, we found that IS was the least damaging and ID was the worst.

  16. [Noncovalent complexes between alpha-chymotrypsin and block copolymers from ethylene and propylene oxides].

    Topchieva, I N; Snitko, Ia E; Efremova, N V; Sorokina, E M


    The ability of alpha-chymotrypsin to form complexes with amphiphilic block copolymer of ethylene oxide and propylene oxide upon heating up to 44-60 degrees C has been demonstrated for the first time. Depending on temperature and the initial component ratio, some complexes were obtained which varied in both composition and enzymatic activity. With a rise in the complexation temperature, the polymer content in the complex increased, while the enzymatic activity of the complex decreases. The complexes are very stable in water, but dissociate in 8 M urea and are characterized by enhanced thermal stability as compared with the original enzyme. It is assumed that both hydrophobic interactions and hydrogen bonds between the components are involved in the complex formation.

  17. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    Kourov, N. I., E-mail:; Marchenkov, V. V.; Belozerova, K. A. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Weber, H. W. [Atominstitut, Vienna University of Technology (Austria)


    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  18. Synthesis, characterization, and antibacterial activities of a novel nanohydroxyapatite/zinc oxide complex.

    Zhou, G.; Li, Yubao; Xiao, W.; Zhang, L.; Zuo, Y.; Xue, J.; Jansen, J.A.


    Nanohydroxyapatite (n-HA)/zinc oxide (ZnO) complex was synthesized by a direct precipitation method, and the antibacterial capability and antibacterial mechanism of this complex were investigated in this article. Transmission electron microscope (TEM), Fourier transform infrared, X-ray photoelectron

  19. Connecting mononuclear dysprosium single-molecule magnets to form dinuclear complexes via in situ ligand oxidation.

    Yutronkie, Nathan J; Kühne, Irina A; Korobkov, Ilia; Brusso, Jaclyn L; Murugesu, Muralee


    A Dy2 complex, exhibiting SMM behaviour, and its Y analogue were prepared via in situ oxidation of Py2TTA, a pincer type ligand, followed by dimerisation. This unique metal complexation and subsequent dimerization were followed by solution NMR studies.

  20. Water exchange in manganese-based water-oxidizing catalysts in photosynthetic systems: from the water-oxidizing complex in photosystem II to nano-sized manganese oxides.

    Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Eaton-Rye, Julian J; Tomo, Tatsuya; Nishihara, Hiroshi; Satoh, Kimiyuki; Carpentier, Robert; Shen, Jian-Ren; Allakhverdiev, Suleyman I


    The water-oxidizing complex (WOC), also known as the oxygen-evolving complex (OEC), of photosystem II in oxygenic photosynthetic organisms efficiently catalyzes water oxidation. It is, therefore, responsible for the presence of oxygen in the Earth's atmosphere. The WOC is a manganese-calcium (Mn₄CaO₅(H₂O)₄) cluster housed in a protein complex. In this review, we focus on water exchange chemistry of metal hydrates and discuss the mechanisms and factors affecting this chemical process. Further, water exchange rates for both the biological cofactor and synthetic manganese water splitting are discussed. The importance of fully unveiling the water exchange mechanism to understand the chemistry of water oxidation is also emphasized here. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.

  1. Electrochemical Instability of Phosphonate-Derivatized, Ruthenium(III) Polypyridyl Complexes on Metal Oxide Surfaces.

    Hyde, Jacob T; Hanson, Kenneth; Vannucci, Aaron K; Lapides, Alexander M; Alibabaei, Leila; Norris, Michael R; Meyer, Thomas J; Harrison, Daniel P


    The oxidative stability of the molecular components of dye-sensitized photoelectrosynthesis cells for solar water splitting remains to be explored systematically. We report here the results of an electrochemical study on the oxidative stability of ruthenium(II) polypyridyl complexes surface-bound to fluorine-doped tin oxide electrodes in acidic solutions and, to a lesser extent, as a function of pH and solvent with electrochemical monitoring. Desorption occurs for the Ru(II) forms of the surface-bound complexes with oxidation to Ru(III) enhancing both desorption and decomposition. Based on the results of long-term potential hold experiments with cyclic voltammetry monitoring, electrochemical oxidation to Ru(III) results in slow decomposition of the complex by 2,2'-bipyridine ligand loss and aquation and/or anation. A similar pattern of ligand loss was also observed for a known chromophore-catalyst assembly for both electrochemical water oxidation and photoelectrochemical water splitting. Our results are significant in identifying the importance of enhancing chromophore stability, or at least transient stability, in oxidized forms in order to achieve stable performance in aqueous environments in photoelectrochemical devices.

  2. Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers for strain tuning of infinite-layer Sr{sub 1−x}La{sub x}CuO{sub 2} thin films

    Sakuma, Keita, E-mail:; Ito, Masataka; He, Yilun; Hajiri, Tetsuya; Ueda, Kenji; Asano, Hidefumi


    We report on the precise tuning of lattice strain in an infinite-layer electron-doped high temperature superconductor Sr{sub 1−x}La{sub x}CuO{sub 2} (SLCO; a{sub SLCO} = 0.3949 nm for x = 0.1), which is a perovskite-related oxide, using perovskite BaTiO{sub 3}–SrTiO{sub 3} (BSTO; Ba{sub y}Sr{sub 1−y}TiO{sub 3}) buffer layers. The BSTO buffer layers formed on (001) (La{sub 0.18}Sr{sub 0.82})(Al{sub 0.59}Ta{sub 0.41})O{sub 3} substrates by magnetron sputtering were fully relaxed with high crystalline quality due to high oxygen partial pressure deposition and post annealing at 950 °C. The lattice constants of the BSTO buffer layers could be controlled in the range of 0.3926–0.3973 nm by changing the Ba content (y = 0.2–0.7). These BSTO buffer layers allow coherent growth of SLCO thin films, and a clear dependence of the superconducting transition temperature on the lattice strain was observed. The fabrication of these BSTO/superconductor heterostructures may provide novel devices composed of functional perovskite thin films, in addition to a general approach for the precise control of lattice strain in functional perovskite thin films. - Highlights: • Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers were developed for the strain tuning of perovskite-related oxides. • Strain effect in Sr{sub 1−x}La{sub x}CuO{sub 2} was investigated by using Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers. • Ba{sub y}Sr{sub 1−y}TiO{sub 3} buffer layers can be used to tune the strain in other perovskite oxides.

  3. Oxygen atom transfer to a half-sandwich iridium complex: clean oxidation yielding a molecular product.

    Turlington, Christopher R; White, Peter S; Brookhart, Maurice; Templeton, Joseph L


    The oxidation of [Ir(Cp*)(phpy)(NCAr(F))][B(Ar(F))4] (1; Cp* = η(5)-pentamethylcyclopentadienyl, phpy = 2-phenylene-κC(1')-pyridine-κN, NCAr(F) = 3,5-bis(trifluoromethyl)benzonitrile, B(Ar(F))4 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) with the oxygen atom transfer (OAT) reagent 2-tert-butylsulfonyliodosobenzene (sPhIO) yielded a single, molecular product at -40 °C. New Ir(Cp*) complexes with bidentate ligands derived by oxidation of phpy were synthesized to model possible products resulting from oxygen atom insertion into the iridium-carbon and/or iridium-nitrogen bonds of phpy. These new ligands were either cleaved from iridium by water or formed unreactive, phenoxide-bridged iridium dimers. The reactivity of these molecules suggested possible decomposition pathways of Ir(Cp*)-based water oxidation catalysts with bidentate ligands that are susceptible to oxidation. Monitoring the [Ir(Cp*)(phpy)(NCAr(F))](+) oxidation reaction by low-temperature NMR techniques revealed that the reaction involved two separate OAT events. An intermediate was detected, synthesized independently with trapping ligands, and characterized. The first oxidation step involves direct attack of the sPhIO oxidant on the carbon of the coordinated nitrile ligand. Oxygen atom transfer to carbon, followed by insertion into the iridium-carbon bond of phpy, formed a coordinated organic amide. A second oxygen atom transfer generated an unidentified iridium species (the "oxidized complex"). In the presence of triphenylphosphine, the "oxidized complex" proved capable of transferring one oxygen atom to phosphine, generating phosphine oxide and forming an Ir-PPh3 adduct in 92% yield. The final Ir-PPh3 product was fully characterized.

  4. Osmium(ii) complexes for light-driven aerobic oxidation of amines to imines.

    Li, Yong-Hui; Liu, Xiao-Le; Yu, Zhen-Tao; Li, Zhao-Sheng; Yan, Shi-Cheng; Chen, Guang-Hui; Zou, Zhi-Gang


    Herein, we describe the synthesis and characterization of three Os(ii) complexes (i.e., [Os(fptz)2(PPhMe2)2] (1, fptzH = 3-trifluoromethyl-5-pyridyl-1,2,4-triazole), [Os(fptz)2(CO)(L1)] (2, L1 = PPh3; 3, L1 = pyridine)) that have been successfully utilized as good photocatalysts to promote aerobic oxidative coupling of amines to imines with molecular oxygen in air as a green oxidant. Complex 1 is the most effective catalyst for the oxidative coupling of benzylamine with molecular O2 (air) as the oxidant because of the complex's strong absorption of visible light and long-lived triplet state. The application of a low catalyst loading (0.06 mol%) of complex 1 to the oxidative coupling of a wide range of amines affords the corresponding imines efficiently and selectively in most cases. The reaction mechanism was investigated via relevant control and quenching experiments. The results indicated that the reaction occurs via an active (1)O2-involved pathway. The (1)O2-generating ability of complex 1 as a photosensitizer was evaluated using 9,10-dimethylanthracene (DMA) as a chemical trap for (1)O2.


    HAO Chengjun; ZhAO Ganqing


    Polymer-bound Schiff-base ligand (PS-Sal-Cys) was prepared from the polystyrene-bound salicylaldehyde and L-cysteine, its complex (PS-Sal-Cys-Mn) was also synthesized. The polymer ligand and its complex were characterized by infrared spectra (IR), small area X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-atomic emission spectro (ICP-AES). In the presence of complex, cyclohexane can be effectively oxidized by molecular oxygen without a reductant. The major products of the reaction are 2-cyclohexen-1-ol, 2-cyclohexen-1-one, and 2-cyclohexen-1-hydroperoxide, which is different from the typical oxidation of cyclohexene. The mechanism of cyclohexene oxidation is also discussed.

  6. Measuring the complex behavior of the SO2 oxidation reaction

    Muhammad Shahzad


    Full Text Available The two step reversible chemical reaction involving five chemical species is investigated. The quasi equilibrium manifold (QEM and spectral quasi equilibrium manifold (SQEM are used for initial approximation to simplify the mechanisms, which we want to utilize in order to investigate the behavior of the desired species. They show a meaningful picture, but for maximum clarity, the investigation method of invariant grid (MIG is employed. These methods simplify the complex chemical kinetics and deduce low dimensional manifold (LDM from the high dimensional mechanism. The coverage of the species near equilibrium point is investigated and then we shall discuss moving along the equilibrium of ODEs. The steady state behavior is observed and the Lyapunov function is utilized to study the stability of ODEs. Graphical results are used to describe the physical aspects of measurements.

  7. Ligand exchange and redox processes in iridium triazolylidene complexes relevant to catalytic water oxidation.

    Petronilho, Ana; Llobet, Antoni; Albrecht, Martin


    Iridium(III) complexes containing a bidentate spectator ligand have emerged as powerful catalyst precursors for water oxidation. Here we investigate the initial steps of the transformation at the iridium center when using complex [IrCp*(pyr-trz)Cl] 1 (Cp* = pentamethylcyclopentadienyl, pyr-trz = 4-(2-pyridyl)-1,2,3-triazol-5-ylidene), a potent water oxidation catalyst precursor. Ligand exchange with water is facile and is reversed in the presence of chloride ions, while MeCN substitution is effective only from the corresponding aqua complex. A pKa of 8.3 for the aqua complex was determined, which is in agreement with strong electron donation from the triazolylidene ligand that is comparable to aryl anions. Evaluation of the pH-dependent oxidation process in aqueous media reveals two regimes (pH 4-8.5 and above pH 10.5) where proton-coupled electron transfer processes occur. These investigations will help to further optimize water oxidation catalysts and indicate that MeCN as a cosolvent has adverse effects for initiating water coordination in the oxidation process.

  8. Multiporphyrin coordination arrays based on complexation of magnesium(II) porphyrins with porphyrinylphosphine oxides.

    Atefi, Farzad; McMurtrie, John C; Arnold, Dennis P


    Di- and triporphyrin arrays consisting of 5,15-diphenylporphyrinatomagnesium(II) (MgDPP) coordinated to free-base and Ni(II) porphyrinyl mono- and bis-phosphine oxides, as well as the self-coordinating diphenyl[10,20-diphenylporphyrinatomagnesium(II)-5-yl]phosphine oxide [MgDPP(Ph(2)PO)], were synthesised in excellent yields and characterised by various spectroscopic techniques. Phosphine oxides stabilise Mg(II) coordination to porphyrins and the resulting complexes have convenient solubilities, while the Ni(II) complexes exhibit interesting intramolecular fluorescence quenching behaviour. The binding constant of MgDPP to triphenylphosphine oxide (5.3 +/- 0.1 x 10(5) M(-1)) and the very high self-association constant of [MgDPP(Ph(2)PO)] (5.5 +/- 0.5 x 10(8) M(-1)) demonstrate the strong affinity of phosphine oxides towards Mg(II) porphyrins. These complexes are the first strongly bound synthetic Mg(II) multiporphyrin complexes and could potentially mimic the "special pair" in the photosynthetic reaction centre.

  9. Microwave irradiation assisted, one pot synthesis of simple and complex metal oxide nanoparticles: a general approach

    Brahma, Sanjaya; Liu, Chuan-Pu; Shivashankar, S. A.


    We demonstrate a standard approach for the growth of binary/ternary metal oxide nanostructures within 5 min at a low temperature (Nanoparticles of some functionally advanced binary/ternary metal oxides (MnO2, Fe2O3, NiO, CdO, Ga2O3, Gd2O3, ZnFe2O4, ZnMn2O4) are synthesized and the structure/microstructure is analyzed to ensure the phase and crystallinity. This synthesis procedure can be extended to the large scale production of many other simple and complex metal oxides.

  10. Oxidation of aromatic alcohols on zeolite-encapsulated copper amino acid complexes

    Ernst, S.; Teixeira Florencio, J.M. [Kaiserslautern Univ. (Germany). Dept. of Chemistry, Chemical Technology


    Copper complexes of the amino acids histidine, arginine and lysine have been introduced into the supercages of zeolite Y and, for the first time, into the large intracrystalline cavities of zeolites EMT and MCM-22. The resulting host/guest compounds are characterized by X-ray powder diffraction, UV/VIS-spectroscopy in the diffuse reflectance mode and by catalytic tests in the liquid-phase oxidation of aromatic alcohols (viz. benzyl alcohol, 2- and 3-methylbenzyl alcohol and 2,5-dimethylbenzyl alcohol) with tertiary-butylhydroperoxide as oxidant. It was observed that intracrystalline copper-amino acid complexes possess remarkable catalytic activity, yielding the corresponding aromatic aldehydes and acids. (orig.)

  11. Direct patterning of complex oxides by pulsed laser deposition through stencils

    Riele, Paul te; Janssens, Arjen; Rijnders, Guus; Blank, Dave H A [University of Twente, Inorganic Material Science, Faculty of Science and Technology MESA Institute for Nanotechnology, PO Box 217, 7500 AE Enschede (Netherlands)


    The possibilities to grow isolated structures of complex oxides by pulsed laser deposition through stencils were investigated. A stencil consisting of a SiN membrane with apertures of several hundred nanometers embedded in a Si chip is placed in front of a heated substrate (up to 750 degrees Celsius). Deposition through these apertures results in resistless, direct patterning by local deposition of complex oxides like ferroelectric Lead Zirconate Titanate. The created isolated structures were analyzed by AFM imaging. Under-deposition, in this work called broadening, is inevitable during stencil deposition and is depending on deposition parameters, especially pressure. Different causes of broadening are mapped and discussed.

  12. Water oxidation catalysis with nonheme iron complexes under acidic and basic conditions: homogeneous or heterogeneous?

    Hong, Dachao; Mandal, Sukanta; Yamada, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Llobet, Antoni; Fukuzumi, Shunichi


    Thermal water oxidation by cerium(IV) ammonium nitrate (CAN) was catalyzed by nonheme iron complexes, such as Fe(BQEN)(OTf)2 (1) and Fe(BQCN)(OTf)2 (2) (BQEN = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine, BQCN = N,N'-dimethyl-N,N'-bis(8-quinolyl)cyclohexanediamine, OTf = CF3SO3(-)) in a nonbuffered aqueous solution; turnover numbers of 80 ± 10 and 20 ± 5 were obtained in the O2 evolution reaction by 1 and 2, respectively. The ligand dissociation of the iron complexes was observed under acidic conditions, and the dissociated ligands were oxidized by CAN to yield CO2. We also observed that 1 was converted to an iron(IV)-oxo complex during the water oxidation in competition with the ligand oxidation. In addition, oxygen exchange between the iron(IV)-oxo complex and H2(18)O was found to occur at a much faster rate than the oxygen evolution. These results indicate that the iron complexes act as the true homogeneous catalyst for water oxidation by CAN at low pHs. In contrast, light-driven water oxidation using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) as a photosensitizer and S2O8(2-) as a sacrificial electron acceptor was catalyzed by iron hydroxide nanoparticles derived from the iron complexes under basic conditions as the result of the ligand dissociation. In a buffer solution (initial pH 9.0) formation of the iron hydroxide nanoparticles with a size of around 100 nm at the end of the reaction was monitored by dynamic light scattering (DLS) in situ and characterized by X-ray photoelectron spectra (XPS) and transmission electron microscope (TEM) measurements. We thus conclude that the water oxidation by CAN was catalyzed by short-lived homogeneous iron complexes under acidic conditions, whereas iron hydroxide nanoparticles derived from iron complexes act as a heterogeneous catalyst in the light-driven water oxidation reaction under basic conditions.

  13. Morphological characteristics, oxidative stability and enzymic hydrolysis of amylose-fatty acid complexes.

    Marinopoulou, Anna; Papastergiadis, Efthimios; Raphaelides, Stylianos N; Kontominas, Michael G


    Complexes of amylose with fatty acids varying in carbon chain length and degree of unsaturation were prepared at 30, 50 or 70°C by dissolving amylose in 0.1N KOH and mixing with fatty acid potassium soap solution. The complexes were obtained in solid form as precipitates after neutralization. SEM microscopy revealed that the morphology of the complexes was that of ordered lamellae separated from amorphous regions whereas confocal laser scanning microscopy showed images of the topography of the guest molecules in the complex matrix. FTIR spectroscopy revealed that the absorption peak attributed to carbonyl group of free fatty acid was shifted when the fatty acid was in the form of amylose complex. Thermo-gravimetry showed that the unsaturated fatty acids were effectively protected from oxidation when they were complexed with amylose whereas enzymic hydrolysis experiments showed that the guest molecules were quantitatively released from the amylose complexes.

  14. Complex Internal Bias Fields in Ferroelectric Hafnium Oxide.

    Schenk, Tony; Hoffmann, Michael; Ocker, Johannes; Pešić, Milan; Mikolajick, Thomas; Schroeder, Uwe


    For the rather new hafnia- and zirconia-based ferroelectrics, a lot of questions are still unsettled. Among them is the electric field cycling behavior consisting of (1) wake-up, (2) fatigue, and (3) the recently discovered subcycling-induced split-up/merging effect of transient current peaks in a hysteresis measurement. In the present work, first-order reversal curves (FORCs) are applied to study the evolution of the switching and backswitching field distribution within the frame of the Preisach model for three different phenomena: (1) The pristine film contains two oppositely biased regions. These internal bias fields vanish during the wake-up cycling. (2) Fatigue as a decrease in the number of switchable domains is accompanied by a slight increase in the mean absolute value of the switching field. (3) The split-up effect is shown to also be related to local bias fields in a complex situation resulting from both the field cycling treatment and the measurement procedure. Moreover, the role of the wake-up phenomenon is discussed with respect to optimizing low-voltage operation conditions of ferroelectric memories toward reasonably high and stable remanent polarization and highest possible endurance.

  15. Oxidatively Robust Monophenolate-Copper(II) Complexes as Potential Models of Galactose Oxidation

    Koten, G. van; Klein Gebbink, R.J.M.; Watanabe, M.; Pratt, R.C.; Stack, D.P.


    Cupric complexes of a novel phenanthroline-phenolate ligand have strongly distorted coordination geometries and electrochemical properties conducive to modeling the spectroscopy and reactivity of the enzyme galactose oxidase.

  16. Polypyridyl transition metal complexes with application in water oxidation catalysis and dye-sensitised solar cells

    Rudd, Jennifer A.


    This thesis contains complementary synthetic and computational studies of transition metal complexes with polypyridyl ligands for use either as water oxidation catalysts or for application in dye-sensitised solar cells (DSSCs). Chapter 1 introduces the reasons for researching water splitting catalysts and describes a number of current techniques used to do so; from photoelectrochemical cells to the use of transition metal polypyridyl complexes. It also introduces three commercially avail...

  17. Developing mononuclear copper-active-oxygen complexes relevant to reactive intermediates of biological oxidation reactions.

    Itoh, Shinobu


    Active-oxygen species generated on a copper complex play vital roles in several biological and chemical oxidation reactions. Recent attention has been focused on the reactive intermediates generated at the mononuclear copper active sites of copper monooxygenases such as dopamine β-monooxygenase (DβM), tyramine β-monooxygenase (TβM), peptidylglycine-α-hydroxylating monooxygenase (PHM), and polysaccharide monooxygenases (PMO). In a simple model system, reaction of O2 and a reduced copper(I) complex affords a mononuclear copper(II)-superoxide complex or a copper(III)-peroxide complex, and subsequent H(•) or e(-)/H(+) transfer, which gives a copper(II)-hydroperoxide complex. A more reactive species such as a copper(II)-oxyl radical type species could be generated via O-O bond cleavage of the peroxide complex. However, little had been explored about the chemical properties and reactivity of the mononuclear copper-active-oxygen complexes due to the lack of appropriate model compounds. Thus, a great deal of effort has recently been made to develop efficient ligands that can stabilize such reactive active-oxygen complexes in synthetic modeling studies. In this Account, I describe our recent achievements of the development of a mononuclear copper(II)-(end-on)superoxide complex using a simple tridentate ligand consisting of an eight-membered cyclic diamine with a pyridylethyl donor group. The superoxide complex exhibits a similar structure (four-coordinate tetrahedral geometry) and reactivity (aliphatic hydroxylation) to those of a proposed reactive intermediate of copper monooxygenases. Systematic studies based on the crystal structures of copper(I) and copper(II) complexes of the related tridentate supporting ligands have indicated that the rigid eight-membered cyclic diamine framework is crucial for controlling the geometry and the redox potential, which are prerequisites for the generation of such a unique mononuclear copper(II)-(end-on)superoxide complex

  18. Thiol-based antioxidants elicit mitochondrial oxidation via respiratory complex III

    Beaudoin, Jessica N.; Ponnuraj, Nagendraprabhu; DiLiberto, Stephen J.; Hanafin, William P.; Kenis, Paul J. A.; Gaskins, H. Rex


    Excessive oxidation is widely accepted as a precursor to deleterious cellular function. On the other hand, an awareness of the role of reductive stress as a similar pathological insult is emerging. Here we report early dynamic changes in compartmentalized glutathione (GSH) redox potentials in living cells in response to exogenously supplied thiol-based antioxidants. Noninvasive monitoring of intracellular thiol-disulfide exchange via a genetically encoded biosensor targeted to cytosol and mitochondria revealed unexpectedly rapid oxidation of the mitochondrial matrix in response to GSH ethyl ester or N-acetyl-l-cysteine. Oxidation of the probe occurred within seconds in a concentration-dependent manner and was attenuated with the membrane-permeable ROS scavenger tiron. In contrast, the cytosolic sensor did not respond to similar treatments. Surprisingly, the immediate mitochondrial oxidation was not abrogated by depolarization of mitochondrial membrane potential or inhibition of mitochondrial GSH uptake. After detection of elevated levels of mitochondrial ROS, we systematically inhibited multisubunit protein complexes of the mitochondrial respiratory chain and determined that respiratory complex III is a downstream target of thiol-based compounds. Disabling complex III with myxothiazol completely blocked matrix oxidation induced with GSH ethyl ester or N-acetyl-l-cysteine. Our findings provide new evidence of a functional link between exogenous thiol-containing antioxidants and mitochondrial respiration. PMID:25994788

  19. Half-sandwich iridium complexes for homogeneous water-oxidation catalysis.

    Blakemore, James D; Schley, Nathan D; Balcells, David; Hull, Jonathan F; Olack, Gerard W; Incarvito, Christopher D; Eisenstein, Odile; Brudvig, Gary W; Crabtree, Robert H


    Iridium half-sandwich complexes of the types Cp*Ir(N-C)X, [Cp*Ir(N-N)X]X, and [CpIr(N-N)X]X are catalyst precursors for the homogeneous oxidation of water to dioxygen. Kinetic studies with cerium(IV) ammonium nitrate as primary oxidant show that oxygen evolution is rapid and continues over many hours. In addition, [Cp*Ir(H(2)O)(3)]SO(4) and [(Cp*Ir)(2)(μ-OH)(3)]OH can show even higher turnover frequencies (up to 20 min(-1) at pH 0.89). Aqueous electrochemical studies on the cationic complexes having chelate ligands show catalytic oxidation at pH > 7; conversely, at low pH, there are no oxidation waves up to 1.5 V vs NHE for the complexes. H(2)(18)O isotope incorporation studies demonstrate that water is the source of oxygen atoms during cerium(IV)-driven catalysis. DFT calculations and kinetic experiments, including kinetic-isotope-effect studies, suggest a mechanism for homogeneous iridium-catalyzed water oxidation and contribute to the determination of the rate-determining step. The kinetic experiments also help distinguish the active homogeneous catalyst from heterogeneous nanoparticulate iridium dioxide.

  20. Sulfide and sulfoxide oxidations by mono- and diperoxo complexes of molybdenum. A density functional study.

    Sensato, Fabrício R; Custodio, Rogério; Longo, E; Safont, Vicent S; Andres, Juan


    The molecular mechanism for the oxidation of sulfides to sulfoxides and subsequent oxidation to sulfones by diperoxo, MoO(O(2))(2)(OPH(3)) (I), and monoperoxo, MoO(2)(O(2))(OPH(3)) (II), complexes of molybdenum was studied using density functional calculations at the b3lyp level and the transition state theory. Complexes I and II were both found to be active species. Sulfide oxidation by I or II shows similar activation free energy values of 18.5 and 20.9 kcal/mol, respectively, whereas sulfoxides are oxidized by I (deltaG = 20.6 kcal/mol) rather than by II (deltaG = 30.3 kcal/mol). Calculated kinetic and thermodynamic parameters account for the spontaneous overoxidation of sulfides to sulfones as has been experimentally observed. The charge decomposition analysis (CDA) of the calculated transition structures of sulfide and sulfoxide oxidations revealed that I and II are stronger electrophilic oxidants toward sulfides than they are toward sulfoxides.

  1. Direct patterning of complex oxides by pulsed laser deposition through stencils

    Riele, te Paul; Janssens, Arjen; Rijnders, Guus; Blank, Dave H.A.


    The possibilities to grow isolated structures of complex oxides by pulsed laser deposition through stencils were investigated. A stencil consisting of a SiN membrane with apertures of several hundred nanometers embedded in a Si chip is placed in front of a heated substrate (up to 750 degrees Celsius

  2. Tetradentate Schiff base ligands and their complexes: synthesis, structural characterization, thermal, electrochemical and alkane oxidation.

    Ceyhan, Gökhan; Köse, Muhammet; McKee, Vickie; Uruş, Serhan; Gölcü, Ayşegül; Tümer, Mehmet


    Three Schiff base ligands (H(2)L(1)-H(2)L(3)) with N(2)O(2) donor sites were synthesized by condensation of 1,5-diaminonapthalene with benzaldehyde derivatives. A series of Cu(II), Co(II), Ni(II), Mn(II) and Cr(III) complexes were prepared and characterized by spectroscopic and analytical methods. Thermal, electrochemical and alkane oxidation reactions of the ligands and their metal complexes were investigated. Extensive application of 1D ((1)H, (13)C NMR) and 2D (COSY, HETCOR, HMBC and TOSCY) NMR techniques were used to characterize the structures of the ligands and establish the (1)H and (13)C resonance assignments of the three ligands. Ligands H(2)L(1) and H(2)L(3) were obtained as single crystals from THF solution and characterized by X-ray diffraction. Both molecules are centrosymmetric and asymmetric unit contains one half of the molecule. Catalytic alkane oxidation reactions with the transition metal complexes investigated using cyclohexane and cyclooctane as substrates. The Cu(II) and Cr(III) complexes showed good catalytic activity in the oxidation of cyclohexane and cyclooctane to desired oxidized products. Electrochemical and thermal properties of the compounds were also investigated.

  3. Structure and spectroscopy of uranyl and thorium complexes with substituted phosphine oxide ligands

    Breshears, Andrew T.; Barnes, Charles L.; Wagle, Durgesh V.; Baker, Gary A.; Walensky, Justin R. [Missouri Univ., Columbia, MO (United States). Dept. of Chemistry; Takase, Michael K. [California Institute of Technology, Pasadena, CA (United States). Beckman Institute


    Phosphine oxide ligands are important in the chemistry of the nuclear fuel cycle. We have synthesized and characterized a series of phosphine oxide ligands with polycyclic aromatic hydrocarbon (PAH) groups to enhance the spectroscopic features of uranyl, UO{sub 2}{sup 2+}, and to make detection more efficient. Complexation of OPPh{sub 2}R, R = C{sub 10}H{sub 7} (naphthyl); C{sub 14}H{sub 9} (phenanthrenyl); C{sub 14}H{sub 9} (anthracenyl); and C{sub 16}H{sub 9} (pyrenyl), to UO{sub 2}(NO{sub 3}){sub 2} afforded the eight-coordinate complexes, UO{sub 2}(NO{sub 3}){sub 2}(OPPh{sub 2}R){sub 2}. An eleven-coordinate complex, Th(NO{sub 3}){sub 4}[OPPh{sub 2}(C{sub 14}H{sub 9})]{sub 3}, C{sub 14}H{sub 9} = phenanthrenyl, was structurally characterized, and was found to be the first thorium compound isolated with three phosphine oxide ligands bound. The phosphine oxide ligands were not fluorescent but the anthracenyl-substituted ligand showed broad, red-shifted emission at approximately 50 nm relative to typical anthracene, making this ligand set a possibility for use in detection. The synthesis and spectroscopy of the uranyl and thorium complexes are presented.

  4. Characterization of Iron Oxide Generated in Ruthner Plant of Pickling Unit in Mobarakeh Steel Complex



    Reducing the chloride content in regenerated iron oxides (RIO) from steel-pickling acid waste economically treated by Ruthner process is the most critical issue for the development of RIO as a useful raw material resource. In this paper, the results of a new method for characterization and modification of RIO produced in Mobarakeh Steel Complex were reported.

  5. N-Heterocyclic Carbene-Palladium Complex Catalyzed Oxidative Carbonylation of Amines to Ureas

    ZHENG,Shu-Zhan; PENG,Xin-Gao; LIU,Jian-Ming; SUN,Wei; XIA,Chun-Gu


    Palladium carbene shows high efficiency without any promoter on oxidative carbonylation of amines to ureas and a new type of palladium carbene complex containing both an aniline and an NHC ligands was found to be the active species for the reaction.

  6. Direct observation of surface reconstruction and termination on a complex metal oxide catalyst by electron microscopy

    Zhu, Yihan


    On the surface: The surface reconstruction of an MoVTeO complex metal oxide catalyst was observed directly by various electron microscopic techniques and the results explain the puzzling catalytic behavior. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Copper(II)–imida‐salen Complexes Encapsulated into NaY Zeolite for Oxidations Reactions

    Kuźniarska‐Biernacka, Iwona; Carvalho, M. Alice; Rasmussen, Søren Birk


    The oxidation of phenol, cychohexanol and hydroquinone has been screened in the presence of copper(II) complexes with the Schiff‐base salen ligand, 1,5‐bis[(E)‐5‐chloro‐2‐hydroxybenzylideneamino]‐1H‐imidazole‐4‐carbonitrile, and encapsulated into NaY zeolite by using two different methods. The new...

  8. A trinuclear ruthenium complex as a highly efficient molecular catalyst for water oxidation.

    Zhang, L L; Gao, Y; Liu, Z; Ding, X; Yu, Z; Sun, L C


    A trinuclear ruthenium complex, 3, was designed and synthesized with the ligand 2,2'-bipyridine-6,6'-dicarboxylic acid (bda) and we found that this complex could function as a highly efficient molecular catalyst for water oxidation in homogeneous systems. This trinuclear molecular water oxidation catalyst, 3, displayed much higher efficiencies in terms of turnover numbers and initial oxygen evolution rate than its counterparts, a binuclear catalyst, 2, and a mononuclear catalyst, 1, in both chemically driven and photochemically driven water oxidation based on either the whole catalytic molecules or just the active Ru centers. The reasons for the superior performance of catalyst 3 were discussed and we believe that multiple Ru centers in a single molecule are indeed beneficial for increasing the probability of the formation of O-O bonds through an intramolecular radical coupling pathway.

  9. Nitric oxide production by chicken macrophages activated by Acemannan, a complex carbohydrate extracted from Aloe vera.

    Karaca, K; Sharma, J M; Nordgren, R


    Cultures of normal chicken spleen cells and HD11 line cells produce nitric oxide (NO) in response to Acemannan, a complex carbohydrate derived from the Aloe vera plant. Neither cell type produced detectable amounts of NO in response to similar concentrations of yeast mannan, another complex carbohydrate. Nitric oxide production was dose dependent and inhibitable by the nitric oxide synthase inhibitor NG-methyl-L-arginine. In addition, the production of NO was inhibited by preincubation of ACM with concanavalin A in a dose-dependent manner. These results suggest that ACM-induced NO synthesis may be mediated through macrophage mannose receptors, and macrophage activation may be accountable for some of the immunomodulatory effects of ACM in chickens.

  10. One-Pot Synthesis of Cu(II Complex with Partially Oxidized TTF Moieties

    Hiroki Oshio


    Full Text Available The one-pot synthesis of a Cu(II complex with partially oxidized tetrathiafulvalene (TTF moieties in its capping MT-Hsae-TTF ligands, [CuII(MT-sae-TTF2] [CuICl2] was realized by the simultaneous occurrence of Cu(II complexation and CuIICl2 mediated oxidation of TTF moieties. The crystal structure was composed of one-dimensional columns formed by partially oxidized TTF moieties and thus the cation radical salt showed relatively high electrical conductivity. Tight binding band structure calculations indicated the existence of a Peierls gap due to the tetramerization of the TTF moieties in the one-dimensional stacking column at room temperature, which is consistent with the semiconducting behavior of this salt.

  11. Highly effective water oxidation catalysis with iridium complexes through the use of NaIO4.

    Codolà, Zoel; Cardoso, João M S; Royo, Beatriz; Costas, Miquel; Lloret-Fillol, Julio


    Exceptional water oxidation (WO) turnover frequencies (TOF=17,000 h(-1)), and turnover numbers (TONs) close to 400,000, the largest ever reported for a metal-catalyzed WO reaction, have been found by using [Cp*Ir(III)(NHC)Cl2] (in which NHC=3-methyl-1-(1-phenylethyl)-imidazoline-2-ylidene) as the pre-catalyst and NaIO4 as oxidant in water at 40 °C. The apparent TOF for [Cp*Ir(III)(NHC)X2] (1X, in which X stands for I (1I), Cl (1Cl), or triflate anion (1OTf)) and [(Cp*-NHCMe)Ir(III)I2] (2) complexes, is kept constant during almost all of the O2 evolution reaction when using NaIO4 as oxidant. The TOF was found to be dependent on the ligand and on the anion (TOF ranging from ≈600 to ≈1100 h(-1) at 25 °C). Degradation of the complexes by oxidation of the organic ligands upon reaction with NaIO4 has been investigated. (1)H NMR, ESI-MS, and dynamic light-scattering measurements (DLS) of the reaction medium indicated that the complex undergoes rapid degradation, even at low equivalents of oxidant, but this process takes place without formation of nanoparticles. Remarkably, three-month-old solution samples of oxidized pre-catalysts remain equally as active as freshly prepared solutions. A UV/Vis feature band at λmax =405 nm is observed in catalytic reaction solutions only when O2 evolves, which may be attributed to a resting state iridium speciation, most probably Ir-oxo species with an oxidation state higher than IV.

  12. Data for effects of lanthanum complex on the thermo-oxidative aging of natural rubber

    Wei Zheng


    Full Text Available Novel mixed antioxidants composed of antioxidant IPPD and lanthanum (La complex were added as a filler to form natural rubber (NR composites. By mechanical testing, Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR and thermogravimetric analysis (TGA, a string of data, including the mechanical properties, the variation of internal groups and the thermal and thermo-oxidative decompositions of NR, was presented in this data article. The data accompanying its research article [1] studied the thermo-oxidative aging properties of NR in detail. The density function theoretical (DFT calculations were also used as an assistant to study the thermo-oxidative aging mechanism of NR. The data revealed that this new rare-earth antioxidant could indeed enhance the thermo-oxidative aging resistance of NR, which is associated with its different function mechanism from that of the pure antioxidant IPPD.

  13. Spectroscopic characterization of genotoxic chromium(V) peptide complexes: Oxidation of Chromium(III) triglycine, tetraglycine and pentaglycine complexes.

    Headlam, Henrietta A; Lay, Peter A


    Evidence is growing that metabolites of Cr(III) dietary supplements are partially oxidized to carcinogenic Cr(VI) and Cr(V) in vivo. Hence, we examined oxidations of Cr(III) peptide (triglycine, tetraglycine and pentaglycine) complexes to Cr(VI) and Cr(V) by PbO2 at 37°C and physiological pH values between 3.85 and 7.4. The products were characterized by EPR and UV/Vis spectroscopies and electrospray mass spectrometry. At pH3.85, the monomeric Cr(V) complexes produced were relatively unstable and degraded over min to hr under the acidic conditions. The triglycine and tetraglycine Cr(V) complexes had five-line (14)N-superhyperfine-coupled EPR signals; giso, (AN) values 1.9824 (2.44×10(-4)cm(-1)) and 1.9825 (2.43×10(-4)cm(-1)), respectively. The pentaglycine Cr(V) complex had a seven-line (14)N-superhyperfine-coupled EPR signal: giso=1.9844; AN=2.27×10(-4)cm(-1). In phosphate buffer (pH7.4 and 5.85), several Cr(V) intermediates were produced, but Cr(VI) was the end product. For the triglycine, tetraglycine and pentaglycine Cr(V) complexes, the giso (AN, 10(-4)cm(-1)) values were 1.9831 (2.17), 1.9843 (2.27) and 1.9844 (2.30), respectively. A second EPR signal with unresolved superhyperfine structure was observed at giso~1.966. At 1min, the tetraglycine and pentaglycine Cr(V) complexes, had another signal at giso~1.978, which decayed relative to the other signals with time. This chemistry has relevance to: (i) certain types of DNA damage produced by Cr carcinogens; (ii) the intracellular oxidation of Cr(III) to Cr(VI); and (iii) redox recycling of Cr(III) metabolites formed from both the intracellular reduction of carcinogenic Cr(VI) and from Cr(III) supplements.

  14. Near infrared electrochromic variable optical attenuator based on ruthenium complex and polycrystalline tungsten oxide

    ZHANG Jidong; WU Xianguo; YU Hongan; YAN Donghang; WANG Zhiyuan


    A near infrared (NIR) electrochromic attenuator based on a dinuclear ruthenium complex and polycrystalline tungsten oxide was fabricated and characterized. The results show that the use of the NIR-absorbing ruthenium complex as a counter electrode material can improve the device performance. By replacing the visible electrochromic ferrocene with the NIR-absorbing ruthenium complex, the optical attenuation at 1550 nm was enhanced from 19.1 to 30.0 dB and color efficiency also increased from 29.2 to 121.2 cm2/C.

  15. Protein Kinase A Governs Oxidative Phosphorylation Kinetics and Oxidant Emitting Potential at Complex I.

    Lark, Daniel S; Reese, Lauren R; Ryan, Terence E; Torres, Maria J; Smith, Cody D; Lin, Chien-Te; Neufer, P Darrell


    The mitochondrial electron transport system (ETS) is responsible for setting and maintaining both the energy and redox charges throughout the cell. Reversible phosphorylation of mitochondrial proteins, particularly via the soluble adenylyl cyclase (sAC)/cyclic AMP (cAMP)/Protein kinase A (PKA) axis, has recently been revealed as a potential mechanism regulating the ETS. However, the governance of cAMP/PKA signaling and its implications on ETS function are incompletely understood. In contrast to prior reports using exogenous bicarbonate, we provide evidence that endogenous CO2 produced by increased tricarboxylic acid (TCA) cycle flux is insufficient to increase mitochondrial cAMP levels, and that exogenous addition of membrane permeant 8Br-cAMP does not enhance mitochondrial respiratory capacity. We also report important non-specific effects of commonly used inhibitors of sAC which preclude their use in studies of mitochondrial function. In isolated liver mitochondria, inhibition of PKA reduced complex I-, but not complex II-supported respiratory capacity. In permeabilized myofibers, inhibition of PKA lowered both the K m and V max for complex I-supported respiration as well as succinate-supported H2O2 emitting potential. In summary, the data provided here improve our understanding of how mitochondrial cAMP production is regulated, illustrate a need for better tools to examine the impact of sAC activity on mitochondrial biology, and suggest that cAMP/PKA signaling contributes to the governance of electron flow through complex I of the ETS.

  16. Disruption of the Class IIa HDAC Corepressor Complex Increases Energy Expenditure and Lipid Oxidation

    Vidhi Gaur


    Full Text Available Drugs that recapitulate aspects of the exercise adaptive response have the potential to provide better treatment for diseases associated with physical inactivity. We previously observed reduced skeletal muscle class IIa HDAC (histone deacetylase transcriptional repressive activity during exercise. Here, we find that exercise-like adaptations are induced by skeletal muscle expression of class IIa HDAC mutants that cannot form a corepressor complex. Adaptations include increased metabolic gene expression, mitochondrial capacity, and lipid oxidation. An existing HDAC inhibitor, Scriptaid, had similar phenotypic effects through disruption of the class IIa HDAC corepressor complex. Acute Scriptaid administration to mice increased the expression of metabolic genes, which required an intact class IIa HDAC corepressor complex. Chronic Scriptaid administration increased exercise capacity, whole-body energy expenditure and lipid oxidation, and reduced fasting blood lipids and glucose. Therefore, compounds that disrupt class IIa HDAC function could be used to enhance metabolic health in chronic diseases driven by physical inactivity.

  17. An autocatalytic radical chain pathway in formation of an iron(IV)-oxo complex by oxidation of an iron(II) complex with dioxygen and isopropanol.

    Morimoto, Yuma; Lee, Yong-Min; Nam, Wonwoo; Fukuzumi, Shunichi


    Evidence of an autocatalytic radical chain pathway has been reported in formation of a non-heme iron(IV)-oxo complex by oxidation of an iron(II) complex with dioxygen and isopropanol in acetonitrile at 298 K. The radical chain reaction is initiated by hydrogen abstraction from isopropanol by the iron(IV)-oxo complex.

  18. Protein kinase A governs oxidative phosphorylation kinetics and oxidant emitting potential at complex I

    Daniel Stephen Lark


    Full Text Available The mitochondrial electron transport system (ETS is responsible for setting and maintaining both the energy and redox charges throughout the cell. Reversible phosphorylation of mitochondrial proteins, particularly via the soluble adenylyl cyclase (sAC/cyclic AMP (cAMP/Protein kinase A (PKA axis, has recently been revealed as a potential mechanism regulating the ETS. However, the governance of cAMP/PKA signaling and its implications on ETS function are incompletely understood. In contrast to prior reports using exogenous bicarbonate, we provide evidence that endogenous CO2 produced by increased tricarboxylic acid (TCA cycle flux is insufficient to increase mitochondrial cAMP levels, and that exogenous addition of membrane permeant 8Br-cAMP does not enhance mitochondrial respiratory capacity. We also report important non-specific effects of commonly used inhibitors of sAC which preclude their use in studies of mitochondrial function. In isolated liver mitochondria, inhibition of PKA reduces complex I-, but not complex II-supported respiratory capacity. In permeabilized myofibers, inhibition of PKA lowers both the Km and Vmax for complex I-supported respiration as well as succinate-supported H2O2 emitting potential. In summary, the data provided here improve our understanding of how mitochondrial cAMP production is regulated, illustrate a need for better tools to examine the impact of sAC activity on mitochondrial biology, and suggest that cAMP/PKA signaling contributes to the governance of electron flow through complex I of the ETS.

  19. Fluorescence turn-on detection of gaseous nitric oxide using ferric dithiocarbamate complex functionalized quantum dots.

    Sun, Jian; Yan, Yehan; Sun, Mingtai; Yu, Huan; Zhang, Kui; Huang, Dejian; Wang, Suhua


    Functional quantum dots (QDs) grafted with ferric dithiocarbamate complex layers (QDs-Fe(III)(DTC)3) were fabricated and demonstrated to be selectively reactive to nitric oxide. The dithiocarbamate (DTC) was covalently conjugated to the amine-coated QDs by a condensation reaction of the carboxyl in DTC and the amino polymer in surface of QDs. The weak fluorescence of QDs-Fe(III)(DTC)3 was attributed to the energy transfer between CdSe/ZnS and Fe(III)(DTC)3 complex at the surface of the functionalized quantum dots. Nitric oxide could greatly switch on the fluorescence of QDs-Fe(III)(DTC)3 by displacing the DTC in the Fe(III)(DTC)3 accompanied by reducing Fe(III) to Fe(II), thus shutting off the energy transfer way. The limit of detection for nitric oxide was estimated to be 3.3 μM and the specific detection was not interfered with other reactive oxygen species. Moreover, the probe was demonstrated for the sensing of gaseous nitric oxide, and the visual detection limit was as low as 10 ppm, showing the potential for sensing nitric oxide by the naked eye.

  20. Pt(II) coordination complexes as visible light photocatalysts for the oxidation of sulfides using batch and flow processes

    Casado-Sánchez, A.; Gómez-Ballesteros, R.; Tato, F.; Soriano, F.J.; Pascual-Coca, G.; Cabrera, S.; J. Alemán


    A new catalytic system for the photooxidation of sulfides based on Pt(ii) complexes is presented. The catalyst is capable of oxidizing a large number of sulfides containing aryl, alkyl, allyl, benzyl, as well as more complex structures such as heterocycles and methionine amino acid, with complete chemoselectivity. In addition, the first sulfur oxidation in a continuous flow process has been developed

  1. Phase transitions via selective elemental vacancy engineering in complex oxide thin films

    Lee, Sang A.; Jeong, Hoidong; Woo, Sungmin; Hwang, Jae-Yeol; Choi, Si-Young; Kim, Sung-Dae; Choi, Minseok; Roh, Seulki; Yu, Hosung; Hwang, Jungseek; Kim, Sung Wng; Choi, Woo Seok


    Defect engineering has brought about a unique level of control for Si-based semiconductors, leading to the optimization of various opto-electronic properties and devices. With regard to perovskite transition metal oxides, O vacancies have been a key ingredient in defect engineering, as they play a central role in determining the crystal field and consequent electronic structure, leading to important electronic and magnetic phase transitions. Therefore, experimental approaches toward understanding the role of defects in complex oxides have been largely limited to controlling O vacancies. In this study, we report on the selective formation of different types of elemental vacancies and their individual roles in determining the atomic and electronic structures of perovskite SrTiO3 (STO) homoepitaxial thin films fabricated by pulsed laser epitaxy. Structural and electronic transitions have been achieved via selective control of the Sr and O vacancy concentrations, respectively, indicating a decoupling between the two phase transitions. In particular, O vacancies were responsible for metal-insulator transitions, but did not influence the Sr vacancy induced cubic-to-tetragonal structural transition in epitaxial STO thin film. The independent control of multiple phase transitions in complex oxides by exploiting selective vacancy engineering opens up an unprecedented opportunity toward understanding and customizing complex oxide thin films.

  2. A study of the Fenton-mediated oxidation of methylene blue-cucurbit[n]uril complexes.

    Fuenzalida, Tomás; Fuentealba, Denis


    Cucurbit[n]urils efficiently decreased the Fenton-mediated oxidation of encapsulated dyes, providing a mechanism for some control and selectivity over the degradation. The encapsulation of methylene blue into cucurbit[7]uril made it highly refractory against Fenton oxidation in the dark or under UVA light irradiation. However, the oxidation of the encapsulated dye was significantly enhanced under visible light irradiation. This behavior was selective for the cucurbit[7]uril complex and not for the cucurbit[8]uril complex, which achieved the same degree of protection irrespective of the irradiation conditions. This different reactivity of the complexes was further discussed in terms of their excited state properties. The main mechanism for protection was the seclusion of the dye into cucurbit[n]urils as shown by the fact that the non-encapsulated dye safranin was protected much less than methylene blue. Additionally, cucurbit[n]urils efficiently trapped hydroxyl radicals, which contributed significantly to the protection of the dyes from Fenton-mediated oxidation.

  3. Defining the electronic and geometric structure of one-electron oxidized copper-bis-phenoxide complexes.

    Storr, Tim; Verma, Pratik; Pratt, Russell C; Wasinger, Erik C; Shimazaki, Yuichi; Stack, T Daniel P


    The geometric and electronic structure of an oxidized Cu complex ([CuSal](+); Sal = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-(1R,2R)-diamine) with a non-innocent salen ligand has been investigated both in the solid state and in solution. Integration of information from UV-vis-NIR spectroscopy, magnetic susceptibility, electrochemistry, resonance Raman spectroscopy, X-ray crystallography, X-ray absorption spectroscopy, and density functional theory calculations provides critical insights into the nature of the localization/delocalization of the oxidation locus. In contrast to the analogous Ni derivative [NiSal](+) (Storr, T.; et al. Angew. Chem., Int. Ed. 2007, 46, 5198), which exists solely in the Ni(II) ligand-radical form, the locus of oxidation is metal-based for [CuSal](+), affording exclusively a Cu(III) species in the solid state (4-300 K). Variable-temperature solution studies suggest that [CuSal](+) exists in a reversible spin-equilibrium between a ligand-radical species [Cu(II)Sal(*)](+) (S = 1) and the high-valent metal form [Cu(III)Sal](+) (S = 0), indicative of nearly isoenergetic species. It is surprising that a bis-imine-bis-phenolate ligation stabilizes the Cu(III) oxidation state, and even more surprising that in solution a spin equilibrium occurs without a change in coordination number. The oxidized tetrahydrosalen analogue [CuSal(red)](+) (Sal(red) = N,N'-bis(3,5-di- tert-butylhydroxybenzyl)-1,2-cyclohexane-(1R,2R)-diamine) exists as a temperature-invariant Cu(II)-ligand-radical complex in solution, demonstrating that ostensibly simple variations of the ligand structure affect the locus of oxidation in Cu-bis-phenoxide complexes.

  4. Influence of bidentate structure of an aryl phosphine oxide ligand on photophysical properties of its Eu~Ⅲ complex

    许辉; 魏莹; 赵保敏; 黄维


    The bidentate phosphine oxide ligand 1,8-bis(diphenylphosphino) naphthalene oxide (NAPO) and its EuⅢ complex 1 Eu(TTA)3(NAPO) (TTA=2-thenoyltrifluoroacetonate) were chosen to study the effect of bidentate phosphine oxide ligand on the photophysical properties of the corresponding complex. The intramolecular energy transfer processes of 1 were studied. The investigation showed that with bidentate structure NAPO could suppress solvent-induced quenching by enforcing the ligand-ligand interaction and the rigidi...

  5. A new entry to asymmetric platinum(IV) complexes via oxidative chlorination.

    Ravera, Mauro; Gabano, Elisabetta; Pelosi, Giorgio; Fregonese, Federico; Tinello, Stefano; Osella, Domenico


    Pt(IV) complexes are usually prepared by oxidation of the corresponding Pt(II) counterparts, typically using hydrogen peroxide or chlorine. A different way to synthesize asymmetrical Pt(IV) compounds is the oxidative chlorination of Pt(II) counterparts with N-chlorosuccinimide. The reaction between cisplatin cis-[PtCl2(NH3)2], carboplatin, cis-[PtCl2(dach)] and cis-[Pt(cbdc)(dach)] (cbdc = cyclobutane-1,1'-dicarboxylato; dach = cyclohexane-1R,2R-diamine) with N-chlorosuccinimide in ethane-1,2-diol was optimized to produce the asymmetric Pt(IV) octahedral complexes [PtA2Cl(glyc)X2] (A2 = 2 NH3 or dach; glyc = 2-hydroxyethanolato; X2 = 2 Cl or cbdc) in high yield and purity. The X-ray crystal structure of the [Pt(cbdc)Cl(dach)(glyc)] complex is also reported. Moreover, the oxidation method proved to be versatile enough to produce other mixed Pt(IV) derivatives varying the reaction medium. The two trichlorido complexes easily undergo a pH-dependent hydrolysis reaction, whereas the dicarboxylato compounds are stable enough to allow further coupling reactions for drug targeting and delivery via the glyc reactive pendant. Therefore, the coupling reaction between the [Pt(cbdc)Cl(dach)(glyc)] and a model carboxylic acid, a model amine, and selectively protected amino acids is reported.

  6. Effect of ligand denticity on the nitric oxide reactivity of cobalt(ii) complexes.

    Deka, Hemanta; Ghosh, Somnath; Saha, Soumen; Gogoi, Kuldeep; Mondal, Biplab


    The activation of nitric oxide (NO) by transition metal complexes has attracted a wide range of research activity. To study the role of ligand denticity on the NO reactivity of Co(ii) complexes, three complexes (, and ) were prepared with ligands , and [ = N(1),N(2)-bis(2,4,6-trimethylbenzyl)ethane-1,2-diamine; = N(1)-(2,4,6-trimethylbenzyl)-N(2)-(2-((2,4,6-trimethylbenzyl)amino)ethyl)ethane-1,2-diamine] and = N(1)-(2,4,6-trimethylbenzyl)-N(2),N(2)-bis(2-((2,4,6-trimethylbenzyl)amino)ethyl)ethane-1,2-diamine], respectively. The complexes differ from each other in terms of denticity and flexibility of the ligand frameworks. In degassed methanol solution, they were exposed to NO gas and their reactivity was studied using various spectroscopic techniques. In the case of complex with a bidentate ligand, reductive nitrosylation of the metal ion with concomitant dinitrosation of the ligand framework was observed. Complex with a tridentate ligand did not undergo reductive nitrosylation; rather, the formation of [Co(III)(NO(-))] was observed. The nitrosyl complexes were isolated and structurally characterized. On the other hand, complex with a tetradentate tripodal ligand did not react with NO. This can be attributed to the geometry of the complex as well as due to the accessibility of the corresponding redox potential.

  7. Insights into amine binding to biaryl phosphine palladium oxidative addition complexes and reductive elimination from biaryl phosphine arylpalladium amido complexes via density functional theory.

    Barder, Timothy E; Buchwald, Stephen L


    We present results on the binding of a variety amines to monoligated oxidative addition complexes of the type L1Pd(Ar)Cl, where L is 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (SPhos, 1) or 2-dicyclohexylphosphino-2',4',6'-tri-ispropylbiphenyl (XPhos, 2). The binding of an amine to oxidative addition complexes composed of 1 and 2 is more complex than with smaller ligands as intermediate Pd(II) complexes with bulky biaryl phosphine ligands disfavor amine binding to favorable conformations of oxidative addition complexes. Additionally, thermodynamic and kinetic parameters for reductive elimination from complexes of the type L1Pd(amido)Ph (where amido = EtNH, Me2N, PhNH) are discussed. From this data, we suggest a possible mechanism for (biaryl phosphine) Pd-catalyzed amination reactions that is more intricate than previously thought.

  8. In-situ formation of complex oxide precipitates during processing of oxide dispersion strengthened ferritic steels

    Jayasankar, K., E-mail: [CSIR-Institute of Minerals & Materials Technology, Bhubaneswar 751013 (India); Pandey, Abhishek [CSIR-Advanced Materials & Processes Research Institute, Bhopal 462026 (India); Mishra, B.K. [CSIR-Institute of Minerals & Materials Technology, Bhubaneswar 751013 (India); Das, Siddhartha [Indian Institute of Technology, Kharagpur 721302 (India)


    Highlights: • Use of dual drive planetary ball mill for Bench scale (>1 kg) production. • X-ray diffraction and TEM were used to study transformations during sintering. • HIPped and rolled samples with nearly 99% density successfully produced. - Abstract: In fusion and fission reactor material development, ODS alloys are the most suitable candidate materials due to its high temperature creep properties and irradiation resistance properties. This paper describes the preparation of oxide dispersion strengthened alloy powder in large quantity (>1 kg batch) in dual drive planetary ball mill using pre-alloyed ferrtic steel powder with nano sized Y{sub 2}O{sub 3}. The consolidation of the powders was carried out in hot isostatic press (HIP) followed by hot rolling. 99% of the theoretical density was achieved by this method. The vickers hardness values of pressed and rolled samples were in the range of 380 ± 2HV and 719 ± 2HV, respectively. Samples were further investigated using X-ray diffraction particle size analyzer and electron microscope. Initial increase in particle size with milling was observed showing flattening of the particle. It was found that 5 h of milling time is sufficient to reduce the particle size to achieve the desired size. Transmission electron microscopy analysis of milled ODS steel powder revealed a uniform distribution of combustion synthesized nano-Y{sub 2}O{sub 3} in ferritic steel matrix after a milling time of 5 h. Preliminary results demonstrated suitability of dual drive planetary ball mill for mass production of alloy within a short time due to various kinds of forces acting at a time during milling process. Fine monoclinic Y{sub 2}Si{sub 2}O{sub 7} precipitates were also observed in the steel. This study explains the particle characteristics of nano Y{sub 2}O{sub 3} dispersed ODS powder and formation of nano clusters in ODS ferritic alloy.

  9. Synthesis,Structure and Antitumor Activity of Dibutyltin Oxide Complex with 5-Fluorouracil Derivatives

    左代姝; 江涛; 管华诗; 戚欣; 王奎旗; 施展


    The dibutyltin( Ⅳ) oxide complex reacts with 5-fluorouracil-1-propanonic or5-fluorouracil-1-acetic acid to give the potential antitumor activity complexes [( 5-fluorouracil )-1-(CH2)=COOSn(Bu-n)2]4O2[m =1, (1); m =2, (2)]which were determined by IR and 1H NMR. The crystal structure determination shows that complex 2 is a dimmer, in which two [(5-fluorouracil)-1-CH2CH2COOSn(Bu-n )2]20units are linked by bridging oxygen atom, and the tin atoms adopt distorted trigonal bipyramids via two carbons from dibutyl group and three oxygen atoms from 5-fluorouracil and bridging oxygen. In vitro test shows complexes 1 and 2 exhibit high cytotoxicity against OVCAR-3 and PC-14.

  10. Aliphatic C-H bond oxidation of toluene using copper peroxo complexes that are stable at room temperature.

    Würtele, Christian; Sander, Ole; Lutz, Volker; Waitz, Thomas; Tuczek, Felix; Schindler, Siegfried


    Dinuclear copper peroxo complexes obtained from mononuclear copper(I) complexes showed extremely high stabilities under ambient conditions in the solid state and could be heated above 100 degrees C without decomposition. The increased stability could be explained with regard to their molecular structures. Furthermore, the four complexes investigated showed a high potential for aliphatic C-H bond oxidations: for example, technical-grade toluene was oxidized to benzaldehyde in yields of up to 20%.

  11. Indefinitely stable iron(IV) cage complexes formed in water by air oxidation

    Tomyn, Stefania; Shylin, Sergii I.; Bykov, Dmytro; Ksenofontov, Vadim; Gumienna-Kontecka, Elzbieta; Bon, Volodymyr; Fritsky, Igor O.


    In nature, iron, the fourth most abundant element of the Earth's crust, occurs in its stable forms either as the native metal or in its compounds in the +2 or +3 (low-valent) oxidation states. High-valent iron (+4, +5, +6) compounds are not formed spontaneously at ambient conditions, and the ones obtained synthetically appear to be unstable in polar organic solvents, especially aqueous solutions, and this is what limits their studies and use. Here we describe unprecedented iron(IV) hexahydrazide clathrochelate complexes that are assembled in alkaline aqueous media from iron(III) salts, oxalodihydrazide and formaldehyde in the course of a metal-templated reaction accompanied by air oxidation. The complexes can exist indefinitely at ambient conditions without any sign of decomposition in water, nonaqueous solutions and in the solid state. We anticipate that our findings may open a way to aqueous solution and polynuclear high-valent iron chemistry that remains underexplored and presents an important challenge.

  12. Oxidative Heck vinylation for the synthesis of complex dienes and polyenes.

    Delcamp, Jared H; Gormisky, Paul E; White, M Christina


    We introduce an oxidative Heck reaction for selective complex diene and polyene formation. The reaction proceeds via oxidative Pd(II)/sulfoxide catalysis that retards palladium-hydride isomerizations which previously limited the Heck manifold's capacity for furnishing stereodefined conjugated dienes. Limiting quantities of nonactivated terminal olefins (1 equiv) and slight excesses of vinyl boronic esters (1.5 equiv) that feature diverse functionality can be used to furnish complex dienes and polyenes in good yields and excellent selectivities (generally E:Z = >20:1; internal:terminal = >20:1). Because this reaction only requires prior activation of a single vinylic carbon, improvements in efficiency are observed for synthetic sequences relative to ones featuring reactions that require activation of both coupling partners.

  13. Crystal Structure of Oxidative Stress Sensor Keap1 in Complex with Selective Autophagy Substrate p62

    Kurokawa, Hirofumi

    Keap1, an adaptor protein of cullin-RING ubiquitin ligase complex, represses cytoprotective transcription factor Nrf2 in an oxidative stress-dependent manner. The accumulation of selective autophagy substrate p62 also activates Nrf2 target genes, but the detailed mechanism has not been elucidated. Crystal structure of Keap1-p62 complex revealed the structural basis for the Nrf2 activation in which Keap1 is inactivated by p62. The accumulation of p62 is observed in hepatocellular carcinoma. The activation of Nrf2 target genes, including detoxifying enzymes and efflux transporters, by p62 may protect the cancer cells from anti-cancer drugs.

  14. New complexes of heteroaromatic N-oxides with europium, uranyl and zinc ions

    Zbigniew Hnatejko


    New solid complexes of europium,uranyl and zinc ions with N-oxides of 4-chloro-2,6-dimethylpyridine,quinoline and 4-methoxyquinaldinic acid in presence different anions were obtained and characterized by elemental and TG analyses,IR and luminescence spectra.The compounds are crystalline,hydrated or anhydrous salts with colours typical of metal ions.Thermal studies showed that in hydrated salts lattice or coordination water molecules are present.A role of different anions in the formation of various types of the complexes is presented.

  15. Transport Properties of Complex Oxides: New Ideas and Insights from Theory and Simulation

    Benedek, Nicole

    Complex oxides are one of the largest and most technologically important materials families. The ABO3 perovskite oxides in particular display an unparalleled variety of physical properties. The microscopic origin of these properties (how they arise from the structure of the material) is often complicated, but in many systems previous research has identified simple guidelines or `rules of thumb' that link structure and chemistry to the physics of interest. For example, the tolerance factor is a simple empirical measure that relates the composition of a perovskite to its tendency to adopt a distorted structure. First-principles calculations have shown that the tendency towards ferroelectricity increases systematically as the tolerance factor of the perovskite decreases. Can we uncover a similar set of simple guidelines to yield new insights into the ionic and thermal transport properties of perovskites? I will discuss recent research from my group on the link between crystal structure and chemistry, soft phonons and ionic transport in a family of layered perovskite oxides, the Ln2NiO4+δ Ruddlesden-Popper phases. In particular, we show how the lattice dynamical properties of these materials (their tendency to undergo certain structural distortions) can be correlated with oxide ion transport properties. Ultimately, we seek new ways to understand the microscopic origins of complex transport processes and to develop first-principles-based design rules for new materials based on our understanding.

  16. Catalytic water oxidation by mononuclear Ru complexes with an anionic ancillary ligand.

    Tong, Lianpeng; Inge, A Ken; Duan, Lele; Wang, Lei; Zou, Xiaodong; Sun, Licheng


    Mononuclear Ru-based water oxidation catalysts containing anionic ancillary ligands have shown promising catalytic efficiency and intriguing properties. However, their insolubility in water restricts a detailed mechanism investigation. In order to overcome this disadvantage, complexes [Ru(II)(bpc)(bpy)OH2](+) (1(+), bpc = 2,2'-bipyridine-6-carboxylate, bpy = 2,2'-bipyridine) and [Ru(II)(bpc)(pic)3](+) (2(+), pic = 4-picoline) were prepared and fully characterized, which features an anionic tridentate ligand and has enough solubility for spectroscopic study in water. Using Ce(IV) as an electron acceptor, both complexes are able to catalyze O2-evolving reaction with an impressive rate constant. On the basis of the electrochemical and kinetic studies, a water nucleophilic attack pathway was proposed as the dominant catalytic cycle of the catalytic water oxidation by 1(+), within which several intermediates were detected by MS. Meanwhile, an auxiliary pathway that is related to the concentration of Ce(IV) was also revealed. The effect of anionic ligand regarding catalytic water oxidation was discussed explicitly in comparison with previously reported mononuclear Ru catalysts carrying neutral tridentate ligands, for example, 2,2':6',2″-terpyridine (tpy). When 2(+) was oxidized to the trivalent state, one of its picoline ligands dissociated from the Ru center. The rate constant of picoline dissociation was evaluated from time-resolved UV-vis spectra.

  17. Optimization of citrate complex combustion for synthesis of transition metal oxide nanostructures

    Nair, V.M. [Dept. of Physics, University College, University of Kerala, Trivandrum 695 034 (India); Jose, R., E-mail: [Faculty of Industrial Sciences and Technology, Universiti Malaysia Pahang, Kuantan 26300 (Malaysia); Raju, K.; Wariar, P.R.S. [Dept. of Physics, University College, University of Kerala, Trivandrum 695 034 (India)


    Highlights: ► We optimized citric acid in a solution combustion process using DFT calculations. ► The amount of citric acid can be reduced than that is conventionally used. ► Complex perovskite ceramic oxides were synthesized to validate the calculations. ► Single phase nanoparticles were obtained using the optimized process. ► Temperature of the combustion flame was much lower for the optimized amount. -- Abstract: Combustion of citrate complex is a popular choice to synthesize nanocrystals of transition metal oxides in a single-step process. The amount of citric acid used for combustion is conventionally calculated based on the total valence of the oxidizing and reducing agents while keeping the equivalent ratio unity such that combustion energy is a maximum. This paper demonstrates by employing quantum chemical calculations that the amount of citric acid could be reduced to nearly two-third if prepared for appreciable amounts. Transition metal oxides belong to quaternary double perovskite has been synthesized as nanocrystals as examples to validate the calculations.

  18. Wide band gap tunability in complex transition metal oxides by site-specific substitution

    Choi, Woo Seok; Chisholm, Matthew F.; Singh, David J.; Choi, Taekjib; Jellison Jr, Gerald E.; Lee, Ho Nyung


    Fabricating complex transition metal oxides with a tuneable band gap without compromising their intriguing physical properties is a longstanding challenge. Here we examine the layered ferroelectric bismuth titanate and demonstrate that, by site-specific substitution with the Mott insulator lanthanum cobaltite, its band gap can be narrowed as much as one electron volt, while remaining strongly ferroelectric. We find that when a specific site in the host material is preferentially substituted, ...

  19. Synthesis, structures, and luminescent properties of lanthanide complexes with triphenylphospine oxide

    Ma, Yan; Xu, Shan; Wang, Xin; Li, Yue-Xue; Jin, Qiong-Hua [Department of Chemistry, Capital Normal University, Beijing (China); Liu, Min [The College of Materials Science and Engineering, Beijing University of Technology (China); Xin, Xiu-Lan [School of Food and Chemical Engineering, Beijing Technology and Business University (China)


    Seven lanthanide complexes [Ln(OPPh{sub 3}){sub 3}(NO{sub 3}){sub 3}] (1-3) (OPPh{sub 3} = triphenylphosphine oxide, Ln = Nd, Sm, Gd), [Dy(OPPh{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}) (4), [Ln(OPPh{sub 3}){sub 3}(NO{sub 3}){sub 3}]{sub 2} (5-7) (Ln = Pr, Eu, Gd) were synthesized by the reactions of different lanthanide salts and OPPh{sub 3} ligand in the air. These complexes were characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows that complexes 1-4 are mononuclear complexes formed by OPPh{sub 3} ligands and nitrates. The asymmetric units of complexes 5-7 consist of two crystallographic-separate molecules. Complex 1 is self-assembled to construct a 2D layer-structure of (4,4) net topology by hydrogen bond interactions. The other complexes show a 1D chain-like structure that was assembled by OPPh{sub 3} ligands and nitrate ions through C-H..O interactions. Solid emission spectra of compounds 4 and 6 are assigned to the characteristic fluorescence of Tb{sup 3+} (λ{sub em} = 480, 574 nm) and Eu{sup 3+} (λ{sub em} = 552, 593, 619, 668 nm). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Arene control over thiolate to sulfinate oxidation in albumin by organometallic ruthenium anticancer complexes.

    Hu, Wenbing; Luo, Qun; Ma, Xiaoyan; Wu, Kui; Liu, Jianan; Chen, Yi; Xiong, Shaoxiang; Wang, Jianping; Sadler, Peter J; Wang, Fuyi


    Interactions of organometallic ruthenium anticancer complexes [Ru(eta6-arene)Cl(en)][PF6] (arene=p-cymene (1) or biphenyl (2), en=ethylenediamine) with human serum albumin were investigated by means of mass spectrometry combined with trypsin digestion, specific sidechain modifications and computational modelling. Both complexes were shown to bind to surface histidine (His128, His247, His510) and methionine (Met298) residues in human albumin, but only the p-cymene complex can gain entry to the crevice containing the free cysteine thiolate (Cys34) and induce oxidation to sulfinate. The two complexes exhibit a similar coordination preference for histidine and methionine residues on the protein surface. His128 binding is favoured both kinetically and thermodynamically. At 310 K, six days of incubation of recombinant human albumin (rHA) with complex 1 (rHA:Ru 50:250 microM) led to about 18 % ruthenation of His128 in the protein. However, the extent of ruthenation of albumin by complex 2 was less than that by 1, due to the steric hindrance from the biphenyl ligand. These results imply that the arene ligand in the organometallic ruthenium anticancer complexes plays a crucial role in interactions with proteins.

  1. Stereoselective Alkane Oxidation with meta-Chloroperoxybenzoic Acid (MCPBA) Catalyzed by Organometallic Cobalt Complexes.

    Shul'pin, Georgiy B; Loginov, Dmitriy A; Shul'pina, Lidia S; Ikonnikov, Nikolay S; Idrisov, Vladislav O; Vinogradov, Mikhail M; Osipov, Sergey N; Nelyubina, Yulia V; Tyubaeva, Polina M


    Cobalt pi-complexes, previously described in the literature and specially synthesized and characterized in this work, were used as catalysts in homogeneous oxidation of organic compounds with peroxides. These complexes contain pi-butadienyl and pi-cyclopentadienyl ligands: [(tetramethylcyclobutadiene)(benzene)cobalt] hexafluorophosphate, [(C₄Me₄)Co(C₆H₆)]PF₆ (1); diiodo(carbonyl)(pentamethylcyclopentadienyl)cobalt, Cp*Co(CO)I₂ (2); diiodo(carbonyl)(cyclopentadienyl)cobalt, CpCo(CO)I₂ (3); (tetramethylcyclobutadiene)(dicarbonyl)(iodo)cobalt, (C₄Me₄)Co(CO)₂I (4); [(tetramethylcyclobutadiene)(acetonitrile)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [(C₄Me₄)Co(bipy)(MeCN)]PF₆ (5); bis[dicarbonyl(B-cyclohexylborole)]cobalt, [(C₄H₄BCy)Co(CO)₂]₂ (6); [(pentamethylcyclopentadienyl)(iodo)(1,10-phenanthroline)cobalt] hexafluorophosphate, [Cp*Co(phen)I]PF₆ (7); diiodo(cyclopentadienyl)cobalt, [CpCoI₂]₂ (8); [(cyclopentadienyl)(iodo)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [CpCo(bipy)I]PF₆ (9); and [(pentamethylcyclopentadienyl)(iodo)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [Cp*Co(bipy)I]PF₆ (10). Complexes 1 and 2 catalyze very efficient and stereoselective oxygenation of tertiary C-H bonds in isomeric dimethylcyclohexanes with MCBA: cyclohexanols are produced in 39 and 53% yields and with the trans/cis ratio (of isomers with mutual trans- or cis-configuration of two methyl groups) 0.05 and 0.06, respectively. Addition of nitric acid as co-catalyst dramatically enhances both the yield of oxygenates and stereoselectivity parameter. In contrast to compounds 1 and 2, complexes 9 and 10 turned out to be very poor catalysts (the yields of oxygenates in the reaction with cis-1,2-dimethylcyclohexane were only 5%-7% and trans/cis ratio 0.8 indicated that the oxidation is not stereoselective). The chromatograms of the reaction mixture obtained before and after reduction with PPh₃ are very similar, which testifies that alkyl

  2. Experimental Investigation of In-Situ Chemical Oxidation of Complex DNAPL Source Zones by Permanganate

    Heiderscheidt, J. L.; Illangasekare, T. H.; Siegrist, R. L.


    Remediation of aquifers contaminated with organic waste chemicals that are in the form of dense non-aqueous phase liquids pose many challenges. The contaminated source zones are naturally heterogeneous and the unstable behavior of DNAPLs results in complex entrapment architecture. Some of the remediation schemes rely on effective delivery of treating agents to the locations where the DNAPLs are entrapped. During remediation, the source zone conditions may change, thus affecting the delivery efficiency of the treating agent. One such technology of DNAPL source zone treatment, in-situ chemical oxidation is designed to speed up remediation of a contaminant source zone by inducing increased mass transfer from DNAPL sources into the aqueous phase for subsequent destruction. Individual sources may be present as pools of high saturation, regions of disconnected ganglia at residual saturation, or some combination. Oxidation using permanganate generates manganese oxide (MnO2 (s)) precipitates. Research has shown that these solids, as with other remedial technologies, can result in permeability reductions in the bulk source zone reducing the ability for oxidant to be transported to individual sources. Solids can also form at the DNAPL-water interface, decreasing contact of the oxidant with the DNAPL source. Consequently, MnO2 (s) formation may alter the mass transfer rate from DNAPL into the aqueous phase, diminishing the magnitude of any mass depletion increase induced by oxidation. A two-dimensional intermediate scale tank experiment was performed, spatially monitoring permeability changes and relating them to MnO2 (s) distribution measured through post-oxidation soil coring. Sampling of aqueous PCE, chloride, and permanganate concentrations was used to relate changes in mass flux from DNAPL residual and pool source zones to MnO2 (s) formation. For the conditions of this experiment, MnO2 (s) formation reduced aqueous permeability in and around DNAPL sources resulting in

  3. Energy transfer processes in Tb(III)-dibenzoylmethanate complexes with phosphine oxide ligands

    Silva Junior, Francisco A.; Nascimento, Helenise A.; Pereira, Dariston K.S.; Teotonio, Ercules E.S.; Espinola, Jose Geraldo P.; Faustino, Wagner M., E-mail: [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil). Departamento de Quimica; Brito, Hermi F. [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Quimica. Departamento de Quimica Fundamental; Felinto, Maria Claudia F.C. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), SP (Brazil); Sa, Gilberto F. [Universidade Federal de Pernambuco (UFPE/CCEN), Recife, PE (Brazil). Centro de Ciencias Exatas e da Natureza. Departamento de Quimica Fundamental


    The Tb{sup 3+}-{beta}-diketonate complexes [Tb(DBM){sub 3}L], [Tb(DBM){sub 2}(NO{sub 3})L{sub 2}] and [Tb(DBM)(NO{sub 3}){sub 2} (HMPA){sub 2}] (DBM = dibenzoylmethanate; L: TPPO triphenylphosphine oxide or HMPA=hexamethylphosphine oxide) were prepared and characterized by elemental analysis (CHN), complexometric titration with EDTA and Fourier transform infrared (FTIR) spectroscopy, and the photoluminescence properties evaluated. The triplet state energies of the coordinated DBM ligands were determined using time-resolved phosphorescence spectra of analogous Gd{sup 3+} complexes. The results show that the energies increase along with the number of coordinated nitrate anions replacing the DBM ligand in the complexes. The luminescence spectra and emission lifetime measurements revealed that the ligand-to-metal energy transfer efficiency follows the same tendency. Unlike the tris-DBM complexes, bis- and mono-DBM presented high luminescence, and may act as promising candidates for preparation of the emitting layer of light converting molecular devices (LCMDs). (author)

  4. Water oxidation chemistry of a synthetic dinuclear ruthenium complex containing redox-active quinone ligands.

    Isobe, Hiroshi; Tanaka, Koji; Shen, Jian-Ren; Yamaguchi, Kizashi


    We investigated theoretically the catalytic mechanism of electrochemical water oxidation in aqueous solution by a dinuclear ruthenium complex containing redox-active quinone ligands, [Ru2(X)(Y)(3,6-tBu2Q)2(btpyan)](m+) [X, Y = H2O, OH, O, O2; 3,6-tBu2Q = 3,6-di-tert-butyl-1,2-benzoquinone; btpyan =1,8-bis(2,2':6',2″-terpyrid-4'-yl)anthracene] (m = 2, 3, 4) (1). The reaction involves a series of electron and proton transfers to achieve redox leveling, with intervening chemical transformations in a mesh scheme, and the entire molecular structure and motion of the catalyst 1 work together to drive the catalytic cycle for water oxidation. Two substrate water molecules can bind to 1 with simultaneous loss of one or two proton(s), which allows pH-dependent variability in the proportion of substrate-bound structures and following pathways for oxidative activation of the aqua/hydroxo ligands at low thermodynamic and kinetic costs. The resulting bis-oxo intermediates then undergo endothermic O-O radical coupling between two Ru(III)-O(•) units in an anti-coplanar conformation leading to bridged μ-peroxo or μ-superoxo intermediates. The μ-superoxo species can liberate oxygen with the necessity for the preceding binding of a water molecule, which is possible only after four-electron oxidation is completed. The magnitude of catalytic current would be limited by the inherent sluggishness of the hinge-like bending motion of the bridged μ-superoxo complex that opens up the compact, hydrophobic active site of the catalyst and thereby allows water entry under dynamic conditions. On the basis of a newly proposed mechanism, we rationalize the experimentally observed behavior of electrode kinetics with respect to potential and discuss what causes a high overpotential for water oxidation by 1.

  5. Multi-Electron Oxidation of Anthracene Derivatives by Nonheme Manganese(IV)-Oxo Complexes.

    Sharma, Namita; Jung, Jieun; Lee, Yong-Min; Seo, Mi Sook; Nam, Wonwoo; Fukuzumi, Shunichi


    Six-electron oxidation of anthracene to anthraquinone by a nonheme Mn(IV)-oxo complex, [(Bn-TPEN)MnIV(O)]2+, proceeds via the rate-determining electron transfer from anthracene to [(Bn-TPEN)MnIV(O)]2+, followed by subsequent fast oxidation reactions to give anthraquinone. The reduced Mn(II) complex ([(Bn-TPEN)MnII]2+) is oxidized by [(Bn-TPEN)MnIV(O)]2+ rapidly to produce the μ-oxo dimer ([(Bn-TPEN)MnIII-O-MnIII(Bn-TPEN)]4+). The oxygen atoms of the anthraquinone product were found to derive from the manganese-oxo species by the 18O labelling experiments. In the presence of Sc3+ ion, formation of anthracene radical cation was directly detected in electron transfer from anthracene to a Sc3+ ion-bound MnIV(O) com-plex, [(Bn-TPEN)MnIV(O)-(Sc(OTf)3)2]2+, followed by subsequent further oxidation to yield anthraquinone. When anthracene was replaced by 9,10-dimethylanthracene, elec-tron transfer from 9,10-dimethylanthracene to [(Bn-TPEN)MnIV(O)-(Sc(OTf)3)2]2+ occurred rapidly to produce stable 9,10-dimethylanthracene radical cation. The driving force dependence of the rate constants of electron transfer from anthracene derivatives to [(Bn-TPEN)MnIV(O)]2+ and [(Bn-TPEN)MnIV(O)-(Sc(OTf)3)2]2+ was well evaluated in light of the Marcus theory of electron transfer.

  6. Photoactive PDI-cobalt complex immobilized on reduced graphene oxide for photoelectrochemical water splitting.

    Balapanuru, Janardhan; Chiu, Gordon; Su, Chenliang; Zhou, Na; Hai, Zhu; Xu, Qing-Hua; Loh, Kian Ping


    We report the synthesis of a perylene derivative (perylene tetracarboxylic di(propyl imidazole), abbreviated as PDI) that is coordinated with Co(II) ions to form a coordination polymer [PDI-Co(Cl)2(H2O)2]n (abbreviated as PDI-Co). The PDI-Co complex combines the photoactivity of the perylene dye with the electrocatalytic activity of the "Co(II)" center for photoelectrochemical hydrogen evolution reaction (HER). To improve charge transfer interactions, the PDI-Co complex is immobilized on reduced graphene oxide (rGO) via noncovalent interactions to form the rGO-PDI-Co complex. The composite shows good performance in multiple cycle testing and the turnover number (TON vs Co(II)) of this hybrid material for hydrogen evolution reaction (754 after 5 h) is considerably higher than previously reported dye-sensitized cobalt-based catalysts.

  7. Oxidation of Cyclohexene with H202 Catalyzed by MCM-41 Supported Co(Il) Amino Acid Complex

    WANG RongMin; LOU JianFang; CAI YongFu; WANG YunPu; ZHANG ZhenLin; SONG PengFei; XIA ChunGu


    @@ Catalysis of oxidation of cyclohexene using zeolite supported transition metal complexes into a variety of products such as expoxide, carbonyl compounds, diols and oxidative cleavage products of C=C has received much attention primarily due to interest in selective and partial oxidations. A major advantage of this catalysis is the ease of separation, recyclobilicity, and site specificity in oxidative reactions. In this paper the catalyst Co(Ⅱ)-glu/ MCM-41 was prepared and its catalytic activity in selective oxidation of cyclohexene was also studied.

  8. A literature review of interaction of oxidized uranium species and uranium complexes with soluble organic matter

    Jennings, Joan K.; Leventhal, J.S.


    Organic material is commonly found associated with uranium ores in sandstone-type deposits. This review of the literature summarizes the classes and separations of naturally occurring organic material but the emphasis is on soluble organic species. The main class of materials of interest is humic substances which are high-molecular-weight complex molecules that are soluble in alkaline solution. These humic substances are able to solubilize (make soluble) minerals and also to complex [by ion exchange and (or) chelation] many cations. The natural process of soil formation results in both mineral decomposition and element complexing by organic species. Uranium in solution, such as ground water, can form many species with other elements or complexes present depending on Eh and pH. In natural systems (oxidizing Eh, pH 5-9) the uranium is usually present as a complex with hydroxide or carbonate. Thermodynamic data for these species are presented. Interacting metals and organic materials have been observed in nature and studied in the laboratory by many workers in diverse scientific disciplines. The results are not easily compared. Measurements of the degree of complexation are reported as equilibrium stability constant determinations. This type of research has been done for Mn, Fe, Cu, Zn, Pb, Ni, Co, Mg, Ca, Al, and to a limited degree for U. The use of Conditional Stability Constants has given quantitative results in some cases. The methods utilized in experiments and calculations are reviewed.

  9. The microglial NADPH oxidase complex as a source of oxidative stress in Alzheimer's disease

    Landreth Gary E


    Full Text Available Abstract Alzheimer's disease is the most common cause of dementia in the elderly, and manifests as progressive cognitive decline and profound neuronal loss. The principal neuropathological hallmarks of Alzheimer's disease are the senile plaques and the neurofibrillary tangles. The senile plaques are surrounded by activated microglia, which are largely responsible for the proinflammatory environment within the diseased brain. Microglia are the resident innate immune cells in the brain. In response to contact with fibrillar beta-amyloid, microglia secrete a diverse array of proinflammatory molecules. Evidence suggests that oxidative stress emanating from activated microglia contribute to the neuronal loss characteristic of this disease. The source of fibrillar beta-amyloid induced reactive oxygen species is primarily the microglial nicotinamide adenine dinucleotide phosphate (NADPH oxidase. The NADPH oxidase is a multicomponent enzyme complex that, upon activation, produces the highly reactive free radical superoxide. The cascade of intracellular signaling events leading to NADPH oxidase assembly and the subsequent release of superoxide in fibrillar beta-amyloid stimulated microglia has recently been elucidated. The induction of reactive oxygen species, as well as nitric oxide, from activated microglia can enhance the production of more potent free radicals such as peroxynitrite. The formation of peroxynitrite causes protein oxidation, lipid peroxidation and DNA damage, which ultimately lead to neuronal cell death. The elimination of beta-amyloid-induced oxidative damage through the inhibition of the NADPH oxidase represents an attractive therapeutic target for the treatment of Alzheimer's disease.

  10. Kinetics of oxidation of bilirubin and its protein complex by hydrogen peroxide in aqueous solutions

    Solomonov, A. V.; Rumyantsev, E. V.; Antina, E. V.


    A comparative study of oxidation reactions of bilirubin and its complex with albumin was carried out in aqueous solutions under the action of hydrogen peroxide and molecular oxygen at different pH values. Free radical oxidation of the pigment in both free and bound forms at pH 7.4 was shown not to lead to the formation of biliverdin, but to be associated with the decomposition of the tetrapyrrole chromophore into monopyrrolic products. The effective and true rate constants of the reactions under study were determined. It was assumed that one possible mechanism of the oxidation reaction is associated with the interaction of peroxyl radicals and protons of the NH groups of bilirubin molecules at the limiting stage with the formation of a highly reactive radical intermediate. The binding of bilirubin with albumin was found to result in a considerable reduction in the rate of the oxidation reaction associated with the kinetic manifestation of the protein protection effect. It was found that the autoxidation of bilirubin by molecular oxygen with the formation of biliverdin at the intermediate stage can be observed with an increase in the pH of solutions.

  11. Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

    Baron, Marco


    Gold(I) dicarbene complexes [Au2(MeIm-Y-ImMe)2](PF6)2(Y=CH2(1), (CH2)2(2), (CH2)4(4), MeIm=1-methylimidazol-2-ylidene) react with iodine to give the mixed-valence complex [Au(MeIm-CH2-ImMe)2AuI2](PF6)2(1 aI) and the gold(III) complexes [Au2I4(MeIm-Y-ImMe)2](PF6)2(2 cIand 4 cI). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes [Au2Cl4(MeIm-CH2-ImMe)2](PF6)2(1 cCl) and [Au2Cl4(MeIm-(CH2)2-ImMe)2](Cl)2(2 cCl-Cl) (as main product); remarkably in the case of complex 2, the X-ray molecular structure of the crystals also shows the presence of I-Au-Cl mixed-sphere coordination. The same type of coordination has been observed in the main product of the reaction of complexes 3 or 4 with ICl. The study of the reactivity towards the oxidative addition of halogens to a large series of dinuclear bis(dicarbene) gold(I) complexes has been extended and reviewed. The complexes react with Cl2, Br2and I2to give the successive formation of the mixed-valence gold(I)/gold(III) n aXand gold(III) n cX(excluding compound 1 cI) complexes. However, complex 3 affords with Cl2and Br2the gold(II) complex 3 bX[Au2X2(MeIm-(CH2)3-ImMe)2](PF6)2(X=Cl, Br), which is the predominant species over compound 3 cXeven in the presence of free halogen. The observed different relative stabilities of the oxidised complexes of compounds 1 and 3 have also been confirmed by DFT calculations. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Heterogeneous and Homogeneous Routes in Water Oxidation Catalysis Starting from Cu(II) Complexes with Tetraaza Macrocyclic Ligands.

    Prevedello, Andrea; Bazzan, Irene; Dalle Carbonare, Nicola; Giuliani, Angela; Bhardwaj, Sunil; Africh, Cristina; Cepek, Cinzia; Argazzi, Roberto; Bonchio, Marcella; Caramori, Stefano; Robert, Marc; Sartorel, Andrea


    Since the first report in 2012, molecular copper complexes have been proposed as efficient electrocatalysts for water oxidation reactions, carried out in alkaline/neutral aqueous media. However, in some cases the copper species have been recognized as precursors of an active copper oxide layer, electrodeposited onto the working electrode. Therefore, the question whether copper catalysis is molecular or not is particularly relevant in the field of water oxidation. In this study, we investigate the electrochemical activity of copper(II) complexes with two tetraaza macrocyclic ligands, distinguishing heterogeneous or homogeneous processes depending on the reaction media. In an alkaline aqueous solution, and upon application of an anodic bias to working electrodes, an active copper oxide layer is observed to electrodeposit at the electrode surface. Conversely, water oxidation in neutral aqueous buffers is not associated to formation of the copper oxide layer, and could be exploited to evaluate and optimize a molecular, homogeneous catalysis.

  13. Chromic anhydride-3, 5-dimethylpyrazole complex: an efficient reagent for oxidation of steroidal estrogens to 6-oxo-derivatives.

    Garza, G A; Rao, P N


    An efficient procedure for the oxidation of steroidal estrogens to the corresponding 6-oxo-derivatives is described. The oxidative process involves the use of 3,5-dimethylpyrazole-chromium trioxide complex at low temperature (-20 degrees). Under these conditions, only the 6-oxo-derivative and the unreacted starting material were obtained and the latter could be subjected to oxidation once again to obtain additional amount of 6-oxo-derivative.

  14. Electrocatalytic oxidation of methanol at platinum electrode modified with Eu-Fe cyanide-bridged binuclear complexes


    The electrocatalytic oxidation of methanol at the platinum electrode modified with Eu-Fe cyanide-bridged binuclear complexes (Eu-Fe film) was investigated for the first time by cyclic voltammetry.Compared with the bare platinum electrode,the results showed that the modified electrode had excellent electrocatalytic activity for the oxidation of methanol;the oxidation peak potential shifted more negatively and the peak current increased about twenty times.The electrooxidation of methanol at the modified el...

  15. A Ni-Fe Layered Double Hydroxide-Carbon Nanotube Complex for Water Oxidation

    Gong, Ming; Wang, Hailiang; Liang, Yongye; Wu, Justin Zachary; Zhou, Jigang; Wang, Jian; Regier, Tom; Wei, Fei; Dai, Hongjie


    Highly active, durable and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions including water splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel iron layered double hydroxide nanoplates on mildly oxidized multi-walled carbon nanotubes. Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-layered double hydroxide. The nanoplates were covalently attached to a network of nanotubes, affording excellent electrical wiring to the nanoplates. The ultra-thin Ni-Fe layered double hydroxide nanoplates/carbon nanotube complex was found to exhibit unusually high electro-catalytic activity and stability for oxygen evolution and outperformed commercial precious metal Ir catalysts.

  16. Organometallic Complexes Anchored to Conductive Carbon for Electrocatalytic Oxidation of Methane at Low Temperature.

    Joglekar, Madhura; Nguyen, Vinh; Pylypenko, Svitlana; Ngo, Chilan; Li, Quanning; O'Reilly, Matthew E; Gray, Tristan S; Hubbard, William A; Gunnoe, T Brent; Herring, Andrew M; Trewyn, Brian G


    Low-temperature direct methane fuel cells (DMEFCs) offer the opportunity to substantially improve the efficiency of energy production from natural gas. This study focuses on the development of well-defined platinum organometallic complexes covalently anchored to ordered mesoporous carbon (OMC) for electrochemical oxidation of methane in a proton exchange membrane fuel cell at 80 °C. A maximum normalized power of 403 μW/mg Pt was obtained, which was 5 times higher than the power obtained from a modern commercial catalyst and 2 orders of magnitude greater than that from a Pt black catalyst. The observed differences in catalytic activities for oxidation of methane are linked to the chemistry of the tethered catalysts, determined by X-ray photoelectron spectroscopy. The chemistry/activity relationships demonstrate a tangible path for the design of electrocatalytic systems for C-H bond activation that afford superior performance in DMEFC for potential commercial applications.

  17. Iron and its complexation by phenolic cellular metabolites: from oxidative stress to chemical weapons.

    Chobot, Vladimir; Hadacek, Franz


    Iron is a transition metal that forms chelates and complexes with various organic compounds, also with phenolic plant secondary metabolites. The ligands of iron affect the redox potential of iron. Electrons may be transferred either to hydroxyl radicals, hydrogen peroxide or molecular oxygen. In the first case, oxidative stress is decreased, in the latter two cases, oxidative stress is increased. This milieu-dependent mode of action may explain the non-linear mode of action of juglone and other secondary metabolites. Attention to this phenomenon may help to explain idiosyncratic and often nonlinear effects that result in biological assays. Current chemical assays are discussed that help to explore these aspects of redox chemistry.

  18. Water oxidation with molecularly defined iridium complexes: insights into homogeneous versus heterogeneous catalysis.

    Junge, Henrik; Marquet, Nicolas; Kammer, Anja; Denurra, Stefania; Bauer, Matthias; Wohlrab, Sebastian; Gärtner, Felix; Pohl, Marga-Martina; Spannenberg, Anke; Gladiali, Serafino; Beller, Matthias


    Molecularly defined Ir complexes and different samples of supported IrO(2) nanoparticles have been tested and compared in the catalytic water oxidation with cerium ammonium nitrate (CAN) as the oxidant. By comparing the activity of nano-scaled supported IrO(2) particles to the one of organometallic complexes it is shown that the overall activity of the homogeneous Ir precursors is defined by both the formation of the homogeneous active species and its conversion to Ir(IV)-oxo nanoparticles. In the first phase of the reaction the activity is dominated by the homogeneous active species. With increasing reaction time, the influence of nano-sized Ir-oxo particles becomes more evident. Notably, the different conversion rates of the homogeneous precursor into the active species as well as the conversion into Ir-oxo nanoparticles and the different particle sizes have a significant influence on the overall activity. In addition to the homogeneous systems, IrO(2)@MCM-41 has also been synthesized, which contains stabilized nanoparticles of between 1 and 3 nm in size. This latter system shows a similar activity to IrCl(3)⋅xH(2)O and complexes 4 and 5. Mechanistic insights were obtained by in situ X-ray absorption spectroscopy and scanning transmission electron microscopy.

  19. Effect of Photo-Oxidation on Energy Transfer in Light Harvesting Complex (LH2) from Rhodobacter Sphaeroides 601

    LIU Kang-Jun; LIU Wei-Min; YAN Yong-Li; DONG Zhi-Wei; LIU Yuan; XU Chun-He; QIAN Shi-Xiong


    @@ We study the photo-oxidation of bacteriochlorophylls (BChls) in peripheral light harvesting complexes (LH2) from rhodobacter sphaeroides by using the steady absorption and the femtosecond pump-probe measurement, to realize the detailed dynamics of LH2 in the presence of photo-oxidation.

  20. Pd-Cu-M (M = Y, Ti, Zr, V, Nb, and Ni) Alloys for the Hydrogen Separation Membrane.

    Nayebossadri, Shahrouz; Speight, John D; Book, David


    Self-supported fcc Pd-Cu-M (M = Y, Ti, Zr, V, Nb, and Ni) alloys were studied as potential hydrogen purification membranes. The effects of small additions (1-2.6 at. %) of these elements on the structure, hydrogen solubility, diffusivity, and permeability were examined. Structural analyses by X-ray diffraction (XRD) showed the fcc phase for all alloys with induced textures from cold rolling. Heat treatment at 650 °C for 96 h led to the reorientation in all alloys except the Pd-Cu-Zr alloy, exhibiting the possibility to enhance the structural stability by Zr addition. Hydrogen solubility was almost doubled in the ternary alloys containing Y and Zr compared to Pd65.1Cu34.9 alloy at 300 °C. It was noted that hydrogen diffusivity is decreased upon additions of these elements compared to the Pd65.1Cu34.9 alloy, with the Pd-Cu-Zr alloy showing the lowest hydrogen diffusivity. However, the comparable hydrogen permeability of the Pd-Cu-Zr alloy with the corresponding binary alloy, as well as its highest hydrogen permeability among the studied ternary alloys at temperatures higher than 300 °C, suggested that hydrogen permeation of these alloys within the fcc phase is mainly dominated by hydrogen solubility. Hydrogen flux variations of all ternary alloys were studied and compared with the Pd65.1Cu34.9 alloy under 1000 ppm of H2S + H2 feed gas. Pd-Cu-Zr alloy showed superior resistance to the sulfur poisoning probably due to the less favorable H2S-surface interaction and more importantly slower rate of bulk sulfidation as a result of improved structural stability upon Zr addition. Therefore, Pd-Cu-Zr alloys may offer new potential hydrogen purification membranes with improved chemical stability and hydrogen permeation compared to the binary fcc Pd-Cu alloys.

  1. Synergistically Enhanced Optical Limiting Property of Graphene Oxide Hybrid Materials Functionalized with Pt Complexes.

    Liu, Rui; Hu, Jinyang; Zhu, Senqiang; Lu, Jiapeng; Zhu, Hongjun


    Recently, graphene-based materials have become well-known nonlinear optical materials for the potential application of laser protection. Two new graphene oxide-platinum  complex (GO-Pt) hybrid materials (GO-Pt-1, GO-Pt-2) have been fabricated through covalent modification and electrostatic adsorption of different Pt complexes with GO. The structural and photophysical properties of the resultant hybrid materials were studied. The nonlinear optical properties and optical power limiting (OPL) performance of Pt complexes, GO, and GO-Pt hybrid materials were investigated by using Z-scan measurements at 532 nm. At the same transmittance, the results illustrate that functionalization of GO makes GO-Pt hybrid materials possess better nonlinear optical properties and OPL performance than individual Pt complexes and GO due to a combination of nonlinear scattering, nonlinear absorption, and photoinduced electron and energy transfer between GO and Pt complex moieties. Furthermore, the nonlinear optics and OPL performance of GO-Pt-2 are better than those of GO-Pt-1, due to not only the excellent optical limiting of Pt-2 and more molecules per area of GO but also the way of combination of Pt-2 and GO.

  2. Luminescent Iridium(III) Complex Labeled DNA for Graphene Oxide-Based Biosensors.

    Zhao, Qingcheng; Zhou, Yuyang; Li, Yingying; Gu, Wei; Zhang, Qi; Liu, Jian


    There has been growing interest in utilizing highly photostable iridium(III) complexes as new luminescent probes for biotechnology and life science. Herein, iridium(III) complex with carboxyl group was synthesized and activated with N-hydroxysuccinimide, followed by tagging to the amino terminate of single-stranded DNA (ssDNA). The Ir-ssDNA probe was further combined with graphene oxide (GO) nanosheets to develop a GO-based biosensor for target ssDNA detection. The quenching efficiency of GO, and the photostability of iridium(III) complex and GO-Ir-ssDNA biosensor, were also investigated. On the basis of the high luminescence quenching efficiency of GO toward iridium(III) complex, the GO-Ir-ssDNA biosensor exhibited minimal background signals, while strong emission was observed when Ir-ssDNA desorbed from GO nanosheets and formed a double helix with the specific target, leading to a high signal-to-background ratio. Moreover, it was found that luminescent intensities of iridium(III) complex and GO-Ir-ssDNA biosensor were around 15 and 3 times higher than those of the traditional carboxyl fluorescein (FAM) dye and the GO-FAM-ssDNA biosensor after UV irradiation, respectively. Our study suggested the sensitive and selective Ir-ssDNA probe was suitable for the development of highly photostable GO-based detection platforms, showing promise for application beyond the OLED (organic light emitting diode) area.

  3. Photodegradation of orange I in the heterogeneous iron oxide-oxalate complex system under UVA irradiation

    Lei, Jing [Faculty of Agriculture, Guangxi University, Nanning 630005 (China); Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environment and Soil Sciences, Guangzhou 510650 (China); Liu Chengshuai [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environment and Soil Sciences, Guangzhou 510650 (China); Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Li Fangbai [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environment and Soil Sciences, Guangzhou 510650 (China)]. E-mail:; Li Xiaomin [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environment and Soil Sciences, Guangzhou 510650 (China); Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Zhou Shungui [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environment and Soil Sciences, Guangzhou 510650 (China); Liu Tongxu [Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environment and Soil Sciences, Guangzhou 510650 (China); Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Gu Minghua [Faculty of Agriculture, Guangxi University, Nanning 630005 (China); Wu Qitang [College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642 (China)


    To understand the photodegradation of azo dyes in natural aquatic environment, a novel photo-Fenton-like system, the heterogeneous iron oxide-oxalate complex system was set up with the existence of iron oxides and oxalate. Five iron oxides, including {gamma}-FeOOH, IO-250, IO-320, IO-420 and IO-520, were prepared and their adsorption capacity was investigated in the dark. The results showed that the saturated adsorption amount ({gamma}{sub max}) was ranked the order of IO-250>IO-320>{gamma}-FeOOH>IO-420>IO-520 and the adsorption equilibrium constant (K{sub a}) followed the order of IO-250>IO-520>{gamma}-FeOOH>IO-420>IO-320. The effect of initial pH value, the initial concentrations of oxalate and orange I on the photodegradation of orange I were also investigated in different iron oxide-oxalate systems. The results showed that the photodegradation of orange I under UVA irradiation could be enhanced greatly in the presence of oxalate. And the optimal oxalate concentrations (C{sub ox}{sup 0}) for {gamma}-FeOOH, IO-250, IO-320, IO-420 and IO-520 were 1.8, 1.6, 3.5, 3.0 and 0.8mM, respectively. The photodegradation of orange I in the presence of optimal C{sub ox}{sup 0} was ranked as the order of {gamma}-FeOOH>IO-250>IO-320>IO-420>IO-520. The optimal range of initial pH was at about 3-4. The first-order kinetic constant for the degradation of orange I decreased with the increase in the initial concentration of orange I. Furthermore, the variation of pH, the concentrations of Fe{sup 3+} and Fe{sup 2+} during the photoreaction were also strongly dependent on the C{sub ox}{sup 0} and iron oxides.

  4. Photodegradation of orange I in the heterogeneous iron oxide-oxalate complex system under UVA irradiation.

    Lei, Jing; Liu, Chengshuai; Li, Fangbai; Li, Xiaomin; Zhou, Shungui; Liu, Tongxu; Gu, Minghua; Wu, Qitang


    To understand the photodegradation of azo dyes in natural aquatic environment, a novel photo-Fenton-like system, the heterogeneous iron oxide-oxalate complex system was set up with the existence of iron oxides and oxalate. Five iron oxides, including gamma-FeOOH, IO-250, IO-320, IO-420 and IO-520, were prepared and their adsorption capacity was investigated in the dark. The results showed that the saturated adsorption amount (gamma(max)) was ranked the order of IO-250 > IO-320 > gamma-FeOOH > IO-420 > IO-520 and the adsorption equilibrium constant (Ka) followed the order of IO-250 > IO-520 > gamma-FeOOH > IO-420 > IO-320. The effect of initial pH value, the initial concentrations of oxalate and orange I on the photodegradation of orange I were also investigated in different iron oxide-oxalate systems. The results showed that the photodegradation of orange I under UVA irradiation could be enhanced greatly in the presence of oxalate. And the optimal oxalate concentrations (C(ox)0) for gamma-FeOOH, IO-250, IO-320, IO-420 and IO-520 were 1.8, 1.6, 3.5, 3.0 and 0.8 mM, respectively. The photodegradation of orange I in the presence of optimal C(ox)0 was ranked as the order of gamma-FeOOH > IO-250 > IO-320 > IO-420 > IO-520. The optimal range of initial pH was at about 3-4. The first-order kinetic constant for the degradation of orange I decreased with the increase in the initial concentration of orange I. Furthermore, the variation of pH, the concentrations of Fe3+ and Fe2+ during the photoreaction were also strongly dependent on the C(ox)0 and iron oxides.

  5. Atomic Resolution Imaging of Nanoscale Structural Ordering in a Complex Metal Oxide Catalyst

    Zhu, Yihan


    The determination of the atomic structure of a functional material is crucial to understanding its "structure-to-property" relationship (e.g., the active sites in a catalyst), which is however challenging if the structure possesses complex inhomogeneities. Here, we report an atomic structure study of an important MoVTeO complex metal oxide catalyst that is potentially useful for the industrially relevant propane-based BP/SOHIO process. We combined aberration-corrected scanning transmission electron microscopy with synchrotron powder X-ray crystallography to explore the structure at both nanoscopic and macroscopic scales. At the nanoscopic scale, this material exhibits structural and compositional order within nanosized "domains", while the domains show disordered distribution at the macroscopic scale. We proposed that the intradomain compositional ordering and the interdomain electric dipolar interaction synergistically induce the displacement of Te atoms in the Mo-V-O channels, which determines the geometry of the multifunctional metal oxo-active sites.

  6. Biomimetic oxidations using transition metal complex catalysts; Sen`i kinzoku sakutai wo mochiiru seigoseigata sanka shokubai hanno

    Murahashi, S. [Osaka University, Osaka (Japan). Faculty of Engineering Science


    Simulation of the functions of flavoenzyme and cytochrome P-450 with transition metal complex catalysts led to the discovery of biomimetic catalytic oxidation. The first section highlights the catalytic oxidation of secondary amides to nitrones by simulation of flavoenzymes. The second section is the simulation of the function of cytochrome P-450 with low valent ruthenium complexes and peroxides. Biomimetic ruthenium-paralyzed oxidations of tertiary amides, amides, {beta}-lactams, alkenes, and alkanes can be performed selectively under mild conditions. These general approaches provide highly useful strategies for synthesis of fine chemicals and biologically active compounds. 15 refs.

  7. pH Responsive and Oxidation Resistant Wet Adhesive based on Reversible Catechol-Boronate Complexation.

    Narkar, Ameya R; Barker, Brett; Clisch, Matthew; Jiang, Jingfeng; Lee, Bruce P


    A smart adhesive capable of binding to a wetted surface was prepared by copolymerizing dopamine methacrylamide (DMA) and 3-acrylamido phenylboronic acid (AAPBA). pH was used to control the oxidation state and the adhesive property of the catechol side chain of DMA and to trigger the catechol-boronate complexation. FTIR spectroscopy confirmed the formation of the complex at pH 9, which was not present at pH 3. The formation of the catechol-boronate complex increased the cross-linking density of the adhesive network. Most notably, the loss modulus values of the adhesive were more than an order of magnitude higher for adhesive incubated at pH 9 when compared to those measured at pH 3. This drastic increase in the viscous dissipation property is attributed to the introduction of reversible complexation into the adhesive network. Based on the Johnson Kendall Roberts (JKR) contact mechanics test, adhesive containing both DMA and AAPBA demonstrated strong interfacial binding properties (work of adhesion (Wadh) = 2000 mJ/m(2)) to borosilicate glass wetted with an acidic solution (pH 3). When the pH was increased to 9, Wadh values (180 mJ/m(2)) decreased by more than an order of magnitude. During successive contact cycles, the adhesive demonstrated the capability to transition reversibly between its adhesive and nonadhesive states with changing pH. Adhesive containing only DMA responded slowly to repeated changes in pH and became progressively oxidized without the protection of boronic acid. Although adhesive containing only AAPBA also demonstrated strong wet adhesion (Wadh ∼ 500 mJ/m(2)), its adhesive properties were not pH responsive. Both DMA and AAPBA are required to fabricate a smart adhesive with tunable and reversible adhesive properties.

  8. Oscillations and complex mechanisms: O/sub 2/ oxidation of benzaldehyde

    Roelofs, M.G.; Wasserman, E.; Jensen, J.H.


    The oxidation of benzaldehyde catalyzed by cobalt and bromine is an oscillating reaction in which the concentrations of Co(III) and of dissolved oxygen vary periodically with time. A mechanistic model is proposed in which the reaction alternates between two stages. In stage I the dissolved oxygen concentration is appreciable and benzoyl radicals combine with oxygen, ultimately oxidizing Co(II) to Co(III). In stage II dissolved oxygen is depleted, and benzoyl radicals are oxidized by Co(III). The model gives satisfactory agreement with a number of qualitative and quantitative features. These include the composition of the steady states and the amplitude and period of oscillation for different concentrations of cobalt, bromide, and benzaldehyde. Specific measurements were also made of the kinetics of the reduction of cobalt(III) by mixtures of benzaldehyde and sodium bromide, the stability of a cobalt-bromide complex, and the consumption of /sup 18/O/sub 2/. This last study demonstrates the presence of two major pathways to benzoic acid which differ in the source of oxygen.

  9. Mechanism of Water Oxidation Catalyzed by a Dinuclear Ruthenium Complex Bridged by Anthraquinone

    Tohru Wada


    Full Text Available We synthesized 1,8-bis(2,2′:6′,2″-terpyrid-4′-ylanthraquinone (btpyaq as a new dimerizing ligand and determined its single crystal structure by X-ray analysis. The dinuclear Ruthenium complex [Ru2(µ-Cl(bpy2(btpyaq](BF43 ([3](BF43, bpy = 2,2′-bipyridine was used as a catalyst for water oxidation to oxygen with (NH42[Ce(NO36] as the oxidant (turnover numbers = 248. The initial reaction rate of oxygen evolution was directly proportional to the concentration of the catalyst and independent of the oxidant concentration. The cyclic voltammogram of [3](BF43 in water at pH 1.3 showed an irreversible catalytic current above +1.6 V (vs. SCE, with two quasi-reversible waves and one irreversible wave at E1/2 = +0.62, +0.82 V, and Epa = +1.13 V, respectively. UV-vis and Raman spectra of [3](BF43 with controlled-potential electrolysis at +1.40 V revealed that [Ru(IV=O O=Ru(IV]4+ is stable under electrolysis conditions. [Ru(III, Ru(II] species are recovered after dissociation of an oxygen molecule from the active species in the catalytic cycle. These results clearly indicate that an O–O bond is formed via [Ru(V=O O=Ru(IV]5+.

  10. Single-molecule in vivo imaging of bacterial respiratory complexes indicates delocalized oxidative phosphorylation.

    Llorente-Garcia, Isabel; Lenn, Tchern; Erhardt, Heiko; Harriman, Oliver L; Liu, Lu-Ning; Robson, Alex; Chiu, Sheng-Wen; Matthews, Sarah; Willis, Nicky J; Bray, Christopher D; Lee, Sang-Hyuk; Shin, Jae Yen; Bustamante, Carlos; Liphardt, Jan; Friedrich, Thorsten; Mullineaux, Conrad W; Leake, Mark C


    Chemiosmotic energy coupling through oxidative phosphorylation (OXPHOS) is crucial to life, requiring coordinated enzymes whose membrane organization and dynamics are poorly understood. We quantitatively explore localization, stoichiometry, and dynamics of key OXPHOS complexes, functionally fluorescent protein-tagged, in Escherichia coli using low-angle fluorescence and superresolution microscopy, applying single-molecule analysis and novel nanoscale co-localization measurements. Mobile 100-200nm membrane domains containing tens to hundreds of complexes are indicated. Central to our results is that domains of different functional OXPHOS complexes do not co-localize, but ubiquinone diffusion in the membrane is rapid and long-range, consistent with a mobile carrier shuttling electrons between islands of different complexes. Our results categorically demonstrate that electron transport and proton circuitry in this model bacterium are spatially delocalized over the cell membrane, in stark contrast to mitochondrial bioenergetic supercomplexes. Different organisms use radically different strategies for OXPHOS membrane organization, likely depending on the stability of their environment. Copyright © 2014. Published by Elsevier B.V.

  11. Novel polystyrene-anchored zinc complex:Efficient catalyst for phenol oxidation

    Alekha Kumar Sutar a; Yasobanta Das ab; Sasmita Pattnaik a; Anita Routaray a; Nibedita Nath a; Prasanta Rath b; Tungabidya Maharana c


    The novel recyclable free -ONNO- tetradentate Schiff base ligand N,N′-bis(2-hydroxy-3-methox-ybenzaldehyde)4-methylbenzene-1,2-diamine (3-MOBdMBn) was synthesized. Complexation of this ligand with zinc (3-MOBdMBn-Zn) was performed, and the catalytic activity of the complex was evaluated. The polymer-supported analog of this complex (P-3-MOBdMBn-Zn) was synthesized, and its catalytic activity was studied. These free and polymer-anchored zinc complexes were prepared by the reactions of metal solutions with one molar equivalent of unsupported 3-MOBdMBn or P-3-MOBdMBn in methanol under nitrogen. The catalytic activity of 3-MOBdMBn-Zn and P-3-MOBdMBn-Zn was evaluated in phenol oxidation. The activity of P-3-MOBdMBn-Zn was signif-icantly affected by the polymer support, and the rate of phenol conversion was around 50%for polystyrene-supported 3-MOBdMBn. The experimental results indicated that the reaction rate was affected by the polymer support, and the rate of phenol conversion was 1.64 μmol/(L·s) in the presence of polystyrene-supported 3-MOBdMBn.

  12. Effects of oxidation on redox and cytotoxic properties of copper complex of Aβ1-16 peptide.

    Ramteke, S N; Walke, G R; Joshi, B N; Rapole, S; Kulkarni, P P


    The effect of oxidation on redox and cytotoxic properties of copper complex of amyloid beta (Aβ) peptide was studied by gamma radiolysis. The oxidation of Aβ1-16 and Aβ1-16/Cu(II) complex was carried out using hydroxyl ((•)OH) radicals produced by gamma radiolysis and the products were analyzed using mass spectrometry. The presence of Cu(II) was found to enhance the oxidation of Aβ1-16 peptide. The oxidation of residues Asp1, His6, and His13 was enhanced due to their involvement in copper binding. The oxidation of His residues of Aβ1-16 peptide, which are chiefly responsible for copper binding, resulted in altered redox properties and subsequently in higher cytotoxicity of the Aβ1-16 peptide in SH-SY5Y cells.

  13. Mononuclear copper(II) nitrato complexes with methyl-substituted 4-nitropyridine N-oxide. Physicochemical and cytotoxic characteristics.

    Puszko, Aniela; Krojcer, Anna; Pełczynska, Marzena; Wietrzyk, Joanna; Cieślak-Golonka, Maria; Jezierska, Julia; Adach, Anna; Kubiak, Maria


    Three new complexes, products of the interaction of Cu(NO(3))(2) and methyl-substituted 4-nitropyridine N-oxides were synthesized and characterized by elemental analysis, magnetic, spectroscopic (IR, FIR and EPR), thermal and X-ray methods. The complexes (magnetic moments 1.70-1.81 BM at 300K) of general formula [Cu(H(2)O)(NO(3))(2)L(2)], L=2-methyl-4-nitropyridine N-oxide and [Cu(NO(3))(2) L'(2)], where L'=2,6-dimethyl- and 2,3,6-trimethyl-4-nitropyridine N-oxide were obtained. The compounds were unstable upon dissolution. The X-ray single crystal structure of Cu(II) complex with 2,6-dimethyl-4-nitropyridine N-oxide was determined and analysed. The compounds and free ligands were tested in vitro on the cytotoxic activity against MCF-7 and SW-707 human cancer cell lines. The complexes with 4-nitropyridine N-oxide (a reference) and 2-methyl-4-nitropyridine N-oxide show a significant anti-proliferative activity against studied cell lines. A reciprocal relationship between the activity and the number of methyl groups was observed. Both ligands and complexes are cytotoxic active but to the different cell lines.


    ZHAO Ganqing; XIE Jimin; LU Xiaoqing; SUN Lu


    The polystyrene supported phenylalanine Schiff base complex of Mn(Ⅱ)(PS-Sal-Phe-Mn)was prepared with chloromethylated styrene polymer beads, 2,4-dihydroxybenzaldehyde,L-phenylalanine and manganese(Ⅱ)acetate tetrahyrate., The polymeric ligand and the complex were characterized by FT-IR,, small area X-ray photoelectron spectroscopy(XPS), and ICP-AES. In the presence of the manganese complex, cyclohexene(1)was effectively oxidized by molecular oxygen without reductant. The major products of the reaction were 2-cyclohexen-1-ol(2),2-cyclohexen-1-one(3)and 2-cyclohexen-1- hydroperoxide(4), which was different with typical oxidation of cyclohexene. The influence of reaction temperature and additive for oxidation had been studied. The selectivity of 2-cyclohexen-l-hydroperoxide varied with reaction time and different additives. The mechanism of cyclohexene oxidation had also been discussed.

  15. Acid-base and catalytic properties of the products of oxidative thermolysis of double complex compounds

    Pechenyuk, S. I.; Semushina, Yu. P.; Kuz'mich, L. F.; Ivanov, Yu. V.


    Acid-base properties of the products of thermal decomposition of [M(A)6] x; [M1(L)6] y (where M is Co, Cr, Cu, Ni; M1 is Fe, Cr, Co; A is NH3, 1/2 en, 1/2 pn, CO(NH2)2; and L is CN, 1/2C2O4) binary complexes in air and their catalytic properties in the oxidation reaction of ethanol with atmospheric oxygen are studied. It is found that these thermolysis products are mixed oxides of the central atoms of complexes characterized by pH values of the zero charge point in the region of 4-9, OH-group sorption limits from 1 × 10-4 to 4.5 × 10-4 g-eq/g, OH-group surface concentrations of 10-50 nm-2 in 0.1 M NaCl solutions, and S sp from 3 to 95 m2/g. Their catalytic activity is estimated from the apparent rate constant of the conversion of ethanol in CO2. The values of constants are (1-6.5) × 10-5 s-1, depending on the gas flow rate and the S sp value.

  16. Bimetallic oxamato complexes synthesized into mesoporous matrix as precursor to tunable nanosized oxide

    Kalinke, Lucas H.G. [Instituto de Química, Universidade Federal de Goiás—UFG, Goiânia, GO 74001-970 (Brazil); Instituto Federal de Goiás—IFG, Anápolis, GO (Brazil); Stumpf, Humberto O. [Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais—UFMG, Belo Horizonte, MG (Brazil); Mazali, Italo O. [Instituto de Química, Universidade Estadual de Campinas—UNICAMP, Campinas, SP (Brazil); Cangussu, Danielle, E-mail: [Instituto de Química, Universidade Federal de Goiás—UFG, Goiânia, GO 74001-970 (Brazil)


    Highlights: • The bimetallic oxamato complexes as single-source precursor. • We prepared into a porous silica glass tunable nanosized oxide powders. • X-ray diffraction shows the formation of CeO{sub 2}/CuO and spinel cobaltite. • The different number of IDC allows control of the nanoparticle size. - Abstract: The bimetallic complexes were employed to prepare into a porous silica glass tunable nanosized oxide powders through the single source precursor (SSP) method. These materials were prepared by first anchoring of [Cu(opba)]{sup 2−} [opba = ortho-phenylenebis(oxamato)], second by reaction in situ with second metal [Co(II) or Ce(III)] and followed by a thermal treatment. The different number of impregnation–decomposition cycles (IDC) allows control of the nanoparticle size. X-ray diffraction shows the formation of mixture CeO{sub 2}–CuO and spinel copper cobaltite. Raman spectroscopy confirmed the formation of such phases. Transmission electron microscopy images revealed that spinel cobaltite particles (8 IDC) present a mean size of about 9 nm, whereas for the CeO{sub 2}–CuO phase the particle diameters are 4 nm (2 IDC) and 8 nm (6 IDC). For CeO{sub 2}–CuO the diffuse reflectance spectroscopy indicates a consistent red shift in band gap from 3.41 to 2.87 eV with increasing of particle size due to quantum confinement effect.

  17. Versatile tuning of supramolecular hydrogels through metal complexation of oxidation-resistant catechol-inspired ligands.

    Menyo, Matthew S; Hawker, Craig J; Waite, J Herbert


    The mussel byssal cuticle employs DOPA-Fe(3+) complexation to provide strong, yet reversible crosslinking. Synthetic constructs employing this design motif based on catechol units are plagued by oxidation-driven degradation of the catechol units and the requirement for highly alkaline pH conditions leading to decreased performance and loss of supramolecular properties. Herein, a platform based on a 4-arm poly(ethylene glycol) hydrogel system is used to explore the utility of DOPA analogues such as the parent catechol and derivatives, 4-nitrocatechol (nCat) and 3-hydroxy-4-pyridinonone (HOPO), as structural crosslinking agents upon complexation with metal ions. HOPO moieties are found to hold particular promise, as robust gelation with Fe(3+) occurs at physiological pH and is found to be largely resistant to oxidative degradation. Gelation is also shown to be triggered by other biorelevant metal ions such as Al(3+), Ga(3+) and Cu(2+) which allows for tuning of the release and dissolution profiles with potential application as injectable delivery systems.

  18. Coordination Complexes as Catalysts: The Oxidation of Anthracene by Hydrogen Peroxide in the Presence of VO(acac)[subscript 2

    Charleton, Kimberly D. M.; Prokopchuk, Ernest M.


    A laboratory experiment aimed at students who are studying coordination chemistry of transition-metal complexes is described. A simple vanadyl acetylacetonate complex can be used as a catalyst in the hydrogen peroxide oxidation of anthracene to produce anthraquinone. The reaction can be performed under a variety of reaction conditions, ideally by…

  19. Preparation and characterization of Ce1-xFexO2 complex oxides and its catalytic activity for methane selective oxidation

    LI Kongzhai; WANG Hua; WEI Yonggang; LIU Mingchun


    A series of Ce1-xFexO2 (x=0, 0.2, 0.4, 0.6, 0.8, 1) complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.4O2 exhibited the best activity, which converted 94.52% of CH4 at 900 °C.

  20. Oxidative metabolism and muscle biochemical profile of polo horses supplemented with an ADE vitamin complex

    Rebeca A. Weigel


    Full Text Available Horses used for the game of polo experience abrupt and frequent changes in exercise intensity. To meet this variable energy demand, the horses use both aerobic and anaerobic pathways in varying proportions and intensities. In this context, there must be a balance between the formation of reactive oxygen species (ROS and the action of antioxidants to prevent oxidative stress and its consequences. The effect of supplementation with an ADE vitamin complex on oxidative metabolism was evaluated in 18 crossbred horses randomly divided between a treated group (TG and a control group (CG. The TG animals received the ADE vitamin complex (1mL/50 kg of body weight by deep intramuscular injection at 30 and 15 days before the game. The CG horses received 10ml of saline by the same administration route and schedule. During the polo match, the animals played for a total of 7.5 min. Blood samples were collected on the same days as the treatments were administered, and immediately before and at 15, 90 and 180 minutes after the game. The concentrations of creatine phosphokinase (CK, lactate dehydrogenase (LDH, lactate, glucose, aspartate aminotransferase (AST, glutathione (GSH, superoxide dismutase (SOD and malondialdehyde (MDA were measured in the blood samples. After the game, the TG demonstrated higher levels of AST, lactate and glucose than the CG, suggesting more efficient energy use by the treated animals. The higher GSH and lower lactate levels in the TG before the game suggest the presence of a greater antioxidant supply in the treated animals. The maintenance of the MDA levels indicates that neither of the groups exhibited oxidative stress.

  1. Manganese Complexes: Diverse Metabolic Routes to Oxidative Stress Resistance in Prokaryotes and Yeast


    Abstract Significance: Antioxidant enzymes are thought to provide critical protection to cells against reactive oxygen species (ROS). However, many organisms can fully compensate for the loss of such enzymatic defenses by accumulating metabolites and Mn2+, which can form catalytic Mn-antioxidants. Accumulated metabolites can direct reactivity of Mn2+ with superoxide and specifically shield proteins from oxidative damage. Recent Advances: There is mounting evidence that Mn-Pi (orthophosphate) complexes act as potent scavengers of superoxide in all three branches of life. Moreover, it is evident that Mn2+ in complexes with carbonates, peptides, nucleosides, and organic acids can also form catalytic Mn-antioxidants, pointing to diverse metabolic routes to oxidative stress resistance. Critical Issues: What conditions favor utility of Mn-metabolites versus enzymatic means for removing ROS? Mn2+-metabolite defenses are critical for preserving the activity of repair enzymes in Deinococcus radiodurans exposed to intense radiation stress, and in Lactobacillus plantarum, which lacks antioxidant enzymes. In other microorganisms, Mn-antioxidants can serve as an auxiliary protection when enzymatic antioxidants are insufficient or fail. These findings of a critical role of Mn-antioxidants in the survival of prokaryotes under oxidative stress parallel the trends developing for the simple eukaryote Saccharomyces cerevisiae. Future Directions: Phosphates, peptides and organic acids are just a snapshot of the types of anionic metabolites that promote such reactivity of Mn2+. Their probable roles in pathogen defense against the host immune response and in ROS-mediated signaling pathways are also areas that are worthy of serious investigation. Moreover, it is clear that these protective chemical processes can be harnessed for practical purposes. Antioxid. Redox Signal. 19, 933–944. PMID:23249283

  2. Synthesis, characterization, and activity of yttrium(III) nitrate complexes bearing tripodal phosphine oxide and mixed phosphine-phosphine oxide ligands.

    Sues, Peter E; Lough, Alan J; Morris, Robert H


    A series of four tripodal phosphine oxide ligands, (OPR(2))(2)CHCH(2)POR(2) (1a-1d), and four mixed phosphine-phosphine oxide ligands, (OPR(2))(2)CHCH(2)PR(2) (3a-3d), were synthesized and coordinated to yttrium to produce Y(NO(3))(3)[(OPR(2))(2)CHCH(2)POR(2)] (2a-2d) and Y(NO(3))(3)[(OPR(2))(2)CHCH(2)PR(2)](OPPh(3)) (4a-4d) complexes. The previously reported ligand 1a and unknown phosphine oxide ligands 1b-1d were generated in an unprecedented trisubstitution reaction of bromoacetaldehyde diethyl acetal, while the novel partially reduced ligands 3a-3d were synthesized from 1a-1d according to a known literature protocol for the selective monoreduction of bisphosphine oxides. The neutral yttrium complexes 2a-2d are nine-coordinate and display a tricapped trigonal-prismatic geometry. Complexes 4a-4d are also neutral, nine-coordinate species and have a pendant phosphine functionality, which provides the potential to form bimetallic early-late transition-metal complexes. Additionally, yttrium complexes 2a-2d were activated with base and tested for the ring-opening polymerization of ε-caprolactone, but the results showed that base by itself was significantly more effective than the yttrium species investigated.

  3. Bonding and Electronic Properties of Linear Diethynyl Oligothienoacene-Bridged Diruthenium Complexes and Their Oxidized Forms.

    Ou, Ya-Ping; Zhang, Jing; Zhang, Ming-Xing; Zhang, Fuxing; Kuang, Daizhi; Hartl, František; Liu, Sheng Hua


    A series of five diruthenium diethynyl complexes based on α,β-fused oligothienoacenes in the core of the bridging ligands [{Ru(dppe)Cp*}2(μ-C≡C-L-C≡C)] [dppe = 1,2-bis(diphenylphosphino)ethane, Cp* = η(5)-C5Me5; L = thieno[3,2-b]thiophene (4), thieno[2,3-b]thiophene (5), 3,4-dimethylthieno[2,3-b]thiophene (6), dithieno[3,2-b:2',3'-d]thiophene (7), and thieno[3,2-b]thieno[2',3':4,5]thieno[2,3-d]thiophene (8)] have been synthesized and fully characterized electrochemically and spectroscopically. Elongation of the redox noninnocent oligothienoacene bridge core causes a smaller potential difference between the initial two anodic steps, not seen for free dialkyl oligothienoacenes, and increased positive charge delocalization over the conjugated bridge backbone. The highest occupied molecular orbital of the parent complexes resides predominantly on the oligothienoacene core, with strong participation of the ethynyl linkers and slightly smaller contribution from the metallic termini. This bonding character makes the initial one-electron oxidation symmetrical, as revealed by combined voltammetric and spectroscopic (IR, UV-vis-near-IR, and electron paramagnetic resonance) methods as well as density functional theory (DFT) and time-dependent DFT calculations of truncated and selected nontruncated models of the studied series. The remarkable gradual appearance of two C≡C stretching absorptions in the IR spectra of the monocationic diethynyl complexes is ascribed to increasing vibronic coupling of the IR-forbidden νs(C≡C) mode of the oxidized -[C≡C-core-C≡C](+)- bridge with a low-lying π-π*(intrabridge)/metal-to-ligand charge-transfer electronic transition in the near-to-mid-IR spectral region.

  4. Spontaneous Tl(I)-to-Tl(III) oxidation in dynamic heterobimetallic Hg(II)/Tl(I) porphyrin complexes.

    Ndoyom, Victoria; Fusaro, Luca; Roisnel, Thierry; Le Gac, Stéphane; Boitrel, Bernard


    Strapped heterobimetallic Hg(II)/Tl(I) porphyrin complexes, with both metal ions bridged by the N-core in a dynamic way, undergo spontaneous Tl(I)-to-Tl(III) oxidation leading to a mono-Tl(III) complex and a mixed valence Tl(I)/Tl(III) bimetallic complex. It provides a new opportunity to tune metal ion translocations in bimetallic porphyrin systems.

  5. Distribution of manganese species in an oxidative dimerization reaction of a bis-terpyridine mononuclear manganese (II) complex and their heterogeneous water oxidation activities.

    Takahashi, Kosuke; Sato, Taisei; Yamazaki, Hirosato; Yagi, Masayuki


    Heterogeneous water oxidation catalyses were studied as a synthetic model of oxygen evolving complex (OEC) in photosynthesis using mica adsorbing various manganese species. Distribution of manganese species formed in the oxidative dimerization reaction of [Mn(II)(terpy)2](2+) (terpy=2,2':6',2″-terpyridine) (1') with various oxidants in water was revealed. 1' was stoichiometrically oxidized to form di-μ-oxo dinuclear manganese complex, [(OH2)(terpy)Mn(III)(μ-O)2Mn(IV)(terpy)(OH2)](3+) (1) by KMnO4 as an oxidant. When Oxone and Ce(IV) oxidants were used, the further oxidation of 1 to [(OH2)(terpy)Mn(IV)(μ-O)2Mn(IV)(terpy)(OH2)](4+) (2) was observed after the oxidative dimerization reaction of 1'. The mica adsorbates with various composition of 1', 1 and 2 were prepared by adding mica suspension to the various oxidant-treated solutions followed by filtration. The heterogeneous water oxidation catalysis by the mica adsorbates was examined using a Ce(IV) oxidant. The observed catalytic activity of the mica adsorbates corresponded to a content of 1 (1ads) adsorbed on mica for KMnO4- and Oxone-treated systems, indicating that 1' (1'ads) and 2 (2ads) adsorbed on mica do not work for the catalysis. The kinetic analysis suggested that 1ads works for the catalysis through cooperation with adjacent 1ads or 2ads, meaning that 2ads assists the cooperative catalysis by 1ads though 2ads is not able to work for the catalysis alone. For the Ce(IV)-treated system, O2 evolution was hardly observed although the sufficient amount of 1ads was contained in the mica adsorbates. This was explained by the impeded penetration of Ce(IV) ions (as an oxidant for water oxidation) into mica by Ce(3+) cations (generated in oxidative dimerization of 1') co-adsorbed with 1ads.

  6. Photochemical activation of ruthenium(II)-pyridylamine complexes having a pyridine-N-oxide pendant toward oxygenation of organic substrates.

    Kojima, Takahiko; Nakayama, Kazuya; Sakaguchi, Miyuki; Ogura, Takashi; Ohkubo, Kei; Fukuzumi, Shunichi


    Ruthenium(II)-acetonitrile complexes having η(3)-tris(2-pyridylmethyl)amine (TPA) with an uncoordinated pyridine ring and diimine such as 2,2'-bipyridine (bpy) and 2,2'-bipyrimidine (bpm), [Ru(II)(η(3)-TPA)(diimine)(CH(3)CN)](2+), reacted with m-chloroperbenzoic acid to afford corresponding Ru(II)-acetonitrile complexes having an uncoordinated pyridine-N-oxide arm, [Ru(II)(η(3)-TPA-O)(diimine)(CH(3)CN)](2+), with retention of the coordination environment. Photoirradiation of the acetonitrile complexes having diimine and the η(3)-TPA with the uncoordinated pyridine-N-oxide arm afforded a mixture of [Ru(II)(TPA)(diimine)](2+), intermediate-spin (S = 1) Ru(IV)-oxo complex with uncoordinated pyridine arm, and intermediate-spin Ru(IV)-oxo complex with uncoordinated pyridine-N-oxide arm. A Ru(II) complex bearing an oxygen-bound pyridine-N-oxide as a ligand and bpm as a diimine ligand was also obtained, and its crystal structure was determined by X-ray crystallography. Femtosecond laser flash photolysis of the isolated O-coordinated Ru(II)-pyridine-N-oxide complex has been investigated to reveal the photodynamics. The Ru(IV)-oxo complex with an uncoordinated pyridine moiety was alternatively prepared by reaction of the corresponding acetonitrile complex with 2,6-dichloropyridine-N-oxide (Cl(2)py-O) to identify the Ru(IV)-oxo species. The formation of Ru(IV)-oxo complexes was concluded to proceed via intermolecular oxygen atom transfer from the uncoordinated pyridine-N-oxide to a Ru(II) center on the basis of the results of the reaction with Cl(2)py-O and the concentration dependence of the consumption of the starting Ru(II) complexes having the uncoordinated pyridine-N-oxide moiety. Oxygenation reactions of organic substrates by [Ru(II)(η(3)-TPA-O)(diimine)(CH(3)CN)](2+) were examined under irradiation (at 420 ± 5 nm) and showed selective allylic oxygenation of cyclohexene to give cyclohexen-1-ol and cyclohexen-1-one and cumene oxygenation to afford cumyl alcohol

  7. Influence of strain on the structural instabilities and functional properties of complex oxides

    Hatt, Alison J.

    Complex oxides display a tremendous array of functional properties, ranging from ferroelectricity to giant magnetoresistance to superconductivity. Epitaxial strain in thin films of these materials provides a tool to further manipulate the available functionalities and presents an attractive avenue for material design. Arising from mismatch between films and substrate lattice parameters, strain can have profound effects on material properties by altering the energy balance between competing structural instabilities. Here we use density functional calculations to address the influence of strain on ABO 3 perovskite oxides, examining the impact on structural instabilities and focusing on regions in which strain induces phase transition phenomena. The density functional approach gives us access to the atomic-level details of a material's response to strain, enabling us to disentangle competing instabilities and differentiate between the ionic, electronic and lattice responses. In particular, we seek to illuminate the coupling of strain to distortion modes involving rigid rotations of the BO6 octahedral units. These octahedral rotations are known to drive or prohibit a number of strain-induced phenomena in functional oxides, but the details of their coupling to strain were not previously well understood. We develop our topic through investigations on four perovskite systems. We first study a layered superlattice of La(Al,Fe,Cr)O3, to distinguish the effect of misfit strain from the symmetry constraint imposed by heterostructuring. We then focus on the influence of strain in a series of single-phase perovskites of increasing complexity. In the simple dielectric LaAlO3, we isolate the strain-rotation coupling, develop a model for the dependence of rotations on bi-axial and uni-axial strain, and characterize a previously unidentified strain-induced phase transition. Next, we address strain in a polar material, multiferroic BiFeO3, to investigate recent experimental reports

  8. Fully delocalized (ethynyl)(vinyl)phenylene bridged triruthenium complexes in up to five different oxidation states.

    Wuttke, Evelyn; Pevny, Florian; Hervault, Yves-Marie; Norel, Lucie; Drescher, Malte; Winter, Rainer F; Rigaut, Stéphane


    Triruthenium [(dppe)(2)Ru{-C≡C-1,4-C(6)H(2)-2,5-R(2)-CH═CH-RuCl(CO)(P(i)Pr(3))(2)}(2)](n+) (4a, R = H; 4b, R = OMe) containing unsymmetrical (ethynyl)(vinyl)phenylene bridging ligands and displaying five well-separated redox states (n = 0-4) are compared to their bis(alkynyl)ruthenium precursors (dppe)(2)Ru{-C≡C-1,4-C(6)H(2)-2,5-R(2)-C≡CR'} (2a,b: R' = TMS; 3a,b: R' = H) and their symmetrically substituted bimetallic congeners, complexes {Cl(dppe)(2)Ru}(2){μ-C≡C-1,4-C(6)H(2)-2,5-R(2)-C≡C} (A(a), R = H; A(b), R = OMe) and {RuCl(CO)(P(i)Pr(3))(2)}(2){μ-CH═CH-1,4-C(6)H(2)-2,5-R(2)-CH═CH} (V(a), R = H; V(b), R = OMe) as well as the mixed (ethynyl)(vinyl)phenylene bridged [Cl(dppe)(2)Ru-C≡C-1,4-C(6)H(4)-CH═CH-RuCl(CO)(P(i)Pr(3))(2)] (M(a)). Successive one-electron transfer steps were studied by means of cyclic voltammetry, EPR and UV-vis-NIR-IR spectroelectrochemistry. These studies show that the first oxidation mainly involves the central bis(alkynyl) ruthenium moiety with only limited effects on the appended vinyl ruthenium moieties. The second to fourth oxidations (n = 2, 3, 4) involve the entire carbon-rich conjugated path of the molecule with an increased charge uniformly distributed between the two arms of the molecules, including the terminal vinyl ruthenium sites. In order to assess the charge distribution, we judiciously use (13)CO labeled analogues to distinguish stretching vibrations due to the acetylide triple bonds and the intense and charge-sensitive Ru(CO) IR probe in different oxidation states. The comparison between complex pairs 4a,b(n+) (n = 0-3), A(a,b)(n+) and V(a,b)(n+) (n = 0-2) serves to elucidate the effect of the methoxy donor substituents on the redox and spectroscopic properties of these systems in their various oxidation states and on the metal/ligand contributions to their frontier orbitals.

  9. Mitochondrial Complex I Inhibitors and Forced Oxidative Phosphorylation Synergize in Inducing Cancer Cell Death

    Roberta Palorini


    Full Text Available Cancer cells generally rely mostly on glycolysis rather than oxidative phosphorylation (OXPHOS for ATP production. In fact, they are particularly sensitive to glycolysis inhibition and glucose depletion. On the other hand mitochondrial dysfunctions, involved in the onset of the Warburg effect, are sometimes also associated with the resistance to apoptosis that characterizes cancer cells. Therefore, combined treatments targeting both glycolysis and mitochondria function, exploiting peculiar tumor features, might be lethal for cancer cells. In this study, we show that glucose deprivation and mitochondrial Complex I inhibitors synergize in inducing cancer cell death. In particular, our results reveal that low doses of Complex I inhibitors, ineffective on immortalized cells and in high glucose growth, become specifically cytotoxic on cancer cells deprived of glucose. Importantly, the cytotoxic effect of the inhibitors on cancer cells is strongly enhanced by forskolin, a PKA pathway activator, that we have previously shown to stimulate OXPHOS. Taken together, we demonstrate that induction in cancer cells of a switch from a glycolytic to a more respirative metabolism, obtained by glucose depletion or mitochondrial activity stimulation, strongly increases their sensitivity to low doses of mitochondrial Complex I inhibitors. Our findings might be a valuable approach to eradicate cancer cells.

  10. Experimental and Computational Evidence for the Reduction Mechanisms of Aromatic N-oxides by Aqueous Fe(II)-Tiron Complex.

    Chen, Yiling; Dong, Hao; Zhang, Huichun


    A combined experimental-theoretical approach was taken to elucidate the reduction mechanisms of five representative aromatic N-oxides (ANOs) by Fe(II)-tiron complex and to identify the rate-limiting step. Based on the possible types of complexes formed with the reductant, three groups of ANOs were studied: type I refers to those forming 5-membered ring complexes through the N and O atoms on the side chain; type II refers to those forming 6-membered ring complexes through the N-oxide O atom and the O atom on the side chain; and type III refers to complexation through the N-oxide O atom only. Density functional theory calculations suggested that the elementary reactions, including protonation, N-O bond cleavage, and the second electron transfer processes, are barrierless, indicating that the first electron transfer is rate-limiting. Consistent with the theoretical results, the experimental solvent isotope effect, KIEH, for the reduction of quinoline N-oxide (a type III ANO) was obtained to be 1.072 ± 0.025, suggesting protonation was not involved in the rate-limiting step. The measured nitrogen kinetic isotope effect, KIEN, for the reduction of pyridine N-oxide (a type III ANO) (1.022 ± 0.006) is in good agreement with the calculated KIEN for its first electron transfer (1.011-1.028), confirming that the first electron transfer is rate-limiting. Electrochemical cell experiments demonstrated that the electron transfer process can be facilitated significantly by type I complexation with FeL2(6-) (1:2 Fe(II)-tiron complex), to some extent by type II complexation with free Fe(II), but not by weak type III complexation.

  11. The Effect of Aging on Mitochondrial Complex I and the Extent of Oxidative Stress in the Rat Brain Cortex.

    Tatarkova, Zuzana; Kovalska, Maria; Timkova, Veronika; Racay, Peter; Lehotsky, Jan; Kaplan, Peter


    One of the characteristic features of the aging is dysfunction of mitochondria. Its role in the regulation of metabolism and apoptosis suggests a possible link between these cellular processes. This study investigates the relationship of respiratory complex I with aging-related oxidative stress in the cerebral mitochondria. Deterioration of complex I seen in senescent (26-months old) mitochondria was accompanied by decline in total thiol group content, increase of HNE and HNE-protein adducts as well as decreased content of complex I subunits, GRIM-19 and NDUFV2. On the other hand, decline of complex I might be related with the mitochondrial apoptosis through increased Bax/Bcl-2 cascade in 15-month old animal brains. Higher amount of Bcl-2, Bcl-xL with the lower content of GRIM-19 could maintain to some extent elevated oxidative stress in mitochondria as seen in the senescent group. In the cortical M1 region increased presence of TUNEL+ cells and more than 20-times higher density of Fluoro-Jade C+ cells in 26-months old was observed, suggesting significant neurodegenerative effect of aging in the neuronal cells. Our study supports a scenario in which the age-related decline of complex I might sensitize neurons to the action of death agonists, such as Bax through lipid and protein oxidative stimuli in mitochondria. Although aging is associated with oxidative stress, these changes did not increase progressively with age, as similar extent of lesions was observed in oxidative stress markers of the both aged groups.

  12. The oxidative p-dichlorobenzene dechlorinating in the presence of copper (ΙΙ complexes and nitrogen (ΙΙ, ΙV oxides

    Valentina Yemelyanova


    Full Text Available The results of dechlorination in the solution CuCl2–TBP–NaNO2–О2–Н2О kinetics research are presented in the article. All system components influence to the dechlorination process is studied and quantitatively described. The composition of copper intermediate complexes participating in reaction is studied by the instrumentality of UV-spectroscopy. Established part of binuclear copper complexes in the catalytic intermediate complex constants of formation were estimated and compared with the kinetic and spectrophotometric methods. The composition of the intermediate complexes responsible for process is defined, the mechanism scheme is offered, the p-dichlorobenzene dechlorination limiting stage including redox-disintegration of the intermediate complex consisting of dimeric complex of copper (II, I chloride, nitrogen oxide and p-dichlorobenzene is defined.

  13. Dietary protein restriction decreases oxidative protein damage, peroxidizability index, and mitochondrial complex I content in rat liver.

    Ayala, Victoria; Naudí, Alba; Sanz, Alberto; Caro, Pilar; Portero-Otin, Manuel; Barja, Gustavo; Pamplona, Reinald


    Caloric restriction (CR) decreases oxidative damage, which contributes to the slowing of aging rate. It is not known if such decreases are due to calories themselves or specific dietary components. In this work, the ingestion of proteins of Wistar rats was decreased by 40% below that of controls. After 7 weeks, the liver of the protein-restricted (PR) animals showed decreases in oxidative protein damage, degree of membrane unsaturation, and mitochondrial complex I content. The results and previous information suggest that the decrease in the rate of aging induced by PR can be due in part to decreases in mitochondrial reactive oxygen species production and DNA and protein oxidative modification, increases in fatty acid components more resistant to oxidative damage, and decreased expression of complex I, analogously to what occurs during CR. Recent studies suggest that those benefits of PR could be caused, in turn, by the lowered methionine intake of that dietary manipulation.

  14. Phase Behavior and Crystal Structure of Perovskite-Type Rare Earth Complex Oxides


    Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33Mn0.33Ti0.67O3 (A=Ca or Sr and Ln=rare earth) were found to have orthorhombic symmetry with the space group Pnma, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Ca0.67Ln0.33Mn0.33Ti0.67O3 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.

  15. Spatially resolved ultrafast magnetic dynamics initiated at a complex oxide heterointerface

    Caviglia, Andrea

    Static strain in complex oxide heterostructures has been extensively used to engineer electronic and magnetic properties at equilibrium. In the same spirit, deformations of the crystal lattice with light may be used to achieve functional control across heterointerfaces dynamically. Here, by exciting large-amplitude infrared-active vibrations in a LaAlO3 substrate we induce magnetic order melting in a NdNiO3 film across a heterointerface. Femtosecond resonant soft X-ray diffraction is used to determine the spatiotemporal evolution of the magnetic disordering. We observe a magnetic melt front that propagates from the substrate interface into the film, at a speed that suggests electronically driven motion. Light control and ultrafast phase front propagation at heterointerfaces may lead to new opportunities in optomagnetism.

  16. Influence of complex impurity centres on radiation damage in wide-gap metal oxides

    Lushchik, A., E-mail: [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Lushchik, Ch. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Popov, A.I. [Institute of Solid State Physics, University of Latvia, Kengaraga 8, Riga LV-1063 (Latvia); Schwartz, K. [GSI Helmholtzzentrum für Schwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt (Germany); Shablonin, E.; Vasil’chenko, E. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia)


    Different mechanisms of radiation damage of wide-gap metal oxides as well as a dual influence of impurity ions on the efficiency of radiation damage have been considered on the example of binary ionic MgO and complex ionic–covalent Lu{sub 3}Al{sub 5}O{sub 12} single crystals. Particular emphasis has been placed on irradiation with ∼2 GeV heavy ions ({sup 197}Au, {sup 209}Bi, {sup 238}U, fluence of 10{sup 12} ions/cm{sup 2}) providing extremely high density of electronic excitations within ion tracks. Besides knock-out mechanism for Frenkel pair formation, the additional mechanism through the collapse of mobile discrete breathers at certain lattice places (e.g., complex impurity centres) leads to the creation of complex defects that involve a large number of host atoms. The experimental manifestations of the radiation creation of intrinsic and impurity antisite defects (Lu|{sub Al} or Ce|{sub Al} – a heavy ion in a wrong cation site) have been detected in LuAG and LuAG:Ce{sup 3+} single crystals. Light doping of LuAG causes a small enhancement of radiation resistance, while pair impurity centres (for instance, Ce|{sub Lu}–Ce|{sub Al} or Cr{sup 3+}–Cr{sup 3+} in MgO) are formed with a rise of impurity concentration. These complex impurity centres as well as radiation-induced intrinsic antisite defects (Lu|{sub Al} strongly interacting with Lu in a regular site) tentatively serve as the places for breathers collapse, thus decreasing the material resistance against dense irradiation.

  17. Surface complexation modeling of Cu(II adsorption on mixtures of hydrous ferric oxide and kaolinite

    Schaller Melinda S


    Full Text Available Abstract Background The application of surface complexation models (SCMs to natural sediments and soils is hindered by a lack of consistent models and data for large suites of metals and minerals of interest. Furthermore, the surface complexation approach has mostly been developed and tested for single solid systems. Few studies have extended the SCM approach to systems containing multiple solids. Results Cu adsorption was measured on pure hydrous ferric oxide (HFO, pure kaolinite (from two sources and in systems containing mixtures of HFO and kaolinite over a wide range of pH, ionic strength, sorbate/sorbent ratios and, for the mixed solid systems, using a range of kaolinite/HFO ratios. Cu adsorption data measured for the HFO and kaolinite systems was used to derive diffuse layer surface complexation models (DLMs describing Cu adsorption. Cu adsorption on HFO is reasonably well described using a 1-site or 2-site DLM. Adsorption of Cu on kaolinite could be described using a simple 1-site DLM with formation of a monodentate Cu complex on a variable charge surface site. However, for consistency with models derived for weaker sorbing cations, a 2-site DLM with a variable charge and a permanent charge site was also developed. Conclusion Component additivity predictions of speciation in mixed mineral systems based on DLM parameters derived for the pure mineral systems were in good agreement with measured data. Discrepancies between the model predictions and measured data were similar to those observed for the calibrated pure mineral systems. The results suggest that quantifying specific interactions between HFO and kaolinite in speciation models may not be necessary. However, before the component additivity approach can be applied to natural sediments and soils, the effects of aging must be further studied and methods must be developed to estimate reactive surface areas of solid constituents in natural samples.

  18. Chirality recognition in the glycidol···propylene oxide complex: a rotational spectroscopic study.

    Thomas, Javix; Sunahori, Fumie X; Borho, Nicole; Xu, Yunjie


    Chirality recognition in the hydrogen-bonded glycidol···propylene oxide complex has been studied by using rotational spectroscopy and ab initio calculations. An extensive conformational search has been performed for this binary adduct at the MP2/6-311++G(d,p) level of theory and a total of 28 homo- and heterochiral conformers were identified. The eight binary conformers, built of the two dominant glycidol monomeric conformers, g-G+ and g+G-, were predicted to be the most stable ones. Jet-cooled rotational spectra of six out of the eight conformers were observed and unambiguously assigned for the first time. The experimental stability ordering has been obtained and compared with the ab initio predictions. The relative stability of the two dominant glycidol monomeric conformers is reversed in some cases when binding to propylene oxide. The contributions of monomeric energy, deformation energy, and binary intermolecular interaction energy to the relative stability of the binary conformers are discussed.

  19. Copper Recovery from Yulong Complex Copper Oxide Ore by Flotation and Magnetic Separation

    Han, Junwei; Xiao, Jun; Qin, Wenqing; Chen, Daixiong; Liu, Wei


    A combined process of flotation and high-gradient magnetic separation was proposed to utilize Yulong complex copper oxide ore. The effects of particle size, activators, Na2S dosage, LA (a mixture of ammonium sulfate and ethylenediamine) dosage, activating time, collectors, COC (a combination collector of modified hydroxyl oxime acid and xanthate) dosage, and magnetic intensity on the copper recovery were investigated. The results showed that 74.08% Cu was recovered by flotation, while the average grade of the copper concentrates was 21.68%. Another 17.34% Cu was further recovered from the flotation tailing by magnetic separation at 0.8 T. The cumulative recovery of copper reached 91.42%. The modifier LA played a positive role in facilitating the sulfidation of copper oxide with Na2S, and the combined collector COC was better than other collectors for the copper flotation. This technology has been successfully applied to industrial production, and the results are consistent with the laboratory data.

  20. First-principles analysis of X-ray magnetic circular dichroism for transition metal complex oxides

    Ikeno, Hidekazu


    X-ray magnetic circular dichroism (XMCD) is widely used for the characterization of magnetism of materials. However, information from XMCD related to the atomic, electronic, and magnetic structures is not fully utilized due to the lack of reliable theoretical tools for spectral analysis. In this work, the first-principles configuration interaction (CI) calculations for X-ray absorption spectra developed by the author were extended for the calculation of XMCD, where the Zeeman energy was taken into the Hamiltonian of the CI to mimic magnetic polarization in the solid state. This technique was applied to interpret the L2,3 XMCD from 3d transition metal complex oxides, such as NiFe2O4 and FeTiO3. The experimental XMCD spectra were quantitatively reproduced using this method. The oxidation states as well as the magnetic ordering between transition metal ions on crystallographically different sites in NiFe2O4 can be unambiguously determined. A first-principles analysis of XMCD in FeTiO3 revealed the presence of Fe3+ and Ti3+ ions, which indicates that the charge transfer from Fe to Ti ions occurs. The origin of magnetic polarization of Ti ions in FeTiO3 was also discussed.

  1. Structural investigations of complex perovskite oxide films with X-ray diffraction

    Boldyreva, Ksenia; Rata, Diana; Herklotz, Andreas; Bilani-Zeneli, Orkidia; Huehne, Ruben; Schultz, Ludwig; Doerr, Kathrin [IFW Dresden (Germany)


    The electronic and magnetic properties of many complex oxides are highly sensitive to external parameters which include mechanical deformation or strain. Thus, X-ray diffraction methods such as reciprocal space mapping are powerful and indispensable for the characterization of thin films, particularly for evaluating the in-plane strain state. The direct influence of strain on the magnetization of epitaxial La{sub 1-x}Sr{sub x}MnO{sub 3} (LSMO) films has been studied utilizing piezoelectric PMN-PT substrates. On the other hand, La{sub 1-x}Sr{sub x}CoO{sub 3} (LSCO) films also reveal large strain-induced changes of the magnetization and the electrical conductivity. Since the in-plane lattice parameter of the piezoelectric substrate, PMN-PT, of {proportional_to}4.02A is larger than that of most correlated oxides, LaSc{sub 1-x}Al{sub x}O{sub 3} (LSAO) has been explored as a buffer layer showing a lattice parameter that is tunable by the composition x. The lattice structure of (i) LSAO buffers depending on the composition and (ii) of magnetic films (LSMO, LSCO) grown in various strain states is discussed.

  2. Polyoxometalate coordinated transition metal complexes as catalysts: Oxidation of styrene to benzaldehyde/benzoic acid

    Srinivasa Rao Amanchi; Anjali Patel; Samar K Das


    Oxidation of styrene is carried out by using heptamolybdate coordinated transition metal (Co2+, Zn2+) complexes, [2-ampH]4[{Co(H2O)5}Mo7O24]·9H2O (1), [3-ampH]4[{Co(H2O)5}Mo7O24]·9H2O (2), [2-ampH]4[{Zn(H2O)5}Mo7O24]·4H2O (3) and [3-ampH]4[{Zn(3-ampy)(H2O)4}Mo7O24]·4H2O (4) as catalysts and H2O2 as an oxidant at 80°C. The leaching study has been carried out to check the quality of catalyst and it has been reused for three times with good percentage of conversion. For the first two catalysts (compounds 1 and 2), the major product obtained is benzaldehyde, and benzoic acid is the major product for next two catalysts (compounds 3 and 4). Stability of the catalysts has been analyzed by IR, UV-spectroscopy and powder X-ray crystallography.

  3. A novel pre-oxidation method for elemental mercury removal utilizing a complex vaporized absorbent.

    Zhao, Yi; Hao, Runlong; Guo, Qing


    A novel semi-dry integrative method for elemental mercury (Hg(0)) removal has been proposed in this paper, in which Hg(0) was initially pre-oxidized by a vaporized liquid-phase complex absorbent (LCA) composed of a Fenton reagent, peracetic acid (CH3COOOH) and sodium chloride (NaCl), after which Hg(2+) was absorbed by the resultant Ca(OH)2. The experimental results indicated that CH3COOOH and NaCl were the best additives for Hg(0) oxidation. Among the influencing factors, the pH of the LCA and the adding rate of the LCA significantly affected the Hg(0) removal. The coexisting gases, SO2 and NO, were characterized as either increasing or inhibiting in the removal process, depending on their concentrations. Under optimal reaction conditions, the efficiency for the single removal of Hg(0) was 91%. Under identical conditions, the efficiencies of the simultaneous removal of SO2, NO and Hg(0) were 100%, 79.5% and 80.4%, respectively. Finally, the reaction mechanism for the simultaneous removal of SO2, NO and Hg(0) was proposed based on the characteristics of the removal products as determined by X-ray diffraction (XRD), atomic fluorescence spectrometry (AFS), the analysis of the electrode potentials, and through data from related research references.

  4. First-principles analysis of X-ray magnetic circular dichroism for transition metal complex oxides

    Ikeno, Hidekazu, E-mail: [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, 1-2 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8570 (Japan)


    X-ray magnetic circular dichroism (XMCD) is widely used for the characterization of magnetism of materials. However, information from XMCD related to the atomic, electronic, and magnetic structures is not fully utilized due to the lack of reliable theoretical tools for spectral analysis. In this work, the first-principles configuration interaction (CI) calculations for X-ray absorption spectra developed by the author were extended for the calculation of XMCD, where the Zeeman energy was taken into the Hamiltonian of the CI to mimic magnetic polarization in the solid state. This technique was applied to interpret the L{sub 2,3} XMCD from 3d transition metal complex oxides, such as NiFe{sub 2}O{sub 4} and FeTiO{sub 3}. The experimental XMCD spectra were quantitatively reproduced using this method. The oxidation states as well as the magnetic ordering between transition metal ions on crystallographically different sites in NiFe{sub 2}O{sub 4} can be unambiguously determined. A first-principles analysis of XMCD in FeTiO{sub 3} revealed the presence of Fe{sup 3+} and Ti{sup 3+} ions, which indicates that the charge transfer from Fe to Ti ions occurs. The origin of magnetic polarization of Ti ions in FeTiO{sub 3} was also discussed.

  5. A novel pre-oxidation method for elemental mercury removal utilizing a complex vaporized absorbent

    Zhao, Yi, E-mail:; Hao, Runlong; Guo, Qing


    Graphical abstract: - Highlights: • An innovative liquid-phase complex absorbent (LCA) for Hg{sup 0} removal was prepared. • A novel integrative process for Hg{sup 0} removal was proposed. • The simultaneous removal efficiencies of SO{sub 2}, NO and Hg{sup 0} were 100%, 79.5% and 80.4%, respectively. • The reaction mechanism of simultaneous removal of SO{sub 2}, NO and Hg{sup 0} was proposed. - Abstract: A novel semi-dry integrative method for elemental mercury (Hg{sup 0}) removal has been proposed in this paper, in which Hg{sup 0} was initially pre-oxidized by a vaporized liquid-phase complex absorbent (LCA) composed of a Fenton reagent, peracetic acid (CH{sub 3}COOOH) and sodium chloride (NaCl), after which Hg{sup 2+} was absorbed by the resultant Ca(OH){sub 2}. The experimental results indicated that CH{sub 3}COOOH and NaCl were the best additives for Hg{sup 0} oxidation. Among the influencing factors, the pH of the LCA and the adding rate of the LCA significantly affected the Hg{sup 0} removal. The coexisting gases, SO{sub 2} and NO, were characterized as either increasing or inhibiting in the removal process, depending on their concentrations. Under optimal reaction conditions, the efficiency for the single removal of Hg{sup 0} was 91%. Under identical conditions, the efficiencies of the simultaneous removal of SO{sub 2}, NO and Hg{sup 0} were 100%, 79.5% and 80.4%, respectively. Finally, the reaction mechanism for the simultaneous removal of SO{sub 2}, NO and Hg{sup 0} was proposed based on the characteristics of the removal products as determined by X-ray diffraction (XRD), atomic fluorescence spectrometry (AFS), the analysis of the electrode potentials, and through data from related research references.

  6. Influence of Copper Oxidation State on the Bonding and Electronic Structure of Cobalt-Copper Complexes

    Eisenhart, Reed J.; Carlson, Rebecca K.; Clouston, Laura J.; Young, Jr., Victor G.; Chen, Yu-Sheng; Bill, Eckhard; Gagliardi, Laura; Lu, Connie C. (UC); (UMM); (MXPL)


    Heterobimetallic complexes that pair cobalt and copper were synthesized and characterized by a suite of physical methods, including X-ray diffraction, X-ray anomalous scattering, cyclic voltammetry, magnetometry, electronic absorption spectroscopy, electron paramagnetic resonance, and quantum chemical methods. Both Cu(II) and Cu(I) reagents were independently added to a Co(II) metalloligand to provide (py3tren)CoCuCl (1-Cl) and (py3tren)CoCu(CH3CN) (2-CH3CN), respectively, where py3tren is the triply deprotonated form of N,N,N-tris(2-(2-pyridylamino)ethyl)amine. Complex 2-CH3CN can lose the acetonitrile ligand to generate a coordination polymer consistent with the formula “(py3tren)CoCu” (2). One-electron chemical oxidation of 2-CH3CN with AgOTf generated (py3tren)CoCuOTf (1-OTf). The Cu(II)/Cu(I) redox couple for 1-OTf and 2-CH3CN is reversible at -0.56 and -0.33 V vs Fc+/Fc, respectively. The copper oxidation state impacts the electronic structure of the heterobimetallic core, as well as the nature of the Co–Cu interaction. Quantum chemical calculations showed modest electron delocalization in the (CoCu)+4 state via a Co–Cu σ bond that is weakened by partial population of the Co–Cu σ antibonding orbital. By contrast, no covalent Co–Cu bonding is predicted for the (CoCu)+3 analogue, and the d-electrons are fully localized at individual metals.

  7. Enhanced photovoltaic effect of ruthenium complex-modified graphene oxide with P-type conductivity

    Zhang, Wei, E-mail:; Bai, Huicong; Zhang, Yu; Sun, Ying; Lin, Shen; Liu, Jian; Yang, Qi; Song, Xi-Ming, E-mail:


    A graphene oxide nanocomposite with bis(1,10-phenanthroline)(N-(2-aminoethyl)-4-(4-methyl-2,2-bipyridine-4-yl) formamide) ruthenium (Ru(phen){sub 2}(bpy-NH{sub 2})(PF{sub 6}){sub 2}), a ruthenium complex, was synthesized by amidation reaction between amino group of the ruthenium complex and carboxyl group of GO. The as-prepared Ru(II)–GO composite was characterized by infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–Vis) absorption spectra, fluorescence spectra, surface photovoltage (SPV) spectrum and transient photovoltage (TPV) technology. This nanocomposite showed a typical p-type character and an enhanced photovoltaic effect at long timescale of about 3 × 10{sup −3} s compared to GO alone. A reversible rise/decay of the photocurrent in response to the on/off illumination step was also observed in a photoelectrochemical cell of the Ru(II)–GO composite. The photocurrent response of the Ru(II)–GO film was remarkably higher than that of GO film. Therefore, this Ru(II)–GO composite is believed to be a promising p-type photoelectric conversion material for further photovoltaic applications. - Highlights: • A new dye-sensitized graphene oxide nanocomposite was reported. • A photo-induced charge transfer process in this nanocomposite was confirmed. • This composite showed a typical p-type conductivity. • This composite showed an enhanced photovoltaic effect at a long timescale.

  8. Regulation of fatty acid oxidation in mouse cumulus-oocyte complexes during maturation and modulation by PPAR agonists.

    Kylie R Dunning

    Full Text Available Fatty acid oxidation is an important energy source for the oocyte; however, little is known about how this metabolic pathway is regulated in cumulus-oocyte complexes. Analysis of genes involved in fatty acid oxidation showed that many are regulated by the luteinizing hormone surge during in vivo maturation, including acyl-CoA synthetases, carnitine transporters, acyl-CoA dehydrogenases and acetyl-CoA transferase, but that many are dysregulated when cumulus-oocyte complexes are matured under in vitro maturation conditions using follicle stimulating hormone and epidermal growth factor. Fatty acid oxidation, measured as production of ³H₂O from [³H]palmitic acid, occurs in mouse cumulus-oocyte complexes in response to the luteinizing hormone surge but is significantly reduced in cumulus-oocyte complexes matured in vitro. Thus we sought to determine whether fatty acid oxidation in cumulus-oocyte complexes could be modulated during in vitro maturation by lipid metabolism regulators, namely peroxisome proliferator activated receptor (PPAR agonists bezafibrate and rosiglitazone. Bezafibrate showed no effect with increasing dose, while rosiglitazone dose dependently inhibited fatty acid oxidation in cumulus-oocyte complexes during in vitro maturation. To determine the impact of rosiglitazone on oocyte developmental competence, cumulus-oocyte complexes were treated with rosiglitazone during in vitro maturation and gene expression, oocyte mitochondrial activity and embryo development following in vitro fertilization were assessed. Rosiglitazone restored Acsl1, Cpt1b and Acaa2 levels in cumulus-oocyte complexes and increased oocyte mitochondrial membrane potential yet resulted in significantly fewer embryos reaching the morula and hatching blastocyst stages. Thus fatty acid oxidation is increased in cumulus-oocyte complexes matured in vivo and deficient during in vitro maturation, a known model of poor oocyte quality. That rosiglitazone further

  9. A new oxo-vanadium complex employing an imidazole-rich tripodal ligand: a bioinspired bromide and hydrocarbon oxidation catalyst.

    Fernández, Tatiana L; Souza, Elizabeth T; Visentin, Lorenzo C; Santos, Jeniffer V; Mangrich, Antonio S; Faria, Roberto B; Antunes, O A C; Scarpellini, Marciela


    A vanadyl complex with the ligand (bis(1-methylimidazol-2-yl)methyl)(2-(pyridyl-2-yl)ethyl)amine was synthesized and fully characterized by X-ray crystallography, elemental analyses, cyclic voltammetry and infrared, electronic and electron paramagnetic resonance spectroscopies. This compound was designed under the so called hybrid concept. It shows to be able to promiscuously use hydrogen peroxide to oxidize bromide and to catalyze the oxidation of benzene and cyclohexane with very good selectivities.

  10. Bioaccumulation and effects of metals on oxidative stress and neurotoxicity parameters in the frogs from the Pelophylax esculentus complex.

    Prokić, Marko D; Borković-Mitić, Slavica S; Krizmanić, Imre I; Mutić, Jelena J; Trifković, Jelena Đ; Gavrić, Jelena P; Despotović, Svetlana G; Gavrilović, Branka R; Radovanović, Tijana B; Pavlović, Slađan Z; Saičić, Zorica S


    Metals are involved in the formation of reactive oxygen species and can induce oxidative stress. The aim of this study was to assess the effects of several metals on oxidative stress in the skin and muscle of the Pelophylax esculentus "complex" frogs (parental species Pelophylax ridibundus, Pelophylax lessonae, and their hybrid Pelophylax esculentus) that inhabit the wetland Obedska Bara in Serbia, and the potential use of these species as bioindicator organisms in biomonitoring studies. The biomarkers of oxidative stress (SOD, CAT, GSH-Px, GR, GST activities and GSH, SH concentrations) and cholinesterase activity were investigated. The concentrations of nine metals (Fe, Cu, Zn, As, Cd, Cr, Hg, Ni, and Pb) were measured in the water and tissues. Correlations were established between metals and biomarkers in the tissues. The results of metal accumulation distinguished the skin of P. lessonae and muscle of P. ridibundus from other P. esculentus complex species. The oxidative stress biomarkers observed in P. ridibundus and P. esculentus had greater similarity than in P. lessonae. The P. lessonae displayed the highest number of correlations between biomarkers and metals. The results of tissue responses revealed that skin was more susceptible to metal-induced oxidative stress, with only exception of As. In the light of these findings, we can suggest the use of P. esculentus complex species as a biomonitoring species in studies of metal accumulation and metal-induced oxidative stress, but with special emphasis on P. lessonae.

  11. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    Comes, Ryan; Liu Hongxue; Lu Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Gu, Man [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Khokhlov, Mikhail; Wolf, Stuart A. [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Guilford College, Greensboro, North Carolina 27410 (United States)


    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  12. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    Comes, Ryan; Gu, Man; Khokhlov, Mikhail; Liu, Hongxue; Lu, Jiwei; Wolf, Stuart A.


    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  13. Mn(II) Oxidation by the Multicopper Oxidase Complex Mnx: A Binuclear Activation Mechanism.

    Soldatova, Alexandra V; Tao, Lizhi; Romano, Christine A; Stich, Troy A; Casey, William H; Britt, R David; Tebo, Bradley M; Spiro, Thomas G


    The bacterial protein complex Mnx contains a multicopper oxidase (MCO) MnxG that, unusually, catalyzes the two-electron oxidation of Mn(II) to MnO2 biomineral, via a Mn(III) intermediate. Although Mn(III)/Mn(II) and Mn(IV)/Mn(III) reduction potentials are expected to be high, we find a low reduction potential, 0.38 V (vs Normal Hydrogen Electrode, pH 7.8), for the MnxG type 1 Cu(2+), the electron acceptor. Indeed the type 1 Cu(2+) is not reduced by Mn(II) in the absence of molecular oxygen, indicating that substrate oxidation requires an activation step. We have investigated the enzyme mechanism via electronic absorption spectroscopy, using chemometric analysis to separate enzyme-catalyzed MnO2 formation from MnO2 nanoparticle aging. The nanoparticle aging time course is characteristic of nucleation and particle growth; rates for these processes followed expected dependencies on Mn(II) concentration and temperature, but exhibited different pH optima. The enzymatic time course is sigmoidal, signaling an activation step, prior to turnover. The Mn(II) concentration and pH dependence of a preceding lag phase indicates weak Mn(II) binding. The activation step is enabled by a pKa > 8.6 deprotonation, which is assigned to Mn(II)-bound H2O; it induces a conformation change (consistent with a high activation energy, 106 kJ/mol) that increases Mn(II) affinity. Mnx activation is proposed to decrease the Mn(III/II) reduction potential below that of type 1 Cu(II/I) by formation of a hydroxide-bridged binuclear complex, Mn(II)(μ-OH)Mn(II), at the substrate site. Turnover is found to depend cooperatively on two Mn(II) and is enabled by a pKa 7.6 double deprotonation. It is proposed that turnover produces a Mn(III)(μ-OH)2Mn(III) intermediate that proceeds to the enzyme product, likely Mn(IV)(μ-O)2Mn(IV) or an oligomer, which subsequently nucleates MnO2 nanoparticles. We conclude that Mnx exploits manganese polynuclear chemistry in order to facilitate an otherwise difficult

  14. High catalytic activity of heteropolynuclear cyanide complexes containing cobalt and platinum ions: visible-light driven water oxidation.

    Yamada, Yusuke; Oyama, Kohei; Gates, Rachel; Fukuzumi, Shunichi


    A near-stoichiometric amount of O2 was evolved as observed in the visible-light irradiation of an aqueous buffer (pH 8) containing [Ru(II) (2,2'-bipyridine)3 ] as a photosensitizer, Na2 S2 O8 as a sacrificial electron acceptor, and a heteropolynuclear cyanide complex as a water-oxidation catalyst. The heteropolynuclear cyanide complexes exhibited higher catalytic activity than a polynuclear cyanide complex containing only Co(III) or Pt(IV) ions as C-bound metal ions. The origin of the synergistic effect between Co and Pt ions is discussed in relation to electronic and local atomic structures of the complexes.

  15. Catalytic Oxidative Decarboxylation of Some Benzylcarboxylic Acid Derivatives by a New Iron(Ill) Schiff Base Complex



    A quadridentate Schiff base ligand of N,N'-bis(2-hydroxy-a-methylbenzylidene)ethylenediamine (HMBEDA) and its new iron(Ⅲ) complex were synthesized and identified by analytical, spectral data (1H NMR, 13C NMR FT-IR and UV-visible) and molar conductance. A rapid and efficient homogeneous oxidative decarboxylatio n ofsome benzylcarboxylic acid derivatives was carried out by a catalytic amount of iron(Ⅲ) Schiff base complex in chloroform, using tetrabutylammonium periodate as a mild oxidant in good to excellent yields at room temperature.

  16. Gold(I) carbene complexes causing thioredoxin 1 and thioredoxin 2 oxidation as potential anticancer agents.

    Schuh, Esther; Pflüger, Carolin; Citta, Anna; Folda, Alessandra; Rigobello, Maria Pia; Bindoli, Alberto; Casini, Angela; Mohr, Fabian


    Gold(I) complexes with 1,3-substituted imidazole-2-ylidene and benzimidazole-2-ylidene ligands of the type NHC-Au-L (NHC = N-heterocyclic carbene L = Cl or 2-mercapto-pyrimidine) have been synthesized and structurally characterized. The compounds were evaluated for their antiproliferative properties in human ovarian cancer cells sensitive and resistant to cisplatin (A2780S/R), as well in the nontumorigenic human embryonic kidney cell line (HEK-293T), showing in some cases important cytotoxic effects. Some of the complexes were comparatively tested as thioredoxin reductase (TrxR) and glutathione reductase (GR) inhibitors, directly against the purified proteins or in cell extracts. The compounds showed potent and selective TrxR inhibition properties in particular in cancer cell lines. Remarkably, the most effective TrxR inhibitors induced extensive oxidation of thioredoxins (Trxs), which was more relevant in the cancerous cells than in HEK-293T cells. Additional biochemical assays on glutathione systems and reactive oxygen species formation evidenced important differences with respect to the classical cytotoxic Au(I)-phosphine compound auranofin.

  17. Fabrication of complex oxide microstructures by combinatorial chemical beam vapour deposition through stencil masks

    Wagner, E. [3D-OXIDES, 70 rue Gustave Eiffel, Saint Genis Pouilly 01630 (France); Sandu, C.S., E-mail: [3D-OXIDES, 70 rue Gustave Eiffel, Saint Genis Pouilly 01630 (France); Laboratoire de Céramique, Ecole Polytechnique Fédérale de Lausanne, Station 12, CH-1015 Lausanne (Switzerland); Harada, S.; Benvenuti, G. [3D-OXIDES, 70 rue Gustave Eiffel, Saint Genis Pouilly 01630 (France); Savu, V. [Laboratoire de Microsystèmes 1, Ecole Polytechnique Fédérale de Lausanne, Station 17, CH-1015 Lausanne (Switzerland); Muralt, P. [Laboratoire de Céramique, Ecole Polytechnique Fédérale de Lausanne, Station 12, CH-1015 Lausanne (Switzerland)


    Chemical Beam Vapour Deposition is a gas phase deposition technique, operated under high vacuum conditions, in which evaporated chemical precursors are thermally decomposed on heated substrates to form a film. In the particular equipment used in this work, different chemical beams effuse from a plurality of punctual precursor sources with line of sight trajectory to the substrate. A shadow mask is used to produce 3D-structures in a single step, replicating the apertures of a stencil as deposits on the substrate. The small gap introduced between substrate and mask induces a temperature difference between both surfaces and is used to deposit selectively solely on the substrate without modifying the mask, taking advantage of the deposition rate dependency on temperature. This small gap also enables the deposition of complex patterned structures resulting from the superposition of many patterns obtained using several precursor beams from different directions through a single mask aperture. A suitable process parameter window for precursor flow and substrate temperature is evidenced to maximize resolution. - Highlights: • Micro-feature growth with stencil mask by Chemical Beam Vapour Deposition • Growth of complex structured oxide films in one step • The gap between substrate and mask avoids deposition on the stencil. • Fabrication of 3D structures by superposing deposits from several beams • The versatile setup combines few chemical beams, variable geometry and stencil mask patterns.

  18. A New Insight of Graphene oxide-Fe(III) Complex Photochemical Behaviors under Visible Light Irradiation

    Liu, Renlan; Zhu, Xiaoying; Chen, Baoliang


    Graphene oxide (GO) contains not only aromatic carbon lattice but also carboxyl groups which enhanced the aqueous solubility of GO. To study the transformation of GO nanosheets in natural environments, GO aqueous dispersion was mixed with Fe3+ ions to form photoactive complex. Under visible light irradiation, Fe(III) of the complex would be reduced to Fe(II) which could subsequently reduce highly toxic Cr(VI) to Cr3+. The electron of the reduction was contributed by the decarboxylation of carboxyl groups on GO and iron was acting as a catalyst during the photoreduction. On the other hand, the consumption of carboxyl groups may convert GO to rGO which are tend to aggregate since the decreased electrostatic repulsion and the increased π-π attraction. The formed Cr3+ may be electrostatically adsorbed by the rGO sheets and simultaneously precipitated with the aggregated rGO sheets, resulting the effective removal of chromium and GO nanosheets from the aqueous environment. This study may shed a light on understanding the environmental transformation of GO and guide the treatment of Cr(VI). PMID:28084446

  19. Aroylhydrazone Cu(II Complexes in keto Form: Structural Characterization and Catalytic Activity towards Cyclohexane Oxidation

    Manas Sutradhar


    Full Text Available The reaction of the Schiff base (3,5-di-tert-butyl-2-hydroxybenzylidene-2-hydroxybenzohydrazide (H3L with a copper(II salt of a base of a strong acid, i.e., nitrate, chloride or sulphate, yielded the mononuclear complexes [Cu(H2L(NO3(H2O] (1, [Cu(H2LCl]·2MeOH (2 and the binuclear complex [{Cu(H2L}2(µ-SO4]·2MeOH (3, respectively, with H2L− in the keto form. Compounds 1–3 were characterized by elemental analysis, Infrared (IR spectroscopy, Electrospray Ionisation Mass Spectrometry (ESI-MS and single crystal X-ray crystallography. All compounds act as efficient catalysts towards the peroxidative oxidation of cyclohexane to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone, under mild conditions. In the presence of an acid promoter, overall yields (based on the alkane up to 25% and a turnover number (TON of 250 (TOF of 42 h−1 after 6 h, were achieved.

  20. Indirect spectrophotometric determination of arbutin, whitening agent through oxidation by periodate and complexation with ferric chloride

    Barsoom, B. N.; Abdelsamad, A. M. E.; Adib, N. M.


    A simple and accurate spectrophotometric method for the determination of arbutin (glycosylated hydroquinone) is described. It is based on the oxidation of arbutin by periodate in presence of iodate. Excess periodate causes liberation of iodine at pH 8.0. The unreacted periodate is determined by measurement of the liberated iodine spectrophotometrically in the wavelength range (300-500 nm). A calibration curve was constructed for more accurate results and the correlation coefficient of linear regression analysis was -0.9778. The precision of this method was better than 6.17% R.S.D. ( n = 3). Regression analysis of Bear-Lambert plot shows good correlation in the concentration range 25-125 ug/ml. The identification limit was determined to be 25 ug/ml a detailed study of the reaction conditions was carried out, including effect of changing pH, time, temperature and volume of periodate. Analyzing pure and authentic samples containing arbutin tested the validity of the proposed method which has an average percent recovery of 100.86%. An alternative method is also proposed which involves a complexation reaction between arbutin and ferric chloride solution. The produced complex which is yellowish-green in color was determined spectophotometrically.

  1. Antileishmanial Activity and Inducible Nitric Oxide Synthase Activation by RuNO Complex

    Tatiane Marcusso Orsini


    Full Text Available Parasites of the genus Leishmania are capable of inhibiting effector functions of macrophages. These parasites have developed the adaptive ability to escape host defenses; for example, they inactivate the NF-κB complex and suppress iNOS expression in infected macrophages, which are responsible for the production of the major antileishmanial substance nitric oxide (NO, favoring then its replication and successful infection. Metal complexes with NO have been studied as potential compounds for the treatment of certain tropical diseases, such as ruthenium compounds, known to be exogenous NO donors. In the present work, the compound cis-[Ru(bpy2SO3(NO]PF6, or RuNO, showed leishmanicidal activity directly and indirectly on promastigote forms of Leishmania (Leishmania amazonensis. In addition, treatment with RuNO increased NO production by reversing the depletion of NO caused by Leishmania. We also found increased expression of Akt, iNOS, and NF-κB in infected and treated macrophages. These results demonstrated that RuNO was able to kill the parasite by NO release and modulate the transcriptional capacity of the cell.

  2. Electrocatalytic Oxidation of Formate with Nickel Diphosphane Dipeptide Complexes. Effect of Ligands Modified with Amino Acids

    Galan, Brandon R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Reback, Matthew L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jain, Avijita [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Appel, Aaron M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shaw, Wendy J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)


    A series of nickel bis-diphosphine complexes with dipeptides appended to the ligands were investigated for the catalytic oxidation of formate. Typical rates of ~7 s-1 were found, similar to the parent complex (~8 s-1), with amino acid size and positioning contributing very little to rate or operating potential. Hydroxyl functionalities did result in lower rates, which were recovered by protecting the hydroxyl group. The results suggest that the overall dielectric introduced by the dipeptides does not play an important role in catalysis, but free hydroxyl groups do influence activity suggesting contributions from intra- or intermolecular interactions. These observations are important in developing a fundamental understanding of the affect that an enzyme-like outer coordination sphere can have upon molecular catalysts. This work was funded by the US DOE Basic Energy Sciences, Chemical Sciences, Geoscience and Biosciences Division (BRG, AJ, AMA, WJS), the US DOE Basic Energy Sciences, Physical Bioscience program (MLR). Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  3. Molybdenum Trihydride Complexes: Computational Model of Oxidatively Induced Reductive Elimination of Dihydrogen.

    Szatkowski, Lukasz; Hall, Michael B


    Recent experimental work shows that the 18-electron molybdenum complexes (1,2,4-C5H2tBu3)Mo(PMe3)2H3 (Cp(tBu)MoH3) and (C5HiPr4)Mo(PMe3)2H3 (Cp(iPr)MoH3) undergo oxidatively induced reductive elimination of dihydrogen (H2), slowly forming the 15-electron monohydride species in tetrahydrofuran and acetonitrile. The 17-electron [Cp(tBu)MoH3](+) derivative was stable enough to be characterized by X-ray diffraction, while [Cp(iPr)MoH3](+) was not. Density functional theory calculations of the H2 elimination pathways for both complexes in the gas phase and in a continuum solvent model indicate that H2 elimination from [Cp(iPr)MoH3](+) has a lower barrier than that from [Cp(tBu)MoH3](+). Further, a specific solvent association, which is stronger for [Cp(tBu)MoH3](+) than for [Cp(iPr)MoH3](+), contributes to the stability of the former. In agreement with the experimental observations, the calculations predict that [Cp(tBu)MoH3](+) would be in a quartet state at room temperature and a doublet state at 4.2 K, while [Cp(iPr)MoH3](+) is in a doublet state even at room temperature.

  4. Complex formation during dissolution of metal oxides in molten alkali carbonates

    Li, Qingfeng; Borup, Flemming; Petrushina, Irina


    Dissolution of metal oxides in molten carbonates relates directly to the stability of materials for electrodes and construction of molten carbonate fuel cells. In the present work the solubilities of PbO, NiO, Fe2O3,and Bi2O3 in molten Li/K carbonates have been measured at 650 degrees C under...... carbon dioxide atmosphere. It is found that the solubilities of NiO and PbO decrease while those of Fe2O3 and Bi2O3 remain approximately constant as the lithium mole fraction increases from 0.43 to 0.62 in the melt. At a fixed composition of the melt, NiO and PbO display both acidic and basic dissolution...... as the partial pressure of carbon dioxide varies. By combination of solubility and electromotive force measurements, a model is constructed assuming the dissolution involves complex formation. The possible species for lead are proposed to be [Pb(CO3)(2)](-2) and/or [Pb(CO3)(3)](-4). A similar complex chemistry...

  5. Cyclopentadienyl molybdenum(II/VI) N-heterocyclic carbene complexes: Synthesis, structure, and reactivity under oxidative conditions

    Li, Shenyu


    A series of N-heterocyclic carbene (NHC) complexes CpMo(CO) 2(NHC)X (NHC = IMe = 1,3-dimethylimidazol-2-ylidene, X = Br, 1; NHC = 1,3-dipropylimidazol-2-ylidene, X = Br, 2; NHC = IMes = 1,3-bis(2,4,6- trimethylphenyl)imidazol-2-ylidene, X = Br, 3; NHC = IBz = 1,3-dibenzylimidazol- 2-ylidene, X = Br, 4a, and X = Cl, 4b; NHC = 1-methyl-3-propylimidazol-2- ylidene, X = Br, 5) and [CpMo(CO)2(IMes)(CH3CN)][BF 4] (6) have been synthesized and fully characterized. The stability of metal-NHC ligand bonds in these compounds under oxidative conditions has been investigated. The thermally stable Mo(VI) dioxo NHC complex [CpMoO 2(IMes)][BF4] (9) has been isolated by the oxidation of the ionic complex 6 by TBHP (tert-butyl hydrogen peroxide). Complex 6 can be applied as a very active (TOFs up to 3400 h-1) and selective olefin epoxidation catalyst. While under oxidative conditions (in the presence of TBHP), compounds 1-5 decompose into imidazolium bromide and imidazolium polyoxomolybdate. The formation of polyoxomolybdate as oxidation products had not been observed in a similar epoxidation catalyzed by Mo(II) and Mo(VI) complexes. DFT studies suggest that the presence of Br- destabilizes the CpMo(VI) oxo NHC carbene species, consistent with the experimental observations. © 2010 American Chemical Society.

  6. On the Resolution of Secondary Phosphine Oxides via Diastereomeric Complex Formation : The Case of tert-Butylphenylphosphine Oxide

    Holt, Jarle; Maj, Anna M.; Schudde, Ebe P.; Pietrusiewicz, K. Michal; Sieron, Lelsaw; Wieczorek, Wanda; Jerphagnon, Thomas; Arends, Isabel W. C. E.; Hanefeld, Ulf; Minnaard, Adriaan J.


    The secondary phosphine oxide, t-BuPhHP=O most prominent chiral member of this compound class, has been re solved in high yield and with excellent ee. This resolution discloses ail efficient route to enantiopure phosphorus compounds.

  7. Systematic coordination chemistry and cytotoxicity of copper(II) complexes with methyl substituted 4-nitropyridine N-oxides.

    Puszko, Aniela; Brzuszkiewicz, Anna; Jezierska, Julia; Adach, Anna; Wietrzyk, Joanna; Filip, Beata; Pełczynska, Marzena; Cieslak-Golonka, Maria


    Three new nitrato copper(II) complexes of dimethyl substituted 4-nitropyridine N-oxide were synthesized and characterized by elemental analysis, magnetic, spectroscopic, thermal and X-ray methods, respectively. They were isolated as trans isomers, mononuclear (μ=1.70-1.88 BM), five (1-2) and four (3) coordinate species of general formula [Cu(NO3)2(H2O)L2] where L=2,3-dimethyl-, 2,5-dimethyl-4-nitropyridine N-oxide and [Cu (NO3)2L2], L=3,5-dimethyl-4-nitropyridine N-oxide, respectively. The X-ray crystal structure of (1) (L=2,3-dimethyl-4-nitropyridine N-oxide) was determined. The organic ligands, the complexes and copper hexaqua ion as a reference were tested in vitro on the cytotoxic activity against human cancer cell lines: MCF-7 (breast), SW-707 (colon) and P-388 (murine leukemia). The complexes are relatively strong cytotoxic agents towards P-388 cell line. Comparative analysis was performed for all known copper(II) complexes containing methyl derivatives of the 4-nitropyridine N-oxide on the basis of their composition, structure and cytotoxic activities. To obtain the typical structure for these species (i.e., 4-coordinate mononuclear of the type trans-[Cu(inorganic anion)2L2]), two methyl groups must be situated on both sides of nitrogen atom(s) (i.e., NO and NO2) in the ligand. The biological activity was found to be strongly dependent upon the number of the methyl groups and the type of cell line. The best cytotoxic results were found for the complexes without substituents or with one methyl group. Generally, for all cell lines, the complexation increased cytotoxicity when compared with the free ligands.

  8. Aberration-corrected scanning transmission electron microscopy for complex transition metal oxides

    Qing-Hua, Zhang; Dong-Dong, Xiao; Lin, Gu


    Lattice, charge, orbital, and spin are the four fundamental degrees of freedom in condensed matter, of which the interactive coupling derives tremendous novel physical phenomena, such as high-temperature superconductivity (high-T c SC) and colossal magnetoresistance (CMR) in strongly correlated electronic system. Direct experimental observation of these freedoms is essential to understanding the structure-property relationship and the physics behind it, and also indispensable for designing new materials and devices. Scanning transmission electron microscopy (STEM) integrating multiple techniques of structure imaging and spectrum analysis, is a comprehensive platform for providing structural, chemical and electronic information of materials with a high spatial resolution. Benefiting from the development of aberration correctors, STEM has taken a big breakthrough towards sub-angstrom resolution in last decade and always steps forward to improve the capability of material characterization; many improvements have been achieved in recent years, thereby giving an in-depth insight into material research. Here, we present a brief review of the recent advances of STEM by some representative examples of perovskite transition metal oxides; atomic-scale mapping of ferroelectric polarization, octahedral distortions and rotations, valence state, coordination and spin ordering are presented. We expect that this brief introduction about the current capability of STEM could facilitate the understanding of the relationship between functional properties and these fundamental degrees of freedom in complex oxides. Project supported by the National Key Basic Research Project, China (Grant No. 2014CB921002), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB07030200), and the National Natural Science Foundation of China (Grant Nos. 51522212 and 51421002).

  9. Synthesis, characterization, and crystal structure of mercury(II) complex containing new phosphine oxide salt

    Samiee, Sepideh; Kooti, Nadieh; Gable, Robert W.


    The reaction of new phosphonium-phosphine oxide salt [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]Br (1) with mercury(II) iodide in a methanolic solution yielded [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]2[Hg2I5Br](2). These two compounds were fully characterized by elemental analysis, IR, 1H, 31P, and 13C NMR spectra. Crystal and molecular structure of 2 has been determined by means of X-ray diffraction. In mercury compound, the phosphine oxide salt is found as a counter ion letting the mercury(II) ion to bound halides to all four coordination sites and to give dimermercurate(II) ions as the structure-constructing species. The neighboring [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]2+cations are joined together by intramolecular Csbnd H⋯O hydrogen bonds to give a 1-D chain structure along the crystallographic b-axis. The [Hg2I5Br]2-anions act as cross-linkers between neighbouring strands extending the supramolecular structure into 2D layers in (110) planes as well as balances the charge of the complex. The significant effects of Csbnd H⋯X (Xdbnd O, Br and I) and π⋯π aromatic interactions play a major role in the crystal packing of compound 2.

  10. Cytotoxic and Nitric Oxide Inhibition Activities of Propolis Extract along with Microencapsulation by Complex Coacervation.

    Onbas, Rabia; Kazan, Aslihan; Nalbantsoy, Ayse; Yesil-Celiktas, Ozlem


    In this study, cytotoxicity of ethanol extract of propolis (EEP) originating from Sivas, Turkey was screened against several cancer cell lines, namely PC-3, U87MG, A-549, mPANC96, CaCo-2, MCF-7, HeLa, MDA-MB-231 and a non-tumor cell line HEK293 by MTT assay. The inhibition levels of inducible nitric oxide synthase (iNOS) were also determined by using RAW 264.7 macrophage cells following lipopolysaccharide (LPS) treatment. EEP exhibited significant cytotoxic nitric oxide inhibition activities with an IC50 value of 0.1 ± 0.1 μg/ml indicating a high potential as an anti-inflammatory agent. In spite of these promising results and the fact that propolis is a highly nutritive substance, its low solubility and bitter taste limit the applications as a natural supplement. Encapsulation might serve as a good strategy in order to overcome these problems. Complex coacervation was applied where the main focus was on surfactant type, polymer ratio (alginate:gelatin), stirring rate and concentration of core material. The mean particle size of unloaded microparticles were 22.62 μm obtained with gelatin:alginate ratio of 1:1 at a stirring rate of 1400 rpm with 2 ml of 1 % (w/v) sodium carboxymethyl cellulose (Na-CMC), whereas addition of EEP at a concentration of 100 mg/ml increased the mean particle size to 36.44 μm and yielded an encapsulation efficiency of 98.77 %. The cytotoxicities of EEP loaded microparticles were also assessed both on MCF-7 and MDA-MB-231 where similar results were achieved as free EEP which can enhance the possible use of propolis extract in the industry as a natural supplement.

  11. Sulfur Versus Iron Oxidation in an Iron-Thiolate Model Complex

    A McDonald; M Bukowski; E Farquhar; T Jackson; K Koehntop; M Seo; R De Hont; A Stubna; J Halfen; E Munck


    In the absence of base, the reaction of [Fe{sup II}(TMCS)]PF{sub 6} (1, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) with peracid in methanol at -20 C did not yield the oxoiron(IV) complex (2, [Fe{sup IV}(O)(TMCS)]PF{sub 6}), as previously observed in the presence of strong base (KO{sup t}Bu). Instead, the addition of 1 equiv of peracid resulted in 50% consumption of 1. The addition of a second equivalent of peracid resulted in the complete consumption of 1 and the formation of a new species 3, as monitored by UV-vis, ESI-MS, and Moessbauer spectroscopies. ESI-MS showed 3 to be formulated as [Fe{sup II}(TMCS) + 2O]{sup +}, while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe-O = 1.95 {angstrom}, Fe-S = 3.26 {angstrom}). The addition of a third equivalent of peracid resulted in the formation of yet another compound, 4, which showed electronic absorption properties typical of an oxoiron(IV) species. Moessbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe{double_bond}O = 1.64 {angstrom}) and resonance Raman ({nu}{sub Fe{double_bond}O} = 831 cm{sup -1}) showed that indeed an oxoiron(IV) unit had been generated in 4. Furthermore, both infrared and Raman spectroscopy gave indications that 4 contains a metal-bound sulfinate moiety ({nu}{sub s}(SO{sub 2}) {approx} 1000 cm{sup -1}, {nu}{sub as}(SO{sub 2}) {approx} 1150 cm{sup -1}). Investigations into the reactivity of 1 and 2 toward H{sup +} and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which 2 could form even in the absence of base but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of 2 to 3.

  12. Influence of Ligand Architecture in Tuning Reaction Bifurcation Pathways for Chlorite Oxidation by Non-Heme Iron Complexes

    Barman, Prasenjit; Faponle, Abayomi S; Vardhaman, Anil Kumar; Angelone, Davide; Löhr, Anna-Maria; Browne, Wesley R; Comba, Peter; Sastri, Chivukula V; de Visser, Sam P


    Reaction bifurcation processes are often encountered in the oxidation of substrates by enzymes and generally lead to a mixture of products. One particular bifurcation process that is common in biology relates to electron transfer versus oxygen atom transfer by high-valent iron(IV)-oxo complexes, whi

  13. Influence of Ligand Architecture in Tuning Reaction Bifurcation Pathways for Chlorite Oxidation by Non-Heme Iron Complexes

    Barman, Prasenjit; Faponle, Abayomi S; Vardhaman, Anil Kumar; Angelone, Davide; Löhr, Anna-Maria; Browne, Wesley R; Comba, Peter; Sastri, Chivukula V; de Visser, Sam P


    Reaction bifurcation processes are often encountered in the oxidation of substrates by enzymes and generally lead to a mixture of products. One particular bifurcation process that is common in biology relates to electron transfer versus oxygen atom transfer by high-valent iron(IV)-oxo complexes,

  14. Homogeneous water oxidation by half-sandwich iridium(III)NHC complexes with pendant hydroxy and amino groups.

    Mahanti, Bani; González Miera, Greco; Martínez-Castro, Elisa; Bedin, Michele; Martín-Matute, Belén; Ott, Sascha; Thapper, Anders


    Herein we report three Ir(III)Cp* complexes with hydroxy- (1, 2) or amino- (3) functionalized N-heterocyclic carbene (NHC) ligands as catalysts for efficient water oxidation induced by addition of ceric ammonium nitrate (CAN). The pendant hydroxy- or amino- groups are very important for activity and the complexes with heteroatom-functionalized NHC ligands show up to 15 times higher rate of oxygen evolution in CAN-induced water oxidation compared to a reference Ir(III)Cp* complex without heteroatom functionalization (4). The presence of molecular high-valent Ir intermediates that are presumably involved in the rate-determining step for water oxidation is established by UV-vis spectroscopic and ESI mass spectrometric analyses during turnover conditions. The hydroxy-groups on the NHC ligands, as well as chloride ligands on the iridium center are proposed to structurally stabilize the high-valent species, and thereby improve the catalytic activity. The Ir(III) complex 1 with a hydroxy-functionalized NHC shows the highest catalytic activity with a TON of 2500 obtained in 3 h and with >90% yield relative to the amount of used oxidant. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. 含铋复合氧化物催化剂的研究进展%Research progress in bismuth-containing complex oxide catalysts

    王鹏; 陈晓晖; 魏可镁


    Bismuth-containing complex oxides is an research hotspot of selective oxidation and photocatalysis at present. Bismuth oxide can combine with titanium oxide, vanadium oxide, iron oxide, copper oxide,molybdenum oxide ,silicon oxide and tungsten oxide to form bismuth-containing complex oxide catalysts.The research advance on bismuth-containing complex oxide catalysts was reviewed. The research aspects of bismuth-containing complex oxide catalysts in the future were outlined.%含铋复合金属氧化物是当前选择性氧化和光催化方面的研究热点.主要介绍了近年来氧化铋与氧化钛、氧化钒、氧化铁、氧化铜、氧化钼、氧化硅和氧化钨等的复合氧化物催化剂的研究进展,并指出了含铋复合氧化物今后的研究方向.

  16. Base-Free Selective Oxidation of Glycerol over LDH Hosted Transition Metal Complexes Using 3% H2O2 as Oxidant

    Xiaoli Wang


    Full Text Available A series of transition metal sulphonato-Schiff base complexes were intercalated into Mg–Al layered-double hydroxides (LDHs. The obtained catalysts were characterized by FTIR, XRD, N2 sorption, SEM and elemental analysis, and then were used in the selective oxidation of glycerol (GLY using 3% H2O2 as an oxidant. It was found that their catalytic performances were closely related to the loading of active complexes, the Schiff base ligands and the metal centers of the catalysts, as well as the reaction conditions. The optimal conversion of GLY was 85.0%, while the selectivity of 1,3-dihydroxyacetone (DHA was 56.5%. Moreover, the catalysts could be reused at least 10 times.

  17. Hydroxo-bridged dicopper(II,III) and -(III,III) complexes: models for putative intermediates in oxidation catalysis.

    Halvagar, Mohammad Reza; Solntsev, Pavlo V; Lim, Hyeongtaek; Hedman, Britt; Hodgson, Keith O; Solomon, Edward I; Cramer, Christopher J; Tolman, William B


    A macrocyclic ligand (L(4-)) comprising two pyridine(dicarboxamide) donors was used to target reactive copper species relevant to proposed intermediates in catalytic hydrocarbon oxidations by particulate methane monooxygenase and heterogeneous zeolite systems. Treatment of LH4 with base and Cu(OAc)2·H2O yielded (Me4N)2[L2Cu4(μ4-O)] (1) or (Me4N)[LCu2(μ-OH)] (2), depending on conditions. Complex 2 was found to undergo two reversible 1-electron oxidations via cyclic voltammetry and low-temperature chemical reactions. On the basis of spectroscopy and theory, the oxidation products were identified as novel hydroxo-bridged mixed-valent Cu(II)Cu(III) and symmetric Cu(III)2 species, respectively, that provide the first precedence for such moieties as oxidation catalysis intermediates.

  18. Solubilization of silica: Synthesis, characterization and study of penta-coordinated pyridine N-oxide silicon complexes

    Subramania Ranganathan; Ch Chandrashekhar Rao; Suvarchala Devi Vudayagiri; Y B R D Rajesh; B Jagadeesh


    In an effort to design agents that could solubilize silica in water, under ambient conditions and pH, as takes place in nature, novel zwitterionic, penta-oxo-coordinated silicon compounds with siliconate cores have been prepared from 4-substituted pyridine N-oxides (H, OMe, morpholino, NO2) as donor ligands, their structures established by 1H, 13C and MS, and the coordination number of silicon, by 29Si NMR. The formation of complexes from pyridine N-oxides is noteworthy since they arise from interaction with a weakly nucleophilic oxygen centre. The ability of the pyridine N-oxides to enhance the solubilization of silica in water has been experimentally demonstrated. Possible rationalization of this observation on the basis of O→Si coordination via the oxygen atom of pyridine N-oxide is suggested.

  19. Coordination functionalization of graphene oxide with tetraazamacrocyclic complexes of nickel(II): Generation of paramagnetic centers

    Basiuk, Vladimir A., E-mail: [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F. (Mexico); Department of Chemistry,Tufts University, 62 Talbot Avenue, Medford, MA 02155 (United States); Alzate-Carvajal, Natalia [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F. (Mexico); Henao-Holguín, Laura V. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F. (Mexico); Rybak-Akimova, Elena V. [Department of Chemistry,Tufts University, 62 Talbot Avenue, Medford, MA 02155 (United States); Basiuk, Elena V., E-mail: [Department of Chemistry,Tufts University, 62 Talbot Avenue, Medford, MA 02155 (United States); Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510 México D.F. (Mexico)


    Highlights: • [Ni(cyclam)]{sup 2+} and [Ni(tet b)]{sup 2+} cations coordinate to carboxylic groups of GO. • The coordination takes place under basic conditions in aqueous-based medium. • The coordination results in the conversion from low-spin to high-spin Ni(II). • Functionalized GO samples were characterized by various instrumental techniques. - Abstract: We describe a novel approach to functionalization of graphene oxide (GO) which allows for a facile generation of paramagnetic centers from two diamagnetic components. Coordination attachment of [Ni(cyclam)]{sup 2+} or [Ni(tet b)]{sup 2+} tetraazamacrocyclic cations to carboxylic groups of GO takes place under basic conditions in aqueous-based reaction medium. The procedure is very straightforward and does not require high temperatures or other harsh conditions. Changing the coordination geometry of Ni(II) from square-planar tetracoordinated to pseudooctahedral hexacoordinated brings about the conversion from low-spin to high-spin state of the metal centers. Even though the content of tetraazamacrocyclic complexes in functionalized GO samples was found to be relatively low (nickel content of ca. 1 wt%, as determined by thermogravimetric analysis, elemental analysis and energy dispersive X-ray spectroscopy), room temperature magnetic susceptibility measurements easily detected the appearance of paramagnetic properties in GO + [Ni(cyclam)] and GO + [Ni(tet b)] nanohybrids, with effective magnetic moments of 1.95 BM and 2.2 BM for, respectively. According to density functional theory calculations, the main spin density is localized at the macrocyclic complexes, without considerable extension to graphene sheet, which suggests insignificant ferromagnetic coupling in the nanohybrids, in agreement with the results of magnetic susceptibility measurements. The coordination attachment of Ni(II) tetraazamacrocycles to GO results in considerable changes in Fourier-transform infrared and X-ray photoelectron spectra

  20. Upon oxidative stress, the antiapoptotic Hsp60/procaspase-3 complex persists in mucoepidermoid carcinoma cells

    C Campanella


    Full Text Available Hsp60, a mitochondrial chaperonin highly conserved during evolution, has been found elevated in the cytosol of cancer cells, both in vivo and in vitro, but its role in determining apoptosis during oxidative stress (OS has not yet been fully elucidated. The aim of the present work was to study the effects of OS on Hsp60 levels and its interactions with procaspase- 3 (p-C3 and p53 in tumor cells. NCI-H292 (mucoepidermoid carcinoma cells were exposed to various concentrations of hydrogen peroxide (H2O2 for 24 hours. Cell viability was determined by Trypan blue and MTT assays. DNA damage was assessed by the Comet assay, and apoptosis was measured by the AnnexinV cytofluorimetric test. Exposure to increasing concentrations of H2O2 resulted in a reduction of cell viability, DNA damage, and early apoptotic phenomena. Hsp60, p-C3, p53, and p21 were assessed by Western blotting and immunocytochemistry before and after OS. Hsp60 and p-C3 were present before and after OS induction. Immunoprecipitation experiments showed an Hsp60/p-C3 complex before OS that persisted after it, while an Hsp60/p53 complex was not detected in either condition. The presence of wild type (wt p53 was confirmed by RT-PCR, and p21 detection suggested p53 activation after OS. We postulate that, although OS may induce early apoptosis in NCI-H292 cells, Hsp60 exerts an anti-apoptotic effect in these cells and, by extension, it may do so in other cancer cells.

  1. Structural Studies of a Complex Between Endothelial Nitric Oxide Synthase and Calmodulin at Physiological Calcium Concentration.

    Piazza, Michael; Dieckmann, Thorsten; Guillemette, Joseph Guy


    The small acidic protein Calmodulin (CaM) serves as a Ca(2+) sensor and control element for many enzymes including nitric oxide synthase (NOS) enzymes that play major roles in key physiological and pathological processes. CaM binding causes a conformational change in NOS to allow for the electron transfer between the reductase and oxygenase domains through a process that is thought to be highly dynamic. In this report, NMR spectroscopy was used to determine the solution structure of the endothelial NOS (eNOS) peptide in complex with CaM at the lowest Ca(2+) concentration (225 nM) required for CaM to bind to eNOS and corresponds to a physiological elevated Ca2+ level found in mammalian cells. Under these conditions, the CaM-eNOS complex has a Ca(2+)-replete C-terminal lobe bound the eNOS peptide and a Ca(2+) free N-terminal lobe loosely associated to the eNOS peptide. With increasing Ca(2+) concentration, the binding of Ca(2+) by the N-lobe of CaM results in a stronger interaction with the C-terminal region of the eNOS peptide and increased α-helical structure of the peptide that may be part of the mechanism resulting in electron transfer from the FMN to the heme in the oxygenase domain of the enzyme. SPR studies performed under the same conditions show Ca(2+) concentration dependent binding kinetics were consistent with the NMR structural results. This investigation shows that structural studies performed under more physiological relevant conditions provide information on subtle changes in structure that may not be apparent when experiments are performed in excess Ca(2+) concentrations.

  2. Synthesis and transformations of alkylphosphate and alkoxysiloxide metal complexes to multicomponent oxide materials

    Lugmair, Claus Guenter

    This thesis describes the synthesis of mixed element oxide materials utilizing oxygen rich ``single-source precursor'' molecules. The key attributes of these precursor complexes are that they possess the stoichiometry of the targeted oxide material and that they can be converted to carbon free materials by mild thermal treatment. Complexes of Al, Cu, Fe, Hf, Nb, Ta, Ti, and Zr were prepared that contain tris(tert-butoxy)siloxy ligands as precursors to silica based materials. The pyrolytic decomposition of these complexes occur under mild conditions, with onset temperatures to decomposition between 95 and 200sp°C. The resulting metal-silica or metal oxide-silica materials contain very little carbon. The solid state transformation of Zrlbrack OSi(OsptBu)sb3rbracksb4 to ZrOsb2{*}4SiOsb2 produced an open fibrous material with pores which are ca. 20 nm in diameter. The solution phase thermolysis of the various metal siloxide complexes in anhydrous organic solvents led to xerogels consisting of small spherical primary particles (≤ca. 5 nm). These xerogels typically possess very high surface areas. The ZrOsb2{*}4SiOsb2 materials are amorphous as initially formed, and subsequent crystallizations of tetragonal ZrOsb2, monoclinic ZrOsb2, and cristobalite occur at relatively high temperatures. The enhanced stabilization of the amorphous and tetragonal phases of zirconia, relative to those derived from many sol-gel systems, implies that these single-source precursors initially produce highly homogeneous materials and that subsequent crystallizations are to a large degree diffusion-controlled, Careful addition of 1 or 2 equiv of water to THF solutions of Mlbrack OSi(OsptBu)sb3rbracksb4 (M = Zr, Hf) produced the isolable aqua complexes Mlbrack OSi(OsptBu)sb3rbracksb4(Hsb2O) and Mlbrack OSi(OsptBu)sb3rbracksb4(Hsb2O)sb2. It is likely that the hydrolysis of Zrlbrack OSi(OsptBu)sb3rbracksb4(Hsb2O)sb2 also occurs by an associative mechanism via the tris(aqua) intermediate

  3. A Method for Atomic Layer Deposition of Complex Oxide Thin Films


    5 2.1.1 Effect of Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Ferroelectricity ...potential ma- terials. One example is the field of high-k dielectric oxides, such as hafnium oxide ( HfO2 ) and zirconium oxide (ZrO2), 1,2 which are allowing...consumers have become accustomed to.3 The class of ferroelectric oxides comprises the family of materials that this thesis will consider. One material in

  4. Enhanced photoefficiency in positive-tone direct patterning of metal complexes for forming patterned indium tin oxide films

    Cordonier, Christopher E.J., E-mail:; Nakamura, Akimasa; Shimada, Kazuhiko; Fujishima, Akira


    The efficiency of positive-tone directly photo-patternable 4-(2-nitrobenzyloxycarbonyl)catechol and 4-(6-nitroveratryloxycarbonyl)catechol complexes of indium tin was improved by tuning the solubility of the complexes and by chelation of maltol as a cooperative photo-solvolytic component, such that films could be patterned at up to 4.88 mW{center_dot}s/nm in terms of resultant indium tin oxide (ITO). Patterned indium tin complexes were thermally transformed to pattern shape preserved ITO by anisotropic contraction and oxidation. The photo-reaction of these ligands and related derivatives was characterized by nuclear magnetic resonance analysis showing decomposition to the respective carboxylic acid for which linear rate constants were approximated, further elucidating the mechanism and mechanics of selective solubility. - Highlights: Black-Right-Pointing-Pointer Photoreaction of ortho-nitrobenzyl dioxybenzoate derivatives was investigated. Black-Right-Pointing-Pointer Tuning the photolabile ester-indium tin complex increased film photoefficiency. Black-Right-Pointing-Pointer A photoreaction of chelated maltol was also found to aid performance. Black-Right-Pointing-Pointer Complexes coated once gave patterned 8.35 Multiplication-Sign 10{sup -4} {Omega}{center_dot}cm indium tin oxide films.

  5. Interplay among nitric oxide and reactive oxygen species: a complex network determining cell survival or death.

    Zhao, Jian


    Programmed cell death (PCD) is an integrated cellular process occurring in plant growth, development, and defense responses to facilitate normal growth and development and better survival against various stresses as a whole. As universal toxic chemicals in plant and animal cells, reactive oxygen or nitrogen species (ROS or RNS), mainly superoxide anion (O(2) (-*)), hydrogen peroxide (H(2)O(2)) or nitric oxide ((*)NO), have been studied extensively for their roles in PCD induction. Physiological and genetic studies have convincingly shown their essential roles. However, the details and mechanisms by which ROS and (*)NO interplay and induce PCD are not well understood. Our recent study on Cupressus lusitanica culture cell death revealed the elicitor-induced co-accumulation of ROS and (*)NO and interactions between (*)NO and H(2)O(2) or O(2)-(*) in different ways to regulate cell death. (*)NO and H(2)O(2) reciprocally enhanced the production of each other whereas (*)NO and O(2) (-*) showed reciprocal suppression on each other's production. It was the interaction between (*)NO and O(2)-(*) but not between (*)NO and H(2)O(2) that induced PCD, probably through peroxynitrite (ONOO(-)). In this addendum, some unsolved issues in the study were discussed based on recent studies on the complex network of ROS and (*)NO leading to PCD in animals and plants.

  6. Thermodynamic properties of complex oxides in the La Ni O system

    Bannikov, D. O.; Cherepanov, V. A.


    Complex oxides La 2NiO 4+δ, La 3Ni 2O 7-δ, La 4Ni 3O 10-δ and LaNiO 3-δ, the members of Ruddlesden-Popper series La n+1Ni nO 3n+1, were prepared using citrate precursors. The stability range of LaNiO 3-δ in air as well as the oxygen nonstoichiometry of La 3Ni 2O 7-δ and La 4Ni 3O 10-δ as a function of temperature and oxygen partial pressure was determined by means of thermogravimetric technique. Decomposition temperatures of La 3Ni 2O 7-δ, La 4Ni 3O 10-δ and LaNiO 3-δ in air were determined by conductivity measurement method. The boundary of stability for La 4Ni 3O 10-δ was determined by EMF measurements of galvanic cell with oxygen conducting solid electrolyte. The isothermal (1400 K) projection of La-Ni-O system phase diagram to the plane "log( PO 2)-relative mole fraction of metal components" was suggested.

  7. Percolation via Combined Electrostatic and Chemical Doping in Complex Oxide Films

    Orth, Peter P.; Fernandes, Rafael M.; Walter, Jeff; Leighton, C.; Shklovskii, B. I.


    Stimulated by experimental advances in electrolyte gating methods, we investigate theoretically percolation in thin films of inhomogeneous complex oxides, such as La1 -xSrxCoO3 (LSCO), induced by a combination of bulk chemical and surface electrostatic doping. Using numerical and analytical methods, we identify two mechanisms that describe how bulk dopants reduce the amount of electrostatic surface charge required to reach percolation: (i) bulk-assisted surface percolation and (ii) surface-assisted bulk percolation. We show that the critical surface charge strongly depends on the film thickness when the film is close to the chemical percolation threshold. In particular, thin films can be driven across the percolation transition by modest surface charge densities. If percolation is associated with the onset of ferromagnetism, as in LSCO, we further demonstrate that the presence of critical magnetic clusters extending from the film surface into the bulk results in considerable enhancement of the saturation magnetization, with pronounced experimental consequences. These results should significantly guide experimental work seeking to verify gate-induced percolation transitions in such materials.

  8. Microwave-Assisted Routes for the Synthesis of Complex Functional Oxides

    Jesús Prado-Gonjal


    Full Text Available The synthesis of complex functional inorganic materials, such as oxides, can be successfully performed by using microwave irradiation as the source of heat. To achieve this, different routes and set-ups can be used: microwave-assisted synthesis may proceed in the solid state or in solution, aqueous or not, and the set ups may be as simple and accessible as domestic oven or quite sophisticated laboratory equipment. An obvious advantage of this innovative methodology is the considerable reduction in time—minutes rather than hours or days—and, as a consequence, energy saving. No less important is the fact that the particle growth is inhibited and the broad variety of different microwave or microwave-assisted synthesis techniques opens up opportunities for the preparation of inorganic nanoparticles and nanostructures. In this work, various microwave synthesis techniques have been employed: solid-state microwaves, single-mode microwaves using a TE10p cavity and microwave-assisted hydrothermal synthesis. Relevant examples are presented and discussed.

  9. Wet air oxidation as a pretreatment option for selective biodegradability enhancement and biogas generation potential from complex effluent.

    Padoley, K V; Tembhekar, P D; Saratchandra, T; Pandit, A B; Pandey, R A; Mudliar, S N


    This study looks at the possibility of wet air oxidation (WAO) based pretreatment of complex effluent to selectively enhance the biodegradability (without substantial COD destruction) and facilitate biogas generation potential. A lab-scale wet air oxidation reactor with biomethanated distillery wastewater (B-DWW) as a model complex effluent (COD 40,000 mg L(-1)) was used to demonstrate the proof-of-concept. The studies were conducted using a designed set of experiments and reaction temperature (150-200°C), air pressure (6-12 bar) and reaction time (15-120 min) were the main process variables of concern for WAO process optimization. WAO pretreatment of B-DWW enhanced the biodegradability of the complex wastewater by the virtue of enhancing its biodegradability index (BI) from 0.2 to 0.88, which indicate favorable Biochemical Methane Potential (BMP) for biogas generation. The kinetics of COD destruction and BI enhancement has also been reported.

  10. Making oxidation potentials predictable: Coordination of additives applied to the electronic fine tuning of an iron(II) complex

    Haslinger, Stefan


    This work examines the impact of axially coordinating additives on the electronic structure of a bioinspired octahedral low-spin iron(II) N-heterocyclic carbene (Fe-NHC) complex. Bearing two labile trans-acetonitrile ligands, the Fe-NHC complex, which is also an excellent oxidation catalyst, is prone to axial ligand exchange. Phosphine- and pyridine-based additives are used for substitution of the acetonitrile ligands. On the basis of the resulting defined complexes, predictability of the oxidation potentials is demonstrated, based on a correlation between cyclic voltammetry experiments and density functional theory calculated molecular orbital energies. Fundamental insights into changes of the electronic properties upon axial ligand exchange and the impact on related attributes will finally lead to target-oriented manipulation of the electronic properties and consequently to the effective tuning of the reactivity of bioinspired systems.

  11. Matrix isolation infrared spectroscopic and theoretical study of the copper (I) and silver (I) nitrous oxide complexes

    Wang, Guanjun; Jin, Xi; Chen, Mohua; Zhou, Mingfei


    Copper and silver chloride-nitrous oxide complexes: ClCuNNO and ClAgNNO have been produced and trapped in solid argon by co-deposition of laser-evaporated metal chlorides with nitrous oxide in excess argon. On the basis of isotopic substituted experiments as well as theoretical calculations, infrared absorptions at 2305.8 and 1318.4 cm -1, and 2291.2 and 1325.4 cm -1 are assigned to the N-N and N-O stretching modes of the linear ClCuNNO and ClAgNNO complexes, respectively. The binding energies for the complexes with respect to MCl (M = Cu, Ag) and N 2O were computationally estimated to be 27.9 and 13.1 kcal/mol.

  12. New insights into the chemical structure of Y2Ti2O7-δ nanoparticles in oxide dispersion-strengthened steels designed for sodium fast reactors by electron energy-loss spectroscopy

    Badjeck, V.; Walls, M. G.; Chaffron, L.; Malaplate, J.; March, K.


    In this paper we study by high resolution scanning transmission electron microscopy coupled with electron energy-loss spectroscopy (STEM-EELS) an oxide dispersion-strengthened (ODS) steel with the nominal composition Fe-14Cr-1W-0.3TiH2-0.3Y2O3 (wt.%) designed to withstand the extreme conditions met in Gen. IV nuclear reactors. After denoising via principal component analysis (PCA) the data are analyzed using independent component analysis (ICA) which is useful in the investigation of the physical properties and chemical structure of the material by separating the individual spectral responses. The Y-Ti-O nanoparticles are found to be homogeneously distributed in the ferritic matrix, sized from 1 to 20 nm and match a non-stoichiometric pyrochlore-Y2Ti2O7-δ structure for sizes greater than 5 nm. We show that they adopt a (Y-Ti-O)-Cr core-shell structure and that Cr also segregates at the matrix grain boundaries, which may slightly modify the corrosion properties of the steel. Using Ti-L2,3 and O-K fine structure (ELNES) the Ti oxidation state is shown to vary from the center of the nanoparticles to their periphery, from Ti4+ in distorted Oh symmetry to a valency often lower than 3+. The sensitivity of the Ti "white lines" ELNES to local symmetry distortions is also shown to be useful when investigating the strain induced in the nanoparticles by the surrounding matrix. The Cr-shell and the variation of the Ti valence state highlight a complex nanoparticle-matrix interface.

  13. Theoretical investigation of water oxidation processes on small Mn(x)Ti(2-x)O4 (x = 0-2) complexes.

    Lee, Choongkeun; Aikens, Christine M


    Understanding the water oxidation process on small metal oxide complexes is fundamental for developing photocatalysts for solar fuel production. Titanium oxide and manganese oxide complexes have high potential as components of a cheap, nontoxic, and stable photocatalyst. In this theoretical work, the water oxidation process on Mn(x)Ti(2-x)O4 (x = 0-2) clusters is investigated at the BP86 level of theory using two water molecules and fully saturated systems. In the oxidation cycle using two water molecules, Mn reduces the reaction energy; however, Mn does not reduce the reaction energy on the fully saturated system. When two water molecules are used, the highest reaction energy in the water oxidation cycle is lower than 3 eV, but the highest reaction energy is higher than 3 eV on fully saturated systems except for the pure titanium oxide complex which has a highest reaction energy of 2.56 eV. Dehydrogenation processes in the water oxidation cycle require higher energy than the O-O formation or water adsorption processes. The overall dehydrogenation energy is usually smaller on complexes including at least one Mn atom and it is smallest on the Mn2O4 complex that has two water molecules. Considering the highest reaction energy in the overall water oxidation cycle, water oxidation at the manganese atom of MnTiO4 hydrated with two water molecules is the most favorable in energy.

  14. Hydrophilic interaction liquid chromatography-electrospray ionization-tandem mass spectrometry of a complex mixture of native and oxidized phospholipids.

    Losito, I; Facchini, L; Diomede, S; Conte, E; Megli, F M; Cataldi, T R I; Palmisano, F


    A mixture of native and oxidized phospholipids (PLs), generated by the soybean lipoxygenase type V-catalyzed partial oxidation of a lipid extract obtained from human platelets, was analyzed by Hydrophilic Interaction Liquid Chromatography-ElectroSpray Ionization-Tandem Mass Spectrometry (HILIC-ESI-MS/MS). The complexity of the resulting mixture was remarkable, considering that the starting lipid extract, containing (as demonstrated in a previous study) about 130 native PLs, was enriched with enzymatically generated hydroperoxylated derivatives and chemically generated hydroxylated forms of PLs bearing polyunsaturated side chains. Nonetheless, the described analytical approach proved to be very powerful; indeed, focusing on phosphatidylcolines (PCs), the most abundant PL class in human platelets, about fifty different native/oxidized species could be identified in a single HILIC-ESI-MS/MS run. Low-energy collision induced dissociation tandem MS (CID-MS/MS) experiments on chromatographically separated species showed single neutral losses of H2O2 and H2O to be typical fragmentation pathways of hydroperoxylated PCs, whereas a single H2O loss was observed for hydroxylated ones. Moreover, diagnostic losses of n-hexanal or n-pentanol were exploited to recognize PCs hydroperoxylated on the last but five carbon atom of a ɷ-6 polyunsaturated side chain. Despite the low resolution of the 3D ion trap mass analyzer used, the described HILIC-ESI-MS/MS approach appears very promising for the identification of oxidized lipids in oxidatively stressed complex biological systems.

  15. Synthesis and characterization of alumina-supported vanadium oxide catalysts prepared by the molecular designed dispersion of VO(acac)2 complexes

    Weckhuysen, B.M.; Baltes, M.; Voort, P. van der; Ramachandra Rao, R.; Catana, Gabriela; Schoonheydt, R.A.; Vansant, E.F.


    Alumina-supported vanadium oxide catalysts have been prepared by the molecular designed dispersion method, using the vanadyl acetylacetonate complex (VO(acac)2). The complex has been adsorbed on the support from solution, followed by thermal conversion into the corresponding supported vanadium oxide

  16. Mechanism of mechanochemical synthesis of complex oxides and the peculiarities of their nano-structurization determining sintering

    Zyryanov V.V.


    Full Text Available A mechanism of superfast mechanosynthesis reaction for oxide systems is proposed on the base of a dynamics study. The threshold effect and linear dependence of the chemical response on the effective temperature of the reaction zone are established. Major factors are determined: molecular mass of reagents, enthalpy and difference of reagents in Mohs’s hardness, which also influence the composition of the primary product. Primary acts are characterized by a superfast roller mechanism of mass transfer with the formation of a transient dynamic state (D*. Secondary acts slowly approximate the composition of the product to the composition of the starting mixture by diffusion mass transfer in a deformation mixing regime with a contribution of a rotation (roller mechanism. The list of structure types for complex oxides derived by mechanosynthesis includes perovskites, fluorites, pyrochlors, sheelites, and some other ones. Powders of crystal products display multilevel structurization. In all studied complex oxides strong disordering of the “anti-glass” type was observed. The mechanism of sintering was studied in BaTiO3 powders of different origin and in metastable complex oxides derived by mechanosynthesis. The major contribution in shrinkage belongs to rearrangements of crystalline particles as a whole. Structure transformations accompany, as a rule, sintering of inhomogeneous powders derived by mechanosynthesis.

  17. Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

    Liang, Wenchuan [Univ. of California, Berkeley, CA (United States)


    X-ray absorption spectroscopy (XAS) was performed on Photosystem II (PSII)-enriched membranes prepared from spinach to explore: (1) the correlation between structure and magnetic spin state of the Mn cluster in the oxygen evolving complex (OEC) in the S2 state; and (2) the oxidation state changes of the Mn cluster in the flash-induced S-states. The structure of the Mn cluster in the S2 state with the g~4 electron paramagnetic resonance (EPR) signal (S2-g4 state) was compared with that in the S2 state with multiline signal (S2-MLS state) and the S1 state. The S2-g4 state has a higher XAS inflection point energy than that of the S1 state, indicating the oxidation of Mn in the advance from the S1 to the S2-g4 state. Differences in the edge shape and in the extended X-ray absorption fine structure (EXAFS) show that the structure of the Mn cluster in the S2-g4 state is different from that in the S2-MLS or the S1 state. In the S2-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 Å and 2.85 Å. Very little distance disorder exists in the second shell of the S1 or S2-MLS states. The third shell of the S2-g4 state at about 3.3 Å also contains increased heterogeneity relative to that of the S2-MLS or the S1 state. Various S-states were prepared at room-temperature by saturating, single-turnover flashes. The flash-dependent oscillation in the amplitude of the MLS was used to characterize the S-state composition and to construct "pure" S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S1 → S2 transition.

  18. Tilts, dopants, vacancies and non-stoichiometry: Understanding and designing the properties of complex solid oxide perovskites from first principles

    Bennett, Joseph W.

    Perovskite oxides of formula ABO3 have a wide range of structural, electrical and mechanical properties, making them vital materials for many applications, such as catalysis, ultrasound machines and communication devices. Perovskite solid solutions with high piezoelectric response, such as ferroelectrics, are of particular interest as they can be employed as sensors in SONAR devices. Ferroelectric materials are unique in that their chemical and electrical properties can be non-invasively and reversibly changed, by switching the bulk polarization. This makes ferroelectrics useful for applications in non-volatile random access memory (NVRAM) devices. Perovskite solid solutions with a lower piezoelectric response than ferroelectrics are important for communication technology, as they function well as electroceramic capacitors. Also of interest is how these materials act as a component in a solid oxide fuel cell, as they can function as an efficient source of energy. Altering the chemical composition of these solid oxide materials offers an opportunity to change the desired properties of the final ceramic, adding a degree of flexibility that is advantageous for a variety of applications. These solid oxides are complex, sometimes disordered systems that are a challenge to study experimentally. However, as it is their complexity which produces favorable properties, highly accurate modeling which captures the essential features of the disordered structure is necessary to explain the behavior of current materials and predict favorable compositions for new materials. Methodological improvements and faster computer speeds have made first-principles and atomistic calculations a viable tool for understanding these complex systems. Offering a combination of accuracy and computational speed, the density functional theory (DFT) approach can reveal details about the microscopic structure and interactions of complex systems. Using DFT and a combination of principles from both

  19. Protective effect of polysaccharide-protein complex from a polypore mushroom, Phellinus rimosus against radiation-induced oxidative stress.

    Joseph, Jini; Panicker, Sudheesh Narayana; Janardhanan, Kainoor Krishnankutty


    Ionizing radiation induces severe oxidative stress in the body resulting an imbalance in prooxidant and antioxidant status in the cell. The aim of the present study is to investigate the protective effect of polysaccharide protein complex (PPC-Pr) isolated from the mushroom Phellinus rimosus against the oxidative stress induced by gamma radiation. PPC-Pr complex was isolated from the aqueous extracts of P. rimosus. The complex was administered to Swiss albino mice at a concentration of 5 and 10 mg/kg body weight intraperitoneally for 5 days consecutively and exposed to 4 Gy of gamma irradiation. Animals were sacrificed 1 day after irradiation and the antioxidant parameters such as glutathione, glutathione peroxidase, superoxide dismutase, catalase, glutathione reductase as well as lipid peroxidation were evaluated in both liver and brain tissues to evaluate oxidative stress. Amifostine, a standard radioprotective agent, was used as a positive control. In vitro DNA damage was assessed using the comet assay. Survival studies were also carried out to determine the protective role of PPC-Pr against radiation-induced delayed oxidative stress. PPC-Pr treatment enhanced the declined levels of antioxidants and comet parameters to a significant level, indicating its antioxidant as well as DNA protecting potential. Significant increase in the survival rate of animals was also observed in irradiated animals treated with PPC-Pr complex. The results were comparable to the standard drug amifostine. The results indicate profound effects of PPC-Pr against radiation-induced oxidative stress. The findings suggest potential therapeutic use of PPC-Pr in radiotherapy.

  20. Interplay of Experiment and Theory in Elucidating Mechanisms of Oxidation Reactions by a Nonheme Ru(IV)O Complex.

    Dhuri, Sunder N; Cho, Kyung-Bin; Lee, Yong-Min; Shin, Sun Young; Kim, Jin Hwa; Mandal, Debasish; Shaik, Sason; Nam, Wonwoo


    A comprehensive experimental and theoretical study of the reactivity patterns and reaction mechanisms in alkane hydroxylation, olefin epoxidation, cyclohexene oxidation, and sulfoxidation reactions by a mononuclear nonheme ruthenium(IV)-oxo complex, [Ru(IV)(O)(terpy)(bpm)](2+) (1), has been conducted. In alkane hydroxylation (i.e., oxygen rebound vs oxygen non-rebound mechanisms), both the experimental and theoretical results show that the substrate radical formed via a rate-determining H atom abstraction of alkanes by 1 prefers dissociation over oxygen rebound and desaturation processes. In the oxidation of olefins by 1, the observations of a kinetic isotope effect (KIE) value of 1 and styrene oxide formation lead us to conclude that an epoxidation reaction via oxygen atom transfer (OAT) from the Ru(IV)O complex to the C═C double bond is the dominant pathway. Density functional theory (DFT) calculations show that the epoxidation reaction is a two-step, two-spin-state process. In contrast, the oxidation of cyclohexene by 1 affords products derived from allylic C-H bond oxidation, with a high KIE value of 38(3). The preference for H atom abstraction over C═C double bond epoxidation in the oxidation of cyclohexene by 1 is elucidated by DFT calculations, which show that the energy barrier for C-H activation is 4.5 kcal mol(-1) lower than the energy barrier for epoxidation. In the oxidation of sulfides, sulfoxidation by the electrophilic Ru-oxo group of 1 occurs via a direct OAT mechanism, and DFT calculations show that this is a two-spin-state reaction in which the transition state is the lowest in the S = 0 state.

  1. Kinetics and mechanism of oxidation of glycine by iron(III)-1,10-phenanthroline complex in perchloric acid medium

    T V N Partha Sarathi; A Kalyan Kumar; K Krishna Kishore; P Vani


    Kinetics and mechanism of oxidation of glycine by iron(III)-1,10-phenanthroline complex has been studied in perchloric acid medium. The reaction is first order with respect to iron(III) and glycine. An increase in (phenanthroline) increases the rate, while increase in [H+] decreases the rate. Hence it can be inferred that the reactive species of the substrate is the zwitterionic form and that of the oxidant is [Fe(phen)2(H2O)2]3+. The proposed mechanism leads to the rate law as elucidated.

  2. Nitrite to nitric oxide interconversion by heme FeII complex assisted by [CuI(tmpa)]+

    Turias, Francesc


    The present computational study complements the recent experimental efforts by Karlin and coworkers to describe the interconversion of nitrite to nitric oxide by means of an iron porphyrin complex together with a Cu chemical system, i.e., the iron(II) complex (F8TPP)FeII [F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2−)] and a preformed copper(II)–nitrito complex [(tmpa)CuII(NO2)][B(C6F5)4] [tmpa = tris(2-pyridylmethyl)amine], being the latter an oxidized species of [(tmpa)CuI(MeCN)]+. By DFT calculations, we unravel how the reduction of nitrite to nitric oxide takes place through a μ-oxo heme-FeIII–O–CuII complex, following a mimetic path as in the cytochrome c oxidase. Mayer bond order (MBO) and energy decomposition analyses are used to analyze the bonding strength of such nitro derivatives to either copper or iron. © 2015 Springer Science+Business Media New York

  3. Chitosan-based Schiff base-metal complexes (Mn, Cu, Co) as heterogeneous, new catalysts for the -isophorone oxidation

    C S Thatte; M V Rathnam; A C Pise


    A new chitosan-based Schiff base was prepared and complexed with manganese, cobalt and copper. These Schiff base metal complexes were used as heterogeneous catalysts for the air oxidation of -isophorone to ketoisophorone. The obtained complexes were characterized by means of FT-IR, 1HNMR spectroscopy, elemental analysis, powder X-ray diffraction, field emission gun scanning electron microscopy, electron spin resonance spectroscopy, ICP-AES and solubility tests. Thermal properties were also investigated using thermal gravimetric analysis. Data obtained by thermal analysis revealed that these complexes showed good thermal stability. The conversion and selectivity of -isophorone to ketoisophorone for each prepared catalyst was studied using a batch reactor and gas chromatography for product identification and quantification. The results were compared against the homogeneous bis-salicylaldehyde ethylenedi-imine-Mn catalyst. The use of methanol, acetone, methyl isobutyl ketone and -hexane as solvent and its effect on conversion and selectivity was also investigated. Acetone was found to be a promising solvent for the -isophorone oxidation. The role of triethyl amine and acetyl acetone in the oxidation reaction has also been investigated.

  4. Organization of the Escherichia coli aerobic enzyme complexes of oxidative phosphorylation in dynamic domains within the cytoplasmic membrane.

    Erhardt, Heiko; Dempwolff, Felix; Pfreundschuh, Moritz; Riehle, Marc; Schäfer, Caspar; Pohl, Thomas; Graumann, Peter; Friedrich, Thorsten


    The Escherichia coli cytoplasmic membrane contains the enzyme complexes of oxidative phosphorylation (OXPHOS). Not much is known about their supramolecular organization and their dynamics within the membrane in this model organism. In mitochondria and other bacteria, it was demonstrated by nondenaturing electrophoretic methods and electron microscopy that the OXPHOS complexes are organized in so-called supercomplexes, stable assemblies with a defined number of the individual enzyme complexes. To investigate the organization of the E. coli enzyme complexes of aerobic OXPHOS in vivo, we established fluorescent protein fusions of the NADH:ubiquinone oxidoreductase, the succinate:ubiquinone oxidoreductase, the cytochrome bd-I, and the cytochrome bo3 terminal oxidases, and the FoF1 ATP-synthase. The fusions were integrated in the chromosome to prevent artifacts caused by protein overproduction. Biochemical analysis revealed that all modified complexes were fully assembled, active, and stable. The distribution of the OXPHOS complexes in living cells was determined using total internal reflection fluorescence microscopy. The dynamics within the membrane were detected by fluorescence recovery after photobleaching. All aerobic OXPHOS complexes showed an uneven distribution in large mobile patches within the E. coli cytoplasmic membrane. It is discussed whether the individual OXPHOS complexes are organized as clustered individual complexes, here called "segrazones."

  5. Oxidized Low-Density Lipoprotein-β2-Glycoprotein I Complex But Not Free Oxidized LDL Is Associated With the Presence and Severity of Coronary Artery Disease.

    Bliden, Kevin P; Chaudhary, Rahul; Lopez, Luis R; Damrongwatanasuk, Rongras; Guyer, Kirk; Gesheff, Martin G; Franzese, Christopher J; Kaza, Himabindu; Tantry, Udaya S; Gurbel, Paul A


    Oxidized low-density lipoprotein (oxLDL) and β2-glycoprotein I (β2GPI) have been identified in human atherosclerotic lesions and when complexed have been implicated as a pro-atherothrombotic antigen. We examined the association of free oxLDL and oxLDL-β2GPI complex in patients with coronary artery disease who underwent elective cardiac catheterization. Serum was collected from patients with suspected coronary artery disease immediately before elective cardiac catheterization who were either treated (n = 385) or not treated (n = 150) with statins and from healthy volunteers (n = 134). OxLDL and oxLDL-β2GPI complex levels were determined by enzyme-linked immunosorbent assay. Disease severity was defined angiographically as none-minimal (75%) luminal diameter obstruction of any major coronary vessel. Both oxLDL and oxLDL-β2GPI complex were lower in patients on statins (p LDL4 and triglycerides increased with oxLDL-β2GPI complex quartiles (p = 0.001). OxLDL-β2GPI complex (>0.32 U/ml) was predictive of severe atherosclerosis by receiver-operating characteristic curve analysis in statin-naive patients (area under the curve 0.66, p = 0.002). In conclusion, oxLDL-β2GPI appears more predictive of coronary artery disease severity than oxLDL alone in statin-naive patients.

  6. Understanding and engineering two-dimensional electron gases in complex oxides

    Bjaalie, Lars Gunnar Tangen

    The next generation of electronic devices faces the challenge of adequately containing and controlling extremely high charge densities within structures of nanometer dimensions. Atomic-scale transistors must be thin and be able to control extremely high charge densities (>10e13/cm. 2). Silicon devicestypically have two-dimensional electron gas (2DEG) densities around 10e12/cm. 2.Nitride-based devices can sustain densities an order of magnitude higher. The "complex oxides" have recently emerged as an attractive materials system to support these developments. The demonstration of a 2DEG at the SrTiO 3/LaAlO3 interface has triggered an avalanche of research, including the unprecedentedly high density of 3x10e14/cm. 2 at SrTiO3/GdTiO3and SrTiO3/SmTiO3 interfaces. Metal-insulator (Mott) transitions that are inherent to some of these complex oxides could offer even greater prospects for enhanced functionality or novel device concepts. The materials and heterostructures that have been explored to date are clearly only a small subset of the vast number of materials combinations that could lead to interesting phenomena. In this work we use first-principles methods to build greater understanding of the interface phenomena, so that searches can be better informed and more focused. We also develop a set of criteria that the materials and their heterostructures should satisfy to develop a high-performance 2DEG-based device. We focus in particular on the band alignment, calculating it for a variety of different potential materials. Next, we study GdTiO3/SrTiO3/GdTiO3 heterostructures in depth, where each interface contributes excess electrons into the SrTiO3. We calculate the 2DEG formation for a superlattice containing six layers of SrTiO3, and compare with angle-resolved photoemission spectroscopy results. Together, the experimental and theoretical results conclusively show that the 2DEG results from the interface itself, and does not originate from a secondary source such as

  7. Copper-sulfenate complex from oxidation of a cavity mutant of Pseudomonas aeruginosa azurin

    Sieracki, Nathan A.; Tian, Shiliang; Hadt, Ryan G.; Zhang, Jun-Long; Woertink, Julia S.; Nilges, Mark J.; Sun, Furong; Solomon, Edward I.; Lu, Yi [Stanford; (UIUC); (Peking)


    Metal–sulfenate centers are known to play important roles in biology and yet only limited examples are known due to their instability and high reactivity. Herein we report a copper–sulfenate complex characterized in a protein environment, formed at the active site of a cavity mutant of an electron transfer protein, type 1 blue copper azurin. Reaction of hydrogen peroxide with Cu(I)–M121G azurin resulted in a species with strong visible absorptions at 350 and 452 nm and a relatively low electron paramagnetic resonance gz value of 2.169 in comparison with other normal type 2 copper centers. The presence of a side-on copper–sulfenate species is supported by resonance Raman spectroscopy, electrospray mass spectrometry using isotopically enriched hydrogen peroxide, and density functional theory calculations correlated to the experimental data. In contrast, the reaction with Cu(II)–M121G or Zn(II)–M121G azurin under the same conditions did not result in Cys oxidation or copper–sulfenate formation. Structural and computational studies strongly suggest that the secondary coordination sphere noncovalent interactions are critical in stabilizing this highly reactive species, which can further react with oxygen to form a sulfinate and then a sulfonate species, as demonstrated by mass spectrometry. Engineering the electron transfer protein azurin into an active copper enzyme that forms a copper–sulfenate center and demonstrating the importance of noncovalent secondary sphere interactions in stabilizing it constitute important contributions toward the understanding of metal–sulfenate species in biological systems.

  8. Crystal Structures of the Nitrite and Nitric Oxide Complexes of Horse Heart Myoglobin

    Copeland,D.; Soares, A.; West, A.; Richter-Addo, G.


    Nitrite is an important species in the global nitrogen cycle, and the nitrite reductase enzymes convert nitrite to nitric oxide (NO). Recently, it has been shown that hemoglobin and myoglobin catalyze the reduction of nitrite to NO under hypoxic conditions. We have determined the 1.20 Angstroms resolution crystal structure of the nitrite adduct of ferric horse heart myoglobin (hh Mb). The ligand is bound to iron in the nitrito form, and the complex is formulated as Mb{sup III}(ONO{sup -}). The Fe-ONO bond length is 1.94 Angstroms, and the O-N-O angle is 113 degrees. In addition, the nitrite ligand is stabilized by hydrogen bonding with the distal His64 residue. We have also determined the 1.30 Angstroms resolution crystal structures of hh Mb{sup II}NO. When hh Mb{sup II}NO is prepared from the reaction of metMb{sup III} with nitrite/dithionite, the FeNO angle is 144 degrees with a Fe-NO bond length of 1.87 Angstroms. However, when prepared from the reaction of NO with reduced Mb{sup II}, the FeNO angle is 120 degrees with a Fe-NO bond length of 2.13 Angstroms. This difference in FeNO conformations as a function of preparative method is reproducible, and suggests a role of the distal pocket in hh Mb{sup II}NO in stabilizing local FeNO conformational minima.

  9. Copper-sulfenate complex from oxidation of a cavity mutant of Pseudomonas aeruginosa azurin.

    Sieracki, Nathan A; Tian, Shiliang; Hadt, Ryan G; Zhang, Jun-Long; Woertink, Julia S; Nilges, Mark J; Sun, Furong; Solomon, Edward I; Lu, Yi


    Metal-sulfenate centers are known to play important roles in biology and yet only limited examples are known due to their instability and high reactivity. Herein we report a copper-sulfenate complex characterized in a protein environment, formed at the active site of a cavity mutant of an electron transfer protein, type 1 blue copper azurin. Reaction of hydrogen peroxide with Cu(I)-M121G azurin resulted in a species with strong visible absorptions at 350 and 452 nm and a relatively low electron paramagnetic resonance gz value of 2.169 in comparison with other normal type 2 copper centers. The presence of a side-on copper-sulfenate species is supported by resonance Raman spectroscopy, electrospray mass spectrometry using isotopically enriched hydrogen peroxide, and density functional theory calculations correlated to the experimental data. In contrast, the reaction with Cu(II)-M121G or Zn(II)-M121G azurin under the same conditions did not result in Cys oxidation or copper-sulfenate formation. Structural and computational studies strongly suggest that the secondary coordination sphere noncovalent interactions are critical in stabilizing this highly reactive species, which can further react with oxygen to form a sulfinate and then a sulfonate species, as demonstrated by mass spectrometry. Engineering the electron transfer protein azurin into an active copper enzyme that forms a copper-sulfenate center and demonstrating the importance of noncovalent secondary sphere interactions in stabilizing it constitute important contributions toward the understanding of metal-sulfenate species in biological systems.

  10. Photocatalytic benzylic C–H bond oxidation with a flavin scandium complex

    Mühldorf, Bernd; Wolf, Robert


    The enhanced reduction potential of riboflavin tetraacetate coordinating to scandium triflate enables the challenging photocatalytic C–H oxidation of electron-deficient alkylbenzenes and benzyl alcohols.

  11. Emission Properties, Solubility, Thermodynamic Analysis and NMR Studies of Rare-Earth Complexes with Two Different Phosphine Oxides

    Hiroki Iwanaga


    Full Text Available The paper proposes novel molecular designs for rare-earth complexes involving the introduction of two different phosphine oxide structures into one rare-earth ion. These designs are effective for improving solubility and emission intensity. Additionally, the complexes are indispensable for realizing high performances in LEDs and security media. The thermodynamic properties of Eu(III complexes are correlated with the solubility. Correlations between coordination structures and emission intensity were explained by NMR analysis. The luminous flux of red LED devices with Eu(III complexes is very high (20 mA, 870 m lumen. A new white LED has its largest spectra intensity in the red region and a human look much more vividly under this light.

  12. Photochemical Oxidation of a Manganese(III) Complex with Oxygen and Toluene Derivatives to Form a Manganese(V)-Oxo Complex

    Jung, Jieun; Ohkubo, Kei; Prokop-Prigge, Katharine A.; Neu, Heather M.; Goldberg, David P.; Fukuzumi, Shunichi


    Visible light photoirradiation of an oxygen-saturated benzonitrile solution of a manganese(III) corrolazine complex [(TBP8Cz)MnIII (1): [TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato3−] in the presence of toluene derivatives resulted in formation of the manganese(V)-oxo complex [(TBP8Cz)MnV(O)]. The photochemical oxidation of (TBP8Cz)MnIII with O2 and hexamethylbenzene (HMB) led to the isosbestic conversion of 1 to (TBP8Cz)MnV(O), accompanied by the selective oxidation of HMB to pentamethylbenzyl alcohol (87%). The formation rate of (TBP8Cz)MnV(O) increased with methyl group substitution, from toluene, p-xylene, mesitylene, durene, pentamethylbenzene, up to hexamethylbenzene. Deuterium kinetic isotope effects (KIEs) were observed for toluene (KIE = 5.4) and mesitylene (KIE = 5.3). Femtosecond laser flash photolysis of (TBP8Cz)MnIII revealed the formation of a tripquintet excited state, which was rapidly converted to a tripseptet excited state. The tripseptet excited state was shown to be the key, activated state that reacts with O2 via a diffusion-limited rate constant. The data allow for a mechanism to be proposed in which the tripseptet excited state reacts with O2 to give the putative (TBP8Cz)MnIV(O2•−), which then abstracts a hydrogen atom from the toluene derivatives in the rate-determining step. The mechanism of hydrogen abstraction is discussed by comparison of the reactivity with the hydrogen abstraction from the same toluene derivatives by cumylperoxyl radical. Taken together, the data suggest a new catalytic method is accessible for the selective oxidation of C-H bonds with O2 and light, and the first evidence for catalytic oxidation of C–H bonds was obtained with 10-methyl-9,10-dihydroacridine as a substrate. PMID:24219426

  13. A Kinetically Mechanistic Investigation of Oxidation of 1,4-Butanediamine by Ag(Ⅲ)Complex in Alkaline Medium

    SONG,Changying; SHAN,Jinhuan; Shen,Shigang; Sun,Hanwen


    Kinetics and mechanism of oxidation of 1,4-butanediamine by a Ag (Ⅲ)complex were studied spectropho-tometrically in alkaline medium at constant ion strength. The reaction shows first order with respect to the Ag(Ⅲ)complex and 1,4.butanediamine respectively. The second order rate constant,k`:increased with the increasing in[OH-],and decreased with the increasing in[IO4-4].A plausible mechanism was proposed from the kinetics study.The rate equations derived from the mechanism Can explain all experimental phenomena. The activation parameters were calculated.

  14. Kinetics and Mechanism of Oxidation of Leucine and Alanine by Ag(III Complex in Alkaline Medium

    Changying Song


    Full Text Available Kinetics and mechanism of oxidation of leucine and alanine by Ag(III complex were studied spectrophotometrically in alkaline medium at constant ion strength. The reaction was in first order with respect to Ag(III complex and amino acids (leucine, alanine. The second-order rate constant, k−, decreased with the increasing in [OH−] and [IO4−]. A plausible mechanism was proposed from the kinetics study, and the rate equations derived from mechanism can explain all experimental phenomena. The activation parameters were calculated at 298.2 K.

  15. Enhancing oxidative stability in heated oils using core/shell structures of collagen and α-tocopherol complex.

    Gim, Seo Yeong; Hong, Seungmi; Kim, Jisu; Kwon, YongJun; Kim, Mi-Ja; Kim, GeunHyung; Lee, JaeHwan


    In this study, collagen mesh structure was prepared by carrying α-tocopherol in the form of core/shell complex. Antioxidant properties of α-tocopherol loaded carriers were tested in moisture added bulk oils at 140°C. From one gram of collagen core/shell complex, 138mg α-tocopherol was released in medium chain triacylglycerol (MCT). α-Tocopherol was substantially protected against heat treatment when α-tocopherol was complexed in collagen core/shell. Oxidative stability in bulk oil was significantly enhanced by added collagen mesh structure or collagen core/shell complex with α-tocopherol compared to that in control bulk oils (pcore/shell with α-tocopherol (p>0.05). Results of DPPH loss in methanol demonstrated that collagen core/shell with α-tocopherol had significantly (pcore/shell complex is a promising way to enhance the stability of α-tocopherol and oxidative stability in oil-rich foods prepared at high temperature. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Phospha-scorpionate complexes by click chemistry using phenyl azide and ethynylphosphine oxides

    van Assema, S.G.A.; Tazelaar, C.G.J.; de Jong, G.B.; van Maarseveen, J.H.; Schakel, M.; Lutz, M.; Spek, A.L.; Slootweg, J.C.; Lammertsma, K.


    The copper-catalyzed Click reaction of phenyl azide with ethynylphosphine oxides provides new P-substituted triazoles. With tris(ethynyl)phosphine oxide this route affords a versatile scorpionate ligand that coordinates to RhCl3 as a tripodal N ligand. Upon reduction, the same ligand can act as a P

  17. Electrocatalytic Oxidation of NADH Based on Self-assembled Colloidal Gold and Nafion Matrixes and Co Complex Mediator

    Na WANG; Ruo YUAN; Ya Qin CHAI; Dian Ping TANG; Qiang ZHU; Xue Lian LI


    A novel approach based on self-assembled colloidal gold and Nafion matrixes and Co complex mediator to construct Co(bpy)33+/nano-Au/Co(bpy)33+/nafion/GC electrode, on which formed stable redox-active films. This electrode can decrease the overpotential about 330 mV for the oxidation of NADH with high stability, wide linear range and low detection limit.

  18. Bio-inspired multinuclear copper complexes covalently immobilized on reduced graphene oxide as efficient electrocatalysts for the oxygen reduction reaction.

    Xi, Yue-Ting; Wei, Ping-Jie; Wang, Ru-Chun; Liu, Jin-Gang


    Inspired by the multicopper active site of laccase, which efficiently catalyzes the oxygen reduction reaction (ORR), herein we report a novel bio-inspired ORR catalyst composed of a multinuclear copper complex that was immobilized on the surface of reduced graphene oxide (rGO) via the covalently grafted triazole-dipyridine (TADPy) dinucleating ligand. This rGO-TADPyCu catalyst exhibited high ORR activity and superior long-term stability compared to Pt/C in alkaline media.

  19. Ligand/cluster/support catalytic complexes in heterogeneous ultrananocatalysis: NO oxidation on Ag3/MgO(100).

    Sementa, Luca; Barcaro, Giovanni; Negreiros, Fabio R; Fortunelli, Alessandro


    In the present work we explore via first-principles simulations whether the ligand/cluster/support catalytic complex generated by CO oxidation over silver trimers deposited on the regular MgO(100) surface - i.e. a Ag3/carbonate or Ag3(CO3)/MgO(100) species - can be used as a catalyst in a different reaction: the selective oxidation of NO to NO2 (or NOox). The Ag3(CO3)/MgO(100) complex is first shown to be reasonably stable at room temperature in terms of both disaggregation and sintering, and that it can be generated from Ag3 adsorbed onto an oxygen vacancy defect of the regular MgO(100) surface under oxidation conditions. It is then found that the Ag3(CO3)/MgO(100) species transforms under NOox conditions into an even more complex aggregate, a mixed carbonate/double-nitrite Ag3(CO3)(NO2)2/MgO(100) species, which can then act as an efficient catalyst of NOox. It is noteworthy that under NOox reaction conditions a different ligand/cluster/support catalytic complex is formed with respect to the original COox one. These findings prove the diversity of the catalytic chemistry of subnanometer (or ultranano) metal clusters deposited on oxide substrates, associated with the formation of many different ligand/cluster/support aggregates, the vast amount of combinatorial possibilities thus opening, and the need for computational approaches to perform systematic structural and stoichiometric searches in order to cope with such a multiform diversity.

  20. Catalytic application of an organosuperbasedenderon grafted on mesoporous SBA-15 and related palladium complex in the aerobic oxidation of alcohols

    Hojat Veisi


    Full Text Available An efficient synthetic method for successful application of amine denderon on SBA-15 and related Pd (II complex has been developed by employing aerobic oxidation of alcohols as model reactions. The yields of the products were in the range from 75% to 92%. The catalyst can be readily recovered and reused at least 5 consecutive cycles without significant leaching and loss its catalytic activity.

  1. Mechanistic implications of the active species involved in the oxidation of hydrocarbons by Iron complexes of pyrazine-2-carboxylic acid

    Tanase, Stefania; Marques-Gallego, Patricia; Browne, Wesley R.; Hage, Ronald; Bouwman, Elisabeth; Feringa, Ben L.; Reedijk, Jan


    The reactivity towards H2O2 of the complexes [Fe(pca)(2)(py)(2)]center dot py (1) and Na-2{[Fe(pca(3))](2)O}center dot 2H(2)O center dot CH3CN (2) (where pca(-) is pyrazine-2-carboxylate) and their catalytic activity in the oxidation of hydrocarbons is reported. Addition of H2O2 to 1 results in the

  2. Kinetics and Mechanism for Oxidation of L-Proline by Bis(hydrogen periodato) argentate (Ⅲ) Complex Anion

    SUN Han-Wen; SHI Hong-Mei; SHEN Shi-Gang; FANG Wei-Jun; GUO Zhi-Feng


    Oxidation of L-proline by bis(hydrogen periodato)argentate(Ⅲ) complex anion, [Ag(HIO6)2]5-, has been studied in aqueous alkaline medium in the temperature range of 25-40 ℃ by use of conventional spectrophotometry.Under the conditions for kinetic measurements, the oxidation results in decarboxylation of proline, giving rise to γ-aminobutyrate as identified by mass spectrometry. The oxidation kinetics is first order with respect to the silver(Ⅲ)and proline concentrations; the second-order rate constants, decreasing with increasing [periodate], are essentially independent of [OH-]. The kinetic results were interpreted in terms of a reaction mechanism which involves a pre-equilibrium between [Ag(HIO6)2]5- and [Ag(HIO6)(H2O)(OH)]2-, a mono-periodate coordinated silver(Ⅲ)complex. Both Ag(Ⅲ) complexes are reduced parallelly by the fully deprotonated form of proline in reductant and shows a lower reactivity than [Ag(HIO6)(OH)(H2O)]2-.

  3. Intramolecular Oxidative O-Demethylation of an Oxoferryl Porphyrin Complexed with a Per-O-methylated β-Cyclodextrin Dimer.

    Kitagishi, Hiroaki; Kurosawa, Shun; Kano, Koji


    The intramolecular oxidation of ROCH3 to ROCH2 OH, where the latter compound spontaneously decomposed to ROH and HCHO, was observed during the reaction of the supramolecular complex (met-hemoCD3) with cumene hydroperoxide in aqueous solution. Met-hemoCD3 is composed of meso-tetrakis(4-sulfonatophenyl)porphinatoiron(III) (Fe(III) TPPS) and a per-O-methylated β-cyclodextrin dimer having an -OCH2 PyCH2 O- linker (Py=pyridine-3,5-diyl). The O=Fe(IV) TPPS complex was formed by the reaction of met-hemoCD3 with cumene hydroperoxide, and isolated by gel-filtration chromatography. Although the isolated O=Fe(IV) TPPS complex in the cyclodextrin cage was stable in aqueous solution at 25 °C, it was gradually converted to Fe(II) TPPS (t1/2 =7.6 h). This conversion was accompanied by oxidative O-demethylation of an OCH3 group in the cyclodextrin dimer. The results indicated that hydrogen abstraction by O=Fe(IV) TPPS from ROCH3 yields HO-Fe(III) TPPS and ROCH2(.) . This was followed by radical coupling to afford Fe(II) TPPS and ROCH2 OH. The hemiacetal (ROCH2 OH) immediately decomposed to ROH and HCHO. This study revealed the ability of oxoferryl porphyrin to induce two-electron oxidation.

  4. Complex Formation Between Lysozyme and Stabilized Micelles with a Mixed Poly(ethylene oxide)/Poly(acrylic acid) Shell.

    Karayianni, Maria; Gancheva, Valeria; Pispas, Stergios; Petrov, Petar


    The electrostatic complexation between lysozyme and stabilized polymeric micelles (SPMs) with a poly(acrylic acid) (PAA) or a mixed poly(ethylene oxide)/poly(acrylic acid) (PEO/PAA) shell (SPMs with a mixed shell, SPMMS) and a temperature-responsive poly(propylene oxide) (PPO) core was investigated by means of dynamic, static, and electrophoretic light scattering. The SPMs and different types of SPMMS used resulted from the self-assembly of PAA-PPO-PAA triblock copolymer chains, or PAA-PPO-PAA and PEO-PPO-PEO triblock copolymer chain mixtures (with varying chain lengths and molar ratios) in aqueous solutions at pH 10 and the subsequent cross-linking of their PPO cores via loading and photo-cross-linking of pentaerythritol tetraacrylate (PETA). The solution behavior, structure and properties of the formed complexes at pH 7 and 0.01 M ionic strength, were studied as a function of the protein concentration in the solution (the concentration of the stabilized micelles was kept constant) or equivalently the ratio of the two components. The complexation process and properties of the complexes proved to be dependent on the protein concentration, while of particular interest was the effect of the structure of the shell of the SPMs on the stability/solubility of the complexes. Finally, the fluorescence and mid infrared spectroscopic investigation of the structure of the complexed protein showed that, although a small stretching of the protein molecules occurred in some cases, no protein denaturation takes place upon complexation.

  5. Discovery of Fe7O9: a new iron oxide with a complex monoclinic structure

    Ryosuke Sinmyo; Elena Bykova; Ovsyannikov, Sergey V.; Catherine McCammon; Ilya Kupenko; Leyla Ismailova; Leonid Dubrovinsky


    Iron oxides are fundamentally important compounds for basic and applied sciences as well as in numerous industrial applications. In this work we report the synthesis and investigation of a new binary iron oxide with the hitherto unknown stoichiometry of Fe7O9. This new oxide was synthesized at high-pressure high-temperature (HP-HT) conditions, and its black single crystals were successfully recovered at ambient conditions. By means of single crystal X-ray diffraction we determined that Fe7O9 ...

  6. Advances in Homogeneous Catalysis Using Secondary Phosphine Oxides (SPOs): Pre-ligands for Metal Complexes.

    Achard, Thierry


    The secondary phosphine oxides are known to exist in equilibrium between the pentavalent phosphine oxides (SPO) and the trivalent phosphinous acids (PA). This equilibrium can be displaced in favour of the trivalent tautomeric form upon coordination to late transition metals. This tutorial review provides the state of the art of the use of secondary phosphine oxides as pre-ligands in transition metal-catalysed reactions. Using a combination of SPOs and several metals such as Pd, Pt, Ru, Rh and Au, a series of effective and original transformations have been obtained and will be discussed here.

  7. Spin dynamics of complex oxides, bismuth-antimony alloys, and bismuth chalcogenides

    Sahin, Cuneyt

    The emerging field of spintronics relies on the manipulation of electron spin in order to use it in spin-based electronics. Such a paradigm change has to tackle several challenges including finding materials with sufficiently long spin lifetimes and materials which are efficient in generating pure spin currents. This thesis predicts that two types of material families could be a solution to the aforementioned challenges: complex oxides and bismuth based materials. We derived a general approach for constructing an effective spin-orbit Hamiltonian which is applicable to all nonmagnetic materials. This formalism is useful for calculating spin-dependent properties near an arbitrary point in momentum space. We also verified this formalism through comparisons with other approaches for III-V semiconductors, and its general applicability is illustrated by deriving the spin-orbit interaction and predicting spin lifetimes for strained strontium titanate (STO) and a two-dimensional electron gas in STO (such as at the LAO/STO interface). Our results suggest robust spin coherence and spin transport properties in STO related materials even at room temperature. In the second part of the study we calculated intrinsic spin Hall conductivities for bismuth-antimony (BISb) semimetals with strong spin-orbit couplings, from the Kubo formula and using Berry curvatures evaluated throughout the Brillouin zone from a tight-binding Hamiltonian. Nearly crossing bands with strong spin-orbit interaction generate giant spin Hall conductivities in these materials, ranging from 474 ((h/e)O--1cm--1) for bismuth to 96((h/e)O--1cm --1) for antimony; the value for bismuth is more than twice that of platinum. The large spin Hall conductivities persist for alloy compositions corresponding to a three-dimensional topological insulator state, such as Bi0.83Sb0.17. The spin Hall conductivity could be changed by a factor of 5 for doped Bi, or for Bi0.83Sb0.17, by changing the chemical potential by 0.5 e

  8. Styrene Oxidation by Copper(II) Complexes Salen-Type Encapsulated into Nay Zeolite

    I. Kuźniarska-Biernacka; M.A. Carvalho; I. Correia Neves; A. M. Fonseca; A. Lisińska-Czekaj; D. Czekaj


    The copper(II) complex with a Schiff-base salen-type ligand has been encapsulated in the nanopores of a NaY zeolite by using two different methodologies, the flexible ligand and in situ complex preparation methods...

  9. Synthesis, structural studies, and oxidation catalysis of the late-first-row-transition-metal complexes of a 2-pyridylmethyl pendant-armed ethylene cross-bridged cyclam.

    Jones, Donald G; Wilson, Kevin R; Cannon-Smith, Desiray J; Shircliff, Anthony D; Zhang, Zhan; Chen, Zhuqi; Prior, Timothy J; Yin, Guochuan; Hubin, Timothy J


    The first 2-pyridylmethyl pendant-armed ethylene cross-bridged cyclam ligand has been synthesized and successfully complexed to Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+) cations. X-ray crystal structures were obtained for all six complexes and demonstrate pentadentate binding of the ligand with the requisite cis-V configuration of the cross-bridged cyclam ring in all cases, leaving a potential labile binding site cis to the pyridine donor for interaction of the complex with oxidants and/or substrates. The electronic properties of the complexes were evaluated using solid-state magnetic moment determination and acetonitrile solution electronic spectroscopy, which both agree with the crystal structure determination of high-spin divalent metal complexes in all cases. Cyclic voltammetry in acetonitrile revealed reversible redox processes in all but the Ni(2+) complex, suggesting that catalytic reactivity involving electron-transfer processes is possible for complexes of this ligand. Kinetic studies of the dissociation of the ligand from the copper(II) complex under strongly acidic conditions and elevated temperatures revealed that the pyridine pendant arm actually destabilizes the complex compared to the parent cross-bridged cyclam complex. Screening for oxidation catalysis using hydrogen peroxide as the terminal oxidant for the most biologically relevant Mn(2+), Fe(2+), and Cu(2+) complexes identified the Mn(2+) complex as a potential mild oxidation catalyst worthy of continued development.

  10. Alkoxy-Siloxide Metal Complexes: Precursors to Metal Silica, Metal Oxide Silica, and Metal Silicate Materials.

    Terry, Karl William

    The alkoxy-siloxide complexes M (OSi(O ^{rm t}Bu)_3 ]_4 (M = Ti(1), Zr(2), Hf(3)), were prepared by reaction with their respective metal diethylamides. These compounds readily undergo low-temperature decomposition to their respective metal oxide silica materials rm(MO_2{cdot}4SiO_2). The volatile products of the thermolysis of 2 (ca. 200 ^circC) were isobutylene (11.7 equiv) and water (5.4 equiv). The rm ZrO _2{cdot}4SiO_2 material from the decomposition of 2 at 400^circ C was amorphous until ca. 1100^ circC where crystallization of t-ZrO _2 occurred. After thermolysis to 1500 ^circC, t-ZrO_2 and cristobalite were the major products with minor amounts of m-ZrO_2. The rm HfO_2{cdot}4SiO_2 material from the decomposition of 3 at 400^ circC was amorphous until ca. 1000 ^circC where crystallization of c/t -HfO_2 was observed. Thermolysis to 1460^circC yielded c/t -HfO_2, m-HfO_2, and minor amounts of cristobalite. The crystallization of anatase in the rm TiO_2{cdot }4SiO_2 material from decomposed 1 at 400^circC was apparent after thermolysis to 1000^circC. Thermolysis to 1400^circC gave a mixture of anatase, rutile, and cristobalite. Compound 2 was decomposed in xylenes and yielded a transparent gel which was isolated as a white powder upon drying in vacuuo. The compounds [ Me _2AlOSi(O^{t}Bu)_3] _2 (4) and [( ^{t}BuO)MeAlOSi(O^{t}Bu) _3]_2 (5) were structurally characterized and contain bent and planar rm Al_2O_2 four membered rings, respectively. Both 4 and 5 yield isobutylene upon thermolysis (ca. 200 ^circC) and the crystallization of mullite occurs at 1034^circC and 1017^circC, respectively (by DTA). The solution thermolysis of 4 in refluxing toluene yields an opaque white gel. The crystallization of mullite occurs at 1029^circC (by DTA). The compounds [ CuOSi(O ^{t}Bu)_3]_{n } (6) and [ CuOSi(O ^{t}Bu)_2Ph]_4 (7) were prepared by reaction with [ CuO^{t}Bu]_4. The thermolysis of 6 at 1000^circ C under argon gave Cu^circ and amorphous silica and thermolysis under

  11. Outer-Sphere Mechanism in the Oxidation of Pyrrole-2- Carboxaldehyde by Hexacyanoferrate (III Complex.

    Abd-Alhakeem H. Abu-Nawwas


    Full Text Available The kinetics and mechanism of base-catalyzed oxidation of pyrrole-2-carboxaldehyde with hexacyanoferrate (III is reported. The reaction showed first order with respect to aldahyde , alkali and hexaeyanoferrate(III. The kinetic data suggest that the oxidation involves the formation of an anion of the substrate undergoes oxidation with hexaeyanoferrate(III via outer sphere mechanism process. The free radical thus produced is further oxidized to form the final products. A suitable mechanism was proposed and rate law was derived as − d[Fe CN 6 ] 3− = 2k1k2 RC(OH2 [Fe CN 6 ] 3−[OH−] k−1 H2O

  12. Azo dye oxidation with hydrogen peroxide catalysed by manganese 1,4,7-triazacyclononane complexes in aqueous solution.

    Gilbert, Bruce C; Smith, John R Lindsay; Newton, Maurice S; Oakes, John; Pons i Prats, Roger


    A kinetic and mechanistic study is reported of the oxidation of a number of azonaphthol dyes with hydrogen peroxide in aqueous solution, catalysed by some mono and dinuclear manganese(IV) complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3TACN). The results of UV-Vis investigations, augmented by EPR and ESI-MS studies, are described for a series of experiments in which concentrations, pH and ionic strength have been varied. The reactions are characterised by an induction period followed by a relatively rapid oxidation. For the dinuclear manganese complex 2, these are consistent with an initial perhydrolysis of the manganese complex involving both the dye anion and HO2-, to give mononuclear manganese species and the operation of a catalytic cycle incorporating MnIIIL(OH)3, O = MnVL(OH)2 and MnIVL(OH)3 (L = Me3TACN) (cf. the reactions of peroxidase enzymes). ESI-MS results provide evidence for the formation and reaction (with the dye) of MnIVL(OH)3. With the mononuclear manganese complex MnIVL(OMe)3, there is a short lag-phase attributed to perhydrolysis by HO2- followed by the same catalytic cycle.

  13. Selective Oxidation of Glycerol with 3% H2O2 Catalyzed by LDH-Hosted Cr(III Complex

    Gongde Wu


    Full Text Available A series of layered double hydroxides (LDHs –hosted sulphonato-salen Cr(III complexes were prepared and characterized by various physico-chemical measurements, such as Fourier transform infrared spectroscopy (FTIR, ultraviolet-visible spectroscopy (UV-Vis, powder X-ray diffraction (XRD, transmission electron microscope (TEM, scanning electron microscope (SEM and elemental analysis. Additionally, their catalytic performances were investigated in the selective oxidation of glycerol (GLY using 3% H2O2 as an oxidant. It was found that all the LDH-hosted Cr(III complexes exhibited significantly enhanced catalytic performance compared to the homogeneous Cr(III complex. Additionally, it was worth mentioning that the metal composition of LDH plates played an important role in the catalytic performances of LDH-hosted Cr(III complex catalysts. Under the optimal reaction conditions, the highest GLY conversion reached 85.5% with 59.3% of the selectivity to 1,3-dihydroxyacetone (DHA. In addition, the catalytic activity remained after being recycled five times.

  14. Complexity

    Gershenson, Carlos


    The term complexity derives etymologically from the Latin plexus, which means interwoven. Intuitively, this implies that something complex is composed by elements that are difficult to separate. This difficulty arises from the relevant interactions that take place between components. This lack of separability is at odds with the classical scientific method - which has been used since the times of Galileo, Newton, Descartes, and Laplace - and has also influenced philosophy and engineering. In recent decades, the scientific study of complexity and complex systems has proposed a paradigm shift in science and philosophy, proposing novel methods that take into account relevant interactions.

  15. Towards Catalytic Ammonia Oxidation to Dinitrogen: A Synthetic Cycle by Using a Simple Manganese Complex.

    Keener, Megan; Peterson, Madeline; Hernández Sánchez, Raúl; Oswald, Victoria F; Wu, Guang; Ménard, Gabriel


    Oxidation of the nucleophilic nitride, (salen)Mn≡N (1) with stoichiometric [Ar3 N][X] initiated a nitride coupling reaction to N2 , a major step toward catalytic ammonia oxidation (salen=N,N'-bis(salicylidene)-ethylenediamine dianion; Ar=p-bromophenyl; X=[SbCl6 ](-) or [B(C6 F5 )4 ](-) ). N2 production was confirmed by mass spectral analysis of the isotopomer, 1-(15) N, and the gas quantified. The metal products of oxidation were the reduced Mn(III) dimers, [(salen)MnCl]2 (2) or [(salen)Mn(OEt2 )]2 [B(C6 F5 )4 ]2 (3) for X=[SbCl6 ](-) or [B(C6 F5 )4 ](-) , respectively. The mechanism of nitride coupling was probed to distinguish a nitridyl from a nucleophilic/electrophilic coupling sequence. During these studies, a rare mixed-valent Mn(V) /Mn(III) bridging nitride, [(salen)Mn(V) (μ-N)Mn(III) (salen)][B(C6 F5 )4 ] (4), was isolated, and its oxidation-state assignment was confirmed by X-ray diffraction (XRD) studies, perpendicular and parallel-mode EPR and UV/Vis/NIR spectroscopies, as well as superconducting quantum interference device (SQUID) magnetometry. We found that 4 could subsequently be oxidized to 3. Furthermore, in view of generating a catalytic system, 2 can be re-oxidized to 1 in the presence of NH3 and NaOCl closing a pseudo-catalytic "synthetic" cycle. Together, the reduction of 1→2 followed by oxidation of 2→1 yield a genuine synthetic cycle for NH3 oxidation, paving the way to the development of a fully catalytic system by using abundant metal catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Discovery of Fe7O9: a new iron oxide with a complex monoclinic structure

    Sinmyo, Ryosuke; Bykova, Elena; Ovsyannikov, Sergey V.; McCammon, Catherine; Kupenko, Ilya; Ismailova, Leyla; Dubrovinsky, Leonid


    Iron oxides are fundamentally important compounds for basic and applied sciences as well as in numerous industrial applications. In this work we report the synthesis and investigation of a new binary iron oxide with the hitherto unknown stoichiometry of Fe7O9. This new oxide was synthesized at high-pressure high-temperature (HP-HT) conditions, and its black single crystals were successfully recovered at ambient conditions. By means of single crystal X-ray diffraction we determined that Fe7O9 adopts a monoclinic C2/m lattice with the most distorted crystal structure among the binary iron oxides known to date. The synthesis of Fe7O9 opens a new portal to exotic iron-rich (M,Fe)7O9 oxides with unusual stoichiometry and distorted crystal structures. Moreover, the crystal structure and phase relations of such new iron oxide groups may provide new insight into the cycling of volatiles in the Earth’s interior.

  17. NO to cancer: The complex and multifaceted role of nitric oxide and the epigenetic nitric oxide donor, RRx-001☆

    Scicinski, Jan; Oronsky, Bryan; Ning, Shoucheng; Knox, Susan; Peehl, Donna; Kim, Michelle M.; Langecker, Peter; Fanger, Gary


    The endogenous mediator of vasodilation, nitric oxide (NO), has been shown to be a potent radiosensitizer. However, the underlying mode of action for its role as a radiosensitizer – while not entirely understood – is believed to arise from increased tumor blood flow, effects on cellular respiration, on cell signaling, and on the production of reactive oxygen and nitrogen species (RONS), that can act as radiosensitizers in their own right. NO activity is surprisingly long-lived and more potent in comparison to oxygen. Reports of the effects of NO with radiation have often been contradictory leading to confusion about the true radiosensitizing nature of NO. Whether increasing or decreasing tumor blood flow, acting as radiosensitizer or radioprotector, the effects of NO have been controversial. Key to understanding the role of NO as a radiosensitizer is to recognize the importance of biological context. With a very short half-life and potent activity, the local effects of NO need to be carefully considered and understood when using NO as a radiosensitizer. The systemic effects of NO donors can cause extensive side effects, and also affect the local tumor microenvironment, both directly and indirectly. To minimize systemic effects and maximize effects on tumors, agents that deliver NO on demand selectively to tumors using hypoxia as a trigger may be of greater interest as radiosensitizers. Herein we discuss the multiple effects of NO and focus on the clinical molecule RRx-001, a hypoxia-activated NO donor currently being investigated as a radiosensitizer in the clinic. PMID:26164533

  18. NO to cancer: The complex and multifaceted role of nitric oxide and the epigenetic nitric oxide donor, RRx-001.

    Scicinski, Jan; Oronsky, Bryan; Ning, Shoucheng; Knox, Susan; Peehl, Donna; Kim, Michelle M; Langecker, Peter; Fanger, Gary


    The endogenous mediator of vasodilation, nitric oxide (NO), has been shown to be a potent radiosensitizer. However, the underlying mode of action for its role as a radiosensitizer - while not entirely understood - is believed to arise from increased tumor blood flow, effects on cellular respiration, on cell signaling, and on the production of reactive oxygen and nitrogen species (RONS), that can act as radiosensitizers in their own right. NO activity is surprisingly long-lived and more potent in comparison to oxygen. Reports of the effects of NO with radiation have often been contradictory leading to confusion about the true radiosensitizing nature of NO. Whether increasing or decreasing tumor blood flow, acting as radiosensitizer or radioprotector, the effects of NO have been controversial. Key to understanding the role of NO as a radiosensitizer is to recognize the importance of biological context. With a very short half-life and potent activity, the local effects of NO need to be carefully considered and understood when using NO as a radiosensitizer. The systemic effects of NO donors can cause extensive side effects, and also affect the local tumor microenvironment, both directly and indirectly. To minimize systemic effects and maximize effects on tumors, agents that deliver NO on demand selectively to tumors using hypoxia as a trigger may be of greater interest as radiosensitizers. Herein we discuss the multiple effects of NO and focus on the clinical molecule RRx-001, a hypoxia-activated NO donor currently being investigated as a radiosensitizer in the clinic.

  19. Antioxidant, electrochemical, thermal, antimicrobial and alkane oxidation properties of tridentate Schiff base ligands and their metal complexes

    Ceyhan, Gökhan; Çelik, Cumali; Uruş, Serhan; Demirtaş, İbrahim; Elmastaş, Mahfuz; Tümer, Mehmet


    In this study, two Schiff base ligands (HL 1 and HL 2) and their Cu(II), Co(II), Ni(II), Pd(II) and Ru(III) metal complexes were synthesized and characterized by the analytical and spectroscopic methods. Alkane oxidation activities of the metal complexes were studied on cyclohexane as substrate. The ligands and their metal complexes were evaluated for their antimicrobial activity against Corynebacterium xerosis, Bacillus brevis, Bacillus megaterium, Bacillus cereus, Mycobacterium smegmatis, Staphylococcus aureus, Micrococcus luteus and Enterococcus faecalis (as Gram-positive bacteria) and Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Yersinia enterocolitica, Klebsiella fragilis, Saccharomyces cerevisiae, and Candida albicans (as Gram-negative bacteria). The antioxidant properties of the Schiff base ligands were evaluated in a series of in vitro tests: 1,1-diphenyl-2-picrylhydrazyl (DPPH rad ) free radical scavenging and reducing power activity of superoxide anion radical generated non-enzymatic systems. Electrochemical and thermal properties of the compounds were investigated.

  20. Respiratory Complex I in Bos taurus and Paracoccus denitrificans Pumps Four Protons across the Membrane for Every NADH Oxidized.

    Jones, Andrew J Y; Blaza, James N; Varghese, Febin; Hirst, Judy


    Respiratory complex I couples electron transfer between NADH and ubiquinone to proton translocation across an energy-transducing membrane to support the proton-motive force that drives ATP synthesis. The proton-pumping stoichiometry of complex I (i.e. the number of protons pumped for each two electrons transferred) underpins all mechanistic proposals. However, it remains controversial and has not been determined for any of the bacterial enzymes that are exploited as model systems for the mammalian enzyme. Here, we describe a simple method for determining the proton-pumping stoichiometry of complex I in inverted membrane vesicles under steady-state ADP-phosphorylating conditions. Our method exploits the rate of ATP synthesis, driven by oxidation of NADH or succinate with different sections of the respiratory chain engaged in catalysis as a proxy for the rate of proton translocation and determines the stoichiometry of complex I by reference to the known stoichiometries of complexes III and IV. Using vesicles prepared from mammalian mitochondria (from Bos taurus) and from the bacterium Paracoccus denitrificans, we show that four protons are pumped for every two electrons transferred in both cases. By confirming the four-proton stoichiometry for mammalian complex I and, for the first time, demonstrating the same value for a bacterial complex, we establish the utility of P. denitrificans complex I as a model system for the mammalian enzyme. P. denitrificans is the first system described in which mutagenesis in any complex I core subunit may be combined with quantitative proton-pumping measurements for mechanistic studies.

  1. Electricity Recovery from Municipal Sewage Wastewater Using a Hydrogel Complex Composed of Microbially Reduced Graphene Oxide and Sludge

    Naoko Yoshida


    Full Text Available Graphene oxide (GO has recently been shown to be an excellent anode substrate for exoelectrogens. This study demonstrates the applicability of GO in recovering electricity from sewage wastewater. Anaerobic incubation of sludge with GO formed a hydrogel complex that embeds microbial cells via π-π stacking of microbially reduced GO. The rGO complex was electrically conductive (23 mS·cm−1 and immediately produced electricity in sewage wastewater under polarization at +200 mV vs. Ag/AgCl. Higher and more stable production of electricity was observed with rGO complexes (179–310 μA·cm−3 than with graphite felt (GF; 79–95 μA·cm−3. Electrochemical analyses revealed that this finding was attributable to the greater capacitance and smaller internal resistance of the rGO complex. Microbial community analysis showed abundances of Geobacter species in both rGO and GF complexes, whereas more diverse candidate exoelectrogens in the Desulfarculaceae family and Geothrix genus were particularly prominent in the rGO complex.

  2. Homoleptic Ce(III) and Ce(IV) Nitroxide Complexes: Significant Stabilization of the 4+ Oxidation State

    Bogart, Justin A.; Lewis, Andrew J.; Medling, Scott A.; Piro, Nicholas A.; Carroll, Patrick J.; Booth, Corwin H.; Schelter, Eric J.


    Electrochemical experiments performed on the complex Ce-IV[2-((BuNO)-Bu-t)py](4), where [2-((BuNO)-Bu-t)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(Bu4N)-Bu-n](2)[Ce(NO3)(6)] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with delta symmetry. The results speak to the behavior of CeO2 and related solid solutions in oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.

  3. Homoleptic cerium(III) and cerium(IV) nitroxide complexes: significant stabilization of the 4+ oxidation state.

    Bogart, Justin A; Lewis, Andrew J; Medling, Scott A; Piro, Nicholas A; Carroll, Patrick J; Booth, Corwin H; Schelter, Eric J


    Electrochemical experiments performed on the complex Ce(IV)[2-((t)BuNO)py]4, where [2-((t)BuNO)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(n)Bu4N]2[Ce(NO3)6] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with δ symmetry. The results speak to the behavior of CeO2 and related solid solutions in oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.

  4. CEC mechanism in electrochemical oxidation of nitrocatechol-boric acid complexes

    Rafiee, Mohammad, E-mail: [Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan (Iran, Islamic Republic of); Nematollahi, Davood; Salehzadeh, Hamid [Faculty of Chemistry, Bu-Ali Sina University, Hamedan (Iran, Islamic Republic of)


    Graphical abstract: Display Omitted Highlights: > Nitrochetechol and its anionic form undergo complex reaction with boric acid. > The electron transfer of complex is coupled with both proceeding and following chemical reactions. > Electrochemical behavior of complex is resolved by diagnostic criteria and digital simulation. - Abstract: The electrochemical behavior of nitrocatechols-boric acid complexes in aqueous solution has been studied using cyclic voltammetry. The results indicate that nitrocatechol-boric acid complex derivatives are involved in the CEC mechanism. In this work, the impact of empirical parameters on the shape of the voltammograms is examined based on a CEC mechanism. In addition, homogeneous rate constants of both the preceding and the following reactions were estimated by comparing the experimental cyclic voltammograms with the digitally simulated results. The calculated dissociation constants for the complexes (K{sub d}) and for ring cleavage of nitroquinone (k{sub f2}) were found to vary in the following order: 4-nitrocatechol > 3-methylnitrocatechol > 3-metoxynitrocatechol.

  5. Synthesis of nanocrystalline materials through reverse micelles: A versatile methodology for synthesis of complex metal oxides

    Ashok K Ganguli; Sonalika Vaidya; Tokeer Ahmad


    We have been successful in obtaining monophasic nanosized oxides with varying chemical compositions using the reverse micellar method. Here we describe our methodology to obtain important metal oxides like ceria, zirconia and zinc oxide. The oxalate of cerium, zirconium and zinc were synthesized using the reverse micellar route. While nanorods of zinc oxalate with dimension, 120 nm in diameter and 600 nm in length, could be obtained, whereas spherical particles of size, 4–6 nm, were obtained for cerium oxalate. These precursors were heated to form their respective oxides. Mixture of nanorods and nanoparticles of cerium oxide was obtained. ZrO2 nanoparticles of 3–4 nm size were obtained by the thermal decomposition of zirconium oxalate precursor. ZnO nanoparticles (55 nm) were obtained by the decomposition of zinc oxalate nanorods. Photoluminescence (PL) studies at 20 K shows the presence of three peaks corresponding to free excitonic emission, free to bound and donor–acceptor transitions. We also synthesized nanoparticles corresponding to Ba1–PbZrO3 using the reverse micellar route. The dielectric constant and loss were stable with frequency and temperature for the solid solution.

  6. Atomic-Scale Study Of Complex Cobalt Oxide Using Scanning Transmission Electron Microscope

    Gulec, Ahmet

    Cobalt oxides offer a rich ?eld for the formation of novel phases, including superconductors and exotic magnetic phases, involving a mixed valence state for cobalt and/or the presence of oxygen vacancies. Having spin states, such as, low spin (LS), high spin (HS), and intermediate spin (IS), cobalt oxides differ from other 3d metal oxides The presence of such spin states make the physics of the cobalt oxides so complicated that it has not yet been completely understood. In order to improve our understanding of the various phase transitions observed in Cobalt oxides and to comprehend the relationship between crystal and electronic structure, both high energy resolution and high spatial resolution are essential. Fortunately, transmission electron microscopy (TEM) is a technique which is capable of ful?lling both of these requirements. In this thesis, I have utilized unique techniques in a scanning transmission electron microscope (STEM) to analyze the atomic-scale structure-property relationship, both at room temperature and through insitu cooling to liquid nitrogen (LN2) temperature. In particular, by using correlated Z-contrast imaging, electron energy loss spectrum (EELS) and electron energy loss magnetic circular dichroism (EMCD), the structure, composition, bonding and magnetic behavior are characterized directly on the atomic scale.

  7. Nanoparticles of complex metal oxides synthesized using the reverse-micellar and polymeric precursor routes

    Ashok K Ganguli; Tokeer Ahmad; Padam R Arya; Pika Jha


    Current interest in the properties of materials having grains in the nanometer regime has led to the investigation of the size-dependent properties of various dielectric and magnetic materials. We discuss two chemical methods, namely the reverse-micellar route and the polymeric citrate precursor route used to obtain homogeneous and monophasic nanoparticles of several dielectric oxides like BaTiO3, Ba2TiO4, SrTiO3, PbTiO3, PbZrO3 etc. In addition we also discuss the synthesis of some transition metal (Mn and Cu) oxalate nanorods using the reverse-micellar route. These nanorods on decomposition provide a facile route to the synthesis of transition metal oxide nanoparticles. We discuss the size dependence of the dielectric and magnetic properties in some of the above oxides.

  8. Volume dependence of magnetic properties in Co2Cr1-xYx Ga (Y=Ti-Ni) Heusler alloys: A first-principles study

    Gonçalves, J. N.; Fortunato, N. M.; Amaral, J. S.; Amaral, V. S.


    The magnetic properties tuning and volume dependence in the series of quaternary full Heusler alloys with formula Co2Cr1-xYx Ga (Y=Ti, V, Mn, Fe, Co, Ni) were studied with a detailed first-principles exploration. We employ the density functional KKR method with the coherent potential approximation, estimating effective Heisenberg exchange constants via the magnetic force theorem together with mean-field Curie temperature (TC) and magnetic moment for compositions in the whole concentration range. The volumetric dependency of these magnetic properties is studied, particularly the pressure derivatives of TC at equilibrium. Our ternary alloy calculations show good agreement with local-density and generalized gradient approximations in the literature. The quaternary alloys show a wide range of tunable magnetic properties, where magnetic moments range from 0.8 to 4.9 μB, TC from 130 K to 1250 K, and dTC / dV values range from -7 to + 6.3 KÅ-3 .

  9. Complex


    Schiff bases and their complex compounds have been studied for their .... establishing coordination of the N–(2 – hydroxybenzyl) - L - α - valine Schiff base ..... (1967); “Spectrophotometric Identification of Organic Compounds”, Willey, New.

  10. A newly identified essential complex, Dre2-Tah18, controls mitochondria integrity and cell death after oxidative stress in yeast.

    Laurence Vernis

    Full Text Available A mutated allele of the essential gene TAH18 was previously identified in our laboratory in a genetic screen for new proteins interacting with the DNA polymerase delta in yeast [1]. The present work shows that Tah18 plays a role in response to oxidative stress. After exposure to lethal doses of H(2O(2, GFP-Tah18 relocalizes to the mitochondria and controls mitochondria integrity and cell death. Dre2, an essential Fe/S cluster protein and homologue of human anti-apoptotic Ciapin1, was identified as a molecular partner of Tah18 in the absence of stress. Moreover, Ciapin1 is able to replace yeast Dre2 in vivo and physically interacts with Tah18. Our results are in favour of an oxidative stress-induced cell death in yeast that involves mitochondria and is controlled by the newly identified Dre2-Tah18 complex.

  11. Mechanism of oxidation of L-methionine by iron(III)-1,10-phenanthroline complex - A kinetic study

    P Vani; K Krishna Kishore; R Rambabu; L S A Dikshitulu


    Kinetics and mechanism of oxidation of L-methionine by iron(III)-1, 10-phenanthroline complex have been studied in perchloric acid medium. The reaction is first order each in iron(III) and methionine. Increase in [phenanthroline] increases the rate while increase in [HClO4] decreases it. While the reactive species of the substrate is the zwitterionic form, that of the oxidant is [Fe(phen)2(H2O)2]3+. The proposed mechanism leads to the rate law $$\\dfrac{d[Fe(phen)^{2+}_3]}{dt} = \\dfrac{k_2 K_4 K_3 K^2_2 [Fe^{III}] [\\text{phen}^2] [\\text{Met}]}{(1+K_1 [H^+]) ([H^+]^2 + K_4 K_3 K^2_2[\\text{phen}]^2)}.$$

  12. Hydrometallurgical process for the recycling of copper using anodic oxidation of cuprous ammine complexes and flow-through electrolysis

    Oishi, T.; Yaguchi, M.; Koyama, K.; Tanaka, M. [Metals Recycling Group, Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569 (Japan); Lee, J.-C. [Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), 30 Gajeong-dong, Yuseong-ku, Daejeon 305-350 (Korea)


    Flow-through electrolysis for copper electrowinning from cuprous ammine complex was studied in order to develop a hydrometallurgical copper recycling process using an ammoniacal chloride solution, focusing on the anodic oxidation of cuprous to cupric ammine complexes. The current efficiency of this anodic oxidation was 96% at a current density of 200 A m{sup -2} under a batch condition. In a flow-through electrolysis using a sub-liter cell and a carbon felt anode, the anodic current efficiency increased with the flow rate and was typically higher than 97%. This tendency was explained by the backward flow of the cupric ammine complex, which was formed on the anode, through the diaphragm. The anodic overpotential was lower than 0.3 V even at an apparent current density of 1500 A m{sup -2}. A similar current efficiency and overpotential were also achieved in a liter scale cell, which indicates the scale flexibility of this electrolysis. The power consumption requirements for copper electrowinning in this cell were 460 and 770 kWh t{sup -1} at the current densities of 250 and 500 A m{sup -2}, respectively, which were much lower than that of the conventional copper electrowinning despite the longer interpolar distance. (author)

  13. Protective Effects of Vitamin E against Oxidative Damage Induced by Aβ1-40Cu(Ⅱ) Complexes

    Xueling DAI; Yaxuan SUN; Zhaofeng JIANG


    β-amyloid peptide (Aβ) is considered to be responsible for the formation of senile plaques,which is the hallmark of Alzheimer's disease (AD). Oxidative stress, manifested by protein oxidation and lipid peroxidation, among other alterations, is a characteristic of AD brain. A growing body of evidence has been presented in support of Aβ1-40 forming an oligomeric complex that binds copper at a CuZn superoxide dismutase-like binding site. Aβ1-40Cu(Ⅱ) complexes generate neurotoxic hydrogen peroxide (H2O2) from O2 via Cu2+ reduction, though the precise reaction mechanism is unclear. Thc toxicity of Aβ1-40 or the Aβ1-40Cu(Ⅱ)complexes to cultured primary cortical neurons was partially attenuated when (+)-α-tocopherol (vitamin E)as free radical antioxidant was added at a concentration of 100 μM. The data derived from lactate dehydrogenase (LDH) release and the formation of H2O2 confirmed the results from the MTT assay. These findings indicate that copper binding to Aβ1-40 can give rise to greater production of H2O2, which leads to a breakdown in the integrity of the plasma membrane and subsequent neuronal death. Groups treated with vitamin E exhibited much slighter damage, suggesting that vitamin E plays a key role in protecting neuronal cells from dysfunction or death.

  14. Complex self-assembly of reverse poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) triblock copolymers with long hydrophobic and extremely lengthy hydrophilic blocks.

    Cambón, Adriana; Figueroa-Ochoa, Edgar; Juárez, Josué; Villar-Álvarez, Eva; Pardo, Alberto; Barbosa, Silvia; Soltero, J F Armando; Taboada, Pablo; Mosquera, Víctor


    Amphiphilic block copolymers have emerged during last years as a fascinating substrate material to develop micellar nanocontainers able to solubilize, protect, transport, and release under external or internal stimuli different classes of cargos to diseased cells or tissues. However, this class of materials can also induce biologically relevant actions, which complement the therapeutic activity of their cargo molecules through their mutual interactions with biologically relevant entities (cellular membranes, proteins, organelles...); these interactions at the same time, are regulated by the nature, conformation, and state of the copolymeric chains. For these reasons, in this paper we investigated the self-assembly process and physico-chemcial properties of two reverse triblock poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers, BO14EO378BO14 and BO21EO385BO21, which have been recently found to be very useful as drug delivery nanovehicles and biological response modifiers under certain conditions (A. Cambón et al. Int. J. Pharm. 2013, 445, 47-57) in order to obtain a clear picture of the solution behavior of this class or block copolymers and to understand their biological activity. These block copolymers are characterized by possessing long BO blocks and extremely lengthy central EO ones, which provide them with a rich rheological behavior characterized by the formation of flowerlike micelles with sizes ranging from 20 to 40 nm in aqueous solution and the presence of intermicellar bridging even at low copolymers concentrations as denoted by atomic force microscopy. Bridging is also clearly observed by analyzing the rheological response of these block copolymers both storage and loss moduli upon changes on time, temperature, and or concentration. Strikingly, the relatively wide Poisson distribution of the polymeric chains make the present copolymers behave rather distinctly to conventional associative thickeners. The observed rich

  15. Unique Ligand-Based Oxidative DNA Cleavage by Zinc(II) Complexes of Hpyramol and Hpyrimol

    Maheswari, P.U.; Barends, S.; Özalp-Yaman, S.; de Hoog, P.; Casellas, H.; Teat, S.J.; Massera, C.; Lutz, M.; Spek, A.L.; van Wezel, G.P.; Gamez, P.; Reedijk, J.


    The zinc(II) complexes reported here have been synthesised from the ligand 4-methyl-2-N-(2-pyridylmethyl)aminophenol (Hpyramol) with chloride or acetate counterions. All the five complexes have been structurally characterised, and the crystal structures reveal that the ligand Hpyramol gradually unde

  16. A novel, green 1-glycyl-3-methyl imidazolium chloride-copper(Ⅱ)complex catalyzed C-H oxidation of alkyl benzene and cyclohexane

    Parasuraman Karthikeyan; Pundlik Rambhau Bhagat; S. Senthil Kumar


    A variety of alkyl-arenes and cyclohexane were converted to the corresponding ketones with NaClO as the oxidant in the presence of 1-glycyl-3-methyl imidazolium chloride-copper(Ⅱ) complex.This method contains simplified product isolation and catalyst recycling,affording benzylic C-H oxidation of alkyl-arenes imparting high yield of ketones.Furthermore,complex could be reused seven times without a significant loss of its catayfic activity.

  17. Silica-gel Supported V Complexes:Preparation, Characterization and Catalytic Oxidative Desulfurization

    黎俊波; 刘习文; 曹灿灿; 郭嘉; 潘志权


    In this manuscript, a series of catalyst SGn-[VVO2-PAMAM-MSA] (SG=silica gel, PAMAM=poly-amidoamine, MSA=5-methyl salicylaldehyde, n=0, 1, 2, 3) was prepared and their structures were fully charac-terized by Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelec-tron spectroscopy (XPS) and inductive coupled plasma emission spectrometer (ICP) etc. XPS revealed that the metal V and SGn-PAMAM-MSA combined more closely after the formation of Schiff base derivatives. Their cata-lytic activities for oxidation of dibenzothiophene were evaluated using tert-butyl hydroperoxide as oxidant. The results showed that the catalyst SG2.0-[VVO2-PAMAM-MSA] presented good catalytic activity and recycling time. Mean-while, the optimal condition for the catalytic oxidation of SG2.0-[VVO2-PAMAM-MSA] was also investigated, which showed that when the oxidation temperature was 90 °C, time was 60 min, the O/S was 3︰1, and the mass content of catalyst was 1%, the rate of desulfurization could reach 85.2%. Moreover, the catalyst can be recycled several times without significant decline in catalytic activity.

  18. Acyl-CoA Dehydrogenase 9 Is Required for the Biogenesis of Oxidative Phosphorylation Complex I

    J. Nouws; L. Nijtmans; S.M. Houten; M. Brand; M. Huynen; H. Venselaar; S. Hoefs; J. Gloerich; J. Kronick; T. Hutchin; P. Willems; R. Rodenburg; R. Wanders; L. van den Heuvel; J. Smeitink; R.O. Vogel


    Acyl-CoA dehydrogenase 9 (ACAD9) is a recently identified member of the acyl-CoA dehydrogenase family. It closely resembles very long-chain acyl-CoA dehydrogenase (VLCAD), involved in mitochondria! (3 oxidation of long-chain fatty acids. Contrary to its previously proposed involvement in fatty acid

  19. Photo-catalytic Degradation and Sorption of Radio-cobalt from EDTA-Co Complexes Using Manganese Oxide Materials - 12220

    Koivula, Risto; Harjula, Risto [University of Helsinki, P.O.Box 55, FI-00014 Helsinki (Finland); Tusa, Esko [Fortum Power and Heat Oy P.O.Box 100, 00048 FORTUM (Finland)


    The synthesised cryptomelane-type α-MnO{sub 2} was tested for its Co-57 uptake properties in UV-photo-reactor filled with 10 μM Co-EDTA solution with a background of 10 mM NaNO{sub 3}. High cobalt uptake of 96% was observed after 1 hour of UV irradiation. As for comparison, a well-known TiO{sub 2} (Degussa P25) was tested as reference material that showed about 92% cobalt uptake after six hours of irradiation in identical experiment conditions. It was also noted that the cobalt uptake on cryptomelane with out UV irradiation was modest, only about 10%. Decreasing the pH of the Co-EDTA solution had severe effects on the cobalt uptake mainly due to the rather high point of zero charge of the MnO{sub 2} surface (pzc at pH ∼4.5). Modifying the synthesis procedure we were able to produce a material that functioned well even in solution of pH 3 giving cobalt uptake of almost 99%. The known properties, catalytic and ion exchange, of manganese oxides were simultaneously used for the separation of EDTA complexed Co-57. Tunnel structured cryptomelane -type showed very fast and efficient Co uptake properties outperforming the well known and widely used Degussa P25 TiO{sub 2} in both counts. The layered structured manganese oxide, birnessite, reached also as high Co removal level as the reference material Degussa did but the reaction rate was considerably faster. Since the decontamination solutions are typically slightly acidic and the point of zero charge of the manganese oxides are rather high > pH 4.5 the material had to be modified. This modified material had tolerance to acidic solutions and it's Co uptake performance remained high in the solutions of lower pH (pH 3). Increasing the ion concentration of test solutions, background concentration, didn't affect the final Co uptake level; however, some changes in the uptake kinetics could be seen. The increase in EDTA/MoMO ratio was clearly reflected in the Co uptake curves. The obtained results of manganese

  20. Polyhedral C2@Agn cages distorted by ancillary pyridine N-oxide ligands in silver-acetylenediide complexes.

    Zhao, Xiao-Li; Zhang, Lin-Ping; Mak, Thomas C W


    Reactions of the pyridine N-oxide ligands L, L2 and L3 with the silver acetylenediide-containing system under hydrothermal conditions gave rise to four silver-acetylenediide complexes bearing interesting C2@Agn motifs: (Ag2C2)2(AgCF3CO2)8(L1)3.5 (1), (Ag2C2)2(AgCF3CO2)8(L2)2 (2), (Ag2C2)(AgCF3CO2)4(L3) (3) and [(Ag7(C2)(CF3SO3)3(L3)2(H2O)2] x 2CF3SO3 (4) (L = nicotinic acid N-oxide, L(1) = pyridine N-oxide, L2 = 1,2-bis(4-pyridyl)ethane N,N'-dioxide, L3 = 1,3-bis(4-pyridyl)propane N,N'-dioxide), which exhibit new distorted polyhedral C2@Agn cage motifs. Complex 1 has a pair of acetylenediide dianions encapsulated in a Ag(14) aggregate composed of three polyhedral parts, whereas 2 contains an irregular (C2)2@Ag13 double cage. In 3, the basic building unit is a centrosymmetric (C2)2@Ag12 double cage with each component single cage taking the shape of a highly distorted triangulated dodecahedron with one missing vertex. As to complex 4, the core is a C2@Ag7 single cage in the form of a slightly distorted monocapped trigonal prism with four cleaved edges that include all three vertical sides. Furthermore, in the silver-rich environment, the pyO-type ligands are induced to exhibit unprecedented coordination modes, such as the mu(5)-O,O,O,O',O' ligation mode of L2 in 2 and the mu4-O,O,O',O' mode of L3 in 3 and 4.

  1. New complexes of cobalt(II) ions with pyridinecarboxylic acid N-oxides and 4,4‧-byp

    Hnatejko, Zbigniew; Dutkiewicz, Grzegorz; Kubicki, Maciej; Lis, Stefan


    This paper reports a study concerning the isolation and characterization of mixed ligand complexes of the Co(II) ions with pyridinecarboxylic acids N-oxides (picolinic (PNO), nicotinic (NNO) and isonicotinic (INO)), [Co(PNO)2(4,4'-byp)]·6H2O 1, [Co(NNO)(4,4'-byp)NO3]·8H2O 2 and [Co(INO)(4,4'-byp)NO3]·7H2O 3; (4,4'-byp = 4,4'-bipyridine). The complexes 2 and 3 were prepared by the hydrothermal synthesis. The structures of the complexes were elucidated on the basis of elemental analysis, thermal decomposition, IR and mass spectroscopy. IR spectra show that N-oxides act as bidentate ligands, in which both the N-oxide and the carboxylate groups are involved in coordination. In 2 and 3 the Co(II) ion exists in the same coordination environment. For 1, the X-ray crystal structure has been determined and it turned out that it contains the coordination polymers, created by the chains of Co ions joined by 4,4'-byp ligands. The Co(II) ion occupies the center of symmetry in the space group C2/c. This ion is coordinated by two nitrogen atoms (from two 4,4'-byp ligands) and four oxygen atoms from two PNO anions. The extensive network of hydrogen bonds involving six different water molecules connects the one-dimensional polymers into three-dimensional crystal structure.

  2. Influence of calcium(II) and chloride on the oxidative reactivity of a manganese(II) complex of a cross-bridged cyclen ligand.

    Zhang, Zhan; Coats, Katherine L; Chen, Zhuqi; Hubin, Timothy J; Yin, Guochuan


    Available data from different laboratories have confirmed that both Ca(2+) and Cl(-) are crucial for water oxidation in Photosystem II. However, their roles are still elusive. Using a manganese(II) complex having a cross-bridged cyclen ligand as a model, the influence of Ca(2+) on the oxidative reactivity of the manganese(II) complex and its corresponding manganese(IV) analogue were investigated. It has been found that adding Ca(2+) can significantly improve the oxygenation efficiency of the manganese(II) complex in sulfide oxidation and further accelerate the oxidation of sulfoxide to sulfone. Similar improvements have also been observed for Mg(2+), Sr(2+), and Ba(2+). A new monomeric manganese(IV) complex having two cis-hydroxide ligands has also been isolated through oxidation of the corresponding manganese(II) complex with H2O2 in the presence of NH4PF6. This rare cis-dihydroxomanganese(IV) species has been well characterized by X-ray crystallography, electrochemistry, electron paramagnetic resonance, and UV-vis spectroscopy. Notably, using the manganese(IV) complex as a catalyst demonstrates higher activity than the corresponding manganese(II) complex, and adding Ca(2+) further improves its catalytic efficiency. However, adding Cl(-) decreases its catalytic activity. In electrochemical studies of manganese(IV) complexes with no chloride ligand present, adding Ca(2+) positively shifted the redox potential of the Mn(IV)/Mn(III) couple but negatively shifted its Mn(V)/Mn(IV) couple. In the manganese(II) complex having a chloride ligand, adding Ca(2+) shifted both the Mn(IV)/Mn(III) and Mn(V)/Mn(IV) couples in the negative direction. The revealed oxidative reactivity and redox properties of the manganese species affected by Ca(2+) and Cl(-) may provide new clues to understanding their roles in the water oxidation process of Photosystem II.

  3. Chemical Oxidation of Complex PAH Mixtures by Base-activated Sodium Persulfate

    Hauswirth, S.; Miller, C. T.


    In situ chemical oxidation (ISCO) is an attractive approach for the remediation of recalcitrant soil and groundwater contaminants. One oxidant that has received significant recent attention is sodium persulfate, which has several advantages, including a relatively long lifetime in porous media, the ability to destroy a wide-range of chemical contaminants, and a high oxidation potential. In this study, we investigated the chemical mechanisms associated with base-activated persulfate oxidation of polycyclic aromatic hydrocarbons (PAHs) and assessed the applicability of persulfate to the remediation of porous media contaminated with non-aqueous phase liquid (NAPL) PAH mixtures. Batch experiments were conducted to determine the oxidation kinetics for individual PAH compounds, synthetic PAH mixtures, and manufactured gas plant (MGP) tars. Additional experiments were conducted with added surfactants (Triton X-100, Triton X-45, and Tween 80) to increase PAH mass transfer from the NAPL to the aqueous phase, and with radical scavengers (ethanol and tert-butyl alcohol) to identify the reactive species responsible for degradation. Degradation of total PAHs in the NAPL experiments was as high as 70%. The addition of surfactant increased initial PAH degradation rates, but also greatly increased the rate of base consumption, thereby reducing the overall fraction degraded. The degradation of individual PAHs within the NAPLs varied significantly, with the masses of some compounds remaining largely unchanged. The results of the radical scavenger and single PAH experiments suggest that the observed pattern of degradation in PAH mixtures is the result of a combination of mass transfer considerations and competition for radical species.

  4. Copper Tetrahydrosalen Complex Encapsulated in Zeolite Y:an Effective Heterogeneous Catalyst for the Oxidation of Cycloalkanes


    A new heterogeneous catalyst, copper tetrahydrosalen complex encapsulated in zeolite Y (denoted as Cu[H4]salen/Y) has been developed with flexible ligand method, and characterized by FTIR, DR UV-Vis spectroscopy, N2 adsorption/desorption at -196℃. This catalyst behaved like a bio-mimic enzyme, and exhibited much higher activity for the oxidation of cycloalkanes than Cusalen/Y prepared with the same method. The effects of the reaction conditions on the catalytic performance were investigated.

  5. Multiphase enantioselective Kharasch-Sosnovsky allylic oxidation based on neoteric solvents and copper complexes of ditopic ligands.

    Aldea, Luis; García, José I; Mayoral, José A


    Recoverable multiphase enantioselective catalytic systems for the Kharasch-Sosnovsky oxidation of cycloalkenes with tert-butyl peroxybenzoate are described, based on the use of [BMIM][PF(6)] and a new solvent derived from glycerol as the catalyst reservoir phases, and chiral copper complexes with different ligands from the bis(oxazoline) family. The best results are obtained with the glycerol-derived solvent and a recently described azabisoxazoline-based ditopic ligand, allowing up to four uses of the catalytic phase with good results.

  6. Assessment of oxidative stress in leukocytes and granulocyte function following oral administration of a silibinin-phosphatidylcholine complex in cats.

    Webb, Craig B; McCord, Kelly W; Twedt, David C


    To determine the effect of oral administration of a silibinin-phosphatidylcholine complex (SPC) on oxidative stress in leukocytes and granulocyte function in healthy cats. 10 purpose-bred adult cats. Cats were administered SPC (10 mg/kg/d) orally for 5 days; blood samples were collected prior to and immediately after the 5-day treatment period. Leukocytes were incubated with monochlorobimane for detection of reduced glutathione (GSH) via flow cytometry. Leukocytes were also incubated with dihydrorhodamine 123 and mixed with Escherichia coli conjugated to a fluorescent marker to measure E coli phagocytosis and the subsequent oxidative burst via flow cytometry. Activities of the antioxidant enzymes superoxide dismutase and glutathione peroxidase, along with the reduced glutathione-to-oxidized glutathione (GSH:GSSG) ratio and a measure of lipid peroxidation (malondialdehyde concentration [micromol/L of blood]), were measured spectrophotometrically. The mean fluorescence intensity (MFI), representing GSH content, increased significantly in feline lymphocytes and granulocytes following 5 days of oral administration of SPC. Mean +/- SD lymphocyte MFI significantly increased from 27.8 +/- 9.0 to 39.6 +/- 6.7, and the granulocyte MFI increased from 508.6 +/- 135.6 to 612.1 +/- 122.9. Following 5 days of SPC administration, the percentage of phagocytic cells that were responding optimally significantly increased (from 37 +/- 11.8% to 45 +/- 17.5%). Other measures of oxidative stress did not change significantly. In cats, oral administration of supplemental SPC appears to increase granulocyte GSH content and phagocytic function, both of which would be potentially beneficial in cats with diseases associated with oxidative stress.

  7. Synthesis, spectral characterization, structures, and oxidation state distributions in [(corrolato)Fe(III)(NO)](n) (n = 0, +1, -1) complexes.

    Sinha, Woormileela; Deibel, Naina; Agarwala, Hemlata; Garai, Antara; Schweinfurth, David; Purohit, Chandra Shekhar; Lahiri, Goutam Kumar; Sarkar, Biprajit; Kar, Sanjib


    Two novel trans-A2B-corroles and three [(corrolato){FeNO}(6)] complexes have been prepared and characterized by various spectroscopic techniques. In the native state, all these [(corrolato){FeNO}(6)] species are diamagnetic and display "normal" chemical shifts in the (1)H NMR spectra. For two of the structurally characterized [(corrolato){FeNO}(6)] derivatives, the Fe-N-O bond angles are 175.0(4)° and 171.70(3)° (DFT: 179.94°), respectively, and are designated as linear nitrosyls. The Fe-N (NO) bond distances are 1.656(4) Å and 1.650(3) Å (DFT: 1.597 Å), which point toward a significant Fe(III) → NO back bonding. The NO bond lengths are 1.159(5) Å and 1.162(3) Å (DFT: 1.162 Å) and depict their elongated character. These structural data are typical for low-spin Fe(III). Electrochemical measurements show the presence of a one-electron oxidation and a one-electron reduction process for all the complexes. The one-electron oxidized species of a representative [(corrolato){FeNO}(6)] complex exhibits ligand to ligand charge transfer (LLCT) transitions (cor(π) → cor(π*)) at 399 and 637 nm, and the one-electron reduced species shows metal to ligand charge transfer (MLCT) transition (Fe(dπ) → cor(π*)) in the UV region at 330 nm. The shift of the νNO stretching frequency of a representative [(corrolato){FeNO}(6)] complex on one-electron oxidation occurs from 1782 cm(-1) to 1820 cm(-1), which corresponds to 38 cm(-1), and on one-electron reduction occurs from 1782 cm(-1) to 1605 cm(-1), which corresponds to 177 cm(-1). The X-band electron paramagnetic resonance (EPR) spectrum of one-electron oxidation at 295 K in CH2Cl2/0.1 M Bu4NPF6 displays an isotropic signal centered at g = 2.005 with a peak-to-peak separation of about 15 G. The in situ generated one-electron reduced species in CH2Cl2/0.1 M Bu4NPF6 at 295 K shows an isotropic signal centered at g = 2.029. The 99% contribution of corrole to the HOMO of native species indicates that oxidation occurs from

  8. Oxidizing behavior of some platinum metal fluorides. [Xe complexes with Pt, Pd fluorides; Chlorine-2 oxidation by transition metal hexafluorides

    Graham, L.


    The previously known compounds Xe/sub 2/F/sub 3//sup +/PtF/sub 6//sup -/, XeF/sup +/PtF/sub 6//sup -/ and XeF/sub 2/.2PtF/sub 4/(XePt/sub 2/F/sub 10/) were prepared by the interaction of XeF/sub 2/ with PtF/sub 4/. The new compounds XeF/sub 2/.PdF/sub 4/ and XeF/sub 2/.2PdF/sub 4/(XePd/sub 2/F/sub 10/) were produced by interaction of XeF/sub 2/ with either PdF/sub 4/ or Pd/sub 2/F/sub 6/. A weight loss-versus-time curve indicated the presence of 4:1, 3:1 and 2:1 XeF/sub 2//PdF/sub 4/ complexes. The thermal decomposition of XeFPtF/sub 6/ or XePd/sub 2/F/sub 10/ yields highly pure XeF/sub 4/. Thus the interaction of XeF/sub 2/ with platinum fluorides (PtF/sub 4/ or PtF/sub 5/) or palladium fluorides (Pd/sub 2/F/sub 6/ or PdF/sub 4/) provides for the conversion of XeF/sub 2/ to XeF/sub 4/. The compound XePd/sub 2/F/sub 10/ is a close structural relative of XePt/sub 2/F/sub 10/, and spectroscopic evidence suggests that both are salts of XeF/sup +/ and a polymeric (M/sub 2/F/sub 9/)/sub x//sup x-/ ion. A Xe:PtF/sub 6/ material of approximately 1:1 stoichiometry has been prepared and compared with XePdF/sub 6/(XeF/sub 2/.PdF/sub 4/). The interaction of chlorine with the third-series transition metal hexafluorides has been investigated. Gravimetric and tensimetric evidence indicate that the initial product of the Cl/sub 2/ plus IrF/sub 6/ reaction is a solid of composition Cl/sub 2/IrF/sub 6/. Vibrational spectroscopic and other evidence indicates that this solid yields a sequence of products, of which Cl/sub 3//sup +/IrF/sub 6//sup -/, Cl/sub 3//sup +/Ir/sub 2/F/sub 11//sup -/ and Ir/sub 4/F/sub 20/ have been identified, the last being the ultimate solid product of the room temperature decomposition of the adduct. A new chlorine fluoride generated in the room temperature decomposition of Cl/sub 2/IrF/sub 6/ has been tentatively formulated as Cl/sub 3/F from infrared evidence.

  9. Stability of Y-Ti-O nanoparticles in ODS alloys during heat treatment and high temperature swift heavy ion irradiation

    Skuratov, V.A. [FLNR, JINR, Dubna (Russian Federation); National Research Nuclear University MEPhI, Moscow (Russian Federation); Dubna State University, Dubna (Russian Federation); Sohatsky, A.S.; Kornieieva, K. [FLNR, JINR, Dubna (Russian Federation); O' Connell, J.H.; Neethling, J.H. [CHRTEM, NMMU, Port Elizabeth (South Africa); Nikitina, A.A.; Ageev, V.S. [JSC VNIINM, Moscow (Russian Federation); Zdorovets, M. [Institute of Nuclear Physics, Astana (Kazakhstan); Ural Federal University, Yekaterinburg (Russian Federation); Volkov, A.D. [Nazarbayev University, Astana (Kazakhstan)


    Aim of this report is to compare the morphology of swift (167 and 220 MeV) Xe ion induced latent tracks in Y{sub 2}Ti{sub 2}O{sub 7} nanoparticles during post-irradiation heat treatment and after irradiation at different temperatures in pre-thinned TEM foils and TEM targets prepared from hundreds microns thick irradiated oxide dispersion strengthened (ODS) steel. No difference in track parameters was found in room temperature irradiated nanoparticles in pre-thinned and conventional samples. Microstructural data gathered from pre-thinned foils irradiated in the temperature range 350-650 C or annealed at similar temperatures demonstrate that amorphous latent tracks interact with the surrounding matrix, changing the track and nanoparticle morphology, while such effect is not observed in conventional ODS material treated at the same conditions. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Thiolate-bridged dinuclear ruthenium and iron complexes as robust and efficient catalysts toward oxidation of molecular dihydrogen in protic solvents.

    Yuki, Masahiro; Sakata, Ken; Hirao, Yoshifumi; Nonoyama, Nobuaki; Nakajima, Kazunari; Nishibayashi, Yoshiaki


    Thiolate-bridged dinuclear ruthenium and iron complexes are found to work as efficient catalysts toward oxidation of molecular dihydrogen in protic solvents such as water and methanol under ambient reaction conditions. Heterolytic cleavage of the coordinated molecular dihydrogen at the dinuclear complexes and the sequential oxidation of the produced hydride complexes are involved as key steps to promote the present catalytic reaction. The catalytic activity of the dinuclear complexes toward the chemical oxidation of molecular dihydrogen achieves up to 10000 TON (turnover number), and electrooxidation of molecular dihydrogen proceeds quite rapidly. The result of the density functional theory (DFT) calculation on the reaction pathway indicates that a synergistic effect between the two ruthenium atoms plays an important role to realize the catalytic oxidation of molecular dihydrogen efficiently. The present dinuclear ruthenium complex is found to work as an efficient organometallic anode catalyst for the fuel cell. It is noteworthy that the present dinuclear complex worked not only as an effective catalyst toward chemical and electrochemical oxidation of molecular dihydrogen but also as a good anode catalyst for the fuel cell. We consider that the result described in this paper provides useful and valuable information to develop highly efficient and low-cost transition metal complexes as anode catalysts in the fuel cell.

  11. A Robust and Low-Complexity Gas Recognition Technique for On-Chip Tin-Oxide Gas Sensor Array

    Farid Flitti


    Full Text Available Gas recognition is a new emerging research area with many civil, military, and industrial applications. The success of any gas recognition system depends on its computational complexity and its robustness. In this work, we propose a new low-complexity recognition method which is tested and successfully validated for tin-oxide gas sensor array chip. The recognition system is based on a vector angle similarity measure between the query gas and the representatives of the different gas classes. The latter are obtained using a clustering algorithm based on the same measure within the training data set. Experimented results on our in-house gas sensors array show more than 98% of correct recognition. The robustness of the proposed method is tested by recognizing gas measurements with simulated drift. Less than 1% of performance degradation is noted at the worst case scenario which represents a significant improvement when compared to the current state-of-the-art.

  12. A novel catalyst of silicon cerium complex oxides for selective catalytic reduction of NO by NH_3

    徐海涛; 沈岳松; 邵成华; 林福文; 祝社民; 丘泰


    A series of CeO2/SiO2 and SixCe1-xO2 complex oxides supported on an activated Al2TiO5-TiO2-SiO2 complex phase (ATS) ceramics were prepared by step impregnation and co-impregnation methods, and characterized by N2-BET, XRD, SEM and NH3-TPD techniques. The effects of reaction temperature, CeO2/SiO2 loadings and Si/Ce molar ratio on the granular catalysts for NO selective catalytic reduction with ammonia (NH3-SCR) were studied. Results indicated that both CeO2/SiO2/ATS and CeO2/ATS catalysts showed the same ac...

  13. A New Domain of Reactivity for High-Valent Dinuclear [M(μ-O)2 M'] Complexes in Oxidation Reactions.

    Engelmann, Xenia; Yao, Shenglai; Farquhar, Erik R; Szilvási, Tibor; Kuhlmann, Uwe; Hildebrandt, Peter; Driess, Matthias; Ray, Kallol


    The strikingly different reactivity of a series of homo- and heterodinuclear [(M(III) )(μ-O)2 (M(III) )'](2+) (M=Ni; M'=Fe, Co, Ni and M=M'=Co) complexes with β-diketiminate ligands in electrophilic and nucleophilic oxidation reactions is reported, and can be correlated to the spectroscopic features of the [(M(III) )(μ-O)2 (M(III) )'](2+) core. In particular, the unprecedented nucleophilic reactivity of the symmetric [Ni(III) (μ-O)2 Ni(III) ](2+) complex and the decay of the asymmetric [Ni(III) (μ-O)2 Co(III) ](2+) core through aromatic hydroxylation reactions represent a new domain for high-valent bis(μ-oxido)dimetal reactivity.

  14. Iron complexes of chiral phenol-oxazoline ligands: Structural studies and oxidation catalysis

    Godbole, M.D.; Prat Puig, M.; Tanase, S.; Kooijman, H.; Spek, A.L.; Bouwman, E.


    Iron complexes of two ligands, HphoxCOOH and HphoxiPr, have been synthesized and characterized by crystal structure analyses. The complexes (HNEt3)2[Fe(phoxCOO)2](ClO4) and [Fe(phoxiPr)3] are reported. Reactions of the ligands rac-HphoxCOOH and rac- HphoxiPr with iron(II) or iron(III) perchlorate re

  15. The morphology of Al-Ti-O complex oxide inclusions formed in an ultra low-carbon steel melt during the RH process

    Doo, Won-Chul; Kim, Dong-Yong; Kang, Soo-Chang; Yi, Kyung-Woo


    Internal morphologies of bulk shape oxides in a melt of Ti bearing low-carbon steel were analyzed. The outer shapes of nearly spherical inclusions containing Ti were quite different from the shape of alumina inclusions that typically have a cluster form. A cross-section investigation using a polishing method and the FIB method revealed that the TiOx-Al2O3 complex oxide covers alumina clusters and that the interfaces of the alumina and complex oxide are modified as time passes.

  16. Methods to assess secondary volatile lipid oxidation products in complex food matrices

    Jacobsen, Charlotte; Yesiltas, Betül

    A range of different methods are available to determine secondary volatile lipid oxidation products. These methods include e.g. spectrophotometric determination of anisidine values and TBARS as well as GC based methods for determination of specific volatile oxidation products such as pentanal...... and hexanal. Different extraction methods for extracting volatiles before GC analysis can be used, e.g static headspace, dynamic headspace and solid phase microextraction. Traditionally, dynamic headspace extraction has been performed manually. However, recently automated dynamic headspace methods have become...... available. This presentation will briefly discuss advantages and disadvantages of spectrophotometric methods versus GC- based methods. Moreover, the different extraction methods used for GC-based analysis will be discussed and examples on results obtained with SPME, the traditional and the automated dynamic...

  17. Relationship between the catalytic properties of the products of the oxidative thermolysis of certain complexes and the porous structures of samples in the oxidation reactions of volatile organic compounds

    Semushina, Yu. P.; Pechenyuk, S. I.; Kuzmich, L. F.; Knyazeva, A. I.


    The rate of the gas-phase oxidation of ethanol, 2-propanol, acetone, ethyl acetate, dioxane, and benzene with atmospheric oxygen is studied on surfaces of bimetallic oxide catalysts Co-Fe, Cu-Fe, Cr-Co, and Ni-Fe, prepared via thermal decomposition of double complex compounds in air. It is found that the rate of oxidation of volatile compounds depends on the volume of the transient pores in the catalyst sample. The rate of oxidation on the same catalyst at 350°C depends on the nature of the substance in the order: acetone > ethyl acetate > ethanol > propanol > dioxane, benzene.

  18. The complex interface chemistry of thin-film silicon/zinc oxide solar cell structures.

    Gerlach, D; Wimmer, M; Wilks, R G; Félix, R; Kronast, F; Ruske, F; Bär, M


    The interface between solid-phase crystallized phosphorous-doped polycrystalline silicon (poly-Si(n(+))) and aluminum-doped zinc oxide (ZnO:Al) was investigated using spatially resolved photoelectron emission microscopy. We find the accumulation of aluminum in the proximity of the interface. Based on a detailed photoemission line analysis, we also suggest the formation of an interface species. Silicon suboxide and/or dehydrated hemimorphite have been identified as likely candidates. For each scenario a detailed chemical reaction pathway is suggested. The chemical instability of the poly-Si(n(+))/ZnO:Al interface is explained by the fact that SiO2 is more stable than ZnO and/or that H2 is released from the initially deposited a-Si:H during the crystallization process. As a result, Zn (a deep acceptor in silicon) is "liberated" close to the silicon/zinc oxide interface presenting the inherent risk of forming deep defects in the silicon absorber. These could act as recombination centers and thus limit the performance of silicon/zinc oxide based solar cells. Based on this insight some recommendations with respect to solar cell design, material selection, and process parameters are given for further knowledge-based thin-film silicon device optimization.

  19. Complex responses to Si quantum dots accumulation in carp liver tissue: Beyond oxidative stress.

    Serban, Andreea Iren; Stanca, Loredana; Sima, Cornelia; Staicu, Andrea Cristina; Zarnescu, Otilia; Dinischiotu, Anca


    The use of quantum dots (QDs) in biomedical applications is limited due to their inherent toxicity caused by the heavy metal core of the particles. Consequently, silicon-based QDs are expected to display diminished toxicity. We investigated the in vivo effects induced by Si/SiO2 QDs intraperitoneally injected in crucian carp liver. The QDs contained a crystalline Si core encased in a SiO2 shell, with a size between 2.75 and 11.25nm and possess intrinsic fluorescence (Ex 325nm/Em ∼690nm). Tissue fluorescence microscopy analysis revealed the presence of QDs in the liver for at least 2weeks after injection. Although protein and lipid oxidative stress markers showed the onset of oxidative stress, the hepatic tissue exhibited significant antioxidant adaptations (increase of antioxidant enzymes, recovery of glutathione levels), sustained by the activation of Hsp30 and Hsp70 chaperoning proteins. The increased activity of cyclooxigenase-2 (COX-2) and matrix metalloproteinases (MMPs) support the idea that Si/SiO2 QDs have a potential to induce inflammatory response, a scenario also indicated by the profile of Hsp60 and Hsp90 heat shock proteins. MMPs profile and the recovery of oxidative stress markers suggested a tissue remodelation phase after 3weeks from QDs administration.

  20. Catalytic activity of thiacalix[4]arenetetrasulfonate metal complexes on modified anion-exchangers for ascorbic acid oxidation.

    Odo, Junichi; Hirashima, Tomomi; Hayashida, Tomoko; Miyauchi, Asuka; Minemoto, Mami; Iuchi, Masato; Inoguchi, Masahiko


    The catalysis of ascorbic acid (AsA) oxidation by anion-exchangers modified with metal complexes of thiacalix[4]arenetetrasulfonate (Me-TCAS[4]A-500, Me=Mn(3+), Fe(3+), Co(3+), Ce(4+), Cu(2+), Zn(2+), Ni(2+), and H2) were investigated. Me-TCAS[4]A-500 (Me=Mn(3+), Fe(3+), Ce(4+), and Cu(2+)) all exhibited the ability to catalyze the oxidative reaction of AsA to dehydroascorbic acid. However, in the presence of high concentrations of AsA, only Cu(2+)-TCAS[4]A-500 was capable of complete oxidation of the acid. Moreover, after six repeat uses, Cu(2+)-TCAS[4]A-500 maintained high and relatively constant catalytic activity. Prior treatment of glucose solutions with Cu(2+)-TCAS[4]A-500, even in the presence of high AsA concentrations, enabled the satisfactory determination of glucose without interference by AsA. Cu(2+)-TCAS[4]A-500 will therefore be applicable as an artificial substitute for ascorbate oxidase, and may be useful as a means to eliminate AsA interference during the analysis of vital compounds such as glucose and uric acid.

  1. Array-based identification of triple-negative breast cancer cells using fluorescent nanodot-graphene oxide complexes.

    Tao, Yu; Auguste, Debra T


    Early and accurate diagnosis of breast cancer holds great promise to improve treatability and curability. Here, we report the usage of six luminescent nanodot-graphene oxide complexes as novel fluorescent nanoprobes in a sensing array capable of effectively identifying healthy, cancerous, and metastatic human breast cells. The sensory system is based on the utilization of nanoprobe-graphene oxide sensor elements that can be disrupted in the presence of breast cells to give fluorescent readouts. Using this multichannel sensor, we have successfully identified breast cancer cells and distinguished between estrogen receptor positive, human epidermal growth factor receptor-2 positive, and triple negative phenotypes. This approach also allows cell identification at high sensitivity (200 cells) with high reproducibility. The unknown cell sample analysis indicates that the sensor is able to identify 49 out of 50 breast cell samples correctly, with a detection accuracy of 98%. Taken together, this array-based luminescent nanoprobe-graphene oxide sensing platform presents a useful cell screening tool with potential applications in biomedical diagnostics.

  2. Highly efficient and selective photocatalytic oxidation of sulfide by a chromophore-catalyst dyad of ruthenium-based complexes.

    Li, Ting-Ting; Li, Fu-Min; Zhao, Wei-Liang; Tian, Yong-Hua; Chen, Yong; Cai, Rong; Fu, Wen-Fu


    Electronic coupling across a bridging ligand between a chromophore and a catalyst center has an important influence on biological and synthetic photocatalytic processes. Structural and associated electronic modifications of ligands may improve the efficiency of photocatalytic transformations of organic substrates. Two ruthenium-based supramolecular assemblies based on a chromophore-catalyst dyad containing a Ru-aqua complex and its chloro form as the catalytic components were synthesized and structurally characterized, and their spectroscopic and electrochemical properties were investigated. Under visible light irradiation and in the presence of [Co(NH3)5Cl]Cl2 as a sacrificial electron acceptor, both complexes exhibited good photocatalytic activity toward oxidation of sulfide into the corresponding sulfoxide with high efficiency and >99% product selectivity in neutral aqueous solution. The Ru-aqua complex assembly was more efficient than the chloro complex. Isotopic labeling experiments using (18)O-labeled water demonstrated the oxygen atom transfer from the water to the organic substrate, likely through the formation of an active intermediate, Ru(IV)═O.

  3. Nitric oxide binding and photodelivery based on ruthenium(II) complexes of 4-arylazo-3,5-dimethylpyrazole.

    Ortiz, Mayreli; Torréns, Mabel; Mola, José L; Ortiz, Pedro J; Fragoso, Alex; Díaz, Alicia; Cao, Roberto; Prados, Pilar; de Mendoza, Javier; Otero, Antonio; Antiñolo, Antonio; Lara, Agustin


    Two fluorescent ligands, 3,5-dimethyl-4-(6'-sulfonylammonium-1'-azonaphthyl)pyrazole (dmpzn, 1) and 3,5-dimethyl-4-(4'-N,N'-dimethylaminoazophenyl)pyrazole (dmpza, 2) were obtained by condensation of ketoenolic derivatives with hydrazine. 1 and 2 formed the novel dinuclear complexes [(H(2)O)(3)ClRu(micro-L)(2)RuCl(H(2)O)(3)] (3 or 4) and [(H(2)O)(NO)Cl(2)Ru(micro-L)(2)RuCl(2)(NO)(H(2)O)] (6 or 7) (where L 1 = 2 or , respectively) which were characterized by IR, NMR and elemental analysis. The nitrosyl complexes were prepared by bubbling purified nitric oxide through methanol solutions of the corresponding ruthenium(II) chloroderivative or by reaction of the appropriate ligands with Ru(NO)Cl(3). Complexes 3 and 4 were found to bind NO, resulting in an increase in fluorescence. Ligand 1 also formed the mononuclear nitrosyl complex [Ru(NO)(bpy)(2)(dmpzn)]Cl(2) (8) which released NO in water at physiological pH and in the solid state as revealed by fluorescence and IR measurements, respectively.


    CHEN Songtao; ZHAO Ganqing; LU Xiaoqing; XIE Jimin


    The polystyrene supported glutamic acid Schiff base complex of Mn (Ⅱ) (PS-Sal-Glue-Mn) was prepared with chloromethylated styrene polymer beads,2,4-dihydroxybenzaldehyde, L-glutamic acid and manganese (Ⅱ) acetate tetrahyrate. The polymeric ligand and the complex were characterized by FT-IR, small area X-ray photoelectron spectroscopy (XPS) and ICP-AES. In the presence of the manganese complex, cyclohexene (1) was effectively oxidized by molecular oxygen without reductant. The major products of the reaction were 2-cyclohexen-1-ol (2), 2-cyclohexen-1-one (3) and 2-cyclohexen-1- hydroperoxide (4), which was different with typical oxidation of cyclohexene. The influence of reaction temperature and additive for oxidation had been studied. The selectivity of 2-cyclohexen-1-hydroperoxide varied with reaction time and different additives. The mechanism of cyclohexene oxidation had also been discussed.

  5. Are matrix isolated species really “isolated”? Infrared spectroscopic and theoretical studies of noble gas-transition metal oxide complexes


    In this review, we summarize our recent results on matrix isolation infrared spectroscopic studies and theoretical investigations of noble gas-transition metal oxide complexes. The results show that some transition metal oxide species trapped in solid noble gas matrices are chemically coordinated by one or multiple noble gas atoms forming noble gas complexes and, hence, cannot be regarded as isolated species. Noble gas coordination alters the vibrational frequencies as well as the geometric and electronic structures of transition metal oxide species trapped in solid noble gas matrixes. The interactions between noble gas atoms and transition metal oxides involve ion-induced dipole interactions as well as chemical bonding interactions. Periodic trends in the bonding in these noble gas-transition metal complexes are discussed.



    The polystyrene supported glutamic acid Schiff base complex of Mn (Ⅱ) (PS-Sal-Glue-Mn) was prepared with chloromethylated styrene polymer beads, 2,4-dihydroxybenzaldehyde, L-glutamic acid and manganese (Ⅱ) acetate tetrahyrate. The polymeric ligand and the complex were characterized by FT-IR, small area X-ray photoelectron spectroscopy (XPS) and ICP-AES. In the presence of the manganese complex, cyclohexene (1) was effectively oxidized by molecular oxygen without reductant. The major products of the reaction were 2-cyclohexen-1-ol (2), 2-cyclohexen-1-one (3) and 2-cyclohexen-1- hydroperoxide (4), which was different with typical oxidation of cyclohexene. The influence of reaction temperature and additive for oxidation had been studied. The selectivity of 2-cyclohexen-1-hydroperoxide varied with reaction time and different additives. The mechanism of cyclohexene oxidation had also been discussed.

  7. Magnetic interactions in oxide-bridged dichromium(III) complexes. Computational determination of the importance of non-bridging ligands

    Morsing, Thorbjørn Juul; Sauer, Stephan P. A.; Weihe, Høgni


    The magnetic susceptibility of the dinuclear chromium(III) complex [(CH3CN)5CrOCr(NCCH3)5](BF4)4 · 2 CH3CN has been measured and analyzed. With a fitted value of the triplet energy J = 650 cm-1, the antiferromagnetic coupling is the strongest hitherto determined for an unsupported linear oxide-br...... relative errors typically of less than 10 % ranging from the strongest coupled systems to systems with moderately strong couplings. A significant influence (>20%) of the chemical nature of the peripheral, non-bridging ligands on the exchange coupling was found and rationalized.......The magnetic susceptibility of the dinuclear chromium(III) complex [(CH3CN)5CrOCr(NCCH3)5](BF4)4 · 2 CH3CN has been measured and analyzed. With a fitted value of the triplet energy J = 650 cm-1, the antiferromagnetic coupling is the strongest hitherto determined for an unsupported linear oxide...

  8. Ruthenium complex with benznidazole and nitric oxide as a new candidate for the treatment of chagas disease.

    Renata Sesti-Costa


    Full Text Available Chagas disease remains a serious medical and social problem in Latin America and is an emerging concern in nonendemic countries as a result of population movement, transfusion of infected blood or organs and congenital transmission. The current treatment of infected patients is unsatisfactory due to strain-specific drug resistance and the side effects of the current medications. For this reason, the discovery of safer and more effective chemotherapy is mandatory for the successful treatment and future eradication of Chagas disease.We investigated the effect of a ruthenium complex with benznidazole and nitric oxide (RuBzNO2 against Trypanosoma cruzi both in vitro and in vivo. Our results demonstrated that RuBzNO2 was more effective than the same concentrations of benznidazole (Bz in eliminating both the extracellular trypomastigote and the intracellular amastigote forms of the parasite, with no cytotoxic effect in mouse cells. In vivo treatment with the compound improved the survival of infected mice, inhibiting heart damage more efficiently than Bz alone. Accordingly, tissue inflammation and parasitism was significantly diminished after treatment with RuBzNO2 in a more effective manner than that with the same concentrations of Bz.The complexation of Bz with ruthenium and nitric oxide (RuBzNO2 increases its effectiveness against T. cruzi and enables treatment with lower concentrations of the compound, which may reduce the side effects of Bz. Our findings provide a new potential candidate for the treatment of Chagas disease.

  9. Ruthenium complex with benznidazole and nitric oxide as a new candidate for the treatment of chagas disease.

    Sesti-Costa, Renata; Carneiro, Zumira A; Silva, Maria C; Santos, Maíta; Silva, Grace K; Milanezi, Cristiane; da Silva, Roberto S; Silva, João S


    Chagas disease remains a serious medical and social problem in Latin America and is an emerging concern in nonendemic countries as a result of population movement, transfusion of infected blood or organs and congenital transmission. The current treatment of infected patients is unsatisfactory due to strain-specific drug resistance and the side effects of the current medications. For this reason, the discovery of safer and more effective chemotherapy is mandatory for the successful treatment and future eradication of Chagas disease. We investigated the effect of a ruthenium complex with benznidazole and nitric oxide (RuBzNO2) against Trypanosoma cruzi both in vitro and in vivo. Our results demonstrated that RuBzNO2 was more effective than the same concentrations of benznidazole (Bz) in eliminating both the extracellular trypomastigote and the intracellular amastigote forms of the parasite, with no cytotoxic effect in mouse cells. In vivo treatment with the compound improved the survival of infected mice, inhibiting heart damage more efficiently than Bz alone. Accordingly, tissue inflammation and parasitism was significantly diminished after treatment with RuBzNO2 in a more effective manner than that with the same concentrations of Bz. The complexation of Bz with ruthenium and nitric oxide (RuBzNO2) increases its effectiveness against T. cruzi and enables treatment with lower concentrations of the compound, which may reduce the side effects of Bz. Our findings provide a new potential candidate for the treatment of Chagas disease.

  10. Impact of electric-field dependent dielectric constants on two-dimensional electron gases in complex oxides

    Peelaers, H.; Gordon, L.; Steiauf, D.; Janotti, A.; Van de Walle, C. G. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Krishnaswamy, K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106-9560 (United States); Sarwe, A. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Applied Physics Department, Chalmers Institute of Technology, Gothenburg SE 412-96 (Sweden)


    High-density two-dimensional electron gas (2DEG) can be formed at complex oxide interfaces such as SrTiO{sub 3}/GdTiO{sub 3} and SrTiO{sub 3}/LaAlO{sub 3}. The electric field in the vicinity of the interface depends on the dielectric properties of the material as well as on the electron distribution. However, it is known that electric fields can strongly modify the dielectric constant of SrTiO{sub 3} as well as other complex oxides. Solving the electrostatic problem thus requires a self-consistent approach in which the dielectric constant varies according to the local magnitude of the field. We have implemented the field dependence of the dielectric constant in a Schrödinger-Poisson solver in order to study its effect on the electron distribution in a 2DEG. Using the SrTiO{sub 3}/GdTiO{sub 3} interface as an example, we demonstrate that including the field dependence results in the 2DEG being confined closer to the interface compared to assuming a single field-independent value for the dielectric constant. Our conclusions also apply to SrTiO{sub 3}/LaAlO{sub 3} as well as other similar interfaces.

  11. Synthesis, Characterization and Activity of Rare Earth Complexes with Schiff Base From 2,6-Diformylpyridine N-Oxide and 4-Amino-antipyrine

    于青; 唐瑜; 谭民裕


    Six new rare earth complexes with Schiff base from 2,6-diformylpyridine N-oxide and 4-amino-antipyrine were synthesized. These complexes with general formula REL(NO3)3 (RE=La, Pr, Eu, Tb, Er, Y) were characterized by elemental analysis, IR, UV, molar conductance measurements and antimicrobial activity.

  12. The complex interplay of iron metabolism, reactive oxygen species, and reactive nitrogen species: insights into the potential of various iron therapies to induce oxidative and nitrosative stress.

    Koskenkorva-Frank, Taija S; Weiss, Günter; Koppenol, Willem H; Burckhardt, Susanna


    Production of minute concentrations of superoxide (O2(*-)) and nitrogen monoxide (nitric oxide, NO*) plays important roles in several aspects of cellular signaling and metabolic regulation. However, in an inflammatory environment, the concentrations of these radicals can drastically increase and the antioxidant defenses may become overwhelmed. Thus, biological damage may occur owing to redox imbalance-a condition called oxidative and/or nitrosative stress. A complex interplay exists between iron metabolism, O2(*-), hydrogen peroxide (H2O2), and NO*. Iron is involved in both the formation and the scavenging of these species. Iron deficiency (anemia) (ID(A)) is associated with oxidative stress, but its role in the induction of nitrosative stress is largely unclear. Moreover, oral as well as intravenous (iv) iron preparations used for the treatment of ID(A) may also induce oxidative and/or nitrosative stress. Oral administration of ferrous salts may lead to high transferrin saturation levels and, thus, formation of non-transferrin-bound iron, a potentially toxic form of iron with a propensity to induce oxidative stress. One of the factors that determine the likelihood of oxidative and nitrosative stress induced upon administration of an iv iron complex is the amount of labile (or weakly-bound) iron present in the complex. Stable dextran-based iron complexes used for iv therapy, although they contain only negligible amounts of labile iron, can induce oxidative and/or nitrosative stress through so far unknown mechanisms. In this review, after summarizing the main features of iron metabolism and its complex interplay with O2(*-), H2O2, NO*, and other more reactive compounds derived from these species, the potential of various iron therapies to induce oxidative and nitrosative stress is discussed and possible underlying mechanisms are proposed. Understanding the mechanisms, by which various iron formulations may induce oxidative and nitrosative stress, will help us

  13. Selection, characterisation and mapping of complex electrochemical processes at individual single-walled carbon nanotubes: the case of serotonin oxidation.

    Güell, Aleix G; Meadows, Katherine E; Dudin, Petr V; Ebejer, Neil; Byers, Joshua C; Macpherson, Julie V; Unwin, Patrick R


    The electrochemical (EC) oxidation of the neurotransmitter, serotonin, at individual single-walled carbon nanotubes (SWNTs) is investigated at high resolution using a novel platform that combines flow-aligned SWNTs with atomic force microscopy, Raman microscopy, electronic conductance measurements, individual SWNT electrochemistry and high-resolution scanning electrochemical cell microscopy (SECCM). SECCM has been used to visualise the EC activity along side-wall sections of metallic SWNTs to assess the extent to which side-walls promote the electrochemistry of this complex multi-step process. Uniform and high EC activity is observed that is consistent with significant reaction at the side-wall, rather than electrochemistry being driven by defects alone. By scanning forward and reverse (trace and retrace) over the same region of a SWNT, it is also possible to assess any blocking of EC activity by serotonin oxidation reaction products. At a physiologically relevant concentration (5 μM), there is no detectable blocking of SWNTs, which can be attributed, at least in part, to the high diffusion rate to an individual, isolated SWNT in the SECCM format. At higher serotonin concentration (2 mM), oligomer formation from oxidation products is much more significant and major blocking of the EC process is observed from line profiles recorded as the SECCM meniscus moves over an SWNT. The SECCM line profile morphology is shown to be highly diagnostic of whether blocking occurs during EC processes. The studies herein add to a growing body of evidence that various EC processes at SWNTs, from simple outer sphere redox reactions to complex multi-step processes, occur readily at pristine SWNTs. The platform described is of general applicability to various types of nanostructures and nanowires.

  14. Quercetin phospholipid complex significantly protects against oxidative injury in ARPE-19 cells associated with activation of Nrf2 pathway.

    Xu, Xin-Rong; Yu, Hai-Tao; Yang, Yan; Hang, Li; Yang, Xue-Wen; Ding, Shu-Hua


    Age-related macular degeneration (AMD) is a major cause of blindness worldwide. Oxidative stress plays a crucial role in the pathogenesis of dry AMD. Quercetin has potent anti-oxidative activities, but poor bioavailability limits its therapeutic application. Herein, we prepared the phospholipid complex of quercetin (quercetin-PC), characterized its structure by differential scanning calorimetry, infrared spectrum and x-ray diffraction. Quercetin-PC had equilibrium solubility of 38.36 and 1351.27μg/ml in water and chloroform, respectively, which was remarkably higher than those of quercetin alone. Then we established hydrogen peroxide (H2O2)-induced oxidative injury model in human ARPE-19 cells to examine the effects of quercetin-PC. Quercetin-PC, stronger than quercetin, promoted cell proliferation, and the proliferation rate was increased to be 78.89% when treated with Quercetin-PC at 400μM. Moreover, quercetin-PC effectively prevented ARPE-19 cells from apoptosis, and the apoptotic rate was reduced to be 3.1% when treated with Quercetin-PC at 200μM. In addition, quercetin-PC at 200μM significantly increased the activities of SOD, CAT and GSH-PX, and reduced the levels of reactive oxygen species and MDA in H2O2-treated ARPE-19 cells, but quercetin at 200μM failed to do so. Molecular examinations revealed that quercetin-PC at 200μM significantly activated Nrf2 nuclear translocation and significantly enhanced the expression of target genes HO-1, NQO-1 and GCL by different folds at both mRNA and protein levels. Our current data collectively indicated that quercetin-PC had stronger protective effects against oxidative-induced damages in ARPE-19 cells, which was associated with activation of Nrf2 pathway and its target genes implicated in antioxidant defense.

  15. Unraveling the complexity of iron oxides at high pressure and temperature: Synthesis of Fe5O6.

    Lavina, Barbara; Meng, Yue


    The iron-oxygen system is the most important reference of rocks' redox state. Even as minor components, iron oxides can play a critical role in redox equilibria, which affect the speciation of the fluid phases chemical differentiation, melting, and physical properties. Until our recent finding of Fe4O5, iron oxides were assumed to comprise only the polymorphs of FeO, Fe3O4, and Fe2O3. Combining synthesis at high pressure and temperature with microdiffraction mapping, we have identified yet another distinct iron oxide, Fe5O6. The new compound, which has an orthorhombic structure, was obtained in the pressure range from 10 to 20 GPa upon laser heating mixtures of iron and hematite at ~2000 K, and is recoverable to ambient conditions. The high-pressure orthorhombic iron oxides Fe5O6, Fe4O5, and h-Fe3O4 display similar iron coordination geometries and structural arrangements, and indeed exhibit coherent systematic behavior of crystallographic parameters and compressibility. Fe5O6, along with FeO and Fe4O5, is a candidate key minor phase of planetary interiors; as such, it is of major petrological and geochemical importance. We are revealing an unforeseen complexity in the Fe-O system with four different compounds-FeO, Fe5O6, Fe4O5, and h-Fe3O4-in a narrow compositional range (0.75 < Fe/O < 1.0). New, finely spaced oxygen buffers at conditions of the Earth's mantle can be defined.

  16. Importance of As(V)-iron oxides complexes in retention mechanisms of arsenic in soils

    Cancès, B.; Laperche, V.; Juillot, F.; Morin, G.; Calas, G.


    The knowledge of arsenic speciation in environmental system is primordial since the mobility and toxicity of this element strongly depends on its chemical form (oxidation state, molecular environment). The objective of the present study is to compare the arsenic speciation in recently polluted soils and in their long term natural analogues in order to identify major As-bearing mineral phases controlling the fate of arsenic in soils. Our approach, which combines conventional techniques (XRD, SEM-EDS) with X-ray Absorption Spectroscopy (EXAFS and XANES), provides the possibility of measuring changes of arsenic speciation as a function of soil horizons. At this step of the study, two soil profiles were investigated : The first one is located in the vicinity of a former arsenical pesticides manufactory (Auzon, France). The other one has developed over a geochemical anomaly (Echassières, France) and can be considered as a long term analogue for polluted soils. In the first soil studied, the main source of arsenic comes from the topsoil through the dissolution of pesticides (Schulténite PbHAsO4 and alumopharmacosidérite KAl4(AsO4)3(OH)5.6,5H2O) or/and of As sulfides (realgar AsS and orpiment As2S3). In the second one, arsenic comes from the geological substratum through the dissolution of pharmacosiderite ((Bax,K2-2x)(Fe, Al)4(AsO4)3(OH)5.6H2O formed by hydrothermal weathering of arsenopyrite (FeAsS) and löllingite (FeAs2). Despite these contrasted sources and ways of dissemination, our results indicate that arsenic is mainly present as As(V) co-precipitated with, or adsorbed on poorly ordered iron (oxihydr)oxides, such as ferrihydrite in topsoil horizon of both soil profiles. This study emphasizes the importance of iron (oxihydr)oxides in the trapping of arsenic released in the environment, provided the persistence of acidic and oxidizing soil conditions.

  17. Complex oxide with negative thermal expansion for producing ceramic matrix composites with invar effect

    Dedova, Elena S.; Pertushina, Mariya U.; Kondratenko, Anton I.; Gorev, Mikhail V.; Kulkov, Sergei N.


    The article investigates the phase composition of (Al2O3-20 wt % ZrO2)-ZrW2O8 ceramic composites obtained by cold-pressing and sintering processes. Using X-ray analysis it has been shown that composites mainly have monoclinic modification of zirconium dioxide and orthorhombic phase of aluminum oxide. After adding zirconium tungstate the phase composition of sintered ceramics changes, followed by the formation of tungsten-aluminates spinel such as Alx(WOy)z. It has been shown that thermal expansion coefficient of material decreases approximatly by 30%, as compared with initial ceramics.

  18. Parkinson’s Disease: A Complex Interplay of Mitochondrial DNA Alterations and Oxidative Stress

    Sarah Ciccone


    Full Text Available Parkinson’s disease (PD is one of the most common age-related neurodegenerative diseases. This pathology causes a significant loss of dopaminergic neurons in the Substantia Nigra. Several reports have claimed a role of defective nuclear and mitochondrial DNA repair pathways in PD etiology, in particular, of the Base Excision Repair (BER system. In addition, recent findings, related to PD progression, indicate that oxidative stress pathways involving c-Abl and GST could also be implicated in this pathology. This review focuses on recently described networks most likely involved in an integrated manner in the course of PD.

  19. Immobilization of cobalt(II) Schiff base complexes on polystyrene resin and a study of their catalytic activity for the aerobic oxidation of alcohols.

    Jain, Suman; Reiser, Oliver


    The copper-catalyzed [3+2] azide-alkyne cycloaddition and the Staudinger ligation are readily applicable and highly efficient for the immobilization of cobalt Schiff base complexes onto polystyrene resins. Stepwise synthesis of polymer-bound Schiff bases followed by their subsequent complexation with metal ions were successfully carried out. Direct covalent attachment of preformed homogeneous cobalt Schiff base complexes to the resins was also possible. The catalytic efficiency of the so-prepared polystyrene-bound cobalt Schiff bases was studied for the oxidation of alcohols to carbonyl compounds using molecular oxygen as oxidant. The immobilized complexes were highly efficient and even more reactive than the corresponding homogenous analogues, thus affording better yields of oxidized products within shorter reaction times. The supported catalysts could easily be recovered from the reaction mixture by simple filtration and reused for subsequent experiments with consistent catalytic activity.

  20. Half-metallicity and magnetism of the full-Heusler compounds KYX2 (Y=Ti, V, and Cr; X=C, N, and O)

    Dehghanzadeh, M.; Ahmadian, F.


    The electronic structure and half-metallic (HM) properties of new alloys KYX2 (Y=Ti, V, and Cr; X=C, N, and O) containing transition metals and sp elements were investigated within the density functional theory (DFT) using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. It was found that these new compounds can be experimentally synthesized because of their negative formation energies. The total energy calculations showed that in all compounds, the stable state structure was a ferromagnetic AlCu2Mn-type structure except for KTiC2 and KTiN2 which were stable in a nonmagnetic (NM) AlCu2Mn-type structure. The KTiO2 in both structures, KCrO2 in AlCu2Mn-type structure, and KVO2 in CuHg2Ti-type structure were half-metallic ferromagnets. KVO2 in AlCu2Mn-type structure was a special case with a ferromagnetic semiconducting behavior. The origin of minority band gaps for KTiO2 in both structures was also studied using the band structure calculations. The total magnetic moments of HM compounds were integer values which were in agreement with Slater-Pauling rule (Mtot=Ztot-12). Furthermore, the regions of half-metallictiy in HM compounds were considerably wider than those of Heusler compounds including transition metals, indicating the high robustness of half-metallicity with variation of lattice constants.

  1. High Turnover Catalysis of Water Oxidation by Mn(II) complexes of Monoanionic Pentadentate Ligands

    Seidler-Egdal, Rune Kirk; Nielsen, Anne; Bond, Andrew


    Capillary electrophoresis (CE) and electrospray ionisation (ESI) mass spectra of aqueous solutions of manganese(II) complexes of the monoanions of the pentadentate ligands N-methyl-N′-carboxymethyl-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine (mcbpen−) and N-benzyl-N′-carboxymethyl-N,N′-bis(2...

  2. High turnover catalysis of water oxidation by Mn(II) complexes of monoanionic pentadentate ligands

    Seidler-Egdal, Rune Kirk; Nielsen, Anne; Bond, Andrew


    Capillary electrophoresis (CE) and electrospray ionisation (ESI) mass spectra of aqueous solutions of manganese(II) complexes of the monoanions of the pentadentate ligands N-methyl-N'-carboxymethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2-diamine (mcbpen(-)) and N-benzyl-N'-carboxymethyl-N,N'-bis(2...

  3. Dioxygen affinities and catalytic oxidation activities of cobalt complexes with Schiff bases containing crown ether

    Sun, B.; Chen, J.R.; Hu, J.Y.; Li, X.J.


    The stoichiometry of dioxygen uptake of Co complexes with 4',5'-bis-(5-chloro-2-hydroxyphenylmethylideneimino)benzo-12-crown-4 (la), 4',5'-bis(2-hydroxyphenylmethylideneimino)benzo-12-crown-4(1b), 4',5'-bis-(5-methoxy-2-hydroxyphenylmethylideneimino)benzo-12-crown-4 (1c), 4',5'-bis-(5-chloro-2-hydro

  4. Reduction enhances yields of nitric oxide trapping by iron-diethyldithiocarbamate complex in biological systems.

    Vanin, A.F.; Bevers, L.M.; Mikoyan, V.D.; Poltorakov, A.P.; Kubrina, L.N.; Faassen, E. van


    The mechanism of NO trapping by iron-diethylthiocarbamate complexes was investigated in cultured cells and animal and plant tissues. Contrary to common belief, the NO radicals are trapped by iron-diethylthiocarbamates not only in ferrous but in ferric state also in the biosystems. When DETC was exce

  5. Polycation-Sodium Lauryl Ether Sulfate-Type Surfactant Complexes : Influence of Ethylene Oxide Length

    Vleugels, Leo F. W.; Pollet, Jennifer; Tuinier, Remco


    Poiyelectrolyte-surfactant complexes (PESC) are a class of materials which form spontaneously by self-assembly driven by electrostatic and hydrophobic interactions. PESC containing sodium lauryl ether Sulfates (SLES) have found wide application in hair care products like shampoo. Typically, SLES wit

  6. Gold(I) Carbene Complexes Causing Thioredoxin 1 and Thioredoxin 2 Oxidation as Potential Anticancer Agents

    Schuh, Esther; Pflueger, Carolin; Citta, Anna; Folda, Alessandra; Rigobello, Maria Pia; Bindoli, Alberto; Casini, Angela; Mohr, Fabian


    Gold(I) complexes with 1,3-substituted imidazole-2-ylidene and benzimidazole-2-ylidene ligands of the type NHC-Au-L (NHC = N-heterocyclic carbene L = Cl or 2-mercapto-pyrimidine) have been synthesized and structurally characterized. The compounds were evaluated for their antiproliferative properties

  7. Structural features and oxidative stress towards plasmid DNA of apramycin copper complex.

    Balenci, D; Bonechi, G; D'Amelio, N; Gaggelli, E; Gaggelli, N; Molteni, E; Valensin, G; Szczepanik, W; Dziuba, M; Swiecicki, G; Jezowska-Bojczuk, M


    The interaction of apramycin with copper at different pH values was investigated by potentiometric titrations and EPR, UV-vis and CD spectroscopic techniques. The Cu(II)-apramycin complex prevailing at pH 6.5 was further characterized by NMR spectroscopy. Metal-proton distances derived from paramagnetic relaxation enhancements were used as restraints in a conformational search procedure in order to define the structure of the complex. Longitudinal relaxation rates were measured with the IR-COSY pulse sequence, thus solving the problems due to signal overlap. At pH 6.5 apramycin binds copper(II) with a 2 : 1 stoichiometry, through the vicinal hydroxyl and deprotonated amino groups of ring III. Plasmid DNA electrophoresis showed that the Cu(II)-apramycin complex is more active than free Cu(II) in generating strand breakages. Interestingly, this complex in the presence of ascorbic acid damages DNA with a higher yield than in the presence of H(2)O(2).

  8. The complex photo-rearrangement of a heterocyclic N-oxide : Kinetics from picoseconds to minutes

    Cordes, Thorben; Regner, Nadja; Heinz, Björn; Borysova, Elina; Ryseck, Gerald; Gilch, Peter


    The photo-induced rearrangement of 2-benzoyl-3-phenylquinoxaline-1,4-dioxide yielding 1,3-dibenzoylbenzimidazolone (DBBI) is studied by time-resolved fluorescence, UV/vis absorption, and IR spectroscopy. This complex rearrangement occurs on time scales ranging from 0.1 ps up to minutes. Processes wi

  9. Chemistry of high-oxidation-state groups V and VI complexes: Novel silyl and imido complexes and the reactions of silyl and alkyl alkylidyne complexes with oxygen

    Chen, Tianniu

    This dissertation describes the synthesis and characterization of the novel early transition metal (especially group VI metals) complexes free of anionic pi-ligands such as cyclopentadienyl (Cp) and studies of their reactions with oxygen and silanes. Our study of Cp-free tungsten silyl chemistry is reported. A novel d 0 tungsten silyl complex 2 [(ButCH 2)W(=CHBut)2(SiButPh2 ) (2a) ⇌ (ButCH2)2W(≡CBu t)(SiButPh2) (2b)] and an equilibrium between 2a and 2b are described in Chapter 2. The thermodynamics of this equilibrium [DeltaH° = -0.9(0.2) kcal/mol, DeltaS° = -0.6(0.8) eu] was investigated by 1H NMR. The studies of the alpha-hydrogen exchange between 2a and 2b by 2-D EXSY experiments gave kinetic parameters of the exchange: DeltaH≠ = 17.9(1.1) kcal/mol, DeltaS≠ = 1.9(5.7) eu for the forward reaction (2a → 2b) and Delta H≠ = 18.6 (1.1) kcal/mol, DeltaS ≠ = 1.9(5.7) eu for the back reaction (2b → 2a). The reaction of O2 with silyl alkylidyne 2b [(Bu tCH2)W(=CHBut)2(SiBut Ph2) (2a) ⇌ (ButCH2)2W(≡CBu t)(SiButPh2) (2b)] is described in Chapter 3. A silyl migration product (ButCH2) 2W(=O)[=C(But)(SiButPh2)] ( 5) was characterized. A siloxy analog of 2b, (Bu tCH2)2W≡CBut(OSiBu tPh2) (6), was prepared and excluded as a possible intermediate in the formation of 5. Ab initio calculations suggested a pathway involving silyl migration in 2b to give a tungsten (IV) intermediate (ButCH 2)2W=C(But)(SiButPh2) (7) prior to the reaction with O2. A crystal structure of (Me3SiCH2)2W(=O)(=CHSiMe3)(O=PMe 3)•(Me3SiCH2)3W≡CSiMe 3 (12) was obtained from the reaction of alkyl alkylidyne (Me3SiCH2)3W≡CSiMe3 with O2 in the presence of PMe3. In Chapter 4, preparation and characterization of bis(2,6-diisopropylphenylimido)molybdenum(VI) amide and silyl complexes (ArN=)2Mo(NMe2)2 (14), (ArN=)2Mo(NMe2)[Si(SiMe3) 3] (15), (ArN=)2MoCl[N(SiMe3) 2] (16), (ArN=)2Mo(NMe2)[N(SiMe 3)2] (17), and (ArN=)2Mo(NHAr) 2 (18) are reported. In addition, new bis

  10. A Manganese(V)-Oxo Complex: Synthesis by Dioxygen Activation and Enhancement of Its Oxidizing Power by Binding Scandium Ion.

    Hong, Seungwoo; Lee, Yong-Min; Sankaralingam, Muniyandi; Vardhaman, Anil Kumar; Park, Young Jun; Cho, Kyung-Bin; Ogura, Takashi; Sarangi, Ritimukta; Fukuzumi, Shunichi; Nam, Wonwoo


    A mononuclear non-heme manganese(V)-oxo complex, [Mn(V)(O)(TAML)](-) (1), was synthesized by activating dioxygen in the presence of olefins with weak allylic C-H bonds and characterized structurally and spectroscopically. In mechanistic studies, the formation rate of 1 was found to depend on the allylic C-H bond dissociation energies (BDEs) of olefins, and a kinetic isotope effect (KIE) value of 16 was obtained in the reactions of cyclohexene and cyclohexene-d10. These results suggest that a hydrogen atom abstraction from the allylic C-H bonds of olefins by a putative Mn(IV)-superoxo species, which is formed by binding O2 by a high-spin (S = 2) [Mn(III)(TAML)](-) complex, is the rate-determining step. A Mn(V)-oxo complex binding Sc(3+) ion, [Mn(V)(O)(TAML)](-)-(Sc(3+)) (2), was also synthesized in the reaction of 1 with Sc(3+) ion and then characterized using various spectroscopic techniques. The binding site of the Sc(3+) ion was proposed to be the TAML ligand, not the Mn-O moiety, probably due to the low basicity of the oxo group compared to the basicity of the amide carbonyl group in the TAML ligand. Reactivity studies of the Mn(V)-oxo intermediates, 1 and 2, in oxygen atom transfer and electron-transfer reactions revealed that the binding of Sc(3+) ion at the TAML ligand of Mn(V)-oxo enhanced its oxidizing power with a positively shifted one-electron reduction potential (ΔEred = 0.70 V). This study reports the first example of tuning the second coordination sphere of high-valent metal-oxo species by binding a redox-inactive metal ion at the supporting ligand site, thereby modulating their electron-transfer properties as well as their reactivities in oxidation reactions.

  11. Ship-in-bottle synthesis of NaY zeolite encapsulated Cosalen complex and its catalytic performance for cyclohexane oxidation

    YUAN Xia; LI Fang; LUO He'an


    N,N'-bis(salicylidene)ethylenediiminocobalt (Cosalen) was encapsulated into microporous NaY zeolite via the technique of "ship-in-bottle".The encapsulated complex (Cosalen-NaY) was characterized by Fourier-transform infrared spectrum,ultraviolet-visible spectrum, Bmnauer-Emmett-Teller surface areas, X-ray diffraction,thermogravimetry-differential thermal analysis and scanning electron microscope.The reaction of cyclohexane oxidation using oxygen was chosen to investigate the catalytic performance of Cosalen-NaY, and the effects of oxygen pressure. temperature and reaction time were also studied.The results show that Cosalen complex is encapsulated into the supercage of the zeolite and the structure of NaY zeolite remains integrity and the thermal stabilitv of Cosalen is greatly enhanced after encapsulation.Cosalen-NaY shows the better activity in the oxidation of eyclohexane without reductant and solvent.The conversion of cyclohexane is up to 13.4%at 150 ℃ for 3 h under oxygen pressure of 0.85 MPa, with the higher total selectivity to cyclohexanol, cyclohexanone, cyclohexyl hydroperoxide(CHHP)and acid (79.2%)than the neat complex(55.5%). NaY zeolite carrier maybe contributes to the results. There is no obviPUS induction period to initiate the reaction;furthermore. the amount of CHHP among the products is small, which indicates that the Cosalen-NaY has the strong abilitv to accelerate the decomposition of CHHP. Recycling tests show that the hybrid material can be used repeatedly with a negligible loss of active sites.

  12. Dinuclear Pt(II)-bisphosphonate complexes: a scaffold for multinuclear or different oxidation state platinum drugs.

    Piccinonna, Sara; Margiotta, Nicola; Pacifico, Concetta; Lopalco, Antonio; Denora, Nunzio; Fedi, Serena; Corsini, Maddalena; Natile, Giovanni


    Geminal bisphosphonates (BPs), used in the clinic for the treatment of hypercalcaemia and skeletal metastases, have been also exploited for promoting the specific accumulation of platinum antitumor drugs in bone tissue. In this work, the platinum dinuclear complex [{Pt(en)}(2)(μ-AHBP-H(2))](+) (1) (the carbon atom bridging the two phosphorous atoms carrying a 2-ammonioethyl and a hydroxyl group, AHBP-H(2)) has been used as scaffold for the synthesis of a Pt(II) trinuclear complex, [{Pt(en)}(3)(μ-AHBP)](+) (2), and a Pt(IV) adamantane-shaped dinuclear complex featuring an oxo-bridge, [{Pt(IV)(en)Cl}(2)(μ-O)(μ-AHBP-H(2))](+) (3) (X-ray structure). Compound 2 undergoes a reversible, pH dependent, rearrangement with a neat switch point around pH = 5.4. Compound 3 undergoes a one-step electrochemical reduction at E(pc) = -0.84 V affording compound 1. Such a potential is far lower than that of glutathione (-0.24 V), nevertheless compound 3 can undergo chemical reduction to 1 by GSH, most probably through a different (inner-sphere) mechanism. In vitro cytotoxicity of the new compounds, tested against murine glioma (C6) and human cervix (HeLa) and hepatoma (HepG2) cell lines, has shown that, while the Pt(IV) dimer 3 is inactive up to a concentration of 50 μM, the two Pt(II) polynuclear compounds 1 and 2 have a cytotoxicity comparable to that of cisplatin with the trinuclear complex 2 generally more active than the dinuclear complex 1.

  13. Synthesis and catalytic property of Cu-Mn-Ce/ γ -Al2O3 complex oxide

    黄可龙; 王红霞; 刘素琴; 桂客


    A new type of catalytic material for purification of automobile exhaust,Cu-Mn-Ce-O/ γ -Al2O3,has been studied.The factors affecting its catalytic activity,such as calcination temperature and the period of calcinations and so on have been investigated.Its catalytic activity after SO2-poisoning was determined in a fixed-bed reactor by exposing the sample to the atmosphere of 160 mL/min SO2/air.The study reveals that the catalyst has shown high catalytic activities for the conversion of NH3 oxidation by NO after sulfate.The conversion of NO reduction over the sulfated catalyst is somewhat higher than that over the fresh catalyst except that the optimum temperature has increased about 100 ℃.Also at the optimum process for the experiment,the selective catalytic oxidation of CO by NO is over 76% and the conversion of NO reduction is over 80% by NH3.

  14. Thin films of metal oxides grown by chemical vapor deposition from volatile transition metal and lanthanide metal complexes

    Pollard, Kimberly Dona


    This thesis describes the synthesis and characterization of novel volatile metal-organic complexes for the chemical vapor deposition (CVD) of metal oxides. Monomeric tantalum complexes, lbrack Ta(OEt)sb4(beta-diketonate)) are prepared by the acid-base reaction of lbrack Tasb2(OEt)sb{10}rbrack with a beta-diketone, (RC(O)CHsb2C(O)Rsp' for R = CHsb3, Rsp' = CFsb3; R = Rsp'=C(CHsb3)sb3; R = Csb3Fsb7,\\ Rsp'=C(CHsb3)sb3;\\ R=Rsp'=CFsb3; and R = Rsp' = CHsb3). The products are characterized spectroscopically. Thermal CVD using these complexes as precursors gave good quality Tasb2Osb5 thin films which are characterized by XPS, SEM, electrical measurements, and XRD. Factors affecting the film deposition such as the type of carrier gas and the temperature of the substrate were considered. Catalyst-enhanced CVD reactions with each of the precursors and a palladium catalyst, ((2-methylallyl)Pd(acac)), were studied as a lower temperature route to good quality Tasb2Osb5 films. The decomposition mechanism at the hot substrate surface was studied. Precursors for the formation of yttria by CVD were examined. New complexes of the form (Y(hfac)sb3(glyme)), (hfac = \\{CFsb3C(O)CHC(O)CFsb3\\}sp-,\\ glyme=CHsb3O(CHsb2CHsb2O)sb{n}CHsb3 for n = 1-4) were synthesized and characterized spectroscopically. X-ray structural determinations of three new complexes were obtained. CVD reaction conditions were determined which give YOF films and, with catalyst-enhanced CVD, reaction conditions which give selective formation of Ysb2Osb3, YOF, or YFsb3. The films were studied by XPS, SEM, and XRD. Decomposition mechanisms which lead to film formation, together with a possible route for fluorine atom transfer from the ligand to the metal resulting in fluorine incorporation, were studied by analysis of exhaust products using GC-MS. Novel precursors of the form lbrack Ce(hfac)sb3(glyme)rbrack,\\ (hfac=\\{CFsb3C(O)CHC(O)CFsb3\\}sp-,\\ glyme=CHsb3O(CHsb2CHsb2O)sb{n}CHsb3, n = 1-4) for CVD of ceria were

  15. Electro-oxidation of chlorophenols at glassy carbon electrodes modified with polyNi(II)complexes

    Berrios, Cristhian [Facultad de Quimica y Biologia, Departamento de Ciencias del Ambiente, Universidad de Santiago de Chile (USACh), casilla 40, correo 33, Santiago (Chile); Marco, Jose F.; Gutierrez, Claudio [Instituto de Quimica Fisica ' Rocasolano' , CSIC, C. Serrano, 119, 28006, Madrid (Spain); Ureta-Zanartu, Maria Soledad [Facultad de Quimica y Biologia, Departamento de Ciencias del Ambiente, Universidad de Santiago de Chile (USACh), casilla 40, correo 33, Santiago (Chile)], E-mail:


    The effect of the ligand macrocycle (phenylporphyrin (PP) or phthalocyanine (Pc)) and of the ligand substituent (-NH{sub 2} or -SO{sub 3}{sup -}) on the catalytic activity for the electro-oxidation in a pH 11 buffer electrolyte of 2- and 4-chlorophenol (2-CP and 4-CP), 2,4- and 2,6-dichlorophenol (2,4-DCP and 2,6-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) at glassy carbon electrodes modified with electropolymerized Ni(II) macrocycles was studied. The polyphenolic residue deposited at the electrode surface was characterized by cyclic voltammetry, impedance measurements, ex situ Fourier transform infrared spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). A band of aliphatic C=O stretching in the IR spectrum of the fouling film produced by potential cycling in 2,4,6-TCP indicated that the aromatic ring had been broken, yielding ketones, aldehydes and/or carboxylic acids. The sulphonated Ni(II) polymers, which showed the Ni(III)/Ni(II) process in the CV, had XP spectra typical of paramagnetic Ni(II), indicating that they contained Ni(OH){sub 2} clusters. On the contrary, the CVs of the amino Ni(II) did not show the Ni(III)/Ni(II) process at all, this process appearing only after previous activation by potential cycling, and only to a small extent. As was to be expected, the XP spectra of activated amino films corresponded to diamagnetic Ni(II), showing that the concentration of Ni(OH){sub 2} clusters was very small. The amino films were less active than the sulpho films for the oxidation of chlorophenols, in agreement with the lower concentration of Ni(OH){sub 2} clusters in the former films. For all electrodes the highest activity was observed for 2,4,6-TCP, since its oxidation yields a phenolic residue which is much more porous than those produced by the other CPs.

  16. Halide, amide, cationic, manganese carbonylate, and oxide derivatives of triamidosilylamine uranium complexes.

    Gardner, Benedict M; Lewis, William; Blake, Alexander J; Liddle, Stephen T


    Treatment of the complex [U(Tren(TMS))(Cl)(THF)] [1, Tren(TMS) = N(CH(2)CH(2)NSiMe(3))(3)] with Me(3)SiI at room temperature afforded known crystalline [U(Tren(TMS))(I)(THF)] (2), which is reported as a new polymorph. Sublimation of 2 at 160 °C and 10(-6) mmHg afforded the solvent-free dimer complex [{U(Tren(TMS))(μ-I)}(2)] (3), which crystallizes in two polymorphic forms. During routine preparations of 1, an additional complex identified as [U(Cl)(5)(THF)][Li(THF)(4)] (4) was isolated in very low yield due to the presence of a slight excess of [U(Cl)(4)(THF)(3)] in one batch. Reaction of 1 with one equivalent of lithium dicyclohexylamide or bis(trimethylsilyl)amide gave the corresponding amide complexes [U(Tren(TMS))(NR(2))] (5, R = cyclohexyl; 6, R = trimethylsilyl), which both afforded the cationic, separated ion pair complex [U(Tren(TMS))(THF)(2)][BPh(4)] (7) following treatment of the respective amides with Et(3)NH·BPh(4). The analogous reaction of 5 with Et(3)NH·BAr(f)(4) [Ar(f) = C(6)H(3)-3,5-(CF(3))(2)] afforded, following addition of 1 to give a crystallizable compound, the cationic, separated ion pair complex [{U(Tren(TMS))(THF)}(2)(μ-Cl)][BAr(f)(4)] (8). Reaction of 7 with K[Mn(CO)(5)] or 5 or 6 with [HMn(CO)(5)] in THF afforded [U(Tren(TMS))(THF)(μ-OC)Mn(CO)(4)] (9); when these reactions were repeated in the presence of 1,2-dimethoxyethane (DME), the separated ion pair [U(Tren(TMS))(DME)][Mn(CO)(5)] (10) was isolated instead. Reaction of 5 with [HMn(CO)(5)] in toluene afforded [{U(Tren(TMS))(μ-OC)(2)Mn(CO)(3)}(2)] (11). Similarly, reaction of the cyclometalated complex [U{N(CH(2)CH(2)NSiMe(2)Bu(t))(2)(CH(2)CH(2)NSiMeBu(t)CH(2))}] with [HMn(CO)(5)] gave [{U(Tren(DMSB))(μ-OC)(2)Mn(CO)(3)}(2)] [12, Tren(DMSB) = N(CH(2)CH(2)NSiMe(2)Bu(t))(3)]. Attempts to prepare the manganocene derivative [U(Tren(TMS))MnCp(2)] from 7 and K[MnCp(2)] were unsuccessful and resulted in formation of [{U(Tren(TMS))}(2)(μ-O)] (13) and [MnCp(2)]. Complexes 3-13 have been

  17. Mitochondrial Oxidative Stress due to Complex I Dysfunction Promotes Fibroblast Activation and Melanoma Cell Invasiveness

    Maria Letizia Taddei


    Full Text Available Increased ROS (cellular reactive oxygen species are characteristic of both fibrosis and tumour development. ROS induce the trans-differentiation to myofibroblasts, the activated form of fibroblasts able to promote cancer progression. Here, we report the role of ROS produced in response to dysfunctions of mitochondrial complex I, in fibroblast activation and in tumour progression. We studied human fibroblasts with mitochondrial dysfunctions of complex I, leading to hyperproduction of ROS. We demonstrated that ROS level produced by the mutated fibroblasts correlates with their activation. The increase of ROS in these cells provides a greater ability to remodel the extracellular matrix leading to an increased motility and invasiveness. Furthermore, we evidentiated that in hypoxic conditions these fibroblasts cause HIF-1α stabilization and promote a proinvasive phenotype of human melanoma cells through secretion of cytokines. These data suggest a possible role of deregulated mitochondrial ROS production in fibrosis evolution as well as in cancer progression and invasion.

  18. Synthesis of titanium oxide nanoparticles using DNA-complex as template for solution-processable hybrid dielectric composites

    Ramos, J.C. [Center for Sustainable Materials Chemistry, 153 Gilbert Hall, Oregon State University, Corvallis, OR (United States); Mejia, I.; Murphy, J.; Quevedo, M. [Department of Materials Science and Engineering, University of Texas at Dallas, Dallas, TX (United States); Garcia, P.; Martinez, C.A. [Engineering and Technology Institute, Autonomous University of Ciudad Juarez, Ciudad Juarez, Chihuahua (Mexico)


    Highlights: • We developed a synthesis method to produce TiO{sub 2} nanoparticles using a DNA complex. • The nanoparticles were anatase phase (~6 nm diameter), and stable in alcohols. • Composites showed a k of 13.4, 4.6 times larger than the k of polycarbonate. • Maximum processing temperature was 90 °C. • Low temperature enables their use in low-voltage, low-cost, flexible electronics. - Abstract: We report the synthesis of TiO{sub 2} nanoparticles prepared by the hydrolysis of titanium isopropoxide (TTIP) in the presence of a DNA complex for solution processable dielectric composites. The nanoparticles were incorporated as fillers in polycarbonate at low concentrations (1.5, 5 and 7 wt%) to produce hybrid dielectric films with dielectric constant higher than thermally grown silicon oxide. It was found that the DNA complex plays an important role as capping agent in the formation and suspension stability of nanocrystalline anatase phase TiO{sub 2} at room temperature with uniform size (∼6 nm) and narrow distribution. The effective dielectric constant of spin-cast polycarbonate thin-films increased from 2.84 to 13.43 with the incorporation of TiO{sub 2} nanoparticles into the polymer host. These composites can be solution processed with a maximum temperature of 90 °C and could be potential candidates for its application in low-cost macro-electronics.

  19. One-step electrochemical deposition of Schiff base cobalt complex as effective water oxidation catalyst

    Huang, Binbin; Wang, Yan; Zhan, Shuzhong; Ye, Jianshan


    Schiff base metal complexes have been applied in many fields, especially, a potential homogeneous catalyst for water splitting. However, the high overpotential, time consumed synthesis process and complicated working condition largely limit their application. In the present work, a one-step approach to fabricate Schiff base cobalt complex modified electrode is developed. Microrod clusters (MRC) and rough spherical particles (RSP) can be obtained on the ITO electrode through different electrochemical deposition condition. Both of the MRC and RSP present favorable activity for oxygen evolution reaction (OER) compared to the commercial Co3O4, taking an overpotential of 650 mV and 450 mV to drive appreciable catalytic current respectively. The highly active and stable RSP shows a Tafel plot of 84 mV dec-1 and negligible decrease of the current density for 12 h bulk electrolysis. The synthesis strategy of effective and stable catalyst in this work provide a simple method to fabricate heterogeneous OER catalyst with Schiff base metal complex.

  20. The Resistance of Electron Transport Chain Fe-S Clusters to Oxidative Damage during the Reaction of Peroxynitrite with Mitochondrial Complex II and Rat Heart Pericardium

    Pearce, Linda L.; Martinez-Bosch, Sandra; Manzano, Elisenda Lopez; Winnica, Daniel E.; Epperly, Michael W.; Peterson, Jim


    The effects of peroxynitrite and nitric oxide on the iron-sulfur clusters in complex II (succinate dehydrogenase) isolated from bovine heart have been studied primarily by EPR spectroscopy and no measurable damage to the constitutive 2Fe-2S, 3Fe-4S, or 4Fe-4S clusters was observed. The enzyme can be repeatedly oxidized with a slight excess of peroxynitrite and then quantitatively re-reduced with succinate. When added in large excess, peroxynitrite reacted with at least one tyrosine in each subunit of complex II to form 3-nitrotyrosines, but activity was barely compromised. Examination of rat-heart pericardium subjected to conditions leading to peroxynitrite production showed a small inhibition of complex II (16%) and a greater inhibition of aconitase (77%). In addition, experiments performed with excesses of sodium citrate and sodium succinate on rat-heart pericardium indicated that the “g ~2.01” EPR signal observed immediately following the beginning of conditions modeling oxidative/nitrosative stress, could be a consequence of both reversible oxidation of the constitutive 3Fe-4S cluster in complex II and degradation of the 4Fe-4S cluster in aconitase. However, the net signal envelope, which becomes apparent in less than one minute following the start of oxidative/nitrosative conditions, is dominated by the component arising from complex II. Taking into account the findings of a previous study concerning complexes I and III [L.L. Pearce, A.J. Kanai, M.W. Epperly, J. Peterson (2005) Nitric Oxide 13, 254-63] it is now apparent that, with the exception of the cofactor in aconitase, mammalian (mitochondrial) iron-sulfur clusters are surprisingly resistant to degradation stemming from oxidative/nitrosative stress. PMID:19118636

  1. Adsorption and Wetting in Model Mesoporous Silicas and in Complex Metal Oxide Catalysts

    Jayaraman, Karthik

    The surface of most metal oxides is covered by hydroxyl groups which influence many surface phenomena such as adsorption and wetting, catalysis and surface reactions. Surface chemistry of silica is a subject of exhaustive studies owing to a wide variety of practical applications of silica. In Chapter 1, a brief review of classification, synthesis and characterization of silica is provided. The hydroxylation of silica surface i.e the number of hydroxyl (-OH) groups on the surface is of utmost importance for its practical applications. In Chapter 2, a brief introduction to surface hydration of silica is provided followed by the gas adsorption measurements and characterization. Pore wetting is critical to many applications of mesoporous adsorbents, catalysts, and separation materials. In the work presented in Chapter 3, we employed the combined vapor adsorption study using nitrogen (77K) and water (293K) isotherms to evaluate the water contact angles for a series of ordered mesoporous silicas (ex:SBA-15). The proposed method of contact angle relies on the statistical film thickness (t-curve) of the adsorbed water. There were no t-curves for water for dehydroxylated or hydrophobic surfaces in literature and we addressed this issue by measuring t-curves for a series of model surfaces with known and varying silanol coverage. Using the radius of menisci ((H2O)), statistical film thickness t(H2O) from water isotherm, and the true radius of pores (rp(N 2)), from nitrogen isotherms, the water contact angle inside pores were calculated. As it was anticipated, the results obtained showed that the silica pore contact angles were strongly influenced by the number of the surface silanol groups and, therefore, by the thermal and hydration treatments of silicas. Phthalocyanines (Pcs) present an interesting class of catalytically active of molecules with unique spectroscopic, photoelectric, and sometimes magnetic properties. In the work presented in Chapter 4, we have undertaken a

  2. Competition between covalent bonding and charge transfer at complex-oxide interfaces.

    Salafranca, Juan; Rincón, Julián; Tornos, Javier; León, Carlos; Santamaria, Jacobo; Dagotto, Elbio; Pennycook, Stephen J; Varela, Maria


    Here we study the electronic properties of cuprate-manganite interfaces. By means of atomic resolution electron microscopy and spectroscopy, we produce a subnanometer scale map of the transition metal oxidation state profile across the interface between the high Tc superconductor YBa2Cu3O7-δ and the colossal magnetoresistance compound (La,Ca)MnO3. A net transfer of electrons from manganite to cuprate with a peculiar nonmonotonic charge profile is observed. Model calculations rationalize the profile in terms of the competition between standard charge transfer tendencies (due to band mismatch), strong chemical bonding effects across the interface, and Cu substitution into the Mn lattice, with different characteristic length scales.

  3. A theory for bioinorganic chemical reactivity of oxometal complexes and analogous oxidants: the exchange and orbital-selection rules.

    Usharani, Dandamudi; Janardanan, Deepa; Li, Chunsen; Shaik, Sason


    Over the past decades metalloenzymes and their synthetic models have emerged as an area of increasing research interest. The metalloenzymes and their synthetic models oxidize organic molecules using oxometal complexes (OMCs), especially oxoiron(IV)-based ones. Theoretical studies have helped researchers to characterize the active species and to resolve mechanistic issues. This activity has generated massive amounts of data on the relationship between the reactivity of OMCs and the transition metal's identity, oxidation state, ligand sphere, and spin state. Theoretical studies have also produced information on transition state (TS) structures, reaction intermediates, barriers, and rate-equilibrium relationships. For example, the experimental-theoretical interplay has revealed that nonheme enzymes carry out H-abstraction from strong C-H bonds using high-spin (S = 2) oxoiron(IV) species with four unpaired electrons on the iron center. However, other reagents with higher spin states and more unpaired electrons on the metal are not as reactive. Still other reagents carry out these transformations using lower spin states with fewer unpaired electrons on the metal. The TS structures for these reactions exhibit structural selectivity depending on the reactive spin states. The barriers and thermodynamic driving forces of the reactions also depend on the spin state. H-Abstraction is preferred over the thermodynamically more favorable concerted insertion into C-H bonds. Currently, there is no unified theoretical framework that explains the totality of these fascinating trends. This Account aims to unify this rich chemistry and understand the role of unpaired electrons on chemical reactivity. We show that during an oxidative step the d-orbital block of the transition metal is enriched by one electron through proton-coupled electron transfer (PCET). That single electron elicits variable exchange interactions on the metal, which in turn depend critically on the number of

  4. Green oxidation of alkenes in ionic liquid solvent by hydrogen peroxide over high performance Fe(III) Schiff base complexes immobilized on MCM-41

    Mohammad Taghi Goldani; Ali Mohammadi; Reza Sandaroos


    A series of Fe(III) Schiff base complexes immobilized on MCM-41 were prepared and characterized by various physicochemical and spectroscopic methods. The complexes were used for oxidation of cyclohexene by 30% hydrogen peroxide in the presence and absence of ethylmethyl imidazolium chloride (EMIM) ionic liquid as solvent. The immobilized complexes proved to be effective catalysts and generally exhibited much higher catalytic performance than their homogeneous analogue. Catalytic performance of the complexes was also found to be closely related to the Schiff base ligands used. Additionally, ion liquid solvent efficiently improved all the catalytic performances. Finally, the reaction was extended to different alkenes using the heterogeneous complex 2-L4. Among all the alkenes, those containing -electron-withdrawing groups and trans-orientations exhibited lower tendency for oxidation.

  5. Electrochemistry of metal complexes applications from electroplating to oxide layer formation

    Survila, Arvydas


    This book aims to sequentially cover all the major stages of electrochemical processes (mass transport, adsorption, charge transfer), with a special emphasis on their deep interrelation. Starting with general considerations on equilibria in solutions and at interfaces as well as on mass transport, the text acquaints readers with the theory and common experimental practice for studying electrochemical reactions of metals complexes. The core part of the book deals with all important aspects of electroplating, including a systematic discussion of co-deposition of metals and formation of alloys.

  6. Substituents Dependent Capability of bis(ruthenium-dioxolene-terpyridine)Complexes Toward Water Oxidation

    Wada, T.; Muckerman, J.; Fujita, E.; Tanaka, K.


    The bridging ligand, 1,8-bis(2,2':6',2{double_prime}-terpyrid-4'-yl)anthracene (btpyan) was synthesized by the Miyaura-Suzuki cross coupling reaction of anthracenyl-1,8-diboronic acid and 4'-triflyl-2,2':6'-2{double_prime}-terpyridine in the presence of Pd(PPh{sub 3}){sub 4} (5 mol%) with 68% in yield. Three ruthenium-dioxolene dimers, [Ru{sub 2}(OH){sub 2}(dioxolene){sub 2}(btpyan)]{sup 0} (dioxolene = 3,6-di-tert-butyl-1,2-benzosemiquinone ([1]{sup 0}), 3,5-dichloro-1,2-benzosemiquinone ([2]{sup 0}) and 4-nitro-1,2-benzosemiquinone ([3]{sup 0})) were prepared by the reaction of [Ru{sub 2}Cl{sub 6}(btpyan)]{sup 0} with the corresponding catechol. The electronic structure of [1]{sup 0} is approximated by [Ru{sub 2}{sup II}(OH){sub 2}(sq){sub 2}(btpyan)]{sup 0} (sq = semiquinonato). On the other hand, the electronic states of [2]{sup 0} and [3]{sup 0} are close to [Ru{sub 2}{sup III}(OH){sub 2} (cat){sub 2}(btpyan)]{sup 0} (cat = catecholato), indicating that a dioxolene having electron-withdrawing groups stabilizes [Ru{sub 2}{sup III}(OH){sub 2}(cat){sub 2}(btpyan)]{sup 0} rather than [Ru{sub 2}{sup II}(OH){sub 2}(sq){sub 2}(btpyan)]{sup 0} as resonance isomers. No sign was found of deprotonation of the hydroxo groups of [1]{sup 0}, whereas [2]{sup 0} and [3]{sup 0} showed an acid-base equilibrium in treatments with t-BuOLi followed by HClO{sub 4}. Furthermore, controlled potential electrolysis of [1]{sup 0} deposited on an ITO (indium-tin oxide) electrode catalyzed the four-electron oxidation of H{sub 2}O to evolve O{sub 2} at potentials more positive than +1.6 V (vs. SCE) at pH 4.0. On the other hand, the electrolysis of [2]{sup 0} and [3]{sup 0} deposited on ITO electrodes did not show catalytic activity for water oxidation under similar conditions. Such a difference in the reactivity among [1]{sup 0}, [2]{sup 0} and [3]{sup 0} is ascribed to the shift of the resonance equilibrium between [Ru{sub 2}{sup II}(OH){sub 2}(sq){sub 2




    Full Text Available Ceramic materials based on complex oxides with both the perovskite structure (Ln2/3Nb2O6 and the structure of tetragonal tungsten bronze (Ba6-xLn8+2x/3Ti18O54 have been investigated over a wide frequency and temperature ranges. The results obtained for certain structures denote the presence of the temperature anomalies of dielectric parameters (ε, tanδ. These anomalies occur over the wide frequency range including submilimeter (SMM wavelength range, and are related neither with the processing peculiarities nor with the presence of the phase transitions. Temperature behavior of the permittivity has been considered in terms of the polarization mechanism based on the elastic-strain lattice oscillations. It has been assumed that the observed anomalies could be ascribed to a superposition of harmonic and anharmonic contribution to lattice oscillations that determines τε sign and magnitude.

  8. [Preparation and antithrombogenicity of oxidated low molecular weight heparin-antithrombin complex coated-polyvinyl chloride tubing].

    Luo, Peng; Liu, Weiyong; Yang, Chun; Zhou, Hua; Cao, Ruijun; Yang, Jian


    Based on non-enzymatic protein glycated reaction, the sodium periodate-oxidated low molecular weight heparin-antithrombin covalent complex (SPLMWATH) was produced. By using polyethyleneimine-glutaraldehyde bonding technique, polyvinyl chloride (PVC) tubings were coated with SPLMWATH, heparin and low molecular weight heparin (LMWH). Spectrophotometry and dynamic clotting time experiment were used to determine the synthetic ratio of SPLMWATH, graft density, coating leaching ratio and to evaluate the antithrombogenicity of different coating on the PVC tubings. The results showed that the synthetic ratio of SPLMWATH was approximately 55%, and compared with heparin coating and LMWH coating, the graft density of SPLMWATH coating on the PVC tubing was smaller, but its coating stability and antithrombogenicity were significantly better than that of heparin coating and LMWH coating on the PVC tubings.

  9. The effect of thiosulfate-oxidizing bacteria on the stability of the gold-thiosulfate complex

    Lengke, Maggy F.; Southam, Gordon


    An Acidithiobacillus thiooxidans spp., isolated from the Driefontein Consolidated Gold Mine, Witwatersrand Basin, Republic of South Africa was able to precipitate gold from Au(S 2O 3) 23- in the presence of up to 0.26 mM gold. In chemical control experiments and with the presence of dead bacteria, gold was not precipitated under similar experimental conditions and duration. During growth, the pH of the culture medium decreased from pH 5.4 to 1.9, while the Eh increased from 0.3 to between 0.5 to 0.6 V within a period of 75 days. In the active (live) bacterial culture systems, acid production enhanced thiosulfate disproportionation, after which the elemental sulfur and any other intermediate sulfur species were oxidized completely to sulfate. The gold, Au(S 2O 3) 23-, was stable in the bacterial systems until sulfur oxidation was complete; then the bacteria precipitated gold from Au(S 2O 3) 23-. The bacterial systems (0.02-0.26 mM gold) precipitated 87 to 100% of the gold under diurnal light exposure, while only 11 to 69% of the gold was precipitated in the dark. The presence of gold (≥0.08 mM) reduced bacterial growth, disrupted cell division causing cell elongation, and was ultimately toxic to this bacterium, killing the cultures. The gold was precipitated inside the bacterial cells as fine-grained colloids ranging between 5 and 10 nm in diameter and in the bulk fluid phase as crystalline micrometer-scale gold. Observations using transmission electron microscopy revealed that the gold was deposited throughout the cell; however, it was concentrated in the cell envelope, especially along the cytoplasmic membrane, suggesting that gold precipitation was likely enhanced via electron transport processes associated with energy generation. Seven months after population growth had stopped, the gold had formed coiled or wire gold, irregular and rounded structures with an approximate size ranging from 0.5 to 5 μm, and crystalline octahedral gold.

  10. Kinetic effects of sulfur oxidation on catalytic nitrile hydration: nitrile hydratase insights from bioinspired ruthenium(II) complexes.

    Kumar, Davinder; Nguyen, Tho N; Grapperhaus, Craig A


    Kinetic investigations inspired by the metalloenzyme nitrile hydratase were performed on a series of ruthenium(II) complexes to determine the effect of sulfur oxidation on catalytic nitrile hydration. The rate of benzonitrile hydration was quantified as a function of catalyst, nitrile, and water concentrations. Precatalysts L(n)RuPPh3 (n = 1-3; L(1) = 4,7-bis(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(2) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(3) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-sulfenato-propyl)-1-thia-4,7-diazacyclononane) were activated by substitution of triphenylphosphine with substrate in hot dimethylformamide solution. Rate measurements are consistent with a dynamic equilibrium between inactive aqua (L(n)Ru-OH2) and active nitrile (L(n)Ru-NCR) derivatives with K = 21 ± 1, 9 ± 0.9, and 23 ± 3 for L(1) to L(3), respectively. Subsequent hydration of the L(n)Ru-NCR intermediate yields the amide product with measured hydration rate constants (k's) of 0.37 ± 0.01, 0.82 ± 0.07, and 1.59 ± 0.12 M(-1) h(-1) for L(1) to L(3), respectively. Temperature dependent studies reveal that sulfur oxidation lowers the enthalpic barrier by 27 kJ/mol, but increases the entropic barrier by 65 J/(mol K). Density functional theory (DFT) calculations (B3LYP/LanL2DZ (Ru); 6-31G(d) (all other atoms)) support a nitrile bound catalytic cycle with lowering of the reaction barrier as a consequence of sulfur oxidation through enhanced nitrile binding and attack of the water nucleophile through a highly organized transition state.

  11. Total reflection X-ray fluorescence trace mercury determination by trapping complexation: Application in advanced oxidation technologies

    Custo, Graciela [Unidad de Actividad Quimica, Comision Nacional de Energia Atomica, Av. Gral Paz 1499 (B1650KNA) San Martin, Buenos Aires (Argentina); Litter, Marta I. [Unidad de Actividad Quimica, Comision Nacional de Energia Atomica, Av. Gral Paz 1499 (B1650KNA) San Martin, Buenos Aires (Argentina); Escuela de Posgrado, Universidad de General San Martin, San Lorenzo 3391 Villa Ballester, 1653. Prov. de Buenos Aires (Argentina); Rodriguez, Diana [Universidad Nacional de Lujan, Ruta 5 y 7. Prov. de Buenos Aires (Argentina); Vazquez, Cristina [Unidad de Actividad Quimica, Comision Nacional de Energia Atomica, Av. Gral Paz 1499 (B1650KNA) San Martin, Buenos Aires (Argentina) and Laboratorio de Quimica de Sistemas Heterogeneos, Facultad de Ingenieria, Universidad de Buenos Aires, P. Colon 850 (C1063ACU), Buenos Aires (Argentina)]. E-mail:


    It is well known that Hg species cause high noxious effects on the health of living organisms even at very low levels (5 {mu}g/L). Quantification of this element is an analytical challenge due to the peculiar physicochemical properties of all Hg species. The regulation of the maximal allowable Hg concentration led to search for sensitive methods for its determination. Total reflection X-ray fluorescence is a proved instrumental analytical tool for the determination of trace elements. In this work, the use of total reflection X-ray fluorescence for Hg quantification is investigated. However, experimental determination by total reflection X-ray fluorescence requires depositing a small volume of sample on the reflector and evaporation of the solvent until dryness to form a thin film. Because of volatilization of several Hg forms, a procedure to capture these volatile species in liquid samples by using complexing agents is proposed. Acetate, oxalic acid, ethylenediaminetetracetic acid and ammonium pyrrolidine-dithiocarbamate were assayed for trapping the analytes into the solution during the preparation of the sample and onto the reflector during total reflection X-ray fluorescence measurements. The proposed method was applied to evaluate Hg concentration during TiO{sub 2}-heterogeneous photocatalysis, one of the most known advanced oxidation technologies. Advanced oxidation technologies are processes for the treatment of effluents in waters and air that involve the generation of very active oxidative and reductive species. In heterogeneous photocatalysis, Hg is transformed to several species under ultraviolet illumination in the presence of titanium dioxide. Total reflection X-ray fluorescence was demonstrated to be applicable in following the extent of the heterogeneous photocatalysis reaction by determining non-transformed Hg in the remaining solution.

  12. Total reflection X-ray fluorescence trace mercury determination by trapping complexation: Application in advanced oxidation technologies

    Custo, Graciela; Litter, Marta I.; Rodríguez, Diana; Vázquez, Cristina


    It is well known that Hg species cause high noxious effects on the health of living organisms even at very low levels (5 μg/L). Quantification of this element is an analytical challenge due to the peculiar physicochemical properties of all Hg species. The regulation of the maximal allowable Hg concentration led to search for sensitive methods for its determination. Total reflection X-ray fluorescence is a proved instrumental analytical tool for the determination of trace elements. In this work, the use of total reflection X-ray fluorescence for Hg quantification is investigated. However, experimental determination by total reflection X-ray fluorescence requires depositing a small volume of sample on the reflector and evaporation of the solvent until dryness to form a thin film. Because of volatilization of several Hg forms, a procedure to capture these volatile species in liquid samples by using complexing agents is proposed. Acetate, oxalic acid, ethylenediaminetetracetic acid and ammonium pyrrolidine-dithiocarbamate were assayed for trapping the analytes into the solution during the preparation of the sample and onto the reflector during total reflection X-ray fluorescence measurements. The proposed method was applied to evaluate Hg concentration during TiO 2-heterogeneous photocatalysis, one of the most known advanced oxidation technologies. Advanced oxidation technologies are processes for the treatment of effluents in waters and air that involve the generation of very active oxidative and reductive species. In heterogeneous photocatalysis, Hg is transformed to several species under ultraviolet illumination in the presence of titanium dioxide. Total reflection X-ray fluorescence was demonstrated to be applicable in following the extent of the heterogeneous photocatalysis reaction by determining non-transformed Hg in the remaining solution.

  13. An RMND1 Mutation causes encephalopathy associated with multiple oxidative phosphorylation complex deficiencies and a mitochondrial translation defect.

    Janer, Alexandre; Antonicka, Hana; Lalonde, Emilie; Nishimura, Tamiko; Sasarman, Florin; Brown, Garry K; Brown, Ruth M; Majewski, Jacek; Shoubridge, Eric A


    Mutations in the genes composing the mitochondrial translation apparatus are an important cause of a heterogeneous group of oxidative phosphorylation (OXPHOS) disorders. We studied the index case in a consanguineous family in which two children presented with severe encephalopathy, lactic acidosis, and intractable seizures leading to an early fatal outcome. Blue native polyacrylamide gel electrophoretic (BN-PAGE) analysis showed assembly defects in all of the OXPHOS complexes with mtDNA-encoded structural subunits, and these defects were associated with a severe deficiency in mitochondrial translation. Immunoblot analysis showed reductions in the steady-state levels of several structural subunits of the mitochondrial ribosome. Whole-exome sequencing identified a homozygous missense mutation (c.1250G>A) in an uncharacterized gene, RMND1 (required for meiotic nuclear division 1). RMND1 localizes to mitochondria and behaves as an integral membrane protein. Retroviral expression of the wild-type RMND1 cDNA rescued the biochemical phenotype in subject cells, and siRNA-mediated knockdown of the protein recapitulated the defect. BN-PAGE, gel filtration, and mass spectrometry analyses showed that RMND1 forms a high-molecular-weight and most likely homopolymeric complex (∼240 kDa) that does not assemble in subject fibroblasts but that is rescued by expression of RMND1 cDNA. The p.Arg417Gln substitution, predicted to be in a coiled-coil domain, which is juxtaposed to a transmembrane domain at the extreme C terminus of the protein, does not alter the steady-state level of RMND1 but might prevent protein-protein interactions in this complex. Our results demonstrate that the RMND1 complex is necessary for mitochondrial translation, possibly by coordinating the assembly or maintenance of the mitochondrial ribosome. Copyright © 2012 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  14. Density functional theory calculations on the complexation of p-arsanilic acid with hydrated iron oxide clusters: structures, reaction energies, and transition states.

    Adamescu, Adrian; Hamilton, Ian P; Al-Abadleh, Hind A


    Aromatic organoarsenicals, such as p-arsanilic acid (pAsA), are still used today as feed additives in the poultry and swine industries in developing countries. Through the application of contaminated litter as a fertilizer, these compounds enter the environment and interact with reactive soil components such as iron and aluminum oxides. Little is known about these surface interactions at the molecular level. We report density functional theory (DFT) calculations on the energies, optimal geometries, and vibrational frequencies for hydrated pAsA/iron oxide complexes, as well as changes in Gibbs free energy, enthalpy, and entropy for various types of ligand exchange reactions leading to both inner- and outer-sphere complexes. Similar calculations using arsenate are also shown for comparison, along with activation barriers and transition state geometries between inner-sphere complexes. Minimum energy calculations show that the formation of inner- and outer-sphere pAsA/iron oxide complexes is thermodynamically favorable, with the monodentate mononuclear complexes being the most favorable. Interatomic As-Fe distances are calculated to be between 3.3 and 3.5 Å for inner-sphere complexes and between 5.2 and 5.6 Å for outer-sphere complexes. In addition, transition state calculations show that activation energies greater than 23 kJ/mol are required to form the bidentate binuclear pAsA/iron oxide complexes, and that formation of arsenate bidentate binuclear complexes is thermodynamically -rather than kinetically- driven. Desorption thermodynamics using phosphate ions show that reactions are most favorable using HPO4(2-) species. The significance of our results for the overall surface complexation mechanism of pAsA and arsenate is discussed.

  15. Normobaric hyperoxia stimulates superoxide and nitric oxide production in the caudal solitary complex of rat brain slices.

    Ciarlone, Geoffrey E; Dean, Jay B


    Central CO2-chemosensitive neurons in the caudal solitary complex (cSC) are stimulated not only by hypercapnic acidosis, but by hyperoxia as well. While a cellular mechanism for the CO2 response has yet to be isolated, previous data show that a redox-sensitive mechanism underlies neuronal excitability to hyperoxia. However, it remains unknown how changes in Po2 affect the production of reactive oxygen and nitrogen species (RONS) in the cSC that can lead to increased cellular excitability and, with larger doses, to cellular dysfunction and death. To this end, we used fluorescence microscopy in real time to determine how normobaric hyperoxia increases the production of key RONS in the cSC. Because neurons in the region are CO2 sensitive, we also examined the potential effects of CO2 narcosis, used during euthanasia before brain slice harvesting, on RONS production. Our findings show that normobaric hyperoxia (0.4 → 0.95 atmospheres absolute O2) increases the fluorescence rates of fluorogenic dyes specific to both superoxide and nitric oxide. Interestingly, different results were seen for superoxide fluorescence when CO2 narcosis was used during euthanasia, suggesting long-lasting changes in superoxide production and/or antioxidant activity subsequent to CO2 narcosis before brain slicing. Further research needs to distinguish whether the increased levels of RONS reported here are merely increases in oxidative and nitrosative signaling or, alternatively, evidence of redox and nitrosative stress.

  16. Thermodynamic, kinetic and mechanistic investigations of Piperazine oxidation by Diperiodatocuprate(III) complex in aqueous alkaline medium

    Vijay P Pattar; Prashant A Magdum; Deepa G Patil; Sharanappa T Nandibewoor


    The kinetics of oxidation of piperazine by the copper complex, diperiodatocuprate(III) in alkaline medium was studied at 298 K, at an ionic strength of 2.0*10-2 mol dm-3. The reaction between piperazine and diperiodatocuprate(III) in aqueous alkaline medium exhibited 1:2 stoichiometry. The oxidation products were identified by UV-Visible, GC-MS and IR spectral studies. In the present study we have obtained different kinetic observations. The reaction exhibited unit order in case of diperiodatocuprate(III), while less than unit order with respect to piperazine. The addition of alkali and periodate retarded the rate of reaction. The effects of added products, ionic strength and dielectric constant on the rate of the reaction were also studied. The active species of diperiodatocuprate(III) in alkaline media is [Cu(OH)2(H3IO6)]-. The activation parameters with respect to the rate determining step and the thermodynamic quantities with respect to the equilibrium steps were evaluated and discussed. The plausible mechanism consistent with the experimental results was proposed and discussed in detail.

  17. Asymmetric oxidation of vinyl- and ethynyl terthiophene ligands in triruthenium complexes.

    Zhang, Jing; Sun, Chao-Fang; Zhang, Ming-Xing; Hartl, František; Yin, Jun; Yu, Guang-Ao; Rao, Li; Liu, Sheng Hua


    A series of ruthenium(ii) complexes [{RuCl(CO)(PMe3)3(-CH[double bond, length as m-dash]CH-)}nX], (: n = 3, X = 3,3''-dimethyl-2,2':3',2''-terthiophene; : n = 2, X = 2,2'-bithiophene; : n = 2, X = 2,3-bis(3-methylthiophen-2-yl)benzothiophene) and [{Cp*(dppe)2Ru(-C[triple bond, length as m-dash]C-)}3X], (X = 3,3''-dimethyl-2,2':3',2''-terthiophene), were prepared and characterized by (1)H, (13)C and (31)P NMR. Their redox, spectroscopic and bonding properties were studied with a range of spectro-electrochemical methods in combination with density functional theory calculations. The first two anodic steps observed for and are largely localized on the lateral frameworks of the molecular triangle, the direct conjugation between them being precluded due to the photostable open form of the dithienyl ethene moiety. The third anodic step is then mainly localized on the centerpiece of the triangular structure, affecting both bithiophene laterals. The experimental IR and UV-vis-NIR spectroelectrochemical data and, largely, also DFT calculations account for this explanation, being further supported by direct comparison with the anodic behavior of reference diruthenium complexes and .

  18. Oxidative stress promotes SIRT1 recruitment to the GADD34/PP1α complex to activate its deacetylase function.

    Lee, Irene Chengjie; Ho, Xue Yan; George, Simi Elizabeth; Goh, Catherine Wenhui; Sundaram, Jeyapriya Rajameenakshi; Pang, Karen Ka Lam; Luo, Weiwei; Yusoff, Permeen; Sze, Newman Siu Kwan; Shenolikar, Shirish


    Phosphorylation of the eukaryotic translation initiation factor, eIF2α, by stress-activated protein kinases and dephosphorylation by the growth arrest and DNA damage-inducible protein (GADD34)-containing phosphatase is a central node in the integrated stress response. Mass spectrometry demonstrated GADD34 acetylation at multiple lysines. Substituting K(315) and K(322) with alanines or glutamines did not impair GADD34's ability to recruit protein phosphatase 1α (PP1α) or eIF2α, suggesting that GADD34 acetylation did not modulate eIF2α phosphatase activity. Arsenite (Ars)-induced oxidative stress increased cellular GADD34 levels and enhanced Sirtuin 1 (SIRT1) recruitment to assemble a cytoplasmic complex containing GADD34, PP1α, eIF2α and SIRT1. Induction of GADD34 in WT MEFs paralleled the dephosphorylation of eIF2α (phosphoserine-51) and SIRT1 (phosphoserine-47). By comparison, eIF2α and SIRT1 were persistently phosphorylated in Ars-treated GADD34-/- MEFs. Expressing WT GADD34, but not a mutant unable to bind PP1α in GADD34-/- MEFs restored both eIF2α and SIRT1 dephosphorylation. SIRT1 dephosphorylation increased its deacetylase activity, measured in vitro and in cells. Loss of function of GADD34 or SIRT1 enhanced cellular p-eIF2α levels and attenuated cell death following Ars exposure. These results highlighted a novel role for the GADD34/PP1α complex in coordinating the dephosphorylation and reactivation of eIF2α and SIRT1 to determine cell fate following oxidative stress.Cell Death and Differentiation advance online publication, 6 October 2017; doi:10.1038/cdd.2017.152.

  19. Complex dynamics of capillary imbibition of poly(ethylene oxide) melts in nanoporous alumina

    Yao, Yang; Alexandris, Stelios; Henrich, Franziska; Auernhammer, Günter; Steinhart, Martin; Butt, Hans-Jürgen; Floudas, George


    Capillary penetration of a series of entangled poly(ethylene oxide) melts within nanopores of self-ordered alumina follows an approximate t1/2 behavior according to the Lucas-Washburn equation; t is the time. However, the dependence on the capillary diameter deviates from the predicted proportionality to d1/2; d is the pore diameter. We observed a reversal in the dynamics of capillary rise with polymer molecular weight. Chains with 50 entanglements (Mw ≤ 100 kg/mol) or less show a slower capillary rise than theoretically predicted as opposed to chains with more entanglements (Mw ≥ 500 kg/mol) that display a faster capillary rise. Although a faster capillary rise has been predicted by theory and observed experimentally, it is the first time to our knowledge that a slower capillary rise is observed for an entangled polymer melt under conditions of strong confinement (with 2Rg/d = 1). These results are discussed in the light of theoretical predictions for the existence of a critical length scale that depends on the molecular weight and separates the microscopic (d d*) regime.

  20. Effects of Complex Structured Anodic Oxide Dielectric Layer Grown in Pore Matrix for Aluminum Capacitor.

    Shin, Jin-Ha; Yun, Sook Young; Lee, Chang Hyoung; Park, Hwa-Sun; Suh, Su-Jeong


    Anodization of aluminum is generally divided up into two types of anodic aluminum oxide structures depending on electrolyte type. In this study, an anodization process was carried out in two steps to obtain high dielectric strength and break down voltage. In the first step, evaporated high purity Al on Si wafer was anodized in oxalic acidic aqueous solution at various times at a constant temperature of 5 degrees C. In the second step, citric acidic aqueous solution was used to obtain a thickly grown sub-barrier layer. During the second anodization process, the anodizing potential of various ranges was applied at room temperature. An increased thickness of the sub-barrier layer in the porous matrix was obtained according to the increment of the applied anodizing potential. The microstructures and the growth of the sub-barrier layer were then observed with an increasing anodizing potential of 40 to 300 V by using a scanning electron microscope (SEM). An impedance analyzer was used to observe the change of electrical properties, including the capacitance, dissipation factor, impedance, and equivalent series resistance (ESR) depending on the thickness increase of the sub-barrier layer. In addition, the breakdown voltage was measured. The results revealed that dielectric strength was improved with the increase of sub-barrier layer thickness.

  1. Thermophysical properties of perovskite type alkaline-earth metals and plutonium complex oxides

    Tanaka, Kosuke; Sato, Isamu; Hirosawa, Takashi; Kurosaki, Ken; Muta, Hiroaki; Yamanaka, Shinsuke


    Polycrystalline specimens of strontium plutonate, SrPuO3, have been prepared by mixing the appropriate amounts of PuO2 and SrCO3 powders followed by reacting and sintering at 1600 K under the flowing gas atmosphere of dry-air. The sintered specimens had a single phase of orthorhombic perovskite structure and were crack-free. The elastic moduli of SrPuO3 were determined from the longitudinal and shear sound velocities. The Debye temperature was also determined from the sound velocities and lattice parameter measurements. The thermal conductivity of SrPuO3 was calculated from the measured density at room temperature, literature values of heat capacity, and thermal diffusivity measured by laser flash method in vacuum. Although the thermal conductivity of SrPuO3 slightly decreased with increasing temperature to 800 K, the range of change was extremely narrow and the temperature dependence did not completely follow the 1/T law. The thermal conductivity of SrPuO3 was lower than those of other perovskite type oxides.

  2. Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

    Hensling, Felix V. E.; Xu, Chencheng; Gunkel, Felix; Dittmann, Regina


    The reduction of oxides during annealing and growth in low pressure processes is a widely known problem. We hence investigate the influence of mere annealing and of growth in vacuum systems to shed light on the reasons behind the reduction of perovskites. When comparing the existing literature regarding the reduction of the perovskite model material SrTiO3 it is conspicuous that one finds different oxygen pressures required to achieve reduction for vacuum annealing and for chemically controlled reducing atmospheres. The unraveling of this discrepancy is of high interest for low pressure physical vapor depositions of thin films heterostructures to gain further understanding of the reduction of the SrTiO3. For thermal annealing, our results prove the attached measurement devices (mass spectrometer/ cold cathode gauge) to be primarily responsible for the reduction of SrTiO3 in the deposition chamber by shifting the thermodynamic equilibrium to a more reducing atmosphere. We investigated the impact of our findings on the pulsed laser deposition growth at low pressure for LaAlO3/SrTiO3. During deposition the reduction triggered by the presence of the laser plume dominates and the impact of the measurement devices plays a minor role. During post annealing a complete reoxidization of samples is inhibited by an insufficient supply of oxygen.

  3. Preparation and third-order nonlinear optical properties of self-organized complex oxide Ce: BaTiO3 quantum dots

    师文生; 陈正豪; 刘宁宁; 吕惠宾; 周岳亮; 崔大复; 杨国桢


    Pulsed laser ablation epitaxial Strancky-Krastanow growth of self-organized complex oxide Ce:BaTiO3 quantum dots on MgO(100) substrates is demonstrated. Atomic force microscopy and X-ray diffraction are used to observe the structure and the growth process of the self-organized complex oxide quantum dots. The average dimension, height, and the density of self-organized complex oxide Ce:BaTiO3 quantum dots are given. The nonlinear refractive indexes of the wetting layer and the self-organized ordered quantum dots are determined by the single beam Z-scan method. The mechanisms of the nonlinear effect enhancement for these low-dimensional structure are discussed.

  4. Preparation and third-order nonlinear optical properties of self-organized complex oxide Ce:BaTiO3 quantum dots


    Pulsed laser ablation epitaxial Strancky-Krastanow growth of self-organized complex oxide Ce:BaTiO3 quantum dots on MgO(100) substrates is demonstrated.Atomic force microscopy and X-ray diffraction are used to observe the structure and the growth process of the self-organized complex oxide quantum dots.The average dimension,height,and the density of self-organized complex oxide Ce:BaTiO3 quantum dots are given.The nonlinear refractive indexes of the wetting layer and the self-organized ordered quantum dots are determined by the single beam Z-scan method.The mechanisms of the nonlinear effect enhancement for these low-dimensional structure are discussed.

  5. Dinuclear and Trinuclear Nickel Complexes as Effective Catalysts for Alternating Copolymerization on Carbon Dioxide and Cyclohexene Oxide.

    Tsai, Chen-Yen; Cheng, Fu-Yin; Lu, Kuan-Yeh; Wu, Jung-Tsu; Huang, Bor-Hunn; Chen, Wei-An; Lin, Chu-Chieh; Ko, Bao-Tsan


    A series of novel nickel complexes 1-9 supported by NNO-tridentate Schiff-base derivatives have been synthesized and characterized. Treatment of the pro-ligands [L(1)-H = 2,4-di-tert-butyl-6-(((2-(dimethylamino)ethyl)imino)methyl)phenol, L(2)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4,6-bis(2-phenylpropan-2-yl)phenol, L(3)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)phenol] with Ni(OAc)2·4H2O in refluxing ethanol afforded mono- or bimetallic nickel complexes {[(L(1))Ni(OAc)] (1); (L(2))Ni(OAc)] (2); (L(3))2Ni2(OAc)2(H2O)] (3)}. Alcohol-solvated trimetallic nickel acetate complexes {[(L(3))2Ni3(OAc)4(MeOH)2] (4); (L(3))2Ni3(OAc)4(EtOH)2] (5)} could be generated from the reaction of L(3)-H and anhydrous nickel(II) acetate with a ratio of 2:3 in refluxing anhydrous MeOH or EtOH. The reaction of nickel acetate tetrahydrate and L(4)-H to L(6)-H [L(4)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-5-methoxyphenol, L(5)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4-methoxy-phenol, L(6)-H = 2-(((2-(dimethylamino)ethyl)imino)(phenyl)methyl)phenol] produced, respectively, the alcohol-free trinuclear nickel complexes {[(L(4))2Ni3(OAc)4] (7); [(L(5))2Ni3(OAc)4] (8); [(L(6))2Ni3(OAc)4] (9)} with the same ratio in refluxing EtOH under the atmospheric environment. Interestingly, recrystallization of [(L(3))2Ni3(OAc)4(MeOH)] (4) or [(L(3))2Ni3(OAc)4(EtOH)] (5) in the mixed solvent of CH2Cl2/hexane gives [(L(3))2Ni3(OAc)4] (6), which is isostructural with analogues 7-9. All bi- and trimetallic nickel complexes exhibit efficient activity and good selectivity for copolymerization of CO2 with cyclohexene oxide, resulting in copolymers with a high alternating microstructure possessing ≥99% carbonate-linkage content. This is the first example to apply well-defined trinuclear nickel complexes as efficient catalysts for the production of perfectly alternating poly(cyclohexene carbonate).

  6. Copper Complex in Poly(vinyl chloride) as a Nitric Oxide-Generating Catalyst for the Control of Nitrifying Bacterial Biofilms.

    Wonoputri, Vita; Gunawan, Cindy; Liu, Sanly; Barraud, Nicolas; Yee, Lachlan H; Lim, May; Amal, Rose


    In this study, catalytic generation of nitric oxide by a copper(II) complex embedded within a poly(vinyl chloride) matrix in the presence of nitrite (source of nitric oxide) and ascorbic acid (reducing agent) was shown to effectively control the formation and dispersion of nitrifying bacteria biofilms. Amperometric measurements indicated increased and prolonged generation of nitric oxide with the addition of the copper complex when compared to that with nitrite and ascorbic acid alone. The effectiveness of the copper complex-nitrite-ascorbic acid system for biofilm control was quantified using protein analysis, which showed enhanced biofilm suppression when the copper complex was used in comparison to that with nitrite and ascorbic acid treatment alone. Confocal laser scanning microscopy (CLSM) and LIVE/DEAD staining revealed a reduction in cell surface coverage without a loss of viability with the copper complex and up to 5 mM of nitrite and ascorbic acid, suggesting that the nitric oxide generated from the system inhibits proliferation of the cells on surfaces. Induction of nitric oxide production by the copper complex system also triggered the dispersal of pre-established biofilms. However, the addition of a high concentration of nitrite and ascorbic acid to a pre-established biofilm induced bacterial membrane damage and strongly decreased the metabolic activity of planktonic and biofilm cells, as revealed by CLSM with LIVE/DEAD staining and intracellular adenosine triphosphate measurements, respectively. This study highlights the utility of the catalytic generation of nitric oxide for the long-term suppression and removal of nitrifying bacterial biofilms.

  7. Iron Complexes Bearing Diphosphine Ligands with Positioned Pendant Amines as Electrocatalysts for the Oxidation of H2

    Liu, Tianbiao L.; Liao, Qian; O' Hagan, Molly J.; Hulley, Elliott; DuBois, Daniel L.; Bullock, R. Morris


    The synthesis and spectroscopic characterization of CpC5F4NFe(PtBu2NBn2)Cl, [3-Cl] (where C5F4N is the tetrafluorpyridyl substituent and PtBu2NBn2 = 1,5-di(tert-butyl)-3,7-di(benzyl)-1,5-diaza-3,7-diphosphacyclooctane) are reported. Complex 3-Cl and previously reported [CpC5F4NFe(PtBu2NtBu2)Cl], 4-Cl, are precursors to intermediates in the catalytic oxidation of H2, including CpC5F4NFe(PtBu2NBn2)H (3-H), CpC5F4NFe(PtBu2NtBu2)H (4-H), [CpC5F4NFe(PtBu2NBn2)]BArF4 ([3](BArF4), [CpC5F4NFe(PtBu2NtBu2)]BArF4 ([4](BArF4), [CpC5F4NFe(PtBu2NBn2)(H2)]BArF4 ([3-H2]BArF4), and [CpC5F4NFe(PtBu2NtBu2H)H]BArF4 ([4-FeH(NH)]BArF4). All of these complexes were characterized by spectroscopic and electrochemical studies; 3-Cl, 3-H and 4-Cl were also characterized by single crystal diffraction studies. 3-H and 4-H are electrocatalysts for H2 (1.0 atm) oxidation in the presence of a excess of the amine base N-methylpyrrolidine, with turnover frequencies at 22 °C of 2.5 s-1 and 0.5 s-1, and overpotentials at Ecat/2 of 235 mV and 95 mV, respectively. Studies of individual chemical and/or electrochemical reactions of the various intermediates provide important insights into the factors governing the overall catalytic activity for H2 oxidation, and provide important insights into the role of the pendant base of the [FeFe] hydrogenase active site. This work was supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  8. Facile synthesis of Co(II) and Cu(II) complexes of 2-hydroxybenzophenone: An efficient catalyst for oxidation of olefins and DFT study

    Lashanizadegan, Maryam; Alavijeh, Roya Karimi; Anafcheh, Maryam


    Two diketone complexes of Cu(II) and Co(II) were easily synthesized in reaction of M(CH3COO)2 with 2-Hydroxybenzophenone (bpoH). The complexes of M(bpo)2 were characterized by UV-vis, IR spectroscopy, and elemental analysis. The complexes are active catalysts for the oxidation of styrene using TBHP as an oxidant. Under the optimized reaction conditions, 100% conversion of styrene with 63.5% selectivity for Benzaldehyde and 36.5% for Styrene oxide were obtained by Cu(bpo)2. Also, the effect of imidazole was investigated. Results confirmed that the addition of imidazole accelerates the oxidation of styrene. Our DFT results confirmed the necessity of diffuse functions in the basis set and including an accurate treatment of the dispersion energy for obtaining the most stable structure in these systems. Therefore, the geometry optimization and the vibrational frequencies were calculated at the M06-2X/6-311++G(d,p) level. The scaled theoretical frequencies and the structural parameters are in excellent agreement with the experimental data. The natural charge analysis indicated that an electron is transferred from Cu(bpo)2 back to the TBHP to break the Osbnd O bond and formation of tert-butoxyl radicals. Coordination of imidazole in the axial position of the Cu(bpo)2 significantly assists in moving back of electron and increases the activity of the complex in oxidation.

  9. Theoretical and experimental studies of phenol oxidation by ruthenium complex with N,N,N-tris(benzimidazol-2yl-methyl)amine.

    Hernandez, J Guadalupe; Silva, Antonio Romero; Thangarasu, Pandiyan; Najera, Rafael Herrera; Moreno, Alfonso Duran; Ledesma, M Teresa Orta; Cruz-Borbolla, Julian; Singh, Narinder


    The ruthenium complex with (N,N,N-tris(benzimidazol-2yl-methyl)amine, L(1)) was prepared, and characterized. Fukui data were used to localize the reactive sites on the ligand. The structural and electronic properties of the complex were analyzed by DFT in different oxidation states in order to evaluate its oxidant properties for phenol oxidation. The results show that the hard Ru(IV) cation bonds preferentially with a hard base (Namine = amine nitrogen, or axial chloride ion), and soft Ru(II) with a soft base (Nbzim = benzimidazole nitrogen or axial triphenyl phosphine). Furthermore, the Jahn-Teller effect causes an elongation of the axial bond in the octahedral structure. The bonding nature and the orbital contribution to the electronic transitions of the complex were studied. The experimental UV-visible bands were interpreted by using TD-DFT studies. The complex oxidizes phenol to benzoquinone in the presence of H2O2 and the intermediate was detected by HPLC and (13)C NMR. A possible mechanism and rate law are proposed for the oxidation. The adduct formation of phenol with [Ru(O)L(1)](2+) or [Ru(OH)L(1)](+) is theoretically analyzed to show that [Ru(OH)L(1)-OPh](+) could produce the phenol radical.

  10. Sterically (un)encumbered mer-tridentate N-heterocyclic carbene complexes of titanium(iv) for the copolymerization of cyclohexene oxide with CO2.

    Hessevik, Julie; Lalrempuia, Ralte; Nsiri, Hajar; Törnroos, Karl W; Jensen, Vidar R; Le Roux, Erwan


    Titanium(iv) complexes bearing an unsubstituted tridentate bis(phenolate) N-heterocyclic carbene (NHC) were synthesized and structurally identified. While sterically unencumbered NHC-Ti(iv) complexes bearing chloro and alkoxy co-ligands tend to dimerize in solution and in solid-state, the use of a bulky aryloxy as co-ligand favors the monomeric species. Upon activation by onium salts, all these complexes were found to be highly selective towards the copolymerization of cyclohexene oxide (CHO) with CO2 under mild conditions (PCO2 < 1 bar), albeit the sterically unencumbered NHC-Ti(iv) complexes are less stable and active than their structural analogues bearing bulkier substituents.

  11. Synthesis and Defect Structure Analysis of Complex Oxides for Li-Ion Battery Electrodes

    Hao, Xiaoguang

    Lithium-ion batteries have attracted increased attention for energy storage development due to the vast demand from portable electronics, (hybrid) electric vehicles and future power grids. The research in this dissertation is focused on the development of oxide electrodes for lithium-ion batteries with high power density and improved stability. One of the promising cathodes for lithium-ion batteries is lithium manganospinel (LiMn2O4). However, this compound suffers from manganese dissolution and a Jahn-Teller distortion due to Mn3+, especially in oxygen deficient LiMn2O4-delta. Hydrothermal based synthesis methods were developed to eliminate oxygen vacancies to enable high power in cathodes composed of nano-sized spinel particles. The relationship between oxygen defects and the capacity fading mechanism was demonstrated, and collapse of the mechanical structure was identified in defect-rich LiMn 2O4-delta. Next, the nickel substituted manganospinel, LiNi0.5Mn 1.5O4 shows unexpected high voltage side reactions. To overcome this drawback, a thin and chemically inert titanate was used as an artificial SEI (solid electrolyte interface) coating to prohibit transition-metal dissolution and parasitic side reactions, which led to a 200% improvement of the capacity retention at 55°C and negligible polarization losses. Finally, the spinel-structured lithium titanate (Li 4Ti5O12) is introduced as an anode material for lithium-ion batteries due to its higher operating potential and excellent structural stability compared to current graphite anodes. However, the poor electronic conductivity and low lithium diffusion coefficient hinder its wide application. Given these advantages, a facile, low-cost solution method is explored to synthesize nano-sized titanates. Rapid charge/ discharge was achieved up to rates of 100 C (36 second charge/ discharge) due to a shorter lithium mean-free path and better contact between the active material and conductive agents.

  12. A Biomimetic Approach to Discrimination Between Sequential and Concerted Models for the Oxidation of Ubiquinol at the Qo­ site of the Cyt bc1 Complex

    Cape, Jonathan L.; Forquer, Isaac P.; Bowman, Michael K.; Kramer, David M.


    The cytochrome bc complexes function as quinol:cytochrome c oxidoreductases in the energy conserving membranes of nearly all organisms, where they couple the oxidation of a quinol substrate (QH2) to the pumping of protons across the bioenergetic membrane, resulting in the establishment of a proton motive force, which is used to drive the (C)F0/(C)F1 ATP synthase (Trumpower and Gennis 1994). Among the variety of biological quinols characterized, ubiquinol is the substrate used by most bc-type complexes, and its reactions are of great interest concerning diseases related to oxidative stress and the fundamentals of biological energy transduction.

  13. Biogenic SOA formation through gas-phase oxidation and gas-to-particle partitioning – comparison between process models of varying complexity

    E. Hermansson


    Full Text Available Biogenic volatile organic compounds (BVOCs emitted by the vegetation play an important role for the aerosol mass loadings since the oxidation products of these compounds can take part in the formation and growth of secondary organic aerosols (SOA. The concentrations and properties of BVOCs and their oxidation products in the atmosphere are poorly characterized, which leads to high uncertainties in modeled SOA mass and properties. In this study the formation of SOA has been modeled along an air mass trajectory over the northern European boreal forest using two aerosol dynamics box models where the prediction of the condensable organics from the gas-phase oxidation of BVOC is handled with schemes of varying complexity. The use of box model simulations along an air mass trajectory allows us to, under atmospheric relevant conditions, compare different model parameterizations and their effect on SOA formation. The result of the study shows that the modeled mass concentration of SOA is highly dependent on the organic oxidation scheme used to predict the oxidation products. A near-explicit treatment of organic gas-phase oxidation (Master Chemical Mechanism version 3.2 was compared to oxidation schemes that use the volatility basis set (VBS approach. The resulting SOA mass modeled with different VBS-schemes varies by a factor of about 7 depending on how the first generation oxidation products are parameterized and how they subsequently age (e.g. how fast the gas-phase oxidation products react with the OH-radical, how they respond to temperature changes and if they are allowed to fragment during the aging process. Since the VBS approach is frequently used in regional and global climate models due to its relatively simple treatment of the oxidation products compared to near-explicit oxidation schemes; better understanding of the abovementioned processes are needed. Compared to the most commonly used VBS-schemes, the near-explicit method produces less

  14. Klotho Regulates 14-3-3ζ Monomerization and Binding to the ASK1 Signaling Complex in Response to Oxidative Stress.

    Reynolds K Brobey

    Full Text Available The reactive oxygen species (ROS-sensitive apoptosis signal-regulating kinase 1 (ASK1 signaling complex is a key regulator of p38 MAPK activity, a major modulator of stress-associated with aging disorders. We recently reported that the ratio of free ASK1 to the complex-bound ASK1 is significantly decreased in Klotho-responsive manner and that Klotho-deficient tissues have elevated levels of free ASK1 which coincides with increased oxidative stress. Here, we tested the hypothesis that: 1 covalent interactions exist among three identified proteins constituting the ASK1 signaling complex; 2 in normal unstressed cells the ASK1, 14-3-3ζ and thioredoxin (Trx proteins simultaneously engage in a tripartite complex formation; 3 Klotho's stabilizing effect on the complex relied solely on 14-3-3ζ expression and its apparent phosphorylation and dimerization changes. To verify the hypothesis, we performed 14-3-3ζ siRNA knock-down experiments in conjunction with cell-based assays to measure ASK1-client protein interactions in the presence and absence of Klotho, and with or without an oxidant such as rotenone. Our results show that Klotho activity induces posttranslational modifications in the complex targeting 14-3-3ζ monomer/dimer changes to effectively protect against ASK1 oxidation and dissociation. This is the first observation implicating all three proteins constituting the ASK1 signaling complex in close proximity.

  15. Electrocatalytic oxidation of 2-mercaptoethanol using modified glassy carbon electrode by MWCNT in combination with unsymmetrical manganese (II) Schiff base complexes

    Mohebbi, Sajjad, E-mail:; Eslami, Saadat


    Highlights: • High electocatalytic efficiency and stability of modified hybrid electrode GC/MWCNTs/MnSaloph. • Direct reflection of catalytic activity of manganese complexes on electrocatalytic oxidation of 2-ME. • Decreasing overpotential and increasing catalytic peak current toward oxidation of 2-ME. • Deposition of range of novel substituted N{sub 2}O{sub 2} Saloph complexes of manganese(II) on GCE/MWCNT. • Enhancement of electrocatalytic oxidation activity upon electron donating substitutions on the Saloph. - Abstract: The performance of modified hybrid glassy carbon electrode with composite of carbon nanotubes and manganese complexes for the electrocatalytic oxidation of 2-mercaptoethanol is developed. GC electrode was modified using MWCNT and new N{sub 2}O{sub 2} unsymmetrical tetradentate Schiff base complexes of manganese namely Manganese Saloph complexes 1-5, with general formula Mn[(5-x-4-y-Sal)(5-x′-4-y′-Sal) Ph], where x, x′ = H, Br, NO{sub 2} and y, y′ = H, MeO. Direct immobilization of CNT on the surface of GCE is performed by abrasive immobilization, and then modified by manganese(II) complexes via direct deposition method. These novel modified electrodes clearly demonstrate the necessity of modifying bare carbon electrodes to endow them with the desired behavior and were identified by HRTEM. Also complexes were characterized by elemental analyses, MS, UV–vis and IR spectroscopy. Modified hybrid GC/MWCNT/MnSaloph electrode exhibits strong and stable electrocatalytic activity towards the electrooxidation of 2-mercaptoethanol molecules in comparison with bare glassy carbon electrode with advantages of very low over potential and high catalytic current. Such ability promotes the thiol’s electron transfer reaction. Also, electron withdrawing substituent on the Saloph was enhanced electrocatalytic oxidation activity.

  16. General synthesis of transition metal oxides hollow nanospheres/nitrogen-doped graphene hybrids via metal-ammine complex chemistry for high performance lithium ion batteries.

    Chen, Jiayuan; Wu, Xiaofeng; Gong, Yan; Wang, Pengfei; Li, Wenhui; Mo, Shengpeng; Peng, Shengpan; Tan, Qiangqiang; Chen, Yunfa


    We present a general and facile synthesis strategy, on the basis of metal-ammine complex chemistry, in synthesizing hollow transition metal oxides (Co3O4, NiO, CuO-Cu2O and ZnO)/nitrogen-doped graphene hybrids, potentially applied in high performance lithium ion batteries. The oxygen-containing functional groups of graphene oxide play a prerequisite role in the formation of hollow transition metal oxides on graphene nanosheets, and a significant hollowing process occurs only when forming metal (Co2+, Ni2+, Cu2+, or Zn2+)-ammine complex ions. Moreover, the hollowing process is well correlated with complexing capacity between metal ions and NH3 molecules. The significant hollowing process occurs for strong metal-ammine complex ions including Co2+, Ni2+, Cu2+, and Zn2+ ions, and no hollow structures formed for weak and/or non-complex Mn2+ and Fe3+ ions. Simultaneously, this novel strategy can also achieve the directly doping of nitrogen atoms into graphene framework. When used as anodic materials, the electrochemical performance of two typical hollow Co3O4 or NiO/nitrogen-doped graphene hybrids are evaluated. It is demonstrated that these unique nanostructed hybrids, in contrast with the bare counterparts, solid transition metal oxides/nitrogen-doped graphene hybrids, perform the significantly improved specific capacity, superior rate capability and excellent capacity retention. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Indium tin oxide with zwitterionic interfacial design for biosensing applications in complex matrices

    Darwish, Nadia T.; Alias, Yatimah; Khor, Sook Mei, E-mail:


    Graphical abstract: - Highlights: • The incorporation of a linker and antifouling molecules is an important interfacial design for both affinity and enzymatic biosensors. • The resistance to non-specific protein adsorptions of BSA–FITC and RBITC–Cyt c were determined by confocal laser scanning microscopy. • The antifouling interface allows detection of target analytes in highly complicated biological matrices. - Abstract: Biosensing interfaces consisting of linker molecules (COOH or NH{sub 2}) and charged, antifouling moieties ((-SO{sup 3−} and N{sup +}(Me){sub 3}) for biosensing applications were prepared for the first time by the in situ deposition of mixtures of aryl diazonium cations on indium tin oxide (ITO) electrodes. A linker molecule is required for the attachment of biorecognition molecules (e.g., antibodies, enzymes, DNA chains, and aptamers) close to the transducer surface. The attached molecules improve the biosensing sensitivity and also provide a short response time for analyte detection. Thus, the incorporation of a linker and antifouling molecules is an important interfacial design for both affinity and enzymatic biosensors. The reductive adsorption behavior and electrochemical measurement were studied for (1) an individual compound and (2) a mixture of antifouling zwitterionic molecules together with linker molecules [combination 1: 4-sulfophenyl (SP), 4-trimethylammoniophenyl (TMAP), and 1,4-phenylenediamine (PPD); combination 2: 4-sulfophenyl (SP), 4-trimethylammoniophenyl (TMAP), and 4-aminobenzoic acid (PABA)] of aryl diazonium cations grafted onto an ITO electrode. The mixture ratios of SP:TMAP:PPD and SP:TMAP:PABA that provided the greatest resistance to non-specific protein adsorptions of bovine serum albumin labeled with fluorescein isothiocyanate (BSA–FITC) and cytochrome c labeled with rhodamine B isothiocyanate (RBITC–Cyt c) were determined by confocal laser scanning microscopy (CLSM). For the surface antifouling study

  18. Polynuclear Iron-Oxo/Hydroxy Complexes of Ketoacidoximate Ligands: Synthesis, Structures and Conversion to Ferric Oxide

    Davaasuren, Bambar


    The polynuclear iron-oxo/hydroxy complexes containing ketoacidoximate ligands described in this report are [Fe3(μ3-O){O2C-C(C6H5)=NOCH3}6(py)3] (1) (py=pyridine), [Fe2(μ3-O){O2C-C(CH2-C6H5)=NO}2(H2O)(CH3OH)]2 (2) and [{Fe(μ2-OH)(O2C-C(CH3)=NO)}(dmso)]6 (3) (dmso=dimethyl sulfoxide). 1–3 are isolated from the reaction of Fe(NO3)3⋅9H2O and in situ generated anions of ketoacidoximate ligand [(HO2C-C(R1)=NOR2), where R1=CH3, C6H5 and CH2-C6H5; R2=H or CH3] in H2O, followed by crystallization in donor solvents. 1–3 undergo thermal decomposition above 200 °C and form crystalline α-Fe2O3 at 600 °C.

  19. Surfactants present complex joint effects on the toxicities of metal oxide nanoparticles.

    Wang, Dali; Lin, Zhifen; Yao, Zhifeng; Yu, Hongxia


    The potential toxicities of nanoparticles (NPs) have been intensively discussed over the past decade. In addition to their single toxicities, NPs can interact with other environmental chemicals and thereby exert joint effects on biological systems and the environment. The present study investigated the combined toxicities of NPs and surfactants, which are among the chemicals that most likely coexist with NPs. Photobacterium phosphoreum was employed as the model organism. The results indicate that surfactants with different ion types can alter the properties of NPs (i.e., particle size and surface charge) in different ways and present complex joint effects on NP toxicities. Mixtures of different NPs and surfactants exhibited antagonistic, synergistic, and additive effects. In particular, the toxicity of ZnO was observed to result from its dissolved Zn(2+); thus, the joint effects of the ZnO NPs and surfactants can be explained by the interactions between the Zn ions and the surfactants. Our study suggests that the potential hazards caused by mixtures of NPs and surfactants are different from those caused by single NPs. Because surfactants are extensively used in the field of nanotechnology and are likely to coexist with NPs in natural waters, the ecological risk assessments of NPs should consider the impacts of surfactants.

  20. Properties of TRPO-HNO3 complex used for direct dissolution of lanthanide and actinide oxides in supercritical fluid CO2


    The mixed trialkylphosphine oxide-nitric acid (TRPO-HNO3) complex prepared by contacting pure TRPO with concentrated HNO3 may be used as additives for direct dissolution of lanthanide and actinide oxides in the supercritical fluid carbon dioxide (SCF-CO2). Properties of the TRPO-HNO3 complex have been studied. Experimental results show when the initial HNO3/TRPO volume ratio is varied from 1:7 to 5:1, the concentration of HNO3 in the TRPO-HNO3 complex changes from 2.12 to 6.16 mol/L, the [HNO3]/[TRPO] ratio of the TRPO-HNO3 complex changes from 0.93 to 3.38, and the content of H2O in the TRPO-HNO3 complex changes from 0.97% to 2.70%. All of the density, viscosity and surface tension of the TRPO-HNO3 complex change with the concentration of HNO3 in the complex. The protons of HNO3 and H2O in the complex undergo rapid exchange to exhibit a singlet resonance peak in NMR spectra with D2O insert. When the TRPO-HNO3 complex dissolves in a low dielectric constant solvent, small droplets of HNO3 appear which can be detected by NMR.

  1. Pd2+/Pd0 redox cycling in hexagonal YMn(0.5)Fe(0.5)O3: implications for catalysis by PGM-substituted complex oxides.

    Kurzman, Joshua A; Li, Jun; Schladt, Thomas D; Parra, César R; Ouyang, Xiaoying; Davis, Ryan; Miller, Jeffrey T; Scott, Susannah L; Seshadri, Ram


    Complex oxides--containing at least two different cations on crystallographically distinct sites--have recently been shown to display redox cycling of platinum group metals (PGMs), such as Pd; for example, Pd-substituted complex oxides can reversibly extrude metallic Pd under reducing conditions and then reincorporate Pd(2+) ions into the lattice under oxidizing conditions. The title compounds, YMn(0.5)Fe(0.5-x)Pd(x)O(3-δ) (0 ≤ x ≤ 0.07) crystallizing in the noncentrosymmetric YMnO(3) structure, were prepared using a sol-gel process at 800 °C, and the structures were refined from high-resolution synchrotron X-ray powder diffraction data. Their redox cycling behavior was monitored using synchrotron X-ray diffraction and EXAFS studies. In contrast to the previously studied complex oxide host compounds, YMn(0.5)Fe(0.5-x)Pd(x)O(3-δ) is only modestly tolerant to cycling: repeated redox cycling leads to the formation of PdO, which, on the time-scale of the oxidation cycles, does not reincorporate in the complex oxide lattice. Both oxidized and reduced samples were tested for the oxidation of CO to CO(2) under CO-lean conditions. YMn(0.5)Fe(0.5-x)Pd(x)O(3-δ) performs essentially as well as previously studied YFe(1-x)Pd(x)O(3-δ). The CO oxidation light-off characteristics of the hexagonal hosts are very similar to finely dispersed PdO. Despite evidence that Pd is almost fully dispersed as divalent ions in the host lattice, which is presumably accompanied by the concurrent creation of oxygen vacancies (2 Pd(2+):1 V(O(2-))), the as-prepared hexagonal materials do not display any significant improvement in catalytic activity as a function of Pd substitution level. This suggests that the corner-connected trigonal bipyramids that characterize this structural family do not enable the transport of oxygen through the bulk of the lattice. The study casts light on factors in the solid-state chemistry of precious metal-substituted complex oxides that influence the efficacy

  2. Oxidative addition of disulfide/diselenide to group 10 metal(0) and in situ functionalization to form neutral thiasalen/selenasalen group 10 metal(II) complexes.

    Dutta, Pradip Kr; Asatkar, Ashish K; Zade, Sanjio S; Panda, Snigdha


    Three components, one pot synthesis of thiasalen/selenasalen Ni(II), Pd(II) and Pt(II) complexes, 14-19, by the oxidative addition of S-S/Se-Se bond of bis(o-formylphenyl)disulfide/-diselenide to Ni(0), Pd(0) and Pt(0) followed by in situ Schiff base formation with ethylenediamine is reported. S-S or Se-Se bonds were cleaved and coordinated to the metal center as thiolate (ArS(-)) or selenolate (ArSe(-)) while the formal oxidation state of metal centers was changed from '0' to '+2'. The disulfide/diselenide reacted with zero-valent metals at room temperature to give only the monometallic complexes. All complexes (except Pd-thiolate complex 15) were studied by single crystal X-ray crystallography and revealed the square planar geometry around metal centers.

  3. Multi-scale simulation of structural heterogeneity of swift-heavy ion tracks in complex oxides

    Wang, Jianwei; Lang, Maik; Ewing, Rodney C.; Becker, Udo


    Tracks formed by swift-heavy ion irradiation, 2.2 GeV Au, of isometric Gd2Ti2O7 pyrochlore and orthorhombic Gd2TiO5 were modeled using the thermal-spike model combined with a molecular-dynamics simulation. The thermal-spike model was used to calculate the energy dissipation over time and space. Using the time, space, and energy profile generated from the thermal-spike model, the molecular-dynamics simulations were performed to model the atomic-scale evolution of the tracks. The advantage of the combination of these two methods, which uses the output from the continuum model as an input for the atomistic model, is that it provides a means of simulating the coupling of the electronic and atomic subsystems and provides simultaneously atomic-scale detail of the track structure and morphology. The simulated internal structure of the track consists of an amorphous core and a shell of disordered, but still periodic, domains. For Gd2Ti2O7, the shell region has a disordered pyrochlore with a defect fluorite structure and is relatively thick and heterogeneous with different degrees of disordering. For Gd2TiO5, the disordered region is relatively small as compared with Gd2Ti2O7. In the simulation, ‘facets’, which are surfaces with definite crystallographic orientations, are apparent around the amorphous core and more evident in Gd2TiO5 along [010] than [001], suggesting an orientational dependence of the radiation response. These results show that track formation is controlled by the coupling of several complex processes, involving different degrees of amorphization, disordering, and dynamic annealing. Each of the processes depends on the mass and energy of the energetic ion, the properties of the material, and its crystallographic orientation with respect to the incident ion beam.

  4. The Oxidative Coupling of 2,6-Xylenol Catalyzed by Polymeric Complexes of Copper, 1. Kinetic Study of the Catalysis by Copper(II)-Complexes of Partially Aminated Polystyrene

    Schouten, Arend Jan; Prak, Nanno; Challa, Ger


    The oxidative coupling reaction of 2,6-xylenol catalyzed by copper(II) complexes of chemically modified polystyrene was investigated. Under the applied reaction conditions the main reaction product was 2,6,2',6'-tetramethyl-1,1'-dioxo-4,4'-bicyclohexa-2,5-dienylidene. It was found that the polymeric

  5. Mixed N-Heterocyclic Carbene-Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions

    Xu, Songchen [Ames Laboratory; Manna, Kuntal [Ames Laboratory; Ellern, Arkady [Ames Laboratory; Sadow, Aaron D [Ames Laboratory


    In order to facilitate oxidative addition chemistry of fac-coordinated rhodium(I) and iridium(I) compounds, carbene–bis(oxazolinyl)phenylborate proligands have been synthesized and reacted with organometallic precursors. Two proligands, PhB(OxMe2)2(ImtBuH) (H[1]; OxMe2 = 4,4-dimethyl-2-oxazoline; ImtBuH = 1-tert-butylimidazole) and PhB(OxMe2)2(ImMesH) (H[2]; ImMesH = 1-mesitylimidazole), are deprotonated with potassium benzyl to generate K[1] and K[2], and these potassium compounds serve as reagents for the synthesis of a series of rhodium and iridium complexes. Cyclooctadiene and dicarbonyl compounds {PhB(OxMe2)2ImtBu}Rh(η4-C8H12) (3), {PhB(OxMe2)2ImMes}Rh(η4-C8H12) (4), {PhB(OxMe2)2ImMes}Rh(CO)2 (5), {PhB(OxMe2)2ImMes}Ir(η4-C8H12) (6), and {PhB(OxMe2)2ImMes}Ir(CO)2 (7) are synthesized along with ToMM(η4-C8H12) (M = Rh (8); M = Ir (9); ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). The spectroscopic and structural properties and reactivity of this series of compounds show electronic and steric effects of substituents on the imidazole (tert-butyl vs mesityl), effects of replacing an oxazoline in ToM with a carbene donor, and the influence of the donor ligand (CO vs C8H12). The reactions of K[2] and [M(μ-Cl)(η2-C8H14)2]2 (M = Rh, Ir) provide {κ4-PhB(OxMe2)2ImMes'CH2}Rh(μ-H)(μ-Cl)Rh(η2-C8H14)2 (10) and {PhB(OxMe2)2ImMes}IrH(η3-C8H13) (11). In the former compound, a spontaneous oxidative addition of a mesityl ortho-methyl to give a mixed-valent dirhodium species is observed, while the iridium compound forms a monometallic allyl hydride. Photochemical reactions of dicarbonyl compounds 5 and 7 result in C–H bond oxidative addition providing the compounds {κ4-PhB(OxMe2)2ImMes'CH2}RhH(CO) (12) and {PhB(OxMe2)2ImMes}IrH(Ph)CO (13). In 12, oxidative addition results in cyclometalation of the mesityl ortho-methyl similar to 10, whereas the iridium compound reacts with the benzene solvent to give a rare crystallographically characterized cis

  6. Differential regulation of acid sphingomyelinase in macrophages stimulated with oxidized low-density lipoprotein (LDL) and oxidized LDL immune complexes: role in phagocytosis and cytokine release.

    Truman, Jean-Philip; Al Gadban, Mohammed M; Smith, Kent J; Jenkins, Russell W; Mayroo, Nalini; Virella, Gabriel; Lopes-Virella, Maria F; Bielawska, Alicja; Hannun, Yusuf A; Hammad, Samar M


    Oxidized low-density lipoprotein (oxLDL) and oxLDL-containing immune complexes (oxLDL-IC) contribute to the formation of lipid-laden macrophages (foam cells). Fcγ receptors mediate uptake of oxLDL-IC, whereas scavenger receptors internalize oxLDL. We have previously reported that oxLDL-IC, but not free oxLDL, activate macrophages and prolong their survival. Sphingomyelin is a major constituent of cell membranes and lipoprotein particles and acid sphingomyelinase (ASMase) hydrolyses sphingomyelin to generate the bioactive lipid ceramide. ASMase exists in two forms: lysosomal (L-ASMase) and secretory (S-ASMase). In this study we examined whether oxLDL and oxLDL-IC regulate ASMase differently, and whether ASMase mediates monocyte/macrophage activation and cytokine release. The oxLDL-IC, but not oxLDL, induced early and consistent release of catalytically active S-ASMase. The oxLDL-IC also consistently stimulated L-ASMase activity, whereas oxLDL induced a rapid transient increase in L-ASMase activity before it steadily declined below baseline. Prolonged exposure to oxLDL increased L-ASMase activity; however, activity remained significantly lower than that induced by oxLDL-IC. Further studies were aimed at defining the function of the activated ASMase. In response to oxLDL-IC, heat-shock protein 70B' (HSP70B') was up-regulated and localized with redistributed ASMase in the endosomal compartment outside the lysosome. Treatment with oxLDL-IC induced the formation and release of HSP70-containing and IL-1β-containing exosomes via an ASMase-dependent mechanism. Taken together, the results suggest that oxLDL and oxLDL-IC differentially regulate ASMase activity, and the pro-inflammatory responses to oxLDL-IC are mediated by prolonged activation of ASMase. These findings may contribute to increased understanding of mechanisms mediating macrophage involvement in atherosclerosis.

  7. The impact of crystal symmetry on the electronic structure and functional properties of complex lanthanum chromium oxides

    Qiao, Liang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Xiao, Haiyan Y. [Univ. of Tennessee, Knoxville, TN (United States); Heald, Steve M. [Argonne National Lab. (ANL), Argonne, IL (United States); Bowden, Mark E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Varga, Tamas [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Exarhos, Gregory J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Biegalski, Michael D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Ivanov, Ilia N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Weber, William J. [Univ. of Tennessee, Knoxville, TN (United States); Droubay, Timothy C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chambers, Scott A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)


    Complex oxides exhibit a wide range of crystal structures, chemical compositions and physical properties. The underlying drivers determining the complicated structure-composition-property phase diagrams are the relative positions and orbital overlaps between the metal cations and the oxygen anions. Here we report a combined experimental and theoretical investigation of the structure and bonding in a series of lanthanum chromium oxides prepared by reactive molecular beam epitaxy. Of particular interest is the charge state and local coordination of the Cr. We have stabilized LaCrO3, LaCrO4 and La2CrO6 films by controlling the three elemental fluxes during deposition, and have carried out x-ray diffraction, x-ray photoemission, and x-ray absorption spectroscopy, as well as first-principles calculations, to determine structure, charge state, chemical bonding, and electronic structure. Significant changes in bonding character and orbital interaction are revealed with decreasing ligand symmetry from octahedral to tetrahedral Cr coordination. Both LaCrO4 and LaCrO6 with tetrahedrally coordinated Cr show strong pre-edge features in the Cr K-edge near-edge structure whereas LaCrO3 with octahedrally coordinated Cr exhibits very weak pre-edge features. The origin of these pre-edge features is discussed based on various selection rules and ligand symmetry. We also demonstrate an increase in cation-anion orbital hybridization and a decrease in long-range ligand coupling induced by this symmetry reduction. These in turn result in dramatic modifications of the macroscopic optical and magnetic properties.

  8. Mechanistic insights into the oxidation of substituted phenols via hydrogen atom abstraction by a cupric-superoxo complex.

    Lee, Jung Yoon; Peterson, Ryan L; Ohkubo, Kei; Garcia-Bosch, Isaac; Himes, Richard A; Woertink, Julia; Moore, Cathy D; Solomon, Edward I; Fukuzumi, Shunichi; Karlin, Kenneth D


    To obtain mechanistic insights into the inherent reactivity patterns for copper(I)-O2 adducts, a new cupric-superoxo complex [(DMM-tmpa)Cu(II)(O2(•-))](+) (2) [DMM-tmpa = tris((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)amine] has been synthesized and studied in phenol oxidation-oxygenation reactions. Compound 2 is characterized by UV-vis, resonance Raman, and EPR spectroscopies. Its reactions with a series of para-substituted 2,6-di-tert-butylphenols (p-X-DTBPs) afford 2,6-di-tert-butyl-1,4-benzoquinone (DTBQ) in up to 50% yields. Significant deuterium kinetic isotope effects and a positive correlation of second-order rate constants (k2) compared to rate constants for p-X-DTBPs plus cumylperoxyl radical reactions indicate a mechanism that involves rate-limiting hydrogen atom transfer (HAT). A weak correlation of (k(B)T/e) ln k2 versus E(ox) of p-X-DTBP indicates that the HAT reactions proceed via a partial transfer of charge rather than a complete transfer of charge in the electron transfer/proton transfer pathway. Product analyses, (18)O-labeling experiments, and separate reactivity employing the 2,4,6-tri-tert-butylphenoxyl radical provide further mechanistic insights. After initial HAT, a second molar equiv of 2 couples to the phenoxyl radical initially formed, giving a Cu(II)-OO-(ArO') intermediate, which proceeds in the case of p-OR-DTBP substrates via a two-electron oxidation reaction involving hydrolysis steps which liberate H2O2 and the corresponding alcohol. By contrast, four-electron oxygenation (O-O cleavage) mainly occurs for p-R-DTBP which gives (18)O-labeled DTBQ and elimination of the R group.

  9. Synthesis and characterization of mononuclear copper(II) complexes of pyridine 2-carboxamide: Their application as catalyst in peroxidative oxidation and antimicrobial agents

    Suvendu Samanta; Shounak Ray; Sutapa Joardar; Supriya Dutta


    Four water soluble copper(II) complexes, [Cu(HL)2 (H2O)2]Cl2 (1), [Cu(HL) 2 (ClO4)2 ] (2), [Cu(HL)2 (SCN)2] (3) and [CuL 2 ]·8H 2 O (4), where HL is pyridine 2–carboxamide, have been synthesized and characterized by various spectroscopic techniques. Structures have been determined by single crystal X-ray crystallography. The pH induced inter-conversion of Cu(HL)2 (H2O)2 ]Cl2 (1) and [CuL2]·8H2O (4) through co-ordination mode switching was investigated thoroughly with the help of absorption spectroscopy. Complexes 1–3 were found to be active catalysts for the oxidation of toluene, ethyl benzene and cyclohexane in the presence of hydrogen peroxide as the oxidant under mild conditions. Toluene was oxidized to benzyl alcohol and benzaldehyde, ethyl benzene was oxidized to 1-phenylethanol and acetophenone and cyclohexane was oxidized to yield cyclohexanol and cyclohexanone Antimicrobial activities have been investigated with these copper(II) complexes against gram + ve bacteria, gram − ve bacterial and fungal species.

  10. Efficient asymmetric Baeyer-Villiger oxidation of prochiral cyclobutanones using new polymer-supported and unsupported chiral co(salen) complexes

    Reza Sandaroos; Mohammad Taghi Goldani; Saman Damavandi; Ali Mohammadi


    Two heterogeneous catalysts 4 and 5 and three homogenous complexes 1-3 were prepared and used for enantioselective Baeyer-Villiger (B-V) oxidation of prochiral cyclobutanones. Among the prepared catalysts, the supported ones showed better enantioselectivity, good thermal stability and negligible loss of activity over consecutive recycling offset by lower chemical yield.

  11. Films, Needles, and Particles: A Comparative Study on the Ferroic Properties of Complex Oxides Nano-Structured in One, Two, and Three Dimensions


    complex oxides have been observed to possess the properties of insulators , semiconductors, semimetals, metals, and superconductors (3). Ferroic and...are varied independently. To study the film-to- nano-needle and film-to-nano-particle transitions , we have designed Metal- Insulator -Metal (MIM...9 4. Conclusions 11 5. References 12 6. Transitions 14 6.1 Patent Disclosure

  12. Thermoelectric Properties and Microstructure of Modified Novel Complex Cobalt Oxides Sr3RECo4O10.5 (RE = Y, Gd)

    Van Nong, Ngo; Pryds, Nini


    We report on the high-temperature thermoelectric properties and microstructure of modified novel complex cobalt oxides Sr3RECo4O10.5 (RE = Y, Gd), in which the Sr- and Co-sites are partly substituted by Ca and Ga, respectively. We have found that the sample with RE = Gd shows a significant higher...

  13. A novel dinuclear schiff base copper complex as an efficient and cost effective catalyst for oxidation of alcohol: Synthesis, crystal structure and theoretical studies

    Atena Naeimi; Samira Saeednia; Mehdi Yoosefian; Hadi Amiri Rudbari; Viviana Mollica Nardo


    An environmentally friendly protocol is described for an economic, practical laboratory-scale oxidation of primary and secondary alcohols to aldehydes and ketones, using a bis-chloro-bridged binuclear Cu(II) complex [(HL)Cu(2-Cl)2Cu(HL)]*1.5 CH3OH as catalyst. The catalyst was prepared in situ from commercially available reagents and is characterized by single crystal X-ray analysis, FT-IR, UV-visible spectra, mass spectrometry, and powder x-ray diffraction (PXRD). The geometry of the complex has been optimized using the B3LYP level of theory confirming the experimental data. Our results demonstrated well the efficiency, selectivity and stability of this new catalyst in the oxidation of alcohols in ethanol and tert-butyl hydroperoxide (tBuOOH) as a green solvent and oxidant, respectively. Turnover number and reusability have proven the high efficiency and relative stability of the catalyst.

  14. Oxidative stress disassembles the p38/NPM/PP2A complex, which leads to modulation of nucleophosmin-mediated signaling to DNA damage response.

    Guillonneau, Maëva; Paris, François; Dutoit, Soizic; Estephan, Hala; Bénéteau, Elise; Huot, Jacques; Corre, Isabelle


    Oxidative stress is a leading cause of endothelial dysfunction. The p38 MAPK pathway plays a determinant role in allowing cells to cope with oxidative stress and is tightly regulated by a balanced interaction between p38 protein and its interacting partners. By using a proteomic approach, we identified nucleophosmin (NPM) as a new partner of p38 in HUVECs. Coimmunoprecipitation and microscopic analyses confirmed the existence of a cytosolic nucleophosmin (NPM)/p38 interaction in basal condition. Oxidative stress, which was generated by exposure to 500 µM H2O2, induces a rapid dephosphorylation of NPM at T199 that depends on phosphatase PP2A, another partner of the NPM/p38 complex. Blocking PP2A activity leads to accumulation of NPM-pT199 and to an increased association of NPM with p38. Concomitantly to its dephosphorylation, oxidative stress promotes translocation of NPM to the nucleus to affect the DNA damage response. Dephosphorylated NPM impairs the signaling of oxidative stress-induced DNA damage via inhibition of the phosphorylation of ataxia-telangiectasia mutated and DNA-dependent protein kinase catalytic subunit. Overall, these results suggest that the p38/NPM/PP2A complex acts as a dynamic sensor, allowing endothelial cells to react rapidly to acute oxidative stress.-Guillonneau, M., Paris, F., Dutoit, S., Estephan, H., Bénéteau, E., Huot, J., Corre, I. Oxidative stress disassembles the p38/NPM/PP2A complex, which leads to modulation of nucleophosmin-mediated signaling to DNA damage response.

  15. The aerobic oxidation of a Pd(II) dimethyl complex leads to selective ethane elimination from a Pd(III) intermediate.

    Khusnutdinova, Julia R; Rath, Nigam P; Mirica, Liviu M


    Oxidation of the Pd(II) complex (N4)Pd(II)Me(2) (N4 = N,N'-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane) with O(2) or ROOH (R = H, tert-butyl, cumyl) produces the Pd(III) species [(N4)Pd(III)Me(2)](+), followed by selective formation of ethane and the monomethyl complex (N4)Pd(II)Me(OH). Cyclic voltammetry studies and use of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap suggest an inner-sphere mechanism for (N4)Pd(II)Me(2) oxidation by O(2) to generate a Pd(III)-superoxide intermediate. In addition, reaction of (N4)Pd(II)Me(2) with cumene hydroperoxide involves a heterolytic O-O bond cleavage, implying a two-electron oxidation of the Pd(II) precursor and formation of a transient Pd(IV) intermediate. Mechanistic studies of the C-C bond formation steps and crossover experiments are consistent with a nonradical mechanism that involves methyl group transfer and transient formation of a Pd(IV) species. Moreover, the (N4)Pd(II)Me(OH) complex formed upon ethane elimination reacts with weakly acidic C-H bonds of acetone and terminal alkynes, leading to formation of a new Pd(II)-C bond. Overall, this study represents the first example of C-C bond formation upon aerobic oxidation of a Pd(II) dimethyl complex, with implications in the development of Pd catalysts for aerobic oxidative coupling of C-H bonds.

  16. Synthesis, spectroscopic characterization and catalytic oxidation properties of ONO/ONS donor Schiff base ruthenium(III) complexes containing PPh3/AsPh3

    Priyarega; M Muthu Tamizh; R Karvembu; R Prabhakaran; K Natarajan


    Six different ruthenium(III) complexes of Schiff bases derived from 2-hydroxy-1-naphthaldehyde and -aminophenol/-aminothiophenol have been synthesized. The compounds with the general formula [RuX(EPh3)2(L)] (X = Cl or Br; E = P or As; L = bifunctional tridentate ONO/ONS donor Schiff base ligand) were characterized by infrared, electronic, electron paramagnetic resonance spectroscopy and elemental analyses. Spectroscopic investigation reveals coordination of Schiff base ligand through ONO/ONS donor atoms and octahedral geometry around ruthenium metal. Redox property of complexes has been examined by using cyclic voltammetry. The catalytic oxidation property of ruthenium(III) complexes were also investigated.

  17. Extraction of rare earth elements from their oxides using organophosphorus reagent complexes with HNO_3 and H_2O in supercritical CO_2

    段五华; 曹丕佳; 朱永(贝睿)


    Direct extraction of metals from solids with complexing agents in supercritical CO2(SC-CO2) has recently attracted interests in separation,purification,recovery,and analysis of metals.In the present study,the static/dynamic extraction of rare earth elements(Nd,Ce) from their oxides(Nd2O3,CeO2) with organophosphorus complexes with HNO3 and H2O in SC-CO2 was investigated.The static extraction efficiency of Nd from Nd2O3 with the tri-n-butylphosphate(TBP)-HNO3 complex could reach 95% under optimized experiment...

  18. Silica functionalized Cu(II) acetylacetonate Schiff base complex: An efficient catalyst for the oxidative condensation reaction of benzyl alcohol with amines

    Anbarasu, G.; Malathy, M.; Karthikeyan, P.; Rajavel, R.


    Silica functionalized Cu(II) acetylacetonate Schiff base complex via the one pot reaction of silica functionalized 3-aminopropyltriethoxysilane with acetyl acetone and copper acetate has been reported. The synthesized material was well characterized by analytical techniques such as FT-IR, UV-DRS, XRD, SEM-EDX, HR-TEM, EPR, ICP-AES and BET analysis. The characterization results confirmed the grafting of Cu(II) Schiff base complex on the silica surface. The catalytic activity of synthesized silica functionalized Cu(II) acetylacetonate Schiff base complex was evaluated through the oxidative condensation reaction of benzyl alcohol to imine.

  19. Effect of erbium substitution on thermoelectric properties of complex oxide Ca3Co2O6 at high temperatures

    LU Dongqing; CHEN Gang; PEI Jian; YANG Xi; XIAN Hengze


    Polycrystalline particles of Ca3-xErxCo2O6 (x=0.0, 0.15, 0.3, 0.45 and 0.6) were synthesized using sol-gel method combined with Low Temperature Sintering procedure (LTS) to evaluate the effect of Er substitution on the thermoelectric properties of Ca3Co2O6. The crystal structure and microstructure were investigated using X-ray diffraction, infrared spectroscopy and scanning electron microscope. The electrical conductivity and Seebeck coefficient of the complex oxides were measured from 300 to 1073 K. The results showed that all the samples were p-type semiconductors. The electrical conductivity increased with the increase in temperature. Er substitutions at Ca site affected carrier concentrations and carrier mobility, resulting an increase in Seebeck coefficient and decrease in electrical conductivity. The power factor of Ca2.85Er0.15Co2O6 reached 10.66 μw/mK2 at 1073 K.

  20. Study of hafnium (IV) oxide nanoparticles synthesized by polymerized complex and polymer precursor derived sol-gel methods

    Ramos-González, R.


    This work reports the preparation and characterization of hafnium (IV) oxide (HfO2) nanoparticles grown by derived sol-gel routes that involves the formation of an organic polymeric network. A comparison between polymerized complex (PC) and polymer precursor (PP) methods is presented. For the PC method, citric acid (CA) and ethylene glycol (EG) are used as the chelating and polymerizable reagents, respectively. In the case of PP method, poly(acrylic acid) (PAA) is used as the chelating reagent. In both cases, different precursor gels were prepared and the hafnium (IV) chloride (HfCl4) molar ratio was varied from 0.1 to 1.0 for the PC method and from 0.05 to 0.5 for the PP method. In order to obtain the nanoparticles, the precursors were heat treated at 500 and 800 °C. The thermal characterization of the precursor gels was carried out by thermogravimetric analysis (TGA) and the structural and morphological characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns of the samples obtained by both methods shows the formation of HfO2 at 500 °C with monoclinic crystalline phase. The PC method exhibited also the cubic phase. Finally, the HfO2 nanoparticles size (4 to 11 nm) was determined by TEM and XRD patterns. © (2010) Trans Tech Publications.

  1. Evidence for the mitochondrial lactate oxidation complex in rat neurons: demonstration of an essential component of brain lactate shuttles.

    Takeshi Hashimoto

    Full Text Available To evaluate the presence of components of a putative Intracellular Lactate Shuttle (ILS in neurons, we attempted to determine if monocarboxylate (e.g. lactate transporter isoforms (MCT1 and -2 and lactate dehydrogenase (LDH are coexpressed in neuronal mitochondria of rat brains. Immunohistochemical analyses of rat brain cross-sections showed MCT1, MCT2, and LDH to colocalize with the mitochondrial inner membrane marker cytochrome oxidase (COX in cortical, hippocampal, and thalamic neurons. Immunoblotting after immunoprecipitation (IP of mitochondria from brain homogenates supported the histochemical observations by demonstrating that COX coprecipitated MCT1, MCT2, and LDH. Additionally, using primary cultures from rat cortex and hippocampus as well as immunohistochemistry and immunocoprecipitation techniques, we demonstrated that MCT2 and LDH are coexpressed in mitochondria of cultured neurons. These findings can be interpreted to mean that, as in skeletal muscle, neurons contain a mitochondrial lactate oxidation complex (mLOC that has the potential to facilitate both intracellular and cell-cell lactate shuttles in brain.

  2. Real-space observation of metal-insulator transition at complex oxide heterointerface with cross-sectional STM

    Chiu, Ya-Ping; Lin, Jheng-Cyuan; Thanh, Tra-Vu; Lin, Tai-Te; Huang, Po-Cheng; Huang, Bo-Chao; Lin, Jiunn-Yuan; Chu, Ying-Hao

    We report the direct observation of tunable electronic property through visible light at LaAlO3 / SrTiO3 (LAO/STO) complex oxide heterointerface using cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S). Many researches have shown that for the interface to be conducting, the thickness of LAO should be equal to or greater than the critical value 4 unit cells (u.c.). With LAO surface modification by Au clusters, interfacial two-dimensional electron gas presents a giant optical switching effect under visible light illuminated. In this study, through the interaction between photons and electrons system, a direct observation of the evolution of electronic structures from insulating to conducting has been revealed in the LAO (3u.c.)/STO model using the technique of cross-sectional scanning tunneling microscopy and spectroscopy. Results clearly reveal the changes in the built-in electric field in LAO and the band bending in the STO adjacent to the interface after light illumination. National Sun Yat-sen University, Taiwan; Academia Sinica, Taiwan.

  3. Structure–Activity Relationship To Screen Ni–Bisphosphine Complexes for the Oxidative Coupling of CO2 and Ethylene

    Al-Ghamdi, Miasser


    Density functional theory calculations have been used to investigate competition between inner- and outer-sphere reaction pathways in the oxidative coupling of CO2 and ethylene for a set of 12 Ni–bisphosphine complexes, in order to build a QSAR approach correlating catalyst structure to calculated energy barriers for CO2 activation. The ligands were selected to explore different substituents on the P atoms (cyclohexyl, phenyl, and tert-butyl) and different lengths of the tether connecting the P atoms, −(CH2)n– with n = 1–3. As expected, the conclusion is that the inner-sphere reaction pathway is favored with unhindered ligands, while the outer-sphere reaction pathway is favored with hindered ligands. To find a possible correlation with molecular descriptors, we started using the buried volume as a steric descriptor. A reasonable correlation could be found for the energy barrier along the inner-sphere pathway, while scarce correlation was found for the energy barrier along the outer-sphere pathway, indicating that the steric bulkiness of the ligand disfavors approach of CO2 to the metal center. Much stronger correlation between the ligand structure and the energy barrier along the inner-sphere pathway was achieved when the steric descriptor was augmented by an electronic descriptor, consisting of the partial charge on the Ni atom. The much better correlation suggests that bisphosphine ligands have a non-negligible electronic impact on the catalyst performance.

  4. Oxidative formation of phosphinyl radicals from a trigonal pyramidal terminal phosphide Rh(i) complex, with an unusually long Rh-P bond.

    Fischbach, Urs; Trincado, M; Grützmacher, Hansjörg


    A rhodium complex containing a tetrapodal triolefin ligand (trop3P) and a phosphanyl ligand (PPh2(-)) has been prepared and characterised. The special structural confinements of the tetradentate ligand impose an unusually long Rh-PPh2 bond. Chemical oxidation of the complex with FcOTf affords [Rh(OTf)(trop3P)] and plausibly phosphanyl radicals, which react instantly with a spin trap reagent forming a nitroxide-based persistent radical, undergo HAT with silanes or dimerise to the corresponding diphosphine (PPh2)2. Chemical oxidation with a peroxide leads to complex [Rh(POPh2)(trop3P)] which is photolabile and loses the Ph2PO moiety upon irradiation with UV/Vis light in CH2Cl2.

  5. Methylresorcinarene: a reaction vessel to control the coordination geometry of copper(II) in pyridine N-oxide copper(II) complexes.

    Beyeh, Ngong Kodiah; Puttreddy, Rakesh


    Pyridine and 2-picolinic acid N-oxides form 2 : 2 and 2 : 1 ligand : metal (L : M) discrete L2M2 and polymeric complexes with CuCl2 and Cu(NO3)2, respectively, with copper(ii) salts. The N-oxides also form 1 : 1 host-guest complexes with methylresorcinarene. In combination, the three components form a unique 2 : 2 : 1 host-ligand-metal complex. The methylresorcinarene acts as a reaction vessel/protecting group to control the coordination of copper(ii) from cis-see-saw to trans-square planar, and from octahedral to square planar coordination geometry. These processes were studied in solution and in the solid state via(1)H NMR spectroscopy and single crystal X-ray diffraction.

  6. Photochemical nitric oxide precursors: synthesis, photochemistry, and ligand substitution kinetics of ruthenium salen nitrosyl and ruthenium salophen nitrosyl complexes.

    Works, Carmen F; Jocher, Christoph J; Bart, Gwen D; Bu, Xianhui; Ford, Peter C


    Described are syntheses, characterizations, and photochemical reactions of the nitrosyl complexes Ru(salen)(ONO)(NO) (I, salen = N,N'-ethylenebis(salicylideneiminato) dianion), Ru(salen)(Cl)(NO) (II), Ru((t)Bu(4)salen)(Cl)(NO) (III,(t)Bu(4)salen = N,N'-ethylenebis(3,5-di-tert-butylsalicylideneiminato) dianion), Ru((t)Bu(4)salen)(ONO)(NO) (IV), Ru((t)Bu(2)salophen)(Cl)(NO) (V, (t)Bu(2)salophen = N,N'-1,2-phenylenediaminebis(3-tert-butylsalicylideneiminato) dianion), and Ru((t)Bu(4)salophen)(Cl)(NO) (VI, (t)Bu(4)salophen = N,N'-1,2-phenylenebis(3,5-di-tert-butylsalicylideneiminato) dianion). Upon photolysis, these Ru(L)(X)(NO) compounds undergo NO dissociation to give the ruthenium(III) solvento products Ru(L)(X)(Sol). Quantum yields for 365 nm irradiation in acetonitrile solution fall in a fairly narrow range (0.055-0.13) but decreased at longer lambda(irr). The quantum yield (lambda(irr) = 365 nm) for NO release from the water soluble complex [Ru(salen)(H(2)O)(NO)]Cl (VII) was 0.005 in water. Kinetics of thermal back-reactions to re-form the nitrosyl complexes demonstrated strong solvent dependence with second-order rate constants k(NO) varying from 5 x 10(-4) M(-1) s(-1) for the re-formation of II in acetonitrile to 5 x 10(8) M(-1) s(-1) for re-formation of III in cyclohexane. Pressure and temperature effects on the back-reaction rates were also examined. These results are relevant to possible applications of photochemistry for nitric oxide delivery to biological targets, to the mechanisms by which NO reacts with metal centers to form metal-nitrosyl bonds, and to the role of photochemistry in activating similar compounds as catalysts for several organic transformations. Also described are the X-ray crystal structures of I and V.

  7. The role of genomic oxidative-reductive balance as predictor of complex regional pain syndrome development: a novel theory.

    Smith, Howard S


    The aftermath of sequencing the human genome has birthed many efforts to utilize an individual's genetic information in order to tailor optimal treatment strategies - so-called personalized medicine. An individual's genetic information may eventually help diagnosis and treatment, as well selecting optimal pharmacologic agents based partly on how well they reach their target, how well they will bind to and produce an effect at their targets, how well they will be metabolized, and the profile of their adverse effects. It also appears that clinicians may be able to utilize an individual's genetic information to ascertain a subject's risk or susceptibility of developing a particular medical condition. Although, this has not been widely utilized in pain medicine at this point, the future may revolutionize the role of genetic information in the evaluation and management of various pain conditions. One reason for variations in therapeutic outcomes from different pharmacologic pain treatments is the different genetic disposition of patient to develop pain or to respond to analgesics. The patient's phenotype may represent a conglomerate of several different genetic variants concomitantly present in an individual. Genetic variants may modulate the risk of developing a painful condition, or may modulate the perception of pain (e.g. OPRM1 or GCH1 variants conferring modest "protection" from pain by increasing the tone of the endogenous opioid system or decreasing nitric oxide formation). Other genetic polymorphisms may alter pharmacokinetic mechanisms (e.g. CYP2D6 related prodrug activation of codeine to morphine), alter pharmacodynamic mechanisms (e.g. opioid receptor mutations), or alter other analgesic effects (e.g. diminished euphoric effects from opioids potentially due to DRD2 polymorphisms decreasing the functioning of the dopaminergic reward system). This article theorizes that genetic alterations including functional polymorphisms of Nrf2 (a master regulator of the

  8. Complexation of amidocarbamoyl phosphine oxides with Ln{sup +3} (Ln = La, Nd, Pm, Sm and Eu) cation series: structural and thermodynamical features

    Hosseinnejad, Tayebeh; Kazemi, Tayebeh [Alzahra Univ., Tehran (Iran, Islamic Republic of). Dept. of Chemistry


    In the present study, we have mainly investigated the nature of interactions in Ln{sup 3+} (Ln = La, Nd, Pm, Sm, Eu) complexes with amidocarbamoyl methyl phosphine oxide (CMPO) and amidocarbamoyl propyl phosphine oxide (CPPO) ligands based on density functional theory (DFT) approaches. In the first step, thermodynamical properties for complexation of CMPO and CPPO ligands with Ln{sup 3+} cation series have been determined in the gas phase and with the presence of three solvents: n-hexane, chloroform and toluene, via polarized continuum model (PCM) computations. The trend of metal-ligand interaction strength has been analyzed and compared with the trend of ionic hardness within the series of lanthanide cations and different size of alkyl chain of amidocarbamoyl phosphine oxide ligand. The calculated thermochemical results in the gas and solution phases reveals that there is a consistency between increasing trend in the hardness of Ln{sup 3+} cation series and also electron-donating property of alkyl chain with increasing in thermodynamical stability of [Ln-CMPO]{sup 3+} and [Ln-CPPO]{sup 3+} complex series. We have also demonstrated that in the complexation reaction of all complex series, using n-hexane as solvent is more favorable thermodynamically than chloroform and toluene. It should be stated that this issue has been observed in many experiments. Finally, analysis of calculated deformation energies and also the variation in bond order of some selected key bonds in CMPO and CPPO ligands and their corresponded Ln{sup 3+} complexes series show a similar trend with increasing in the hardness of Ln{sup 3+} cation series and electron-donating of alkyl chain of amidocarbamoyl phosphine oxide ligand.

  9. Non-covalent interactions of nitrous oxide with aromatic compounds: Spectroscopic and computational evidence for the formation of 1:1 complexes

    Cao, Qian [Department of Chemistry, P.O. Box 55, University of Helsinki, Helsinki FI-00014 (Finland); School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Gor, Gennady Y., E-mail: [Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Krogh-Jespersen, Karsten [Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903 (United States); Khriachtchev, Leonid [Department of Chemistry, P.O. Box 55, University of Helsinki, Helsinki FI-00014 (Finland)


    We present the first study of intermolecular interactions between nitrous oxide (N{sub 2}O) and three representative aromatic compounds (ACs): phenol, cresol, and toluene. The infrared spectroscopic experiments were performed in a Ne matrix and were supported by high-level quantum chemical calculations. Comparisons of the calculated and experimental vibrational spectra provide direct identification and characterization of the 1:1 N{sub 2}O-AC complexes. Our results show that N{sub 2}O is capable of forming non-covalently bonded complexes with ACs. Complex formation is dominated by dispersion forces, and the interaction energies are relatively low (about −3 kcal mol{sup −1}); however, the complexes are clearly detected by frequency shifts of the characteristic bands. These results suggest that N{sub 2}O can be bound to the amino-acid residues tyrosine or phenylalanine in the form of π complexes.

  10. Non-covalent interactions of nitrous oxide with aromatic compounds: Spectroscopic and computational evidence for the formation of 1:1 complexes

    Cao, Qian; Gor, Gennady Y.; Krogh-Jespersen, Karsten; Khriachtchev, Leonid


    We present the first study of intermolecular interactions between nitrous oxide (N2O) and three representative aromatic compounds (ACs): phenol, cresol, and toluene. The infrared spectroscopic experiments were performed in a Ne matrix and were supported by high-level quantum chemical calculations. Comparisons of the calculated and experimental vibrational spectra provide direct identification and characterization of the 1:1 N2O-AC complexes. Our results show that N2O is capable of forming non-covalently bonded complexes with ACs. Complex formation is dominated by dispersion forces, and the interaction energies are relatively low (about -3 kcal mol-1); however, the complexes are clearly detected by frequency shifts of the characteristic bands. These results suggest that N2O can be bound to the amino-acid residues tyrosine or phenylalanine in the form of π complexes.

  11. Cobalt complexes with pyrazole ligands as catalyst precursors for the peroxidative oxidation of cyclohexane: X-ray absorption spectroscopy studies and biological applications.

    Silva, Telma F S; Martins, Luísa M D R S; Guedes da Silva, M Fátima C; Kuznetsov, Maxim L; Fernandes, Alexandra R; Silva, Ana; Pan, Chun-Jern; Lee, Jyh-Fu; Hwang, Bing-Joe; Pombeiro, Armando J L


    [CoCl(μ-Cl)(Hpz(Ph))3]2 (1) and [CoCl2(Hpz(Ph))4] (2) were obtained by reaction of CoCl2 with HC(pz(Ph))3 and Hpz(Ph), respectively (Hpz(Ph)=3-phenylpyrazole). The compounds were isolated as air-stable solids and fully characterized by IR and far-IR spectroscopy, MS(ESI+/-), elemental analysis, cyclic voltammetry (CV), controlled potential electrolysis, and single-crystal X-ray diffraction. Electrochemical studies showed that 1 and 2 undergo single-electron irreversible Co(II)→Co(III) oxidations and Co(II)→Co(I) reductions at potentials measured by CV, which also allowed, in the case of dinuclear complex 1, the detection of electronic communication between the Co centers through the chloride bridging ligands. The electrochemical behavior of models of 1 and 2 were also investigated by density functional theory (DFT) methods, which indicated that the vertical oxidation of 1 and 2 (that before structural relaxation) affects mostly the chloride and pyrazolyl ligands, whereas adiabatic oxidation (that after the geometry relaxation) and reduction are mostly metal centered. Compounds 1 and 2 and, for comparative purposes, other related scorpionate and pyrazole cobalt complexes, exhibit catalytic activity for the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone under mild conditions (room temperature, aqueous H2O2). In situ X-ray absorption spectroscopy studies indicated that the species derived from complexes 1 and 2 during the oxidation of cyclohexane (i.e., Ox-1 and Ox-2, respectively) are analogous and contain a Co(III) site. Complex 2 showed low in vitro cytotoxicity toward the HCT116 colorectal carcinoma and MCF7 breast adenocarcinoma cell lines.

  12. Magnesium oxide prepared via metal-chitosan complexation method: Application as catalyst for transesterification of soybean oil and catalyst deactivation studies

    Almerindo, Gizelle I.; Probst, Luiz F. D.; Campos, Carlos E. M.; de Almeida, Rusiene M.; Meneghetti, Simoni M. P.; Meneghetti, Mario R.; Clacens, Jean-Marc; Fajardo, Humberto V.


    A simple method to prepare magnesium oxide catalysts for biodiesel production by transesterification reaction of soybean oil with ethanol is proposed. The method was developed using a metal-chitosan complex. Compared to the commercial oxide, the proposed catalysts displayed higher surface area and basicity values, leading to higher yield in terms of fatty acid ethyl esters (biodiesel). The deactivation of the catalyst due to contact with CO2 and H2O present in the ambient air was verified. It was confirmed that the active catalytic site is a hydrogenocarbonate adsorption site.

  13. Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel(II) complex containing proton relays in the second and outer coordination spheres.

    Das, Parthapratim; Ho, Ming-Hsun; O'Hagan, Molly; Shaw, Wendy J; Bullock, R Morris; Raugei, Simone; Helm, Monte L


    A nickel bis(diphosphine) complex containing proton relays in the second and outer coordination spheres, Ni(P(Cy)2N((CH2)2OMe))2, (P(Cy)2N((CH2)2OMe) = 1,5-di(methoxyethyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to the Ni(II) complex results in rapid formation of three isomers of the doubly protonated Ni(0) complex, [Ni(P(Cy)2N((CH2)2OMe)2H)2](2+). The three isomers show fast interconversion at 40 °C, unique to this complex in this class of catalysts. Under conditions of 1.0 atm H2 using H2O as a base, catalytic oxidation proceeds at a turnover frequency of 5 s(-1) and an overpotential of 720 mV, as determined from the potential at half of the catalytic current. Compared to the previously reported Ni(P(Cy)2N(Bn))2 complex, the new complex operates at a faster rate and at a lower overpotential.

  14. From cation to oxide: hydroxylation and condensation of aqueous complexes; Du cation a l'oxyde: hydroxylation et condensation en solution

    Jolivet, J.P. [Universite Pierre et Marie Curie, Chimie de la Matiere Condensee, URA CNRS 1466, 75 - Paris (France)


    Hydroxylation, condensation and precipitation of metal cations in aqueous solution are briefly reviewed. Hydroxylation of aqueous complexes essentially depends on the format charge (oxidation state), the size and the pH of the medium. It is the step allowing the condensation reaction. Depending on the nature of complexes (aqua-hydroxo, oxo-hydroxo), the. mechanism of condensation is different, olation or ox-olation respectively. The first one leads to poly-cations or hydroxides more or less stable against dehydration. The second one leads to poly-anions or oxides. Oligomeric species (poly-cations, poly-anions) are form from charged monomer complexes while the formation of solid phases requires non-charged precursors. Because of their high lability, charged oligomers are never the precursors of solids phases. The main routes for the formation of solid phases from solution are studied with two important and representative elements, Al and Si. For Al{sup 3+} ions, different methods (base addition in solution, thermo-hydrolysis, hydrothermal synthesis) are discussed in relation to the crystal structure of the solid phase obtained. For silicic species condensing by ox-olation, the role of acid or base catalysis on the morphology of gels is studied. The influence of complexing ligands on the processes and on the characteristics of solids (morphology of particles, basic salts and polymetallic oxides formation) is studied. (author)

  15. Study on Properties of TBP-HNO3 Complex Used for Direct Dissolution of Lanthanide and Actinide Oxides in Supercritical Fluid CO2

    DUAN Wu-Hua; ZHU Li-Yang; JING Shan; ZHU Yong-Jun; CHEN Jing


    The tri-n-butyl phosphate-nitric acid (TBP-HNO3) complex prepared by contacting the pure TBP with the concentrated HNO3 can be used for direct dissolution of lanthanide and actinide oxides in the supercritical fluid carbon dioxide (SCF-CO2). Properties of the TBP-HNO3 complex have been studied. Experimental results showed that when the initial HNO3/TBP volume ratio was varied from 1 : 7 to 5 : 1, the concentration of HNO3 in the TBP-HNO3 complex changed from 1.95 to 5.89 mol/L, the [HNO3]/[TBP] ratio of the TBP-HNO3 complex changed from 0.61 to 2.22, and the content of H2O in the TBP-HNO3 complex changed from 2.02% to 4.19%. All of the density, viscosity and surface tension of the TBP-HNO3 complex changed with the concentration of HNO3 in the complex, and were higher than those of the pure TBP. The protons of HNO3 and H2O in the complex underwent rapid exchange to exhibit a singlet resonance peak in nuclear magnetic resonance spectra. When the TBP-HNO3 complex was dissolved in a low dielectric constant solvent, small droplets of HNO3 were formed that can be detected by NMR.

  16. Ferrous sulfate, but not iron polymaltose complex, aggravates local and systemic inflammation and oxidative stress in dextran sodium sulfate-induced colitis in rats

    Toblli JE


    Full Text Available Jorge E Toblli, Gabriel Cao, Margarita Angerosa Laboratory of Experimental Medicine, Hospital Alemán, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina Background and aims: Iron deficiency is common in inflammatory bowel disease, yet oral iron therapy may worsen the disease symptoms and increase systemic and local oxidative stress. The aim of this study was to compare the effects of oral ferrous sulfate and iron polymaltose complex on inflammatory and oxidative stress markers in colitic rats.Methods: Animals were divided into four groups with ten animals each. Rats of three groups received dextran sodium sulfate to induce colitis and animals of two of these groups received 5 mg iron/kg of body weight a day, as ferrous sulfate or iron polymaltose complex, for 7 days. Gross colon anatomy, histology of colon and liver, stainings of L-ferritin, Prussian blue, hepcidin, tumor necrosis factor-α, and interleukin-6, as well serum levels of liver enzymes, inflammatory markers, and iron markers, were assessed.Results: Body weight, gross anatomy, crypt injury and inflammation scores, inflammatory parameters in liver and colon, as well as serum and liver hepcidin levels were not significantly different between colitic animals without iron treatment and colitic animals treated with iron polymaltose complex. In contrast, ferrous sulfate treatment caused significant worsening of these parameters. As opposed to ferrous sulfate, iron polymaltose complex caused less or no additional oxidative stress in the colon and liver compared to colitic animals without iron treatment.Conclusion: Iron polymaltose complex had negligible effects on colonic tissue erosion, local or systemic oxidative stress, and local or systemic inflammation, even at high therapeutic doses, and may thus represent a valuable oral treatment of iron deficiency in inflammatory bowel disease. Keywords: preclinical, oral iron treatment, tolerability, colonic tissue erosion

  17. Ferrous sulfate, but not iron polymaltose complex, aggravates local and systemic inflammation and oxidative stress in dextran sodium sulfate-induced colitis in rats.

    Toblli, Jorge E; Cao, Gabriel; Angerosa, Margarita


    Iron deficiency is common in inflammatory bowel disease, yet oral iron therapy may worsen the disease symptoms and increase systemic and local oxidative stress. The aim of this study was to compare the effects of oral ferrous sulfate and iron polymaltose complex on inflammatory and oxidative stress markers in colitic rats. Animals were divided into four groups with ten animals each. Rats of three groups received dextran sodium sulfate to induce colitis and animals of two of these groups received 5 mg iron/kg of body weight a day, as ferrous sulfate or iron polymaltose complex, for 7 days. Gross colon anatomy, histology of colon and liver, stainings of L-ferritin, Prussian blue, hepcidin, tumor necrosis factor-α, and interleukin-6, as well serum levels of liver enzymes, inflammatory markers, and iron markers, were assessed. Body weight, gross anatomy, crypt injury and inflammation scores, inflammatory parameters in liver and colon, as well as serum and liver hepcidin levels were not significantly different between colitic animals without iron treatment and colitic animals treated with iron polymaltose complex. In contrast, ferrous sulfate treatment caused significant worsening of these parameters. As opposed to ferrous sulfate, iron polymaltose complex caused less or no additional oxidative stress in the colon and liver compared to colitic animals without iron treatment. Iron polymaltose complex had negligible effects on colonic tissue erosion, local or systemic oxidative stress, and local or systemic inflammation, even at high therapeutic doses, and may thus represent a valuable oral treatment of iron deficiency in inflammatory bowel disease.

  18. The oxygen free radicals originating from mitochondrial complex I contribute to oxidative brain injury following hypoxia-ischemia in neonatal mice

    Niatsetskaya, Zoya V.; Sosunov, Sergei A.; Matsiukevich, Dzmitry; Utkina-Sosunova, Irina V.; Ratner, Veniamin I.; Starkov, Anatoly A.; Ten, Vadim S.


    Oxidative stress and Ca++ toxicity are mechanisms of hypoxic-ischemic (HI) brain injury. This work investigates if partial inhibition of mitochondrial respiratory chain protects HI-brain by limiting generation of oxidative radicals during reperfusion. HI-insult was produced in p10 mice treated with complex-I (C-I) inhibitor, pyridaben (P), or vehicle. Administration of P significantly decreased extent of HI injury. Mitochondria isolated from the ischemic hemisphere in P-treated animals showed reduced H2O2 emission, less oxidative damage to the mitochondrial matrix, and increased tolerance to Ca++ triggered opening of permeability transition pore. Protective effect of P administration was also observed when the reperfusion-driven oxidative stress was augmented by the exposure to 100% O2 which exacerbated brain injury only in V-treated mice. In vitro, intact brain mitochondria dramatically increased H2O2 emission in response to hyperoxia, resulting in substantial loss of Ca++ buffering capacity. However, in the presence of C-I inhibitor, rotenone, or antioxidant, catalase, these effects of hyperoxia were abolished. Our data suggest that the reperfusion-driven recovery of C-I dependent mitochondrial respiration contributes not only to the cellular survival, but also causes an oxidative damage to the mitochondria, potentiating a loss of Ca++ buffering capacity. This highlights a novel neuroprotective strategy against HI-brain injury where the major therapeutic principle is a pharmacological attenuation, rather than an enhancement of mitochondrial oxidative metabolism during early reperfusion. PMID:22378894

  19. The oxygen free radicals originating from mitochondrial complex I contribute to oxidative brain injury following hypoxia-ischemia in neonatal mice.

    Niatsetskaya, Zoya V; Sosunov, Sergei A; Matsiukevich, Dzmitry; Utkina-Sosunova, Irina V; Ratner, Veniamin I; Starkov, Anatoly A; Ten, Vadim S


    Oxidative stress and Ca(2+) toxicity are mechanisms of hypoxic-ischemic (HI) brain injury. This work investigates if partial inhibition of mitochondrial respiratory chain protects HI brain by limiting a generation of oxidative radicals during reperfusion. HI insult was produced in p10 mice treated with complex I (C-I) inhibitor, pyridaben, or vehicle. Administration of P significantly decreased the extent of HI injury. Mitochondria isolated from the ischemic hemisphere in pyridaben-treated animals showed reduced H(2)O(2) emission, less oxidative damage to the mitochondrial matrix, and increased tolerance to the Ca(2+)-triggered opening of the permeability transition pore. A protective effect of pyridaben administration was also observed when the reperfusion-driven oxidative stress was augmented by the exposure to 100% O(2) which exacerbated brain injury only in vehicle-treated mice. In vitro, intact brain mitochondria dramatically increased H(2)O(2) emission in response to hyperoxia, resulting in substantial loss of Ca(2+) buffering capacity. However, in the presence of the C-I inhibitor, rotenone, or the antioxidant, catalase, these effects of hyperoxia were abolished. Our data suggest that the reperfusion-driven recovery of C-I-dependent mitochondrial respiration contributes not only to the cellular survival, but also causes oxidative damage to the mitochondria, potentiating a loss of Ca(2+) buffering capacity. This highlights a novel neuroprotective strategy against HI brain injury where the major therapeutic principle is a pharmacological attenuation, rather than an enhancement of mitochondrial oxidative metabolism during early reperfusion.

  20. Polychromophoric metal complexes for generating the bioregulatory agent nitric oxide by single- and two-photon excitation.

    Ford, Peter C


    In order to deliver a bioactive agent to a physiological location, it is important to be able to regulate precisely the location and the dosage. Such exquisite control can easily be envisioned for a photochemical drug that is active toward release of the desired bioactive agent upon irradiation of a specific tissue site. These materials should be thermally stable but reactive under excitation at visible (vis) or near-infrared (NIR) wavelengths where tissue transmission is optimal. Two photon excitation (TPE) is of special interest, since the use of focused laser pulses to activate release could provide 3D spatial control in therapeutic applications. This Account describes the preparation and photochemistry of a series of transition metal complexes designed to release the simple bioregulatory compound nitric oxide upon vis or NIR excitation. In order to enhance the light gathering capability of such compounds, we have attached chromophores with high single- or two-photon absorption cross sections to several photochemical NO precursors. For example, the iron nitrosyl clusters Fe2(mu-SR)2(NO)4 (Roussin's red esters) have been prepared with various chromophores as pendant groups, an example being the protoporphyrin XI derivative illustrated here. Direct excitation into the vis absorbing Q bands of the porphyrin leads to enhanced rates of NO generation from the Fe/S/NO cluster owing to the larger rate of light absorption by that antenna. Furthermore, femtosecond pulsed laser NIR excitation of the same compound at 810 nm (a spectral region where no absorption bands are apparent) leads to weak emission at approximately 630 nm and generation of NO, both effects providing evidence of a TPE mechanism. Roussin's red esters with other chromophores described here are even more effective for TPE-stimulated NO release. Another photochemical NO precursor discussed is the Cr(III) complex trans-Cr(L)(ONO)2(+) where L is a cyclic tetraamine such as cyclam. When L includes a

  1. Simple Detection of the IS6110 Sequence of Mycobacterium tuberculosis Complex in Sputum, Based on PCR with Graphene Oxide.

    Sang-Hyun Hwang

    Full Text Available Graphene oxide (GO has proven to be a satisfactory DNA-sensor platform for applications in enzyme-free signal amplification, fluorescence-based amplification, and nanoparticle-based platforms because of its excellent electrical, thermal, and optical properties. In this study, we designed a novel platform for the fluorescence detection of biomolecules, using a fluorescent dye-labeled primer and GO. We applied this system for the detection of the IS6110 insertion sequence of the Mycobacterium tuberculosis complex (MTB and evaluated its feasibility for use in molecular diagnostics. Fifty-four sputum specimens were collected at our institution from October 2010 to March 2012. To detect MTB in the samples, we performed PCR amplification of the IS6110 DNA sequence using FAM-labeled primers, after which the PCR amplicon was incubated with GO and the fluorescence was measured. The results were compared with those obtained by conventional real-time quantitative PCR (RQ-PCR. The fluorescence intensity observed increased in a concentration-dependent manner with the FAM-labeled IS6110 amplicon. The results of the PCR-GO system for detecting IS6110 DNA were in good agreement with those obtained with conventional RQ-PCR (kappa statistic = 0.925. The PCR-GO system detected MTB DNA in 23 of 25 RQ-PCR-positive sputum samples (92.0%; 95% CI, 75.0-98.0%, but not in 29 of 29 RQ-PCR-negative sputum samples (100%; 95% CI, 88.1-100.0%. These results indicate the utility of the PCR-GO system in molecular diagnostics.

  2. Simple Detection of the IS6110 Sequence of Mycobacterium tuberculosis Complex in Sputum, Based on PCR with Graphene Oxide.

    Hwang, Sang-Hyun; Kim, Dong-Eun; Sung, Heungsup; Park, Byeong-Min; Cho, Mi-Jeong; Yoon, Ok-Jin; Lee, Do-Hoon


    Graphene oxide (GO) has proven to be a satisfactory DNA-sensor platform for applications in enzyme-free signal amplification, fluorescence-based amplification, and nanoparticle-based platforms because of its excellent electrical, thermal, and optical properties. In this study, we designed a novel platform for the fluorescence detection of biomolecules, using a fluorescent dye-labeled primer and GO. We applied this system for the detection of the IS6110 insertion sequence of the Mycobacterium tuberculosis complex (MTB) and evaluated its feasibility for use in molecular diagnostics. Fifty-four sputum specimens were collected at our institution from October 2010 to March 2012. To detect MTB in the samples, we performed PCR amplification of the IS6110 DNA sequence using FAM-labeled primers, after which the PCR amplicon was incubated with GO and the fluorescence was measured. The results were compared with those obtained by conventional real-time quantitative PCR (RQ-PCR). The fluorescence intensity observed increased in a concentration-dependent manner with the FAM-labeled IS6110 amplicon. The results of the PCR-GO system for detecting IS6110 DNA were in good agreement with those obtained with conventional RQ-PCR (kappa statistic = 0.925). The PCR-GO system detected MTB DNA in 23 of 25 RQ-PCR-positive sputum samples (92.0%; 95% CI, 75.0-98.0%), but not in 29 of 29 RQ-PCR-negative sputum samples (100%; 95% CI, 88.1-100.0%). These results indicate the utility of the PCR-GO system in molecular diagnostics.

  3. Comparison of the mechanisms underlying the relaxation induced by two nitric oxide donors: sodium nitroprusside and a new ruthenium complex.

    Bonaventura, Daniella; de Lima, Renata Galvão; Vercesi, Juliana A; da Silva, Roberto Santana; Bendhack, Lusiane M


    We studied the mechanisms involved in the relaxation induced by nitric oxide (NO) donors, ruthenium complex ([Ru(terpy)(bdq)NO(+)](3+)-TERPY) and sodium nitroprusside (SNP) in denuded rat aorta. Both NO donors induced vascular relaxation independent of the agonist used in the pre-contraction. [Ru(terpy)(bdq)NO(+)](3+) and SNP activated guanylyl cyclase (GC) and K(+) channels. The production of cGMP induced by [Ru(terpy)(bdq)NO(+)](3+) - was higher than that obtained with SNP. The combination of GC inhibitor with K(+)channels blocker almost abolished the relaxation induced by the NO donors. The extracellular NO scavenger oxyhemoglobin reduced the potency without changing the maximum effect (Emax) of both NO donors. By using specific NO species scavengers, hydroxocobalamin and l-cysteine, we have identified the contribution of free radical NO (NO()) and nytroxil anion (NO(-)), respectively, to the rat aorta relaxation induced by both NO donors. The selective scavengers for NO() and NO(-) reduced the potency but not the Emax of [Ru(terpy)(bdq)NO(+)](3+). However, the NO(-) scavenger had no effect on the relaxation induced by SNP and NO() scavenger reduced only the potency to SNP. The inhibition of sarcoplasmic reticulum Ca(2+)-ATPase reduced only the potency of SNP without effect on the relaxation induced by [Ru(terpy)(bdq)NO(+)](3+). Our results demonstrate that both NO donors induce relaxation by activating the GC and K(+) channels. The NO() is the unique NO specie involved in the SNP-relaxation. On the other hand, the relaxant effect of [Ru(terpy)(bdq)NO(+)](3+) involves both NO() and NO(-), that produce higher concentration of cGMP. The inhibition of sarcoplasmic reticulum Ca(2+)-ATPase reduces the relaxation induced by SNP but it did not alter the relaxation induced by [Ru(terpy)(bdq)NO(+)](3+).

  4. Mechanistic Insights into the Oxidation of Substituted Phenols via Hydrogen Atom Abstraction by a Cupric–Superoxo Complex


    To obtain mechanistic insights into the inherent reactivity patterns for copper(I)–O2 adducts, a new cupric–superoxo complex [(DMM-tmpa)CuII(O2•–)]+ (2) [DMM-tmpa = tris((4-methoxy-3,5-dimethylpyridin-2-yl)methyl)amine] has been synthesized and studied in phenol oxidation–oxygenation reactions. Compound 2 is characterized by UV–vis, resonance Raman, and EPR spectroscopies. Its reactions with a series of para-substituted 2,6-di-tert-butylphenols (p-X-DTBPs) afford 2,6-di-tert-butyl-1,4-benzoquinone (DTBQ) in up to 50% yields. Significant deuterium kinetic isotope effects and a positive correlation of second-order rate constants (k2) compared to rate constants for p-X-DTBPs plus cumylperoxyl radical reactions indicate a mechanism that involves rate-limiting hydrogen atom transfer (HAT). A weak correlation of (kBT/e) ln k2 versus Eox of p-X-DTBP indicates that the HAT reactions proceed via a partial transfer of charge rather than a complete transfer of charge in the electron transfer/proton transfer pathway. Product analyses, 18O-labeling experiments, and separate reactivity employing the 2,4,6-tri-tert-butylphenoxyl radical provide further mechanistic insights. After initial HAT, a second molar equiv of 2 couples to the phenoxyl radical initially formed, giving a CuII–OO–(ArO′) intermediate, which proceeds in the case of p-OR-DTBP substrates via a two-electron oxidation reaction involving hydrolysis steps which liberate H2O2 and the corresponding alcohol. By contrast, four-electron oxygenation (O–O cleavage) mainly occurs for p-R-DTBP which gives 18O-labeled DTBQ and elimination of the R group. PMID:24953129

  5. Preparation and Catalysis of Aminomethylated Polystyrene Supported Unsymmetrical Schiff-Base Metal Complexes for the Oxidation of Cyclohexene

    X.L.Shi; Y.Chang; F.Zha; Y.G.Wang


    1 Results The dominant position of molecular oxygen as the oxidant for bulk chemical oxyfunctionalizations is due to the fact that it is the only economically and environmentally friendly feasible oxidant for large scale processing.But molecular oxygen is not better oxidant than others,such as PhIO,NaOCl,H2O2,alkyl hydroperoxides,percarboxylic acids,magnesium monoperoxyphthalate.So we have to select high reactivity and general utility catalyst.The oxidation of hydrocarbons catalyzed by transition metal ...

  6. Magnetic and structural properties of La{sub 1-x}Th{sub x}CrO{sub 3} and LaCr{sub 1-y}Ti{sub y}O{sub 3}

    Reuvekamp, P.; Kremer, R.K. [Max Planck Institut fuer Festkoerperforschung, (Germany); Razavi, F.S. [Department of Physics, Brock University, St. Catharines, Ontario (Canada)


    The magnetic properties of ceramic samples of La{sub 1-x}Th{sub x}CrO{sub 3} and LaCr{sub 1-y}Ti{sub y}O{sub 3} were investigated. In order to improve the chemical homogeneity and stoichiometry, the ceramic samples were prepared by the citrate-pyrolysis synthesis route. X-ray investigations of these samples revealed that all the phases maintained their orthorhombic structure, however with different mass densities. The substitution of Th for La does not have effect on the magnetic properties of LaCrO{sub 3} with the Neel temperature remaining close to 290 K whereas, replacing Ti for Cr reduces the Neel temperature to a minimum of 237 K for y=0.2.


    Barajas Ledesma, Edgar


    Los resultados de la síntesis y caracterización de películas de TiO2 (titania) y TiO2-Al2O3 (titania –alúmina) obtenidas mediante pulverización catódica (sputtering) y deposición electroforética, son presentados en el presente trabajo. En el sistema mixto se emplearon dos composiciones de alúmina: 10 y 20 % mol, respectivamente. Por lo tanto, se tuvieron tres sistemas: sistema T (100% titania), sistema A1 (10% alúmina) y sistema A2 (20 % alúmina). Las películas fueron deposi...

  8. Analysis of Ba{sub x}Sr{sub y}TiO{sub 3} perovskite layers. II. Development of analytical method for the determination of the stoichiometry and trace impurities by ICP-MS

    Boulyga, S.F. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen]|[Radiation Physics and Chemistry Problems Inst., Minsk (Belarus); Becker, J.S. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen


    Determination of stoichiometry in semiconducting and non-conducting thin layers is of importance for the study of growth mechanisms and for the control of defects during their development and production. An analytical procedure for inductively coupled plasma mass spectrometry (ICP-MS) was developed using different ICP-MS instruments [one double-focusing sector field ICP-MS (DF-ICP-MS) and two quadrupole ICP-MS without and with hexapole collision cell (ICP-QMS and HEX-ICP-QMS, respectively)] for the determination of stoichiometry and trace impurities in thin Ba{sub x}Sr{sub y}TiO{sub 3} (BST) perovskite layers on silicon substrates after dissolution of layer. Maximum sensitivity, lowest detection limits and best precision was achieved in DF-ICP-MS. ICP-QMS with hexapole collision cell yielded better sensitivity and lower limits of detection in comparison to conventional quadrupole ICP-MS. (orig.)

  9. Observation of a dodecagonal oxide quasicrystal and its complex approximant in the SrTiO3-Pt(1 1 1) system

    Schenk, Sebastian; Förster, Stefan; Meinel, Klaus; Hammer, René; Leibundgut, Bettina; Paleschke, Maximilian; Pantzer, Jonas; Dresler, Christoph; Schumann, Florian O.; Widdra, Wolf


    We report on the formation of a SrTiO3-derived dodecagonal oxide quasicrystal (OQC) at the interface to Pt(1 1 1). This is the second observation of a two-dimensional quasicrystal in the class of oxides. The SrTiO3-derived OQC exhibits strong similarities to the BaTiO3-derived OQC with respect to the local tiling geometry. However, the characteristic length scale of the SrTiO3-derived OQC is 1.8% smaller. Coexisting with the OQC a large scale approximant structure with a monoclinic unit cell is identified. It demonstrates the extraordinary level of complexity that oxide approximant structures can reach.

  10. Effects of Melatonin, Aluminum Oxide, and Polymethylsiloxane Complex on the Expression of LYVE-1 in the Liver of Mice with Obesity and Type 2 Diabetes Mellitus.

    Michurina, S V; Ishchenko, I Yu; Arkhipov, S A; Klimontov, V V; Rachkovskaya, L N; Konenkov, V I; Zavyalov, E L


    The effects of melatonin, aluminum oxide, and polymethylsiloxane complex on the expression of LYVE-1 (lymphatic vessel endothelial hyaluronan receptor) in the liver were studied in db/db mice with experimental obesity and type 2 diabetes mellitus. The complex or placebo was administered daily by gavage from week 8 to week 16 of life. The animals receiving the complex exhibited enhanced, in comparison with the placebo group, immunohistochemical LYVE-1+ staining of endothelial cells in sinusoids. Enhanced expression of LYVE-1 was associated with less pronounced dilatation of interlobular arteries, veins, and lymphatic vessels. Thee findings suggest a protective effect of the complex towards structural changes in the liver of mice with obesity and type 2 diabetes.

  11. Two pathways for electrocatalytic oxidation of hydrogen by a nickel bis(diphosphine) complex with pendant amines in the second coordination sphere.

    Yang, Jenny Y; Smith, Stuart E; Liu, Tianbiao; Dougherty, William G; Hoffert, Wesley A; Kassel, W Scott; Rakowski DuBois, M; DuBois, Daniel L; Bullock, R Morris


    A nickel bis(diphosphine) complex containing pendant amines in the second coordination sphere, [Ni(P(Cy)2N(t-Bu)2)2](BF4)2 (P(Cy)2N(t-Bu)2 = 1,5-di(tert-butyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to the Ni(II) complex gives three isomers of the doubly protonated Ni(0) complex [Ni(P(Cy)2N(t-Bu)2H)2](BF4)2. Using the pKa values and Ni(II/I) and Ni(I/0) redox potentials in a thermochemical cycle, the free energy of hydrogen addition to [Ni(P(Cy)2N(t-Bu)2)2](2+) was determined to be -7.9 kcal mol(-1). The catalytic rate observed in dry acetonitrile for the oxidation of H2 depends on base size, with larger bases (NEt3, t-BuNH2) resulting in much slower catalysis than n-BuNH2. The addition of water accelerates the rate of catalysis by facilitating deprotonation of the hydrogen addition product before oxidation, especially for the larger bases NEt3 and t-BuNH2. This catalytic pathway, where deprotonation occurs prior to oxidation, leads to an overpotential that is 0.38 V lower compared to the pathway where oxidation precedes proton movement. Under the optimal conditions of 1.0 atm H2 using n-BuNH2 as a base and with added water, a turnover frequency of 58 s(-1) is observed at 23 °C.

  12. Self-propagating high-temperature synthesis of LaMO{sub 3} perovskite-type oxide using heteronuclearcyano metal complex precursors

    Sánchez-Rodríguez, Daniel, E-mail: [GRMT, Department of Physics, University of Girona, Campus Montilivi, Edif.PII, E17071 Girona, Catalonia (Spain); Wada, Hiroki; Yamaguchi, Syuhei [Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Farjas, Jordi [GRMT, Department of Physics, University of Girona, Campus Montilivi, Edif.PII, E17071 Girona, Catalonia (Spain); Yahiro, Hidenori, E-mail: [Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan)


    The decomposition of La[Fe(CN){sub 6}]·5H{sub 2}O and La[Co(CN){sub 6}]·5H{sub 2}O under different atmospheres has been analyzed by thermogravimetry (TG) and differential thermal analysis (DTA). In addition, the decomposition temperature at different sample locations was monitored for sample masses around 2 g of La[Fe(CN){sub 6}]·5H{sub 2}O and La[Co(CN){sub 6}]·5H{sub 2}O, when they were calcined for 1 h at temperatures ranging from 200 to 400 °C in a controlled gas-flow system. Results showed that, the large enough of the cyano complex precursors undergo combustion when they are decomposed under oxygen atmosphere. X-ray diffraction results revealed that perovskite-type oxides crystallize due to the overheating of the process. As a result, it has been possible to produce LaFeO{sub 3} and LaCoO{sub 3} perovskite-type oxide powders by SHS under oxygen atmosphere using La[Fe(CN){sub 6}]·5H{sub 2}O and La[Co(CN){sub 6}]·5H{sub 2}O as a precursor. The effect of the ignition temperature has been investigated. The specific surface area of the perovskite-type oxides produced via SHS using heteronuclearcyano metal complex as a precursor is significantly higher than that of other LaMO{sub 3} produced using the same technique but obtained from other type of precursors. - Highlights: • The decomposition of La[Fe(CN){sub 6}] and La[Co(CN){sub 6}] precursors was analyzed. • The combustion process proceeded under oxygen when sample was large enough. • Perovskite oxides via SHS from the cyano complex precursors were synthesized. • LaMO{sub 3} perovskite oxides via SHS was obtained with high specific surface area.

  13. Poly(N-4-vinylbenzyl-1,4,7-triazacyclononane Copper Complex Grafted Solid Catalyst for Oxidative Polymerization of 2,6-Dimethylphenol

    Kei Saito


    Full Text Available A new solid phase catalyst, poly(N-4-vinylbenzyl-1,4,7-triazacyclononane copper(I complex, grafted onto polystyrene particles, has been employed for the oxidative polymerization of 2,6-dimethylphenol using an aqueous biphasic (water/toluene solvent system. The solid catalyst was synthesized by first grafting N-(4-vinylbenzyl-1,4,7-triaza-cyclononane onto polystyrene particles using a radical mediated polymerization method and next by creating the polymer-metal complex of copper-triazacyclononane with these modified particles. Poly(2,6-dimethyl-1,4-phenylene oxide was successfully obtained from the polymerization of 2,6-dimethylphenol using this new metal-organic solid phase catalyst.

  14. Synthesis of TiO2 Nanoparticles via a Ti(Ⅳ) Complex with Stearic Acid and the Photocatalytic Activity for Organic Oxidation

    XU,Yi-Ming(许宜铭); YU,Xiao-Han(于小涵); LIU,Hui-Jun(刘惠君)


    The nano-sized particles of TiO2 were prepared by thermal decomposition of titanium(Ⅳ) tetrabutanoxide complex with stearic acid at 450 ℃ in the air. It was observed that the amount of stearic acid, used initially for the complex synthesis in 2-propanol at 25 ℃, had great influence on the physical properties of the prepared TiO2 including crystal structure,the particle size, surface area and the adsorption capacity for organic substrate of a textile dye X3B in water, and thereafter the photocatalytic activity for the dye oxidation. Some samples displayed lower adsorption capacity for the organic substrate in water than a TiO2 of Degussa p25, but higher photocatalytic activity for the organic oxidation. Possible reason for the observed difference was discussed in the text.

  15. A complex of antioxidant vitamins effectively inhibits free-radical oxidation of LDL phospholipids in blood plasma and membrane structures of the liver and myocardium.

    Konovalova, G G; Lisina, M O; Tikhaze, A K; Lankin, V Z


    Antioxidant effect of a complex preparation including antioxidant vitamins C, E, provitamin A and selenium was studied on the model of Cu(2+)-initiated free-radical oxidation of LDL isolated from human blood plasma. The antioxidant effect of combined administration of alpha-tocopherol+ascorbic acid and alpha-tocopherol+beta-carotene is far more pronounced that the antioxidant effect of individual components of these cocktails. Moreover, in the model system the combined action of all antioxidant components completely inhibited free-radical oxidation of LDL. A 30-day course of peroral administration of antioxidant vitamin cocktail and selenium to rats pronouncedly enhanced the antioxidant potential of liver and completely suppressed free-radical processes in the myocardium. It is suggested that preparations containing antioxidant vitamins and selenium can be perspective for prevention and complex therapy of atherosclerosis.

  16. Poly(N-4-vinylbenzyl-1,4,7-triazacyclononane) Copper Complex Grafted Solid Catalyst for Oxidative Polymerization of 2,6-Dimethylphenol.

    Saito, Kei; Miyamoto, Koji; Nanayakkara, Sepa; Ihara, Hirotaka; Hearn, Milton T W


    A new solid phase catalyst, poly(N-4-vinylbenzyl-1,4,7-triazacyclononane) copper(I) complex, grafted onto polystyrene particles, has been employed for the oxidative polymerization of 2,6-dimethylphenol using an aqueous biphasic (water/toluene) solvent system. The solid catalyst was synthesized by first grafting N-(4-vinylbenzyl)-1,4,7-triaza-cyclononane onto polystyrene particles using a radical mediated polymerization method and next by creating the polymer-metal complex of copper-triazacyclononane with these modified particles. Poly(2,6-dimethyl-1,4-phenylene oxide) was successfully obtained from the polymerization of 2,6-dimethylphenol using this new metal-organic solid phase catalyst.

  17. A manganese(V)-oxo π-cation radical complex: influence of one-electron oxidation on oxygen-atom transfer.

    Prokop, Katharine A; Neu, Heather M; de Visser, Sam P; Goldberg, David P


    One-electron oxidation of Mn(V)-oxo corrolazine 2 affords 2(+), the first example of a Mn(V)(O) π-cation radical porphyrinoid complex, which was characterized by UV-vis, EPR, LDI-MS, and DFT methods. Access to 2 and 2(+) allowed for a direct comparison of their reactivities in oxygen-atom transfer (OAT) reactions. Both complexes are capable of OAT to PPh(3) and RSR substrates, and 2(+) was found to be a more potent oxidant than 2. Analysis of rate constants and activation parameters, together with DFT calculations, points to a concerted OAT mechanism for 2(+) and 2 and indicates that the greater electrophilicity of 2(+) likely plays a dominant role in enhancing its reactivity. These results are relevant to comparisons between Compound I and Compound II in heme enzymes.

  18. Photocatalytic oxidation of TMB with the double stranded DNA-SYBR Green I complex for label-free and universal colorimetric bioassay.

    Zhang, Xinfeng; Huang, Chengpeng; Xu, Shuxia; Chen, Junbo; Zeng, Ying; Wu, Peng; Hou, Xiandeng


    We report here the newly discovered photocatalytic activity of the dsDNA-SYBR Green I (SG) complex, which can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) under light irradiation corresponding to the excitation of the dsDNA-SG complex. The most appealing feature of the photocatalytic system here is that it can be obtained using random DNA sequences that can form a duplex. Considering the universality of the photooxidase, a label-free and universal platform was proposed for highly sensitive visual bioassays.

  19. DNA-binding, catalytic oxidation, C—C coupling reactions and antibacterial activities of binuclear Ru(II thiosemicarbazone complexes: Synthesis and spectral characterization

    Arumugam Manimaran


    Full Text Available New hexa-coordinated binuclear Ru(II thiosemicarbazone complexes of the type {[(B(EPh3(COClRu]2L} (where, E = P or As; B = PPh3 or AsPh3 or pyridine; L = mononucleating NS donor of N-substituted thiosemicarbazones have been synthesized and characterized by elemental analysis, FT-IR, UV–vis and 31P{1H} NMR cyclic voltammetric studies. The DNA-binding studies of Ru(II complexes with calf thymus DNA (CT-DNA were investigated by UV–vis, viscosity measurements, gel-electrophoresis and fluorescence spectroscopy. The new complexes have been used as catalysts in C—C coupling reaction and in the oxidation of alcohols to their corresponding carbonyl compounds by using NMO as co-oxidant and molecular oxygen (O2 atmosphere at ambient temperature. Further, the new binucleating thiosemicarbazone ligands and their Ru(II complexes were also screened for their antibacterial activity against Klebsiella pneumoniae, Shigella sp., Micrococcus luteus, Escherichia coli and Salmonella typhi. From this study, it was found out that the activity of the complexes almost reaches the effectiveness of the conventional bacteriocide.

  20. Porphyrazines with oligo(ethylene oxide) thio alkoxy chains: Synthesis, aggregation, photophysics, and complexation with redox-active ions

    Piet, D.P.; Veldhuis, H.; Zuilhof, H.; Sudhölter, E.J.R.


    A series of new porphyrazines with oligo(ethylene oxide) thioalkoxy side chains has been synthesized. Study of the phase transitions reveals the absence of liquid crystallinity. Due to the ethylene oxide moieties, the solubility in a variety of solvents is dramatically increased. This allowed the

  1. An efficient optical-electrochemical dual probe for highly sensitive recognition of dopamine based on terbium complex functionalized reduced graphene oxide

    Zhou, Zhan; Wang, Qianming


    A novel organic-inorganic hybrid sensor based on diethylenetriaminepentaacetic acid (DTPA) modified reduced graphene oxide (RGO-DTPA) chelated with terbium ions allows detection of dopamine (DA) through an emission enhancement effect. Its luminescence, peaking at 545 nm, has been improved by a factor of 25 in the presence of DA (detection limit = 80 nM). In addition, this covalently bonded terbium complex functionalized reduced graphene oxide (RGO-DTPA-Tb) can be successfully assembled on a glassy carbon electrode. The assay performed through differential pulse voltammetry (DPV) yielded obvious peak separation between DA and excessive amounts of the interfering ascorbic acid (AA).A novel organic-inorganic hybrid sensor based on diethylenetriaminepentaacetic acid (DTPA) modified reduced graphene oxide (RGO-DTPA) chelated with terbium ions allows detection of dopamine (DA) through an emission enhancement effect. Its luminescence, peaking at 545 nm, has been improved by a factor of 25 in the presence of DA (detection limit = 80 nM). In addition, this covalently bonded terbium complex functionalized reduced graphene oxide (RGO-DTPA-Tb) can be successfully assembled on a glassy carbon electrode. The assay performed through differential pulse voltammetry (DPV) yielded obvious peak separation between DA and excessive amounts of the interfering ascorbic acid (AA). Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06156f

  2. Density functional theory studies on the oxidation of 5'-dGMP and 5'-dAMP by a platinum(IV) complex.

    Ariafard, Alireza; Tabatabaie, Elham S; Aghmasheh, Simin; Najaflo, Sahar; Yates, Brian F


    Density functional theory has been used to investigate the oxidation of a guanine nucleotide by platinum(IV), a process that can be important in the degradation of DNA. For the first time, we have provided a comprehensive mechanism for all of the steps in this process. A number of intermediates are predicted to occur but with short lifetimes that would make them difficult to observe experimentally. A key step in the mechanism is electron transfer from guanine to platinum(IV), and we show that this is driven by the loss of a chloride ligand from the platinum complex after nucleophilic attack of 5'-phosphate to C8 of guanine. We have investigated several different initial platinum(IV) guanine adducts and shown that the adduct formed from replacement of an axial chlorine ligand in the platinum(IV) complex undergoes oxidation more easily. We have studied adenine versus guanine adducts, and our results show that oxidation of the former is more difficult because of disruption of the aromatic π system that occurs during the process. Finally, our results show that the acidic hydrolysis step to form the final oxidized product occurs readily via an initial protonation of N7 of the guanine.

  3. Inorganic and organic structures as interleavers among [bis(1-methyl-3-(p-carboxylatephenyl)triazenide 1-oxide)Ni(II)] complexes to form supramolecular arrangements

    Santos, Aline Joana Rolina Wohlmuth Alves; dos Santos Hackbart, Helen Cristina; Giacomini, Gabriela Xavier; Bersch, Patrícia; Paraginski, Gustavo Luiz; Hörner, Manfredo


    Alternative compounds to capture metal ions are triazenes 1-oxide since they are basic compounds O(N) with negative charge in the deprotonated form. The proximity of both coordination sites (O and N) enables these compounds to have good chelating ability and a tendency to stabilize in the formation of rings with soft and hard transition metal ions. The structure analysis by single crystal X-ray diffraction of compounds (1) and (2) demonstrate the formation of 3D supramolecular arrangements through ion-ion, ion-dipolo and dipolo-dipolo interactions. In one of them, there are [(H2O)2(CH3CH3SO)K2]2+ as linkers of polymerization and, in another complex, there are [(H2O)(CH3CH3SO)Ni(H2O)6]2+ as a linker of polymerization. These linkers act in the polymerization of the novel mononuclear complex [bis(1-methyl (p-carboxylatephenyl) triazenide 1-oxide) NiII] (3). The crystallography analysis of (1) and (2) showed distorted quadratic geometry for Ni (II), thus, there are two axial positions available in Ni (II) to be used in catalysis studies and as sensor or biosensor. In addition, this study shows the support of this novel mononuclear complex of Ni (II) (3) on protonated chitosan chains (4). The compounds (3) and (4) were characterized by spectroscopic analysis, infrared (IR) and energy dispersive X-ray detector (EDS), and by differential scanning calorimetry analysis (DSC). The specificity of ligand 1-methyl (p-carboxyphenyl) triazene 1-oxide to capture potassium and nickel ions will be tested at different pH values, as well as the capacity of the triazenide 1-oxide of Ni (II) complex, supported on chitosan polymer, or not, to act as a catalyst for organic reactions and biomimetic organic reactions.

  4. Dynamic etching of soluble surface layers with on-line inductively coupled plasma mass spectrometry detection - a novel approach for determination of complex metal oxide surface cation stoichiometry

    Limbeck, A; Rupp, GM; M. Kubicek; Tellez, H.; Druce, J; Ishihara, T.; Kilner, JA; Fleig, J.


    In this work, an innovative approach for determining the surface stoichiometry of complex metal oxide (CMO) thin films is presented. The procedure is based on treatment of the sample surface with different etching solutions, followed by on-line analysis of the derived eluates using inductively coupled plasma ? mass spectrometry (ICP-MS). Via consecutive treatment of the sample surface with water and diluted HCl, a differentiation between water soluble and acid soluble parts of near surface re...

  5. Dual function photocatalysis of cyano-bridged heteronuclear metal complexes for water oxidation and two-electron reduction of dioxygen to produce hydrogen peroxide as a solar fuel.

    Aratani, Yusuke; Suenobu, Tomoyoshi; Ohkubo, Kei; Yamada, Yusuke; Fukuzumi, Shunichi


    The photocatalytic production of hydrogen peroxide from water and dioxygen under visible light irradiation was made possible by using polymeric cyano-bridged heteronuclear metal complexes (M(II)[Ru(II)(CN)4(bpy)]; M(II) = Ni(II), Fe(II) and Mn(II)), where the photocatalytic two-electron reduction of O2 and water oxidation were catalysed by the Ru and M(II) moieties, respectively.

  6. Ergothioneine prevents copper-induced oxidative damage to DNA and protein by forming a redox-inactive ergothioneine-copper complex.

    Zhu, Ben-Zhan; Mao, Li; Fan, Rui-Mei; Zhu, Jun-Ge; Zhang, Ying-Nan; Wang, Jing; Kalyanaraman, Balaraman; Frei, Balz


    Ergothioneine (2-mercaptohistidine trimethylbetaine) is a naturally occurring amino acid analogue found in up to millimolar concentrations in several tissues and biological fluids. However, the biological functions of ergothioneine remain incompletely understood. In this study, we investigated the role of ergothioneine in copper-induced oxidative damage to DNA and protein, using two copper-containing systems: Cu(II) with ascorbate and Cu(II) with H(2)O(2) [0.1 mM Cu(II), 1 mM ascorbate, and 1 mM H(2)O(2)]. Oxidative damage to DNA and bovine serum albumin was measured as strand breakage and protein carbonyl formation, respectively. Ergothioneine (0.1-1.0 mM) provided strong, dose-dependent protection against oxidation of DNA and protein in both copper-containing systems. In contrast, only limited protection was observed with the purported hydroxyl radical scavengers, dimethyl sulfoxide and mannitol, even at concentrations as high as 100 mM. Ergothioneine also significantly inhibited copper-catalyzed oxidation of ascorbate and competed effectively with histidine and 1,10-phenanthroline for binding of cuprous copper, but not cupric copper, as demonstrated by UV-visible and low-temperature electron spin resonance techniques. We conclude that ergothioneine is a potent, natural sulfur-containing antioxidant that prevents copper-dependent oxidative damage to biological macromolecules by forming a redox-inactive ergothioneine-copper complex.

  7. A general method for preparing lanthanide oxide nanoparticles via thermal decomposition of lanthanide(III) complexes with 1-hydroxy-2-naphthoic acid and hydrazine ligands

    Parimalagandhi, Karuppannan; Premkumar, Thathan; Vairam, Sundararajan


    Six new lanthanide(III) complexes (i.e., [Ln(L)2(NA)1.5]·3H2O, where Ln=La(III), Pr(III), Nd(III), Sm(III), Gd(III), and Ce(III) and L and NA indicate N2H4 and C10H6(1-O)(2-COO), respectively) with 1-hydroxy-2-naphthoic acid [C10H6(1-O)(2-COOH)] and hydrazine (N2H4) as co-ligands were characterized by elemental, FTIR, UV-visible, and XRD techniques. In the FT-IR spectra, the N-N stretching frequency in the range of 981-949 cm-1 demonstrates evidence of the presence of coordinated N2H4, indicating the bidentate bridging nature of hydrazine in the complexes. These complexes show symmetric and asymmetric COO- stretching from 1444 to 1441 cm-1 and 1582 to 1557 cm-1, respectively, indicating bidentate coordination. TG-DTA studies revealed that the compounds underwent endothermic dehydration from 98 to 110 °C. This was followed by the exothermic decomposition of oxalate intermediates to yield the respective metal oxides as the end products. From SEM images, the average size of the metal oxide particles prepared by thermal decomposition of the complexes was determined to be 39-42 nm. The powder X-ray and SEM coupled with energy dispersive X-ray (EDX) studies revealed the presence of the respective nano-sized metal oxides. The kinetic parameters of the decomposition of the complexes were calculated using the Coats-Redfern equation.

  8. Characterization of the mechanisms of action and nitric oxide species involved in the relaxation induced by the ruthenium complex.

    Bonaventura, Daniella; Oliveira, Fabiana S; Lunardi, Claure N; Vercesi, Juliana A; da Silva, Roberto S; Bendhack, Lusiane M


    Nitric oxide (NO) plays an important role in the control of vascular tone. NO donors have therapeutic use and the most used NO donors, nitroglycerin and sodium nitroprusside have problems in their use. Thus, new NO donors have been synthesized to minimize these undesirable effects. Nytrosil ruthenium complexes have been studied as a new class of NO donors. trans-[RuCl([15]aneN(4))NO](2+), induces vasorelaxation only in presence of reducing agent. In this study, we characterized the mechanisms of vasorelaxation of trans-[RuCl([15]aneN(4))NO](2+) in denuded rat aorta and identified which NO forms are involved in this relaxation. We also evaluated the effect of this NO donor in decreasing the cytosolic Ca(2+) concentration ([Ca(2+)]c) of the vascular smooth muscle cells. Vasorelaxation to trans-[RuCl([15]aneN(4))NO](2+) (E(max): 101.8 +/- 2.3%, pEC(50): 5.03 +/- 0.15) was almost abolished in the presence of the NO* scavenger hydroxocobalamin (E(max): 4.0 +/- 0.4%; P < 0.001) and it was partially inhibited by the NO(-) scavenger L-cysteine (E(max): 79.9 +/- 6.9%, pEC(50): 4.41 +/- 0.06; P < 0.05). The guanylyl cyclase inhibitor ODQ reduced the E(max) (57.7 +/- 4.0%, P < 0.001) and pEC(50) (4.21 +/- 0.42, P < 0.01) and the combination of ODQ and TEA abolished the response to trans-[RuCl([15]aneN(4))NO](2+). The blockade of voltage-dependent (K(v)), ATP-sensitive (K(ATP)), and Ca(2+)-activated (K(Ca) K(+) channels reduced the vasorelaxation induced by trans-[RuCl([15]aneN(4))NO](2+). This compound significantly reduced [Ca(2+)]c (from 100% to 85.9 +/- 3.5%, n = 4). In conclusion, our data demonstrate that this NO donor induces vascular relaxation involving NO* and NO(-) species, that is associated to a decrease in [Ca(2+)]c. The mechanisms of vasorelaxation involve guanylyl cyclase activation, cGMP production and K(+) channels activation.

  9. Synthesis, structural characterization, and benzyl alcohol oxidation activity of mononuclear manganese(II) complex with 2,2'-bipyridine: [Mn(bipy)2(ClO4)2

    KANİ, İbrahim; KURTÇA, Mehmet


    A manganese(II) complex of 2,2'-bipyridine (bipy) was synthesized and characterized by X-ray diffraction, IR, and UV-vis spectroscopy. The activity of the complex was tested for oxidation of benzyl alcohols using t-BuOOH as an oxidant in organic solvents and in an organic/water biphasic system (hexane/H2O, toluene/H2O). The effect of solvent, temperature, oxidant, and some additives (KBr, N(C4H9)Br, and N-bromosuccinimide) on the oxidation of benzyl alcohol is reported. The res...

  10. Innovative Powder Processing of Oxide Dispersion Strengthened ODS Ferritic Stainless Steels

    Rieken, Joel; Anderson, Iver; Kramer, Matthew


    An innovative gas atomization reaction synthesis technique was employed as a viable method to dramatically lower the processing cost for precursor oxide dispersion forming ferritic stainless steel powders (i.e., Fe-Cr-(Hf,Ti)-Y). During this rapid solidification process the atomized powders were enveloped by a nano-metric Cr-enriched metastable oxide film. Elevated temperature heat treatment was used to dissociate this metastable oxide phase through oxygen exchange reactions with Y-(Hf,Ti) enriched intermetallic compound precipitates. These solid state reactions resulted in the formation of highly stable nano-metric mixed oxide dispersoids (i.e., Y-Ti-O or Y-Hf-O) throughout the alloy microstructure. Subsequent high temperature (1200 C) heat treatments were used to elucidate the thermal stability of each nano-metric oxide dispersoid phase. Transmission electron microscopy coupled with X-ray diffraction was used to evaluate phase evolution within the alloy microstructure.

  11. Bimetallic Oxidation Catalysts. Oxygen Insertion into an Aryl–Hydrogen Bond of a Binuclear Copper(I) Complex

    Gelling, O.J.; Bolhuis, F. van; Meetsma, A.; Feringa, Bernard


    The binuclear copper(I) complex of 1,3-bis[N-(2-pyridylethyl)formimidoyl]benzene reacts with molecular oxygen to give a phenoxy- and hydroxy-bridged binuclear copper(II) complex; the structures of both complexes have been determined by X-ray crystallography.

  12. Formation of a ruthenium(IV)-oxo complex by electron-transfer oxidation of a coordinatively saturated ruthenium(II) complex and detection of oxygen-rebound intermediates in C-H bond oxygenation.

    Kojima, Takahiko; Nakayama, Kazuya; Ikemura, Kenichiro; Ogura, Takashi; Fukuzumi, Shunichi


    A coordinatively saturated ruthenium(II) complex having tetradentate tris(2-pyridylmethyl)amine (TPA) and bidentate 2,2'-bipyridine (bpy), [Ru(TPA)(bpy)](2+) (1), was oxidized by a Ce(IV) ion in H(2)O to afford a Ru(IV)-oxo complex, [Ru(O)(H(+)TPA)(bpy)](3+) (2). The crystal structure of the Ru(IV)-oxo complex 2 was determined by X-ray crystallography. In 2, the TPA ligand partially dissociates to be in a facial tridentate fashion and the uncoordinated pyridine moiety is protonated. The spin state of 2, which showed paramagnetically shifted NMR signals in the range of 60 to -20 ppm, was determined to be an intermediate spin (S = 1) by the Evans' method with (1)H NMR spectroscopy in acetone-d(6). The reaction of 2 with various oraganic substrates in acetonitrile at room temperature afforded oxidized and oxygenated products and a solvent-bound complex, [Ru(H(+)TPA)(bpy)(CH(3)CN)], which is intact in the presence of alcohols. The oxygenation reaction of saturated C-H bonds with 2 proceeds by two-step processes: the hydrogen abstraction with 2, followed by the dissociation of the alcohol products from the oxygen-rebound complexes, Ru(III)-alkoxo complexes, which were successfully detected by ESI-MS spectrometry. The kinetic isotope effects in the first step for the reaction of dihydroanthrathene (DHA) and cumene with 2 were determined to be 49 and 12, respectively. The second-order rate constants of C-H oxygenation in the first step exhibited a linear correlation with bond dissociation energies of the C-H bond cleavage.

  13. In-Situ ATR-FTIR and Surface Complexation Modeling Study of the Adsorption of Dimethylarsenic Acid and p-Arsanilic Acid on Iron Oxides

    Goldberg, S. R.; Al-Abadleh, H.; Mitchell, W.


    Arsenic is an element that exists naturally in many rocks and minerals around the world, accumulates in petroleum, shale, and coal deposits as a result of biogeochemical processes, and is found in fly ash from fuel combustion. Arsenic compounds in their organic and inorganic forms pose both health and environmental risks. The environmental fate of arsenic compounds is controlled to a large extent by their surface interactions with inorganic and organic surfaces. We report results from applying the triple layer surface complexation model to adsorption isotherm and pH-envelope experimental data of dimethylarsenic acid, DMA, and p-arsanilic acid, p-AsA on the iron oxides, hematite and goethite. Ligand exchange reactions were based on the interpretation of ATR-FTIR spectra of DMA and p-AsA surface complexes. Surface coverage of the organoarsenicals was quantified in-situ from the spectral component at 840 cm-1. The best model fit to the DMA adsorption data was obtained using an outer-sphere complex, whereas for p-AsA, best model fit was obtained using two monodentate inner-sphere surface complexes. The significance of the results is discussed in relation to improving modeling tools used by environmental regulators. Accurate predictive modeling tools are needed for effective design of arsenic removal technologies using iron oxide minerals.

  14. In-situ synthesis and luminescence properties of titanium oxide gels containing 1,10-phenanthroline europium(Ⅲ) complex

    XIE Fei; YANG Hui; XU Cun-jin; ZHANG Xi-he


    It is difficult to directly dope europium complexes in gel because the excessive water or high acidic condition may lead to their decomposition. We prepared a novel homogeneous TiO2 gel containing Eu-phen complexes by using an in-situ synthesis method. The formation of Eu-phen complexes in sol-gel derived TiO2 was confirmed by luminescence excitation spectra. The effects of temperature and aging time on in-situ synthesis are discussed. The luminescence spectra of gel containing europium complexes were also compared with the pure Eu-phen complexes.

  15. Gas-phase doubly charged complexes of cyclic peptides with copper in +1, +2 and +3 formal oxidation states: formation, structures and electron capture dissociation.

    Afonso, Carlos; Tabet, Jean-Claude; Giorgi, Gianluca; Tureček, František


    Copper complexes with a cyclic D-His-β-Ala-L-His-L-Lys and all-L-His-β-Ala-His-Lys peptides were generated by electrospray which were doubly charged ions that had different formal oxidation states of Cu(I), Cu(II) and Cu(III) and different protonation states of the peptide ligands. Electron capture dissociation showed no substantial differences between the D-His and L-His complexes. All complexes underwent peptide cross-ring cleavages upon electron capture. The modes of ring cleavage depended on the formal oxidation state of the Cu ion and peptide protonation. Density functional theory (DFT) calculations, using the B3LYP with an effective core potential at Cu and M06-2X functionals, identified several precursor ion structures in which the Cu ion was threecoordinated to pentacoordinated by the His and Lys side-chain groups and the peptide amide or enolimine groups. The electronic structure of the formally Cu(III) complexes pointed to an effective Cu(I) oxidation state with the other charge residing in the peptide ligand. The relative energies of isomeric complexes of the [Cu(c-HAHK + H)](2+) and [Cu(c-HAHK - H)](2+) type with closed electronic shells followed similar orders when treated by the B3LYP and M06-2X functionals. Large differences between relative energies calculated by these methods were obtained for open-shell complexes of the [Cu(c-HAHK)](2+) type. Charge reduction resulted in lowering the coordination numbers for some Cu complexes that depended on the singlet or triplet spin state being formed. For [Cu(c-HAHK - H)](2+) complexes, solution H/D exchange involved only the N-H protons, resulting in the exchange of up to seven protons, as established by ultra-high mass resolution measurements. Contrasting the experiments, DFT calculations found the lowest energy structures for the gas-phase ions that were deprotonated at the peptide C(α) positions.

  16. Rearrangement of a (dithiolato)platinum(II) complex formed by reaction of cyclic disulfide 7,8-dithiabicyclo[4.2.1]nona-2,4-diene with a platinum(0) complex: Oxidation of the rearranged (dithiolato)platinum(II) complex

    石井, 昭彦


    Reaction of the title bicyclic disulfide 16 with [(Ph3P)(2)Pt(eta(2)-C2H4)] (2) yielded the corresponding (dithiolato)platinum(II) complex 17 by oxidative addition. The initial product 17 isomerized at room temperature in a [1,5]-sulfur rearrangement to give another (dithiolato)platinum(II) complex 18 in high isolated yield. Oxidation reactions of 18 with dimethyldioxirane (DMD) provided (sulfenato-thiolato)platinum(II) 23, (sulfinato-thiolato)platinum(II) 24, (sulfenato-sulfinato)platinum(II...

  17. Reduction of brain mitochondrial β-oxidation impairs complex I and V in chronic alcohol intake: the underlying mechanism for neurodegeneration.

    James Haorah

    Full Text Available Neuropathy and neurocognitive deficits are common among chronic alcohol users, which are believed to be associated with mitochondrial dysfunction in the brain. The specific type of brain mitochondrial respiratory chain complexes (mRCC that are adversely affected by alcohol abuse has not been studied. Thus, we examined the alterations of mRCC in freshly isolated mitochondria from mice brain that were pair-fed the ethanol (4% v/v and control liquid diets for 7-8 weeks. We observed that alcohol intake severely reduced the levels of complex I and V. A reduction in complex I was associated with a decrease in carnitine palmitoyltransferase 1 (cPT1 and cPT2 levels. The mitochondrial outer (cPT1 and inner (cPT2 membrane transporter enzymes are specialized in acylation of fatty acid from outer to inner membrane of mitochondria for ATP production. Thus, our results showed that alterations of cPT1 and cPT2 paralleled a decrease β-oxidation of palmitate and ATP production, suggesting that impairment of substrate entry step (complex I function can cause a negative impact on ATP production (complex V function. Disruption of cPT1/cPT2 was accompanied by an increase in cytochrome C leakage, while reduction of complex I and V paralleled a decrease in depolarization of mitochondrial membrane potential (ΔΨ, monitored by JC-1 fluorescence and ATP production in alcohol intake. We noted that acetyl-L-carnitine (ALC, a cofactor of cPT1 and cPT2 prevented the adverse effects of alcohol while coenzyme Q10 (CoQ10 was not very effective against alcohol insults. These results suggest that understanding the molecular, biochemical, and signaling mechanisms of the CNS mitochondrial β-oxidation such as ALC can mitigate alcohol related neurological disorders.

  18. PCN pincer palladium(II) complex catalyzed enantioselective hydrophosphination of enones: synthesis of pyridine-functionalized chiral phosphine oxides as NC(sp(3))O pincer preligands.

    Hao, Xin-Qi; Huang, Juan-Juan; Wang, Tao; Lv, Jing; Gong, Jun-Fang; Song, Mao-Ping


    A series of chiral PCN pincer Pd(II) complexes VI-XIII with aryl-based aminophosphine-imidazoline or phosphinite-imidazoline ligands were synthesized and characterized. They were examined as enantioselective catalysts for the hydrophosphination of enones. Among them, complex IX, which features a Ph2PO donor as well as an imidazoline donor with (4S)-phenyl and N-Tol-p groups, was found to be the optimal catalyst. Thus, in the presence of 2-5 mol % of complex IX a wide variety of enones reacted smoothly with diarylphosphines to give the corresponding chiral phosphine derivatives in high yields with enantioselectivities of up to 98% ee. In particular, heteroaryl species such as 2-thienyl-, 2-furyl-, and 2-pyridinyl-containing enones that have a strong coordination ability to the Pd center were also appropriate substrates for the current catalytic system. For example, hydrophosphination of 2-alkenoylpyridines with diphenylphosphine followed by oxidation with H2O2 afforded the corresponding pyridine-functionalized chiral phosphine oxides in good yields with good to excellent enantioselectivities (10 examples, up to 95% ee). Furthermore, it had been demonstrated that the obtained pyridine-containing phosphine oxide acted as a tridentate ligand in the reaction with PdCl2 to form an intriguing NCsp(3)O pincer Pd(II) complex via Csp(3)-H bond activation, which to our knowledge is the first example of a chiral DCsp(3)D' Pd pincer (D ≠ D'; D and D' denote donor atoms such as P, N, etc.).

  19. 铁络合物催化类Fenton氧化研究进展%Progress in the research on iron complex catalyzed Fenton-like oxidation

    郗丽娟; 曹天静; 李大鹏; 杨榕; 徐淑芬; 廖霞; 张瑛洁


    The progress in iron complex catalyzed Fenton-like oxidation is reviewed. Compared with iron,the iron complex has a higher catalytic activity to improve the removal rate of organic matter from water. The homogeneous Fenton-like catalyzed by iron complex may bring a problem of removing metallic ions in subsequent process, so the heterogeneous Fenton-like catalyzed by iron complex has a better future. The current research situation of the Fenton-like catalyzed by iron complex loaded on resin is introduced emphatically and the reactive species in the Fenton-like catalyzed by iron complex is discussed.%综述了铁络合物催化类Fenton氧化的研究进展.铁络合物与铁相比具有更高的催化活性,可提高水中有机物的去除效果.均相类Fenton存在后续金属离子的去除问题,因此铁络合物作为催化剂的多相催化类Fenton氧化具有更好的应用前景.重点介绍了高分子负载铁络合物催化类Fenton氧化降解水中有机物的研究现状及铁络合物催化类Fenton氧化的反应活性物种.

  20. Selective CO{sub 2} reduction conjugated with H{sub 2}O oxidation utilizing semiconductor/metal-complex hybrid photocatalysts

    Morikawa, T., E-mail:; Sato, S., E-mail:; Arai, T., E-mail:; Uemura, K., E-mail:; Yamanaka, K. I., E-mail:; Suzuki, T. M., E-mail:; Kajino, T., E-mail:; Motohiro, T., E-mail: [Toyota Central R and D Labs, Inc., Nagakute, Aichi 480-1192 (Japan)


    We developed a new hybrid photocatalyst for CO{sub 2} reduction, which is composed of a semiconductor and a metal complex. In the hybrid photocatalyst, ΔG between the position of conduction band minimum (E{sub CBM}) of the semiconductor and the CO{sub 2} reduction potential of the complex is an essential factor for realizing fast electron transfer from the conduction band of semiconductor to metal complex leading to high photocatalytic activity. On the basis of this concept, the hybrid photocatalyst InP/Ru-complex, which functions in aqueous media, was developed. The photoreduction of CO{sub 2} to formate using water as an electron donor and a proton source was successfully achieved as a Z-scheme system by functionally conjugating the InP/Ru-complex photocatalyst for CO{sub 2} reduction with a TiO{sub 2} photocatalyst for water oxidation. The conversion efficiency from solar energy to chemical energy was ca. 0.04%, which approaches that for photosynthesis in a plant. Because this system can be applied to many other inorganic semiconductors and metal-complex catalysts, the efficiency and reaction selectivity can be enhanced by optimization of the electron transfer process including the energy-band configurations, conjugation conformations, and catalyst structures. This electrical-bias-free reaction is a huge leap forward for future practical applications of artificial photosynthesis under solar irradiation to produce organic species.

  1. Selective oxidation of benzyl alcohol with tert-butylhydroperoxide catalysed via Mn (II) 2, 2-bipyridine complexes immobilized over the mesoporous hexagonal molecular sieves (HMS)

    Vahid Mahdavi; Mahdieh Mardani


    A series ofMn(II)bipy complexes with different loading of Mn2+ supported on HMS was prepared. These samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Thermogravimetric and Differential Scanning Calorimetry (TG-DSC), Ultraviolet and Visible spectra (UV-Vis) and Fourier transforms Infrared (FT-IR). The catalytic activity of the supportedMn(II)bipy complexes, [Mn(bipy)2]2+/HMS was evaluated in the oxidation of benzyl alcohol in the liquid phase using tert-butylhydroperoxide (TBHP) as an oxidant. The effects of Mn2+ loading and various solvents on the conversion and selectivity were studied. A second order function for the variation in catalytic activity with respect to the loading of Mn2+ ions in different catalyst samples was observed. The activity of the [Mn(bipy)2]2+/HMS catalyst differs with the type of the solvent and in this case, acetonitrile gives the best conversion results. The kinetic of benzyl alcohol oxidation was investigated at temperatures of 27, 46, 60, 75 and 90°C using [Mn(bipy)2]2+/HMS and excess TBHP. The order of reaction with respect to benzyl alcohol was determined to be pseudo-first order. The value of the apparent activation energy was also determined.

  2. Metabolic effects of a novel silicate inositol complex of the nitric oxide precursor arginine in the obese insulin-resistant JCR:LA-cp rat.

    Proctor, Spencer D; Kelly, Sandra E; Vine, Donna F; Russell, James C


    Insulin resistance is a major contributor to macro- and microvascular complications, particularly in the presence of the metabolic syndrome, and is also associated with polycystic ovary syndrome. Impaired nitric oxide metabolism and endothelial function are important components of the vascular disease. Increasing the bioavailability of arginine, the precursor of nitric oxide, thus potentially offers protection against end-stage disease. We have recently demonstrated that dietary supplementation with a novel silicate inositol arginine complex reduces vasculopathy and glomerular sclerosis in the insulin-resistant JCR:LA-cp rat. The objective of this study was to address the absorption of, and the underlying metabolic alterations caused by, the arginine silicate inositol complex and arginine HCl (as a reference agent) in obese insulin-resistant male and female JCR:LA-cp rats. Male and female rats were treated with the preparations at 1.0 mg/(kg d) (expressed as arginine HCl) from 8 to 12 and 12 to 18 weeks of age, respectively. Obese female, but not male, rats treated with the arginine silicate inositol complex showed a reduced rate of weight gain without concomitant reduction in food intake. Plasma silicon levels were raised very significantly in arginine silicate-treated rats, consistent with significant absorption of the complex. In male rats, arginine levels were elevated by treatment with arginine silicate only; and female rats responded to both preparations. Plasma concentrations of oxides of nitrogen in rats treated with the silicate complex showed a dimorphism, decreasing in male and increasing in female rats. Fasting insulin levels were elevated in male rats treated with the arginine silicate complex, whereas fasting and postprandial insulin levels were decreased in female rats. Furthermore, female, but not male, rats treated with either of the arginine preparations showed significant reductions in cholesterol, triglyceride, and phospholipid concentrations

  3. Synthesis, structural studies, kinetic stability, and oxidation catalysis of the late first row transition metal complexes of 4,10-dimethyl-1,4,7,10-tetraazabicyclo[6.5.2]pentadecane.

    Matz, Dallas L; Jones, Donald G; Roewe, Kimberly D; Gorbet, Michael-Joseph; Zhang, Zhan; Chen, Zhuqi; Prior, Timothy J; Archibald, Stephen J; Yin, Guochuan; Hubin, Timothy J


    Synthetic details for 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.5.2]pentadecane, the dimethyl ethylene cross-bridged homocyclen ligand are presented for the first time. Its novel Mn(2+), Fe(2+), Mn(3+), and Fe(3+) complexes have been synthesized and characterized. X-ray crystal structures were obtained for both manganese complexes, along with five additional Co(3+), Cu(2+), and Zn(2+) structures, the first structural characterization of complexes of this ligand. Each complex has the cis-V configuration of the cross-bridged macrocycle ring, leaving cis labile binding sites for interaction of the complex with oxidants and/or substrates. The copper(II) complex kinetic stability in 5 M HCl and at elevated temperatures was determined and compared to related complexes in the literature. The electronic properties of the manganese and iron complexes were evaluated using solid state magnetic moment determination and acetonitrile solution electronic spectroscopy, revealing high spin metal complexes in all cases. Cyclic voltammetry in acetonitrile of the divalent iron and manganese complexes revealed reversible redox processes, suggesting catalytic reactivity involving electron transfer processes are possible for both complexes. Screening of the Mn(2+) and Fe(2+) complexes for oxidation catalysis using hydrogen peroxide as the terminal oxidant showed both complexes are worthy of continued development.

  4. Reductive electropolymerization of a vinyl-containing poly-pyridyl complex on glassy carbon and fluorine-doped tin oxide electrodes.

    Harrison, Daniel P; Carpenter, Logan S; Hyde, Jacob T


    Controllable electrode surface modification is important in a number of fields, especially those with solar fuels applications. Electropolymerization is one surface modification technique that electrodeposits a polymeric film at the surface of an electrode by utilizing an applied potential to initiate the polymerization of substrates in the Helmholtz layer. This useful technique was first established by a Murray-Meyer collaboration at the University of North Carolina at Chapel Hill in the early 1980s and utilized to study numerous physical phenomena of films containing inorganic complexes as the monomeric substrate. Here, we highlight a procedure for coating electrodes with an inorganic complex by performing reductive electropolymerization of the vinyl-containing poly-pyridyl complex onto glassy carbon and fluorine doped tin oxide coated electrodes. Recommendations on electrochemical cell configurations and troubleshooting procedures are included. Although not explicitly described here, oxidative electropolymerization of pyrrole-containing compounds follows similar procedures to vinyl-based reductive electropolymerization but are far less sensitive to oxygen and water.

  5. Electrochemical properties of the hexacyanoferrate(II)–ruthenium(III) complex immobilized on silica gel surface chemically modified with zirconium(IV) oxide

    Panice, Lucimara B.; Oliveira, Elisangela A. de; Filho, Ricardo A.D. Molin; Oliveira, Daniela P. de [Departamento de Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR (Brazil); Lazarin, Angélica M., E-mail: [Departamento de Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR (Brazil); Andreotti, Elza I.S.; Sernaglia, Rosana L. [Departamento de Química, Universidade Estadual de Maringá, Av. Colombo, 5790, 87020-900 Maringá, PR (Brazil); Gushikem, Yoshitaka [Instituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154, 13084-971 Campinas, São Paulo (Brazil)


    Highlights: • The cyano-bridged mixed valence ruthenium composite material was synthesized. • This newly synthesized compound was incorporated into a carbon paste electrode. • The electrode did not show significant changes in response after six months of use. • The modified electrode is very stable and reproducible. • The electrode sensor was successfully applied for ascorbic acid determination. - Abstract: The chemically modified silica gel with zirconium(IV) oxide was used to immobilize the [Fe(CN){sub 6}]{sup 4−} complex ion initially. The reaction of this material with [Ru(edta)H{sub 2}O]{sup −} complex ion formed the immobilized cyano-bridged mixed valence ruthenium complex, (≡Zr){sub 5}[(edta)RuNCFe(CN){sub 5}]. This material was incorporated into a carbon paste electrode and, its electrochemical properties were investigated. However, for an ascorbic acid solution, an enhancement of the anodic peak current was detected due to electrocatalytic oxidation. The electrode presented the same response for at least 150 successive measurements, with a good repeatability. The modified electrode is very stable and reproducible. The sensor was applied for ascorbic acid determination in pharmaceutical preparation with success.

  6. Structure, bonding and energetics of N-heterocyclic carbene (NHC) stabilized low oxidation state group 2 (Be, Mg, Ca, Sr and Ba) metal complexes: A theoretical study

    Ashim Baishya; V Rao Mundlapati; Sharanappa Nembenna; Himansu S Biswal


    A series of N-heterocyclic carbene stabilized low oxidation state group 2 metal halide and hydrides with metal-metal bonds ([L(X) M-M(X) L]; L = NHC ((CHNH)2C:), M = Be, Mg, Ca, Sr and Ba, and X = Cl or H) has been studied by computational methods. The main objective of this study is to predict whether it is possible to stabilize neutral ligated low oxidation state alkaline-earth metal complexes with metal-metal bonds. The homolytic metal-metal Bond Dissociation Energy (BDE) calculation, Natural Bond Orbital (NBO) and Energy Decomposition Analyses (EDA) on density functional theory (DFT) optimized [L(X)M-M(X)L] complexes revealed that they are as stable as their -diketiminate, guanidinate and -diimine counterparts. The optimized structures of the complexes are in trans-linear geometries. The bond order analyses such as Wiberg Bond Indices (WBI) and Fuzzi Bond Order (FBO) confirm the existence of single bond between two metal atoms, and it is covalent in nature.

  7. Mixed cerium-platinum oxides: Electronic structure of [CeO]Ptn (n = 1, 2) and [CeO2]Pt complex anions and neutrals

    Ray, Manisha; Kafader, Jared O.; Topolski, Josey E.; Jarrold, Caroline Chick


    The electronic structures of several small Ce-Pt oxide complexes were explored using a combination of anion photoelectron (PE) spectroscopy and density functional theory calculations. Pt and Pt2 both accept electron density from CeO diatomic molecules, in which the cerium atom is in a lower-than-bulk oxidation state (+2 versus bulk +4). Neutral [CeO]Pt and [CeO]Pt2 complexes are therefore ionic, with electronic structures described qualitatively as [CeO+2]Pt-2 and [CeO+]Pt2-, respectively. The associated anions are described qualitatively as [CeO+]Pt-2 and [CeO+]Pt2-2, respectively. In both neutrals and anions, the most stable molecular structures determined by calculations feature a distinct CeO moiety, with the positively charged Ce center pointing toward the electron rich Pt or Pt2 moiety. Spectral simulations based on calculated spectroscopic parameters are in fair agreement with the spectra, validating the computationally determined structures. In contrast, when Pt is coupled with CeO2, which has no Ce-localized electrons that can readily be donated to Pt, the anion is described as [CeO2]Pt-. The molecular structure predicted computationally suggests that it is governed by charge-dipole interactions. The neutral [CeO2]Pt complex lacks charge-dipole stabilizing interactions, and is predicted to be structurally very different from the anion, featuring a single Pt-O-Ce bridge bond. The PE spectra of several of the complexes exhibit evidence of photodissociation with Pt- daughter ion formation. The electronic structures of these complexes are related to local interactions in Pt-ceria catalyst-support systems.

  8. Paramagnetic nuclear magnetic resonance relaxation and molecular mechanics studies of the chloroperoxidase-indole complex: insights into the mechanism of chloroperoxidase-catalyzed regioselective oxidation of indole.

    Zhang, Rui; He, Qinghao; Chatfield, David; Wang, Xiaotang


    To unravel the mechanism of chloroperoxidase (CPO)-catalyzed regioselective oxidation of indole, we studied the structure of the CPO-indole complex using nuclear magnetic resonance (NMR) relaxation measurements and computational techniques. The dissociation constant (KD) of the CPO-indole complex was calculated to be approximately 21 mM. The distances (r) between protons of indole and the heme iron calculated via NMR relaxation measurements and molecular docking revealed that the pyrrole ring of indole is oriented toward the heme with its 2-H pointing directly at the heme iron. Both KD and r values are independent of pH in the range of 3.0-6.5. The stability and structure of the CPO-indole complex are also independent of the concentration of chloride or iodide ion. Molecular docking suggests the formation of a hydrogen bond between the NH group of indole and the carboxyl O of Glu 183 in the binding of indole to CPO. Simulated annealing of the CPO-indole complex using r values from NMR experiments as distance restraints reveals that the van der Waals interactions were much stronger than the Coulomb interactions in the binding of indole to CPO, indicating that the association of indole with CPO is primarily governed by hydrophobic rather than electrostatic interactions. This work provides the first experimental and theoretical evidence of the long-sought mechanism that leads to the "unexpected" regioselectivity of the CPO-catalyzed oxidation of indole. The structure of the CPO-indole complex will serve as a lighthouse in guiding the design of CPO mutants with tailor-made activities for biotechnological applications.

  9. Structure and Reactivity of a Thermostable Prokaryotic Nitric-oxide Synthase That Forms a Long-lived Oxy-Heme Complex

    Sudhamsu,J.; Crane, B.


    In an effort to generate more stable reaction intermediates involved in substrate oxidation by nitric-oxide synthases (NOSs), we have cloned, expressed, and characterized a thermostable NOS homolog from the thermophilic bacterium Geobacillus stearothermophilus (gsNOS). As expected, gsNOS forms nitric oxide (NO) from L-arginine via the stable intermediate N-hydroxy L-arginine (NOHA). The addition of oxygen to ferrous gsNOS results in long-lived heme-oxy complexes in the presence (Soret peak 427 nm) and absence (Soret peak 413 nm) of substrates L-arginine and NOHA. The substrate-induced red shift correlates with hydrogen bonding between substrate and heme-bound oxygen resulting in conversion to a ferric heme-superoxy species. In single turnover experiments with NOHA, NO forms only in the presence of H4B. The crystal structure of gsNOS at 3.2 A Angstroms of resolution reveals great similarity to other known bacterial NOS structures, with the exception of differences in the distal heme pocket, close to the oxygen binding site. In particular, a Lys-356 (Bacillus subtilis NOS) to Arg-365 (gsNOS) substitution alters the conformation of a conserved Asp carboxylate, resulting in movement of an Ile residue toward the heme. Thus, a more constrained heme pocket may slow ligand dissociation and increase the lifetime of heme-bound oxygen to seconds at 4 degC. Similarly, the ferric-heme NO complex is also stabilized in gsNOS. The slow kinetics of gsNOS offer promise for studying downstream intermediates involved in substrate oxidation.

  10. Mn(II) Oxidation by the Multicopper Oxidase Complex Mnx: A Coordinated Two-Stage Mn(II)/(III) and Mn(III)/(IV) Mechanism.

    Soldatova, Alexandra V; Romano, Christine A; Tao, Lizhi; Stich, Troy A; Casey, William H; Britt, R David; Tebo, Bradley M; Spiro, Thomas G


    The bacterial manganese oxidase MnxG of the Mnx protein complex is unique among multicopper oxidases (MCOs) in carrying out a two-electron metal oxidation, converting Mn(II) to MnO2 nanoparticles. The reaction occurs in two stages: Mn(II) → Mn(III) and Mn(III) → MnO2. In a companion study , we show that the electron transfer from Mn(II) to the low-potential type 1 Cu of MnxG requires an activation step, likely forming a hydroxide bridge at a dinuclear Mn(II) site. Here we study the second oxidation step, using pyrophosphate (PP) as a Mn(III) trap. PP chelates Mn(III) produced by the enzyme and subsequently allows it to become a substrate for the second stage of the reaction. EPR spectroscopy confirms the presence of Mn(III) bound to the enzyme. The Mn(III) oxidation step does not involve direct electron transfer to the enzyme from Mn(III), which is shown by kinetic measurements to be excluded from the Mn(II) binding site. Instead, Mn(III) is proposed to disproportionate at an adjacent polynuclear site, thereby allowing indirect oxidation to Mn(IV) and recycling of Mn(II). PP plays a multifaceted role, slowing the reaction by complexing both Mn(II) and Mn(III) in solution, and also inhibiting catalysis, likely through binding at or near the active site. An overall mechanism for Mnx-catalyzed MnO2 production from Mn(II) is presented.

  11. Curcumin prevents maleate-induced nephrotoxicity: relation to hemodynamic alterations, oxidative stress, mitochondrial oxygen consumption and activity of respiratory complex I.

    Tapia, E; Sánchez-Lozada, L G; García-Niño, W R; García, E; Cerecedo, A; García-Arroyo, F E; Osorio, H; Arellano, A; Cristóbal-García, M; Loredo, M L; Molina-Jijón, E; Hernández-Damián, J; Negrette-Guzmán, M; Zazueta, C; Huerta-Yepez, S; Reyes, J L; Madero, M; Pedraza-Chaverrí, J


    The potential protective effect of the dietary antioxidant curcumin (120 mg/Kg/day for 6 days) against the renal injury induced by maleate was evaluated. Tubular proteinuria and oxidative stress were induced by a single injection of maleate (400 mg/kg) in rats. Maleate-induced renal injury included increase in renal vascular resistance and in the urinary excretion of total protein, glucose, sodium, neutrophil gelatinase-associated lipocalin (NGAL) and N-acetyl β-D-glucosaminidase (NAG), upregulation of kidney injury molecule (KIM)-1, decrease in renal blood flow and claudin-2 expression besides of necrosis and apoptosis of tubular cells on 24 h. Oxidative stress was determined by measuring the oxidation of lipids and proteins and diminution in renal Nrf2 levels. Studies were also conducted in renal epithelial LLC-PK1 cells and in mitochondria isolated from kidneys of all the experimental groups. Maleate induced cell damage and reactive oxygen species (ROS) production in LLC-PK1 cells in culture. In addition, maleate treatment reduced oxygen consumption in ADP-stimulated mitochondria and diminished respiratory control index when using malate/glutamate as substrate. The activities of both complex I and aconitase were also diminished. All the above-described alterations were prevented by curcumin. It is concluded that curcumin is able to attenuate in vivo maleate-induced nephropathy and in vitro cell damage. The in vivo protection was associated to the prevention of oxidative stress and preservation of mitochondrial oxygen consumption and activity of respiratory complex I, and the in vitro protection was associated to the prevention of ROS production.

  12. Aggregation and Stability of Reduced Graphene Oxide: Complex Roles of Divalent Cations, pH, and Natural Organic Matter

    The aggregation and stability of graphene oxide (GO) and three successively reduced GO (rGO) nanomaterials were investigated. Reduced GO species were partially reduced GO (rGO-1h), intermediately reduced GO (rGO-2h), and fully reduced GO (rGO-5h). Specifically, influence of pH, i...




    Various homoallylalcohols were highly regioselective oxidized with molecular oxygen at the terminal carbon to afford cyclic acetals (alpha-alkoxytetrahydrofurans) using PdNO2Cl(CH3CN)(2) as a catalyst in the presence of CuCl2 and t-butanol or isopropanol.

  14. Catalytic Oxidation with a Non-Heme Iron Complex That Generates a Low-Spin FeIIIOOH Intermediate

    Roelfes, Gerard; Lubben, Marcel; Hage, Ronald; Que, Jr.; Feringa, Bernard


    The antitumor drug bleomycin (BLM) is proposed to act via a low-spin iron(III) hydroperoxide intermediate called “activated bleomycin”. To gain more insight into the mechanistic aspects of catalytic oxidation by these intermediates we have studied the reactivity of [(N4Py)Fe(CH3CN)](ClO4)2 (1) (N4Py

  15. Solid phase microextraction (SPME) for extraction of volatile oxidation products from complex food systems – Pros and cons

    Jacobsen, Charlotte; Horn, Anna Frisenfeldt; Lu, Henna Fung Sieng

    Volatile secondary lipid oxidation products can be identified and quantified by GC-FID or GC-MS. An extraction step is, however, needed before GC analysis. A range of different extraction methods are available such as static headspace, dynamic headspace and SPME. Each of these methods has its adv...

  16. Is Solid Phase Microextraction (SPME) an appropriate method for extraction of volatile oxidation products from complex food systems

    Jacobsen, Charlotte; Horn, Anna Frisenfeldt; Lu, Henna Fung Sieng

    Volatile secondary lipid oxidation products can be identified and quantified by GC-FID or GC-MS. An extraction step is, however, needed before GC analysis. A range of different extraction methods are available such as static headspace, dynamic headspace and SPME. Each of these methods has its adv...

  17. Copper(II) complexes of neuropeptide gamma with point mutations (S8,16A) products of metal-catalyzed oxidation.

    Błaszak, Marta; Jankowska, Elżbieta; Kowalik-Jankowska, Teresa


    To obtain the information about the influence of the serine residues (S8,S16) on the acid-base properties of the neuropeptide gamma, the peptide with point mutations (S8,16A) and its N-acetyl derivative were synthesized. Any additional deprotonations were not observed. It means that the presence of serine residues is necessary in the amino acid sequence of the neuropeptide gamma to have its acid-base properties. The stability constants, stoichiometry and solution structures of copper(II) complexes of the neuropeptide gamma mutants D(1)AGH(4)GQIA(8)H(9)KRH(12)KTDA(16)FVGLM(21)-NH2 (S8,16A) 2ANPG and its N-acetyl derivative Ac-2ANPG were determined in aqueous solution. The equilibrium and structural properties of copper(II) complexes have been characterized by pH-metric, spectroscopic (UV-visible, CD, EPR) and mass spectrometric (MS) methods. At physiological pH7.4 the 2ANPG forms the CuH2L and CuHL complexes in equilibrium with 3N {NH2,βCOO(-)-D(1),2NIm} and 4N {NH2,N(-),2NIm} binding sites, respectively. The exchange Ser on Ala residues does not alter the coordination mode of the peptide. To elucidate the products of the copper(II)-catalyzed oxidation of 2ANPG and Ac-2ANPG the liquid chromatography-mass spectrometry method (LC-MS) and the Cu(II)/H2O2 as a model oxidizing system were employed. For solutions containing a 1:4 peptide-hydrogen peroxide molar ratio oxidation of the methionine residue to methionine sulphoxide was observed. For the 1:1:4 Cu(II)-2ANPG-H2O2 system oxidation of two His residues and cleavage of the G(3)H(4) peptide bond was observed, while for the 1:1:4 Cu(II)-Ac-2ANPG-H2O2 system oxidation of three histidine residues to 2-oxohistidines was also observed.

  18. Transient kinetics of electron transfer reactions of flavodoxin: ionic strength dependence of semiquinone oxidation by cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic acid and computer modeling of reaction complexes.

    Simondsen, R P; Weber, P C; Salemme, F R; Tollin, G


    Electron transfer reactions between Clostridum pasteurianum flavodoxin semiquinone and various oxidants [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic acid (EDTA)] have been studied as a function of ionic strength by using stopped-flow spectrophotometry. The cytochrome c reaction is complicated by the existence of two cytochrome species which react at different rates and whose relative concentrations are ionic strength dependent. Only the faster of these two reactions is considered here. At low ionic strength, complex formation between cytochrome c and flavodoxin is indicated by a leveling off of the pseudo-first-order rate constant at high cytochrome c concentration. This is not observed for either ferricyanide or ferric EDTA. For cytochrome c, the rate and association constants for complex formation were found to increase with decreasing ionic strength, consistent with negative charges on flavodoxin interacting with the positively charged cytochrome electron transfer site. Both ferricyanide and ferric EDTA are negatively charged oxidants, and the rate data respond to ionic strength changes as would be predicted for reactants of the same charge sign. These results demonstrate that electrostatic interactions involving negatively charged groups are important in orienting flavodoxin with respect to oxidants during electron transfer. We have also carried out computer modeling studies of putative complexes of flavodoxin with cytochrome c and ferricyanide, which relate their structural properties to both the observed kinetic behavior and some more general features of physiological electron transfer processes. The results of this study are consistent with the ionic strength behavior described above.

  19. Temperature and solvent structure dependence of VO2+ complexes of pyridine-N-oxide derivatives and their interaction with human serum transferrin.

    Sanna, Daniele; Ugone, Valeria; Micera, Giovanni; Garribba, Eugenio


    The behaviour of the systems formed by VO(2+), 2-hydroxypyridine-N-oxide (Hhpo) and 2-mercaptopyridine-N-oxide (Hmpo) was studied both in solution and in the solid state through the combined application of spectroscopic (EPR and UV-Vis spectroscopy) and DFT methods. The geometry of solid bis-chelated complexes [VOL(2)], with L = hpo and mpo, is square pyramidal, but it can change to cis-[VOL(2)S], where S is a solvent molecule, when these are dissolved in a coordinating solvent. The equilibrium between the square pyramidal and cis-octahedral forms is strongly affected by solvent and temperature. At room temperature, the predominant species is [VOL(2)], which gives a pink colour to the solutions; at lower temperatures, the equilibrium is shifted--partially or completely--toward the formation of cis-[VOL(2)S], which is green. In an acidic environment and in the presence of an excess of ligand, [VOL(2)] can transform into the tris-chelated complex [VL(3)](+), in which vanadium loses the oxido ligand and adopts a hexa-coordinated geometry intermediate between octahedral and trigonal prismatic. 1-Methylimidazole (1-MeIm), which represents a model for His-N coordination, forms mixed complexes with stoichiometry cis-[VOL(2)(1-MeIm)], occupying an equatorial position. In the ternary systems VO(2+)-Hhpo-hTf and VO(2+)-Hmpo-hTf at room temperature and pH 7.4, besides (VO)hTf and (VO)(2)hTf, the mixed species cis-VO(hpo)(2)(hTf) and VO(mpo)(hTf) are observed, with the equatorial binding of an accessible histidine residue. Finally, the contribution of the N-oxide group to (51)V A(z) and A(iso) hyperfine coupling constants, which can be important in the characterisation of similar species, is discussed.

  20. Protein and lipid oxidative damage and complex I content are lower in the brain of budgerigar and canaries than in mice. Relation to aging rate.

    Pamplona, Reinald; Portero-Otín, Manuel; Sanz, Alberto; Ayala, Victoria; Vasileva, Ekaterina; Barja, Gustavo


    What are the mechanisms determining the rate of animal aging? Of the two major classes of endothermic animals, bird species are strikingly long-lived compared to mammals of similar body size and metabolic rate. Thus, they are ideal models to identify longevity-related characteristics not linked to body size or low metabolic rates. Since oxidative stress seems to be related to the basic aging process, we measured specific markers of different kinds of oxidative damage to proteins, like glutamic and aminoadipic semialdehydes (GSA and AASA, specific protein carbonyls), Nɛ-(carboxyethyl)lysine (CEL), Nɛ-(carboxymethyl)lysine (CML), and Nɛ-(malondialdehyde)lysine (MDAL), as well as mitochondrial Complex I content and amino acid and membrane fatty acyl composition, in the brain of short-lived mice (maximum life span [MLSP] 3.5 years) compared with those of long-lived budgerigar 'parakeets' (MLSP, 21 years) and canaries (MLSP, 24 years). The brains of both bird species had significantly lower levels of compounds formed as a result of oxidative (GSA and AASA), glycoxidative (CEL and CML), and lipoxidative (CML and MDAL) protein modifications, as well as a lower levels of mitochondrial complex I protein. Although it is known that fatty acid unsaturation is lower in many tissues of long-lived compared to short-lived mammals, this is not true in the particular case of brain. In agreement with this, we also found that the brain tissue of bugerigars and canaries contains no fewer double bonds than that of mice. Amino acid composition analyses revealed that bird proteins have a significantly lower content of His, Leu and Phe, as well as, interestingly, of methionine, whereas Asp, Glu, Ala, Val, and Lys contents were higher than in the mammals. These results, together with those previously described in other tissues of pigeons (MLSP, 35 years) compared to rats (MLSP, 4 years), indicate that oxidative damage to proteins, lipids and mitochondrial DNA are lower in birds (very