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Sample records for c-h bond activation

  1. C-H bond activation by f-block complexes.

    Science.gov (United States)

    Arnold, Polly L; McMullon, Max W; Rieb, Julia; Kühn, Fritz E

    2015-01-01

    Most homogeneous catalysis relies on the design of metal complexes to trap and convert substrates or small molecules to value-added products. Organometallic lanthanide compounds first gave a tantalizing glimpse of their potential for catalytic C-H bond transformations with the selective cleavage of one C-H bond in methane by bis(permethylcyclopentadienyl)lanthanide methyl [(η(5) -C5 Me5 )2 Ln(CH3 )] complexes some 25 years ago. Since then, numerous metal complexes from across the periodic table have been shown to selectively activate hydrocarbon C-H bonds, but the challenges of closing catalytic cycles still remain; many f-block complexes show great potential in this important area of chemistry. PMID:25384554

  2. Surface-Controlled Mono/Diselective ortho C-H Bond Activation.

    Science.gov (United States)

    Li, Qing; Yang, Biao; Lin, Haiping; Aghdassi, Nabi; Miao, Kangjian; Zhang, Junjie; Zhang, Haiming; Li, Youyong; Duhm, Steffen; Fan, Jian; Chi, Lifeng

    2016-03-01

    One of the most charming and challenging topics in organic chemistry is the selective C-H bond activation. The difficulty arises not only from the relatively large bond-dissociation enthalpy, but also from the poor reaction selectivity. In this work, Au(111) and Ag(111) surfaces were used to address ortho C-H functionalization and ortho-ortho couplings of phenol derivatives. More importantly, the competition between dehydrogenation and deoxygenation drove the diversity of reaction pathways of phenols on surfaces, that is, diselective ortho C-H bond activation on Au(111) surfaces and monoselective ortho C-H bond activation on Ag(111) surfaces. The mechanism of this unprecedented phenomenon was extensively explored by scanning tunneling microscopy, density function theory, and X-ray photoelectron spectroscopy. Our findings provide new pathways for surface-assisted organic synthesis via the mono/diselective C-H bond activation. PMID:26853936

  3. Palladium-Catalyzed Deaminative Phenanthridinone Synthesis from Aniline via C-H Bond Activation.

    Science.gov (United States)

    Yedage, Subhash L; Bhanage, Bhalchandra M

    2016-05-20

    This work reports palladium-catalyzed phenanthridinone synthesis using the coupling of aniline and amide by formation of C-C and C-N bonds in a one-pot fashion via dual C-H bond activation. It involves simultaneous cleavage of four bonds and the formation of two new bonds. The present protocol is ligand-free, takes place under mild reaction conditions, and is environmentally benign as nitrogen gas and water are the only side products. This transformation demonstrates a broad range of aniline and amide substrates with different functional groups and has been scaled up to gram level. PMID:27088815

  4. Time resolved infrared studies of C-H bond activation by organometallics

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    Asplund, M.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States). Chemical Sciences Div.

    1998-06-01

    This work describes how step-scan Fourier Transform Infrared spectroscopy and visible and near infrared ultrafast lasers have been applied to the study of the photochemical activation of C-H bonds in organometallic systems, which allow for the selective breaking of C-H bonds in alkanes. The author has established the photochemical mechanism of C-H activation by Tp{sup *}Rh(CO){sub 2}(Tp{sup *} = HB-Pz{sup *}{sub 3}, Pz = 3,5-dimethylpyrazolyl) in alkane solution. The initially formed monocarbonyl forms a weak solvent complex, which undergoes a change in Tp{sup *} ligand connectivity. The final C-H bond breaking step occurs at different time scales depending on the structure of the alkane. In linear solvents, the time scale is <50 ns and cyclic alkanes is {approximately}200 ps. The reactivity of the Tp{sup *}Rh(CO){sub 2} system has also been studied in aromatic solvents. Here the reaction proceeds through two different pathways, with very different time scales. The first proceeds in a manner analogous to alkanes and takes <50 ns. The second proceeds through a Rh-C-C complex, and takes place on a time scale of 1.8 {micro}s.

  5. Aromatic C-H bond activation revealed by infrared multiphoton dissociation spectroscopy.

    Science.gov (United States)

    Jašíková, Lucie; Hanikýřová, Eva; Schröder, Detlef; Roithová, Jana

    2012-04-01

    Metal-oxide cations are models of catalyst mediating the C-H bond activation of organic substrates. One of the most powerful reagents suggested in the gas phase is based on CuO(+) . Here, we describe the activation of the aromatic C-H bonds of phenanthroline in its complex with CuO(+) . The reaction sequence starts with a hydrogen atom abstraction by the oxygen atom from the 2-position of the phenanthroline ring, followed by OH migration to the ring. Using infrared multiphoton spectroscopy, it is shown that the reaction can be energetically facilitated by additional coordination of a water ligand to the copper ion. As the reaction is intramolecular, a spectroscopic characterization of the product is mandatory in order to unambiguously address the reaction mechanism. PMID:22689621

  6. Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

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    Colby, Denise; Bergman, Robert; Ellman, Jonathan

    2010-05-13

    Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach

  7. Titanium-Thiolate-Aluminum-Carbide Complexes by Multiple C-H Bond Activation.

    Science.gov (United States)

    Guérin; Stephan

    1999-12-16

    All three C-H bonds of a methyl group are activated in the reaction of [Cp(iPr(3)PN)Ti(SR)(2)] with AlMe(3) [Eq. (1)]. The Ti-Al-carbide clusters formed contain a severely distorted tetrahedral carbide carbon atom with a relatively short bond to Ti, which is attributed to a relative increase in the Lewis acidity of the Ti center as a result of the interaction of the S and N donors with Al. PMID:10649329

  8. Modification of Purine and Pyrimidine Nucleosides by Direct C-H Bond Activation

    Directory of Open Access Journals (Sweden)

    Yong Liang

    2015-03-01

    Full Text Available Transition metal-catalyzed modifications of the activated heterocyclic bases of nucleosides as well as DNA or RNA fragments employing traditional cross-coupling methods have been well-established in nucleic acid chemistry. This review covers advances in the area of cross-coupling reactions in which nucleosides are functionalized via direct activation of the C8-H bond in purine and the C5-H or C6-H bond in uracil bases. The review focuses on Pd/Cu-catalyzed couplings between unactivated nucleoside bases with aryl halides. It also discusses cross-dehydrogenative arylations and alkenylations as well as other reactions used for modification of nucleoside bases that avoid the use of organometallic precursors and involve direct C-H bond activation in at least one substrate. The scope and efficiency of these coupling reactions along with some mechanistic considerations are discussed.

  9. Activation of C-H and B-H bonds through agostic bonding: an ELF/QTAIM insight.

    Science.gov (United States)

    Zins, Emilie-Laure; Silvi, Bernard; Alikhani, M Esmaïl

    2015-04-14

    Agostic bonding is of paramount importance in C-H bond activation processes. The reactivity of the σ C-H bond thus activated will depend on the nature of the metallic center, the nature of the ligand involved in the interaction and co-ligands, as well as on geometric parameters. Because of their importance in organometallic chemistry, a qualitative classification of agostic bonding could be very much helpful. Herein we propose descriptors of the agostic character of bonding based on the electron localization function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) topological analysis. A set of 31 metallic complexes taken, or derived, from the literature was chosen to illustrate our methodology. First, some criteria should prove that an interaction between a metallic center and a σ X-H bond can indeed be described as "agostic" bonding. Then, the contribution of the metallic center in the protonated agostic basin, in the ELF topological description, may be used to evaluate the agostic character of bonding. A σ X-H bond is in agostic interaction with a metal center when the protonated X-H basin is a trisynaptic basin with a metal contribution strictly larger than the numerical uncertainty, i.e. 0.01 e. In addition, it was shown that the weakening of the electron density at the X-Hagostic bond critical point with respect to that of X-Hfree well correlates with the lengthening of the agostic X-H bond distance as well as with the shift of the vibrational frequency associated with the νX-H stretching mode. Furthermore, the use of a normalized parameter that takes into account the total population of the protonated basin, allows the comparison of the agostic character of bonding involved in different complexes. PMID:25760795

  10. Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels

    Energy Technology Data Exchange (ETDEWEB)

    Fiedler, Dorothea; Leung, Dennis H.; Raymond, Kenneth N.; Bergman, Robert G.

    2004-11-27

    Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M{sub 4}L{sub 6} supramolecular tetrahedron can encapsulate a variety of cationic guests, with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated and the C-H bond activation of aldehydes occurs, with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.

  11. Inserting CO2 into Aryl C-H Bonds of Metal-Organic Frameworks: CO2 Utilization for Direct Heterogeneous C-H Activation.

    Science.gov (United States)

    Gao, Wen-Yang; Wu, Haifan; Leng, Kunyue; Sun, Yinyong; Ma, Shengqian

    2016-04-25

    Described for the first time is that carbon dioxide (CO2 ) can be successfully inserted into aryl C-H bonds of the backbone of a metal-organic framework (MOF) to generate free carboxylate groups, which serve as Brønsted acid sites for efficiently catalyzing the methanolysis of epoxides. The work delineates the very first example of utilizing CO2 for heterogeneous C-H activation and carboxylation reactions on MOFs, and opens a new avenue for CO2 chemical transformations under mild reaction conditions. PMID:27080057

  12. Direct Functionalization of Nitrogen Heterocycles via Rh-Catalyzed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Jared; Bergman, Robert; Ellman, Jonathan

    2008-02-04

    Nitrogen heterocycles are present in many compounds of enormous practical importance, ranging from pharmaceutical agents and biological probes to electroactive materials. Direct funtionalization of nitrogen heterocycles through C-H bond activation constitutes a powerful means of regioselectively introducing a variety of substituents with diverse functional groups onto the heterocycle scaffold. Working together, our two groups have developed a family of Rh-catalyzed heterocycle alkylation and arylation reactions that are notable for their high level of functional-group compatibility. This Account describes their work in this area, emphasizing the relevant mechanistic insights that enabled synthetic advances and distinguished the resulting transformations from other methods. They initially discovered an intramolecular Rh-catalyzed C-2-alkylation of azoles by alkenyl groups. That reaction provided access to a number of di-, tri-, and tetracyclic azole derivatives. They then developed conditions that exploited microwave heating to expedite these reactions. While investigating the mechanism of this transformation, they discovered that a novel substrate-derived Rh-N-heterocyclic carbene (NHC) complex was involved as an intermediate. They then synthesized analogous Rh-NHC complexes directly by treating precursors to the intermediate [RhCl(PCy{sub 3}){sub 2}] with N-methylbenzimidazole, 3-methyl-3,4-dihydroquinazolein, and 1-methyl-1,4-benzodiazepine-2-one. Extensive kinetic analysis and DFT calculations supported a mechanism for carbene formation in which the catalytically active RhCl(PCy{sub 3}){sub 2} fragment coordinates to the heterocycle before intramolecular activation of the C-H bond occurs. The resulting Rh-H intermediate ultimately tautomerizes to the observed carbene complex. With this mechanistic information and the discovery that acid co-catalysts accelerate the alkylation, they developed conditions that efficiently and intermolecularly alkylate a variety of

  13. Graphene Oxide Catalyzed C-H Bond Activation: The Importance Oxygen Functional Groups for Biaryl Construction

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    Gao, Yongjun; Tang, Pei; Zhou, Hu; Zhang, Wei; Yang, Hanjun; Yan, Ning; Hu, Gang; Mei, Donghai; Wang, Jianguo; Ma, Ding

    2016-02-24

    A heterogeneous, inexpensive and environment-friendly carbon catalytic system was developed for the C-H bond arylation of benzene resulting in the subsequent formation of biaryl compounds. The oxygen-containing groups on these graphene oxide sheets play an essential role in the observed catalytic activity. The catalytic results of model compounds and DFT calculations show that these functional groups promote this reaction by stabilization and activation of K ions at the same time of facilitating the leaving of I. And further mechanisms studies show that it is the charge induced capabilities of oxygen groups connected to specific carbon skeleton together with the giant π-reaction platform provided by the π-domain of graphene that played the vital roles in the observed excellent catalytic activity. D. Mei acknowledges the support from the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory.

  14. Synthesis of a Benzodiazepine-derived Rhodium NHC Complex by C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, Roberg G.; Gribble, Jr., Michael W.; Ellman, Jonathan A.

    2008-01-30

    The synthesis and characterization of a Rh(I)-NHC complex generated by C-H activation of 1,4-benzodiazepine heterocycle are reported. This complex constitutes a rare example of a carbene tautomer of a 1,4-benzodiazepine aldimine stabilized by transition metal coordination and demonstrates the ability of the catalytically relevant RhCl(PCy{sub 3}){sub 2} fragment to induce NHC-forming tautomerization of heterocycles possessing a single carbene-stabilizing heteroatom. Implications for the synthesis of benzodiazepines and related pharmacophores via C-H functionalization are discussed.

  15. Intramolecular C-H Bond Activation through a Flexible Ester Linkage

    Czech Academy of Sciences Publication Activity Database

    Shaffer, Christopher; Schröder, Detlef; Gutz, Ch.; Lutzen, A.

    2012-01-01

    Roč. 51, č. 32 (2012), s. 8097-8100. ISSN 1433-7851 Grant ostatní: European Research Council(XE) AdG HORIZOMS Institutional support: RVO:61388963 Keywords : C-H activation * copper * gas phase * ion mobility * oxidation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 13.734, year: 2012

  16. Aromatic C-H bond activation revealed by infrared multiphoton dissociation spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Jašíková, L.; Hanikýřová, E.; Schröder, Detlef; Roithová, J.

    2012-01-01

    Roč. 47, č. 4 (2012), s. 460-465. ISSN 1076-5174 Grant ostatní: GA ČR(CZ) GAP207/11/0338; Seventh Framework Program(XE) 226716 Institutional research plan: CEZ:AV0Z40550506 Keywords : C-H activation * density functional theory calculations * ion spectroscopy * metal oxides * rearrangements Subject RIV: CC - Organic Chemistry Impact factor: 3.214, year: 2012

  17. Biomass Oxidation: Formyl C-H Bond Activation by the Surface Lattice Oxygen of Regenerative CuO Nanoleaves.

    Science.gov (United States)

    Amaniampong, Prince N; Trinh, Quang Thang; Wang, Bo; Borgna, Armando; Yang, Yanhui; Mushrif, Samir H

    2015-07-27

    An integrated experimental and computational investigation reveals that surface lattice oxygen of copper oxide (CuO) nanoleaves activates the formyl C-H bond in glucose and incorporates itself into the glucose molecule to oxidize it to gluconic acid. The reduced CuO catalyst regains its structure, morphology, and activity upon reoxidation. The activity of lattice oxygen is shown to be superior to that of the chemisorbed oxygen on the metal surface and the hydrogen abstraction ability of the catalyst is correlated with the adsorption energy. Based on the present investigation, it is suggested that surface lattice oxygen is critical for the oxidation of glucose to gluconic acid, without further breaking down the glucose molecule into smaller fragments, because of C-C cleavage. Using CuO nanoleaves as catalyst, an excellent yield of gluconic acid is also obtained for the direct oxidation of cellobiose and polymeric cellulose, as biomass substrates. PMID:26119659

  18. Iron-Carbonyl-Catalyzed Redox-Neutral [4+2] Annulation of N-H Imines and Internal Alkynes by C-H Bond Activation.

    Science.gov (United States)

    Jia, Teng; Zhao, Chongyang; He, Ruoyu; Chen, Hui; Wang, Congyang

    2016-04-18

    Stoichiometric C-H bond activation of arenes mediated by iron carbonyls was reported by Pauson as early as in 1965, yet the catalytic C-H transformations have not been developed. Herein, an iron-catalyzed annulation of N-H imines and internal alkynes to furnish cis-3,4-dihydroisoquinolines is described, and represents the first iron-carbonyl-catalyzed C-H activation reaction of arenes. Remarkablely, this is also the first redox-neutral [4+2] annulation of imines and alkynes proceeding by C-H activation. The reaction also features only cis stereoselectivity and excellent atom economy as neither base, nor external ligand, nor additive is required. Experimental and theoretical studies reveal an oxidative addition mechanism for C-H bond activation to afford a dinuclear ferracycle and a synergetic diiron-promoted H-transfer to the alkyne as the turnover-determining step. PMID:27002210

  19. Catalytic C-H bond stannylation: a new regioselective pathway to C-Sn bonds via C-H bond functionalization.

    Science.gov (United States)

    Doster, Meghan E; Hatnean, Jillian A; Jeftic, Tamara; Modi, Sunjay; Johnson, Samuel A

    2010-09-01

    The ubiquitous Stille coupling reaction utilizes Sn-C bonds and is of great utility to organic chemists. Unlike the B-C bonds used in the Miyaura-Suzuki coupling reaction, which are readily obtained via direct borylation of C-H bonds, routes to organotin compounds via direct C-H bond functionalization are lacking. Here we report that the nickel-catalyzed reaction of fluorinated arenes and pyridines with vinyl stannanes does not provide the expected vinyl compounds via C-F activation but rather provides new Sn-C bonds via C-H functionalization with the loss of ethylene. This mechanism provides a new unanticipated methodology for the direct conversion of C-H bonds to carbon-heteroatom bonds. PMID:20690675

  20. Intramolecular C-H bond activation and redox isomerization across two-electron mixed valence diiridium cores.

    Energy Technology Data Exchange (ETDEWEB)

    Esswein, A. J.; Veige, A. S.; Piccoli, P. M. B.; Schultz, A. J.; Nocera, D. G.; MIT

    2008-03-24

    Metal-metal cooperativity enables the reaction of carbon-based substrates at diiridium two-electron mixed valence centers. Arylation of Ir{sub 2}{sup 0,II}(tfepma){sub 3}Cl{sub 2} (1) (tfepma = bis[(bistrifluoroethoxy)phosphino]methylamine) with RMgBr (R = C{sub 6}H{sub 5} and C{sub 6}D{sub 5}) is followed by C-H bond activation to furnish the bridging benzyne complex Ir{sub 2}II,II(tfepma){sub 3}({mu}-C{sub 6}H4)(C{sub 6}H{sub 5})H (2), as the kinetic product. At ambient temperature, 2 isomerizes to Ir{sub 2}{sup I,III}(tfepma){sub 3}({mu}-C{sub 6}H4)(C{sub 6}H{sub 5})H (3) (k{sub obs} = 9.57 {+-} 0.10 x 10{sup -5} s{sup -1} at 31.8 C, {Delta}H{sup {+-}} = 21.7 {+-} 0.3 kcal/mol, {Delta}S{sup {+-}} = -7.4 {+-} 0.9 eu), in which the benzyne moiety is conserved and the Ir{sup III} center is ligated by terminal hydride and phenyl groups. The same reaction course is observed for arylation of 1 with C{sub 6}D{sub 5}MgBr to produce 2-d{sub 10} and 3-d{sub 10} accompanied by an inverse isotope effect, k{sub h}/k{sub d} = 0.44 (k{sub obs} = 2.17 {+-} 0.10 x 10{sup -4} s{sup -1} in C{sub 6}D{sub 6} solution at 31.8 C, {Delta}H{sup {+-}} = 24.9 {+-} 0.7 kcal/mol, {Delta}S{sup {+-}} = -6.4 {+-} 2.4 eu). 2 reacts swiftly with hydrogen to provide Ir{sub 2}{sup II,II}(tfepma){sub 3}H{sub 4} as both the syn and anti isomers (4-syn and 4-anti, respectively). The hydrides of 4-syn were directly located by neutron diffraction analysis. X-ray crystallographic examination of 2, 2-d{sub 10}, 3, and 4-syn indicates that cooperative reactivity at the bimetallic diiridium core is facilitated by the ability of the two-electron mixed valence framework to accommodate the oxidation state changes and ligand rearrangements attendant to the reaction of the substrate.

  1. Direct Synthesis of Protoberberine Alkaloids by Rh-Catalyzed C-H Bond Activation as the Key Step.

    Science.gov (United States)

    Jayakumar, Jayachandran; Cheng, Chien-Hong

    2016-01-26

    A one-pot reaction of substituted benzaldehydes with alkyne-amines by a Rh-catalyzed C-H activation and annulation to afford various natural and unnatural protoberberine alkaloids is reported. This reaction provides a convenient route for the generation of a compound library of protoberberine salts, which recently have attracted great attention because of their diverse biological activities. In addition, pyridinium salt derivatives can also be formed in good yields from α,β-unsaturated aldehydes and amino-alkynes. This reaction proceeds with excellent regioselectivity and good functional group compatibility under mild reaction conditions by using O2 as the oxidant. PMID:26689172

  2. Promotional effects of chemisorbed oxygen and hydroxide in the activation of C-H and O-H bonds over transition metal surfaces

    Science.gov (United States)

    Hibbitts, David; Neurock, Matthew

    2016-08-01

    Electronegative coadsorbates such as atomic oxygen (O*) and hydroxide (OH*) can act as Brønsted bases when bound to Group 11 as well as particular Group 8-10 metal surfaces and aid in the activation of X-H bonds. First-principle density functional theory calculations were carried out to systematically explore the reactivity of the C-H bonds of methane and surface methyl intermediates as well as the O-H bond of methanol directly and with the assistance of coadsorbed O* and OH* intermediates over Group 11 (Cu, Ag, and Au) and Group 8-10 transition metal (Ru, Rh, Pd, Os, Ir, and Pt) surfaces. C-H as well as O-H bond activation over the metal proceeds via a classic oxidative addition type mechanism involving the insertion of the metal center into the C-H or O-H bond. O* and OH* assist C-H and O-H activation over particular Group 11 and Group 8-10 metal surfaces via a σ-bond metathesis type mechanism involving the oxidative addition of the C-H or O-H bond to the metal along with a reductive deprotonation of the acidic C-H and O-H bond over the M-O* or M-OH* site pair. The O*- and OH*-assisted C-H activation paths are energetically preferred over the direct metal catalyzed C-H scission for all Group 11 metals (Cu, Ag, and Au) with barriers that are 0.4-1.5 eV lower than those for the unassisted routes. The barriers for O*- and OH*-assisted C-H activation of CH4 on the Group 8-10 transition metals, however, are higher than those over the bare transition metal surfaces by as much as 1.4 eV. The C-H activation of adsorbed methyl species show very similar trends to those for CH4 despite the differences in structure between the weakly bound methane and the covalently adsorbed methyl intermediates. The activation of the O-H bond of methanol is significantly promoted by O* as well as OH* intermediates over both the Group 11 metals (Cu, Ag, and Au) as well as on all Group 8-10 metals studied (Ru, Rh, Pd, Os, Ir, and Pt). The O*- and OH*-assisted CH3O-H barriers are 0.6 to 2

  3. Trifluoromethylallylation of Heterocyclic C-H Bonds with Allylic Carbonates under Rhodium Catalysis.

    Science.gov (United States)

    Choi, Miji; Park, Jihye; Sharma, Satyasheel; Jo, Hyeim; Han, Sangil; Jeon, Mijin; Mishra, Neeraj Kumar; Han, Sang Hoon; Lee, Jong Suk; Kim, In Su

    2016-06-01

    The rhodium(III)-catalyzed γ-trifluoromethylallylation of various heterocyclic C-H bonds with CF3-substituted allylic carbonates is described. These reactions provide direct access to linear CF3-containing allyl frameworks with complete trans-selectivity via C-H bond activation followed by a formal SN-type reaction pathway. PMID:27187625

  4. Driving Forces for Covalent Assembly of Porphyrins by Selective C-H Bond Activation and Intermolecular Coupling on a Copper Surface.

    Science.gov (United States)

    Floris, Andrea; Haq, Sam; In't Veld, Mendel; Amabilino, David B; Raval, Rasmita; Kantorovich, Lev

    2016-05-11

    Recent synthesis of covalent organic assemblies at surfaces has opened the promise of producing robust nanostructures for functional interfaces. To uncover how this new chemistry works at surfaces and understand the underlying mechanisms that control bond-breaking and bond-making processes at specific positions of the participating molecules, we study here the coupling reaction of tetra(mesityl)porphyrin molecules, which creates covalently connected networks on the Cu(110) surface by utilizing the 4-methyl groups as unique connection points. Using scanning tunneling microscopy (STM), state-of-the-art density functional theory (DFT), and Nudged Elastic Band (NEB) calculations, we show that the unique directionality of the covalent bonding is found to stem from a chain of highly selective C-H activation and dehydrogenation processes, followed by specific intermolecular C-C coupling reactions that are facilitated by the surface, by steric constraints, and by anisotropic molecular diffusion. These insights provide the first steps toward developing synthetic rules for complex two-dimensional covalent organic chemistry that can be enacted directly at a surface to deliver specific macromolecular structures designed for specific functions. PMID:27097295

  5. The Molybdenum Active Site of Formate Dehydrogenase Is Capable of Catalyzing C-H Bond Cleavage and Oxygen Atom Transfer Reactions.

    Science.gov (United States)

    Hartmann, Tobias; Schrapers, Peer; Utesch, Tillmann; Nimtz, Manfred; Rippers, Yvonne; Dau, Holger; Mroginski, Maria Andrea; Haumann, Michael; Leimkühler, Silke

    2016-04-26

    Formate dehydrogenases (FDHs) are capable of performing the reversible oxidation of formate and are enzymes of great interest for fuel cell applications and for the production of reduced carbon compounds as energy sources from CO2. Metal-containing FDHs in general contain a highly conserved active site, comprising a molybdenum (or tungsten) center coordinated by two molybdopterin guanine dinucleotide molecules, a sulfido and a (seleno-)cysteine ligand, in addition to a histidine and arginine residue in the second coordination sphere. So far, the role of these amino acids in catalysis has not been studied in detail, because of the lack of suitable expression systems and the lability or oxygen sensitivity of the enzymes. Here, the roles of these active site residues is revealed using the Mo-containing FDH from Rhodobacter capsulatus. Our results show that the cysteine ligand at the Mo ion is displaced by the formate substrate during the reaction, the arginine has a direct role in substrate binding and stabilization, and the histidine elevates the pKa of the active site cysteine. We further found that in addition to reversible formate oxidation, the enzyme is further capable of reducing nitrate to nitrite. We propose a mechanistic scheme that combines both functionalities and provides important insights into the distinct mechanisms of C-H bond cleavage and oxygen atom transfer catalyzed by formate dehydrogenase. PMID:27054466

  6. Polymerization of ethylene by silica-supported dinuclear Cr(III) sites through an initiation step involving C-H bond activation.

    Science.gov (United States)

    Conley, Matthew P; Delley, Murielle F; Siddiqi, Georges; Lapadula, Giuseppe; Norsic, Sébastien; Monteil, Vincent; Safonova, Olga V; Copéret, Christophe

    2014-02-10

    The insertion of an olefin into a preformed metal-carbon bond is a common mechanism for transition-metal-catalyzed olefin polymerization. However, in one important industrial catalyst, the Phillips catalyst, a metal-carbon bond is not present in the precatalyst. The Phillips catalyst, CrO3 dispersed on silica, polymerizes ethylene without an activator. Despite 60 years of intensive research, the active sites and the way the first CrC bond is formed remain unknown. We synthesized well-defined dinuclear Cr(II) and Cr(III) sites on silica. Whereas the Cr(II) material was a poor polymerization catalyst, the Cr(III) material was active. Poisoning studies showed that about 65 % of the Cr(III) sites were active, a far higher proportion than typically observed for the Phillips catalyst. Examination of the spent catalyst and isotope labeling experiments showed the formation of a Si-(μ-OH)-Cr(III) species, consistent with an initiation mechanism involving the heterolytic activation of ethylene at Cr(III) O bonds. PMID:24505006

  7. Iron(IV)hydroxide pKa and the Role of Thiolate Ligation in C-H Bond Activation by Cytochrome P450

    OpenAIRE

    Yosca, Timothy H.; Rittle, Jonathan; Krest, Courtney M.; Onderko, Elizabeth L.; Silakov, Alexey; Calixto, Julio C.; Behan, Rachel K.; Green, Michael T.

    2013-01-01

    Cytochrome P450 enzymes activate oxygen at heme iron centers to oxidize relatively inert substrate carbon-hydrogen bonds. Cysteine thiolate coordination to iron is posited to increase the pKa of compound II, an iron(IV)hydroxide complex, correspondingly lowering the one-electron reduction potential of compound I, the active catalytic intermediate, and decreasing the driving force for deleterious autooxidation of tyrosine and tryptophan residues in the enzyme’s framework. Here we report the pr...

  8. Metal-catalysed azidation of tertiary C-H bonds suitable for late-stage functionalization

    Science.gov (United States)

    Sharma, Ankit; Hartwig, John F.

    2015-01-01

    Many enzymes oxidize unactivated aliphatic C-H bonds selectively to form alcohols; however, biological systems do not possess enzymes that catalyse the analogous aminations of C-H bonds. The absence of such enzymes limits the discovery of potential medicinal candidates because nitrogen-containing groups are crucial to the biological activity of therapeutic agents and clinically useful natural products. In one prominent example illustrating the importance of incorporating nitrogen-based functionality, the conversion of the ketone of erythromycin to the -N(Me)CH2- group in azithromycin leads to a compound that can be dosed once daily with a shorter treatment time. For such reasons, synthetic chemists have sought catalysts that directly convert C-H bonds to C-N bonds. Most currently used catalysts for C-H bond amination are ill suited to the intermolecular functionalization of complex molecules because they require excess substrate or directing groups, harsh reaction conditions, weak or acidic C-H bonds, or reagents containing specialized groups on the nitrogen atom. Among C-H bond amination reactions, those forming a C-N bond at a tertiary alkyl group would be particularly valuable, because this linkage is difficult to form from ketones or alcohols that might be created in a biosynthetic pathway by oxidation. Here we report a mild, selective, iron-catalysed azidation of tertiary C-H bonds that occurs without excess of the valuable substrate. The reaction tolerates aqueous environments and is suitable for the functionalization of complex structures in the late stages of a multistep synthesis. Moreover, this azidation makes it possible to install a range of nitrogen-based functional groups, including those from Huisgen `click' cycloadditions and the Staudinger ligation. We anticipate that these reactions will create opportunities to modify natural products, their precursors and their derivatives to produce analogues that contain different polarity and charge as a

  9. Evidence for 5-Center 4-Electron Bonding in (C...H...C...H...C) Array

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Juzakov, Gleb

    2003-01-01

    Roč. 68, č. 21 (2003), s. 8284-8286. ISSN 0022-3263 R&D Projects: GA AV ČR IAA4072006 Institutional research plan: CEZ:AV0Z4072921 Keywords : multicenter bonding * generalized population analysis * multicenter bond indices Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.297, year: 2003

  10. Active groups for oxidative activation of C-H bond in C{sub 2}-C{sub 5} paraffins on V-P-O catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Zazhigalov, V.A. [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Fizicheskoj Khimii

    1998-12-31

    For the first time in scientific literature, in our joint work with Dr. G. Ladwig in 1978 it was established phase portraite of the oxide vanadium-phosphorus system within wide range of P/V ratios from 0.5 to 3.2. Some later those data were confirmed. By investigation of the properties of individual vanadium-phosphorus phases it was also shown that the active component of such catalysts in n-butane oxidation was vanadyl pyrophosphate phase (VO){sub 2}Pr{sub 2}O{sub 7}. From then the conclusion has been evidenced by numerous publications and at present it has been out of doubt practically all over the world. It was hypothized that the unique properties of (VO){sub 2}P{sub 2}O{sub 7} in the reaction of n-butane oxidation could be explained by the presence of paired vanadyl groups and nearness of the distances between neighbouring vanadyl pairs and that between the first and fourth carbon atoms in n-butane molecule. The molecule activation occured at the latter atoms by proton abstraction. A comparison of the results on n-butane and butenes oxidation over vanadyl pyrophosphate allowed to conclude that the paraffin oxidation did not take place due to the molecule dehydrogenation process at the first stage of its conversion. Up to now, more than 100 papers related to paraffins oxidation over vanadyl pyrophosphate and the physico-chemical properties of the catalyst have been published. The process of n-butane oxidation is realized in practice. But still, the question about the nature of active sites of the catalyst and the reaction mechanism remains open and provokes further investigations. The present paper deals with our opinion about the problem and the experimental results supporting it. (orig.)

  11. C8-Selective Acylation of Quinoline N-Oxides with α-Oxocarboxylic Acids via Palladium-Catalyzed Regioselective C-H Bond Activation.

    Science.gov (United States)

    Chen, Xiaopei; Cui, Xiuling; Wu, Yangjie

    2016-08-01

    A facile and efficient protocol for palladium-catalyzed C8-selective acylation of quinoline N-oxides with α-oxocarboxylic acids has been developed. In this approach, N-oxide was utilized as a stepping stone for the remote C-H functionalization. The reactions proceeded efficiently under mild reaction conditions with excellent regioselectivity and broad functional group tolerance. PMID:27441527

  12. Rhodium-catalyzed C-C coupling reactions via double C-H activation.

    Science.gov (United States)

    Li, Shuai-Shuai; Qin, Liu; Dong, Lin

    2016-05-18

    Various rhodium-catalyzed double C-H activations are reviewed. These powerful strategies have been developed to construct C-C bonds, which might be widely embedded in complex aza-fused heterocycles, polycyclic skeletons and heterocyclic scaffolds. In particular, rhodium(iii) catalysis shows good selectivity and reactivity to functionalize the C-H bond, generating reactive organometallic intermediates in most of the coupling reactions. Generally, intermolecular, intramolecular and multi-component coupling reactions via double C-H activations with or without heteroatom-assisted chelation are discussed in this review. PMID:27099126

  13. C-H and H-H Bond Activation via Ligand Dearomatization/Rearomatization of a PN3P-Rhodium(I) Complex

    KAUST Repository

    Huang, Kuo-Wei

    2015-04-13

    A neutral complex PN3P-Rh(I)Cl (2) was prepared from a reaction of the PN3P pincer ligand (1) with [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene). Upon treatment with a suitable base, H–H and Csp2–H activation reactions can be achieved through the deprotonation/reprotonation of one of the N–H arms and dearomatization/rearomatization of the central pyridine ring with the oxidation state of Rh remaining I.

  14. C-H bond halogenation catalyzed or mediated by copper: an overview.

    Science.gov (United States)

    Hao, Wenyan; Liu, Yunyun

    2015-01-01

    Carbon-halogen (C-X) bonds are amongst the most fundamental groups in organic synthesis, they are frequently and widely employed in the synthesis of numerous organic products. The generation of a C-X bond, therefore, constitutes an issue of universal interest. Herein, the research advances on the copper-catalyzed and mediated C-X (X = F, Cl, Br, I) bond formation via direct C-H bond transformation is reviewed. PMID:26664634

  15. Tetra-substituted olefin synthesis using palladium-catalysed C-H activation

    OpenAIRE

    Lopez Suarez, Laura; Suarez, Laura Lopez

    2012-01-01

    In an effort to obtain more efficient and greener chemical transformations, a substantial amount of research interest has been directed towards the use of arene C-H bonds as functional groups. Hydroarylation of alkynes through direct functionalisation of C-H bonds has been studied in recent years leading to the development of high-yielding metal-mediated processes. The main aim of the current work is the addition of a third component in the hydroarylation of alkynes trough C-H activation, in ...

  16. Non-specificity of C-H bond rupture by γ radiolysis of 3-methylpentane glass

    International Nuclear Information System (INIS)

    Some authors using esr data claimed that there is a high selectivity for the rupture of a particular C-H bond after the radiolysis of solid branched alkanes. Using the identification of dimer isomers and very low total dose, we have established the identity of the trapped radical produced at 77 K by the radiolysis of 3-methylpentane, all the parent radicals are formed. If there is a different probability of breaking a particular C-H bond, the bond rupture is not much less selective in liquid than in the glassy state

  17. Synthetic Transformations through Alkynoxy-Palladium Interactions and C-H Activation.

    Science.gov (United States)

    Minami, Yasunori; Hiyama, Tamejiro

    2016-01-19

    Organic synthesis based on straightforward transformations is essential for environmentally benign manufacturing for the invention of novel pharmaceuticals, agrochemicals, and organoelectronic materials in order to ultimately realize a sustainable society. Metal-catalyzed C-H bond-cleaving functionalization has become a promising method for achieving the above goal. For site-selective C-H bond cleavage, so-called directing groups, i.e., ligands attached to substrates, are employed. Commonly utilized directing groups are carbonyls, imines, carboxyls, amides, and pyridyls, which σ-donate electron pairs to metals. On the other hand, unsaturated substrates such as alkenes and alkynes, which participate largely as reactants in organic synthesis, are prepared readily by a wide variety of synthetic transformations and are also employed as reactants in organometallic chemistry. Moreover, such unsaturated groups form complexes with some metals by ligation of their p orbitals via donation and back-donation. However, the use of unsaturated bonds as directing groups has not been studied extensively. We have been involved in the development of methods for the cleavage of C-H bonds by means of transition-metal catalysts to achieve new carbon-carbon bond-forming reactions and incidentally came to focus on the alkynoxy group (-OC≡C-), which shows a ketene-like resonance structure. We expected the alkynoxy group to interact electrophilically with a low-valent transition-metal complex in order to cleave adjacent C-H bonds. In this Account, we summarize our recent achievements on C-H activation based on interactions of palladium with the alkynoxy group in alkynyl aryl ethers. The alkynoxy group plays two roles in the transformation: as a directing group for adjacent C-H bond activation and as an acceptor for the carbon and hydrogen fragments. A typical example is palladium-catalyzed ortho-C-H bond activation in alkynoxyarenes followed by sequential insertion/annulation with

  18. C-H Bond Oxidation Catalyzed by an Imine-Based Iron Complex: A Mechanistic Insight.

    Science.gov (United States)

    Olivo, Giorgio; Nardi, Martina; Vìdal, Diego; Barbieri, Alessia; Lapi, Andrea; Gómez, Laura; Lanzalunga, Osvaldo; Costas, Miquel; Di Stefano, Stefano

    2015-11-01

    A family of imine-based nonheme iron(II) complexes (LX)2Fe(OTf)2 has been prepared, characterized, and employed as C-H oxidation catalysts. Ligands LX (X = 1, 2, 3, and 4) stand for tridentate imine ligands resulting from spontaneous condensation of 2-pycolyl-amine and 4-substituted-2-picolyl aldehydes. Fast and quantitative formation of the complex occurs just upon mixing aldehyde, amine, and Fe(OTf)2 in a 2:2:1 ratio in acetonitrile solution. The solid-state structures of (L1)2Fe(OTf)(ClO4) and (L3)2Fe(OTf)2 are reported, showing a low-spin octahedral iron center, with the ligands arranged in a meridional fashion. (1)H NMR analyses indicate that the solid-state structure and spin state is retained in solution. These analyses also show the presence of an amine-imine tautomeric equilibrium. (LX)2Fe(OTf)2 efficiently catalyze the oxidation of alkyl C-H bonds employing H2O2 as a terminal oxidant. Manipulation of the electronic properties of the imine ligand has only a minor impact on efficiency and selectivity of the oxidative process. A mechanistic study is presented, providing evidence that C-H oxidations are metal-based. Reactions occur with stereoretention at the hydroxylated carbon and selectively at tertiary over secondary C-H bonds. Isotopic labeling analyses show that H2O2 is the dominant origin of the oxygen atoms inserted in the oxygenated product. Experimental evidence is provided that reactions involve initial oxidation of the complexes to the ferric state, and it is proposed that a ligand arm dissociates to enable hydrogen peroxide binding and activation. Selectivity patterns and isotopic labeling studies strongly suggest that activation of hydrogen peroxide occurs by heterolytic O-O cleavage, without the assistance of a cis-binding water or alkyl carboxylic acid. The sum of these observations provides sound evidence that controlled activation of H2O2 at (LX)2Fe(OTf)2 differs from that occurring in biomimetic iron catalysts described to date. PMID

  19. C-H and N-H bond dissociation energies of small aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Barckholtz, C.; Barckholtz, T.A.; Hadad, C.M.

    1999-01-27

    A survey of computational methods was undertaken to calculate the homolytic bond dissociation energies (BDEs) of the C-H and N-H bonds in monocyclic aromatic molecules that are representative of the functionalities present in coal. These include six-membered rings (benzene, pyridine, pyridazine, pyrimidine, pyrazine) and five-membered rings (furan, thiophene, pyrrole, oxazole). By comparison of the calculated C-H BDEs with the available experimental values for these aromatic molecules, the B3LYP/6-31G(d) level of theory was selected to calculate the BDEs of polycyclic aromatic hydrocarbons (PAHs), including carbonaceous PAHs (naphthalene, anthracene, pyrene, coronene) and heteroatomic PAHs (benzofuran, benzothiophene, indole, benzoxazole, quinoline, isoquinoline, dibenzofuran, carbazole). The cleavage of a C-H or a N-H bond generates a {sigma} radical that is, in general, localized at the site from which the hydrogen atom was removed. However, delocalization of the unpaired electron results in {approximately} 7 kcal {center{underscore}dot} mol{sup {minus}1} stabilization of the radical with respect to the formation of phenyl when the C-H bond is adjacent to a nitrogen atom in the azabenzenes. Radicals from five-membered rings are {approximately} 6 kcal {center{underscore}dot} mol{sup {minus}1} less stable than those formed from six-membered rings due to both localization of the spin density and geometric factors. The location of the heteroatoms in the aromatic ring affects the C-H bond strengths more significantly than does the size of the aromatic network. Therefore, in general, the monocyclic aromatic molecules can be used to predict the C-H BDE of the large PAHs within 1 kcal {center{underscore}dot} mol{sup {minus}1}.

  20. Site-selective and stereoselective functionalization of unactivated C-H bonds.

    Science.gov (United States)

    Liao, Kuangbiao; Negretti, Solymar; Musaev, Djamaladdin G; Bacsa, John; Davies, Huw M L

    2016-05-12

    The laboratory synthesis of complex organic molecules relies heavily on the introduction and manipulation of functional groups, such as carbon-oxygen or carbon-halogen bonds; carbon-hydrogen bonds are far less reactive and harder to functionalize selectively. The idea of C-H functionalization, in which C-H bonds are modified at will instead of the functional groups, represents a paradigm shift in the standard logic of organic synthesis. For this approach to be generally useful, effective strategies for site-selective C-H functionalization need to be developed. The most practical solutions to the site-selectivity problem rely on either intramolecular reactions or the use of directing groups within the substrate. A challenging, but potentially more flexible approach, would be to use catalyst control to determine which site in a particular substrate would be functionalized. Here we describe the use of dirhodium catalysts to achieve highly site-selective, diastereoselective and enantioselective C-H functionalization of n-alkanes and terminally substituted n-alkyl compounds. The reactions proceed in high yield, and functional groups such as halides, silanes and esters are compatible with this chemistry. These studies demonstrate that high site selectivity is possible in C-H functionalization reactions without the need for a directing or anchoring group present in the molecule. PMID:27172046

  1. Facile P-C/C-H Bond Cleavage Reactivity of Nickel Bis(diphosphine) Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shaoguang; Li, Haixia; Appel, Aaron M.; Hall, Michael B.; Bullock, R. Morris

    2016-07-04

    Unusual cleavage of P-C and C-H bonds of the P2N2 ligand in heteroleptic [Ni(P2N2)(diphosphine)]2+ complexes results in the formation of an iminium formyl nickelate featuring a C,P,P-tridentate coordination mode.

  2. Efficient photolytic C-H bond functionalization of alkylbenzene with hypervalent iodine(iii) reagent.

    Science.gov (United States)

    Sakamoto, Ryu; Inada, Tsubasa; Selvakumar, Sermadurai; Moteki, Shin A; Maruoka, Keiji

    2016-03-01

    A practical approach to radical C-H bond functionalization by the photolysis of a hypervalent iodine(iii) reagent is presented. The photolysis of [bis(trifluoroacetoxy)iodo]benzene (PIFA) leads to the generation of trifluoroacetoxy radicals, which allows the smooth transformation of various alkylbenzenes to the corresponding benzyl ester compounds under mild reaction conditions. PMID:26686276

  3. Gas-phase chemistry of Sc(CH{sub 3}){sub 2}{sup +} with alkenes: Activation of allylic C-H bonds by a d{sup 0} system and the migratory insertion of C=C bonds into Sc{sup +}-CH{sub 3} bonds

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yongqing; Hill, Y.D.; Freiser, B.S. [Purdue Univ., West Lafayette, IN (United States)] [and others

    1992-11-04

    The gas-phase chemistry of Sc(CH{sub 3}){sub 2}{sup +} with alkenes was studied by Fourier transform mass spectrometry. The metal center on Sc(CH{sub 3}){sub 2}{sup +} is d{sup 0}, providing an opportunity to study alternative mechanisms of C-C or C-H activation other than the most common one involving oxidative addition. The elimination of H{sub 2} is observed in the reaction of Sc(CH{sub 3}){sub 2}{sup +} with ethylene, and the product ScC{sub 4}H{sub 8}{sup +} and ScC{sub 6}H{sub 10}{sup +} ions have a metal(methyl)(allyl) and metal-bisallyl structure, respectively, consistent with a proposed reaction mechanism involving the consecutive migratory insertion of ethylenes into the scandium-methyl bonds. In addition, theoretical calculations indicate that the metal(methyl)(allyl) structure is between 10 and 20 kcal/mol more stable than the metal(1-butene) isomer. Sc(CH{sub 3}){sub 2}{sup +} reacts with propene to form predominantly ScC{sub 4}H{sub 8}{sup +} by loss of CH{sub 4}, with minor amounts of ScC{sub 3}H{sub 4}{sup +} and ScC{sub 4}H{sub 6}{sup +} also observed. ScC{sub 4}H{sub 6}{sup +} is formed as either the exclusive or the predominant product ion in the reactions of Sc(CH{sub 3}){sub 2}{sup +} with butenes. Sc(CH{sub 3}){sub 2} reacts with cyclopentene to form predominantly ScC{sub 6}H{sub 8}{sup +} by losing CH{sub 4} and H{sub 2}. Isotope labeling studies with Sc(CD{sub 3}){sub 2}{sup +} and other structure studies indicate that all of the alkenes studied, with the exception of ethylene, react with Sc(CH{sub 3}){sub 2}{sup +} via a multicentered {sigma}-bond metathesis mechanism to activate allylic C-H bonds. Finally, the dehydrogenation reactions of Sc{sup +} with n-butane and neopentane were revisited, and a new mechanism is proposed for such chemistry in light of the new results from this study. 34 refs., 5 figs., 2 tabs.

  4. A steric tethering approach enables palladium-catalysed C-H activation of primary amino alcohols

    Science.gov (United States)

    Calleja, Jonas; Pla, Daniel; Gorman, Timothy W.; Domingo, Victoriano; Haffemayer, Benjamin; Gaunt, Matthew J.

    2015-12-01

    Aliphatic primary amines are a class of chemical feedstock essential to the synthesis of higher-order nitrogen-containing molecules, commonly found in biologically active compounds and pharmaceutical agents. New methods for the construction of complex amines remain a continuous challenge to synthetic chemists. Here, we outline a general palladium-catalysed strategy for the functionalization of aliphatic C-H bonds within amino alcohols, an important class of small molecule. Central to this strategy is the temporary conversion of catalytically incompatible primary amino alcohols into hindered secondary amines that are capable of undergoing a sterically promoted palladium-catalysed C-H activation. Furthermore, a hydrogen bond between amine and catalyst intensifies interactions around the palladium and orients the aliphatic amine substituents in an ideal geometry for C-H activation. This catalytic method directly transforms simple, easily accessible amines into highly substituted, functionally concentrated and structurally diverse products, and can streamline the synthesis of biologically important amine-containing molecules.

  5. A Germanium Isocyanide Complex Featuring (n → π*) Back-Bonding and Its Conversion to a Hydride/Cyanide Product via C-H Bond Activation under Mild Conditions

    OpenAIRE

    Brown, Zachary; Vasko, Petra; Fettinger, James; Tuononen, Heikki; Power, Philip

    2012-01-01

    Reaction of the diarylgermylene Ge(ArMe6)2 [ArMe6 = C6H3-2,6-(C6H2-2,4,6-(CH3)3)2] with tert-butyl isocyanide gave the Lewis adduct species (ArMe6)2GeCNBut, in which the isocyanide ligand displays a decreased C–N stretching frequency consistent with an n → π* back-bonding interaction. Density functional theory confirmed that the HOMO is a Ge–C bonding combination between the lone pair of electrons on the germanium atom and the C–N π* orbital of the isocyanide ligand. The complex undergoes fac...

  6. Catalytic C-H bond functionalisation chemistry: the case for quasi-heterogeneous catalysis.

    Science.gov (United States)

    Reay, Alan J; Fairlamb, Ian J S

    2015-11-25

    This feature article examines the potential of heterogeneous Pd species to mediate catalytic C-H bond functionalisation processes employing suitable substrates (e.g. aromatic/heteroaromatic compounds). A focus is placed on the reactivity of supported and non-supported Pd nanoparticle (PdNPs) catalysts, in addition to the re-appropriation of well-established heterogeneous Pd catalysts such as Pd/C. Where possible, reasonable comparisons are made between PdNPs and traditional 'homogeneous' Pd precatalyst sources (which form PdNPs). The involvement of higher order Pd species in traditional cross-coupling processes, such as Mizoroki-Heck, Sonogashira and Suzuki-Miyaura reactions, allows the exemplification of potential future topics for study in the area of catalytic C-H bond functionalisation processes. PMID:26439875

  7. Recent advances in copper-catalyzed C-H bond amidation.

    Science.gov (United States)

    Wan, Jie-Ping; Jing, Yanfeng

    2015-01-01

    Copper catalysis has been known as a powerful tool for its ubiquitous application in organic synthesis. One of the fundamental utilities of copper catalysis is in the C-N bond formation by using carbon sources and nitrogen functional groups such as amides. In this review, the recent progress in the amidation reactions employing copper-catalyzed C-H amidation is summarized. PMID:26664644

  8. Boron-Catalyzed Aromatic C-H Bond Silylation with Hydrosilanes.

    Science.gov (United States)

    Ma, Yuanhong; Wang, Baoli; Zhang, Liang; Hou, Zhaomin

    2016-03-23

    Metal-free catalytic C-H silylation of a series of aromatic compounds such as N,N-disubstituted anilines with various hydrosilanes has been achieved for the first time using commercially available B(C6F5)3 as a catalyst. This protocol features simple and neutral reaction conditions, high regioselectivity, wide substrate scope (up to 40 examples), Si-Cl bond compatibility, and no requirement for a hydrogen acceptor. PMID:26959863

  9. Direct Oxidation of Aliphatic C-H Bonds in Amino-Containing Molecules under Transition-Metal-Free Conditions.

    Science.gov (United States)

    Li, Xin; Che, Xing; Chen, Gui-Hua; Zhang, Jun; Yan, Jia-Lei; Zhang, Yun-Fei; Zhang, Li-Sheng; Hsu, Chao-Ping; Gao, Yi Qin; Shi, Zhang-Jie

    2016-03-18

    By employing a simple, inexpensive, and transition-metal-free oxidation system, secondary C-H bonds in a series of phthaloyl protected primary amines and amino acid derivatives were oxidized to carbonyls with good regioselectivities. This method could also be applied to oxidize tertiary C-H bonds and modify synthetic dipeptides. PMID:26949833

  10. Mild metal-catalyzed C-H activation: examples and concepts.

    Science.gov (United States)

    Gensch, T; Hopkinson, M N; Glorius, F; Wencel-Delord, J

    2016-05-21

    Organic reactions that involve the direct functionalization of non-activated C-H bonds represent an attractive class of transformations which maximize atom- and step-economy, and simplify chemical synthesis. Due to the high stability of C-H bonds, these processes, however, have most often required harsh reaction conditions, which has drastically limited their use as tools for the synthesis of complex organic molecules. Following the increased understanding of mechanistic aspects of C-H activation gained over recent years, great strides have been taken to design and develop new protocols that proceed efficiently under mild conditions and duly benefit from improved functional group tolerance and selectivity. In this review, we present the current state of the art in this field and detail C-H activation transformations reported since 2011 that proceed either at or below ambient temperature, in the absence of strongly acidic or basic additives or without strong oxidants. Furthermore, by identifying and discussing the major strategies that have led to these improvements, we hope that this review will serve as a useful conceptual overview and inspire the next generation of mild C-H transformations. PMID:27072661

  11. A direct experimental evidence for an aromatic C-H⋯O hydrogen bond by fluorescence-detected infrared spectroscopy

    Science.gov (United States)

    Venkatesan, V.; Fujii, A.; Ebata, T.; Mikami, N.

    2004-08-01

    Formation of a weak aromatic C-H⋯O hydrogen bond has been discerned both experimentally and computationally in the 1,2,4,5-tetrafluorobenzene (TFB)-water system. The intermolecular structure of the isolated TFB-water cluster in a supersonic jet was characterized using fluorescence-detected infrared spectroscopy. The formation of a weak hydrogen bond in the cluster was directly evidenced by a low-frequency shift and intensity enhancement of the hydrogen-bonded aromatic C-H stretch in the TFB moiety. This is the first direct observation of an aromatic C-H⋯O hydrogen bond in isolated gas phase clusters.

  12. The C-H bond dissociation enthalpies in fused N-heterocyclic compounds

    Science.gov (United States)

    Wang, Ying-Xing; Zheng, Wen-Rui; Ding, Lan-Lan

    2016-03-01

    The C-H bond dissociation enthalpies (BDEs) of the 26 N, O, S-containing mono-heterocyclic compounds were evaluated using the composite high-level ab initio methods G3 and G4. The C-H BDEs for 32 heterocyclic compounds were calculated using 8 types of density functional theory (DFT) methods. Comparing with the experimental values, the BMK method gave the lowest root mean square error (RMSE) of 7.2 kJ/mol. Therefore, the C-H BDEs of N-fused-heterocyclic compounds at different positions were investigated by the BMK method. By NBO analysis two linear relationships between the C-H BDEs of quinoline and isoquinoline with natural charges qC/ e in molecules and with natural charges qC/ e in radicals were found. The substituent effects on C(α)-H BDEs in N-fused-heterocyclic compounds were also discussed. It was found that there are two linear relationships between the C(α)-H BDEs of quinoline and isoquinoline derivatives with natural charges qC(α)/ e for the EDGs and CEGs substituents.

  13. The Breathing Orbital Valence Bond Method in Diffusion Monte Carlo: C-H Bond Dissociation ofAcetylene

    Energy Technology Data Exchange (ETDEWEB)

    Domin, D.; Braida, Benoit; Lester Jr., William A.

    2008-05-30

    This study explores the use of breathing orbital valence bond (BOVB) trial wave functions for diffusion Monte Carlo (DMC). The approach is applied to the computation of the carbon-hydrogen (C-H) bond dissociation energy (BDE) of acetylene. DMC with BOVB trial wave functions yields a C-H BDE of 132.4 {+-} 0.9 kcal/mol, which is in excellent accord with the recommended experimental value of 132.8 {+-} 0.7 kcal/mol. These values are to be compared with DMC results obtained with single determinant trial wave functions, using Hartree-Fock orbitals (137.5 {+-} 0.5 kcal/mol) and local spin density (LDA) Kohn-Sham orbitals (135.6 {+-} 0.5 kcal/mol).

  14. Aromatic Cyanoalkylation through Double C-H Activation Mediated by Ni(III).

    Science.gov (United States)

    Zhou, Wen; Zheng, Shuai; Schultz, Jason W; Rath, Nigam P; Mirica, Liviu M

    2016-05-11

    Herein we report an atom- and step-economic aromatic cyanoalkylation reaction that employs nitriles as building blocks and proceeds through Csp(2)-H and Csp(3)-H bond activation steps mediated by Ni(III). In addition to cyanomethylation with MeCN, regioselective α-cyanoalkylation was observed with various nitrile substrates to generate secondary and tertiary nitriles. Importantly, to the best of our knowledge these are the first examples of C-H bond activation reactions occurring at a Ni(III) center, which may exhibit different reactivity and selectivity profiles than those corresponding to analogous Ni(II) centers. These studies provide guiding principles to design catalytic C-H activation and functionalization reactions involving high-valent Ni species. PMID:27120207

  15. Insertion of singlet chlorocarbenes across C-H bonds in alkanes: Evidence for two phase mechanism

    Indian Academy of Sciences (India)

    M Ramalingam; K Ramasami; P Venuvanalingam

    2007-09-01

    Transition states for the insertion reactions of singlet mono and dichlorocarbenes (1CHCl and 1CCl2) into C-H bonds of alkanes (methane, ethane, propane and -butane) have been investigated at MP2 and DFT levels with 6-31g ( , ) basis set. The of 1CHCl and 1CCl2 may interact with alkane’s filled fragment orbital of either or symmetry. So chlorocarbenes insertion reactions have been investigated for both (/) approaches. The approach has been adjudicated to be the minimum energy path over the approach both at the MP2 and DFT levels. Mulliken, NPA and ESP derived charge analyses have been carried out along the minimal energy reaction path using the IRC method for 1CHCl and 1CCl2 insertions into the primary and secondary C-H bonds of propane. The occurrence of TSs either in the electrophilic or nucleophilic phase has been identified through NBO charge analyses in addition to the net charge flow from alkane to the carbene moiety.

  16. Enzymatic hydroxylation of an unactivated methylene C-H bond guided by molecular dynamics simulations

    Science.gov (United States)

    Narayan, Alison R. H.; Jiménez-Osés, Gonzalo; Liu, Peng; Negretti, Solymar; Zhao, Wanxiang; Gilbert, Michael M.; Ramabhadran, Raghunath O.; Yang, Yun-Fang; Furan, Lawrence R.; Li, Zhe; Podust, Larissa M.; Montgomery, John; Houk, K. N.; Sherman, David H.

    2015-08-01

    The hallmark of enzymes from secondary metabolic pathways is the pairing of powerful reactivity with exquisite site selectivity. The application of these biocatalytic tools in organic synthesis, however, remains under-utilized due to limitations in substrate scope and scalability. Here, we report how the reactivity of a monooxygenase (PikC) from the pikromycin pathway is modified through computationally guided protein and substrate engineering, and applied to the oxidation of unactivated methylene C-H bonds. Molecular dynamics and quantum mechanical calculations were used to develop a predictive model for substrate scope, site selectivity and stereoselectivity of PikC-mediated C-H oxidation. A suite of menthol derivatives was screened computationally and evaluated through in vitro reactions, where each substrate adhered to the predicted models for selectivity and conversion to product. This platform was also expanded beyond menthol-based substrates to the selective hydroxylation of a variety of substrate cores ranging from cyclic to fused bicyclic and bridged bicyclic compounds.

  17. Formation and High Reactivity of the anti-Dioxo Form of High-Spin μ-Oxodioxodiiron(IV) as the Active Species That Cleaves Strong C-H Bonds.

    Science.gov (United States)

    Kodera, Masahito; Ishiga, Shin; Tsuji, Tomokazu; Sakurai, Katsutoshi; Hitomi, Yutaka; Shiota, Yoshihito; Sajith, P K; Yoshizawa, Kazunari; Mieda, Kaoru; Ogura, Takashi

    2016-04-18

    Recently, it was shown that μ-oxo-μ-peroxodiiron(III) is converted to high-spin μ-oxodioxodiiron(IV) through O-O bond scission. Herein, the formation and high reactivity of the anti-dioxo form of high-spin μ-oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic-absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. Decay of μ-oxodioxodiiron(IV) was greatly accelerated on addition of substrate. The reactivity order of substrates is toluenebond cleavage of ethylbenzene than the most reactive diiron system reported so far. The KIE for the reaction with toluene/[D8 ]toluene is 95 at -30 °C, which the largest in diiron systems reported so far. The present diiron complex efficiently catalyzes the oxidation of various alkanes with H2 O2 . PMID:26970337

  18. Rhodium(III)-Catalyzed Directed ortho-C-H Bond Functionalization of Aromatic Ketazines via C-S and C-C Coupling.

    Science.gov (United States)

    Wen, Jing; Wu, An; Wang, Mingyang; Zhu, Jin

    2015-11-01

    Described herein is a convenient and efficient method for sulfuration and olefination of aromatic ketazines via rhodium-catalyzed oxidative C-H bond activation. A range of substituted substrates are supported, and a possible mechanism is proposed according to experimental results of kinetic isotopic effect, reversibility studies, and catalysis of rhodacycle intermediate c1. PMID:26417874

  19. A Metallacycle Fragmentation Strategy for Vinyl Transfer from Enol Carboxylates to Secondary Alcohol C-H Bonds via Osmium- or Ruthenium-Catalyzed Transfer Hydrogenation.

    Science.gov (United States)

    Park, Boyoung Y; Luong, Tom; Sato, Hiroki; Krische, Michael J

    2015-06-24

    A strategy for catalytic vinyl transfer from enol carboxylates to activated secondary alcohol C-H bonds is described. Using XPhos-modified ruthenium(0) or osmium(0) complexes, enol carboxylate-carbonyl oxidative coupling forms transient β-acyloxy-oxametallacycles, which eliminate carboxylate to deliver allylic ruthenium(II) or osmium(II) alkoxides. Reduction of the metal(II) salt via hydrogen transfer from the secondary alcohol reactant releases the product of carbinol C-H vinylation and regenerates ketone and zero-valent catalyst. PMID:26066660

  20. Photocatalytic benzylic C-H bond oxidation with a flavin scandium complex.

    Science.gov (United States)

    Mühldorf, Bernd; Wolf, Robert

    2015-05-18

    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. PMID:25647055

  1. Catalytic C-H bond addition of pyridines to allenes by a rare-Earth catalyst.

    Science.gov (United States)

    Song, Guoyong; Wang, Baoli; Nishiura, Masayoshi; Hou, Zhaomin

    2015-06-01

    The catalytic C-H addition of pyridines to allenes has been achieved for the first time by using a half-sandwich scandium catalyst, thus constituting a straightforward and atom-economical route for the synthesis of alkenylated pyridine derivatives. The reaction proceeded regio- and stereoselectively, affording a new family of alkenylated pyridine compounds which are otherwise difficult to synthesize. A cationic Sc-η(2) -pyridyl species was isolated and confirmed to be a key catalyst species in this transformation. PMID:25899713

  2. Synthesis of isoquinolines via Rh-catalyzed C-H activation/C-N cyclization with diazodiesters or diazoketoesters as a C2 source.

    Science.gov (United States)

    Wang, Jie; Zha, Shanke; Chen, Kehao; Zhang, Feifei; Zhu, Jin

    2016-06-01

    Synthesis of isoquinolines based on efficient C-C and C-N bond formation through Rh(iii)-catalyzed C-H activation and subsequent intramolecular cyclization is reported. Diazodiesters serving as a C2 source in the newly formed heterocycles are first demonstrated. Additionally, the Rh(iii)-catalyzed direct C-H activation/cyclization of benzimidates with diazoketoesters is also described. PMID:27146107

  3. Lactamization of sp(2) C-H Bonds with CO2 : Transition-Metal-Free and Redox-Neutral.

    Science.gov (United States)

    Zhang, Zhen; Liao, Li-Li; Yan, Si-Shun; Wang, Lei; He, Yun-Qi; Ye, Jian-Heng; Li, Jing; Zhi, Yong-Gang; Yu, Da-Gang

    2016-06-13

    The first direct use of carbon dioxide in the lactamization of alkenyl and heteroaryl C-H bonds to synthesize important 2-quinolinones and polyheterocycles in moderate to excellent yields is reported. Carbon dioxide, a nontoxic, inexpensive, and readily available greenhouse gas, acts as an ideal carbonyl source. Importantly, this transition-metal-free and redox-neutral process is eco-friendly and desirable for the pharmaceutical industry. Moreover, these reactions feature a broad substrate scope, good functional group tolerance, facile scalability, and easy product derivatization. PMID:27095584

  4. Synthesis of Dihydropyridines and Pyridines from Imines and Alkynes via C-H Activation

    Energy Technology Data Exchange (ETDEWEB)

    Ellman, Jonathan A.; Colby, Denise; Bergman, Robert

    2007-11-20

    A convenient one-pot C-H alkenylation/electrocyclization/aromatization sequence has been developed for the synthesis of highly substituted pyridine derivatives from alkynes and {alpha},{beta}-unsaturated N-benzyl aldimines and ketimines that proceeds through dihydropyridine intermediates. A new class of ligands for C-H activation was developed, providing broader scope for the alkenylation step than could be achieved with previously reported ligands. Substantial information was obtained about the mechanism of the reaction. This included the isolation of a C-H activated complex and its structure determination by X-ray analysis; in addition, kinetic simulations using the Copasi software were employed to determine rate constants for this transformation, implicating facile C-H oxidative addition and slow reductive elimination steps.

  5. A Versatile, Traceless C-H Activation-Based Approach for the Synthesis of Heterocycles.

    Science.gov (United States)

    Zhou, Shuguang; Wang, Jinhu; Zhang, Feifei; Song, Chao; Zhu, Jin

    2016-05-20

    A versatile, traceless C-H activation-based approach for the synthesis of diversified heterocycles is reported. Rh(III)-catalyzed, N-amino-directed C-H alkenylation generates either olefination products or indoles (in situ annulation) in an atom- and step-economic manner at room temperature. The remarkable reactivity endowed by this directing group enables scale-up of the reaction to a 10 g scale at a very low catalyst loading (0.01 mol %/0.1 mol %). Ex situ annulation of olefination product provides entry into an array of heterocycles. PMID:27135982

  6. Iridium(iii)-catalyzed regioselective direct arylation of sp(2) C-H bonds with diaryliodonium salts.

    Science.gov (United States)

    Gao, Pan; Liu, Li; Shi, Zhuangzhi; Yuan, Yu

    2016-08-01

    A regioselective direct arylation of arenes and olefins at the ortho position is reported. The key to the high selectivity is the appropriate choice of diaryliodonium salts as the arylating reagent in the presence of a cationic iridium(iii) catalyst. The coordination of the metal with an oxygen atom or a nitrogen atom and subsequent C-H activation allows for direct arylation with coupling partners. This reaction proceeds under mild reaction conditions and with a high tolerance of various functional groups including many halide functional groups. PMID:27381238

  7. Synthesis of all eight L-glycopyranosyl donors using C-H activation

    DEFF Research Database (Denmark)

    Frihed, Tobias; Pedersen, Christian Marcus; Bols, Mikael

    2014-01-01

    The synthesis of all eight rare, but biologically important L-hexoses as the according thioglycosyl donors was achieved through a procedure involving the C-H activation of their corresponding 6-deoxy-L-hexoses. The key steps of the procedure were the silylation of the OH group at C4 followed by an...

  8. Identification of the Chemical Bonding Prompting Adhesion of a-C:H Thin Films on Ferrous Alloy Intermediated by a SiCx:H Buffer Layer.

    Science.gov (United States)

    Cemin, F; Bim, L T; Leidens, L M; Morales, M; Baumvol, I J R; Alvarez, F; Figueroa, C A

    2015-07-29

    Amorphous carbon (a-C) and several related materials (DLCs) may have ultralow friction coefficients that can be used for saving-energy applications. However, poor chemical bonding of a-C/DLC films on metallic alloys is expected, due to the stability of carbon-carbon bonds. Silicon-based intermediate layers are employed to enhance the adherence of a-C:H films on ferrous alloys, although the role of such buffer layers is not yet fully understood in chemical terms. The chemical bonding of a-C:H thin films on ferrous alloy intermediated by a nanometric SiCx:H buffer layer was analyzed by X-ray photoelectron spectroscopy (XPS). The chemical profile was inspected by glow discharge optical emission spectroscopy (GDOES), and the chemical structure was evaluated by Raman and Fourier transform infrared spectroscopy techniques. The nature of adhesion is discussed by analyzing the chemical bonding at the interfaces of the a-C:H/SiCx:H/ferrous alloy sandwich structure. The adhesion phenomenon is ascribed to specifically chemical bonding character at the buffer layer. Whereas carbon-carbon (C-C) and carbon-silicon (C-Si) bonds are formed at the outermost interface, the innermost interface is constituted mainly by silicon-iron (Si-Fe) bonds. The oxygen presence degrades the adhesion up to totally delaminate the a-C:H thin films. The SiCx:H deposition temperature determines the type of chemical bonding and the amount of oxygen contained in the buffer layer. PMID:26135943

  9. 2008 C. H. McCloy lecture. Social psychology and physical activity: back to the future.

    Science.gov (United States)

    Gill, Diane L

    2009-12-01

    In the early 1970s, both my academic career and the psychology subdiscipline within kinesiology began as "social psychology and physical activity. "Since then, sport and exercise psychology research has shifted away from the social to a narrower biopsycho-(no social) approach, and professional practice has focused on the elite rather than the larger public. Psychology can contribute to an integrative and relevant professional discipline by going back to the future as social psychology and physical activity and by incorporating three of C. H. McCloy's themes (a) evidence-based practice, (b) beyond dualisms, and (c) commitment to public service. Our scholarship must move beyond dualisms to recognize complexities and connections and be truly scholarship for practice. Social psychology and physical activity can serve the public by advocating for inclusive, empowering physical activity programs that promote health and well being for all. PMID:20025109

  10. Synthesis of Indole-2-carboxylate Derivatives via Palladium-Catalyzed Aerobic Amination of Aryl C-H Bonds.

    Science.gov (United States)

    Clagg, Kyle; Hou, Haiyun; Weinstein, Adam B; Russell, David; Stahl, Shannon S; Koenig, Stefan G

    2016-08-01

    A direct oxidative C-H amination affording 1-acetyl indolecarboxylates starting from 2-acetamido-3-arylacrylates has been achieved. Indole-2-carboxylates can be targeted with a straightforward deacetylation of the initial reaction products. The C-H amination reaction is carried out using a catalytic Pd(II) source with oxygen as the terminal oxidant. The scope and application of this chemistry is demonstrated with good to high yields for numerous electron-rich and electron-poor substrates. Further reaction of selected products via Suzuki arylation and deacetylation provides access to highly functionalized indole structures. PMID:27404018

  11. Iron-Catalyzed C-H Functionalization Processes.

    Science.gov (United States)

    Cera, Gianpiero; Ackermann, Lutz

    2016-10-01

    Iron-catalyzed C-H activation has recently emerged as an increasingly powerful tool for the step-economical transformation of unreactive C-H bonds. Particularly, the recent development of low-valent iron catalysis has set the stage for novel C-H activation strategies via chelation assistance. The low-cost, natural abundance, and low toxicity of iron prompted its very recent application in organometallic C-H activation catalysis. An overview of the use of iron catalysis in C-H activation processes is summarized herein up to May 2016. PMID:27573499

  12. Copper-mediated C-H activation/C-S cross-coupling of heterocycles with thiols

    KAUST Repository

    Ranjit, Sadananda

    2011-11-04

    We report the synthesis of a series of aryl- or alkyl-substituted 2-mercaptobenzothiazoles by direct thiolation of benzothiazoles with aryl or alkyl thiols via copper-mediated aerobic C-H bond activation in the presence of stoichiometric CuI, 2,2′-bipyridine and Na 2CO 3. We also show that the approach can be extended to thiazole, benzimidazole, and indole substrates. In addition, we present detailed mechanistic investigations on the Cu(I)-mediated direct thiolation reactions. Both computational studies and experimental results reveal that the copper-thiolate complex [(L)Cu(SR)] (L: nitrogen-based bidentate ligand such as 2,2′-bipyridine; R: aryl or alkyl group) is the first reactive intermediate responsible for the observed organic transformation. Furthermore, our computational studies suggest a stepwise reaction mechanism based on a hydrogen atom abstraction pathway, which is more energetically feasible than many other possible pathways including β-hydride elimination, single electron transfer, hydrogen atom transfer, oxidative addition/reductive elimination, and σ-bond metathesis. © 2011 American Chemical Society.

  13. Unified view of oxidative C-H bond cleavage and sulfoxidation by a nonheme iron(IV)-oxo complex via Lewis acid-promoted electron transfer.

    Science.gov (United States)

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

    2014-04-01

    Oxidative C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by a nonheme iron(IV)-oxo complex, [(N4Py)Fe(IV)(O)](2+) (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine), were remarkably enhanced by the presence of triflic acid (HOTf) and Sc(OTf)3 in acetonitrile at 298 K. All the logarithms of the observed second-order rate constants of both the oxidative C-H bond cleavage and sulfoxidation reactions exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes between PCET and MCET were taken into account, respectively. Thus, the mechanisms of both the oxidative C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by [(N4Py)Fe(IV)(O)](2+) in the presence of HOTf and Sc(OTf)3 have been unified as the rate-determining electron transfer, which is coupled with binding of [(N4Py)Fe(IV)(O)](2+) by proton (PCET) and Sc(OTf)3 (MCET). There was no deuterium kinetic isotope effect (KIE) on the oxidative C-H bond cleavage of toluene via the PCET pathway, whereas a large KIE value was observed with Sc(OTf)3, which exhibited no acceleration of the oxidative C-H bond cleavage of toluene. When HOTf was replaced by DOTf, an inverse KIE (0.4) was observed for PCET from both toluene and [Ru(II)(bpy)3](2+) (bpy =2,2'-bipyridine) to [(N4Py)Fe(IV)(O)](2+). The PCET and MCET reactivities of [(N4Py)Fe(IV)(O)](2+) with Brønsted acids and various metal triflates have also been unified as a single correlation with a quantitative measure of the Lewis acidity. PMID:24605985

  14. Synthesis and characterization of ethylbis(2-pyridylethyl)amineruthenium complexes and two different types of C-H bond cleavage at an ethylene arm.

    Science.gov (United States)

    Fukui, Sohei; Kajihara, Akari; Hirano, Toshiyuki; Sato, Fumitoshi; Suzuki, Noriyuki; Nagao, Hirotaka

    2011-06-01

    Ruthenium complexes bearing ethylbis(2-pyridylethyl)amine (ebpea), which has flexible -C(2)H(4)- arms between the amine and the pyridyl groups and coordinates to a metal center in facial and meridional modes, have been synthesized and characterized. Three trichloro complexes, fac-[Ru(III)Cl(3)(ebpea)] (fac-[1]), mer-[Ru(III)Cl(3)(ebpea)] (mer-[1]), and mer-[Ru(II)Cl(3){η(2)-N(C(2)H(5))(C(2)H(4)py)═CH-CH(2)py}] (mer-[2]), were synthesized using the Ru blue solution. Formation of mer-[2] proceeded via a C-H activation of the CH(2) group next to the amine nitrogen atom of the ethylene arm. Reduction reactions of fac- and mer-[1] afforded a triacetonitrile complex mer-[Ru(II)(CH(3)CN)(3)(ebpea)](PF(6))(2) (mer-[3](PF(6))(2)). Five nitrosyl complexes fac-[RuX(2)(NO)(ebpea)]PF(6) (X = Cl for fac-[4]PF(6); X = ONO(2) for fac-[5]PF(6)) and mer-[RuXY(NO)(ebpea)]PF(6) (X = Cl, Y = Cl for mer-[4]PF(6); X = Cl, Y = CH(3)O for mer-[6]PF(6); X = Cl, Y = OH for mer-[7]PF(6)) were synthesized and characterized by X-ray crystallography. A reaction of mer-[2] in H(2)O-C(2)H(5)OH at room temperature afforded mer-[1]. Oxidation of C(2)H(5)OH in H(2)O-C(2)H(5)OH and i-C(3)H(7)OH in H(2)O-i-C(3)H(7)OH to acetaldehyde and acetone by mer-[2] under stirring at room temperature occurred with formation of mer-[1]. Alternative C-H activation of the CH(2) group occurred next to the pyridyl group, and formation of a C-N bond between the CH moiety and the nitrosyl ligand afforded a nitroso complex [Ru(II)(N(3))(2){N(O)CH(py)CH(2)N(C(2)H(5))C(2)H(4)py}] ([8]) in reactions of nitrosyl complexes with sodium azide in methanol, and reaction of [8] with hydrochloric acid afforded a corresponding chloronitroso complex [Ru(II)Cl(2){N(O)CH(py)CH(2)N(C(2)H(5))C(2)H(4)py}] ([9]). PMID:21517051

  15. CH Bond Activation of Hydrocarbons Mediated by Rare-Earth Metals and Actinides: Beyond σ-Bond Metathesis and 1,2-Addition

    OpenAIRE

    W. HUANG; Diaconescu, PL

    2015-01-01

    © 2015 Elsevier Inc. This review discusses C. H bond activation of hydrocarbons mediated by rare-earth metal complexes with an emphasis on type of mechanisms. The review is organized as follows: in the first part, C. H bond activations mediated by rare-earth metals and actinides following traditional reaction pathways, such as σ-bond metathesis and 1,2-addition, are summarized; in the second part, nontraditional C. H bond activation examples are discussed in detail in order to understand the ...

  16. The structure and orientation of the C-H...OC hydrogen bonding in PHB studied by polarized infrared spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Murakami, R.; Sato, H.; Dybal, Jiří; Iwata, T.; Zhang, J.; Tashiro, K.; Noda, I.; Ozaki, Y.

    Nishinomiya : Kwansei Gakuin University, 2005. s. 59. [International Symposium of Research Center for Environment Friendly Polymers /1./. 24.10.2005-25.10.2005, Nishinomiya] Institutional research plan: CEZ:AV0Z40500505 Keywords : poly(3-hydroxybutyrate) * polarized infrared spectra * hydrogen bonding Subject RIV: CD - Macromolecular Chemistry

  17. Hard three-dimensional sp2 carbon-bonded phase formed by ion beam irradiation of fullerene, a-C and polymeric a-C:H films

    International Nuclear Information System (INIS)

    The formation of new carbon amorphous phase through the ion irradiation of fullerene, a-C and polymeric a-C:H films is presented. The carbon films were subjected to N irradiation at 400 keV in the fluence range from 1013 to 3 x 1016 N cm-2. Modifications in the carbon structure, as function of the irradiation fluence, were investigated using the Rutherford backscattering spectrometry, nuclear reaction analysis, Fourier transform infrared, Raman spectroscopy, UV-VIS-NearIR spectrophotometry and nanoindentation techniques. After high fluence, the three carbon samples were transformed into very similar hard (∼14 GPa) and non-hydrogenated amorphous carbon layers with very low optical gaps (∼0.2 eV) and an unusual sp2 rich-bonded atomic network. The mechanical properties of the irradiated films correlated with the bonding topologies of this new sp2 carbon phase are analyzed in terms of the constraint-counting model. The results show that the unusual rigidity was achieved by the distortion of the sp2 carbon bond angles, giving origin to a constrained three-dimensional sp2 carbon bonded network

  18. Palladium Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Engelin, Casper Junker; Fristrup, Peter

    2011-01-01

    The atom-efficiency of one of the most widely used catalytic reactions for forging C-C bonds, the Tsuji-Trost reaction, is limited by the need of preoxidized reagents. This limitation can be overcome by utilization of the recently discovered palladium-catalyzed C-H activation, the allylic C...

  19. Synthesis and orthogonal functionalization of oxazolo[5',4':4,5]pyrano[2,3-b]pyridine by intra- and intermolecular Pd-catalyzed direct C-H bond heteroarylation.

    Science.gov (United States)

    Théveau, Laure; Schneider, Cédric; Querolle, Olivier; Meerpoel, Lieven; Levacher, Vincent; Hoarau, Christophe

    2016-04-01

    The construction and subsequent orthogonal functionalization of a hitherto unknown oxazolo[5',4':4,5]pyrano[2,3-b]pyridine are reported. A palladium-catalyzed direct C-H bond functionalization methodology was used to build the tricyclic scaffold as well as to achieve the subsequent C-H bond functionalization at the C-2 position of the oxazole unit with various (hetero)aryl iodides. Remarkably, selective C-H construction and functionalization procedures preserve the chorine atom on the pyridine moiety offering a late-stage substitution site to progress drug design. PMID:26967763

  20. Rh(iii)-catalyzed C-H activation/cyclization of oximes with alkenes for regioselective synthesis of isoquinolines.

    Science.gov (United States)

    Chen, Renjie; Qi, Jifeng; Mao, Zhenjun; Cui, Sunliang

    2016-07-14

    A Rh(iii)-catalyzed C-H activation/cyclization of oximes and alkenes for facile and regioselective access to isoquinolines has been developed. This protocol features mild reaction conditions and easily accessible starting materials, and has been applied to the concise synthesis of moxaverine. A kinetic isotope effect study was conducted and a plausible mechanism was proposed. PMID:27273816

  1. Exceptional sensitivity of metal-aryl bond energies to ortho-fluorine substituents: influence of the metal, the coordination sphere, and the spectator ligands on M-C/H-C bond energy correlations.

    Science.gov (United States)

    Clot, Eric; Mégret, Claire; Eisenstein, Odile; Perutz, Robin N

    2009-06-10

    DFT calculations are reported of the energetics of C-H oxidative addition of benzene and fluorinated benzenes, Ar(F)H (Ar(F) = C(6)F(n)H(5-n), n = 0-5) at ZrCp(2) (Cp = eta(5)-C(5)H(5)), TaCp(2)H, TaCp(2)Cl, WCp(2), ReCp(CO)(2), ReCp(CO)(PH(3)), ReCp(PH(3))(2), RhCp(PH(3)), RhCp(CO), IrCp(PH(3)), IrCp(CO), Ni(H(2)PCH(2)CH(2)PH(2)), Pt(H(2)PCH(2)CH(2)PH(2)). The change in M-C bond energy of the products fits a linear function of the number of fluorine substituents, with different coefficients corresponding to ortho-, meta-, and para-fluorine. The values of the ortho-coefficient range from 20 to 32 kJ mol(-1), greatly exceeding the values for the meta- and para-coefficients (2.0-4.5 kJ mol(-1)). Similarly, the H-C bond energies of Ar(F)H yield ortho- and para-coefficients of 10.4 and 3.4 kJ mol(-1), respectively, and a negligible meta-coefficient. These results indicate a large increase in the M-C bond energy with ortho-fluorine substitution on the aryl ring. Plots of D(M-C) vs D(H-C) yield slopes R(M-C/H-C) that vary from 1.93 to 3.05 with metal fragment, all in excess of values of 1.1-1.3 reported with other hydrocarbyl groups. Replacement of PH(3) by CO decreases R(M-C/H-C) significantly. For a given ligand set and metals in the same group of the periodic table, the value of R(M-C/H-C) does not increase with the strength of the M-C bond. Calculations of the charge on the aryl ring show that variations in ionicity of the M-C bonds correlate with variations in M-C bond energy. This strengthening of metal-aryl bonds accounts for numerous experimental results that indicate a preference for ortho-fluorine substituents. PMID:19453181

  2. Rhodium-Catalyzed Intramolecular C-H Silylation by Silacyclobutanes.

    Science.gov (United States)

    Zhang, Qing-Wei; An, Kun; Liu, Li-Chuan; Guo, Shuangxi; Jiang, Chenran; Guo, Huifang; He, Wei

    2016-05-17

    Silacyclobutane was discovered to be an efficient C-H bond silylation reagent. Under the catalysis of Rh(I) /TMS-segphos, silacyclobutane undergoes sequential C-Si/C-H bond activations, affording a series of π-conjugated siloles in high yields and regioselectivities. The catalytic cycle was proposed to involve a rarely documented endocyclic β-hydride elimination of five-membered metallacycles, which after reductive elimination gave rise to a Si-Rh(I) species that is capable of C-H activation. PMID:27073004

  3. Contrasting electronic requirements for C-H binding and C-H activation in d(6) half-sandwich complexes of rhenium and tungsten.

    Science.gov (United States)

    Thenraj, Murugesan; Samuelson, Ashoka G

    2015-09-15

    A computational study of the interaction half-sandwich metal fragments (metal = Re/W, electron count = d(6)), containing linear nitrosyl (NO(+) ), carbon monoxide (CO), trifluorophosphine (PF3 ), N-heterocyclic carbene (NHC) ligands with alkanes are conducted using density functional theory employing the hybrid meta-GGA functional (M06). Electron deficiency on the metal increases with the ligand in the order NHC < CO < PF3 < NO(+). Electron-withdrawing ligands like NO(+) lead to more stable alkane complexes than NHC, a strong electron donor. Energy decomposition analysis shows that stabilization is due to orbital interaction involving charge transfer from the alkane to the metal. Reactivity and dynamics of the alkane fragment are facilitated by electron donors on the metal. These results match most of the experimental results known for CO and PF3 complexes. The study suggests activation of alkane in metal complexes to be facile with strong donor ligands like NHC. PMID:26174521

  4. C-H activation reactions by yttrium and lutetium hydride complexes : H/D exchange vs metalation of hydrocarbons. Importance of the hybridization state at the α carbon

    NARCIS (Netherlands)

    Deelman, Berth-Jan; Teuben, Jan H.; Macgregor, Stuart A.; Eisenstein, Odile

    1995-01-01

    Extended Hückel (EHT) calculations have been used to discuss the two alternative σ-bond C-H metathesis reactions which occur with organo-lanthanide (Ln = Y, Lu) compounds. The two reactions lead either to H/H (H/D) exchange or to metalation and have been modelled by studying the interaction of a Cp2

  5. Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Hitoshi; Thalji, Reema; Bergman, Robert; Ellman, Jonathan

    2008-05-22

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe){sub 2}]{sub 2} and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

  6. C. H. McCloy Lecture: Fifty Years of Advancements in Fitness and Activity Research

    Science.gov (United States)

    Corbin, Charles B.

    2012-01-01

    Over the past 50 years progress in fitness and activity research has been influenced by social events, technical innovations, and changes in the field of physical education and kinesiology. The conventional wisdom of the 1950s yielded to a new wisdom based on research evidence. The author's research, as well as the research of others, from 1960 to…

  7. Anti-thrombotic activity and chemical characterization of steroidal saponins from Dioscorea zingiberensis C.H. Wright.

    Science.gov (United States)

    Li, Hua; Huang, Wen; Wen, Yanqing; Gong, Guohua; Zhao, Qingbing; Yu, Gang

    2010-12-01

    Steroidal saponins have long attracted scientific attention, due to their structural diversity and significant biological activities. Total steroidal saponins (TSS) extracted from the rhizomes of Dioscorea zingiberensis C.H. Wright (DZW) constitute an effective treatment for cardiovascular disease. However, the active constituents contained in DZW rhizomes and their pharmacological properties are not fully understood. The aim of this work is to determine and quantify the active constituents in DZW rhizomes using fingerprint technique, and evaluate its anti-thrombotic activity using inferior vena cava ligation thrombosis rat model and pulmonary thrombosis mice model after being gavaged with TSS for 1 or 2weeks. In the study, a chemical fingerprint method was firstly established and validated to quantify and standardize TSS from DZW rhizomes including parvifloside, protodeltonin, protodioscin, protogracillin, zingiberensis saponin, deltonin, dioscin and trillin. TSS extracted from DZW rhizomes were showed to have the inhibitions on platelet aggregation (PAG) and thrombosis, and prolong activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) in a dose-dependent manner in rats. TSS also prolonged the bleeding time and clotting time in a dose-dependent manner in mice. The results indicate that TSS could inhibit thrombosis by both improving the anticoagulation activity and inhibiting PAG action, suggesting that TSS from DZW rhizomes have the potential to reduce the risk of cardiovascular diseases by anti-thrombotic action. PMID:20659537

  8. Silicon carbide wafer bonding by modified surface activated bonding method

    Science.gov (United States)

    Suga, Tadatomo; Mu, Fengwen; Fujino, Masahisa; Takahashi, Yoshikazu; Nakazawa, Haruo; Iguchi, Kenichi

    2015-03-01

    4H-SiC wafer bonding has been achieved by the modified surface activated bonding (SAB) method without any chemical-clean treatment and high temperature annealing. Strong bonding between the SiC wafers with tensile strength greater than 32 MPa was demonstrated at room temperature under 5 kN force for 300 s. Almost the entire wafer has been bonded very well except a small peripheral region and few voids. The interface structure was analyzed to verify the bonding mechanism. It was found an amorphous layer existed as an intermediate layer at the interface. After annealing at 1273 K in vacuum for 1 h, the bonding tensile strength was still higher than 32 MPa. The interface changes after annealing were also studied. The results show that the thickness of the amorphous layer was reduced to half after annealing.

  9. A study on aromatic C-H⋯X (X = N, O) hydrogen bonds in 1,2,4,5-tetrafluorobenzene clusters using infrared spectroscopy and ab initio calculations

    Science.gov (United States)

    Venkatesan, V.; Fujii, A.; Mikami, N.

    2005-06-01

    The (1:1) clusters of 1,2,4,5-tetrafluorobenzene (TFB) with CH 3CN, CH 3OCH 3, and NH 3 were studied both experimentally and computationally. Using fluorescence-detected infrared (FDIR) spectroscopy, the aromatic C-H⋯X (X = N, O) hydrogen bond formation in the clusters was directly evidenced by a low-frequency shift and intensity enhancement of the aromatic C-H stretching vibration in the TFB moiety. The molecular structures, stabilization energies, and vibrational frequencies of the clusters were computed at the MP2/6-31+G* level. The observed low-frequency shifts of the aromatic C-H stretch in the clusters correlate with the proton affinities of the acceptor molecules.

  10. Enantioselective S - H and C - H insertions with optically active Rh(II) and Cu(II) catalysts. Asymmetric catalysis, 58

    International Nuclear Information System (INIS)

    The substrates for the S - H insertion reaction were azibutanone 2 and thiophenol 3. Methyl 2-diazo-3-oxo-heptane-carboxylate 26 was used as the substrate in an intramolecular C - H insertion. Both reactions were carried out enantioselectively in the presence of optically active rhodium(II) and copper(II) catalysts. For the S - H insertion optical inductions up to 13,8 %ee and for the C - H insertion up to 14 %ee were achieved. (Authors)

  11. Thermally activated solvent bonding of polymers

    OpenAIRE

    Ng, S H; Tjeung, R. T.; Z. F. Wang; Lu, A. C. W.; Rodriguez, I.; de Rooij, Nicolaas F.

    2010-01-01

    We present a thermally activated solvent bonding technique for the formation of embedded microstructures in polymer. It is based on the temperature dependent solubility of polymer in a liquid that is not a solvent at room temperature. With thermal activation, the liquid is transformed into a solvent of the polymer, creating a bonding capability through segmental or chain interdiffusion at the bonding interface. The technique has advantages over the more commonly used thermal bonding due to it...

  12. Imidazolium-Based Dicationic Cyclophanes. Solid-State Aggregates with unconventional (C?H)+???Cl? Hydrogen Bonding Revealed by X-Ray Diffraction

    OpenAIRE

    Alcalde, Ermitas

    2007-01-01

    Abstract The first single-crystal X-ray crystallographic diffraction analysis of a dicationic heterophane showed a non-classic (CH)+???Cl hydrogen bond between the imidazolium rings and halide anions and the formation of unconventional charged assisted hydrogen bonds, which were the non-covalent forces driving the anion interactions shown by the dications 4?2X. Here we report the halide-templated controlled synthesis and chemical response in basic media of 4?2X. The...

  13. Rhodium(III) Catalyzed Carboamination of Alkenes Triggered by C-H Activation of N-Phenoxyacetamides under Redox-Neutral Conditions.

    Science.gov (United States)

    Hu, Zhiyong; Tong, Xiaofeng; Liu, Guixia

    2016-04-01

    N-Alkoxyacrylamides are coupled with N-phenoxyacetamides by Rh(III) catalysis through C-H functionalization and amido group transfer under external oxidant-free conditions, which affords acyclic alkene carboamination products in an atom-economical way. Mechanistic insight into this transformation indicates the amide group in N-alkoxyacrylamide plays a critical role in this C-C/C-N bond formation reaction. This methodology provides a highly efficient way to construct o-tyrosine derivatives under mild conditions. PMID:27002932

  14. C-H activation reactions by yttrium and lutetium hydride complexes: H/D exchange vs metalation of hydrocarbons. Importance of the hybridization state at the α carbon

    OpenAIRE

    Deelman, Berth-Jan; Teuben, Jan H.; Macgregor, Stuart A.; Eisenstein, Odile

    1995-01-01

    Extended Hückel (EHT) calculations have been used to discuss the two alternative σ-bond C-H metathesis reactions which occur with organo-lanthanide (Ln = Y, Lu) compounds. The two reactions lead either to H/H (H/D) exchange or to metalation and have been modelled by studying the interaction of a Cp2Ln+ fragment with [H-R-H]- and [R-H-H]- respectively. It is shown that the metallic fragment interacts in a similar way with the two organic fragments and that the preference for one of the two pat...

  15. Iridium-catalysed ortho-H/D and -H/T exchange under basic conditions: C-H activation of unprotected tetrazoles.

    Science.gov (United States)

    Kerr, William J; Lindsay, David M; Reid, Marc; Atzrodt, Jens; Derdau, Volker; Rojahn, Patrick; Weck, Remo

    2016-05-10

    The first examples of selective ortho-directed C-H activation with unprotected 2-aryltetrazoles are described. A new base-assisted protocol for iridium(i) hydrogen isotope exchange catalysis allows access to ortho-deuterated and tritiated tetrazoles, including the tetrazole-containing pharmaceutical, Valsartan. Preliminary mechanistic studies are also presented. PMID:27115235

  16. Air/Water-Stable Tridentate NHC-PdII Complex; Catalytic C-H Activation of Hydrocarbons via H/D Exchange Process in D2O

    OpenAIRE

    Lee, Joo Ho; Yoo, Kyung Soo; Park, Chan Pil; Olsen, Janet M.; Sakaguchi, Satoshi; Surya Prakash, G. K.; Mathew, Thomas; Jung, Kyung Woon

    2009-01-01

    While developing novel catalysts for carbon-carbon or carbon-heteroatom coupling (N, O, or F), we were able to introduce tridentate NHC-amidate-alkoxide palladium(II) complexes. In aqueous solution, these NHC-Pd(II) complexes showed high ability for C-H activation of various hydrocarbons (cyclohexane, cyclopentane, dimethyl ether, THF, acetone, and toluene) under mild conditions.

  17. Functionalized alkynyl-chlorogermanes: hydrometallation, Ge-Cl bond activation, Ge-H bond formation and chlorine-tert-butyl exchange via a transient germyl cation.

    Science.gov (United States)

    Honacker, Christian; Qu, Zheng-Wang; Tannert, Jens; Layh, Marcus; Hepp, Alexander; Grimme, Stefan; Uhl, Werner

    2016-04-14

    Treatment of alkynyl-arylchlorogermanes ArylnGe(Cl)(C[triple bond, length as m-dash]C-(t)Bu)3-n (n = 1, 2) with HM(t)Bu2 (M = Al, Ga) yielded mixed Al or Ga alkenyl-alkynylchlorogermanes via hydrometallation reactions. Intramolecular interactions between the Lewis-basic Cl atoms and the Lewis-acidic Al or Ga atoms afforded MCGeCl heterocycles. The endocyclic M-Cl distances were significantly lengthened compared to the starting compounds and indicated Ge-Cl bond activation. Dual hydrometallation succeeded only with HGa(t)Bu2. One Ga atom of the product was involved in a Ga-Cl bond, while the second one had an interaction to a C-H bond of a phenyl group. In two cases treatment of chlorogermanes with two equivalents of HAl(t)Bu2 resulted in hydroalumination of one alkynyl group and formation of unprecedented Ge-H functionalized germanes, Aryl-Ge(H)(C[triple bond, length as m-dash]C-(t)Bu)[C(Al(t)Bu2)[double bond, length as m-dash]C(H)-(t)Bu] (Aryl = mesityl, triisopropylphenyl). The Al atoms of these compounds interacted with the α-C atoms of the alkynyl groups. Ph(Cl)Ge(C[triple bond, length as m-dash]C-(t)Bu)[C(Al(t)Bu2}[double bond, length as m-dash]C(H)-(t)Bu] reacted in an unusual Cl/(t)Bu exchange to yield the tert-butylgermane Ph((t)Bu)Ge(C[triple bond, length as m-dash]C-(t)Bu)[C{Al((t)Bu)(Cl)}[double bond, length as m-dash]C(H)-(t)Bu]. Quantum chemical calculations suggested the formation of a germyl cation as a transient intermediate. PMID:26610394

  18. Manganese Catalyzed C-H Halogenation.

    Science.gov (United States)

    Liu, Wei; Groves, John T

    2015-06-16

    led to the discovery of the first Mn-catalyzed direct aliphatic C-H fluorination reactions utilizing simple, nucleophilic fluoride salts. Mechanistic studies and DFT calculations have revealed a trans-difluoromanganese(IV) species as the key fluorine transfer intermediate. In addition to catalyzing normal (19)F-fluorination reactions, manganese salen complexes were found to enable the incorporation of radioactive (18)F fluorine via C-H activation. This advance represented the first direct Csp(3)-H bond (18)F labeling with no-carrier-added [(18)F]fluoride and facilitated the late-stage labeling of drug molecules for PET imaging. Given the high reactivity and enzymatic-like selectively of metalloporphyrins, we envision that this new Heteroatom-Rebound Catalysis (HRC) strategy will find widespread application in the C-H functionalization arena and serve as an effective tool for forming new carbon-heteroatom bonds at otherwise inaccessible sites in target molecules. PMID:26042637

  19. Water as a green solvent for efficient synthesis of isocoumarins through microwave-accelerated and Rh/Cu-catalyzed C-H/O-H bond functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qiu; Yan, Yunnan; Wang, Xiaowei; Gong, Binwei; Tang, Xiaobo; Shi, JingJing; Xu, H. Eric; Yi, Wei [Shenyang; (Gannan); (Van Andel); (UST - China); (Chinese Aca. Sci.)

    2014-08-14

    Green chemistry that uses water as a solvent has recently received great attention in organic synthesis. Here we report an efficient synthesis of biologically important isocoumarins through direct cleavage of C–H/O–H bonds by microwave-accelerated and Rh/Cu-catalyzed oxidative annulation of various substituted benzoic acids, where water is used as the only solvent in the reactions. The remarkable features of this “green” methodology include high product yields, wide tolerance of various functional groups as substrates, and excellent region-/site-specificities, thus rendering this methodology a highly versatile and eco-friendly alternative to the existing methods for synthesizing isocoumarins and other biologically important derivatives such as isoquinolones.

  20. Intermolecular C-H activation with an Ir-METAMORPhos piano-stool complex--multiple reaction steps at a reactive ligand.

    Science.gov (United States)

    Oldenhof, S; Lutz, M; van der Vlugt, J I; Reek, J N H

    2015-10-21

    Substrate activation by means of a reactive ligand is a topic of much interest. Herein we describe a stoichiometric anti-Markovnikov C-N bond formation involving ligand reactivity in multiple steps along the reaction coordinate, including ligand assisted substrate (de)protonation and C-N bond formation, as illustrated by a combined experimental, spectroscopic and computational study. This affords a highly unusual four-membered iridacycle bearing an exo-cyclic C=C double bond. PMID:26329519

  1. Intermolecular insertion of an N,N-heterocyclic carbene into a nonacidic C-H bond: Kinetics, mechanism and catalysis by (K-HMDS)2 (HMDS = Hexamethyldisilazide).

    Science.gov (United States)

    Lloyd-Jones, Guy C; Alder, Roger W; Owen-Smith, Gareth J J

    2006-07-01

    The reaction of 2-[13C]-1-ethyl-3-isopropyl-3,4,5,6-tetrahydropyrimidin-1-ium hexafluorophosphate ([13C1]-1-PF6) with a slight excess (1.03 equiv) of dimeric potassium hexamethyldisilazide ("(K-HMDS)2") in toluene generates 2-[13C]-3-ethyl-1-isopropyl-3,4,5,6-tetrahydropyrimid-2-ylidene ([13C1]-2). The hindered meta-stable N,N-heterocyclic carbene [13C1]-2 thus generated undergoes a slow but quantitative reaction with toluene (the solvent) to generate the aminal 2-[13C]-2-benzyl-3-ethyl-1-isopropylhexahydropyrimidine ([13C1]-14) through formal C-H insertion of C2 (the "carbene carbon") at the toluene methyl group. Despite a significant pKa mismatch (Delta pKa 1+ and toluene estimated to be ca. 16 in DMSO) the reaction shows all the characteristics of a deprotonation mechanism, the reaction rate being strongly dependent on the toluene para substituent (rho = 4.8(+/-0.3)), and displaying substantial and rate-limiting primary (k(H)/k(D) = 4.2(+/-0.6)) and secondary (k(H)/k(D) = 1.18(+/-0.08)) kinetic isotope effects on the deuteration of the toluene methyl group. The reaction is catalysed by K-HMDS, but proceeds without cross over between toluene methyl protons and does not involve an HMDS anion acting as base to generate a benzyl anion. Detailed analysis of the reaction kinetics/kinetic isotope effects demonstrates that a pseudo-first-order decay in 2 arises from a first-order dependence on 2, a first-order dependence on toluene (in large excess) and, in the catalytic manifold, a complex noninteger dependence on the K-HMDS dimer. The rate is not satisfactorily predicted by equations based on the Brønsted salt-effect catalysis law. However, the rate can be satisfactorily predicted by a mole-fraction-weighted net rate constant: -d[2]/dt = ({x2 k(uncat)} + {(1-x2) k(cat)})[2]1[toluene]1, in which x2 is determined by a standard bimolecular complexation equilibrium term. The association constant (Ka) for rapid equilibrium-complexation of 2 with (K-HMDS)2 to form [2(K

  2. Bipodal surface organometallic complexes with surface N-donor ligands and application to the catalytic cleavage of C-H and C-C bonds in n -Butane

    KAUST Repository

    Bendjeriou-Sedjerari, Anissa

    2013-11-27

    We present a new generation of "true vicinal" functions well-distributed on the inner surface of SBA15: [(Sî - Si-NH 2)(≡Si-OH)] (1) and [(≡Si-NH2)2] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [(≡Si-NH-)(≡Si-O-)]Zr(CH2tBu) 2 (3) and [(≡Si-NH-)2]Zr(CH2tBu) 2 (4) have been obtained by reaction with Zr(CH2tBu) 4. The surfaces were characterized with 2D multiple-quantum 1H-1H NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH2tBu)4 reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [(≡Si-NH-)2]Zr(H) 2 (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [(≡Si-NH-)2(≡Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an 1H NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [(≡Si-Nî)(≡Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [(≡Si-NH-)(≡Si-O-)] Zr(H)2 (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [(≡Si-NH-)(≡Si-O-)2]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N]. © 2013 American Chemical Society.

  3. Seven organic salts assembled from hydrogen-bonds of N-H⋯O, O-H⋯O, and C-H⋯O between acidic compounds and bis(benzimidazole)

    Science.gov (United States)

    Jin, Shouwen; Liu, Hui; Gao, Xin Jun; Lin, Zhanghui; Chen, Guqing; Wang, Daqi

    2014-10-01

    Seven crystalline organic acid-base adducts derived from 1,4-bis(benzimidazol-2-yl)butane/1,2-bis(2-benzimidazolyl)-1,2-ethanediol and acidic components (picric acid, 2-hydroxy-5-(phenyldiazenyl)benzoic acid, 5-sulfosalicylic acid, oxalic acid, and 1,5-naphthalenedisulfonic acid) were prepared and characterized by the single crystal X-ray diffraction analysis, IR, mp, and elemental analysis. All of the seven compounds are organic salts involving proton transfer from the acidic components to the bis(benzimidazole). For the salt 3, although a competing carboxyl group is present, it has been observed that only the proton at the -SO3H group is deprotonized rather than the H at the COOH. While in the salt 7, both COOH and SO3H were ionized to exhibit a valence number of -2. For 4, the oxalic acid existed as unionized molecule, monoanion, and dianion simultaneously in one compound. All supramolecular architectures of the organic salts 1-7 involve extensive intermolecular N-H⋯O, O-H⋯O, and C-H⋯O hydrogen bonds as well as other noncovalent interactions. Since the potentially hydrogen bonding phenol group is present in the ortho position to the carboxyl group in 2, 3, and 7, it forms the more facile intramolecular O-H⋯O hydrogen bonding. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These weak interactions combined, all the complexes displayed 3D framework structure.

  4. Solvent-Controlled, Tunable β-OAc and β-H Elimination in Rh(III)-Catalyzed Allyl Acetate and Aryl Amide Coupling via C-H Activation.

    Science.gov (United States)

    Dai, Huimin; Yu, Chao; Wang, Zihao; Yan, Hong; Lu, Changsheng

    2016-07-15

    The Heck reaction between arenes and allyl acetate has led to cinnamyl derivatives and allyl products depending on the regioselectivity of β-elimination. The regioselectivity can be controlled by the solvent in the Rh(III)-catalyzed arene-allyl acetate coupling via C-H activation: (1) in THF, cinnamyl derivatives via β-H elimination were generated; (2) in MeOH, allyl products via β-OAc elimination were produced. Both routes have advantages such as excellent γ-selectivity toward allyl acetate, good to excellent yields, and broad substrate scope. PMID:27351917

  5. Radical Beckmann Rearrangement and Its Application in the Formal Total Synthesis of Antimalarial Natural Product Isocryptolepine via C-H Activation.

    Science.gov (United States)

    Mahajan, Pankaj S; Humne, Vivek T; Tanpure, Subhash D; Mhaske, Santosh B

    2016-07-15

    The Beckmann rearrangement of ketoximes, mediated by ammonium persulfate-dimethyl sulfoxide as a reagent, has been achieved under neutral conditions. Based on the radical trapping and (18)O-labeling experiments, the transformation follows a mechanism involving a radical pathway. The scope and generality of the developed protocol has been demonstrated by 19 examples. The developed protocol and Pd-catalyzed intramolecular double C-H activation were used as key steps in the formal total synthesis of antimalarial natural product isocryptolepine. PMID:27377995

  6. Rhodium (II) carbene C-H insertion in water and catalyst reuse

    International Nuclear Information System (INIS)

    A five-session laboratory experiment is described for the synthesis of a beta-lactam via Rh(II) catalysed intramolecular C-H insertion of a alpha-diazo-alpha-ethoxycarbonyl acetamide. The metallo-carbene, responsible for the C-H bond activation, was generated from the diazo substrate and the catalyst Rh2(OAc)4. The high stability and solubility of the catalyst and the exclusive C-H insertion of the Rh-carbene allows the synthesis of this important heterocycle in water and the catalyst reutilization. (author)

  7. 76 FR 12364 - Agency Information Collection Activities: Bonded Warehouse Regulations

    Science.gov (United States)

    2011-03-07

    ... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Bonded Warehouse... Bonded Warehouse Regulations. This request for comment is being made pursuant to the Paperwork Reduction... concerning the following information collection: Title: Bonded Warehouse Regulations. OMB Number:...

  8. C-H ACTIVATION REACTIONS BY YTTRIUM AND LUTETIUM HYDRIDE COMPLEXES - H/D EXCHANGE VS METALATION OF HYDROCARBONS - IMPORTANCE OF THE HYBRIDIZATION STATE AT THE ALPHA-CARBON

    NARCIS (Netherlands)

    DEELMAN, BJ; TEUBEN, JH; MACGREGOR, SA; EISENSTEN, O

    1995-01-01

    Extended Huckel (EHT) calculations have been used to discuss the two alternative sigma-bond C-H metathesis reactions which occur with organo-lanthanide (Ln = Y, Lu) compounds. The two reactions lead either to H/H (H/D) exchange or to metalation and have been modelled by studying the interaction of a

  9. Rhodium(III)-Catalyzed C-H Activation/Annulation with Vinyl Esters as an Acetylene Equivalent

    OpenAIRE

    Webb, NJ; Marsden, SP; Raw, SA

    2014-01-01

    The behavior of electron-rich alkenes in rhodium-catalyzed C–H activation/annulation reactions is investigated. Vinyl acetate emerges as a convenient acetylene equivalent, facilitating the synthesis of sixteen 3,4-unsubstituted isoquinolones, as well as select heteroaryl-fused pyridones. The complementary regiochemical preferences of enol ethers versus enol esters/enamides is discussed

  10. 2008 C. H. McCloy Lecture: Social Psychology and Physical Activity--Back to the Future

    Science.gov (United States)

    Gill, Diane L.

    2009-01-01

    In the early 1970s, both my academic career and the psychology subdiscipline within kinesiology began as "social psychology and physical activity." Since then, sport and exercise psychology research has shifted away from the social to a narrower bio-psycho-(no social) approach, and professional practice has focused on the elite rather than the…

  11. Initial Stages in the Rhodium(III)-Catalyzed C-H Bond Activation of Primary Alcohols in Aqueous Solution

    DEFF Research Database (Denmark)

    Eriksen, J.; Monsted, L.; Monsted, O.;

    2010-01-01

    ,4,8,11-tetraazacyclotetradecane) cation. The hydride complex is stable for extended periods of time in acidic solution in the absence of oxidants. In basic solutions a series of base-catalyzed reactions take place to yield ultimately the same mixture of [Rh(cycb)(OH)(2)](+) isomers as produced by base hydrolysis of the trans...

  12. Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

    Science.gov (United States)

    Gulzar, Naeem; Klussmann, Martin

    2014-01-01

    The direct functionalization of C-H bonds is an important and long standing goal in organic chemistry. Such transformations can be very powerful in order to streamline synthesis by saving steps, time and material compared to conventional methods that require the introduction and removal of activating or directing groups. Therefore, the functionalization of C-H bonds is also attractive for green chemistry. Under oxidative conditions, two C-H bonds or one C-H and one heteroatom-H bond can be transformed to C-C and C-heteroatom bonds, respectively. Often these oxidative coupling reactions require synthetic oxidants, expensive catalysts or high temperatures. Here, we describe a two-step procedure to functionalize indole derivatives, more specifically tetrahydrocarbazoles, by C-H amination using only elemental oxygen as oxidant. The reaction uses the principle of C-H functionalization via Intermediate PeroxideS (CHIPS). In the first step, a hydroperoxide is generated oxidatively using visible light, a photosensitizer and elemental oxygen. In the second step, the N-nucleophile, an aniline, is introduced by Brønsted-acid catalyzed activation of the hydroperoxide leaving group. The products of the first and second step often precipitate and can be conveniently filtered off. The synthesis of a biologically active compound is shown. PMID:24998636

  13. Réactions de cycloisomérisation d'ènynes en présence de complexes d'or, de platine et d'ions halogéniums - Approche combinatoire en présence de complexes de platine. Réactions d'acyloxylation par activation C-H d'aromatiques en présence de complexes d'or.

    OpenAIRE

    Pradal, Alexandre

    2012-01-01

    This manuscript concerns the development of electrophilic systems, involving gold and platinum π-Lewis acids or halogenium ions and their involvement in C-C triple bond (stereoselective enyne cycloisomerization reactions in the presence or in the absence of an external nucleophile and halocarbocyclization reactions) and C-H bond (acyloxylation reactions of hindered arenes) activation processes. The use of a catalytic system which consists in a binuclear gold (I) complex possessing the diphosp...

  14. 78 FR 75576 - Agency Information Collection Activities: Importation Bond Structure

    Science.gov (United States)

    2013-12-12

    ... regulation to post a bond in order to secure a Customs transaction must submit the bond on CBP Form 301 which... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Importation Bond... Importation Bond Structure. This request for comment is being made pursuant to the Paperwork Reduction Act...

  15. Characterization of two alkyl hydroperoxide reductase C homologs alkyl hydroperoxide reductase C_H1 and alkyl hydroperoxide reductase C_H2 in Bacillus subtilis

    Institute of Scientific and Technical Information of China (English)

    Mee-Kyung; Cha; Yoo-Jeen; Bae; Kyu-Jeong; Kim; Byung-Joon; Park; Il-Han; Kim

    2015-01-01

    AIM: To identify alkyl hydroperoxide reductase subunit C(AhpC) homologs in Bacillus subtilis(B. subtilis) and to characterize their structural and biochemical properties. AhpC is responsible for the detoxification of reactive oxygen species in bacteria.METHODS: Two AhpC homologs(AhpC_H1 and AhpC_H2) were identified by searching the B. subtilis database; these were then cloned and expressed in Escherichia coli. AhpC mutants carrying substitutions of catalytically important Cys residues(C37S, C47 S, C166 S, C37/47 S, C37/166 S, C47/166 S, and C37/47/166 S for AhpC_H1; C52 S, C169 S, and C52/169 S for AhpC_H2) were obtained by site-directed mutagenesis and purified, and their structure-function relationship was analyzed. The B. subtilis ahp C genes were disrupted by the short flanking homology method, and the phenotypes of the resulting AhpC-deficient bacteria were examined.RESULTS: Comparative characterization of AhpC homologs indicates that AhpC_H1 contains an extra C37, which forms a disulfide bond with the peroxidatic C47, and behaves like an atypical 2-Cys AhpC, while AhpC_H2 functions like a typical 2-Cys AhpC. Tryptic digestion analysis demonstrated the presence of intramolecular Cys37-Cys47 linkage, which could be reduced by thioredoxin, resulting in the association of the dimer into higher-molecular-mass complexes. Peroxidase activity analysis of Cys→Ser mutants indicated that three Cys residues were involved in the catalysis. AhpC_H1 was resistant to inactivation by peroxide substrates, but had lower activity at physiological H2O2 concentrations compared to AhpC_H2, suggesting that in B. subtilis, the enzymes may be physiologically functional at different substrate concentrations. The exposure to organic peroxides induced AhpC_H1 expression, while AhpC_H1-deficient mutants exhibited growth retardation in the stationary phase, suggesting the role of AhpC_H1 as an antioxidant scavenger of lipid hydroperoxides and a stress-response factor in B. subtilis

  16. Development of a supramolecular ensemble of an AIEE active hexaphenylbenzene derivative and Ag@Cu2O core-shell NPs: an efficient photocatalytic system for C-H activation.

    Science.gov (United States)

    Chopra, Radhika; Kumar, Manoj; Bhalla, Vandana

    2016-08-01

    A supramolecular ensemble having Ag@Cu2O core-shell nanoparticles stabilized by aggregates of a hexaphenylbenzene derivative has been developed which exhibits excellent photocatalytic efficiency in reactions involving preparation of imidazole and benzimidazole derivatives via C-H activation. PMID:27464360

  17. Interfiber bonding and fiber segment activation in paper

    OpenAIRE

    Hannu Paulapuro; Anna K. Vainio

    2007-01-01

    Bonding and activation in paper were studied with the help of laboratory test sheets and common paper strength tests. Different papermaking furnishes and raw material treatments were used to examine the effects they have on bonding and activation. Furthermore, various boundary conditions during drying were included to single out the influence of bonding and activation on paper properties. It was found that bonding is clearly increased by beating of kraft pulp, starch addition, and thermomecha...

  18. Mechanochemically Activated Oxidative Coupling of Indoles with Acrylates through C-H Activation: Synthesis of 3-Vinylindoles and β,β-Diindolyl Propionates and Study of the Mechanism.

    Science.gov (United States)

    Jia, Kan-Yan; Yu, Jing-Bo; Jiang, Zhi-Jiang; Su, Wei-Ke

    2016-07-15

    Construction of 3-vinylindoles (3) and β,β-diindolyl propionates (4) through solvent-free C-H functionalization has been explored under high-speed ball-milling conditions. The reaction selectivity is influenced by the catalyst dramatically: Pd(OAc)2 provides 3 in moderate to good yields, whereas PdX2 (X = Cl, I) affords 4 as the major products. The reaction mechanism has been further studied by using electrospray ionization mass spectrometry, implicating the dimeric palladium complex A as the key intermediate in an explanation of the selectivity. PMID:27328874

  19. A meta-selective C-H borylation directed by a secondary interaction between ligand and substrate

    Science.gov (United States)

    Kuninobu, Yoichiro; Ida, Haruka; Nishi, Mitsumi; Kanai, Motomu

    2015-09-01

    Regioselective C-H bond transformations are potentially the most efficient method for the synthesis of organic molecules. However, the presence of many C-H bonds in organic molecules and the high activation barrier for these reactions make these transformations difficult. Directing groups in the reaction substrate are often used to control regioselectivity, which has been especially successful for the ortho-selective functionalization of aromatic substrates. Here, we describe an iridium-catalysed meta-selective C-H borylation of aromatic compounds using a newly designed catalytic system. The bipyridine-derived ligand that binds iridium contains a pendant urea moiety. A secondary interaction between this urea and a hydrogen-bond acceptor in the substrate places the iridium in close proximity to the meta-C-H bond and thus controls the regioselectivity. 1H NMR studies and control experiments support the participation of hydrogen bonds in inducing regioselectivity. Reversible direction of the catalyst through hydrogen bonds is a versatile concept for regioselective C-H transformations.

  20. Ultrafast studies of organometallic photochemistry: The mechanism of carbon-hydrogen bond activation in solution

    Energy Technology Data Exchange (ETDEWEB)

    Bromberg, S.E.

    1998-05-01

    When certain organometallic compounds are photoexcited in room temperature alkane solution, they are able to break or activate the C-H bonds of the solvent. Understanding this potentially practical reaction requires a detailed knowledge of the entire reaction mechanism. Because of the dynamic nature of chemical reactions, time-resolved spectroscopy is commonly employed to follow the important events that take place as reactants are converted to products. For the organometallic reactions examined here, the electronic/structural characteristics of the chemical systems along with the time scales for the key steps in the reaction make ultrafast UV/Vis and IR spectroscopy along with nanosecond Step-Scan FTIR spectroscopy the ideal techniques to use for this study. An initial study of the photophysics of (non-activating) model metal carbonyls centering on the photodissociation of M(CO){sub 6} (M = Cr, W, Mo) was carried out in alkane solutions using ultrafast IR spectroscopy. Next, picosecond UV/vis studies of the C-H bond activation reaction of Cp{sup *}M(CO){sub 2} (M = Rh, Ir), conducted in room temperature alkane solution, are described in an effort to investigate the origin of the low quantum yield for bond cleavage ({approximately}1%). To monitor the chemistry that takes place in the reaction after CO is lost, a system with higher quantum yield is required. The reaction of Tp{sup *}Rh(CO){sub 2} (Tp{sup *} = HB-Pz{sub 3}{sup *}, Pz{sup *} = 3,5-dimethylpyrazolyl) in alkanes has a quantum yield of {approximately}30%, making time resolved spectroscopic measurements possible. From ultrafast IR experiments, two subsequently formed intermediates were observed. The nature of these intermediates are discussed and the first comprehensive reaction mechanism for a photochemical C-H activating organometallic complex is presented.

  1. Nickel-Catalyzed Aromatic C-H Functionalization.

    Science.gov (United States)

    Yamaguchi, Junichiro; Muto, Kei; Itami, Kenichiro

    2016-08-01

    Catalytic C-H functionalization using transition metals has received significant interest from organic chemists because it provides a new strategy to construct carbon-carbon bonds and carbon-heteroatom bonds in highly functionalized, complex molecules without pre-functionalization. Recently, inexpensive catalysts based on transition metals such as copper, iron, cobalt, and nickel have seen more use in the laboratory. This review describes recent progress in nickel-catalyzed aromatic C-H functionalization reactions classified by reaction types and reaction partners. Furthermore, some reaction mechanisms are described and cutting-edge syntheses of natural products and pharmaceuticals using nickel-catalyzed aromatic C-H functionalization are presented. PMID:27573407

  2. p-tert-Butylcalix[4]arene complexes of molybdenum and tungsten: reactivity of the calixarene methylene C-H bond and the facile migration of the metal around the phenolic rim of the calixarene.

    Science.gov (United States)

    Buccella, Daniela; Parkin, Gerard

    2006-12-20

    p-tert-Butylcalix[4]arene, [CalixBut(OH)4], reacts with Mo(PMe3)6 and W(PMe3)4(eta2-CH2PMe2)H to yield compounds of composition {[CalixBut(OH)2(O)2]M(PMe3)3H2} which exhibit unprecedented use of a C-H bond of a calixarene methylene group as a binding functionality in the form of agostic and alkyl hydride derivatives. Thus, X-ray diffraction studies demonstrate that, in the solid state, the molybdenum complex [CalixBut(OH)2(O)2]Mo(PMe3)3H2 exists as an agostic derivative with a Mo...H-C interaction, whereas the tungsten complex exists as a metallated trihydride [Calix-HBut(OH)2(O)2]W(PMe3)3H3. Solution 1H NMR spectroscopic studies, however, provide evidence that [Calix-HBut(OH)2(O)2]W(PMe3)3H3 is in equilibrium with its agostic isomer [CalixBut(OH)2(O)2]W(PMe3)3H2. Dynamic NMR spectroscopy also indicates that the [M(PMe3)3H2] fragments of both the molybdenum and tungsten complexes [CalixBut(OH)2(O)2]M(PMe3)3H2 migrate rapidly around the phenolic rim of the calixarene on the NMR time scale, an observation that is in accord with incorporation of deuterium into the methylene endo positions upon treatment of the isomeric mixture of [CalixBut(OH)2(O)2]W(PMe3)3H2 and [Calix-HBut(OH)2(O)2]W(PMe3)3H3 with D2. Treatment of {[CalixBut(OH)2(O)2]W(PMe3)3H2} with Ph2C2 gives the alkylidene complex [CalixBut(O)4]W=C(Ph)Ar [Ar = PhCC(Ph)CH2Ph]. PMID:17165791

  3. Selective C–H bond activation of alkanes by gas-phase metal ions

    Czech Academy of Sciences Publication Activity Database

    Roithová, J.; Schröder, Detlef

    2010-01-01

    Roč. 110, č. 2 (2010), s. 1170-1211. ISSN 0009-2665 R&D Projects: GA AV ČR KJB400550704; GA ČR GA203/08/1487 Grant ostatní: European Research Council(XE) AdG HORIZOMS Institutional research plan: CEZ:AV0Z40550506 Keywords : alkanes * C-H bond activation * density functional theory * mass spectrometry * matrix isolation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 33.033, year: 2010

  4. Strength and leak testing of plasma activated bonded interfaces

    DEFF Research Database (Denmark)

    Visser, M.M.; Weichel, Steen; Reus, Roger De;

    2002-01-01

    Bond strength and hermeticity of plasma activated bonded (PAB) Si-Si interfaces are reported. Bonding of 100 mm Si(1 0 0) wafers was performed. An average bond strength of 9.0+/-3.9 MPa was achieved without performing any annealing steps. Cavities bonded in vacuum were found to be hermetic based on...... detection of changes in membrane deflections. The detection limit for leak was 8E-13 mbar l/s. For comparison, strength and leak tests were also performed with regular fusion bonded wafers annealed at 1100 degreesC. The PAB was found to withstand post-processing steps such as RCA cleaning, 24 h in de...

  5. 75 FR 50772 - Agency Information Collection Activities: Importation Bond Structure

    Science.gov (United States)

    2010-08-17

    ... Bond, to CBP. CBP proposes to revise CBP Form 301 in order to accurately reflect the changes that have... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Importation Bond... concerning the: Importation Bond Structure. This request for comment is being made pursuant to the...

  6. Interfiber bonding and fiber segment activation in paper

    Directory of Open Access Journals (Sweden)

    Hannu Paulapuro

    2007-01-01

    Full Text Available Bonding and activation in paper were studied with the help of laboratory test sheets and common paper strength tests. Different papermaking furnishes and raw material treatments were used to examine the effects they have on bonding and activation. Furthermore, various boundary conditions during drying were included to single out the influence of bonding and activation on paper properties. It was found that bonding is clearly increased by beating of kraft pulp, starch addition, and thermomechanical pulp fines, whereas activation benefited most from beating and addition of reinforcement fibers to mechanical pulp based furnishes. Subjecting test sheets to increasing amounts of drying stress affected activation positively, and bonding negatively. The increase in activation did not seem to be dependent on the beating degree of chemical pulp fibers. Bonding, on the other hand, deteriorated more significantly in sheets made of extensively beaten kraft fibers, i.e. in sheets where the initial bonding potential was higher. Commonly used paper strength measurements provide dependable and accurate tools for assessing the effect of different variables on both bonding and activation. A short literature survey of bonding and activation is also provided.

  7. Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

    International Nuclear Information System (INIS)

    This quarter has witnessed further progress both in our experimental methods of photoelectron spectroscopy and in our understanding the fundamental relationships between ionization energies and the chemistry of transition metal species. Progress continues on the new gas phase photoelectron spectrometer that combine improved capabilities for HeI/HeII UPS, XPS, and Auger investigations of organometallic molecules. Several measurements have been accomplished this year that were not possible previously. We have published the formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies, and applied the relationships to homonuclear and heteronuclear diatomic molecules, multiple bonds, and metal-ligand bonds. Studies of C-H bond activation have continued with examination of different degrees of Si-H bond addition to metals. the electronic effects of intermolecular interactions have been observed by comparing the ionizations of metal complexes in the gas phase with the ionizations of monolayer solid organometallic films prepared in ultra-high vacuum. The orientations of the molecules have been determined by scanning tunneling microscopy. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C60 molecule, buckminsterfullerene. Studies of the following complexes are described : Fe, Os, Nb, Mo, Rh, Re, Al, and Mn. 19 refs

  8. Rhodium mediated bond activation: from synthesis to catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Hung-An [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    Recently, our lab has developed monoanionic tridentate ligand, ToR, showing the corresponding coordination chemistry and catalyst reactivity of magnesium, zirconium, zinc and iridium complexes. This thesis details synthetic chemistry, structural study and catalytic reactivity of the ToR-supported rhodium compounds. Tl[ToR] has been proved to be a superior ligand transfer agent for synthesizing rhodium complexes. The salt metathesis route of Tl[ToM] with [Rh(μ-Cl)(CO)]2 and [Rh(μ- Cl)(COE)]2 gives ToMRh(CO)2 (2.2) and ToMRhH(β3-C8H13) (3.1) respectively while Tl[ToM] with [Rh(μ-Cl)(CO)]2 affords ToPRh(CO)2 (2.3). 2.2 reacts with both strong and weak electrophiles, resulting in the oxazoline N-attacked and the metal center-attacked compounds correspondingly. Using one of the metal center-attacked electrophiles, 2.3 was demonstrated to give high diastereoselectivity. Parallel to COE allylic C-H activation complex 3.1, the propene and allylbenzene allylic C-H activation products have also been synthesized. The subsequent functionalization attempts have been examined by treating with Brønsted acids, Lewis acids, electrophiles, nucleophiles, 1,3-dipolar reagents and reagents containing multiple bonds able to be inserted. Various related complexes have been obtained under these conditions, in which one of the azide insertion compounds reductively eliminates to give an allylic functionalization product stoichiometrically. 3.1 reacts with various primary alcohols to give the decarbonylation dihydride complex ToMRh(H)2CO (4.1). 4.1 shows catalytic reactivity for primary alcohol decarbonylation under a photolytic condition. Meanwhile, 2.2 has been found to be more reactive than 4.1 for catalytic alcohol decarbonylation under the same condition. Various complexes and primary

  9. Formation of Embedded Microstructures by Thermal Activated Solvent Bonding

    CERN Document Server

    Ng, S H; Wang, Z F; Lu, A C W; Rodriguez, I; De Rooij, N

    2008-01-01

    We present a thermal activated solvent bonding technique for the formation of embedded microstrucutres in polymer. It is based on the temperature dependent solubility of polymer in a liquid that is not a solvent at room temperature. With thermal activation, the liquid is transformed into a solvent of the polymer, creating a bonding capability through segmental or chain interdiffusion at the bonding interface. The technique has advantages over the more commonly used thermal bonding due to its much lower operation temperature (30 degrees C lower than the material's Tg), lower load, as well as shorter time. Lap shear test indicated bonding shear strength of up to 2.9 MPa. Leak test based on the bubble emission technique showed that the bonded microfluidic device can withstand at least 6 bars (87 psi) of internal pressure (gauge) in the microchannel. This technique can be applied to other systems of polymer and solvent.

  10. 76 FR 28801 - Agency Information Collection Activities: Bonded Warehouse Regulations

    Science.gov (United States)

    2011-05-18

    ... Federal Register (76 FR 11254) on March 1, 2011, allowing for a 60-day comment period. This notice allows... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Bonded Warehouse... approval in accordance with the Paperwork Reduction Act: Bonded Warehouse Regulations. This is a...

  11. Transition metal-catalyzed C(vinyl)-C(vinyl) bond formation via double C(vinyl)-H bond activation.

    Science.gov (United States)

    Shang, Xiaojie; Liu, Zhong-Quan

    2013-04-21

    Transition metal-catalyzed oxidative dehydrogenative coupling reactions of Caryl-H bonds with Cvinyl-H bonds to generate a Caryl-Cvinyl bonds have been well developed in recent decades. However, only a few studies have focused on the direct Cvinyl-Cvinyl bond formation via double Cvinyl-H bond activation. Recent developments in this active area have been highlighted in this tutorial review. PMID:23318664

  12. Electrochemical activation of a tetrathiafulvalene halogen bond donor in solution.

    Science.gov (United States)

    Oliveira, R; Groni, S; Fave, C; Branca, M; Mavré, F; Lorcy, D; Fourmigué, M; Schöllhorn, B

    2016-06-21

    The halogen bond donor properties of iodo-tetrathiafulvalene (I-TTF) can be electrochemically switched and controlled via reversible oxidation in the solution phase. Interestingly the activation of only one single halogen bond yielded already a strong and selective interaction, quantified by cyclic voltammetry. The standard potentials of the redox couples I-TTF(0/1+) and I-TTF(1+/2+) were observed to shift upon the addition of halides. These anions selectively stabilize the cationic I-TTF species through halogen bonding in polar liquid electrolytes. The thermodynamic affinity constants for chloride and bromide binding to the oxidized species have been determined. Competition in halide binding between I-TTF(1+) and other halogen bond donors allowed for comparing the relative donor strength of the respective electrophilic species. Furthermore it has been shown that halogen bonding can prevail over hydrogen bonding in the investigated system. PMID:27231819

  13. Exploration of earth-abundant transition metals (Fe, Co, and Ni) as catalysts in unreactive chemical bond activations.

    Science.gov (United States)

    Su, Bo; Cao, Zhi-Chao; Shi, Zhang-Jie

    2015-03-17

    Activation of inert chemical bonds, such as C-H, C-O, C-C, and so on, is a very important area, to which has been drawn much attention by chemists for a long time and which is viewed as one of the most ideal ways to produce valuable chemicals. Under modern chemical bond activation logic, many conventionally viewed "inert" chemical bonds that were intact under traditional conditions can be reconsidered as novel functionalities, which not only avoids the tedious synthetic procedures for prefunctionalizations and the emission of undesirable wastes but also inspires chemists to create novel synthetic strategies in completely different manners. Although activation of "inert" chemical bonds using stoichiometric amounts of transition metals has been reported in the past, much more attractive and challenging catalytic transformations began to blossom decades ago. Compared with the broad application of late and noble transition metals in this field, the earth-abundant first-row transition-metals, such as Fe, Co, and Ni, have become much more attractive, due to their obvious advantages, including high abundance on earth, low price, low or no toxicity, and unique catalytic characteristics. In this Account, we summarize our recent efforts toward Fe, Co, and Ni catalyzed "inert" chemical bond activation. Our research first unveiled the unique catalytic ability of iron catalysts in C-O bond activation of both carboxylates and benzyl alcohols in the presence of Grignard reagents. The benzylic C-H functionalization was also developed via Fe catalysis with different nucleophiles, including both electron-rich arenes and 1-aryl-vinyl acetates. Cobalt catalysts also showed their uniqueness in both aromatic C-H activation and C-O activation in the presence of Grignard reagents. We reported the first cobalt-catalyzed sp(2) C-H activation/arylation and alkylation of benzo[h]quinoline and phenylpyridine, in which a new catalytic pathway via an oxidative addition process was demonstrated

  14. Identification and H(D)-bond energies of C-H(D)Cl interactions in chloride-haloalkane clusters: a combined X-ray crystallographic, spectroscopic, and theoretical study.

    Science.gov (United States)

    Serebryanskaya, Tatiyana V; Novikov, Alexander S; Gushchin, Pavel V; Haukka, Matti; Asfin, Ruslan E; Tolstoy, Peter M; Kukushkin, Vadim Yu

    2016-05-18

    The cationic (1,3,5-triazapentadiene)Pt(II) complex [Pt{NH[double bond, length as m-dash]C(N(CH2)5)N(Ph)C(NH2)[double bond, length as m-dash]NPh}2]Cl2 ([]Cl2) was crystallized from four haloalkane solvents giving [][Cl2(CDCl3)4], [][Cl2(CHBr3)4], [][Cl2(CH2Cl2)2], and [][Cl2(C2H4Cl2)2] solvates that were studied by X-ray diffraction. In the crystal structures of [][Cl2(CDCl3)4] and [][Cl2(CHBr3)4], the Cl(-) ion interacts with two haloform molecules via C-DCl(-) and C-HCl(-) contacts, thus forming the negatively charged isostructural clusters [Cl(CDCl3)2](-) and [Cl(CHBr3)2](-). In the structures of [][Cl2(CH2Cl2)2] and [][Cl2(C2H4Cl2)2], cations [](2+) are linked to a 3D-network by a system of H-bondings including one formed by each Cl(-) ion with CH2Cl2 or C2H4Cl2 molecules. The lengths and energies of these H-bonds in the chloride-haloalkane clusters were analyzed by DFT calculations (M06 functional) including AIM analysis. The crystal packing noticeably affected the geometry of the clusters, and energy of C-HCl(-) hydrogen bonds ranged from 1 to 6 kcal mol(-1). An exponential correlation (R(2) > 0.98) between the calculated Cl(-)H distances and the energies of the corresponding contacts was found and used to calculate hydrogen bond energies from the experimental Cl(-)H distances. Predicted energy values (3.3-3.9 kcal mol(-1) for the [Cl(CHCl3)2](-) cluster) are in a reasonable agreement with the energy of the Cl3C-HCl(-) bond estimated using ATRFTIR spectroscopy (2.7 kcal mol(-1)). PMID:27157359

  15. Computational Exploration of Rh(III)/Rh(V) and Rh(III)/Rh(I) Catalysis in Rhodium(III)-Catalyzed C-H Activation Reactions of N-Phenoxyacetamides with Alkynes.

    Science.gov (United States)

    Yang, Yun-Fang; Houk, K N; Wu, Yun-Dong

    2016-06-01

    The selective rhodium-catalyzed functionalization of arenes is greatly facilitated by oxidizing directing groups that act both as directing groups and internal oxidants. We report density functional theory (B3LYP and M06) investigations on the mechanism of rhodium(III)-catalyzed redox coupling reaction of N-phenoxyacetamides with alkynes. The results elucidated the role of the internal oxidizing directing group, and the role of Rh(III)/Rh(I) and Rh(III)/Rh(V) catalysis of C-H functionalizations. A novel Rh(III)-Rh(V)-Rh(III) cycle successfully rationalizes recent experimental observations by Liu and Lu et al. ( Liu , G. Angew. Chem. Int. Ed. 2013 , 52 , 6033 ) on the reactions of N-phenoxyacetamides with alkynes in different solvents. Natural Bond Orbital (NBO) analysis confirms the identity of Rh(V) intermediate in the catalytic cycle. PMID:27177448

  16. Active Thermochemical Tables: Sequential Bond Dissociation Enthalpies of Methane, Ethane, and Methanol and the Related Thermochemistry.

    Science.gov (United States)

    Ruscic, Branko

    2015-07-16

    Active Thermochemical Tables (ATcT) thermochemistry for the sequential bond dissociations of methane, ethane, and methanol systems were obtained by analyzing and solving a very large thermochemical network (TN). Values for all possible C-H, C-C, C-O, and O-H bond dissociation enthalpies at 298.15 K (BDE298) and bond dissociation energies at 0 K (D0) are presented. The corresponding ATcT standard gas-phase enthalpies of formation of the resulting CHn, n = 4-0 species (methane, methyl, methylene, methylidyne, and carbon atom), C2Hn, n = 6-0 species (ethane, ethyl, ethylene, ethylidene, vinyl, ethylidyne, acetylene, vinylidene, ethynyl, and ethynylene), and COHn, n = 4-0 species (methanol, hydroxymethyl, methoxy, formaldehyde, hydroxymethylene, formyl, isoformyl, and carbon monoxide) are also presented. The ATcT thermochemistry of carbon dioxide, water, hydroxyl, and carbon, oxygen, and hydrogen atoms is also included, together with the sequential BDEs of CO2 and H2O. The provenances of the ATcT enthalpies of formation, which are quite distributed and involve a large number of relevant determinations, are analyzed by variance decomposition and discussed in terms of principal contributions. The underlying reasons for periodic appearances of remarkably low and/or unusually high BDEs, alternating along the dissociation sequences, are analyzed and quantitatively rationalized. The present ATcT results are the most accurate thermochemical values currently available for these species. PMID:25760799

  17. Hydrogen bonds of anti-HIV active aminophenols

    Science.gov (United States)

    Belkov, M. V.; Ksendzova, G. A.; Skornyakov, I. V.; Sorokin, V. L.; Tolstorozhev, G. B.; Shadyro, O. I.

    2011-05-01

    Analysis of IR-Fourier spectra from solutions and crystals of antiviral sulfo-containing aminophenols has shown that various types of intramolecular and intermolecular interactions can occur in molecules of these compounds. Three types of intramolecular hydrogen bonds (O-HṡṡṡN, O-HṡṡṡO=S=O, and N-HṡṡṡO=S=O) are formed in CCl4 solutions of the sulfo-containing aminophenols. The formation of intermolecular H-bonds involving the NH- and OH-groups and the preservation of the intramolecular O-HṡṡṡO=S=O H-bond are characteristic of the anti-HIV active aminophenol crystals. Spectral attributes are determined in order to distinguish between the anti-HIV active and inactive sulfo-containing aminophenols.

  18. A potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insights

    KAUST Repository

    Ajitha, Manjaly John

    2016-03-29

    The possibility of direct introduction of a new functionality through C–H bond activation is an attractive strategy in covalent synthesis. Here, we investigated the mechanism of Rh-catalysed C-H amination of the hetero-aryl substrate (2-phenylpyridine) using phenyl azide as nitrogen source by density functional theory (DFT). For the deprotocyclometallation and protodecyclometallation processes of the title reaction, we propose a stepwise base-assisted mechanism (pathway I) instead of previously reported concerted mechanism (pathway II). In the new mechanism proposed here, 2-phenylpyridine acts as a base in the initial deprotonation step (C-H bond cleavage) and transports the proton towards the final protonation step. In fact, the N-H bond of the strong conjugate acid (formed during initial C-H bond cleavage) considered in pathway I (via TS4) is more acidic than the C-H bond of the neutral substrate considered in pathway II (via TS5). The higher activation barrier of TS5 mainly originates from the ring strain of the four membered cyclic transition state. The vital role of base, as disclosed here, can potentially have broader mechanistic implications for the development of reaction conditions of transition metal catalysed reactions.

  19. Bipyridine- and phenanthroline-based metal-organic frameworks for highly efficient and tandem catalytic organic transformations via directed C-H activation

    Energy Technology Data Exchange (ETDEWEB)

    Manna, Kuntal [Univ. of Chicago, Chicago, IL (United States); Zhang, Teng [Univ. of Chicago, Chicago, IL (United States); Greene, Francis X. [Univ. of Chicago, Chicago, IL (United States); Lin, Wenbin [Univ. of Chicago, Chicago, IL (United States)

    2015-02-16

    We report here the synthesis of a series of robust and porous bipyridyl- and phenanthryl-based metal–organic frameworks (MOFs) of UiO topology (BPV-MOF, mBPV-MOF, and mPT-MOF) and their postsynthetic metalation to afford highly active single-site solid catalysts. While BPV-MOF was constructed from only bipyridyl-functionalized dicarboxylate linker, both mBPV- and mPT-MOF were built with a mixture of bipyridyl- or phenanthryl-functionalized and unfunctionalized dicarboxylate linkers. The postsynthetic metalation of these MOFs with [Ir(COD)(OMe)]2 provided Ir-functionalized MOFs (BPV-MOF-Ir, mBPV-MOF-Ir, and mPT-MOF-Ir), which are highly active catalysts for tandem hydrosilylation of aryl ketones and aldehydes followed by dehydrogenative ortho-silylation of benzylicsilyl ethers as well as C–H borylation of arenes using B₂pin₂. Both mBPV-MOF-Ir and mPT-MOF-Ir catalysts displayed superior activities compared to BPV-MOF-Ir due to the presence of larger open channels in the mixed-linker MOFs. Impressively, mBPV-MOF-Ir exhibited high TONs of up to 17000 for C–H borylation reactions and was recycled more than 15 times. The mPT-MOF-Ir system is also active in catalyzing tandem dehydrosilylation/dehydrogenative cyclization of N-methylbenzyl amines to azasilolanes in the absence of a hydrogen acceptor. Importantly, MOF-Ir catalysts are significantly more active (up to 95 times) and stable than their homogeneous counterparts for all three reactions, strongly supporting the beneficial effects of active site isolation within MOFs. This work illustrates the ability to increase MOF open channel sizes by using the mixed linker approach and shows the enormous potential of developing highly active and robust single-site solid catalysts based on MOFs containing nitrogen-donor ligands for important organic transformations.

  20. 77 FR 6814 - Agency Information Collection Activities: Bonded Warehouse Proprietor's Submission

    Science.gov (United States)

    2012-02-09

    ... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Bonded Warehouse... the Bonded Warehouse Proprietor's Submission (CBP Form 300). This request for comment is being made... CBP is soliciting comments concerning the following information collection: Title: Bonded...

  1. Scalable and sustainable electrochemical allylic C-H oxidation.

    Science.gov (United States)

    Horn, Evan J; Rosen, Brandon R; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D; Baran, Phil S

    2016-05-01

    New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as "classics". Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact. PMID:27096371

  2. Control of the intermolecular coupling of dibromotetracene on Cu(110) by the sequential activation of C-Br and C-H bonds.

    Science.gov (United States)

    Ferrighi, Lara; Píš, Igor; Nguyen, Thanh Hai; Cattelan, Mattia; Nappini, Silvia; Basagni, Andrea; Parravicini, Matteo; Papagni, Antonio; Sedona, Francesco; Magnano, Elena; Bondino, Federica; Di Valentin, Cristiana; Agnoli, Stefano

    2015-04-01

    Dibromotetracene molecules are deposited on the Cu(110) surface at room temperature. The complex evolution of this system has been monitored at different temperatures (i.e., 298, 523, 673, and 723 K) by means of a variety of complementary techniques that range from STM and temperature-programmed desorption (TPD) to high-resolution X-ray spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). State-of-the-art density-functional calculations were used to determine the chemical processes that take place on the surface. After deposition at room temperature, the organic molecules are transformed into organometallic monomers through debromination and carbon-radical binding to copper adatoms. Organometallic dimers, trimers, or small oligomers, which present copper-bridged molecules, are formed by increasing the temperature. Surprisingly, further heating to 673 K causes the formation of elongated chains along the Cu(110) close-packed rows as a consequence of radical-site migration to the thermodynamically more stable molecule heads. Finally, massive dehydrogenation occurs at the highest temperature followed by ring condensation to nanographenic patches. This study is a paradigmatic example of how intermolecular coupling can be modulated by the stepwise control of a simple parameter, such as temperature, through a sequence of domino reactions. PMID:25711882

  3. Indole cyanation via C-H bond activation under catalysis of Ru(Ⅲ)-exchanged NaY zeolite (RuY) as a recyclable catalyst

    Institute of Scientific and Technical Information of China (English)

    Alireza Khorshidi

    2012-01-01

    Selective 3-cyanation of indoles was achieved under heterogeneous catalysis of Ru(Ⅲ)-exchanged NaY zeolite (RuY) as a recyclable catalyst,in combination with K4[Fe(CN)6] as a nontoxic,slow cyanide releasing agent.Under the aforementioned conditions,good yields of the desired products were obtained.

  4. Cobalt-Catalyzed Cyclization of N-Methoxy Benzamides with Alkynes using an Internal Oxidant through C-H/N-O Bond Activation.

    Science.gov (United States)

    Sivakumar, Ganesan; Vijeta, Arjun; Jeganmohan, Masilamani

    2016-04-18

    The cyclization of substituted N-methoxy benzamides with alkynes in the presence of an easily affordable cobalt complex and NaOAc provides isoquinolone derivatives in good to excellent yields. The cyclization reaction is compatible with a range of functional group-substituted benzamides, as well as ester- and alcohol-substituted alkynes. The cobalt complex [Co(III) Cp*(OR)2 ] (R=Me or Ac) serves as an efficient catalyst for the cyclization reaction. Later, isoquinolone derivatives were converted into 1-chloro and 1-bromo substituted isoquinoline derivatives in excellent yields in the presence of POCl3 or PBr3 . PMID:26951887

  5. Ruthenium(II)-catalyzed synthesis of pyrrole- and indole-fused isocoumarins by C-H bond activation in DMF and water

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, K.S.; Sawant, S.G.; Dixneuf, P.H.

    isocoumarin derivatives. These catalytic reactions can be performed in DMF and competively in water. COMMUNICATION Keisham S. Singh*,Sneha G. Sawant, Pierre H. Dixneuf * Page No. – Page No. Ruthenium(II) catalysed synthesis of pyrrole...

  6. Activation of the C-H bond: catalytic hydroxylation of hydrocarbons by new cobaltic alkylperoxydic complexes; selective and catalytic cycloalkane dehydrogenation in presence of uranium for hydrogen transfer

    International Nuclear Information System (INIS)

    The aim of the thesis is to improve efficiency and selectivity of chemical reactions for alkane transformations. In the first part decomposition of hydroperoxides and hydrocarbon hydroxylation by cobalt complexes is studied. In the second part cycloalkanes are dehydrogenated into aromatics with a Pt catalyst, trapping hydrogen by uranium. Uranium hydride UH3 can yield very pure hydrogen at reasonable temperature

  7. I. Developing methods for the analysis of chemistry students' inscriptions, II. Exploring the regioselectivity of 1,3-dipolar cycloadditions of munchnones, III. Stereochemical investigations of C-H activation reactions involving germylene and stannylene/aryl iodide reagents

    Science.gov (United States)

    Kiste, Alan L.

    I. Analyzing and comparing student-generated inscriptions in chemistry is crucial to gaining insight into students' understanding about chemistry concepts. Thus, we developed two methods of analyzing student-generated inscriptions: features analysis and thematic analysis. We have also demonstrated how these methods are able to discern differences between both how students inscribe their understandings and the content of those inscriptions, regardless of (1) how those inscriptions were created (i.e. computer vs. pencil-and-paper), (2) the nature of the inscriptions (verbal vs. pictorial), and (3) the expertise of the students. The ability to analyze inscriptions regardless of the medium allows the examination of multiple inscriptions in educational research applications as well as in the design and development of educational materials. Also, inscriptions can be compared across contexts, allowing the comparison of student-generated inscriptions derived from various educational interventions. Finally, the ability to compare inscriptions regardless of the level of expertise allows novice/expert comparisons as well as longitudinal comparison over time. II. Predicting the regiochemistry of 1,3-dipolar cycloadditions of munchnones and acetylenic dipolarophiles is difficult based on frontier molecular orbital theory (FMO) alone. We have proposed that, in addition to FMO considerations, steric factors influencing the non-covalent interactions between reactive centers in the transition state also influence the regioselectivity of these reactions. We have developed a scheme to use a tether-based regiocontrol strategy to synthesize 2,4-disubstituted pyrroles using N-(2-thiazolinyl) secondary amino acid derivatives. Attempts to synthesize these amino acid derivatives have been, so far, unsuccessful. III. To provide additional information about the mechanism of C-H activation reactions of stannylenes and germylenes, and to demonstrate the utility of these reactions, we explored

  8. Actor Bonds in Situations of Discontinuous Business Activities

    DEFF Research Database (Denmark)

    Skaates, Maria Anne

    2000-01-01

    Demand in many industrial buying situations, e.g. project purchases or procurement related to virtual organizations, is discontinuous. In situations of discontinuity, networks are often more of an ad hos informational and social nature, as strong activity and resource links are not present...... the institutional concept of the "field". Finally this paper introduces the concept of "social capital" (Bourdieu, 1983) and discusses whether it can be used to conceptualize the dynamic features of actor bonds in situations of discontinuity....

  9. C-H activation versus yttrium-methyl cation formation from [Y(AlMe4)3] induced by cyclic polynitrogen bases: solvent and substituent-size effects.

    Science.gov (United States)

    Bojer, Daniel; Venugopal, Ajay; Mix, Andreas; Neumann, Beate; Stammler, Hans-Georg; Mitzel, Norbert W

    2011-05-23

    The reaction of 1,3,5-triisopropyl-1,3,5-triazacyclohexane (TiPTAC) with [Y(AlMe(4))(3)] resulted in the formation of [(TiPTAC)Y(Me(3)AlCH(2)AlMe(3))(μ-MeAlMe(3))] by C-H activation and methane extrusion. In contrast, the presence of bulkier cyclohexyl groups on the nitrogen atoms in 1,3,5-tricyclohexyl-1,3,5-triazacyclohexane (TCyTAC) led to the formation of the cationic dimethyl complex [(TCyTAC)(2)YMe(2)][AlMe(4)]. The investigations reveal a dependency of the reaction mechanism on the steric bulk of the N-alkyl entity and the solvent employed. In toluene C-H activation was observed in reactions of [Y(AlMe(4))(3)] with 1,3,5-trimethyl-1,3,5-triazacyclohexane (TMTAC) and TiPTAC. In THF molecular dimethyl cations, such as [(TCyTAC)(2)YMe(2)][AlMe(4)], [(TMTAC)(2)YMe(2)][AlMe(4)] and [(TiPTAC)(2)YMe(2)][AlMe(4)], could be synthesised by addition of the triazacyclohexane at a later stage. The THF-solvated complex [YMe(2)(thf)(5)][AlMe(4)] could be isolated and represents an intermediate in these reactions. It shows that cationic methyl complexes of the rare-earth metals can be formed by donor-induced cleavage of the rare-earth-metal tetramethylaluminates. The compounds were characterised by single-crystal X-ray diffraction or multinuclear and variable-temperature NMR spectroscopy, as well as elemental analyses. Variable-temperature NMR spectroscopy illustrates the methyl group exchange processes between the cations and anions in solution. PMID:21503986

  10. Development of HIP bonding procedure and mechanical properties of HIP bonded joints for reduced activation ferritic steel F-82H

    International Nuclear Information System (INIS)

    Structural materials of blanket components in fusion DEMO reactors will receive a neutron wall load more than 3-5MW/m2 as well as exposed by surface heat flux more than 0.5MW/m2. A reduced activation ferritic steel F-82H has been developed by JAERI in collaboration with NKK from viewpoints of resistance for high temperature and neutron loads and lower radioactivity. This study intends to obtain basic performance of F-82H to establish the fabrication procedure of the first wall and blanket box by using Hot Isostatic Pressing (HIP) bonding. Before HIP bonding tests, effects of heat treatment temperature and surface roughness on mechanical properties of joints were investigated in the heat treatment tests and diffusion bonding tests, respectively. From these results, the optimum HIP bonding conditions and the post heat treatment were selected. Using these conditions, the HIP bonding tests were carried out to evaluate HIP bondability and to obtain mechanical properties of the joints. Sufficient HIP bonding performance was obtained under the temperature of 1040degC, the compressive stress of 150MPa, the holding time of 2h, and the surface roughness ∼μ m. Mechanical properties of HIP bonded joints with these conditions were similar to those of as-received base metal. An oxide formation on the surface to be bonded would need to be avoided for sufficient bonding. The bonding ratio, Charpy impact value and fatigue performance of the joints strongly depended on the HIP conditions, especially temperature, while micro-structure, Vickers hardness and tensile properties had little dependence on the HIP temperature. The surface roughness strongly affected the bonding ratio and would be required to be in the level of a few μ m. In the HIP bonding test of the welded material, the once-melted surface could be jointed by the HIP bonding under the above-mentioned procedure. (J.P.N.)

  11. C-H and C-C activation of n -butane with zirconium hydrides supported on SBA15 containing N-donor ligands: [(≡SiNH-)(≡SiX-)ZrH2], [(≡SiNH-)(≡SiX-)2ZrH], and[(≡SiN=)(≡SiX-)ZrH] (X = -NH-, -O-). A DFT study

    KAUST Repository

    Pasha, Farhan Ahmad

    2014-07-01

    Density functional theory (DFT) was used to elucidate the mechanism of n-butane hydrogenolysis (into propane, ethane, and methane) on well-defined zirconium hydrides supported on SBA15 coordinated to the surface via N-donor surface pincer ligands: [(≡SiNH-)(≡SiO-)ZrH2] (A), [(≡SiNH-)2ZrH2] (B), [(≡SiNH-)(≡SiO-) 2ZrH] (C), [(≡SiNH-)2(≡SiO-)ZrH] (D), [(≡SiN=)(≡Si-O-)ZrH] (E), and [(≡SiN=)(≡SiNH-)ZrH] (F). The roles of these hydrides have been investigated in C-H/C-C bond activation and cleavage. The dihydride A linked via a chelating [N,O] surface ligand was found to be more active than B, linked to the chelating [N,N] surface ligand. Moreover, the dihydride zirconium complexes are also more active than their corresponding monohydrides C-F. The C-C cleavage step occurs preferentially via β-alkyl transfer, which is the rate-limiting step in the alkane hydrogenolysis. The energetics of the comparative pathways over the potential energy surface diagram (PES) reveals the hydrogenolysis of n-butane into propane and ethane. © 2014 American Chemical Society.

  12. CHEMICAL ACTIVATION OF MOLECULES BY METALS: EXPERIMENTAL STUDIES OF ELECTRON DISTRIBUTIONS AND BONDING

    Energy Technology Data Exchange (ETDEWEB)

    LICHTENBERGER, DENNIS L.

    2002-03-26

    This research program is directed at obtaining detailed experimental information on the electronic interactions between metals and organic molecules. These interactions provide low energy pathways for many important chemical and catalytic processes. A major feature of the program is the continued development and application of our special high-resolution valence photoelectron spectroscopy (UPS), and high-precision X-ray core photoelectron spectroscopy (XPS) instrumentation for study of organometallic molecules in the gas phase. The study involves a systematic approach towards understanding the interactions and activation of bound carbonyls, C-H bonds, methylenes, vinylidenes, acetylides, alkenes, alkynes, carbenes, carbynes, alkylidenes, alkylidynes, and others with various monometal, dimetal, and cluster metal species. Supporting ligands include -aryls, alkoxides, oxides, and phosphines. We are expanding our studies of both early and late transition metal species and electron-rich and electron-poor environments in order to more completely understand the electronic factors that serve to stabilize particular organic fragments and intermediates on metals. Additional new directions for this program are being taken in ultra-high vacuum surface UPS, XPS, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments on both physisorbed and chemisorbed organometallic thin films. The combination of these methods provides additional electronic structure information on surface-molecule and molecule-molecule interactions. A very important general result emerging from this program is the identification of a close relationship between the ionization energies of the species and the thermodynamics of the chemical and catalytic reactions of these systems.

  13. CHEMICAL ACTIVATION OF MOLECULES BY METALS: EXPERIMENTAL STUDIES OF ELECTRON DISTRIBUTIONS AND BONDING; FINAL

    International Nuclear Information System (INIS)

    This research program is directed at obtaining detailed experimental information on the electronic interactions between metals and organic molecules. These interactions provide low energy pathways for many important chemical and catalytic processes. A major feature of the program is the continued development and application of our special high-resolution valence photoelectron spectroscopy (UPS), and high-precision X-ray core photoelectron spectroscopy (XPS) instrumentation for study of organometallic molecules in the gas phase. The study involves a systematic approach towards understanding the interactions and activation of bound carbonyls, C-H bonds, methylenes, vinylidenes, acetylides, alkenes, alkynes, carbenes, carbynes, alkylidenes, alkylidynes, and others with various monometal, dimetal, and cluster metal species. Supporting ligands include -aryls, alkoxides, oxides, and phosphines. We are expanding our studies of both early and late transition metal species and electron-rich and electron-poor environments in order to more completely understand the electronic factors that serve to stabilize particular organic fragments and intermediates on metals. Additional new directions for this program are being taken in ultra-high vacuum surface UPS, XPS, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments on both physisorbed and chemisorbed organometallic thin films. The combination of these methods provides additional electronic structure information on surface-molecule and molecule-molecule interactions. A very important general result emerging from this program is the identification of a close relationship between the ionization energies of the species and the thermodynamics of the chemical and catalytic reactions of these systems

  14. Palladium(ii)-catalyzed C-C and C-O bond formation for the synthesis of C1-benzoyl isoquinolines from isoquinoline N-oxides and nitroalkenes.

    Science.gov (United States)

    Li, Jiu-Ling; Li, Wei-Ze; Wang, Ying-Chun; Ren, Qiu; Wang, Heng-Shan; Pan, Ying-Ming

    2016-08-01

    C1-Benzoyl isoquinolines can be generated via a palladium(ii)-catalyzed C-C and C-O coupling of isoquinoline N-oxides with aromatic nitroalkenes. The reaction proceeds through remote C-H bond activation and subsequent intramolecular oxygen atom transfer (OAT). In this reaction, the N-O bond was designed as a directing group in the C-H bond activation as well as the source of an oxygen atom. PMID:27443150

  15. Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

    International Nuclear Information System (INIS)

    The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies has been developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. This relationship has been used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. We have been able to obtain a direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal. The ionization energies have also been used to correlate the rates of carbonyl substitution reactions of (η5-C5H4X)Rh(CO)2 complexes, and to reveal the electronic factors that control the stability of the transition state. The extent that the electronic features of these bonding interactions transfer to other chemical systems is being investigated in terms of the principle of additivity of ligand electronic effects. Specific examples under study include metal- phosphines, metal-halides, and metallocenes. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C60 molecule, buckminsterfullerene, and its interaction with a metal surface. The high-resolution valence ionizations in the gas phase reveal the high symmetry of the molecule, and studies of thin films of C60 reveal weak intermolecular interactions. Scanning tunneling and atomic force microscopy reveal the arrangement of spherical molecules on gold substrates, with significant delocalization of charge from the metal surface. 21 refs

  16. Effects of lithium-implantation on the hydrogen retention in both a-C:H and a-Si C:H materials submitted to deuterium bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Barbier, G.; Chevarier, N.; Chevarier, A. [Lyon-1 Univ., 69 -Villeurbanne (France). Inst. de Physique Nucleaire; Ross, G.G.; El Khakani, M.A. [INRS-Energie et Materiaux, Varennes, PQ (Canada)

    1996-09-01

    The hydrogen release in plasma facing materials is a challenging problem for the hydrogen recycling. The hydrogen desorption from a-C:H and a-SiC:H materials induced by deuterium bombardment has been investigated. Prior to the deuterium bombardment, both materials were implanted with different fluences of lithium ions. Before and after each irradiation, depth profiles of H, Li and deuterium were determined by nuclear microanalysis. After deuterium bombardment, il is shown that the retention of the initial hydrogen in both materials was enhanced by increasing the total dose of the implanted Li. For the a-C:H samples, the hydrogen desorption under deuterium bombardment was strongly reduced by lithium implantation. This effect was also evidenced in a-SiC:H samples, even though it is less spectacular that in a-C:H. Also, nuclear analyses showed that the retained dose of deuterium decreases when the lithium concentration increases. This could be a result of the formation of Li-H bonds which occurs to the detriment of deuterium retention in both a-C:H and a-SiC:H materials. Preliminary results of both materials exposed to TdeV tokamak discharges confirms the role of Li in hydrogen retention, already observed in deuterium bombardment exposure. (author).

  17. Proposal of an Amide-Directed Carbocupration Mechanism for Copper-Catalyzed meta-Selective C-H Arylation of Acetanilides by Diaryliodonium Salts

    Institute of Scientific and Technical Information of China (English)

    Song-lin Zhang; Yu-qiang Ding

    2011-01-01

    We examined the puzzling mechanism for Cu-catalyzed meta-C-H arylation reaction of anilides by diaryliodonium salts through systematic theoretical analysis.The previously proposed anti-oxy-cupration mechanism featuring anti- 1,2- or anti- 1,4-addition of cuprate and oxygen to the phenyl ring generating a meta-cuprated intermediate was excluded due to the large activation barriers.Alternatively,a new amide-directed carbocupration mechanism was proposed which involves a critical rate- and regio-determining step of amide-directed addition of the Cu(III)-aryl bond across the phenyl C2=C3 double bond to form an orthocuprated,meta-arylated intermediate.This mechanism is kinetically the most favored among several possible mechanisms such as ortho- or para-cupration/migration mechanism,direct meta C-H bond cleavage mediated by Cu(III) or Cu(I),and Cu(III)-catalyzed ortho-directed C-H bond activation mechanism.Furthermore,the predicted regioselectivity based on this mechanism has been shown to favor the meta-arylation that is consistent with the experimental observations.

  18. Decorative a-C:H coatings

    Czech Academy of Sciences Publication Activity Database

    Černý, F.; Jech, V.; Štěpánek, I.; Macková, Anna; Konvičková, S.

    roč. 256, 3 s. 1 (2009), s77-s81. ISSN 0169-4332 Institutional research plan: CEZ:AV0Z10480505 Keywords : a-C:H films * decorative coatings * adhesion Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.616, year: 2009

  19. Ortho-Functionalized Aryltetrazines by Direct Palladium-Catalyzed C-H Halogenation: Application to Fast Electrophilic Fluorination Reactions.

    Science.gov (United States)

    Testa, Christelle; Gigot, Élodie; Genc, Semra; Decréau, Richard; Roger, Julien; Hierso, Jean-Cyrille

    2016-04-25

    A general catalyzed direct C-H functionalization of s-tetrazines is reported. Under mild reaction conditions, N-directed ortho-C-H activation of tetrazines allows the introduction of various functional groups, thus forming carbon-heteroatom bonds: C-X (X=I, Br, Cl) and C-O. Based on this methodology, we developed electrophilic mono- and poly-ortho-fluorination of tetrazines. Microwave irradiation was optimized to afford fluorinated s-aryltetrazines, with satisfactory selectivity, within only ten minutes. This work provides an efficient and practical entry for further accessing highly substituted tetrazine derivatives (iodo, bromo, chloro, fluoro, and acetate precursors). It gives access to ortho-functionalized aryltetrazines which are difficult to obtain by classical Pinner-like syntheses. PMID:27010438

  20. Metal-Free sp(2)-C-H Borylation as a Common Reactivity Pattern of Frustrated 2-Aminophenylboranes.

    Science.gov (United States)

    Chernichenko, Konstantin; Lindqvist, Markus; Kótai, Bianka; Nieger, Martin; Sorochkina, Kristina; Pápai, Imre; Repo, Timo

    2016-04-13

    C-H borylation is a powerful and atom-efficient method for converting affordable and abundant chemicals into versatile organic reagents used in the production of fine chemicals and functional materials. Herein we report a facile C-H borylation of aromatic and olefinic C-H bonds with 2-aminophenylboranes. Computational and experimental studies reveal that the metal-free C-H insertion proceeds via a frustrated Lewis pair mechanism involving heterolytic splitting of the C-H bond by cooperative action of the amine and boryl groups. The adapted geometry of the reactive B and N centers results in an unprecedentently low kinetic barrier for both insertion into the sp(2)-C-H bond and intramolecular protonation of the sp(2)-C-B bond in 2-ammoniophenyl(aryl)- or -(alkenyl)borates. This common reactivity pattern serves as a platform for various catalytic reactions such as C-H borylation and hydrogenation of alkynes. In particular, we demonstrate that simple 2-aminopyridinium salts efficiently catalyze the C-H borylation of hetarenes with catecholborane. This reaction is presumably mediated by a borenium species isoelectronic to 2-aminophenylboranes. PMID:27003334

  1. Palladium-catalysed transannular C-H functionalization of alicyclic amines

    Science.gov (United States)

    Topczewski, Joseph J.; Cabrera, Pablo J.; Saper, Noam I.; Sanford, Melanie S.

    2016-03-01

    Discovering pharmaceutical candidates is a resource-intensive enterprise that frequently requires the parallel synthesis of hundreds or even thousands of molecules. C-H bonds are present in almost all pharmaceutical agents. Consequently, the development of selective, rapid and efficient methods for converting these bonds into new chemical entities has the potential to streamline pharmaceutical development. Saturated nitrogen-containing heterocycles (alicyclic amines) feature prominently in pharmaceuticals, such as treatments for depression (paroxetine, amitifadine), diabetes (gliclazide), leukaemia (alvocidib), schizophrenia (risperidone, belaperidone), malaria (mefloquine) and nicotine addiction (cytisine, varenicline). However, existing methods for the C-H functionalization of saturated nitrogen heterocycles, particularly at sites remote to nitrogen, remain extremely limited. Here we report a transannular approach to selectively manipulate the C-H bonds of alicyclic amines at sites remote to nitrogen. Our reaction uses the boat conformation of the substrates to achieve palladium-catalysed amine-directed conversion of C-H bonds to C-C bonds on various alicyclic amine scaffolds. We demonstrate this approach by synthesizing new derivatives of several bioactive molecules, including varenicline.

  2. Direct C-H alkylation and indole formation of anilines with diazo compounds under rhodium catalysis.

    Science.gov (United States)

    Mishra, Neeraj Kumar; Choi, Miji; Jo, Hyeim; Oh, Yongguk; Sharma, Satyasheel; Han, Sang Hoon; Jeong, Taejoo; Han, Sangil; Lee, Seok-Yong; Kim, In Su

    2015-12-18

    The rhodium(III)-catalyzed direct functionalization of aniline C-H bonds with α-diazo compounds is described. These transformations provide a facile construction of ortho-alkylated anilines with diazo malonates or highly substituted indoles with diazo acetoacetates. PMID:26458276

  3. Deposition and characterisation of multilayer hard coatings. Ti/TiNδ/TiCxNy/(TiC) a-C:H/(Ti) a-C:H

    International Nuclear Information System (INIS)

    Multilayer hard coatings containing Ti, TiNδ, TiCxNy, (TiCm) a-C:H, (TiCn) a-C:H, and (Ti) a-C:H were deposited on commercially pure titanium substrates by using an asymmetric bipolar pulsed-dc reactive magnetron sputtering of a titanium target, with Ar, Ar+N2, Ar+N2+CH4, and Ar+CH4 gas mixtures. The microstructures, elemental compositions and bonding states of the interlayers and the coating surfaces were studied by using cross-sectional transmission electron microscopy (XTEM), electron energy loss spectroscopy (EELS), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The microstructure development of the multilayer coating was strongly influenced by target poisoning. As a result of the complete poisoning of the titanium target during the deposition of TiNδ and TiCxNy interlayers, the a-C:H interlayers containing graded titanium and nitrogen contents were found to develop successively to the TiCxNy interlayer without the formation of near-stoichiometric TiC. The (TiCm) a-C:H interlayer consisted of nano-particles of distorted fcc crystal structure embedded in the a-C:H matrix. The (TiCn) a-C:H and (Ti) a-C:H top layers were found to be a-C:H matrix without nano-particles. In the (Ti) a-C:H top layer there was no measurable amount of Ti observed, regardless of the variation of CH4 concentration between 37.5 and 60 % flow rate in Ar+-CH4 gas mixture. The top layer (Ti) a-C:H was found to contain approximately 10 atomic % nitrogen, due to N2 contamination during deposition caused by low conductance of N2 through the nominally closed valve of the mass flow controller. The change of the CH4 concentration during deposition of the top layer (Ti) a-C:H, however, showed a strong influence on the hydrogen content. The comparison of the fluorescence background of the Raman spectra revealed that hydrogen-less (Ti) a-C:H was deposited at a CH4 concentration of less than 50 % flow rate in Ar. The hardness and adhesion of the multilayer

  4. Strength and leak testing of plasma activated bonded interfaces

    DEFF Research Database (Denmark)

    Visser, M.M.; Weichel, Steen; Reus, Roger De; Hanneborg, A.B.

    detection of changes in membrane deflections. The detection limit for leak was 8E-13 mbar l/s. For comparison, strength and leak tests were also performed with regular fusion bonded wafers annealed at 1100 degreesC. The PAB was found to withstand post-processing steps such as RCA cleaning, 24 h in de...

  5. 77 FR 26024 - Agency Information Collection Activities: Bonded Warehouse Proprietor's Submission

    Science.gov (United States)

    2012-05-02

    ... previously published in the Federal Register (77 FR 6814) on February 9, 2012, allowing for a 60-day comment... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Bonded Warehouse... approval in accordance with the Paperwork Reduction Act: Bonded Warehouse Proprietor's Submission (CBP...

  6. Quantum delocalization of protons in the hydrogen bond network of an enzyme active site

    CERN Document Server

    Wang, Lu; Boxer, Steven G; Markland, Thomas E

    2015-01-01

    Enzymes utilize protein architectures to create highly specialized structural motifs that can greatly enhance the rates of complex chemical transformations. Here we use experiments, combined with ab initio simulations that exactly include nuclear quantum effects, to show that a triad of strongly hydrogen bonded tyrosine residues within the active site of the enzyme ketosteroid isomerase (KSI) facilitates quantum proton delocalization. This delocalization dramatically stabilizes the deprotonation of an active site tyrosine residue, resulting in a very large isotope effect on its acidity. When an intermediate analog is docked, it is incorporated into the hydrogen bond network, giving rise to extended quantum proton delocalization in the active site. These results shed light on the role of nuclear quantum effects in the hydrogen bond network that stabilizes the reactive intermediate of KSI, and the behavior of protons in biological systems containing strong hydrogen bonds.

  7. Breastfeeding and Active Bonding Protects against Children’s Internalizing Behavior Problems

    Directory of Open Access Journals (Sweden)

    Jianghong Liu

    2013-12-01

    Full Text Available Breastfeeding is associated with numerous health benefits to offspring and mothers and may improve maternal-infant bonding. Ample evidence suggests breastfeeding can improve child neurodevelopment, but more research is needed to establish whether breastfeeding is linked to the development of child psychopathology. This paper aims to explore the effects of both breastfeeding and mother-child interactions on child behavioral outcomes at a later age. Children from the China Jintan Child Cohort Study (N = 1267, at age six years old were assessed, along with their parents. Children who were breastfed exclusively for a period of time in the presence of active bonding were compared to those who were breastfed in the absence of active bonding as well as to children who were not exclusively breastfed, with or without active bonding. Results from ANOVA and GLM, using SPSS20, indicate that children who were breastfed and whose mothers actively engaged with them displayed the lowest risk of internalizing problems (mean = 10.01, SD = 7.21, while those who were neither exclusively breastfed nor exposed to active bonding had the least protection against later internalizing problems (mean = 12.79, SD = 8.14. The effect of breastfeeding on internalizing pathology likely represents a biosocial and holistic effect of physiological, and nutritive, and maternal-infant bonding benefits.

  8. Mechanism and Selectivity of Ru(II) - and Rh(III) -Catalyzed Oxidative Spiroannulation of Naphthols and Phenols with Alkynes through a C-H Activation/Dearomatization Strategy.

    Science.gov (United States)

    Zhang, Mei; Huang, Genping

    2016-06-27

    The ruthenium- and rhodium-catalyzed oxidative spiroannulation of naphthols and phenols with alkynes was investigated by means of density functional theory calculations. The results show that the reaction undergoes O-H deprotonation/C(sp(2) )-H bond cleavage through a concerted metalation-deprotonation mechanism/migratory insertion of the alkyne into the M-C bond to deliver the eight-membered metallacycle. However, the dearomatization through the originally proposed enol-keto tautomerization/C-C reductive elimination was calculated to be kinetically inaccessible. Alternatively, an unusual metallacyclopropene, generated from the isomerization of the eight-membered metallacycle through rotation of the C-C double bond, was identified as a key intermediate to account for the experimental results. The subsequent C-C coupling between the carbene carbon atom and the carbon atom of the 2-naphthol/phenol ring was calculated to be relatively facile, leading to the formation of the unexpected dearomatized products. The calculations reproduce quite well the experimentally observed formal [5+2] cycloaddition in the rhodium-catalyzed oxidative annulation of 2-vinylphenols with alkynes. The calculations show that compared with the case of 2-alkenylphenols, the presence of conjugation effects and less steric repulsion between the phenol ring and the vinyl moiety make the competing reductive oxyl migration become dominant, which enables the selectivity switch from the spiroannulation to the formal [5+2] cycloaddition. PMID:27225930

  9. Access to novel fluorovinylidene ligands via exploitation of outer-sphere electrophilic fluorination: new insights into C-F bond formation and activation.

    Science.gov (United States)

    Milner, Lucy M; Hall, Lewis M; Pridmore, Natalie E; Skeats, Matthew K; Whitwood, Adrian C; Lynam, Jason M; Slattery, John M

    2016-01-19

    Metal vinylidene complexes are widely encountered, or postulated, as intermediates in a range of important metal-mediated transformations of alkynes. However, fluorovinylidene complexes have rarely been described and their reactivity is largely unexplored. By making use of the novel outer-sphere electrophilic fluorination (OSEF) strategy we have developed a rapid, robust and convenient method for the preparation of fluorovinylidene and trifluoromethylvinylidene ruthenium complexes from non-fluorinated alkynes. Spectroscopic investigations (NMR and UV/Vis), coupled with TD-DFT studies, show that fluorine incorporation results in significant changes to the electronic structure of the vinylidene ligand. The reactivity of fluorovinylidene complexes shows many similarities to non-fluorinated analogues, but also some interesting differences, including a propensity to undergo unexpected C-F bond cleavage reactions. Heating fluorovinylidene complex [Ru(η(5)-C5H5)(PPh3)2(C[double bond, length as m-dash]C{F}R)][BF4] led to C-H activation of a PPh3 ligand to form an orthometallated fluorovinylphosphonium ligand. Reaction with pyridine led to nucleophilic attack at the metal-bound carbon atom of the vinylidene to form a vinyl pyridinium species, which undergoes both C-H and C-F activation to give a novel pyridylidene complex. Addition of water, in the presence of chloride, leads to anti-Markovnikov hydration of a fluorovinylidene complex to form an α-fluoroaldehyde, which slowly rearranges to its acyl fluoride isomer. Therefore, fluorovinylidenes ligands may be viewed as synthetic equivalents of 1-fluoroalkynes providing access to reactivity not possible by other routes. PMID:26701305

  10. An intramolecular disulfide bond designed in myoglobin fine-tunes both protein structure and peroxidase activity.

    Science.gov (United States)

    Wu, Lei-Bin; Yuan, Hong; Zhou, Hu; Gao, Shu-Qin; Nie, Chang-Ming; Tan, Xiangshi; Wen, Ge-Bo; Lin, Ying-Wu

    2016-06-15

    Disulfide bond plays crucial roles in stabilization of protein structure and in fine-tuning protein functions. To explore an approach for rational heme protein design, we herein rationally introduced a pair of cysteines (F46C/M55C) into the scaffold of myoglobin (Mb), mimicking those in native neuroglobin. Molecular modeling suggested that it is possible for Cys46 and Cys55 to form an intramolecular disulfide bond, which was confirmed experimentally by ESI-MS analysis, DTNB reaction and CD spectrum. Moreover, it was shown that the spontaneously formed disulfide bond of Cys46-Cys55 fine-tunes not only the heme active site structure, but also the protein functions. The substitution of Phe46 with Ser46 in F46S Mb destabilizes the protein while facilitates H2O2 activation. Remarkably, the formation of an intramolecular disulfide bond of Cys46-Cys55 in F46C/M55C Mb improves the protein stability and regulates the heme site to be more favorable for substrate binding, resulting in enhanced peroxidase activity. This study provides valuable information of structure-function relationship for heme proteins regulated by an intramolecular disulfide bond, and also suggests that construction of such a covalent bond is useful for design of functional heme proteins. PMID:27117233

  11. Room temperature bonding of SiO2 and SiO2 by surface activated bonding method using Si ultrathin films

    Science.gov (United States)

    Utsumi, Jun; Ide, Kensuke; Ichiyanagi, Yuko

    2016-02-01

    The bonding of metal electrodes and insulator hybrid interfaces is one of the key techniques in three-dimensional integration technology. Metal materials such as Cu or Al are easily directly bonded by surface activated bonding at room temperature, but insulator materials such as SiO2 or SiN are not. Using only Si ultrathin films, we propose a new bonding technique for SiO2/SiO2 bonding at room temperature. Two SiO2 surfaces, on which Si thin films were deposited, were contacted in vacuum. We confirmed that the thickness of the layer was about 7 nm by transmission electron microscopy observation and that the layer was non crystalline by electron energy loss spectroscopy analysis. No metal material was found in the bonding interface by energy-dispersive X-ray spectroscopy analysis. The surface energy was about 1 J/m2, and the bonding strength was more than 25 MPa. This bonding technique was successfully realized to enable SiO2/SiO2 bonding without a metal adhesion layer.

  12. C–H Bond Activation at Palladium(IV) Centers

    OpenAIRE

    Racowski, Joy M.; Ball, Nicholas D.; Sanford, Melanie S.

    2011-01-01

    This communication describes the first observation and study of C–H activation at a PdIV center. This transformation was achieved by designing model complexes in which the rate of reductive elimination is slowed relative to that of the desired C–H activation process. Remarkably, the C–H activation reaction can proceed under mild conditions and with complementary site selectivity to analogous transformations at PdII. These results provide a platform for incorporating this new reaction as a ste...

  13. Carbon dioxide utilization via carbonate-promoted C-H carboxylation

    Science.gov (United States)

    Banerjee, Aanindeeta; Dick, Graham R.; Yoshino, Tatsuhiko; Kanan, Matthew W.

    2016-03-01

    Using carbon dioxide (CO2) as a feedstock for commodity synthesis is an attractive means of reducing greenhouse gas emissions and a possible stepping-stone towards renewable synthetic fuels. A major impediment to synthesizing compounds from CO2 is the difficulty of forming carbon-carbon (C-C) bonds efficiently: although CO2 reacts readily with carbon-centred nucleophiles, generating these intermediates requires high-energy reagents (such as highly reducing metals or strong organic bases), carbon-heteroatom bonds or relatively acidic carbon-hydrogen (C-H) bonds. These requirements negate the environmental benefit of using CO2 as a substrate and limit the chemistry to low-volume targets. Here we show that intermediate-temperature (200 to 350 degrees Celsius) molten salts containing caesium or potassium cations enable carbonate ions (CO32-) to deprotonate very weakly acidic C-H bonds (pKa > 40), generating carbon-centred nucleophiles that react with CO2 to form carboxylates. To illustrate a potential application, we use C-H carboxylation followed by protonation to convert 2-furoic acid into furan-2,5-dicarboxylic acid (FDCA)—a highly desirable bio-based feedstock with numerous applications, including the synthesis of polyethylene furandicarboxylate (PEF), which is a potential large-scale substitute for petroleum-derived polyethylene terephthalate (PET). Since 2-furoic acid can readily be made from lignocellulose, CO32--promoted C-H carboxylation thus reveals a way to transform inedible biomass and CO2 into a valuable feedstock chemical. Our results provide a new strategy for using CO2 in the synthesis of multi-carbon compounds.

  14. C-ON Bond Homolysis of Alkoxyamines, Part 11: Activation of the Nitroxyl Fragment.

    Science.gov (United States)

    Audran, Gérard; Brémond, Paul; Marque, Sylvain R A; Yamasaki, Toshihide

    2016-03-01

    A few years ago, Bagryanskaya and colleagues (J. Org. Chem. 2011) showed that protonation of the nitroxyl fragment deactivated the alkoxyamine C-ON bond. Conversely, our group showed that protonation (Chem. Commun. 2011), as well as other chemical reactions such as oxidation or amine quaternization (Org. Lett. 2012), of the pyridyl moiety carried by the alkyl fragment was suitable to activate the homolysis of the C-ON bond. To pursue our goal of applying alkoxyamines as theranostic agents (Org. Biomol. Chem. 2014 and Mol. Pharmaceutics 2014) by activation of the C-ON bond homolysis, we turned our interest to the chemical activation of the nitroxyl fragment by oxidation/reduction of selected functions. Conversion of a hydroxyl group located close to the nitroxyl moiety successively into aldehyde, then acid, and eventually into ester, led to a successive decrease in kd. PMID:26878593

  15. 29 CFR 2580.412-8 - The nature of the duties or activities to which the bonding requirement relates.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false The nature of the duties or activities to which the bonding requirement relates. 2580.412-8 Section 2580.412-8 Labor Regulations Relating to Labor (Continued) EMPLOYEE... INCOME SECURITY ACT OF 1974 TEMPORARY BONDING RULES Scope and Form of the Bond § 2580.412-8 The nature...

  16. The road to the first, fully active and more stable human insulin variant with an additional disulfide bond

    DEFF Research Database (Denmark)

    Vinther, Tine N.; Kjeldsen, Thomas B.; Jensen, Knud Jørgen;

    2015-01-01

    addressed the question whether a human insulin variant with four disulfide bonds could exist and be fully functional. In this review, we give an overview of the road to engineering four-disulfide bonded insulin analogs. During our journey, we discovered several active four disulfide bonded insulin analogs...

  17. Polymeric thermal analysis of C + H and C + H + Ar ion implanted UHMWPE samples

    International Nuclear Information System (INIS)

    Chemical surface characterization of C + H hybrid ion implanted UHMWPE samples were carried out using DSC (differential scanning calorimeter) and TGA (thermal gravimetric analysis) techniques. Samples were implanted with a fluence of 1017 ion/cm2 and an extraction voltage of 30 kV. The study of TGA and DSC curves showed that: (1) Polymeric decomposition temperature increased (2) T m, ΔC p and ΔH m values changed while ΔC p and ΔH m increased. T g value could not be measured, because of some experimental limitations. However, the increase in ΔH m values showed that T g values increased (3) the branch density which indicated the increase in number of cross-link (M c) decreased in ion implanted samples and (4) increase in ΔH m values indicated increase in crystallinity of implanted surface of UHMWPE samples

  18. Intramolecular cyclopropanation and C-H insertion reactions with metal carbenoids generated from cyclopropenes.

    Science.gov (United States)

    Archambeau, Alexis; Miege, Frédéric; Meyer, Christophe; Cossy, Janine

    2015-04-21

    Activation of unsaturated carbon-carbon bonds by means of transition metal catalysts is an exceptionally active research field in organic synthesis. In this context, due to their high ring strain, cyclopropenes constitute an interesting class of substrates that displays a versatile reactivity in the presence of transition metal catalysts. Metal complexes of vinyl carbenes are involved as key intermediates in a wide variety of transition metal-catalyzed ring-opening reactions of cyclopropenes. Most of the reported transformations rely on intermolecular or intramolecular addition of nucleophiles to these latter reactive species. This Account focuses specifically on the reactivity of carbenoids resulting from the ring-opening of cyclopropenes in cyclopropanation and C-H insertion reactions, which are arguably two of the most representative transformations of metal complexes of carbenes. Compared with the more conventional α-diazo carbonyl compounds, the use of cyclopropenes as precursors of metal carbenoids in intramolecular cyclopropanation or C-H insertion reactions has been largely underexploited. One of the challenges is to devise appropriately substituted and readily available cyclopropenes that would not only undergo regioselective ring-opening under mild conditions but also trigger the subsequent desired transformations with a high level of chemoselectivity and stereoselectivity. These goals were met by considering several substrates derived from the readily available 3,3-dimethylcyclopropenylcarbinols or 3,3-dimethylcyclopropenylcarbinyl amines. In the case of 1,6-cyclopropene-enes, highly efficient and diastereoselective gold(I)-catalyzed ring-opening/intramolecular cyclopropanations were developed as a route to diversely substituted heterocycles and carbocycles possessing a bicyclo[4.1.0]heptane framework. The use of rhodium(II) catalysts enabled us to widen the scope of this transformation for the synthesis of medium-sized heterocyclic scaffolds

  19. Effect of bonding on the performance of a piezoactuator-based active control system

    Science.gov (United States)

    Baz, A.; Poh, S.

    1987-01-01

    The utilization of piezoelectric actuators in controlling the structural vibrations of flexible beams is studied. A Modified Independent Modal Space Control (MIMSC) method is devised to select the optimal location, control gains and excitation voltage of the piezoelectric actuators in a way that would minimize the amplitudes of vibrations of beams to which these actuators are bonded, as well as the input control energy necessary to suppress these vibrations. The presented method accounts for the effects that the piezoelectric actuators and the bonding layers have on changing the elastic and inertial properties of the flexible beams. Numerical examples are presented to illustrate the application of the MIMSC method and to demonstrate the effect of the physical and geometrical properties of the bonding layer on the dynamic performance of the actively controlled beams. The obtained results emphasize the importance of the devised method in designing more realistic active control systems for flexible beams, in particular, and large flexible structures in general.

  20. Effect of different irrigant activation protocols on push-out bond strength.

    Science.gov (United States)

    Akyuz Ekim, Sefika Nur; Erdemir, Ali

    2015-11-01

    The study aimed to evaluate the effect of various final irrigant activation protocols on push-out bond strength of fiber post. Thirty-two single-rooted human maxillar central teeth were sectioned below the cementoenamel junction, instrumented and obturated. Post-space preparation was performed, and roots were randomly divided into eight groups (n = 4) according to the final irrigant activation protocols; distilled water was used as an irrigant in group 1. The other groups were treated with 2.5% NaOCl and 17% EDTA. Conventional syringe irrigation (CSI, no activation) was used in group 2. Irrigation solutions were activated using passive ultrasonic irrigation (PUI, group 3), EndoVac apical negative pressure (ANP, group 4), diode laser (group 5), neodymium:yttrium-aluminum-garnet (Nd:YAG) laser (group 6), erbium:yttrium-aluminum-garnet (Er:YAG) laser (group 7), and Er:YAG laser using with photon-induced photoacoustic streaming (PIPS™) technique (group 8). In all groups, fiber posts (White Post DC, FGM) were luted using Panavia F 2.0 (Kuraray, Osaka, Japan). The specimens were transversally sectioned, and all slices from coronal and apical regions were subjected to push-out tests. The data were calculated as megapascals and analyzed by using two-way analysis of variance followed by post hoc Tukey honestly significant difference (HSD) tests. Removing the smear layer increased the bond strength to dentine when compared with the control group (p < 0.05). The highest bond strength was obtained in the PIPS laser-activated irrigation group (p < 0.05). Coronal root region presented significantly higher bond strength than the apical region (p < 0.05). PIPS laser-activated irrigation showed higher efficiency as a final irrigant activation protocol on push-out bond strength of fiber post. PMID:26022731

  1. Effects of metal ions and disulfide bonds on the activity of phosphodiesterase from Trimeresurus stejnegeri venom.

    Science.gov (United States)

    Peng, Lili; Xu, Xiaolong; Guo, Mingchun; Yan, Xincheng; Wang, Shasha; Gao, Shang; Zhu, Shanshan

    2013-06-01

    Obviously different from the other known phosphodiesterases, the phosphodiesterase from Trimeresurus stejnegeri venom (TS-PDE) consists of two different chains linked with disulfide bonds and contains both endogenous Cu(2+) and Zn(2+). Cu(2+) and Zn(2+) are important for its phosphodiesterase activity. In this study, the effects of metal ions and small-molecule reductants on its structure and activity have been investigated by polyacrylamide gel electrophoresis, high performance liquid chromatography, fluorescence and electron paramagnetic resonance spectroscopy. The results show that TS-PDE has one class of Zn(2+) binding site and two classes of Cu(2+) binding site, including the high affinity activator sites and the low affinity sites. Cu(2+) ions function as a switch for its phosphodiesterase activity. The catalytic activity of TS-PDE does not have an absolute requirement for Cu(2+) and Zn(2+). Mg(2+), Mn(2+), Ni(2+), Co(2+) and Ca(2+) are all effective for its phosphodiesterase activity. TS-PDE has seven disulfide bonds and ten free cysteine residues. l-Ascorbate inhibits the phosphodiesterase activity of TS-PDE through reduction of the Cu(2+), while dithiothreitol, glutathione and tris(2-carboxyethyl)phosphine inhibit the phosphodiesterase activity of TS-PDE by reducing both the Cu(2+) and disulfide bonds. The catalytic activity of TS-PDE relies on its disulfide bonds and bimetallic cluster. In addition, biologically-relevant reductants, glutathione and l-ascorbate, have been found to be endogenous inhibitors to the phosphodiesterase activity of TS-PDE. PMID:23775423

  2. Polyketide Construction via Hydrohydroxyalkylation and Related Alcohol C-H Functionalizations: Reinventing the Chemistry of Carbonyl Addition

    OpenAIRE

    Dechert-Schmitt, Anne-Marie R.; Schmitt, Daniel C.; Xin GAO; Itoh, Takahiko; Krische, Michael J.

    2014-01-01

    Despite the longstanding importance of polyketide natural products in human medicine, nearly all commercial polyketide-based drugs are prepared through fermentation or semi-synthesis. The paucity of manufacturing routes involving de novo chemical synthesis reflects the inability of current methods to concisely address the preparation of these complex structures. Direct alcohol C-H bond functionalization via “C-C bond forming transfer hydrogenation” provides a powerful, new means of constructi...

  3. An activated triple bond linker enables 'click' attachment of peptides to oligonucleotides on solid support

    OpenAIRE

    Wenska, Malgorzata; Alvira, Margarita; Steunenberg, Peter; Stenberg, Åsa; Murtola, Merita; Strömberg, Roger

    2011-01-01

    A general procedure, based on a new activated alkyne linker, for the preparation of peptide–oligonucleotide conjugates (POCs) on solid support has been developed. With this linker, conjugation is effective at room temperature (RT) in millimolar concentration and submicromolar amounts. This is made possible since the use of a readily attachable activated triple bond linker enhances the Cu(I) catalyzed 1,3-dipolar cycloaddition (‘click’ reaction). The preferred scheme for conjugate preparation ...

  4. Amidines for Versatile Cobalt(III)-Catalyzed Synthesis of Isoquinolines through C-H Functionalization with Diazo Compounds.

    Science.gov (United States)

    Li, Jie; Tang, Mengyao; Zang, Lei; Zhang, Xiaolei; Zhang, Zhao; Ackermann, Lutz

    2016-06-01

    A cobalt(III)-catalyzed C-H/N-H bond functionalization for the synthesis of 1-aminoisoquinolines from aryl amidines and diazo compounds has been developed. The reaction proceeds under mild reaction conditions, obviates the need for oxidants, produces only N2 and H2O as the byproducts, and features a broad substrate scope. PMID:27219713

  5. Selective Synthesis of Isoquinolines by Rhodium(III)-Catalyzed C-H/N-H Functionalization with α-Substituted Ketones.

    Science.gov (United States)

    Li, Jie; Zhang, Zhao; Tang, Mengyao; Zhang, Xiaolei; Jin, Jian

    2016-08-01

    A rhodium(III)-catalyzed C-H/N-H bond functionalization for the synthesis of 1-aminoisoquinolines from aryl amidines and α-MsO/TsO/Cl ketones was achieved under mild reaction conditions. Thus, this approach provides a practical method for the site-selective synthesis of various synthetically valuable isoquinolines with wide functional group tolerance. PMID:27441726

  6. Bond slip detection of concrete-encased composite structure using shear wave based active sensing approach

    Science.gov (United States)

    Zeng, Lei; Parvasi, Seyed Mohammad; Kong, Qingzhao; Huo, Linsheng; Lim, Ing; Li, Mo; Song, Gangbing

    2015-12-01

    Concrete-encased composite structure exhibits improved strength, ductility and fire resistance compared to traditional reinforced concrete, by incorporating the advantages of both steel and concrete materials. A major drawback of this type of structure is the bond slip introduced between steel and concrete, which directly reduces the load capacity of the structure. In this paper, an active sensing approach using shear waves to provide monitoring and early warning of the development of bond slip in the concrete-encased composite structure is proposed. A specimen of concrete-encased composite structure was investigated. In this active sensing approach, shear mode smart aggregates (SAs) embedded in the concrete act as actuators and generate desired shear stress waves. Distributed piezoceramic transducers installed in the cavities of steel plates act as sensors and detect the wave response from shear mode SAs. Bond slip acts as a form of stress relief and attenuates the wave propagation energy. Experimental results from the time domain analysis clearly indicate that the amplitudes of received signal by lead zirconate titanate sensors decreased when bond slip occurred. In addition, a wavelet packet-based analysis was developed to compute the received signal energy values, which can be used to determine the initiation and development of bond slip in concrete-encased composite structure. In order to establish the validity of the proposed method, a 3D finite element analysis of the concrete-steel bond model is further performed with the aid of the commercial finite element package, Abaqus, and the numerical results are compared with the results obtained in experimental study.

  7. A Systematic Study of Structure and E-H Bond Activation Chemistry by Sterically Encumbered Germylene Complexes.

    Science.gov (United States)

    Usher, Matthew; Protchenko, Andrey V; Rit, Arnab; Campos, Jesús; Kolychev, Eugene L; Tirfoin, Rémi; Aldridge, Simon

    2016-08-01

    A series of new germylene compounds has been synthesized offering systematic variation in the σ- and π-capabilities of the α-substituent and differing levels of reactivity towards E-H bond activation (E=H, B, C, N, Si, Ge). Chloride metathesis utilizing [(terphenyl)GeCl] proves to be an effective synthetic route to complexes of the type [(terphenyl)Ge(ERn )] (1-6: ERn =NHDipp, CH(SiMe3 )2 , P(SiMe3 )2 , Si(SiMe3 )3 or B(NDippCH)2 ; terphenyl=C6 H3 Mes2 -2,6=Ar(Mes) or C6 H3 Dipp2 -2,6=Ar(Dipp) ; Dipp=C6 H3 iPr2 -2,6, Mes=C6 H2 Me3 -2,4,6), while the related complex [{(Me3 Si)2 N}Ge{B(NDippCH)2 }] (8) can be accessed by an amide/boryl exchange route. Metrical parameters have been probed by X-ray crystallography, and are consistent with widening angles at the metal centre as more bulky and/or more electropositive substituents are employed. Thus, the widest germylene units (θ>110°) are found to be associated with strongly σ-donating boryl or silyl ancillary donors. HOMO-LUMO gaps for the new germylene complexes have been appraised by DFT calculations. The aryl(boryl)-germylene system [Ar(Mes) Ge{B(NDippCH)2 }] (6-Mes), which features a wide C-Ge-B angle (110.4(1)°) and (albeit relatively weak) ancillary π-acceptor capabilities, has the smallest HOMO-LUMO gap (119 kJ mol(-1) ). These features result in 6-Mes being remarkably reactive, undergoing facile intramolecular C-H activation involving one of the mesityl ortho-methyl groups. The related aryl(silyl)-germylene system, [Ar(Mes) Ge{Si(SiMe3 )3 }] (5-Mes) has a marginally wider HOMO-LUMO gap (134 kJ mol(-1) ), rendering it less labile towards decomposition, yet reactive enough to oxidatively cleave H2 and NH3 to give the corresponding dihydride and (amido)hydride. Mixed aryl/alkyl, aryl/amido and aryl/phosphido complexes are unreactive, but amido/boryl complex 8 is competent for the activation of E-H bonds (E=H, B, Si) to give hydrido, boryl and silyl products. The results of these reactivity studies

  8. Silver(I) NHC mediated C-C bond activation of alkyl nitriles and catalytic efficiency in oxazoline synthesis.

    Science.gov (United States)

    Heath, Rachael; Müller-Bunz, Helge; Albrecht, Martin

    2015-05-21

    Preparation of silver triazolylidene (trz) species from triazolium salts and Ag2O in refluxing MeCN leads to a selective C-C bond cleavage and the formation of complexes of general formula [(trz)Ag(CN)] from Calkyl-CN bond activation. Moreover, these silver carbene complexes are precursors of highly active catalysts for oxazoline formation via aldol condensation. PMID:25913007

  9. The active site of hen egg-white lysozyme: flexibility and chemical bonding

    International Nuclear Information System (INIS)

    Chemical bonding at the active site of lysozyme is analyzed on the basis of a multipole model employing transferable multipole parameters from a database. Large B factors at low temperatures reflect frozen-in disorder, but therefore prevent a meaningful free refinement of multipole parameters. Chemical bonding at the active site of hen egg-white lysozyme (HEWL) is analyzed on the basis of Bader’s quantum theory of atoms in molecules [QTAIM; Bader (1994 ▶), Atoms in Molecules: A Quantum Theory. Oxford University Press] applied to electron-density maps derived from a multipole model. The observation is made that the atomic displacement parameters (ADPs) of HEWL at a temperature of 100 K are larger than ADPs in crystals of small biological molecules at 298 K. This feature shows that the ADPs in the cold crystals of HEWL reflect frozen-in disorder rather than thermal vibrations of the atoms. Directly generalizing the results of multipole studies on small-molecule crystals, the important consequence for electron-density analysis of protein crystals is that multipole parameters cannot be independently varied in a meaningful way in structure refinements. Instead, a multipole model for HEWL has been developed by refinement of atomic coordinates and ADPs against the X-ray diffraction data of Wang and coworkers [Wang et al. (2007), Acta Cryst. D63, 1254–1268], while multipole parameters were fixed to the values for transferable multipole parameters from the ELMAM2 database [Domagala et al. (2012), Acta Cryst. A68, 337–351] . Static and dynamic electron densities based on this multipole model are presented. Analysis of their topological properties according to the QTAIM shows that the covalent bonds possess similar properties to the covalent bonds of small molecules. Hydrogen bonds of intermediate strength are identified for the Glu35 and Asp52 residues, which are considered to be essential parts of the active site of HEWL. Furthermore, a series of weak C

  10. Measurement of the C/H ratio by neutrons

    International Nuclear Information System (INIS)

    A probe consisting of a Ra (α, n) Be neutron source and a boron-trifluoride-filled proportional counter were used for measuring the C/H ratio in hydrocarbons. The intensity of the thermal-neutron flux near the counter increases in proportion to the increase of the hydrogen concentration in the hydrocarbon surrounding the probe. The C/H ratio is found by measuring the density. The C/H ratio can be estimated as accurately by this method as by β-particle transmission. The errors resulting from the chemical nature of the hydrocarbon can be reduced to a minimum. The advantage of this method is that it renders possible an external measurement of the C/H ratio of hydrocarbons contained in steel vessels or thick steel piping by means of a portable apparatus. (author)

  11. Cobalt-Mediated Vinylic C-H Functionalization of Alkenes

    OpenAIRE

    Boyd, Warren Christopher

    2012-01-01

    The reaction of cobalt dinitrosyl complexes with alkenes to form cobalt dinitrosoalkane complexes is used to effect the C-H functionalization of alkenes. Deprotonation of cobalt dinitrosoalkane complexes, followed by reaction with neutral electrophiles, yields functionalized cobalt complexes. Thermolysis of such complexes with the parent alkene allows a migration of the cobalt dinitrosyl moiety to the parent alkene, releasing the organic product of C-H functionalization. Progress is presented...

  12. C-H Bond Activation of Bisimines by Palladium (Ⅱ) and Platinum (Ⅱ).Synthesis,Characterization of Bis (imino) aryl-palladium (Ⅱ) Pincer Complexes and Their Application in Carbon-Carbon Cross Coupling Reactions%C-H Bond Activation of Bisimines by Palladium (Ⅱ) and Platinum (Ⅱ).Synthesis, Characterization of Bis (imino) aryl-palladium (Ⅱ) Pincer Complexes and Their Application in Carbon-Carbon Cross Coupling Reactions

    Institute of Scientific and Technical Information of China (English)

    CHEN Rong; CHEN Ying; LIU Fang; LI Ping; HU Zhao-xia; WANG Hong-xing

    2013-01-01

    Abstract:The reactions of a variety of 4,6-dimethyl-1,3-bis (imino) benzenes 2a-g derived from 4,6-dimethylisophthalaldehyde and anilines or benzylamine with palladium (Ⅱ) acetate in anhydrous acetic acid under nitrogen were investigated.Experiment results demonstrate that cyclopalladations in such condition are applicable not only to the present system under study but also to the 5-substituted bis(imino)benzenes 6,7.The molecular structure of 3 b was further confirmed by X-Ray single-crystal diffraction.3b Crystallizes in orthorhombic,space groupP2 (1) 2 (1) 2 (1) with a =0.734 53 (8),b =1.683 8 (3),c =1.691 7(2) nm,α =β =γ =90°.Treatment of 2b with K2PtCl4 in anhydrous acetic acid affords the corresponding NCN-platinum pincer.Carbon-carbon cross coupling reactions catalyzed with 3b were investigated.These palladium complexes have been proved to be high effective catalysts for Suzuki coupling reaction.

  13. RIR MAPLE procedure for deposition of carbon rich Si/C/H films

    International Nuclear Information System (INIS)

    We applied the resonant infrared matrix assisted pulsed laser evaporation (RIR MAPLE) technique to demonstrate a new approach to a controlled deposition of carbon rich amorphous Si/C/H film. In absence of radicals and accelerated species commonly generated in PECVD and sputtering setups, the RIR MAPLE method does not decompose precursor molecules. Moreover, unlike the standard MAPLE procedure, in which solvent molecules absorb laser energy from excimer or near infrared lasers, we applied the pulsed TEA CO2 laser to excite the dendrimer precursor molecules in a frozen target. In this manner we achieved just cross-linking of the starting precursor on substrates and the deposition of carbon rich Si/C/H film. The film was analyzed by Fourier Transformed Infrared (FTIR), UV/VIS, Raman and X-ray Photoelectron (XPS) spectroscopy and Atomic Force Microscopy (AFM) technique. According to analyses the film retained the precursor elemental composition free of graphitic (sp2) clusters. In course of reaction only the peripheral allyl groups containing C=C bonds were opened to achieve cross-linking. Whereas annealing to 300 °C was necessary for the elimination of =C–H1, 2 bonds in the films prepared at 200 °C, those bonds vanished completely for the films prepared at substrate temperature 255 °C. The film posseses a smooth surface with root mean square (RMS) parameter up to 10 nm within scanned distance 2.5 μm.

  14. Improvement of silicon direct bonding using surfaces activated by hydrogen plasma treatment

    CERN Document Server

    Choi, W B; Lee Jae Sik; Sung, M Y

    2000-01-01

    The plasma surface treatment, using hydrogen gas, of silicon wafers was studied as a pretreatment for silicon direct bonding. Chemical reactions of the hydrogen plasma with the surfaces were used for both surface activation and removal of surface contaminants. Exposure of the silicon wafers to the plasma formed an active oxide layer on the surface. This layer was hydrophilic. The surface roughness and morphology were examined as functions of the plasma exposure time and power. The surface became smoother with shorter plasma exposure time and lower power. In addition, the plasma surface treatment was very efficient in removing the carbon contaminants on the silicon surface. The value of the initial surface energy, as estimated by using the crack propagation method, was 506 mJ/M sup 2 , which was up to about three times higher than the value for the conventional direct bonding method using wet chemical treatments.

  15. Predicting the activation energy of catalytic dissociation of the heteroatomic AB bond

    International Nuclear Information System (INIS)

    Two analytical formalisms, adiabatic and diabatic ones, were developed for the description of catalytic dissociation of heteroatomic bond AB interacting with a metal surface in the adsorption processes. In the adiabatic formalism, the transition state was localized on a four-dimensional potential energy surface in classical approximation. This approach generalizes the previous three-dimensional model for dissociative adsorption of homonuclear molecules X2 on metals surfaces, and it was used for studying the effect of non-parallel orientation to a surface of O2 molecules in the adsorption precursor state. The second formalism takes into account a possible quantum character of vibrations along the chemical bond AB. The calculation of the activation energy in this approach is performed by the density matrix method. This approach is applied for studying catalytic dissociation of CO molecule on a Ni(1 1 1) surface. The calculated apparent activation energy for this reaction is compared with published data for this system

  16. Palladium-Catalyzed C–C Bond Formations via Activation of Carboxylic Acids and Their Derivatives

    OpenAIRE

    Song, Bingrui

    2013-01-01

    Applications of carboxylic acids and their derivatives in transition metal-catalyzed cross-coupling reactions regio-selectively forming Csp3-Csp2, and Csp2-Csp2 bonds were explored in this thesis. Several important organic building blocks such as aryl acetates, diaryl acetates, imines, ketones, biaryls, styrenes and polysubstituted alkenes were successfully accessed from carboxylic acids and their derivatives by the means of C–H activation and decarboxylative cross-couplings. An efficient ...

  17. Sphalerite is a geochemical catalyst for carbon−hydrogen bond activation

    OpenAIRE

    Shipp, Jessie A.; Gould, Ian R.; Shock, Everett L.; Williams, Lynda B.; Hartnett, Hilairy E.

    2014-01-01

    Organic compound transformations in the Earth commonly take place in the presence of minerals and aqueous solutions, but a mechanistic understanding of how minerals influence hydrothermal organic reactivity is virtually nonexistent. We present the first description of mineral catalysis of a fundamental organic reaction—carbon−hydrogen bond activation. The discovery that a common mineral, sphalerite (ZnS), can readily accomplish this reaction will interest not only geochemists but also the org...

  18. Dentin Bond Strength of Two One-Bottle Adhesives after Delayed Activation of Light-Cured Resin Composites

    Directory of Open Access Journals (Sweden)

    F. Shafiei

    2007-12-01

    Full Text Available Objective: Adverse surface interactions between one-bottle adhesives and chemical-cured composites may occur with delayed light activation of light-cured composites. The purpose of this study was to assess the Effects of delayed activation of light-cured compositeson shear bond strength of two one-bottle adhesives with different acidity to bovine dentin.Materials and Methods: Flat dentin surface was prepared on sixty-six bovine incisors using 600 grit carbide papers. Prime&Bond NT, and One-Step adhesives and resin composite were applied in six groups: 1 immediate curing of the composite, 2 the composite was left 2.5 minutes over the cured adhesive before light activation, 3 prior to delayed activation of the composite, the cured adhesive was covered with a layer of nonacidic hydrophobic porcelain bonding resin (Choice 2 and cured immediately. After thermocycling,shear bond strength (SBS test was performed using a universal testing machine at 1 mm/min crosshead speed. Data were analyzed with Friedmans two-way Non-parametric ANOVA.Results: The SBS of delayed activation of Prime&Bond was significantly lower than immediate activated (P<0.05. Decrease in the SBS of One-Step was not statistically significant after delayed activation. The SBS of delayed activation of Prime&Bond and One-Step with an additional resin layer was significantly higher than delayed activation (P<0.001.Conclusion: The bond strength of Prime&Bond might be compromised by the higher acidity of this adhesive during the 2.5 minutes delayed activation of light-cured composite.Addition of a layer of hydrophobic resin compensated the effect of delayed activation andimproved the bond strength.

  19. The dimers of glyoxal and acrolein with H 2O and HF: Negative intramolecular coupling and blue-shifted C-H stretch

    Science.gov (United States)

    Karpfen, Alfred; Kryachko, Eugene S.

    2010-04-01

    The structures and the vibrational spectra of the hydrogen-bonded complexes: glyoxal-H 2O, glyoxal-HF, acrolein-H 2O, and acrolein-HF, are investigated within the MP2/aug-cc-pVTZ computational approach. It is demonstrated that the calculated blue shifts of the C-H stretching frequencies in the glyoxal-H 2O complexes are only indirectly pertinent to hydrogen bonding to the C-H group. The comparison with the glyoxal-HF and the acrolein-HF complexes reveals that these blue shifts are a direct consequence of a negative intramolecular coupling between vicinal C dbnd O and C-H bonds in the aldehyde groups of isolated glyoxal and acrolein molecules. To support this interpretation, the halogen-bonded complexes glyoxal-BrF and acrolein-BrF are discussed.

  20. Local network structure of a-SiC:H and its correlation with dielectric function

    Science.gov (United States)

    Kageyama, Shota; Matsuki, Nobuyuki; Fujiwara, Hiroyuki

    2013-12-01

    The microscopic disordered structures of hydrogenated amorphous silicon carbide (a-Si1-xCx:H) layers with different carbon contents have been determined based on the correlations between the dielectric function in the ultraviolet/visible region and the local bonding states studied by high-sensitivity infrared attenuated total reflection spectroscopy. We find that the microscopic structure of the a-Si1-xCx:H layers fabricated by plasma-enhanced chemical vapor deposition shows a sharp structural transition at a boundary of x = 6.3 at. %. In the regime of x ≤ 6.3 at. %, (i) the amplitude of the a-SiC:H dielectric function reduces and (ii) the SiH2 content increases drastically with x, even though most of the C atoms are introduced into the tetrahedral sites without bonding with H. In the regime of x > 6.3 at. %, on the other hand, (i) the amplitude of the dielectric function reduces further and (ii) the concentration of the sp3 CHn (n = 2,3) groups increases. Moreover, we obtained the direct evidence that the sp2 C bonding state in the a-SiC matrix exists in the configuration of C = CH2 and the generation of the graphite-like C = CH2 unit suppresses the band gap widening significantly. At high C contents of x > 6.3 at. %, the a-SiC:H layers show quite porous structures due to the formation of microvoids terminated with the SiH2/CHn groups. By taking the SiH2/CHn microvoid generation in the network and the high-energy shift of the dielectric function by the local bonding states into account, the a-SiC:H dielectric function model has been established. From the analysis using this model, we have confirmed that the a-SiC:H optical properties in the ultraviolet/visible region are determined almost completely by the local network structures.

  1. C-H 活化策略高效合成新型吲哚[2,1-a]异喹啉化合物%Highly Efficient Synthesis of A Novel Indolo[2,1-a]isoquinoline Derivative via C-H Activation Strategy

    Institute of Scientific and Technical Information of China (English)

    王亮; 陈玉婷; 杜依娜; 顾昌翰; 彭望明

    2015-01-01

    The intermediate N-pyrimidyl-2-phenyl-indole was highly efficient synthesized with indole as raw material and the easily installable and removable pyrimidyl group as directing group.The C-H activation/ary-lation was the key step for the synthesis of N-pyrimidyl-2-phenyl-indole compound.After removal of the pyrim-idyl group under simple reaction conditions,the novel indolo[2,1-a]isoquinoline derivative could be successfully synthesized via C-H activation/cyclization.The optimal reaction conditions were established by examining the effect of oxidants and solvents.The gram-scale experiments was conducted under the optimal reaction condi-tions.The structures of all compounds were characterized by IR,NMR and HRMS.%以吲哚为原料,使用容易安置和移除的嘧啶基作为导向基团,以 C- H 活化/芳化反应为关键步骤,实现了中间体 N-嘧啶-2-苯基吲哚的高效合成。通过简便的方法移除该中间体上的嘧啶导向基团,以 C- H 活化/环化反应为关键步骤,实现了新型吲哚[2,1-a]异喹啉的构建。对 C-H 活化/芳化反应条件进行了优化,并在优化的反应条件下进行了该反应的放大量实验。所有化合物均采用 IR、NMR、HRMS 等多种谱学技术进行了结构表征。

  2. Allylic and benzylic sp3 C-H oxidation in water.

    Science.gov (United States)

    Ang, Wei Jie; Lam, Yulin

    2015-01-28

    A copper-catalyzed method for the oxidation of allylic and benzylic sp(3) C-H by aqueous tert-butyl hydroperoxide (T-Hydro) in water using a recyclable fluorous ligand has been developed. The reaction procedure is tolerant to additional functional groups and the fluorous ligand could be reused with little loss of catalytic activity. PMID:25412371

  3. Conformational preferences of heterochiral peptides. Crystal structures of heterochiral peptides Boc-(D) Val-(D) Ala-Leu-Ala-OMe and Boc-Val-Ala-Leu-(D) Ala-OMe--enhanced stability of beta-sheet through C-H...O hydrogen bonds.

    Science.gov (United States)

    Fabiola, G F; Bobde, V; Damodharan, L; Pattabhi, V; Durani, S

    2001-02-01

    The crystal structures of Boc-(D) Val-(D) Ala-Leu-Ala-OMe (vaLA) and Boc-Val-Ala-Leu-(D) Ala-OMe (VALa) have been determined. vaLA crystallises in space group P2(1),2(1),2(1), with a = 9.401 (4), b = 17.253 (5), c = 36.276 (9)A. V = 5,884 (3) A3, Z = 8, R = 0.086. VALa crystallises in space group P2(1) with a = 9.683 (9), b = 17.355 (7), c = 18.187 (9) A, beta = 95.84 (8) degrees , V = 3,040(4) A3, Z = 4, R = 0.125. There are two molecules in the asymmetric unit in antiparallel beta-sheet arrangement in both the structures. Several of the Calpha hydrogens are in hydrogen bonding contact with the carbonyl oxygen in the adjacent strand. An analysis of the observed conformational feature of D-chiral amino acid residues in oligopeptides, using coordinates of 123 crystal structures selected from the 1998 release of CSD has been carried out. This shows that all the residues except D-isoleucine prefer both extended and alphaL conformation though the frequence of occurence may not be equal. In addition to this, D-leucine, valine, proline and phenylalanine have assumed alphaR conformations in solid state. D-leucine has a strong preference for helical conformation in linear peptides whereas they prefer an extended conformation in cyclic peptides. PMID:11245253

  4. New Results on Plasma Activated Bonding of Imprinted Polymer Features for Bio MEMS Applications

    International Nuclear Information System (INIS)

    Nanoimprint Lithography is a well-acknowledged low cost, high resolution, large area 3D patterning process for polymers. It includes the most promising methods: high pressure hot embossing (HE) and UV-Nanoimprint Lithography (UV-NIL). Curing of the imprinted structures is either done by cooling down below the glass transition temperature of the thermoplastic polymer in case of HE or by subsequent UV-light exposure and cross-linking in case of UV-NIL. Both techniques allow rapid prototyping for high volume production of fully patterned substrates for a wide range of materials. The advantages of using polymer substrates over common Micro-Electro-Mechanical Systems (MEMS) processing materials like glass, silicon or quartz are: bio-compatible surfaces, easy manufacturability, low cost for high volume production, suitable for use in micro- and nano-fabrication, low conductivity, wide range of optical properties just to name a few. We will present experimental results on HE processes with PMMA as well as UV-NIL imprints in selected UV-curable resists. In the second part of the work we will describe the bonding techniques for packaging of the micro or nano structures. Packaging of the imprinted features is a key technology for a wide variety of field of applications: μ-TAS, biochemistry, micro-mixers, micro-reactors, electrophoresis cells, life science, micro-optical and nano-optical applications (switches) nanofluidics, data storage, etc. for features down to sub-100 nm range. Most bonding techniques for polymer use adhesives as intermediate layers. We will demonstrate a promising technique for dense and very strong bonds using plasma activation of polymers and glass. This bonding technology allows for bonding at low temperatures well below the glass transition temperature of the polymers, which will ensure that the structures are not deformed

  5. Why Static O-H Bond Parameters Cannot Characterize the Free Radical Scavenging Activity of Phenolic Antioxidants: ab initio Study

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The static O-H bond parameters including O-H bond length, O-H charge difference, O-H Mulliken population and O-H bond stretching force constant (k) for 17 phenols were calculated by ab initio method HF/6-31G**. In combination with the O-H bond dissociation enthalpies (BDE) of the phenols determined by experiment, it was found that there were poor correlationships between the static O-H bond parameters and O-H BDE. Considering the good correlationship between O-H BDE and logarithm of free radical scavenging rate constant for phenolic antioxidant, it is reasonable to believe that the ineffectiveness of static O-H bond parameters in characterizing antioxidant activity arises from the fact that they cannot measure the O-H BDE.

  6. Importance of the oxygen bond strength for catalytic activity in soot oxidation

    DEFF Research Database (Denmark)

    Christensen, Jakob M.; Grunwaldt, Jan-Dierk; Jensen, Anker D.

    2016-01-01

    (loose contact) the rate constants for a number of catalytic materials outline a volcano curve when plotted against their heats of oxygen chemisorption. However, the optima of the volcanoes correspond to different heats of chemisorption for the two contact situations. In both cases the activation...... oxidation. The optimum of the volcano curve in loose contact is estimated to occur between the bond strengths of α-Fe2O3 and α-Cr2O3. Guided by an interpolation principle FeaCrbOx binary oxides were tested, and the activity of these oxides was observed to pass through an optimum for an FeCr2Ox binary oxide...

  7. Atomic and electronic structures of a-SiC:H from tight-binding molecular dynamics

    CERN Document Server

    Ivashchenko, V I; Shevchenko, V I; Ivashchenko, L A; Rusakov, G V

    2003-01-01

    The atomic and electronic properties of amorphous unhydrogenated (a-SiC) and hydrogenated (a-SiC:H) silicon carbides are studied using an sp sup 3 s sup * tight-binding force model with molecular dynamics simulations. The parameters of a repulsive pairwise potential are determined from ab initio pseudopotential calculations. Both carbides are generated from dilute vapours condensed from high temperature, with post-annealing at low temperature for a-SiC:H. A plausible model for the inter-atomic correlations and electronic states in a-SiC:H is suggested. According to this model, the formation of the amorphous network is weakly sensitive to the presence of hydrogen. Hydrogen passivates effectively only the weak bonds of threefold-coordinated atoms. Chemical ordering is very much affected by the cooling rate and the structure of the high-temperature vapour. The as-computed characteristics are in rather good agreement with the results for a-SiC and a-Si:H from ab initio calculations.

  8. Chelation-assisted Pd-catalysed ortho-selective oxidative C-H/C-H cross-coupling of aromatic carboxylic acids with arenes and intramolecular Friedel-Crafts acylation: one-pot formation of fluorenones.

    Science.gov (United States)

    Sun, Denan; Li, Bijin; Lan, Jingbo; Huang, Quan; You, Jingsong

    2016-03-01

    Pd-Catalysed ortho-selective oxidative C-H/C-H cross-coupling of aromatic carboxylic acids with arenes and subsequent intramolecular Friedel-Crafts acylation has been accomplished for the first time through a chelation-assisted C-H activation strategy. Starting from the readily available substrates, a variety of fluorenone derivatives are obtained in one pot. The direct use of naturally occurring carboxylic acid functionalities as directing groups avoids unnecessary steps for installation and removal of an extra directing group. PMID:26861768

  9. Theoretical study of lanthanide mono cation-mediated C-F bond activation

    International Nuclear Information System (INIS)

    Graphical abstract: Performing density functional B3LYP and multi-reference CASPT2 calculations, we found that all Ln+ reactions can be classified into one of two different reaction mechanisms, 'harpoon-like' and 'insertion-elimination', which were experimentally proposed by Cohrnel et al. and Konayagi et al., respectively. The two mechanisms have been proposed exclusive to each other. Our results show that both reaction mechanisms are possible in Ln+ reaction systems. Research highlights: → The lanthanide mono-cations (Ln+) activate C-F bond. → The C-F bond activation reactions with Ln+ proceed with two mechanisms, harpoon-like and insertion-elimination mechanisms. → Gd+ shows extremely high C-F bond activation ability. - Abstract: The potential energy surface corresponding to the reaction of lanthanide mono-cations (Ln+; Ln = Ce-Yb) with CH3F has been investigated using density functional theory calculations. In the initial step of the C-F activation reaction, Ln+ directly coordinates to the F atom of CH3F, and forms same [Ln...F...CH3]+ type transition state structures with an accompanying electron-transfer from the Ln+ to the F atom. Performing intrinsic reaction coordinate calculations from the transition states, we found that all Ln+ reactions can be classified into one of two different reaction mechanisms, 'harpoon-like' and 'insertion-elimination', which were experimentally proposed by Cohrnel et al. and Konayagi et al., respectively. The two mechanisms have been proposed exclusive to each other. Our results show that both reaction mechanisms are possible in Ln+ reaction systems.

  10. Water-containing hydrogen-bonding network in the active center of channelrhodopsin.

    Science.gov (United States)

    Ito, Shota; Kato, Hideaki E; Taniguchi, Reiya; Iwata, Tatsuya; Nureki, Osamu; Kandori, Hideki

    2014-03-01

    Channelrhodopsin (ChR) functions as a light-gated ion channel in Chlamydomonas reinhardtii. Passive transport of cations by ChR is fundamentally different from the active transport by light-driven ion pumps such as archaerhodopsin, bacteriorhodopsin, and halorhodopsin. These microbial rhodopsins are important tools for optogenetics, where ChR is used to activate neurons by light, while the ion pumps are used for neural silencing. Ion-transport functions by these rhodopsins strongly depend on the specific hydrogen-bonding networks containing water near the retinal chromophore. In this work, we measured protein-bound water molecules in a chimeric ChR protein of ChR1 (helices A to E) and ChR2 (helices F and G) of Chlamydomonas reinhardtii using low-temperature FTIR spectroscopy at 77 K. We found that the active center of ChR possesses more water molecules (9 water vibrations) than those of other microbial (2-6 water vibrations) and animal (6-8 water vibrations) rhodopsins. We conclude that the protonated retinal Schiff base interacts with the counterion (Glu162) directly, without the intervening water molecule found in proton-pumping microbial rhodopsins. The present FTIR results and the recent X-ray structure of ChR reveal a unique hydrogen-bonding network around the active center of this light-gated ion channel. PMID:24512107

  11. Si-H bond activation on Cu: Reaction of silane on Cu(111)

    Energy Technology Data Exchange (ETDEWEB)

    Wiegand, B.C.; Lohokare, S.P.; Nuzzo, R.G. (Univ. of Illinois, Urbana, IL (United States))

    1993-11-04

    The activation and decomposition of silane on Cu(111) have been studied using Fourier transform infrared (FTIR), Auger electron (AES), and temperature-programmed reaction (TPRS) spectroscopies, as well as low-energy electron diffraction (LEED). Silane dissociatively chemisorbs on Cu(111) at 90 K. Cleavage of the Si-H bond yields two structurally distinct adsorbed silyl fragments. Infrared spectroscopy identifies the predominant intermediates formed under these conditions as being adsorbed SiH[sub 2] and SiH species. The relative and absolute concentrations of these intermediates depend sensitively on the surface coverage of both Si and H, which themselves depend upon the silane exposure. SiH[sub 2] is stable over a wide range of coverage up to 180 K, where it then undergoes Si-H bond cleavage to form surface bound SiH. At higher temperatures, bond scission in the Si-H moiety results in the formation of adsorbed silicon atoms and the desorption of dihydrogen in a peak centered at [approximately]330 K. Auger electron spectra show that the amount of silicon deposited on the Cu(111) surface in this way is approximately one-third of the amount deposited on a stable Cu[sub 3]Si surface. This latter surface is readily formed by carrying out the silane exposure at temperatures above 300 K. 39 refs., 15 figs., 1 tab.

  12. Toward Efficient Palladium-Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Jensen, Thomas; Fristrup, Peter

    2009-01-01

    Recent breakthroughs have proved that direct palladium (II)-catalyzed allylic C-H alkylation can be achieved. This new procedure shows that the inherent requirement for a leaving group in the Tsuji-Trost palladium-catalyzed allylic alkylation can be lifted. These initial reports hold great promise...

  13. THERMODYNAMIC STUDIES OF HIGH TEMPERATURE EQUILIBRIA OF THE Si - N, Si - C - H AND Si - O - C - H SYSTEMS

    OpenAIRE

    Kostij, Ž.; Pavlovij, P.; Stefanovij, P.

    1990-01-01

    A model of system thermodynamic equilibrium and the obtained results in the temperature interval of 1000 [K] to 6000 [K] at p = const = 1 [bar] are presented for: 1) the Si-N system for Si3N4 synthesis from Si - powder in a nitrogen thermal arc plasma. 2) the Si-C-H system for SiC synthesis from Si-powder in a propane-butane thermal arc plasma (with added hydrogen) and 3) the Si-O-C-H system for SiC synthesis from SiO2-powder in a propane-butane thermal arc plasma (with added C-powder). The d...

  14. Properties of a-C:H:O plasma polymer films deposited from acetone vapors

    Energy Technology Data Exchange (ETDEWEB)

    Drabik, M., E-mail: martin.drabik@gmail.com [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland); Celma, C. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland); Kousal, J.; Biederman, H. [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, V Holešovičkách 2, 180 00 Prague 8 (Czech Republic); Hegemann, D. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland)

    2014-12-31

    To gain insight into the deposition and stability of oxygen-containing plasma polymer films, the properties of amorphous oxygenated hydrocarbon (a-C:H:O) plasma polymer coatings deposited from acetone vapors under various experimental conditions are investigated. Apart from the discharge power, the influence of the reactive carbon dioxide (CO{sub 2}) gas on the structure of the resulting films is studied. It is found by characterization using X-ray Photoelectron Spectroscopy and Fourier-Transform Infrared Spectroscopy that the experimental conditions particularly influence the amount of oxygen in the deposited a-C:H:O plasma polymer films. The O/C elemental ratio increases with increasing amount of CO{sub 2} in the working gas mixture (up to 0.2 for 24 sccm of CO{sub 2} at 30 W) and decreases with increasing RF discharge power (down to 0.17 for 50 W). Furthermore, the nature of bonds between the oxygen and carbon atoms has been examined. Only low amounts of double and triple bonded carbon are observed. This has a particular influence on the aging of the plasma polymer films which is studied both in ambient air and in distilled water for up to 4 months. Overall, stable a-C:H:O plasma polymer films are deposited comprising low amounts (up to about 5%) of ester/carboxyl groups. - Highlights: • Hydrocarbon plasma polymer films with variable oxygen content can be prepared. • Stable oxygenated hydrocarbon plasma polymers contain max 5% of ester/carboxyl groups. • Acetone-derived plasma polymer films can be used as permanent hydrophilic surfaces.

  15. Properties of a-C:H:O plasma polymer films deposited from acetone vapors

    International Nuclear Information System (INIS)

    To gain insight into the deposition and stability of oxygen-containing plasma polymer films, the properties of amorphous oxygenated hydrocarbon (a-C:H:O) plasma polymer coatings deposited from acetone vapors under various experimental conditions are investigated. Apart from the discharge power, the influence of the reactive carbon dioxide (CO2) gas on the structure of the resulting films is studied. It is found by characterization using X-ray Photoelectron Spectroscopy and Fourier-Transform Infrared Spectroscopy that the experimental conditions particularly influence the amount of oxygen in the deposited a-C:H:O plasma polymer films. The O/C elemental ratio increases with increasing amount of CO2 in the working gas mixture (up to 0.2 for 24 sccm of CO2 at 30 W) and decreases with increasing RF discharge power (down to 0.17 for 50 W). Furthermore, the nature of bonds between the oxygen and carbon atoms has been examined. Only low amounts of double and triple bonded carbon are observed. This has a particular influence on the aging of the plasma polymer films which is studied both in ambient air and in distilled water for up to 4 months. Overall, stable a-C:H:O plasma polymer films are deposited comprising low amounts (up to about 5%) of ester/carboxyl groups. - Highlights: • Hydrocarbon plasma polymer films with variable oxygen content can be prepared. • Stable oxygenated hydrocarbon plasma polymers contain max 5% of ester/carboxyl groups. • Acetone-derived plasma polymer films can be used as permanent hydrophilic surfaces

  16. Two-dimensional gold nanostructures with high activity for selective oxidation of carbon–hydrogen bonds

    KAUST Repository

    Wang, Liang

    2015-04-22

    Efficient synthesis of stable two-dimensional (2D) noble metal catalysts is a challenging topic. Here we report the facile synthesis of 2D gold nanosheets via a wet chemistry method, by using layered double hydroxide as the template. Detailed characterization with electron microscopy and X-ray photoelectron spectroscopy demonstrates that the nanosheets are negatively charged and [001] oriented with thicknesses varying from single to a few atomic layers. X-ray absorption spectroscopy reveals unusually low gold–gold coordination numbers. These gold nanosheets exhibit high catalytic activity and stability in the solvent-free selective oxidation of carbon–hydrogen bonds with molecular oxygen.

  17. High growth rate of a-SiC:H films using ethane carbon source by HW-CVD method

    Indian Academy of Sciences (India)

    Mahesh M Kamble; Vaishali S Waman; Sanjay S Ghosh; Azam Mayabadi; Vasant G Sathe; T Shripathi; Habib M Pathan; Sandesh R Jadkar

    2013-12-01

    Hydrogenated amorphous silicon carbide (a-SiC:H) thin films were prepared using pure silane (SiH4) and ethane (C2H6), a novel carbon source, without hydrogen dilution using hot wire chemical vapour deposition (HW-CVD) method at low substrate temperature (200 °C) and at reasonably higher deposition rate (19.5 Å/s < d < 35.2 Å/s). Formation of a-SiC:H films has been confirmed from FTIR, Raman and XPS analysis. Influence of deposition pressure on compositional, structural, optical and electrical properties has been investigated. FTIR spectroscopy analysis revealed that there is decrease in C–H and Si–H bond densities while, Si–C bond density increases with increase in deposition pressure. Total hydrogen content drops from 22.6 to 14.4 at.% when deposition pressure is increased. Raman spectra show increase in structural disorder with increase in deposition pressure. It also confirms the formation of nearly stoichiometric a-SiC:H films. Bandgap calculated using both Tauc’s formulation and absorption at 104 cm-1 shows decreasing trend with increase in deposition pressure. Decrease in refractive index and increase in Urbach energy suggests increase in structural disorder and microvoid density in the films. Finally, it has been concluded that C2H6 can be used as an effective carbon source in HW-CVD method to prepare stoichiometric a-SiC:H films.

  18. Preparation and comparison of a-C:H coatings using reactive sputter techniques

    Energy Technology Data Exchange (ETDEWEB)

    Keunecke, M., E-mail: martin.keunecke@ist.fraunhofer.d [Fraunhofer Institute for Surface Engineering and Thin Films (IST), Braunschweig (Germany); Weigel, K.; Bewilogua, K. [Fraunhofer Institute for Surface Engineering and Thin Films (IST), Braunschweig (Germany); Cremer, R.; Fuss, H.-G. [CemeCon AG, Wuerselen (Germany)

    2009-12-31

    Amorphous hydrogenated carbon (a-C:H) coatings are widely used in several industrial applications. These coatings commonly will be prepared by plasma activated chemical vapor deposition (PACVD). The main method used to prepare a-C:H coating in industrial scale is based on a glow discharge in a hydrocarbon gas like acetylene or methane using a substrate electrode powered with medium frequency (m.f. - some 10 to 300 kHz). Some aims of further development are adhesion improvement, increase of hardness and high coating quality on complex geometries. A relatively new and promising technique to fulfil these requirements is the deposition of a-C:H coatings by a reactive d.c. magnetron sputter deposition from a graphite target with acetylene as reactive gas. An advancement of this technique is the deposition in a pulsed magnetron sputter process. Using these three mentioned techniques a-C:H coatings were prepared in the same deposition machine. For adhesion improvement different interlayer systems were applied. The effect of different substrate bias voltages (d.c. and d.c. pulse) was investigated. By applying the magnetron sputter technique in the d.c. pulse mode, plastic hardness values up to 40 GPa could be reached. Besides hardness other mechanical properties like resistance against abrasive wear were measured and compared. Cross sectional SEM images showed the growth structure of the coatings.

  19. Metal-Oxygen Bond Ionicity as an Efficient Descriptor for Doped NiOOH Photocatalytic Activity.

    Science.gov (United States)

    Zaffran, Jeremie; Toroker, Maytal Caspary

    2016-06-01

    The computational design of solid catalysts has become a very "hot" field during the last decades, especially with the recent increase in computational tool performance. However, theoretical techniques are still very time demanding because they require the consideration of many adsorption configurations of the reaction intermediates on the surface. Herein, we propose to use the metal-oxygen (M-O) bond ionicity as a descriptor for the photocatalytic activity of one of the best catalysts for the oxygen evolution reaction (OER). Ionicity is a bulk property and thus carries the advantage of being easily obtainable from a simple Bader charge analysis by using density functional theory (DFT). We will show that this criterion can be used successfully to design efficient dopants for NiOOH material. This catalyst is known to exhibit interesting photoelectrochemical properties for OER if it is doped with specific transition metals. Finally, we demonstrate that other electronic properties that relate to bulk calculation, such as oxidation states and density of states, are not alone sufficient to explain the photocatalytic activity of the material. Thus, M-O bond ionicity attracts significant interest compared with other bulk observables obtained by using DFT computations. PMID:26945687

  20. CH Bond Activation of Methane by a Transient η(2)-Cyclopropene/Metallabicyclobutane Complex of Niobium.

    Science.gov (United States)

    Li, Chen; Dinoi, Chiara; Coppel, Yannick; Etienne, Michel

    2015-10-01

    This study challenges the problem of the activation of a CH bond of methane by soluble transition metal complexes. High pressure solution NMR, isotopic labeling studies, and kinetic analyses of the degenerate exchange of methane in the methyl complex [Tp(Me2)NbCH3(c-C3H5)(MeCCMe)] (1) are reported. Stoichiometric methane activation by the mesitylene complex [Tp(Me2)Nb(CH2-3,5-C6H3Me2)(c-C3H5) (MeCCMe)] (2) giving 1 is also realized. Evidence is provided that these reactions proceed via an intramolecular abstraction of a β-H of the cyclopropyl group to form either methane or mesitylene from 1 or 2, respectively, yielding the transient unsaturated η(2)-cyclopropene/metallabicyclobutane intermediate [Tp(Me2)Nb(η(2)-c-C3H4) (MeCCMe)] A. This is followed by its mechanistic reverse 1,3-CH bond addition of methane yielding the product. PMID:26374390

  1. Hydrogen Bonding to Alkanes: Computational Evidence

    DEFF Research Database (Denmark)

    Hammerum, Steen; Olesen, Solveig Gaarn

    2009-01-01

    The structural, vibrational, and energetic properties of adducts of alkanes and strong cationic proton donors were studied with composite ab initio calculations. Hydrogen bonding in [D-H+ H-alkyl] adducts contributes to a significant degree to the interactions between the two components, which is...... substantiated by NBO and AIM results. The hydrogen bonds manifest themselves in the same manner as conventional hydrogen bonds, D-H bond elongation, D-H vibrational stretching frequency red shift and intensity increase, and adduct stabilization. The alkane adducts also exhibit elongation of the C-H bonds...... involved and a concurrent red shift, which is rationalized in terms of charge-transfer interactions that cause simultaneous weakening of both the O-H and C-H bonds. Like other dihydrogen-bonded adducts, the adducts possess a bent structure and asymmetric bifurcated hydrogen bonds. The hydrogen bonds are...

  2. Thermodynamic assessement of the Fe-C-H-O system

    Energy Technology Data Exchange (ETDEWEB)

    Conejo, A.N.; Estrada, R.S.; Rodriguez, R.A. [Instituto Tecnologico Morelia (Mexico)

    2003-04-01

    The computation of phase stability diagrams to represent the formation of iron oxides, iron carbides and metallic iron involving the simultaneous effect of pressure (101.3 mbar to 101.3 bar), temperature (477 - 727 C) and reactant gas composition (C-H-O-based gas mixtures), has been carried out. It is proposed to employ ternary diagrams to include all process variables to represent the Fe-C-H-O system. The results can be used in a practical way to define operational conditions to reduce iron oxides into metallic iron as well as to carbidise the solid reactant to produce iron carbide, however, in this case, it has been found that the phase field for iron carbide is located in a region supersaturated with respect to carbon in the gas phase, consequently, if equilibrium prevails, the final solid products will include both iron carbide and free carbon. (orig.)

  3. Amorphous SiC:H- layers from precursors

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, E.; Hilbig, A. [Institute of Ceramic Materials, Freiberg University of Mining and Technology, Gustav-Zeuner Strasse 3, D-09596 Freiberg (Germany); Wenzel, R.; Trommer, K.; Roewer, G. [Institute of Inorganic Chemistry, Freiberg University of Mining and Technology, Leipziger Strasse 29, D-09596 Freiberg (Germany); Sciurova, O.; Niklas, J.R. [Institute of Experimental Physics, Freiberg University of Mining and Technology, Silbermann Strasse 1, D-09596 Freiberg (Germany)

    2002-11-01

    Low-viscous polymers were synthesized in order to produce high purity amorphous SiC layers stabilised by hydrogen, whose optoelectronic properties were then studied in dependence on the pyrolysis conditions. The SiC:H thin layers were deposited by the conversion of an oligomer (chlorovinylsilane) into amorphous silicon carbide. The influence of Si:C ratio and the polymer structure on the composition and ceramic yield of the pyrolysis products is discussed. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  4. Ruthenium-catalyzed C-H/N-O bond functionalization: green isoquinolone syntheses in water.

    OpenAIRE

    Ackermann, Lutz; Fenner, Sabine

    2011-01-01

    Ruthenium-catalyzed isoquinolone syntheses with ample scope were accomplished through carboxylate assistance in environmentally benign water as a reaction medium. The high chemoselectivity of the ruthenium(II) carboxylate complex also set the stage for the direct use of free hydroxamic acids for annulations of alkynes.

  5. C-H arylations of 1,2,3-triazoles by reusable heterogeneous palladium catalysts in biomass-derived γ-valerolactone.

    Science.gov (United States)

    Tian, Xu; Yang, Fanzhi; Rasina, Dace; Bauer, Michaela; Warratz, Svenja; Ferlin, Francesco; Vaccaro, Luigi; Ackermann, Lutz

    2016-07-28

    C-H arylations were accomplished with a user-friendly heterogeneous palladium catalyst in the biomass-derived γ-valerolactone (GVL) as an environmentally-benign reaction medium. The user-friendly protocol was characterized by ample substrate scope and high functional group tolerance in the C-H arylation of 1,2,3-triazoles, and the palladium catalyst could be recycled and reused in the C-H activation process. PMID:27419251

  6. Non-Pincer-Type Mononuclear Scandium Alkylidene Complexes: Synthesis, Bonding, and Reactivity.

    Science.gov (United States)

    Wang, Chen; Zhou, Jiliang; Zhao, Xuefei; Maron, Laurent; Leng, Xuebing; Chen, Yaofeng

    2016-01-22

    The first non-pincer-type mononuclear scandium alkylidene complexes were synthesized and structurally characterized. These complexes exhibited short Sc-C bond lengths and even one of the shortest reported to date (2.1134(18) Å). The multiple character of the Sc-C bond was highlighted by a DFT calculation. This was confirmed by experimental reactivity study where the complex underwent [2+1] cycloaddition with elemental selenium and [2+2] cycloaddition with imine. DFT calculation also revealed a strong nucleophilic behavior of the alkylidene complex that was experimentally demonstrated by the C-H bond activation of phenylacetylene. PMID:26617412

  7. The road to the first, fully active and more stable human insulin variant with an additional disulfide bond.

    Science.gov (United States)

    Vinther, Tine N; Kjeldsen, Thomas B; Jensen, Knud J; Hubálek, František

    2015-11-01

    Insulin, a small peptide hormone, is crucial in maintaining blood glucose homeostasis. The stability and activity of the protein is directed by an intricate system involving disulfide bonds to stabilize the active monomeric species and by their non-covalent oligomerization. All known insulin variants in vertebrates consist of two peptide chains and have six cysteine residues, which form three disulfide bonds, two of them link the two chains and a third is an intra-chain bond in the A-chain. This classical insulin fold appears to have been conserved over half a billion years of evolution. We addressed the question whether a human insulin variant with four disulfide bonds could exist and be fully functional. In this review, we give an overview of the road to engineering four-disulfide bonded insulin analogs. During our journey, we discovered several active four disulfide bonded insulin analogs with markedly improved stability and gained insights into the instability of analogs with seven cysteine residues, importance of dimerization for stability, insulin fibril formation process, and the conformation of insulin binding to its receptor. Our results also open the way for new strategies in the development of insulin biopharmaceuticals. PMID:26382042

  8. Activation of CO and CO2 on homonuclear boron bonds of fullerene-like BN cages: first principles study

    Science.gov (United States)

    Sinthika, S.; Kumar, E. Mathan; Surya, V. J.; Kawazoe, Y.; Park, Noejung; Iyakutti, K.; Thapa, Ranjit

    2015-01-01

    Using density functional theory we investigate the electronic and atomic structure of fullerene-like boron nitride cage structures. The pentagonal ring leads to the formation of homonuclear bonds. The homonuclear bonds are also found in other BN structures having pentagon line defect. The calculated thermodynamics and vibrational spectra indicated that, among various stable configurations of BN-60 cages, the higher number of homonuclear N-N bonds and lower B:N ratio can result in the more stable structure. The homonuclear bonds bestow the system with salient catalytic properties that can be tuned by modifying the B atom bonding environment. We show that homonuclear B-B (B2) bonds can anchor both oxygen and CO molecules making the cage to be potential candidates as catalyst for CO oxidation via Langmuir–Hinshelwood (LH) mechanism. Moreover, the B-B-B (B3) bonds are reactive enough to capture, activate and hydrogenate CO2 molecules to formic acid. The observed trend in reactivity, viz B3 > B2 > B1 is explained in terms of the position of the boron defect state relative to the Fermi level. PMID:26626147

  9. Annealing effects on recombinative activity of nickel at direct silicon bonded interface

    Directory of Open Access Journals (Sweden)

    Takuto Kojima

    2015-09-01

    Full Text Available By performing capacitance transient analyses, the recombination activity at a (110/(100 direct silicon bonded (DSB interface contaminated with nickel diffused at different temperatures, as a model of grain boundaries in multicrystalline silicon, was studied. The trap level depth from the valence band, trap density of states, and hole capture cross section peaked at an annealing temperature of 300 °C. At temperatures ⩾400 °C, the hole capture cross section increased with temperature, but the density of states remained unchanged. Further, synchrotron-based X-ray analyses, microprobe X-ray fluorescence (μ-XRF, and X-ray absorption near edge structure (XANES analyses were performed. The analysis results indicated that the chemical phase after the sample was annealed at 200 °C was a mixture of NiO and NiSi2.

  10. Metal Nanoparticles Catalyzed Selective Carbon-Carbon Bond Activation in the Liquid Phase.

    Science.gov (United States)

    Ye, Rong; Yuan, Bing; Zhao, Jie; Ralston, Walter T; Wu, Chung-Yeh; Unel Barin, Ebru; Toste, F Dean; Somorjai, Gabor A

    2016-07-13

    Understanding the C-C bond activation mechanism is essential for developing the selective production of hydrocarbons in the petroleum industry and for selective polymer decomposition. In this work, ring-opening reactions of cyclopropane derivatives under hydrogen catalyzed by metal nanoparticles (NPs) in the liquid phase were studied. 40-atom rhodium (Rh) NPs, encapsulated by dendrimer molecules and supported in mesoporous silica, catalyzed the ring opening of cyclopropylbenzene at room temperature under hydrogen in benzene, and the turnover frequency (TOF) was higher than other metals or the Rh homogeneous catalyst counterparts. Comparison of reactants with various substitution groups showed that electron donation on the three-membered ring boosted the TOF of ring opening. The linear products formed with 100% selectivity for ring opening of all reactants catalyzed by the Rh NP. Surface Rh(0) acted as the active site in the NP. The capping agent played an important role in the ring-opening reaction kinetics. Larger particle size tended to show higher TOF and smaller reaction activation energy for Rh NPs encapsulated in either dendrimer or poly(vinylpyrrolidone). The generation/size of dendrimer and surface group also affected the reaction rate and activation energy. PMID:27322570

  11. Mechanism of -O-O- bond activation and catalysis by RuIII-pac complexes (pac = polyaminocarboxylate)

    Indian Academy of Sciences (India)

    Debabrata Chatterjee

    2012-11-01

    This paper presents the mechanistic aspects of the -O-O- bond activation by the Ru-pac (pac = polyaminocarboxylate) complex leading to the formation of various catalytic active species, viz. [RuIII(pac)(OOH)]2−, [RuIV(pac)(OH)]− and [RuV(pac)(O)]−, and their reactivity towards oxidation of a few organic compounds.

  12. Direct C-C Coupling of CO2 and the Methyl Group from CH4 Activation through Facile Insertion of CO2 into Zn-CH3 σ-Bond.

    Science.gov (United States)

    Zhao, Yuntao; Cui, Chaonan; Han, Jinyu; Wang, Hua; Zhu, Xinli; Ge, Qingfeng

    2016-08-17

    Conversion of CO2 and CH4 to value-added products will contribute to alleviating the green-house gas effect but is a challenge both scientifically and practically. Stabilization of the methyl group through CH4 activation and facile CO2 insertion ensure the realization of C-C coupling. In the present study, we demonstrate the ready C-C coupling reaction on a Zn-doped ceria catalyst. The detailed mechanism of this direct C-C coupling reaction was examined based on the results from density functional theory calculations. The results show that the Zn dopant stabilizes the methyl group by forming a Zn-C bond, thus hindering subsequent dehydrogenation of CH4. CO2 can be inserted into the Zn-C bond in an activated bent configuration, with the transition state in the form of a three-centered Zn-C-C moiety and an activation barrier of 0.51 eV. The C-C coupling reaction resulted in the acetate species, which could desorb as acetic acid by combining with a surface proton. The formation of acetic acid from CO2 and CH4 is a reaction with 100% atom economy, and the implementation of the reaction on a heterogeneous catalyst is of great importance to the utilization of the greenhouse gases. We tested other possible dopants including Al, Ga, Cd, In, and Ni and found a positive correlation between the activation barrier of C-C coupling and the electronegativity of the dopant, although C-H bond activation is likely the dominant reaction on the Ni-doped ceria catalyst. PMID:27452233

  13. Metal free and selective activation of one C-F bond in a bound CF3 group.

    OpenAIRE

    Azhakar, Ramachandran; Roesky, Herbert W.; Wolf, Hilke; Stalke, Dietmar

    2013-01-01

    The first metal free selective C-F bond activation of a CF(3) group was observed with N-heterocyclic silylenes [PhC(NtBu)(2)SiCl] (1) and [CH{(C=CH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}Si] (2) with PhN=C(CF(3))(2). The reaction proceeds in a 1 : 1 molar ratio to yield the mono C-F bond activated products 3 and 4 with each containing a CF(2) group. Both the reactions proceed through an unprecedented selective activation of one of the C-F bonds rather than forming the [1+2] cycloaddition product co...

  14. β-Boomerang Antimicrobial and Antiendotoxic Peptides: Lipidation and Disulfide Bond Effects on Activity and Structure

    Directory of Open Access Journals (Sweden)

    Harini Mohanram

    2014-04-01

    Full Text Available Drug-resistant Gram-negative bacterial pathogens and endotoxin- or lipopolysaccharide (LPS-mediated inflammations are among some of the most  prominent health issues globally. Antimicrobial peptides (AMPs are eminent molecules that can kill drug-resistant strains and neutralize LPS toxicity. LPS, the outer layer of the outer membrane of Gram-negative bacteria safeguards cell integrity against hydrophobic compounds, including antibiotics and AMPs. Apart from maintaining structural integrity, LPS, when released into the blood stream, also induces inflammatory pathways leading to septic shock. In previous works, we have reported the de novo design of a set of 12-amino acid long cationic/hydrophobic peptides for LPS binding and activity. These peptides adopt β-boomerang like conformations in complex with LPS. Structure-activity studies demonstrated some critical features of the β-boomerang scaffold that may be utilized for the further development of potent analogs. In this work, β-boomerang lipopeptides were designed and structure-activity correlation studies were carried out. These lipopeptides were homo-dimerized through a disulfide bridge to stabilize conformations and for improved activity. The designed peptides exhibited potent antibacterial activity and efficiently neutralized LPS toxicity under in vitro assays. NMR structure of C4YI13C in aqueous solution demonstrated the conserved folding of the lipopeptide with a boomerang aromatic lock stabilized with disulfide bond at the C-terminus and acylation at the N-terminus. These lipo-peptides displaying bacterial sterilization and low hemolytic activity may be useful for future applications as antimicrobial and antiendotoxin molecules.

  15. Significantly shorter Fe-S bond in cytochrome P450-I is consistent with greater reactivity relative to chloroperoxidase

    Science.gov (United States)

    Krest, Courtney M.; Silakov, Alexey; Rittle, Jonathan; Yosca, Timothy H.; Onderko, Elizabeth L.; Calixto, Julio C.; Green, Michael T.

    2015-09-01

    Cytochrome P450 (P450) and chloroperoxidase (CPO) are thiolate-ligated haem proteins that catalyse the activation of carbon hydrogen bonds. The principal intermediate in these reactions is a ferryl radical species called compound I. P450 compound I (P450-I) is significantly more reactive than CPO-I, which only cleaves activated C-H bonds. To provide insight into the differing reactivities of these intermediates, we examined CPO-I and P450-I using variable-temperature Mössbauer and X-ray absorption spectroscopies. These measurements indicate that the Fe-S bond is significantly shorter in P450-I than in CPO-I. This difference in Fe-S bond lengths can be understood in terms of variations in the hydrogen-bonding patterns within the ‘cys-pocket’ (a portion of the proximal helix that encircles the thiolate ligand). Weaker hydrogen bonding in P450-I results in a shorter Fe-S bond, which enables greater electron donation from the axial thiolate ligand. This observation may in part explain P450's greater propensity for C-H bond activation.

  16. Controlled release and enhanced antibacterial activity of salicylic acid by hydrogen bonding with chitosan☆

    Institute of Scientific and Technical Information of China (English)

    Zujin Yang; Yanxiong Fang; Hongbing Ji

    2016-01-01

    Microcapsules of salicylic acid (SA) with chitosan were prepared by spray drying method. Various analytical methods were used to characterize the nature of microcapsules. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of intermolecular interactions between chitosan and SA. Particle size analysis showed that the average size of microcapsules ranged from 2 to 20μm. Scanning electron microscopy (SEM) studies indicated that the microspheres were spherical and had a relatively smooth surface. Microbiological assay of antibacterial activity for SA and its microcapsules was measured using different bacterial strains. It was found that the antibacterial activity of SA was improved after the formation of microcapsules. The in vitro release profile showed that the microcapsules could control SA release from 1 h to 4 h. Kinetic studies revealed that the release pattern follows Korsmeyer–Peppas mechanism. Enhanced antibacterial activity of the SA micro-capsules was attributed to the synergistic effects of intermolecular hydrogen-bonding interactions N–H⋯O and O–H⋯O_C between SA and chitosan. It was also confirmed by quantum chemical calculation.

  17. Investigation of the structure and properties of a-C:H coatings with metal and silicon containing interlayers

    Science.gov (United States)

    Nöthe, M.; Breuer, U.; Koch, F.; Penkalla, H. J.; Rehbach, W. P.; Bolt, H.

    2001-07-01

    The structure of the interface of a-C:H coatings deposited with metal and Si-containing interlayers has been studied. Carbide forming metals (Al, Ti, Cr) can improve the chemical bonding compared with a substrate material which does not form carbides extensively by itself. In addition, a graded transition zone enlarges the interface between the carbon layer and the interlayer metal. In the present work the metal atoms were evaporated and ionized into a dense Ar plasma and deposited onto Si (100) substrates. A graded interface between the metal interlayer and the a-C:H coating was produced by introducing C 2H 2 with increasing amount into the Ar/He plasma during the PAPVD metal deposition process. The PACVD a-C:H deposition process was continued after the termination of metal evaporation to produce the pure a-C:H top layer. Further to Al-, Cr-, Ti- and Cu-interlayers, Si-containing interlayers were investigated. The Si-containing interlayers were deposited by a PACVD process using tetraethoxysilane Si(OC 2H 5) 4 (TEOS) and tetramethylsilane Si(CH 3) 4 (TMS). The characterization of the deposited layer systems was performed by SIMS, SNMS and XPS analyses as well as SEM and analytical TEM methods.

  18. Trigonometric Basis Set Functions: Their Application to the C-H Stretching and Deformation Motions of Benzene and to Orbital Symmetry

    Science.gov (United States)

    Bor, G.; Kettle, Sidney F. A.

    1999-12-01

    The unifying power of the use of trigonometric basis functions in group character tables is demonstrated. Additionally, these functions provide a simple way of generating pictures of symmetry coordinates. This is illustrated for the in-plane stretch and out-of-plane deformation motions of the C-H bonds in benzene. Their application to orbital symmetry applications is also indicated.

  19. Insulin analog with additional disulfide bond has increased stability and preserved activity

    DEFF Research Database (Denmark)

    Vinther, Tine N.; Norrman, Mathias; Ribel, Ulla;

    2013-01-01

    bond may enhance insulin structural stability which would be highly desirable in a pharmaceutical use. To address this hypothesis, we designed insulin with an additional interchain disulfide bond in positions A10/B4 based on Cα-Cα distances, solvent exposure, and side-chain orientation in human insulin...

  20. In vitro characterization of a phosphate starvation-independent carbon-phosphorus bond cleavage activity in Pseudomonas fluorescens 23F.

    OpenAIRE

    McMullan, G.; Quinn, J P

    1994-01-01

    A novel, metal-dependent, carbon-phosphorus bond cleavage activity, provisionally named phosphonoacetate hydrolase, was detected in crude extracts of Pseudomonas fluorescens 23F, an environmental isolate able to utilize phosphonoacetate as the sole carbon and phosphorus source. The activity showed unique specificity toward this substrate; its organic product, acetate, was apparently metabolized by the glyoxylate cycle enzymes of the host cell. Unlike phosphonatase, which was also detected in ...

  1. Activation of the C−N Bond in Nitromethane by Palladium α-Diimine Complexes

    OpenAIRE

    Golisz, Suzanne R.; Hazari, Nilay; Labinger, Jay A.; Bercaw, John E.

    2009-01-01

    The reaction of glyoxal-derived α-diimines with palladium acetates in nitromethane leads to cleavage of the C−N bond in nitromethane, to give palladium nitro complexes in which the α-diimine ligand has been methylated.

  2. The effects of hydrogen bonds on metal-mediated O2 activation and related processes

    OpenAIRE

    Shook, Ryan L.; Borovik, A. S.

    2008-01-01

    Hydrogen bonds stabilize and direct chemistry performed by metalloenzymes. With inspiration from enzymes, we will utilize an approach that incorporates intramolecular hydrogen bond donors to determine their effects on the stability and reactivity of metal complexes. Our premise is that control of secondary coordination sphere interactions will promote new function in synthetic metal complexes. Multidentate ligands have been developed that create rigid organic structures around metal ions. The...

  3. Gold-catalysed facile access to indene scaffolds via sequential C-H functionalization and 5-endo-dig carbocyclization.

    Science.gov (United States)

    Ma, Ben; Wu, Ziang; Huang, Ben; Liu, Lu; Zhang, Junliang

    2016-08-01

    A concise synthesis of functionalized indene derivatives via the gold(i)-catalysed cascade C-H functionalization/conia-ene type reaction of electron-rich aromatics with o-alkynylaryl α-diazoesters has been developed. In this transformation, the gold catalyst not only catalysed the formation of the zwitterionic intermediate via intermolecular C-H functionalization but promoted the subsequent intramolecular 5-endo-dig cyclization via activation of alkynes. The reaction is characterized by high chemo- and site-selectivity, readily available starting materials, nice functional-group tolerance and mild reaction conditions. PMID:27373228

  4. Ruthenium-Catalyzed Direct and Selective C-H Cyanation of N-(Hetero)aryl-7-azaindoles.

    Science.gov (United States)

    Mishra, Aniket; Vats, Tripta Kumari; Deb, Indubhusan

    2016-08-01

    An efficient, highly regioselective, and scalable ruthenium-catalyzed o-aryl C-H mono-cyanation of N-aryl-7-azaindoles to form N-(2-cyanoaryl)-7-azaindoles has been developed through N-directed ortho C-H activation using N-cyano-N-phenyl-p-toluenesulfonamide as cyanating reagent in the presence of AgOTf and NaOAc in DCE. A range of substrates has furnished cyanated azaindoles in good to excellent yields under the simple reaction conditions. Involvement of C-H metalation has been supported by a kinetic study. This methodology provides easy access to a class of pharmaceutically significant molecules and their precursors. PMID:27408980

  5. Rapid Construction of a Benzo-Fused Indoxamycin Core Enabled by Site-Selective C-H Functionalizations.

    Science.gov (United States)

    Bedell, T Aaron; Hone, Graham A B; Valette, Damien; Yu, Jin-Quan; Davies, Huw M L; Sorensen, Erik J

    2016-07-11

    Methods for functionalizing carbon-hydrogen bonds are featured in a new synthesis of the tricyclic core architecture that characterizes the indoxamycin family of secondary metabolites. A unique collaboration between three laboratories has engendered a design for synthesis featuring two sequential C-H functionalization reactions, namely a diastereoselective dirhodium carbene insertion followed by an ester-directed oxidative Heck cyclization, to rapidly assemble the congested tricyclic core of the indoxamycins. This project exemplifies how multi-laboratory collaborations can foster conceptually novel approaches to challenging problems in chemical synthesis. PMID:27206223

  6. The Nature of Activated Non-classical Hydrogen Bonds: A Case Study on Acetylcholinesterase-Ligand Complexes.

    Science.gov (United States)

    Berg, Lotta; Mishra, Brijesh Kumar; Andersson, C David; Ekström, Fredrik; Linusson, Anna

    2016-02-01

    Molecular recognition events in biological systems are driven by non-covalent interactions between interacting species. Here, we have studied hydrogen bonds of the CH⋅⋅⋅Y type involving electron-deficient CH donors using dispersion-corrected density functional theory (DFT) calculations applied to acetylcholinesterase-ligand complexes. The strengths of CH⋅⋅⋅Y interactions activated by a proximal cation were considerably strong; comparable to or greater than those of classical hydrogen bonds. Significant differences in the energetic components compared to classical hydrogen bonds and non-activated CH⋅⋅⋅Y interactions were observed. Comparison between DFT and molecular mechanics calculations showed that common force fields could not reproduce the interaction energy values of the studied hydrogen bonds. The presented results highlight the importance of considering CH⋅⋅⋅Y interactions when analysing protein-ligand complexes, call for a review of current force fields, and opens up possibilities for the development of improved design tools for drug discovery. PMID:26751405

  7. Structure and spectroscopic properties of neutral and cationic tetratomic [C,H,N,Zn] isomers: A theoretical study

    International Nuclear Information System (INIS)

    The structure and spectroscopic parameters of the most relevant [C,H,N,Zn] isomers have been studied employing high-level quantum chemical methods. For each isomer, we provide predictions for their molecular structure, thermodynamic stabilities as well as vibrational and rotational spectroscopic parameters which could eventually help in their experimental detection. In addition, we have carried out a detailed study of the bonding situations by means of a topological analysis of the electron density in the framework of the Bader’s quantum theory of atoms in molecules. The analysis of the relative stabilities and spectroscopic parameters suggests two linear isomers of the neutral [C,H,N,Zn] composition, namely, cyanidehydridezinc HZnCN (1Σ) and hydrideisocyanidezinc HZnNC (1Σ), as possible candidates for experimental detections. For the cationic [C,H,N,Zn]+ composition, the most stable isomers are the ion-molecule complexes arising from the direct interaction of the zinc cation with either the nitrogen or carbon atom of either hydrogen cyanide or hydrogen isocyanide, namely, HCNZn+ (2Σ) and HCNZn+ (2Σ)

  8. Halogen-Bonding-Assisted Iodosylbenzene Activation by a Homogenous Iron Catalyst

    DEFF Research Database (Denmark)

    de Sousa, David P.; Wegeberg, Christina; Vad, Mads Sørensen;

    2016-01-01

    molecules of [Fe(tpena)]2+ cooperate to solubilize PhIO, extracting two equivalents to form the halogen-bonded dimeric {[Fe(tpena)OIPh]2}4+. The closest intradimeric I⋅⋅⋅O distance, 2.56 Å, is nearly 1 Å less than the sum of the van de Waals radii of these atoms. A correlation of the rates of the reaction...... ascribed to [FeIII(tpenaO)]2+, derived from an intramolecular O atom insertion into an Fe–tpena donor bond. Proposed ion pairs, {[Fe(tpena)OIPh]Cl}+ and {[Fe(tpena)OIPh]ClO4}+, are more stable than native [Fe(tpena)OIPh]2+ ions, suggesting that halogen-bonding, as for the solution and solid states...

  9. Unexpected red shift of C-H vibrational band of Methyl benzoate

    CERN Document Server

    Maiti, Kiran Sankar; Scheurer, Christoph

    2016-01-01

    The C-H vibrational bands become more and more important in the structural determination of biological molecules with the development of CARS microscopy and 2DIR spectroscopy. Due to the congested pattern, near degeneracy, and strong anharmonicity of the C-H stretch vibrations, assignment of the C-H vibrational bands are often misleading. Anharmonic vibrational spectra calculation with multidimensional potential energy surface interprets the C-H vibrational spectra more accurately. In this article we have presented the importance of multidimensional potential energy surface in anharmonic vibrational spectra calculation and discuss the unexpected red shift of C-H vibrational band of Methyl benzoate.

  10. High heat flux test of a HIP-bonded first wall panel of reduced activation ferritic steel F-82H

    International Nuclear Information System (INIS)

    Reduced activation ferritic steel F-82H is a primary candidate structural material of DEMO fusion reactors. In fabrication technology, development of the DEMO blanket in JAERI, a hot isostatic pressing (HIP) bonding method, especially for the first wall structure with built-in cooling tubes has been proposed. A HIP-bonded F-82H first wall panel was successfully fabricated with selected manufacturing parameters. A high heat flux test of the HIP-bonded F-82H first wall panel has been performed to examine the thermo-mechanical performance of the panel including the integrity of the HIP-bonded interfaces and the fatigue behavior. A maximum heat flux of 2.7 MW/m2 was applied to accelerate the fatigue test up to 5000 cycles in test blanket inserted ITER. The maximum temperature of the panel was ∼450 deg. C under this heat flux. Through this test campaign, no damage such as cracks was observed on the surface of the panel, and no degradation in heat removal performance was observed either from the temperature responses. The thermal fatigue lifetime of the panel was found to be longer than the fatigue data obtained by mechanical testing

  11. A New Activation Method for Electroless Metal Plating:Palladium Laden via Bonding with Self—Assembly Monolayers

    Institute of Scientific and Technical Information of China (English)

    LiNaXU; JianHuiLIAO; 等

    2002-01-01

    A new activation method has been developed for electroless copper plating on silicon wafer based on palladium chemisorption on SAMs of APTS without SnCl2 sensitization and roughening condition.A closely packed electroless copper film with strong adhesion is successfully formed by AFM observation.XPS study indicates that palladium chemisorption occurred via palladium chloride bonding to the pendant amino group of the SAMs.

  12. A New Activation Method for Electroless Metal Plating: Palladium Laden via Bonding with Self-Assembly Monolayers

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new activation method has been developed for electroless copper plating on silicon wafer based on palladium chemisorption on SAMs of APTS without SnCl2 sensitization and roughening condition. A closely packed electroless copper film with strong adhesion is successfully fonned by AFM observation. XPS study indicates that palladium chemisorption occurred via palladium chloride bonding to the pendant amino group of the SAMs.

  13. To rebound or dissociate? This is the mechanistic question in C-H hydroxylation by heme and nonheme metal-oxo complexes.

    Science.gov (United States)

    Cho, Kyung-Bin; Hirao, Hajime; Shaik, Sason; Nam, Wonwoo

    2016-03-01

    Enzymatic reactions that involve C-H bond activation of alkanes by high-valent iron-oxo species can be explained by the rebound mechanism (RM). Hydroxylation reactions of alkane substrates effected by the reactive compound I (Cpd I) species of cytochrome P450 enzymes are good examples. There was initially little doubt that the rebound paradigm could be carried over in the same form to the arena of synthetic nonheme high-valent iron-oxo or other metal-oxo complexes. However, the active reaction centres of these synthetic systems are not well-caged, in contrast to the active sites of enzymes; therefore, the relative importance of the radical dissociation pathway can become prominent. Indeed, accumulating experimental and theoretical evidence shows that introduction of the non-rebound mechanism (non-RM) is necessary to rationalise the different reactivity patterns observed for synthetic nonheme complexes. In this tutorial review, we discuss several specific examples involving the non-RM while making frequent comparisons to the RM, mainly from the perspective of computational chemistry. We also provide a technical guide to DFT calculations of RM and non-RM and to the interpretations of computational outcomes. PMID:26690848

  14. Silver-Free Palladium-Catalyzed sp(3) and sp(2) C-H Alkynylation Promoted by a 1,2,3-Triazole Amine Directing Group.

    Science.gov (United States)

    Ye, Xiaohan; Xu, Chang; Wojtas, Lukasz; Akhmedov, Novruz G; Chen, Hao; Shi, Xiaodong

    2016-06-17

    Triazole amine was identified as an effective directing group in promoting C-H alkynylation under silver-free conditions. No other external oxidant was required, and the alkynylation products were received in good to excellent yields. X-ray crystallographic analysis confirmed a direct C-H activation intermediate. Other typical directing groups, including pyridine amine (PIP) and 8-aminoquinoline (QA), gave almost no reaction under identical conditions, which highlighted the unique reactivity of the triazole directing group in direct C-H functionalization. PMID:27267908

  15. Study of the hydrogen behavior in amorphous hydrogenated materials of type a - C:H and a - SiC:H facing fusion reactor plasma

    International Nuclear Information System (INIS)

    Plasma facing components of controlled fusion test devices (tokamaks) are submitted to several constraints (irradiation, high temperatures). The erosion (physical sputtering and chemical erosion) and the hydrogen recycling (retention and desorption) of these materials influence many plasma parameters and thus affect drastically the tokamak running. First, we will describe the different plasma-material interactions. It will be pointed out, how erosion and hydrogen recycling are strongly related to both chemical and physical properties of the material. In order to reduce these interactions, we have selected two amorphous hydrogenated materials (a-C:H and a-SiC:H), which are known for their good thermal and chemical qualities. Some samples have been then implanted with lithium ions at different fluences. Our materials have been then irradiated with deuterium ions at low energy. From our results, it is shown that both the lithium implantation and the use of an a - SiC:H substrate can be beneficial in enhancing the hydrogen retention. These results were completed with thermal desorption studies of these materials. It was evidenced that the hydrogen fixation was more efficient in a-SiC:H than in a-C:H substrate. Results in good agreement with those described above have been obtained by exposing a - C:H and a - SiC:H samples to the scrape off layer of the tokamak of Varennes (TdeV, Canada). A modelling of hydrogen diffusion under irradiation has been also proposed. (author)

  16. Hydrogen behaviour study in plasma facing a-C:H and a-SiC:H hydrogenated amorphous materials for fusion reactors

    International Nuclear Information System (INIS)

    Plasma facing components of controlled fusion test devices (tokamaks) are submitted to several constraints (irradiation, high temperatures). The erosion (physical sputtering and chemical erosion) and the hydrogen recycling (retention and desorption) of these materials influence many plasma parameters and thus affect drastically the tokamak running. Firstly, we will describe the different plasma-material interactions. It will be pointed out, how erosion and hydrogen recycling are strongly related to both chemical and physical properties of the material. In order to reduce this interactions, we have selected two amorphous hydrogenated materials (a-C:H and a-SiC:H), which are known for their good thermal and chemical qualities. Some samples have been then implanted with lithium ions at different fluences. Our materials have been then irradiated with deuterium ions at low energy. From our results, it is shown that both the lithium implantation and the use of an a-SiC:H substrate can be benefit in enhancing the hydrogen retention. These results were completed with thermal desorption studies of these materials. It was evidenced that the hydrogen fixation was more efficient in a -SiC:H than in a-C:H substrate. Results in good agreement with those described above have been obtained by exposing a-C:H and a-SiC:H samples to the scrape off layer of the tokamak of Varennes (TdeV, Canada). A modeling of hydrogen diffusion under irradiation has been also proposed. (author)

  17. Preferential activation of primary C–H bonds in the reactions of small alkanes with the diatomic MgO+. cation

    Czech Academy of Sciences Publication Activity Database

    Schröder, Detlef; Roithová, J.; Alikhani, E.; Kwapien, K.; Sauer, J.

    2010-01-01

    Roč. 16, č. 13 (2010), s. 4110-4119. ISSN 0947-6539 R&D Projects: GA AV ČR KJB400550704; GA ČR GA203/08/1487 Grant ostatní: ERC(XE) HORIZOMS AdG226373 Institutional research plan: CEZ:AV0Z40550506 Keywords : alkanes * C-H activation * density functional calculations * magnesium oxide Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.476, year: 2010

  18. Experimental and theoretical studies of Si-Cl and Ge-Cl σ-bond activation reactions by iridium-hydride.

    Science.gov (United States)

    Kameo, H; Ikeda, K; Sakaki, S; Takemoto, S; Nakazawa, H; Matsuzaka, H

    2016-05-01

    We report the iridium hydride-mediated Si-Cl and Ge-Cl σ-bond activation in a low-polarity toluene solution owing to diphosphine-chelation, in which the Si-Cl and Ge-Cl σ-bonds are readily cleaved through an SN2-type pathway via the formation of a free chloride anion. PMID:26928383

  19. Properties of a-C:H:Si thin films deposited by middle-frequency magnetron sputtering

    Science.gov (United States)

    Jiang, Jinlong; Wang, Yubao; Du, Jinfang; Yang, Hua; Hao, Junying

    2016-08-01

    The silicon doped hydrogenated amorphous carbon (a-C:H:Si) films were prepared on silicon substrates by middle-frequency magnetron sputtering silicon target in an argon and methane gas mixture atmosphere. The deposition rate, chemical composition, structure, surface properties, stress, hardness and tribological properties in the ambient air of the films were systemically investigated using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscopy (AFM), nanoindentation and tribological tester. The results show that doped silicon content in the films is controlled in the wide range from 39.7 at.% to 0.2 at.% by various methane gas flow rate, and methane flow rate affects not only the silicon content but also its chemical bonding structure in the films due to the transformation of sputtering modes. Meanwhile, the sp3 carbon component in the films linearly increases with increasing of methane flow rate. The film deposited at moderate methane flow rate of 40-60 sccm exhibits the very smooth surface (RMS roughness 0.4 nm), low stress (0.42 GPa), high hardness (21.1 GPa), as well as low friction coefficient (0.038) and wear rate (1.6 × 10-7 mm3/Nm). The superior tribological performance of the films could be attributed to the formation and integral covering of the transfer materials on the sliding surface and their high hardness.

  20. Impacts of hydrogen dilution on growth and optical properties of a-SiC:H films

    Institute of Scientific and Technical Information of China (English)

    HU; Zhihua; LIAO; Xianbo; DIAO; Hongwei; KONG; Guanglin; Z

    2004-01-01

    Hydrogenated amorphous silicon-carbon (a-SiC:H) films were deposited by plasma enhanced chemical vapor deposition (PECVD) with a fixed methane to silane ratio ([CH4]/[SiH4]) of 1.2 and a wide range of hydrogen dilution (RH=[H2]/[SiH4 + CH4]) values of 12, 22, 33, 102 and 135. The impacts of RH on the structural and optical properties of the films were investigated by using UV-VIS transmission, Fourier transform infrared (FTIR) absorption, Raman scattering and photoluminescence (PL) measur- ements. The effects of high temperature annealing on the films were also probed. It is found that with increasing hydrogen dilution, the optical band gap increases, and the PL peak blueshifts from ~1.43 to 1.62 Ev. In annealed state, the room temperature PL peak for the low RH samples disappears, while the PL peak for the high RH samples appears at ~2.08 Ev, which is attributed to nanocrystalline Si particles confined by Si-C and Si-O bonds.

  1. Ru-catalysed C-H silylation of unprotected gramines, tryptamines and their congeners.

    Science.gov (United States)

    Devaraj, K; Sollert, C; Juds, C; Gates, P J; Pilarski, L T

    2016-04-30

    Selective Ru-catalysed C2-H silylation of heteroarenes is presented. The transformation works with or without directing group assistance and requires no protecting groups. Gramines and tryptamines may be converted efficiently whilst avoiding deleterious elimination side-reactions. Mechanistic studies reveal an unusual activation of the indole C4-H bond by an electron-rich metal. PMID:27050747

  2. SYNTHESIS OF 8-HYDROXYQUINOLINE CHALCONES: TRANS CONFIGURATION, INTRAMOLECULAR HYDROGEN BONDS, BROMINATION, AND ANTIFUNGAL ACTIVITY

    OpenAIRE

    ALONSO J MARRUGO-GONZÁLEZ; VALERIE D ORLOV; ROBERTO FERNANDEZ-MAESTRE

    2012-01-01

    Nine (8-Hydroxyquinolin-5-yl)-arylpropenones were synthesized and their structures demonstrated by IR and NMRspectroscopy. These molecules showed transconfiguration and strong intramolecular hydrogen bonding; in the IR spectra of 5-formyl-8-hydroxyquinoline, 5-acetyl-8-hydroxyquinoline, 1-(8-hydroxyquinolin-5-yl)-3-phenylprop-2-en-1-one and 3-(8-hydroxyquinolin-5-yl)-1-phenylprop-2-en-1-one in CHCl3, besides the known intermolecular hydrogen band (~3180 cm-1), we identified the intramolecular...

  3. Alcohols as alkylating agents in heteroarene C-H functionalization

    Science.gov (United States)

    Jin, Jian; MacMillan, David W. C.

    2015-09-01

    Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage. One of the core principles underlying DNA biosynthesis is the radical-mediated elimination of H2O to deoxygenate ribonucleotides, an example of `spin-centre shift', during which an alcohol C-O bond is cleaved, resulting in a carbon-centred radical intermediate. Although spin-centre shift is a well-understood biochemical process, it is underused by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylation reactions using alcohols as radical precursors. Because conventional radical-based alkylation methods require the use of stoichiometric oxidants, increased temperatures or peroxides, a mild protocol using simple and abundant alkylating agents would have considerable use in the synthesis of diversely functionalized pharmacophores. Here we describe the development of a dual catalytic alkylation of heteroarenes, using alcohols as mild alkylating reagents. This method represents the first, to our knowledge, broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer catalysis. The value of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone.

  4. The Stabilized Cation Pool Method: Metal- and Oxidant-Free Benzylic C-H/Aromatic C-H Cross-Coupling.

    Science.gov (United States)

    Hayashi, Ryutaro; Shimizu, Akihiro; Yoshida, Jun-Ichi

    2016-07-13

    Electrochemical oxidation of toluene derivatives in the presence of a sulfilimine gave benzylaminosulfonium ions as stabilized benzyl cation pools, which reacted with subsequently added aromatic nucleophiles to give the corresponding cross-coupling products. The transformation serves as a powerful metal- and chemical-oxidant-free method for benzylic C-H/aromatic C-H cross-coupling. The method has been successfully applied to synthesis of TP27, an inhibitor of PTPase. PMID:27341676

  5. Evolution of the chemical bonding nature and electrode activity of indium selenide upon the composite formation with graphene nanosheets

    International Nuclear Information System (INIS)

    Graphical abstract: Display Omitted -- Highlights: • In4Se2.85@graphene nanocomposite is easily prepared by high energy mechanical milling process. • The bond covalency of In4Se2.85 is notably changed upon the composite formation with graphene. • In4Se2.85@graphene nanocomposite shows promising anode performance for lithium ion battery. -- Abstract: Evolution of the chemical bonding nature and electrochemical activity of indium selenide upon the composite formation with carbon species is systematically investigated. Nanocomposites of In4Se2.85@graphene and In4Se2.85@carbon-black are synthesized via a solid state reaction between In and Se elements, and the following high energy mechanical milling of In4Se2.85 with graphene and carbon-black, respectively. The high energy mechanical milling (HEMM) of In4Se2.85 with carbon species gives rise to a decrease of particle size with a significant depression of the crystallinity of In4Se2.85 phase. In contrast to the composite formation with carbon-black, that with graphene induces a notable decrease of (In−Se) bond covalency, underscoring significant chemical interaction between graphene and In4Se2.85. Both the nanocomposites of In4Se2.85@graphene and In4Se2.85@carbon-black show much better anode performance for lithium ion batteries with larger discharge capacity and better cyclability than does the pristine In4Se2.85 material, indicating the beneficial effect of composite formation on the electrochemical activity of indium selenide. Between the present nanocomposites, the electrode performance of the In4Se2.85@graphene nanocomposite is superior to that of the In4Se2.85@carbon-black nanocomposite, which is attributable to the weakening of (In−Se) bonds upon the composite formation with graphene as well as to the better mixing between In4Se2.85 and graphene. The present study clearly demonstrates that the composite formation with graphene has strong influence on the chemical bonds and electrode activity of indium

  6. Effect of deposition temperature and thermal annealing on the dry etch rate of a-C: H films for the dry etch hard process of semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Moo [Department of Materials Science and Engineering, Korea University, Anam-Dong, Sungbook-Ku, Seoul, 136-701 (Korea, Republic of); TC Technology Team, Samsung Electronics Co. Ltd., Nongseo-Dong, Kiheung-Ku, Yongin-Si, Gyeounggi-Do, 446-711 (Korea, Republic of); Won, Jaihyung [TC Technology Team, Samsung Electronics Co. Ltd., Nongseo-Dong, Kiheung-Ku, Yongin-Si, Gyeounggi-Do, 446-711 (Korea, Republic of); Yim, Soyoung [Department of Materials Science and Engineering, Korea University, Anam-Dong, Sungbook-Ku, Seoul, 136-701 (Korea, Republic of); Park, Se Jun; Choi, Jongsik; Kim, Jeongtae; Lee, Hyeondeok [TC Technology Team, Samsung Electronics Co. Ltd., Nongseo-Dong, Kiheung-Ku, Yongin-Si, Gyeounggi-Do, 446-711 (Korea, Republic of); Byun, Dongjin, E-mail: dbyun@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Anam-Dong, Sungbook-Ku, Seoul, 136-701 (Korea, Republic of)

    2012-06-01

    The effect of deposition and thermal annealing temperatures on the dry etch rate of a-C:H films was investigated to increase our fundamental understanding of the relationship between thermal annealing and dry etch rate and to obtain a low dry etch rate hard mask. The hydrocarbon contents and hydrogen concentration were decreased with increasing deposition and annealing temperatures. The I(D)/I(G) intensity ratio and extinction coefficient of the a-C:H films were increased with increasing deposition and annealing temperatures because of the increase of sp{sup 2} bonds in the a-C:H films. There was no relationship between the density of the unpaired electrons and the deposition temperature, or between the density of the unpaired electrons and the annealing temperature. However, the thermally annealed a-C:H films had fewer unpaired electrons compared with the as-deposited ones. Transmission electron microscopy analysis showed the absence of any crystallographic change after thermal annealing. The density of the as-deposited films was increased with increasing deposition temperature. The density of the 600 Degree-Sign C annealed a-C:H films deposited under 450 Degree-Sign C was decreased but at 550 Degree-Sign C was increased, and the density of all 800 Degree-Sign C annealed films was increased. The dry etch rate of the as-deposited a-C:H films was negatively correlated with the deposition temperature. The dry etch rate of the 600 Degree-Sign C annealed a-C:H films deposited at 350 Degree-Sign C and 450 Degree-Sign C was faster than that of the as-deposited film and that of the 800 Degree-Sign C annealed a-C:H films deposited at 350 Degree-Sign C and 450 Degree-Sign C was 17% faster than that of the as-deposited film. However, the dry etch rate of the 550 Degree-Sign C deposited a-C:H film was decreased after annealing at 600 Degree-Sign C and 800 Degree-Sign C. The dry etch rate of the as-deposited films was decreased with increasing density but that of the annealed

  7. Gas avalanche pixel detectors with amorphous silicon carbide (a-Si:C:H) overcoating

    International Nuclear Information System (INIS)

    Performance of the gas avalanche pixel detectors of square and circular geometry, with and without semiconducting surface coating, was characterized in terms of gas gain and active region. Although the electric field profile of the square geometry cannot be radially uniform, a 200 microm pitch detector of this type exhibited a maximum gain of ∼ 12,000 which is comparable to that of the circular counterpart. Due to the existence of the anode bus lines passing under the cathodes, there is a defocusing effect of the drift field lines converging to the anodes, resulting in inactive regions where electrons produced from gas ionization are not collected at the anodes. Variation of the count rate with the drift field was measured to probe these defocusing effects. The p-type a-Si:C:H surface coating was effective in reducing these inactive regions

  8. A Periplasmic LolA Derivative with a Lethal Disulfide Bond Activates the Cpx Stress Response System▿

    OpenAIRE

    Tao, Kazuyuki; Watanabe, Shoji; Narita, Shin-ichiro; Tokuda, Hajime

    2010-01-01

    LolA accommodates the acyl chains of lipoproteins in its hydrophobic cavity and shuttles between the inner and outer membranes through the hydrophilic periplasm to place lipoproteins in the outer membrane. The LolA(I93C/F140C) derivative, in which Cys replaces Ile at position 93 and Phe at position 140, strongly inhibited growth in the absence of a reducing agent because of the lethal intramolecular disulfide bond between the two Cys residues. Expression of I93C/F140C was found to activate th...

  9. Formation of sulfido niobium complexes through C-S bond activation

    International Nuclear Information System (INIS)

    Upon reacting η5-C5H5)2 Nb CL2, η5-C5H5 = Cp, and (Ph)3 Sn (S Ph), in THF, (η5- C5H5)2 Nb (Cl) (μ-S) Sn (Ph)3 (Cl), 1, and (η5-C5 H5)2 Nb (S) Cl, 2, were obtained. Complexes 1 and 2 were characterized by IR, 1H-NMR, 13 C-NMR, Moessbauer spectroscopies, elemental analysis as well as by atomic absorption. Hydrolysis of 1 yielded the μ-oxo species, (η5-C5 H5)2 Nb (Cl) (μ-O) Sn (Ph)3 Cl, 3, which was characterized by IR, 1H-NMR, 13 C-NMR and Moessbauer spectroscopies, elemental analysis, atomic absorption as well as by X-ray crystallography. It crystallizes in the space group Pca21 with a= 17.282(3), b = 18.122(4), c 17.3269(2), V = 5426.2(16) angstrom3, and Z= 8. Additional studies indicated that the complexes were formed as a result of the nucleophilic displacement of the niobium-chloride bond by the thiolate ligand followed by a C-S bond cleavage. The cleavage occurs with an excess of the thiolate compound equal to or greater than 2:1. (author)

  10. Tandem Rh(III)-Catalyzed C-H Amination/Annulation Reactions: Synthesis of Indoloquinoline Derivatives in Water.

    Science.gov (United States)

    Shi, Liangliang; Wang, Baiquan

    2016-06-17

    An efficient Rh(III)-catalyzed synthetic method for indoloquinoline derivatives from readily available indoles and isoxazoles was developed. This annulation procedure undergoes tandem C-H activation, cyclization, and condensation steps. In this domino cyclization reaction, water is an efficient solvent. A catalytically competent five-membered rhodacycle has been isolated and characterized, thus revealing a key intermediate in the catalytic cycle. PMID:27266834

  11. Self-lubrication and wear behavior of TiC/a-C : H nanocomposite coatings

    NARCIS (Netherlands)

    Pei, Y. T.; Huizenga, P.; Galvan, D.; De Hosson, J. Th. M.; Chandra, T; Tsuzaki, K; Militzer, M; Ravindran, C

    2007-01-01

    Advanced TiC/a-C:H nanocomposite coatings have been produced via reactive deposition in a closed-field unbalanced magnetron sputtering system. In this paper, we report on the tribological behavior of TiC/a-C:H nanocomposite coatings in which ultra-low friction is tailored with superior wear resistan

  12. Thin films of hydrogenated amorphous carbon (a-C:H) obtained through chemical vapor deposition assisted by plasma; Peliculas delgadas de carbono amorfo hidrogenado (a-C:H) obtenidas mediante deposito quimico de vapores asistido por plasma

    Energy Technology Data Exchange (ETDEWEB)

    Mejia H, J.A.; Camps C, E.E.; Escobar A, L.; Romero H, S.; Chirino O, S. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Muhl S, S. [IIM-UNAM, 04510 Mexico D.F. (Mexico)

    2004-07-01

    Films of hydrogenated amorphous carbon (a-C:H) were deposited using one source of microwave plasma with magnetic field (type ECR), using mixtures of H{sub 2}/CH{sub 4} in relationship of 80/20 and 95/05 as precursory gases, with work pressures of 4X10{sup -4} to 6x10{sup -4} Torr and an incident power of the discharge of microwaves with a constant value of 400 W. It was analyzed the influence among the properties of the films, as the deposit rate, the composition and the bonding types, and the deposit conditions, such as the flow rates of the precursory gases and the polarization voltage of the sample holders. (Author)

  13. Aging of oxygen and hydrogen plasma discharge treated a-C:H and ta-C coatings

    Science.gov (United States)

    Bachmann, Svenja; Schulze, Marcus; Morasch, Jan; Hesse, Sabine; Hussein, Laith; Krell, Lisa; Schnagl, Johann; Stark, Robert W.; Narayan, Suman

    2016-05-01

    Surface modification with gas plasma is an efficient and easy way to improve the surface energy and the tribological behavior of diamond-like carbon (DLC) coatings, e.g., in biomedical implants or as protective coatings. However, the long-term performance of the plasma treated DLC coatings is not fully clear. We thus studied the long-term stability of two kinds of DLC coatings, namely (a) hydrogenated amorphous carbon (a-C:H) and (b) tetrahedral amorphous carbon (ta-C) treated at different radio frequency (RF) power and time of oxygen (O2) and hydrogen (H2) plasma. Their surface properties, e.g. surface wettability, structure and tribological behavior, were studied at regular intervals for a period of two months using contact angle goniometer, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), lateral force microscopy (LFM) and ball on disc apparatus. The surface energy of both the coatings decreased upon aging. The higher the RF power and time of treatment, the higher was the hydrophobicity upon aging. XPS analysis showed that the increase in hydrophobicity could be due to adsorption of unavoidable volatile organic components in the atmosphere. The H2 plasma treated ta-C was capable of rearranging its structural bonds upon aging. The nano-friction measurements by LFM showed that the coefficient of friction of plasma treated a-C:H and ta-C decreased upon aging. The results indicate that the surface properties of plasma treated a-C:H and ta-C are not stable on long-term and are influenced by the environmental conditions.

  14. Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

    Directory of Open Access Journals (Sweden)

    Burkhard Koenig

    2011-01-01

    Full Text Available N-Arylated aliphatic and aromatic amines are important substituents in many biologically active compounds. In the last few years, transition-metal-mediated N-aryl bond formation has become a standard procedure for the introduction of amines into aromatic systems. While N-arylation of simple aromatic halides by simple amines works with many of the described methods in high yield, the reactions may require detailed optimization if applied to the synthesis of complex molecules with additional functional groups, such as natural products or drugs. We discuss and compare in this review the three main N-arylation methods in their application to the synthesis of biologically active compounds: Palladium-catalysed Buchwald–Hartwig-type reactions, copper-mediated Ullmann-type and Chan–Lam-type N-arylation reactions. The discussed examples show that palladium-catalysed reactions are favoured for large-scale applications and tolerate sterically demanding substituents on the coupling partners better than Chan–Lam reactions. Chan–Lam N-arylations are particularly mild and do not require additional ligands, which facilitates the work-up. However, reaction times can be very long. Ullmann- and Buchwald–Hartwig-type methods have been used in intramolecular reactions, giving access to complex ring structures. All three N-arylation methods have specific advantages and disadvantages that should be considered when selecting the reaction conditions for a desired C–N bond formation in the course of a total synthesis or drug synthesis.

  15. The Comparative Studies of Binding Activity of Curcumin and Didemethylated Curcumin with Selenite: Hydrogen Bonding vs Acid-Base Interactions

    Science.gov (United States)

    Liao, Jiahn-Haur; Wu, Tzu-Hua; Chen, Ming-Yi; Chen, Wei-Ting; Lu, Shou-Yun; Wang, Yi-Hsuan; Wang, Shao-Pin; Hsu, Yen-Min; Huang, Yi-Shiang; Huang, Zih-You; Lin, Yu-Ching; Chang, Ching-Ming; Huang, Fu-Yung; Wu, Shih-Hsiung

    2015-12-01

    In this report, the in vitro relative capabilities of curcumin (CCM) and didemethylated curcumin (DCCM) in preventing the selenite-induced crystallin aggregation were investigated by turbidity tests and isothermal titration calorimetry (ITC). DCCM showed better activity than CCM. The conformers of CCM/SeO32- and DCCM/SeO32- complexes were optimized by molecular orbital calculations. Results reveal that the selenite anion surrounded by CCM through the H-bonding between CCM and selenite, which is also observed via IR and NMR studied. For DCCM, the primary driving force is the formation of an acid-base adduct with selenite showing that the phenolic OH group of DCCM was responsible for forming major conformer of DCCM. The formation mechanisms of selenite complexes with CCM or DCCM explain why DCCM has greater activity than CCM in extenuating the toxicity of selenite as to prevent selenite-induced lens protein aggregation.

  16. The Comparative Studies of Binding Activity of Curcumin and Didemethylated Curcumin with Selenite: Hydrogen Bonding vs Acid-Base Interactions

    Science.gov (United States)

    Liao, Jiahn-Haur; Wu, Tzu-Hua; Chen, Ming-Yi; Chen, Wei-Ting; Lu, Shou-Yun; Wang, Yi-Hsuan; Wang, Shao-Pin; Hsu, Yen-Min; Huang, Yi-Shiang; Huang, Zih-You; Lin, Yu-Ching; Chang, Ching-Ming; Huang, Fu-Yung; Wu, Shih-Hsiung

    2015-01-01

    In this report, the in vitro relative capabilities of curcumin (CCM) and didemethylated curcumin (DCCM) in preventing the selenite-induced crystallin aggregation were investigated by turbidity tests and isothermal titration calorimetry (ITC). DCCM showed better activity than CCM. The conformers of CCM/SeO32− and DCCM/SeO32− complexes were optimized by molecular orbital calculations. Results reveal that the selenite anion surrounded by CCM through the H-bonding between CCM and selenite, which is also observed via IR and NMR studied. For DCCM, the primary driving force is the formation of an acid-base adduct with selenite showing that the phenolic OH group of DCCM was responsible for forming major conformer of DCCM. The formation mechanisms of selenite complexes with CCM or DCCM explain why DCCM has greater activity than CCM in extenuating the toxicity of selenite as to prevent selenite-induced lens protein aggregation. PMID:26635113

  17. Thin films of hydrogenated amorphous carbon (a-C:H) obtained through chemical vapor deposition assisted by plasma

    International Nuclear Information System (INIS)

    Films of hydrogenated amorphous carbon (a-C:H) were deposited using one source of microwave plasma with magnetic field (type ECR), using mixtures of H2/CH4 in relationship of 80/20 and 95/05 as precursory gases, with work pressures of 4X10-4 to 6x10-4 Torr and an incident power of the discharge of microwaves with a constant value of 400 W. It was analyzed the influence among the properties of the films, as the deposit rate, the composition and the bonding types, and the deposit conditions, such as the flow rates of the precursory gases and the polarization voltage of the sample holders. (Author)

  18. Iridium-bipyridine periodic mesoporous organosilica catalyzed direct C-H borylation using a pinacolborane.

    Science.gov (United States)

    Maegawa, Yoshifumi; Inagaki, Shinji

    2015-08-01

    Heterogeneous catalysis for direct C-H borylation of arenes and heteroarenes in the combination of iridium (Ir) complex fixed on periodic mesoporous organosilica containing bipyridine ligands within the framework (Ir-BPy-PMO) and pinacolborane (HBpin) is reported. Ir-BPy-PMO showed higher catalytic activity toward the borylation of benzene with inexpensive HBpin compared to expensive bis(pinacolato)diboron (B2pin2). The precatalyst could be handled without the use of a glove box. The catalyst was easily recovered from reaction mixtures by simple filtration under air. The recovered catalyst still showed good catalytic activity for at least three more times for the borylation of benzene. A variety of arenes and heteroarenes were successfully borylated with high boron efficiency by Ir-BPy-PMO using HBpin, whereas almost no activity was observed for borylation of some heteroarenes with B2pin2. The system using Ir-BPy-PMO and HBpin was also utilized in syntheses of multi-boronated thiophene-based building blocks containing ladder-, acenefused-, and fused-thiophene skeletons. The combination of a stable and reusable solid catalyst and inexpensive HBpin is expected to be superior to conventional approaches for the development of industrial applications. PMID:25748945

  19. Cooperativity between Al Sites Promotes Hydrogen Transfer and Carbon-Carbon Bond Formation upon Dimethyl Ether Activation on Alumina.

    Science.gov (United States)

    Comas-Vives, Aleix; Valla, Maxence; Copéret, Christophe; Sautet, Philippe

    2015-09-23

    The methanol-to-olefin (MTO) process allows the conversion of methanol/dimethyl ether into olefins on acidic zeolites via the so-called hydrocarbon pool mechanism. However, the site and mechanism of formation of the first carbon-carbon bond are still a matter of debate. Here, we show that the Lewis acidic Al sites on the 110 facet of γ-Al2O3 can readily activate dimethyl ether to yield CH4, alkenes, and surface formate species according to spectroscopic studies combined with a computational approach. The carbon-carbon forming step as well as the formation of methane and surface formate involves a transient oxonium ion intermediate, generated by a hydrogen transfer between surface methoxy species and coordinated methanol on adjacent Al sites. These results indicate that extra framework Al centers in acidic zeolites, which are associated with alumina, can play a key role in the formation of the first carbon-carbon bond, the initiation step of the industrial MTO process. PMID:27162986

  20. Study of the hydrogen behavior in amorphous hydrogenated materials of type a - C:H and a - SiC:H facing fusion reactor plasma; Etude du comportament de l`hydrogene dans des materiaux amorphes hydrogenes de type a - C:H et a - SiC:H devant faire face au plasma des reacteurs a fusion

    Energy Technology Data Exchange (ETDEWEB)

    Barbier, G. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire

    1997-04-10

    Plasma facing components of controlled fusion test devices (tokamaks) are submitted to several constraints (irradiation, high temperatures). The erosion (physical sputtering and chemical erosion) and the hydrogen recycling (retention and desorption) of these materials influence many plasma parameters and thus affect drastically the tokamak running. First, we will describe the different plasma-material interactions. It will be pointed out, how erosion and hydrogen recycling are strongly related to both chemical and physical properties of the material. In order to reduce these interactions, we have selected two amorphous hydrogenated materials (a-C:H and a-SiC:H), which are known for their good thermal and chemical qualities. Some samples have been then implanted with lithium ions at different fluences. Our materials have been then irradiated with deuterium ions at low energy. From our results, it is shown that both the lithium implantation and the use of an a - SiC:H substrate can be beneficial in enhancing the hydrogen retention. These results were completed with thermal desorption studies of these materials. It was evidenced that the hydrogen fixation was more efficient in a-SiC:H than in a-C:H substrate. Results in good agreement with those described above have been obtained by exposing a - C:H and a - SiC:H samples to the scrape off layer of the tokamak of Varennes (TdeV, Canada). A modelling of hydrogen diffusion under irradiation has been also proposed. (author) 176 refs.

  1. Identification of nanoscale structure and morphology reconstruction in oxidized a-SiC:H thin films

    Energy Technology Data Exchange (ETDEWEB)

    Vasin, A.V.; Rusavsky, A.V.; Nazarov, A.N.; Lysenko, V.S.; Lytvyn, P.M.; Strelchuk, V.V. [Lashkaryov Institute of Semiconductor Physics, 41 Nauki Pr., Kiev 03028 (Ukraine); Kholostov, K.I.; Bondarenko, V.P. [Belarusian State University of Informatics and Radioelectronics, 6P. Brovki Str., Minsk 220013 (Belarus); Starik, S.P. [Bakul Institute of Superhard Materials, 2 Avtzavodskaya Str., Kiev 04074 (Ukraine)

    2012-11-01

    Highlights: Black-Right-Pointing-Pointer Increase of magnetron discharge power results in densification of a-SiC:H thin films. Black-Right-Pointing-Pointer The denser a-SiC:H material the better resistance to oxidation by oxygen. Black-Right-Pointing-Pointer Oxidation of soft a-SiC:H films can result in increase of electric conductivity. Black-Right-Pointing-Pointer Formation of graphitic clusters was found in a-SiC:H after annealing in oxygen. - Abstract: Oxidation behavior of a-SiC:H layers deposited by radio-frequency magnetron sputtering technique was examined by Kelvin probe force microscopy (KPFM) in combination with scanning electron microscopy, Fourier-transform infra-red spectroscopy and submicron selected area Raman scattering spectroscopy. Partially oxidized a-SiC:H samples (oxidation at 600 Degree-Sign C in oxygen) were examined to clarify mechanism of the oxidation process. Nanoscale and microscale morphological defects (pits) with dimension of about 50 nm and several microns respectively have appeared after thermal treatment. KPFM measurements exhibited the surface potential of the material in micro pits is significantly smaller in comparison with surrounding material. Submicron RS measurements indicates formation of graphite-like nano-inclusions in the pit defects. We conclude that initial stage of oxidation process in a-SiC:H films takes place not homogeneously throughout the layer but it is initiated in local nanoscale regions followed by spreading over all layer.

  2. Red-Shifting versus Blue-Shifting Hydrogen Bonds: Perspective from Ab Initio Valence Bond Theory.

    Science.gov (United States)

    Chang, Xin; Zhang, Yang; Weng, Xinzhen; Su, Peifeng; Wu, Wei; Mo, Yirong

    2016-05-01

    Both proper, red-shifting and improper, blue-shifting hydrogen bonds have been well-recognized with enormous experimental and computational studies. The current consensus is that there is no difference in nature between these two kinds of hydrogen bonds, where the electrostatic interaction dominates. Since most if not all the computational studies are based on molecular orbital theory, it would be interesting to gain insight into the hydrogen bonds with modern valence bond (VB) theory. In this work, we performed ab initio VBSCF computations on a series of hydrogen-bonding systems, where the sole hydrogen bond donor CF3H interacts with ten hydrogen bond acceptors Y (═NH2CH3, NH3, NH2Cl, OH(-), H2O, CH3OH, (CH3)2O, F(-), HF, or CH3F). This series includes four red-shifting and six blue-shifting hydrogen bonds. Consistent with existing findings in literature, VB-based energy decomposition analyses show that electrostatic interaction plays the dominating role and polarization plays the secondary role in all these hydrogen-bonding systems, and the charge transfer interaction, which denotes the hyperconjugation effect, contributes only slightly to the total interaction energy. As VB theory describes any real chemical bond in terms of pure covalent and ionic structures, our fragment interaction analysis reveals that with the approaching of a hydrogen bond acceptor Y, the covalent state of the F3C-H bond tends to blue-shift, due to the strong repulsion between the hydrogen atom and Y. In contrast, the ionic state F3C(-) H(+) leads to the red-shifting of the C-H vibrational frequency, owing to the attraction between the proton and Y. Thus, the relative weights of the covalent and ionic structures essentially determine the direction of frequency change. Indeed, we find the correlation between the structural weights and vibrational frequency changes. PMID:27074500

  3. Opto-electronic properties of P-doped nc-Si-QD/a-SiC:H thin films as foundation layer for all-Si solar cells in superstrate configuration

    Science.gov (United States)

    Kar, Debjit; Das, Debajyoti

    2016-07-01

    With the advent of nc-Si solar cells having improved stability, the efficient growth of nc-Si i-layer of the top cell of an efficient all-Si solar cell in the superstrate configuration prefers nc-Si n-layer as its substrate. Accordingly, a wide band gap and high conducting nc-Si alloy material is a basic requirement at the n-layer. Present investigation deals with the development of phosphorous doped n-type nanocrystalline silicon quantum dots embedded in hydrogenated amorphous silicon carbide (nc-Si-QD/a-SiC:H) hetero-structure films, wherein the optical band gap can be widened by the presence of Si-C bonds in the amorphous matrix and the embedded high density tiny nc-Si-QDs could provide high electrical conductivity, particularly in P-doped condition. The nc-Si-QDs simultaneously facilitate further widening of the optical band gap by virtue of the associated quantum confinement effect. A complete investigation has been made on the electrical transport phenomena involving charge transfer by tunneling and thermionic emission prevailing in n-type nc-Si-QD/a-SiC:H thin films. Their correlation with different phases of the specific heterostructure has been carried out for detailed understanding of the material, in order to improve its device applicability. The n-type nc-Si-QD/a-SiC:H films exhibit a thermally activated electrical transport above room temperature and multi-phonon hopping (MPH) below room temperature, involving defects in the amorphous phase and the grain-boundary region. The n-type nc-Si-QD/a-SiC:H films grown at ˜300 °C, demonstrating wide optical gap ˜1.86-1.96 eV and corresponding high electrical conductivity ˜4.5 × 10-1-1.4 × 10-2 S cm-1, deserve to be an effective foundation layer for the top nc-Si sub-cell of all-Si solar cells in n-i-p structure with superstrate configuration.

  4. J.C.H. de Meijere (1866-1947), een voorzichtig geneticus en evolutiebioloog

    OpenAIRE

    Schoor, W.J. van der

    1991-01-01

    J.C.H. de Meijere (1866-1947), a cautious geneticist and evolutionary biologist

    After the success of Hugo de Vries' 'mutationism' during the socalled 'Eclipse of Darwinism' (see Bowler, 1983), Dutch biologists in the 20's and 30's had little interest in evolutionary theory. A remarkable exception was the entomologist J.C.H. de Meijere, who thought technical zoology and (1921-1936) genetics at Amsterdam...

  5. Copper-Catalyzed Oxidative C-H Amination of Tetrahydrofuran with Indole/Carbazole Derivatives.

    Science.gov (United States)

    Yang, Qingjing; Choy, Pui Ying; Fu, Wai Chung; Fan, Baomin; Kwong, Fuk Yee

    2015-11-01

    A simple α-C-H amination of cyclic ether with indole/carbazole derivatives has been accomplished by employing copper(II) chloride/bipy as the catalyst system. In the presence of the di-tert-butyl peroxide oxidant, cyclic ethers such as tetrahydrofuran, 1,4-dioxane, and tetrahydropyran successfully undergo C-H/N-H cross dehydrogenative coupling (CDC) with various carbazole or indole derivatives in good-to-excellent yields. PMID:26485515

  6. Short Synthesis of Sulfur Analogues of Polyaromatic Hydrocarbons through Three Palladium-Catalyzed C-H Bond Arylations.

    Science.gov (United States)

    Hagui, Wided; Besbes, Néji; Srasra, Ezzeddine; Roisnel, Thierry; Soulé, Jean-François; Doucet, Henri

    2016-09-01

    An expeditious synthesis of a wide range of phenanthro[9,10-b]thiophene derivatives, which are a class of polyaromatic hydrocarbon (PAH) containing a sulfur atom, is reported. The synthetic scheme involves only two operations from commercially available thiophenes, 2-bromobenzenesulfonyl chlorides and aryl bromides. In the first step, palladium-catalyzed desulfitative arylation using 2-bromobenzenesulfonyl chlorides allows the synthesis of thiophene derivatives, which are substituted at the C4 position by an aryl group containing an ortho-bromo substituent. Then, a palladium-catalyzed one-pot cascade intermolecular C5-arylation of thiophene using aryl bromides followed by intramolecular arylation led to the corresponding phenanthro[9,10-b]thiophenes in a single operation. In addition, PAHs containing two or three sulfur atoms, as well as both sulfur and nitrogen atoms, were also designed by this strategy. PMID:27550151

  7. Structure and Friction Behavior of CrNx/a-C:H Nanocomposite Films

    Directory of Open Access Journals (Sweden)

    Lunlin Shang

    2014-01-01

    Full Text Available CrN and CrNx/a-C:H nanocomposite films were deposited on Si substrates by the magnetron sputtering technique. The structure, chemical state, and friction behavior of the CrNx/a-C:H films prepared at various CH4 content were studied systematically. The CrN film shows strong (111 and (220 orientation, while the CrNx/a-C:H films consist of the nanocrystalline CrNx or Cr particles embedded in an amorphous hydrocarbon (a-C:H matrix and show weak diffraction peaks, which is in accordance with the XPS analysis results. The typical Raman D and G peaks are observed, indicating that the separated amorphous carbon or CNx phase appears in the CrNx/a-C:H films. However, no chromium carbide was observed in all the as-deposited samples. From the SEM graphs, all the deposited films depicted a dense and compact microstructure with well-attached interface with the substrate. The average friction coefficient of the CrNx/a-C:H films largely decreased with increasing CH4 content.

  8. Carbon–Hydrogen Bond Activation, C–N Bond Coupling, and Cycloaddition Reactivity of a Three-Coordinate Nickel Complex Featuring a Terminal Imido Ligand

    OpenAIRE

    Mindiola, Daniel J.; Waterman, Rory; Iluc, Vlad M.; Cundari, Thomas R.; Hillhouse, Gregory L.

    2014-01-01

    The three-coordinate imidos (dtbpe)Ni=NR (dtbpe = t Bu2PCH2CH2P t Bu2, R = 2,6- i Pr2C6H3, 2,4,6-Me3C6H2 (Mes), and 1-adamantyl (Ad)), which contain a legitimate Ni–N double bond as well as basic imido nitrogen based on theoretical analysis, readily deprotonate HC≡CPh to form the amide acetylide species (dtbpe)Ni{NH(Ar)}(C≡CPh). In the case of R = 2,6- i Pr2C6H3, reductive carbonylation results in formation of the (dtbpe)Ni(CO)2 along with the N–C coupled product keteneimine PhCH=C=N(2,6- i P...

  9. Anaerobic DNA cleavage in red light by dicopper(II) complexes on disulphide bond activation

    Indian Academy of Sciences (India)

    Debojyoti Lahiri; Ritankar Majumdar; Ashis K Patra; Akhil R Chakravarty

    2010-05-01

    Binuclear complexes [Cu(-RSSR)]2 (1) and [M2(-PDS)(H2O)]2 (M = Cu(II), 2; Fe(II), 3), where H2RSSR is a reduced Schiff base derived from 2-(thioethyl)salicylaldimine having a disulphide moiety and H2PDS is derived from dimerization of D-penicillamine, have been prepared, structurally characterized, and their photo-induced DNA cleavage activity studied. The crystal structure of 1 shows the complex as a discrete binuclear species with each metal in a CuN2O2 square-planar geometry (Cu…Cu, 6.420 Å). The tetradentate RSSR2- acts as a bridging ligand. The sulphur atoms in the disulphide unit do not interact with the metal ions. Complexes 1-3 do not show any DNA cleavage activity in darkness. The copper(II) complexes exhibit chemical nuclease activity in the presence of 3-mercaptopropionic acid. Cleavage of supercoiled DNA has been observed in UV-A light of 365 nm for 1 and red light of 647.1 nm for both 1 and 2 in air. Mechanistic data reveal the involvement of the disulphide unit as photosensitizer generating hydroxyl radicals ($^{\\bullet}$OH) as the reactive species. Photo-induced DNA cleavage in red light seems to involve sulphide radicals in a type-I process and hydroxyl radicals. The dicopper(II) complexes show significant anaerobic photo-induced DNA cleavage activity in red light under argon following type-I pathway without involving any reactive oxygen species.

  10. Catalysis of hydrolysis and nucleophilic substitution at the P-N bond of phosphoimidazolide-activated nucleotides in phosphate buffers

    Science.gov (United States)

    Kanavarioti, A.; Rosenbach, M. T.

    1991-01-01

    Phosphoimidazolide-activated derivatives of guanosine and cytidine 5'-monophosphates, henceforth called ImpN's, exhibit enhanced rates of degradation in the presence of aqueous inorganic phosphate in the range 4.0 < or = pH < or = 8.6. This degradation is been attributed to (i) nucleophilic substitution of the imidazolide and (ii) catalysis of the P-N bond hydrolysis by phosphate. The first reaction results in the formation of nucleoside 5'-diphosphate and the second in nucleoside 5'-monophosphate. Analysis of the observed rates as well as the product ratios as a function of pH and phosphate concentration allow distinction between various mechanistic possibilities. The results show that both H2PO4- and HPO4(2-) participate in both hydrolysis and nucleophilic substitution. Statistically corrected biomolecular rate constants indicate that the dianion is 4 times more effective as a general base than the monoanion, and 8 times more effective as nucleophile. The low Bronsted value beta = 0.15 calculated for these phosphate species, presumed to act as general bases in facilitating water attack, is consistent with the fact that catalysis of the hydrolysis of the P-N bond in ImpN's has not been detected before. The beta nuc = 0.35 calculated for water, H2PO4-, HPO4(2-), and hydroxide acting as nucleophiles indicates a more associative transition state for nucleotidyl (O2POR- with R = nucleoside) transfers than that observed for phosphoryl (PO3(2-)) transfers (beta nuc = 0.25). With respect to the stability/reactivity of ImpN's under prebiotic conditions, our study shows that these materials would not suffer additional degradation due to inorganic phosphate, assuming the concentrations of phosphate, Pi, on prebiotic Earth were similar to those in the present oceans ([Pi] approximately 2.25 micromoles).

  11. R and D activities for the design of the MITICA Plasma Driver Plate manufacturing process via explosion bonding technique

    International Nuclear Information System (INIS)

    Highlights: ► The work is focused on the manufacturing process of the Plasma Driver Plate of MITICA. ► A clad plate of molybdenum and copper has been manufactured. ► Simulations have been carried out to improve the design geometry of the component. ► The driver-hole rim have been machined and hot formed. ► No delamination were found in the molybdenum. -- Abstract: The back plate of the MITICA plasma source, named Plasma Driver Plate (PDP), will be protected from the impact of the highly energetic back-streaming positive ions (BSI+), generated inside the accelerator, by a 1.0 mm thick molybdenum layer that will be joined by Explosion Bonding (EB) technique to the copper heat sink. This technology has been investigated and used for manufacturing prototypes, demonstrating very high strength of the obtained molybdenum–copper interface. The production of the shaped edge profile of the driver-hole, after the EB, is an open point. In order to demonstrate the possibility to produce the PDP by explosion bonding, the manufacturing of a full scale prototype of the area just around one of the PDP driver-holes was identified as the road to address most of the manufacturing issues. Elasto-plastic finite element analyses have been carried out to improve the hole rim geometry and the process parameters of all the manufacturing steps. A full scale prototype of the PDP driver-hole has been manufactured and tested. This contribution gives an overview of the R and D activities carried out to address the main open issues, to define the PDP component detailed geometry and its manufacturing processes, via EB technique

  12. Thermal Modification of a-SiC:H Films Deposited by Plasma Enhanced Chemical Vapour Deposition from CH4+SiH4 Mixtures

    Institute of Scientific and Technical Information of China (English)

    刘玉学; 王宁会; 刘益春; 申德振; 范希武; 李灵燮

    2001-01-01

    The effects of thermal annealing on photoluminescence (PL) and structural properties of a-Si1-xCx :H films deposited by plasma enhanced chemical vapour deposition from CH4+SiH4 mixtures are studied by using infrared, PL and transmittance-reflectance spectra. In a-SiC:H network, high-temperature annealing gives rise to the effusion of hydrogen from strongly bonded hydrogen in SiH, SiH2, (SiH2)n, SiCHn and CHn configurations and the break of weak C-C, Si-Si and C-Si bonds. A structural rearrangement will occur, which causes a significant correlation of the position and intensity of the PL signal with the annealing temperature. The redshift of the PL peak is related to the destruction of the confining power of barriers. However, the PL intensity does not have a significant correlation with the annealing temperature for a C-rich a-SiC:H network, which refers to the formation of π-bond cluster as increasing carbon content. It is indicated that the thermal stability of C-rich a-Si1-xCx:H films is better than that of Si-like a-Si1-xCx :H films.

  13. Development of Diversified Methods for Chemical Modification of the 5,6-Double Bond of Uracil Derivatives Depending on Active Methylene Compounds

    Directory of Open Access Journals (Sweden)

    Kosaku Hirota

    2012-05-01

    Full Text Available The reaction of 5-halogenouracil and uridine derivatives 1 and 7 with active methylene compounds under basic conditions produced diverse and selective C-C bond formation products by virtue of the nature of the carbanions. Three different types of reactions such as the regioselective C-C bond formation at the 5- and 6-positions of uracil and uridine derivatives (products 2, 5, 8, 17, 20 and 21, and the formation of fused heterocycle derivatives 2,4-diazabicyclo[4.1.0]heptane (15 and 2,4-diazabicyclo-[4.1.0]nonane (16 via dual C-C bond formations at both the 5- and 6-positions were due to the different active methylene compounds used as reagents.

  14. Active vibration reduction of a flexible structure bonded with optimised piezoelectric pairs using half and quarter chromosomes in genetic algorithms

    International Nuclear Information System (INIS)

    The optimal placement of sensors and actuators in active vibration control is limited by the number of candidates in the search space. The search space of a small structure discretized to one hundred elements for optimising the location of ten actuators gives 1.73 × 1013 possible solutions, one of which is the global optimum. In this work, a new quarter and half chromosome technique based on symmetry is developed, by which the search space for optimisation of sensor/actuator locations in active vibration control of flexible structures may be greatly reduced. The technique is applied to the optimisation for eight and ten actuators located on a 500×500mm square plate, in which the search space is reduced by up to 99.99%. This technique helps for updating genetic algorithm program by updating natural frequencies and mode shapes in each generation to find the global optimal solution in a greatly reduced number of generations. An isotropic plate with piezoelectric sensor/actuator pairs bonded to its surface was investigated using the finite element method and Hamilton's principle based on first order shear deformation theory. The placement and feedback gain of ten and eight sensor/actuator pairs was optimised for a cantilever and clamped-clamped plate to attenuate the first six modes of vibration, using minimization of linear quadratic index as an objective function.

  15. cis-Dichloroplatinum(II) complexes tethered to dibenzo[c,h][1,6]naphthyridin-6-ones: synthesis and cytotoxicity in human cancer cell lines in vitro.

    Science.gov (United States)

    Desbois, Nicolas; Pertuit, David; Moretto, Johnny; Cachia, Claire; Chauffert, Bruno; Bouyer, Florence

    2013-11-01

    A novel family of cisplatin-type complexes tethered to dibenzo[c,h][1,6]naphthyridin-6-one topoisomerase inhibitor via a polymethylene chain and their nonplatinated counterparts were prepared. Their potential cytotoxicity was assessed in three human colorectal cancer cell lines HCT 116, SW480 and HT-29 and compared to the reference molecules cisplatin and oxaliplatin. Platinated compounds were poorly active whilst nonplatinated dibenzo[c,h][1,6]naphthyridin-6-one moieties exhibited higher cytotoxic properties than cisplatin and oxaliplatin whatever the length of the polymethylene chain; molecules containing the tri- and hexamethylene chain length were the most cytotoxic. PMID:24095763

  16. Calf thymus DNA binding/bonding properties of CC-1065 and analogs as related to their biological activities and toxicities.

    Science.gov (United States)

    Krueger, W C; Prairie, M D

    1992-03-01

    CC-1065 is a potent natural antitumor antibiotic that binds non-covalently and covalently (N-3 adenine adduct) in the minor groove of B-form DNA. Synthetic analogs of CC-1065 do not exhibit the delayed death toxicity of CC-1065 and are efficacious anticancer agents, some of them curative in murine tumor models. In an attempt to understand the different biological properties of CC-1065 and analogs, we have determined the following quantities for CC-1065, enantiomeric CC-1065, and three biologically active analogs and their enantiomers: the calf thymus DNA (CT-DNA) induced molar ellipticity of the adduct (or how rigidly the adduct is held in the right-hand conformation of the minor groove); the stability of the adduct with respect to long incubation times and to digestion by snake venom phosphodiesterase I (SVPD); the stabilizing effect on the CT-DNA helix of the covalently and non-covalently bound species with respect to thermal melting; and the CT-DNA binding/bonding (non-covalent/covalent) profiles at a low molar ratio of nucleotide to drug. The major observations from these studies are as follows: (i) molecules which show large DNA interaction parameters, stable adducts, and significant non-covalent binding exhibit delayed death toxicity; (ii) molecules which show intermediate DNA interaction parameters and stable adducts, but do not show significant non-covalent binding, do not exhibit delayed death toxicity and are biologically active; (iii) molecules which show small DNA interaction parameters and unstable DNA adducts are biologically inactive. The results suggest that a window exists in the affinity for the minor groove of DNA wherein an analog may possess the correct balance of toxicity and activity to make a useful anticancer agent. Outside of this window, the analog causes delayed deaths or has no significant biological activity. PMID:1312395

  17. Hydrodesulfurization on Transition Metal Catalysts: Elementary Steps of C-S Bond Activation and Consequences of Bifunctional Synergies

    Science.gov (United States)

    Yik, Edwin Shyn-Lo

    convergence to a single phase is expected and predictable from thermodynamics at a given temperature and sulfur chemical potential, metastability of two phases can exist. We demonstrate, through extensive characterization and kinetic evidence, such behaviors exist in Re, where structural disparities between its phases lead to kinetic hurdles that prevent interconversions between layered ReSx nanostructures and sulfur-covered Re metal clusters. Such features allowed, for the first time, direct comparisons of reaction rates at identical conditions on two disparate phases of the same transition metal identity. Rigorous assessments of kinetic and selectivity data indicated that more universal mechanistic features persist across all catalysts studied, suggesting that differences in their catalytic activity were the result of different densities of HDS sites, which appeared to correlate with their respective metal-sulfur bond energies. Kinetic responses and product distributions indicated that the consumption of thiophene proceeds by the formation of a partially-hydrogenated surface intermediate, which subsequently produces tetrahydrothiophene (THT) and butene/butane (C4) via primary routes on similar types of sites. These sites are formed from desorption of weakly-bound sulfur adatoms on sulfur-covered metal surfaces, which can occur when the heat of sulfur adsorption is sufficiently low at high sulfur coverage as a result of increased sulfur-sulfur repulsive interactions. Relative stabilities and differences in the molecularity of the respective transition states that form THT and C4 dictate product distributions. THT desulfurization to form C4 occurs via readsorption and subsequent dehydrogenation, evidenced by secondary rates that exhibited negative H2 dependences. These behaviors suggest that C-S bond activation occurs on a partially (un)saturated intermediate, analogous to behaviors observed in C-C bond scission reactions of linear and cycloalkanes on hydrogen-covered metal

  18. Soluble porous coordination polymers by mechanochemistry: from metal-containing films/membranes to active catalysts for aerobic oxidation.

    Science.gov (United States)

    Zhang, Pengfei; Li, Haiying; Veith, Gabriel M; Dai, Sheng

    2015-01-14

    Soluble porous coordination polymers from mechanochemical synthesis are presented through a coordination polymerization between highly contorted, rigid tetraphenol and a broad variety of transition metal ions. These polymers can be easily cast as metal-containing films or freestanding membranes. Importantly, as-made coordination polymers are highly active and stable in the aerobic oxidation of allylic C-H bonds. PMID:25389070

  19. Regioselective and Stepwise Syntheses of Functionalized BODIPY Dyes through Palladium-Catalyzed Cross-Coupling Reactions and Direct C-H Arylations.

    Science.gov (United States)

    Feng, Zeya; Jiao, Lijuan; Feng, Yuanmei; Yu, Changjiang; Chen, Na; Wei, Yun; Mu, Xiaolong; Hao, Erhong

    2016-08-01

    Regioselective and stepwise syntheses of a series of functionalized BODIPY dyes through palladium-catalyzed cross-coupling reactions and direct C-H arylations have been developed. In particular, this method allows the straightforward synthesis of 2,6-dibromo-3,5-diarylBODIPYs and 2-bromo-3-arylBODIPYs from polybrominated BODIPYs. The X-ray structure of intermediates 5a-c indicated that the palladium was first inserted into the C-Br bonds at 3,5-positions of brominated BODIPYs. The resulting 2,6-dibromo-substituted BODIPYs are potential long wavelength photosensitizers which are not easily accessible using previous methods. PMID:27362954

  20. TECHNICAL NOTE: A real-time active smart patch system for monitoring the integrity of bonded repair on an aircraft structure

    Science.gov (United States)

    Qing, Xinlin P.; Beard, Shawn J.; Kumar, Amrita; Hannum, Robert

    2006-06-01

    There currently exists a need to develop a cost-effective, in-service structural health monitoring (SHM) system for determining the initial quality of a bonded repair and assessing the long-term durability of the bonded repair on an aircraft structure. In this paper, a real-time active smart patch system (SPS) based on SMART layer technology is introduced for monitoring the integrity of bonded repairs. First, an overview of the SPS is given for typical metal and composite repairs. To illustrate the capability of the SPS, three applications are presented: (1) monitoring of the cure progress of the bonded repair adhesive, (2) detection of the initial artificial disbond between the composite patch and the metal structure, and (3) monitoring of damage in and around a bonded repair during fatigue cycling. The results show that, through the use of a real-time active SPS approach of using sensors placed in, on or around the repair, the initial quality and long-term durability of the repair can be evaluated and monitored.

  1. Structure, bonding, and catalytic activity of monodisperse, transition-metal-substituted CeO2 nanoparticles.

    Science.gov (United States)

    Elias, Joseph S; Risch, Marcel; Giordano, Livia; Mansour, Azzam N; Shao-Horn, Yang

    2014-12-10

    We present a simple and generalizable synthetic route toward phase-pure, monodisperse transition-metal-substituted ceria nanoparticles (M0.1Ce0.9O2-x, M = Mn, Fe, Co, Ni, Cu). The solution-based pyrolysis of a series of heterobimetallic Schiff base complexes ensures a rigorous control of the size, morphology and composition of 3 nm M0.1Ce0.9O2-x crystallites for CO oxidation catalysis and other applications. X-ray absorption spectroscopy confirms the dispersion of aliovalent (M(3+) and M(2+)) transition metal ions into the ceria matrix without the formation of any bulk transition metal oxide phases, while steady-state CO oxidation catalysis reveals an order of magnitude increase in catalytic activity with copper substitution. Density functional calculations of model slabs of these compounds confirm the stabilization of M(3+) and M(2+) in the lattice of CeO2. These results highlight the role of the host CeO2 lattice in stabilizing high oxidation states of aliovalent transition metal dopants that ordinarily would be intractable, such as Cu(3+), as well as demonstrating a rational approach to catalyst design. The current work demonstrates, for the first time, a generalizable approach for the preparation of transition-metal-substituted CeO2 for a broad range of transition metals with unparalleled synthetic control and illustrates that Cu(3+) is implicated in the mechanism for CO oxidation on CuO-CeO2 catalysts. PMID:25406101

  2. Rhodium-Catalyzed Highly Regioselective C-H Arylation of Imidazo[1,2-a]pyridines with Aryl Halides and Triflates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi; He, Lin [Guandong Pharmaceutical Univ., Zhongshan (China); Yin, Guoqiang; Wu, Guojie; Cui, Yingde [Zhongkai Univ. of Agriculture and Engineering, Guangzhou (China)

    2013-08-15

    A convenient Rh-catalyzed C-H arylation of imidazo[1,2-a]pyridines with a variety of aryl halides or triflates has been reported. This process afforded a range of biaryl compounds in excellent yields and showed high activity and broad scope.

  3. Implementation and Evaluation of Web-Based Learning Activities on Bonding and the Structure of Matter for 10-th Grade Chemistry

    Science.gov (United States)

    Frailich, Marcel

    This study deals with the development, implementation, and evaluation of web-based activities associated with the topic of chemical bonding , as taught in 10th grade chemistry. A website was developed entitled: "Chemistry and the Chemical Industry in the Service of Mankind", its URL is: http://stwww.weizmann.ac.il/g-chem/learnchem (Kesner, Frailich, & Hofstein, 2003). The main goal of this study was to assess the educational effectiveness of website activities dealing with the chemical bonding concept. These activities include visualization tools, as well as topics relevant to daily life and industrial applications. The study investigated the effectiveness of a web-based learning environment regarding the understanding of chemical bonding concepts, students' perceptions of the classroom learning environment, their attitudes regarding the relevance of learning chemistry to everyday life, and their interest in chemistry studies. As mentioned before, in the present study we focused on activities (from the website), all of which deal with chemical bonding concept. The following are the reasons for the decision to focus on this topic: (1) Chemical bonding is a key concept that is taught in 10th grade chemistry in high school. It provides the basis for many other chemistry topics that are taught later, and (2) Chemical bonding is a difficult for students using existing tools (e. g., static models in books, ball-and- stick models), which are insufficient to demonstrate the abstract nature phenomena associated with this topic. The four activities developed for this study are (1) models of the atomic structure, (2) metals -- structure and properties, (3) ionic substances in everyday life and in industry, and (4) molecular substances -- structure, properties, and uses. The study analyzed both quantitative and qualitative research. The quantitative tools of the study included: A Semantic Differential questionnaire and a Chemistry Classroom Web-Based Learning Environment

  4. Discovery of molluscicidal and cercaricidal activities of 3-substituted quinazolinone derivatives by a scaffold hopping approach using a pseudo-ring based on the intramolecular hydrogen bond formation.

    Science.gov (United States)

    Guo, Wei; Zheng, Lv-Yin; Li, Yong-Dong; Wu, Ren-Miao; Chen, Qiang; Yang, Ding-Qiao; Fan, Xiao-Lin

    2016-06-10

    Discovery of novel topological agents against Oncomelania hupensis snails and cercariae remains a significant challenge in current Schistosomiasis control. A pseudo-ring formed from salicylanilide by an intramolecular hydrogen bond led to the discovery of 3-substituted quinazolinone derivatives which showed a potent molluscicidal and cercaricidal activities. PMID:27017555

  5. Iridium-mediated Bond Activation and Water Oxidation as an Exemplary Case of CARISMA, A European Network for the Development of Catalytic Routines for Small Molecule Activation.

    Science.gov (United States)

    Licini, Giulia; Albrecht, Martin

    2015-01-01

    CARISMA is a currently running COST Action that pools leading European experts in computational and experimental chemistry to foster synergies for developing new catalytic processes for the transformation of abundant small molecules such as water, carbon dioxide, or ammonia into high-value chemicals and energy-relevant products. CARISMA promotes new collaborations, exchange of knowledge and skills, frontier training to young as well as established researchers, and a platform for the advancement of theoretical and experimental research in an iterative process, comprised of expertise in various connate domains including synthesis, catalysis, spectroscopy, kinetics, and computational chemistry. These interactions stimulate the discovery of new and efficient catalytic processes, illustrated in the second part of this contribution with the collaborative development of powerful iridium-based complexes for bond activation and water oxidation catalysis. PMID:26507475

  6. Accelerated Bonding of Magnesium and Aluminum with a CuNi/Ag/CuNi Sandwich Interlayer by Plasma-Activated Sintering

    Science.gov (United States)

    Wang, Yiyu; Rao, Mei; Li, Leijun; Luo, Guoqiang; Shen, Qiang; Zhang, Lianmeng

    2016-02-01

    Plasma-activated sintering (PAS) has been applied, for the first time, to join magnesium and aluminum using a CuNi/Ag/CuNi sandwich structural interlayer. A cleaning effect and high efficient plasma heating mode in PAS have contributed to forming a strong interfacial diffusion bond under low temperature 673 K (400 °C) and short dwell time (0.6 ks). The designed interlayer provides a diffusion barrier effect and an enhanced physical contact between the interfaces. Strong bonding has been achieved without forming the brittle Mg-Al intermetallics.

  7. Thermal shock and thermal cycling behaviour of amorphous a-C:H films on molybdenum substrates

    International Nuclear Information System (INIS)

    The thermal behaviour of a-C:H films (a stands for amorphous) deposited by the TEXTOR carbonization technique on molybdenum substrates was investigated in high power electron beam testing device for single and multiple shot sequences. The stationary thermal behaviour was also measured. The results for single shot testing are presented in a threshold damage diagram and show that the stability of a-C:H films on molybdenum is superior to that on steel. At higher or repeated loadings the films are converted gradually to molybdenum carbide. AES and SIMS depth profiling was used to investigate the concentration profiles and interface compositions of the films after various heat treatments. Their 1-h thermal stability on molybdenum extends to approximately 7000C in a stationary test. Results show that a-C:H films on molybdenum should be effective in shielding the molybdenum substrate from the plasma in a fusion device as long as the stated loading limits are not exceeded. (orig.)

  8. Compositional, structural and mechanical characteristics of nc-TiC/a-C:H nanocomposite films

    International Nuclear Information System (INIS)

    Nanocomposite nc-TiC/a-C:H films, with an unusual combination of superhardness, high elastic modulus and high elastic recovery, are prepared by filtered cathodic vacuum arc technique using the C2H2 gas as the precursor. The effects of filter coil current on compositional, structural and mechanical properties of the nc-TiC/a-C:H films have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy disperse spectroscopy (EDS), microindentation and tribotester measurements. XPS and Raman analyses show that composition and nanostructure of the nc-TiC/a-C:H films can be changed by varying the filter coil current. By selecting the proper value of filter coil current, 2.5 A, one can remarkably enhance the mechanical properties of films such as superhardness (43.6 GPa). The superhardness can be ascribed to the phase variation and the nanostructure.

  9. Isotopic Effects on Covalent Bond Confined in a Penetrable Sphere.

    Science.gov (United States)

    Sarsa, Antonio; Alcaraz-Pelegrina, José M; Le Sech, Claude

    2015-11-12

    A model of confinement of the covalent bond by a finite potential beyond the Born-Oppenheimer approximation is presented. A two-electron molecule is located at the center of a penetrable spherical cavity. The Schrödinger equation has been solved by using the diffusion Monte Carlo method. Total energies, internuclear distances, and vibrational frequencies of the confined molecular system have been obtained. Even for confining potentials of a few electronvolts, a noticeable increase in the bond energy and the nuclear vibrational frequency is observed, and the internuclear distance is lowered. The gap between the zero point energy of different molecular isotopes increases with confinement. The confinement of the electron pair might play a role in chemical reactivity, providing an alternative explanation for the tunnel effect, when large values of primary kinetic isotopic effect are observed. The Swain-Schaad relation is still verified when confinement changes the zero point energy. A semiquantitative illustration is proposed using the data relative to an hydrogen transfer involving a C-H cleavage catalyzed by the bovine serum amine oxidase. Changes on the confining conditions, corresponding to a confinement/deconfinement process, result in a significant decrease in the activation energy of the chemical transformation. It is proposed that confinement/deconfinement of the electron-pair bonding by external electrostatic forces inside the active pocket of an enzyme could be one of the basic mechanisms of the enzyme catalysis. PMID:26484576

  10. The Effect of Artificial Aging on The Bond Strength of Heat-activated Acrylic Resin to Surface-treated Nickel-chromium-beryllium Alloy

    Science.gov (United States)

    Al Jabbari, Youssef S.; Zinelis, Spiros; Al Taweel, Sara M.; Nagy, William W.

    2016-01-01

    Purpose The debonding load of heat-activated polymethylmethacrylate (PMMA) denture base resin material to a nickel-chromium-beryllium (Ni-Cr-Be) alloy conditioned by three different surface treatments and utilizing two different commercial bonding systems was investigated. Materials and Methods Denture resin (Lucitone-199) was bonded to Ni-Cr-Be alloy specimens treated with Metal Primer II, the Rocatec system with opaquer and the Rocatec system without opaquer. Denture base resin specimens bonded to non-treated sandblasted Ni-Cr-Be alloy were used as controls. Twenty samples for each treatment condition (80 specimens) were tested. The 80 specimens were divided into two categories, thermocycled and non-thermocycled, containing four groups of ten specimens each. The non-thermocycled specimens were tested after 48 hours’ storage in room temperature water. The thermocycled specimens were tested after 2,000 cycles in 4°C and 55°C water baths. The debonding load was calculated in Newtons (N), and collected data were subjected by non parametric test Kruskal-Wallis One Way Analysis of Variance on Ranks and Dunn’s post hoc test at the α = 0.05. Results The Metal Primer II and Rocatec system without opaquer groups produced significantly higher bond strengths (119.9 and 67.6 N), respectively, than did the sandblasted and Rocatec system with opaquer groups, where the bond strengths were 2.6 N and 0 N, respectively. The Metal Primer II was significantly different from all other groups (P<0.05). The bond strengths of all groups were significantly decreased (P<0.05) after thermocycling. Conclusions Although thermocycling had a detrimental effect on the debonding load of all surface treatments tested, the Metal Primer II system provided higher values among all bonding systems tested, before and after thermocycling. PMID:27335613

  11. Supramolecular hydrogen-bonding patterns of co-crystals containing the active pharmaceutical ingredient (API) phloroglucinol and N-heterocycles.

    Science.gov (United States)

    Cvetkovski, Aleksandar; Bertolasi, Valerio; Ferretti, Valeria

    2016-06-01

    The active pharmaceutical ingredient phloroglucinol (PHL) has been taken as an illustrative molecule to explore the intermolecular interactions which can be established with other molecular entities to build PHL pharmaceutical co-crystals. The crystal structures of five newly synthesized co-crystals are reported, where PHL is crystallized with N-heterocycles, namely 2-hydroxy-6-methylpyridine (1), 2,4-dimethyl-6-hydroxypyrimidine (2), 4-phenylpyridine (3), 2-hydroxypyridine (4) and 2,3,5,6-tetramethylpyrazine (5). The structural characteristics of these co-crystals, as far as the hydrogen-bonding networks and the crystalline architectures are concerned, are strongly dependent on the chemical features of the coformer molecules, as well as on their size and shape. A detailed analysis of the intermolecular interactions established in all the PHL co-crystals of known structures has allowed the recognition of some regularities in the packing modes that can be useful in the design of new supramolecular adducts forming predictable structural motifs. PMID:27240764

  12. Nature of chemical bond through positron annihilation

    International Nuclear Information System (INIS)

    Positron annihilation is an important alternative to Compton scattering for determination of electron momentum distribution. The possibility of studying the nature of chemical bond by positron annihilation technique is reviewed in this paper. General concepts connected with momentum space and chemical bond have been outlined. Estimation of positron wavefunction at carbon and hydrogen sites and the calculation of electron momentum distribution of C-H and C-C bonds are discussed. The annihilation with sigma electrons broadens the angular correlation curve while the annihilation with π electrons narrows the curve. The most significant part of this paper is the investigation of participation of d-orbital of sulphur in chemical bonding. Whether or not ligand perturbation is necessary for d-orbital contraction and consequent participation in bonding is controversial till now. A study of angular correlation of positron annihilation radiation on organic sulphides and sulphones is a direct evidence to conclude that ligand perturbation is necessary. (author)

  13. Modeling study of oxygenated fuels on diesel combustion: Effects of oxygen concentration, cetane number and C/H ratio

    International Nuclear Information System (INIS)

    Highlights: • The effects of oxygenated fuels on diesel combustion are extensively investigated. • CO and soot emissions are reduced with the increase of oxygen concentration. • The C–O bond in the oxygenated fuels inhibits the formation of soot precursor C2H2. • Small intermediates such as C2H4 and C2H6 are significantly reduced. • Oxygen concentration seems to be the dominating factor affecting the emissions. - Abstract: The present modeling study aims to gain better insights on the effects of oxygenated fuels on the diesel oxidation and emission formation processes under realistic engine operating conditions. To do that, various blend fuels formulated from diesel, biodiesel, ethanol and DMC fuels were obtained with different oxygen concentrations, cetane numbers and C/H ratios. Simulations were conducted using the coupled KIVA–CHEMKIN code on a light duty diesel engine at a fixed engine speed of 2400 rpm under full load conditions. Constructed numerical simulation models integrated with detailed chemical kinetics were validated against the experimental results with reliable accuracies. Simulation results revealed that as the overall oxygen concentration of the blend fuel increased, significant beneficial effects were shown with reduced NOx, CO and soot emissions. Particularly, with the increase of oxygen concentration, the peak CO concentration and its final emission level were found to be remarkably reduced due to the fuel borne oxygen, reduced carbon influx as well as the possibility accelerated CO oxidation rate. More tangible reductions were shown on the soot emissions probably because the C–O bond in the oxygenated blend fuels had played an important role in inhibiting the carbon atoms from soot formation. Furthermore, as oxygenated fuels were added, the peak concentration of the soot precursor C2H2 species and small hydrocarbon intermediates such as C2H4 and C2H6 were also significantly reduced. In general, it was found that compared to the

  14. Activation of the carbon-fluorine bonds in coordination compounds; Activacion de enlaces carbon-fluor en compuestos de coordinacion

    Energy Technology Data Exchange (ETDEWEB)

    Torrens, H. [Universidad Nacional Autonoma de Mexico, Facultad de Quimica, 04510 Mexico D.F. (Mexico)

    2000-07-01

    Activation of the carbon-fluorine bond is of upmost importance in several chemical processes. In search of synthetic alternatives to promote C-F bond cleavage in arylic systems, several square planar palladium and platinum compounds bearing fluorothiolates and fluorophosphines have been studied. In this paper molecular structures are shown for the following compounds trans-((SC{sub 6}F{sub 5})(P(C{sub 6}F{sub 5}){sub 2}(C{sub 6}H{sub 5}))(Pd({mu}-SC{sub 6}F{sub 5}){sub 2} Pd(SC{sub 6}F{sub 5})(P(C{sub 6}F{sub 5}){sub 2} (C{sub 6}H{sub 5})), cis ((SC{sub 6}F{sub 5}) P(C{sub 6}F{sub 5}){sub 2} (C{sub 6}H{sub 5}) Pt({mu}-SC{sub 6}F{sub 5}){sub 2} Pt(SC{sub 6}F{sub 5}) P(C{sub 6}F{sub 5}){sub 2} (C{sub 6}H{sub 5})), trans Pd ({mu}-SC{sub 6}F{sub 5}){sub 2} Pt(SC{sub 6}F{sub 5})(P(C{sub 6}F{sub 5})(C{sub 6}H{sub 5}){sub 2})), Pt (SC{sub 6}F{sub 5}){sub 2} (C{sub 6}F{sub 5}SC{sub 6}F{sub 4} P(C{sub 6}H{sub 5}){sub 2}))((SC{sub 6}F{sub 5}){sub 2} Pt ({mu}-(SC{sub 6}F{sub 5}){sub 2} Pt(SC{sub 6}F{sub 5}){sub 2}){sup 2-} , (SC{sub 6}HF{sub 4}){sub 2} Pt({mu}-SC{sub 6}HF{sub 4}){sub 2} Pt(SC{sub 6}HF{sub 4}){sub 2}){sup 2-} and ((SC{sub 6}F{sub 4}CF{sub 3}-4){sub 2} Pt (SC{sub 6}F{sub 4}CF{sub 3}-4){sub 2}){sup 2-} . (Author)

  15. Density function theoretical study on the complex involved in Th atom-activated C–C bond in C2H6

    Science.gov (United States)

    Qing-Qing, Wang; Peng, Li; Tao, Gao; Hong-Yan, Wang; Bing-Yun, Ao

    2016-06-01

    Density functional theory (DFT) calculations are performed to investigate the reactivity of Th atom toward ethane C–C bond activation. A comprehensive description of the reaction mechanisms leading to two different reaction products is presented. We report a complete exploration of the potential energy surfaces by taking into consideration different spin states. In addition, the intermediate and transition states along the reaction paths are characterized. Total, partial, and overlap population density of state diagrams and analyses are also presented. Furthermore, the natures of the chemical bonding of intermediate and transition states are studied by using topological method combined with electron localization function (ELF) and Mayer bond order. Infrared spectrum (IR) is obtained and further discussed based on the optimized geometries. Project supported by the National Natural Science Foundation of China (Grant Nos. 21371160, 21401173, and 11364023).

  16. Development of a Direct Photocatalytic C-H Fluorination for the Preparative Synthesis of Odanacatib.

    Science.gov (United States)

    Halperin, Shira D; Kwon, Daniel; Holmes, Michael; Regalado, Erik L; Campeau, Louis-Charles; DiRocco, Daniel A; Britton, Robert

    2015-11-01

    Late-stage C-H fluorination is an appealing reaction for medicinal chemistry. However, the application of this strategy to process research appears less attractive due to the formation and necessary purification of mixtures of organofluorines. Here we demonstrate that γ-fluoroleucine methyl ester, an intermediate critical to the large-scale synthesis of odanacatib, can be accessed directly from leucine methyl ester using a combination of the decatungstate photocatalyst and N-fluorobenzenesulfonimide in flow. This efficient C-H fluorination reaction compares favorably with several generations of classical γ-fluoroleucine process syntheses. PMID:26484983

  17. Study on the HPHT synthetic diamond crystal from Fe-C(H)system and its significance

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Investigations of crystal habit,micro-topographic imaging,micro-composition and micro-structural analysis of HPHT synthetic diamonds from the Fe-C(H)system indicate that most of them have an octahedral habit.The crystals grow mainly layer-to-layer from center to periphery.HPHT synthetic diamond is smaller in size than naturel diamond because it only goes through nucleation and growth in the early stage.In the middle and late stages,due to the coalescence of diamond grains related to differences of surface energy,the growth of HPHT synthetic diamond iS limited.The active energy (E) of transforming single nitrogen into a nitrogen-pair is lowered and the time of transforming single nitrogen into a nitrogen-pair is shortened because of the existence of hydrogen.Therefore,aggregate nitrogen(A-centers)may exist in synthetic diamond from HPHT and explosive detonation processes.It needs further discussion on a worldwide view that the time of natural diamond formation extrectad from nitrogen aggregation is some hundred million years.Consideration of the way in which Surface energy influences the growth of diamond can help to understand some of the remaining issues(e.g.growth mechanism,etc.)in the HPHT synthetic process and effectively explain the formation of naturel diamond in terms of HPHT thermodynamic theory.Especially,it is important to pay more attention to the influence of hydrogen on surface energy in that hydrogen may be a"bridge"for explaining the formation of HPHT synthetic and natural diamond.

  18. Mechanistic Insights into C-H Oxidations by Ruthenium(III)-Pterin Complexes: Impact of Basicity of the Pterin Ligand and Electron Acceptability of the Metal Center on the Transition States.

    Science.gov (United States)

    Mitome, Hiroumi; Ishizuka, Tomoya; Kotani, Hiroaki; Shiota, Yoshihito; Yoshizawa, Kazunari; Kojima, Takahiko

    2016-08-01

    A ruthenium(II) complex, [Ru(dmdmp)Cl(MeBPA)] (2) (Hdmdmp = N,N-dimethyl-6,7-dimethylpterin, MeBPA = N-methyl-N,N-bis(pyridylmethyl)amine), having a pterin derivative as a proton-accepting ligand, was synthesized and characterized. Complex 2 shows higher basicity than that of a previously reported Ru(II)-pterin complex, [Ru(dmdmp) (TPA)](+) (1) (TPA = tris(2-pyridylmethyl)amine). On the other hand, 1e(-)-oxidized species of 1 (1OX) exhibits higher electron-acceptability than that of 1e(-)-oxidized 2 (2OX). Bond dissociation enthalpies (BDE) of the two Ru(II) complexes having Hdmdmp as a ligand in proton-coupled electron transfer (PCET) to generate 1OX and 2OX were calculated to be 85 kcal mol(-1) for 1OX and 78 kcal mol(-1) for 2OX. The BDE values are large enough to perform H atom transfer from C-H bonds of organic molecules to the 1e(-)-oxidized complexes through PCET. The second-order rate constants (k) of PCET oxidation reactions were determined for 1OX and 2OX. The logarithms of normalized k values were proportional to the BDE values of C-H bonds of the substrates with slopes of -0.27 for 1OX and -0.44 for 2OX. The difference between 1OX and 2OX in the slopes suggests that the transition states in PCET oxidations of substrates by the two complexes bear different polarization, as reflection of difference in the electron acceptability and basicity of 1OX and 2OX. The more basic 2OX attracts a proton from a C-H bond via a more polarized transition state than that of 1OX; on the contrary, the more electron-deficient 1OX forms less polarized transition states in PCET oxidation reactions of C-H bonds. PMID:27403587

  19. Cobalt-catalyzed redox-neutral synthesis of isoquinolines:C-H activation assisted by an oxidizing N-S bond%三价钴催化下N-S键辅助的非氧化条件下经碳氢活化合成异喹啉

    Institute of Scientific and Technical Information of China (English)

    王芬; 王强; 包明; 李兴伟

    2016-01-01

    异喹啉是非常重要的杂环化合物,广泛应用于有机合成中,也是构成药物和材料分子的核心骨架。很多异喹啉类的生物碱都由异喹啉基本骨架构成,它们都有一定药理活性和生物活性,包括抗真菌、抗癌、抗心律失常、阵痛麻醉和降血压等功效。迄今已知的含异喹啉骨架的生物碱超过1000种,是生物碱中最多的一类。传统的合成异喹啉的方法需要官能化的原料和强酸,反应条件比较苛刻,合成步骤繁琐。例如Larock课题组利用钯催化将邻溴官能化的亚胺与炔烃环化偶联,合成了一系列异喹啉化合物。而过渡金属催化合成异喹啉是一种能够有效合成多种取代基异喹啉的方法。在过去的几十年中,通过碳氢活化策略合成杂环化合物的方法得到迅猛发展,从而使得大量的芳基化合物都能作为反应的起始原料。尤其是铑、铱、钯、钌等过渡金属都能催化芳烃的碳氢活化,从而合成异喹啉化合物。 Fagnou课题组最早报道了氧化条件下利用三价铑催化剂经碳氢键活化与炔烃偶联合成异喹啉的方法。随后,众多研究组利用氧化型导向基策略在无外加氧化剂条件下高效、高选择性地合成了异喹啉。除了利用三价铑催化剂之外,利用二价钌催化剂通过碳氢活化策略也能实现类似反应。但是,这些反应体系都必须使用铑和钌等贵金属催化剂,极大地限制了该合成异喹啉方法的应用前景。近年来,数个研究组将地球上储量丰富、便宜有效的钴络合物作为催化剂应用到芳烃的碳氢键活化反应中,在简单的反应条件下合成了各种杂环化合物。对于一些反应,三价钴催化与三价铑催化能形成互补。最近, Kanai, Ackermann和Sundararaju几乎同时报道了三价钴催化肟谜的碳氢键活化,并在无外加氧化剂条件下实现了其与炔烃的偶联反应,高效地合成了异喹啉,在该类反应中以氮–氧键断裂作为内部氧化剂。但是在钴催化条件下氧化性的氮–硫键作为内部氧化剂辅助碳氢键活化的反应尚无报道。本课题组最近报道了芳基酮的N-亚磺酰亚胺与烯烃和胺化试剂的偶联反应,经N–S键断裂,高效合成了喹唑啉。本文利用三价钴催化剂在无外加氧化剂条件下实现了芳基酮N-亚磺酰亚胺与炔烃的偶联,反应经历了碳氢键活化和氮硫键断裂得到异喹啉。此反应对端炔和内炔底物均适用。为了初步了解反应机理,我们利用分子内竞争的方法进行了动力学同位素效应测定,结果表明碳氢键断裂过程可能是反应的决速步骤。结合文献结果,提出了可能的反应机理。%A redox‐neutral avenue to access isoquinolines has been realized by a Co(III)‐catalyzed C–H activa‐tion process. Starting from readily available N‐sulfinyl imine substrates and alkynes, the reaction occurred via N–S cleavage with broad substrate scope and functional group compatibility in the presence of cost‐effective cobalt catalysts.

  20. Active-Transient Liquid Phase (A-TLP) Bonding of Pure Aluminum Matrix Composite Reinforced with Short Alumina Fiber Using Al-12Si-xTi Foils as Active Interlayer

    Science.gov (United States)

    Zhang, Guifeng; Su, Wei; Suzumura, Akio

    2016-02-01

    To optimize both the interlayer composition design route and pressure for joining aluminum matrix composite reinforced with short alumina fiber (as-cast 30 vol pct Al2O3sf/Al), traditional transient liquid phase (TLP) bonding using Al-12Si and Cu interlayer and active-TLP (A-TLP) bonding using an active Ti-containing interlayer (Al-12Si-xTi, x = 0.1, 0.5, and 1 wt pct) under the same condition [883 K (610 °C) × 30 minutes × 1 or 0.015 MPa in flowing argon] were compared in terms of interfacial wettability, bond seam microstructure, shear strength, and fracture path. It was found that not only the Ti content but also the pressure are critical factors affecting interfacial wettability and bond seam microstructure. The improvement in wettability by adding Ti as an active element were confirmed by reduction of expulsion of liquid interlayer, elimination of interfacial gap, higher shear strength and favorable fracture path (partially through bond seam and the composite). Because of the incubation period for wetting, reducing the pressure after melting of the interlayer could further increase joint shear strength by thickening the remaining bond seam of solid-solution matrix and decreasing fraction of the in situ newly formed Al-Si-Ti IMC phase (short bar shape) within the bond seam. The maximum shear strength of 88.6 MPa (99 pct of the as-cast composite) was obtained by adding trace Ti content (0.5 Ti wt pct) addition and using low pressure (0.015 MPa). The results showed that suitable combination of Ti content and pressure pattern is required for improving both wettability and bond seam microstructure.

  1. Active-Transient Liquid Phase (A-TLP) Bonding of Pure Aluminum Matrix Composite Reinforced with Short Alumina Fiber Using Al-12Si- xTi Foils as Active Interlayer

    Science.gov (United States)

    Zhang, Guifeng; Su, Wei; Suzumura, Akio

    2016-06-01

    To optimize both the interlayer composition design route and pressure for joining aluminum matrix composite reinforced with short alumina fiber (as-cast 30 vol pct Al2O3sf/Al), traditional transient liquid phase (TLP) bonding using Al-12Si and Cu interlayer and active-TLP (A-TLP) bonding using an active Ti-containing interlayer (Al-12Si- xTi, x = 0.1, 0.5, and 1 wt pct) under the same condition [883 K (610 °C) × 30 minutes × 1 or 0.015 MPa in flowing argon] were compared in terms of interfacial wettability, bond seam microstructure, shear strength, and fracture path. It was found that not only the Ti content but also the pressure are critical factors affecting interfacial wettability and bond seam microstructure. The improvement in wettability by adding Ti as an active element were confirmed by reduction of expulsion of liquid interlayer, elimination of interfacial gap, higher shear strength and favorable fracture path (partially through bond seam and the composite). Because of the incubation period for wetting, reducing the pressure after melting of the interlayer could further increase joint shear strength by thickening the remaining bond seam of solid-solution matrix and decreasing fraction of the in situ newly formed Al-Si-Ti IMC phase (short bar shape) within the bond seam. The maximum shear strength of 88.6 MPa (99 pct of the as-cast composite) was obtained by adding trace Ti content (0.5 Ti wt pct) addition and using low pressure (0.015 MPa). The results showed that suitable combination of Ti content and pressure pattern is required for improving both wettability and bond seam microstructure.

  2. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen,and Zhejiang and Guangdong provinces to issue bonds for the first time.How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the Shanghai Securities Journal.Edited excerpts follow.

  3. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen, and Zhejiang and Guangdong provinces to issue bonds for the first time. How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the ShanghaiSecuritiesJournal. Edited excerpts follow:

  4. Electrochemically induced C-H functionalization using bromide ion/2,2,6,6-tetramethylpiperidinyl-N-oxyl dual redox catalysts in a two-phase electrolytic system

    International Nuclear Information System (INIS)

    Highlights: •Electrocatalytic C-H bond functionalization of tetrahydroisoquinolines is reported. •The transformation is mediated by a bromide ion/TEMPO dual redox catalyst system. •The transformation is conducted in a two-phase electrolytic medium. •The mechanism is proposed to proceed via a sequence of oxidation and addition reactions involving water as a nucleophile. •The procedure features wide substrate scope, the use of mild reaction conditions. -- Abstract: The electrochemical oxidative functionalization of benzylic C-H bonds, mediated by a dual bromide ion/2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) redox catalyst system in a two-phase electrolytic medium, has been explored using cyclic voltammetry (CV) and preparative electrolysis techniques. The results show that electron transfer between TEMPO+ and a neutral substrate occurs with an efficiency that depends upon the presence of a base. The preparative scale electrolysis led to the formation of dihydro-isoquinolinones, isochromanone and xanthenone in moderate to excellent yields. On the basis of the CV analysis and preparative electrolysis results, a reaction mechanism is proposed

  5. C$^+$/H$_2$ Gas in Star-Forming Clouds and Galaxies

    CERN Document Server

    Nordon, Raanan

    2016-01-01

    We present analytic theory for the total column density of singly ionized carbon (C$^+$) in the optically thick photon dominated regions (PDRs) of far-UV irradiated (star-forming) molecular clouds. We derive a simple formula for the C$^+$ column as a function of the cloud (hydrogen) density, the far-UV field intensity, and metallicity, encompassing the wide range of galaxy conditions. We verify our analysis with detailed numerical PDR models. For optically thick gas, most of the C$^+$ column is mixed with hydrogen that is primarily molecular (H$_2$), and this "C$^+$/H$_2$" gas layer accounts for almost all of the `CO-dark' molecular gas in PDRs. The C$^+$/H$_2$ column density is limited by dust shielding and is inversely proportional to the metallicity down to $\\sim$0.1 solar. At lower metallicities, H$_2$ line blocking dominates and the C$^+$/H$_2$ column saturates. Applying our theory to CO surveys in low redshift spirals we estimate the fraction of C$^+$/H$_2$ gas out of the total molecular gas to be typic...

  6. Hydrodesulfurization on Transition Metal Catalysts: Elementary Steps of C-S Bond Activation and Consequences of Bifunctional Synergies

    Science.gov (United States)

    Yik, Edwin Shyn-Lo

    convergence to a single phase is expected and predictable from thermodynamics at a given temperature and sulfur chemical potential, metastability of two phases can exist. We demonstrate, through extensive characterization and kinetic evidence, such behaviors exist in Re, where structural disparities between its phases lead to kinetic hurdles that prevent interconversions between layered ReSx nanostructures and sulfur-covered Re metal clusters. Such features allowed, for the first time, direct comparisons of reaction rates at identical conditions on two disparate phases of the same transition metal identity. Rigorous assessments of kinetic and selectivity data indicated that more universal mechanistic features persist across all catalysts studied, suggesting that differences in their catalytic activity were the result of different densities of HDS sites, which appeared to correlate with their respective metal-sulfur bond energies. Kinetic responses and product distributions indicated that the consumption of thiophene proceeds by the formation of a partially-hydrogenated surface intermediate, which subsequently produces tetrahydrothiophene (THT) and butene/butane (C4) via primary routes on similar types of sites. These sites are formed from desorption of weakly-bound sulfur adatoms on sulfur-covered metal surfaces, which can occur when the heat of sulfur adsorption is sufficiently low at high sulfur coverage as a result of increased sulfur-sulfur repulsive interactions. Relative stabilities and differences in the molecularity of the respective transition states that form THT and C4 dictate product distributions. THT desulfurization to form C4 occurs via readsorption and subsequent dehydrogenation, evidenced by secondary rates that exhibited negative H2 dependences. These behaviors suggest that C-S bond activation occurs on a partially (un)saturated intermediate, analogous to behaviors observed in C-C bond scission reactions of linear and cycloalkanes on hydrogen-covered metal

  7. Conjugation-Driven "Reverse Mars-van Krevelen"-Type Radical Mechanism for Low-Temperature C-O Bond Activation.

    Science.gov (United States)

    Mironenko, Alexander V; Vlachos, Dionisios G

    2016-07-01

    C-O bond activation on monofunctional catalysts (metals, carbides, and oxides) is challenging due to activity constraints imposed by energy scaling relationships. Yet, contrary to predictions, recently discovered multifunctional metal/metal oxide catalysts (e.g., Rh/ReOx, Rh/MoOx, Ir/VOx) demonstrate unusually high C-O scission activity at moderate temperatures. Herein, we use extensive density functional theory calculations, first-principles microkinetic modeling, and electronic structure analysis to elucidate the metal/metal oxide synergy in the Ru/RuO2 catalyst, which enables up to 76% yield of the C-O scission product (2-methyl furan) in catalytic transfer hydrogenolysis of furfural at low temperatures. Our key mechanistic finding is a facile radical-mediated C-O bond activation on RuO2 oxygen vacancies, which directly leads to a weakly bound final product. This is the first time the radical reduction mechanism is reported in heterogeneous catalysis at temperatures <200 °C. We attribute the unique catalytic properties to the formation of a conjugation-stabilized furfuryl radical upon C-O bond scission, the strong hydroxyl affinity of oxygen vacancies due to the metallic character of RuO2, and the acid-base heterogeneity of the oxide surface. The conjugation-driven radical-assisted C-O bond scission applies to any catalytic surface that preserves the π-electron system of the reactant and leads to C-O selectivity enhancement, with notable examples including Cu, H-covered Pd, self-assembled monolayers on Pd, and oxygen-covered Mo2C. Furthermore, we reveal the cooperativity of active sites in multifunctional catalysts. The mechanism is fully consistent with kinetic studies and isotopic labeling experiments, and the insights gained might prove useful more broadly in overcoming activity constraints induced by energy scaling relationships. PMID:27281043

  8. A Substrate-Assisted Mechanism of Nucleophile Activation in a Ser-His-Asp Containing C-C Bond Hydrolase

    Energy Technology Data Exchange (ETDEWEB)

    Ruzzini, Antonio C.; Bhowmik, Shiva; Ghosh, Subhangi; Yam, Katherine C.; Bolin, Jeffrey T.; Eltis, Lindsay D. [Purdue; (UBC)

    2013-11-12

    The meta-cleavage product (MCP) hydrolases utilize a Ser–His–Asp triad to hydrolyze a carbon–carbon bond. Hydrolysis of the MCP substrate has been proposed to proceed via an enol-to-keto tautomerization followed by a nucleophilic mechanism of catalysis. Ketonization involves an intermediate, ESred, which possesses a remarkable bathochromically shifted absorption spectrum. We investigated the catalytic mechanism of the MCP hydrolases using DxnB2 from Sphingomonas wittichii RW1. Pre-steady-state kinetic and LC ESI/MS evaluation of the DxnB2-mediated hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid to 2-hydroxy-2,4-pentadienoic acid and benzoate support a nucleophilic mechanism catalysis. In DxnB2, the rate of ESred decay and product formation showed a solvent kinetic isotope effect of 2.5, indicating that a proton transfer reaction, assigned here to substrate ketonization, limits the rate of acylation. For a series of substituted MCPs, this rate was linearly dependent on MCP pKa2nuc ~ 1). Structural characterization of DxnB2 S105A:MCP complexes revealed that the catalytic histidine is displaced upon substrate-binding. The results provide evidence for enzyme-catalyzed ketonization in which the catalytic His–Asp pair does not play an essential role. The data further suggest that ESred represents a dianionic intermediate that acts as a general base to activate the serine nucleophile. This substrate-assisted mechanism of nucleophilic catalysis distinguishes MCP hydrolases from other serine hydrolases.

  9. Cyclopalladated organosilane-tethered thiosemicarbazones: novel strategies for improving antiplasmodial activity.

    Science.gov (United States)

    Adams, Muneebah; Barnard, Linley; de Kock, Carmen; Smith, Peter J; Wiesner, Lubbe; Chibale, Kelly; Smith, Gregory S

    2016-04-01

    Two series of ferrocenyl- and aryl-derived cyclopalladated organosilane thiosemicarbazone complexes were synthesised via C-H bond activation. Selected compounds were evaluated for in vitro antiplasmodial activity against the chloroquine-sensitive (NF54) and chloroquine-resistant (Dd2) strains of the human malaria parasite Plasmodium falciparum. Cyclopalladation of the thiosemicarbazones resulted in antiplasmodial activities in the low micromolar range. PMID:26911403

  10. Distinguishing Bonds.

    Science.gov (United States)

    Rahm, Martin; Hoffmann, Roald

    2016-03-23

    The energy change per electron in a chemical or physical transformation, ΔE/n, may be expressed as Δχ̅ + Δ(VNN + ω)/n, where Δχ̅ is the average electron binding energy, a generalized electronegativity, ΔVNN is the change in nuclear repulsions, and Δω is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoretical estimates of the first terms. Previously obtained consequences of this energy partitioning are extended here to a different analysis of bonding in a great variety of diatomics, including more or less polar ones. Arguments are presented for associating the average change in electron binding energy with covalence, and the change in multielectron interactions with electron transfer, either to, out, or within a molecule. A new descriptor Q, essentially the scaled difference between the Δχ̅ and Δ(VNN + ω)/n terms, when plotted versus the bond energy, separates nicely a wide variety of bonding types, covalent, covalent but more correlated, polar and increasingly ionic, metallogenic, electrostatic, charge-shift bonds, and dispersion interactions. Also, Q itself shows a set of interesting relations with the correlation energy of a bond. PMID:26910496

  11. Synthesis of Biotin Linkers with the Activated Triple Bond Donor [p-(N-propynoylaminotoluic Acid] (PATA for Efficient Biotinylation of Peptides and Oligonucleotides

    Directory of Open Access Journals (Sweden)

    Martina Jezowska

    2012-11-01

    Full Text Available Biotin is an important molecule for modern biological studies including, e.g., cellular transport. Its exclusive affinity to fluorescent streptavidin/avidin proteins allows ready and specific detection. As a consequence methods for the attachment of biotin to various biological targets are of high importance, especially when they are very selective and can also proceed in water. One useful method is Hüisgen dipolar [3+2]-cycloaddition, commonly referred to as “click chemistry”. As we reported recently, the activated triple bond donor p-(N-propynoylaminotoluic acid (PATA gives excellent results when used for conjugations at submicromolar concentrations. Thus, we have designed and synthesized two biotin linkers, with different lengths equipped with this activated triple bond donor and we proceeded with biotinylation of oligonucleotides and C-myc peptide both in solution and on solid support with excellent yields of conversion.

  12. Theoretical study of optical activity of 1:1 hydrogen bond complexes of water with S-warfarin.

    Science.gov (United States)

    Dadsetani, Mehrdad; Abdolmaleki, Ahmad; Zabardasti, Abedin

    2016-11-01

    The molecular interaction between S-warfarin (SW) and a single water molecule was investigated using the B3LYP method at 6-311++G(d,p) basis set. The vibrational spectra of the optimized complexes have been investigated for stabilization checking. Quantum theories of atoms in molecules, natural bond orbitals, molecular electrostatic potentials and energy decomposition analysis methods have been applied to analyze the intermolecular interactions. The intermolecular charge transfer in the most stable complex is in the opposite direction from those in the other complexes. The optical spectra and the hyperpolarizabilities of SW-water hydrogen bond complexes have been computed. PMID:27294546

  13. Deposition of a-C:H films on a nanotrench pattern by bipolar PBII&D

    Science.gov (United States)

    Hirata, Yuki; Nakahara, Yuya; Nagato, Keisuke; Choi, Junho

    2016-06-01

    In this study, hydrogenated amorphous carbon (a-C:H) films were deposited on a nanotrench pattern (300 nm pitch, aspect ratio: 2.0) by bipolar-type plasma based ion implantation and deposition technique (bipolar PBII&D), and the effects of bipolar pulse on the film properties were investigated. Moreover, the behaviour of ions and radicals surrounding the nanotrench was analyzed to clarify the coating mechanism and properties of the a-C:H films on the nanotrench. Further, thermal nanoimprint lithography was carried out using the nanotrench pattern coated with a-C:H films as the mold, and the mold release properties were evaluated. All nanotrench surfaces were successfully coated with the a-C:H films, but the film thickness on the top, sidewall, and bottom surfaces of the trench were not uniform. The surface roughness of the a-C:H films was found to decrease at a higher positive voltage; this happens due to the higher electron temperature around the nanotrench because of the surface migration of plasma particles arrived on the trench. The effects of the negative voltage on the behaviour of ions and radicals near the sidewall of the nanotrench are quite similar to those near the microtrench reported previously (Park et al 2014 J. Phys. D: Appl. Phys. 47 335306). However, the positive pulse voltage was also found to affect the behaviour of ions and radicals near the sidewall surface. The incident angles of ions on the sidewall surface increased with the positive pulse voltage because the energy of incoming ions on the trench decreases with increasing positive voltage. Moreover, the incident ion flux on the sidewall is affected by the positive voltage history. Further, the radical flux decreases with increasing positive voltage. It can be concluded that a higher positive voltage at a lower negative voltage condition is good to obtain better film properties and higher film thickness on the sidewall surface. Pattern transfer properties for the nanoimprint formed by

  14. Palladium/norbornene catalysis for selective aromatic functionalization via C-H activation

    OpenAIRE

    Fontana, Marco

    2015-01-01

    The subject of this PhD thesis is the study of new processes in homogeneous catalysis for the synthesis of selectively substituted compounds containing the biaryl unit. The methodology, discovered in our laboratory, utilizes simple and readily available starting materials to form complex molecular structures under mild conditions. It takes advantage of the catalytic system based on palladium and norbornene. The metal, the strained olefin and an aryl halide work in a cooperative way to build u...

  15. Iron catalyzed C-H activation and synthesis of novel ligands

    OpenAIRE

    Nakanishi, Masafumi

    2007-01-01

    Iron-catalyzed benzylic oxidations, nitrogen transfer reactions such as iminations of sulfides and sulfoxides, aziridinations of olefins and a-aminations of silyl enol ethers were developed. Also, the synthesis of novel nitrogen containing ligands such as 1,4,7-triazacyclononane (TACN) derivatives and dipyridylamine derivatives was undertaken.Iron-catalyzed benzylic oxidation was successfully performed by using a combination of iron(III) chloride (2 mol%) as a catalyst and tert-butyl hydroper...

  16. Effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement

    Science.gov (United States)

    Shin, Tae-Bong; Lee, Joo-Hee; Ahn, Kang-Min; Kim, Tae-Hyung

    2016-01-01

    PURPOSE To evaluate the effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement. MATERIALS AND METHODS The specimens were prepared to evaluate the bond strength of epoxy resin-based fiber posts (D.T. Light-Post) to dual-curing resin cement (RelyX U200). The specimens were divided into four groups (n=18) according to different surface treatments: group 1, no treatment; group 2, silanization; group 3, silanization after hydrogen peroxide etching; group 4, silanization with warm drying at 80℃ after hydrogen peroxide etching. After storage of the specimens in distilled water at 37℃ for 24 hours, the shear bond strength (in MPa) between the fiber post and resin cement was measured using a universal testing machine. The fractured surface of the fiber post was examined using scanning electron microscopy. Data were analyzed using one-way ANOVA and post-hoc analysis with Tukey's HSD test (α=0.05). RESULTS Silanization of the fiber post (Group 2) significantly increased the bond strength in comparison with the non treated control (Group 1) (P.05). CONCLUSION Fiber post silanization and subsequent heat treatment (80℃) with warm air blower can be beneficial in clinical post cementation. However, hydrogen peroxide etching prior to silanization was not effective in this study. PMID:27141252

  17. Molecular structure, Normal Coordinate Analysis, harmonic vibrational frequencies, Natural Bond Orbital, TD-DFT calculations and biological activity analysis of antioxidant drug 7-hydroxycoumarin

    Science.gov (United States)

    Sebastian, S.; Sylvestre, S.; Jayarajan, D.; Amalanathan, M.; Oudayakumar, K.; Gnanapoongothai, T.; Jayavarthanan, T.

    2013-01-01

    In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the σ* and π* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyperconjugation of hydrogen-bonded interaction. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra. Microbial activity of studied compounds was tested against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, Psuedomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Salmonella typhi and Enterococcus faecalis.

  18. Microstructural characterization of a diffusion-bonded joint for 9Cr-ODS and JLF-1 reduced activation ferritic/martensitic steels

    International Nuclear Information System (INIS)

    Bonding of oxide dispersion strengthened (ODS) steels to non-ODS reduced activation ferritic/martensitic (RAFM) steels is essential to their application to blanket systems. In the present study, a diffusion-bonded joint of the candidate 9Cr-ODS steel and JLF-1 RAFM steel was fabricated using hot isostatic pressing (HIP). The effect of post-bond heat treatments (PBHTs) was studied by hardness measurement and microstructural analysis. The results indicated that, after normalization and tempering (N and T), the hardness and microstructures of 9Cr-ODS and JLF-1 base metals recovered to levels similar to those before HIP. However, a soft region was observed across the bonding interfaces for all specimens containing the as-HIPed condition and those after PBHTs. This was due to coarser micro-carbides (M3C in as-HIPed condition and M23C6 in N and T conditions) near the interfaces than in the base metals for both 9Cr-ODS and JLF-1. Energy Dispersive X-ray Spectroscopy (EDS) analysis confirmed that carbon, tungsten, and chromium in the matrix near the interfaces are transferred to the micro-carbides, making them coarser there. Ti diffused from the 9Cr-ODS side to the JLF-1 side forming Ti-rich carbides after tempering, especially at high temperature to 1073 K

  19. Effect of copper-sulphur bond on the DNA photo-cleavage activity of 2-(methylthio)ethylpyridine-2-carbaldimine copper(II) complexes

    Indian Academy of Sciences (India)

    Tarkeshwar Gupta; Ashis K Patra; Shanta Dhar; Munirathinam Nethaji; Akhil R Chakravarty

    2005-03-01

    The binding and photo-induced DNA cleavage activity of a binary complex [CuL2](ClO4)2 (1) and the in situ generated ternary complexes [CuLB](ClO4)2 from 1 (B: 1,10-phenanthroline, phen, 2; dipyrido[3,2-: 2',3'-]quinoxaline, dpq, 3) are studied, where L is a N2S-donor tridentate Schiff base 2-(methylthio)ethylpyridine-2-carbaldimine. Complex 1, structurally characterized by X-ray diffraction study, has six-coordinate meridional geometry showing CuN4S2 coordination. The Cu-N bond lengths are in the range of 1.968(3) to 2.158(4) Å. The Cu-S bond lengths of 2.599(2) and 2.705(2) Å are significantly long indicating weak covalent interaction between copper and sulphur atoms. The thiomethyl groups are cis to each other giving S-Cu-S angle of 75.82(5)°. The Cu-N(pyridyl) bond distances are longer than the Cu-N(imine) bonds. The complexes are redox active and display a quasi-reversible cyclic voltammetric response assignable to the Cu(II)/Cu(I) couple near 0.0 V vs SCE in DMF-Tris buffer (1 : 4 /) using 0.1 M KCl as supporting electrolyte. Electronic spectra of the complexes show a - band in the range 630 to 700 nm in DMF along with higher energy charge transfer bands. While complex 1 is a poor binder to DNA, the ternary complexes show good DNA binding propensity. The photo-nuclease activity of 1-3 is studied using UV and visible wavelengths. The DNA cleavage activity at 365 nm follows the order: 3 > 2 > 1. The cleavage reaction involves the formation of singlet oxygen as the reactive species in a type-II process.

  20. The disulfide bond in the Aeromonas hydrophila lipase/acyltransferase stabilizes the structure but is not required for secretion or activity.

    OpenAIRE

    Brumlik, M J; van der Goot, F. G.; Wong, K R; Buckley, J T

    1997-01-01

    Vibrio and Aeromonas spp. secrete an unusual 35-kDa lipase that shares several properties with mammalian lecithin-cholesterol acyltransferase. The Aeromonas hydrophila lipase contains two cysteine residues that form an intramolecular disulfide bridge. Here we show that changing either of the cysteines to serine does not reduce enzymatic activity, indicating that the disulfide bond is not required for correct folding. However, when either of the cysteines is replaced, the enzyme is more readil...

  1. Studies on pharmacological activation of human serum immunoglobulin G by chemical modification and active subfragments. IV. Induction of anti-inflammatory activity by chemical cleavage of interchain disulfide bonds in human immunoglobulin G and pharmacological activity of alkylated subfragments.

    Science.gov (United States)

    Mimura, T; Tsujikawa, K; Nakajima, H; Okabe, M; Kohama, Y; Iwai, M; Yokoyama, K

    1986-01-01

    Commercially available human serum immunoglobulin G (IgG, native IgG) was separated into two fractions (Fr.I and II) using a diethylaminoethyl cellulose column. Heavy and light chains containing fractions were obtained from these two fractions after carboxamide-methylation. Thus, these fractions were subjected to an anti-inflammatory screening procedure and were shown to have a potent inhibitory activity against rat carrageenin induced paw edema, while no effect was observed in native IgG, Fr.I or II. The reduction and alkylation of the interchain disulfide bonds were essential to induce the anti-inflammatory activity. The anti-inflammatory activity of alkylated heavy and light chains of Fr.I (Fr.I-H and I-L) was also noted in subacute inflammation caused by the felt pellet and croton oil granuloma methods. Moreover, strong membrane stabilizing activities of Fr.I-H and I-L were demonstrated in vitro using rat red blood cell membrane and liver lysosomal membrane. PMID:3712209

  2. Anisotropic surface properties of micro/nanostructured a-C:H:F thin films with self-assembly applications

    OpenAIRE

    Freire Soler, Víctor Manuel; Corbella Roca, Carles; Bertrán Serra, Enric; Portal-Marco, S.; Rubio-Roy, M.; Andújar Bella, José Luis

    2012-01-01

    The singular properties of hydrogenated amorphous carbon (a-C:H) thin filmsdeposited by pulsed DC plasma enhanced chemical vapor deposition (PECVD), such as hardness and wear resistance, make it suitable as protective coating with low surface energy for self-assembly applications. In this paper, we designed fluorine-containing a-C:H (a-C:H:F) nanostructured surfaces and we characterized them for self-assembly applications. Sub-micron patterns were generated on silicon through laser lithograph...

  3. Platinum containing amorphous hydrogenated carbon (a-C:H/Pt) thin films as selective solar absorbers

    International Nuclear Information System (INIS)

    We have investigated a double-cermet structured thin film in which an a-C:H thin film was used as an anti-reflective (AR) layer and two platinum-containing amorphous hydrogenated carbon (a-C:H/Pt) thin films were used as the double cermet layers. A reactive co-sputter deposition method was used to prepare both the anti-reflective and cermet layers. Effects of the target power and heat treatment were studied. The obtained films were characterized using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy. The optical absorptance and emittance of the as deposited and annealed films were determined using UV–vis-NIR spectroscopy. We show that the optical absorptance of the resulting double-cermet structured thin film is as high as 96% and remains to be 91% after heat treatment at 400 °C, indicating the thermal stability of the film

  4. Top Quark Flavor Changing Decay t → cH0 in Little Higgs Model

    Institute of Scientific and Technical Information of China (English)

    Farshid Tabbakh; LIU Jing-Jing; MA Wen-Gan; ZHANG Ren-You; HOU Hong-Sheng

    2005-01-01

    We study theoretically the quantum effects of the littlest Higgs model (LH) mediated by flavor changing one-loop Feynman diagrams on the rare decay process t → cH0. The comparison of the decay width in the LH model with that in the standard model (SM) is made. We find that the decay branch ratio of t → cH0 in the LH model is at most of the order ~ 10-12, which is two order larger than in the SM. The numerical results show that the difference between the branch ratios in the LH model and the SM is generally sensitive to the LH model parameters, such as symmetry breaking scale f, Higgs boson mass mH0, and x = v'4f /v2 in our chosen parameter space, but relatively insensitive to the value choice of the cosine of the mixing angle c and the ratio λ1/λ2.

  5. Platinum containing amorphous hydrogenated carbon (a-C:H/Pt) thin films as selective solar absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Yung-Hsiang; Brahma, Sanjaya [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Tzeng, Y.H. [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Ting, Jyh-Ming, E-mail: jting@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan (China)

    2014-10-15

    We have investigated a double-cermet structured thin film in which an a-C:H thin film was used as an anti-reflective (AR) layer and two platinum-containing amorphous hydrogenated carbon (a-C:H/Pt) thin films were used as the double cermet layers. A reactive co-sputter deposition method was used to prepare both the anti-reflective and cermet layers. Effects of the target power and heat treatment were studied. The obtained films were characterized using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy. The optical absorptance and emittance of the as deposited and annealed films were determined using UV–vis-NIR spectroscopy. We show that the optical absorptance of the resulting double-cermet structured thin film is as high as 96% and remains to be 91% after heat treatment at 400 °C, indicating the thermal stability of the film.

  6. Conserved water-mediated hydrogen bond network between TM-I, -II, -VI, and -VII in 7TM receptor activation

    DEFF Research Database (Denmark)

    Nygaard, Rie; Hansen, Louise Valentin; Mokrosinski, Jacek;

    2010-01-01

    simulations showed that, although the fewer water molecules in rhodopsin were relatively movable, the hydrogen bond network of the beta2-adrenergic receptor was fully loaded with water molecules that were surprisingly immobilized between the two rotamer switches, both apparently being in their closed...

  7. Comparison of insect kinin analogs with cis-peptide bond motif 4-aminopyroglutamate identifies optimal stereochemistry for diuretic activity.

    Science.gov (United States)

    The insect kinins are present in a wide variety of insects and function as potent diuretic peptides, though they are subject to rapid degradation by internal peptidases. Insect kinin analogs incorporating stereochemical variants of (2S,4S)-4-aminopyroglutamate (APy), a cis-peptide bond motif, demon...

  8. Foster Mother-Infant Bonding: Associations between Foster Mothers' Oxytocin Production, Electrophysiological Brain Activity, Feelings of Commitment, and Caregiving Quality

    Science.gov (United States)

    Bick, Johanna; Dozier, Mary; Bernard, Kristin; Grasso, Damion; Simons, Robert

    2013-01-01

    This study examined the biological processes associated with foster mother-infant bonding. In an examination of foster mother-infant dyads ("N" = 41, mean infant age = 8.5 months), foster mothers' oxytocin production was associated with their expressions of behavioral delight toward their foster infant and their average P3 response to images of…

  9. Deposition of a-C:H films on UHMWPE substrate and its wear-resistance

    Science.gov (United States)

    Xie, Dong; Liu, Hengjun; Deng, Xingrui; Leng, Y. X.; Huang, Nan

    2009-10-01

    In prosthetic hip replacements, ultrahigh molecular weight polyethylene (UHMWPE) wear debris is identified as the main factor limiting the lifetime of the artificial joints. Especially UHMWPE debris from the joint can induce tissue reactions and bone resorption that may lead to the joint loosening. The diamond like carbon (DLC) film has attracted a great deal of interest in recent years mainly because of its excellent tribological property, biocompatibility and chemically inert property. In order to improve the wear-resistance of UHMWPE, a-C:H films were deposited on UHMWPE substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-PECVD) technology. During deposition, the working gases were argon and acetylene, the microwave power was set to 800 W, the biased pulsed voltage was set to -200 V (frequency 15 kHz, duty ratio 20%), the pressure in vacuum chamber was set to 0.5 Pa, and the process time was 60 min. The films were analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, anti-scratch and wear test. The results showed that a typical amorphous hydrogenated carbon (a-C:H) film was successfully deposited on UHMWPE with thickness up to 2 μm. The nano-hardness of the UHMWPE coated with a-C:H films, measured at an applied load of 200 μN, was increased from 10 MPa (untreated UHMWPE) to 139 MPa. The wear test was carried out using a ball (Ø 6 mm, SiC) on disk tribometer with an applied load of 1 N for 10000 cycles, and the results showed a reduction of worn cross-sectional area from 193 μm 2 of untreated UHMWPE to 26 μm 2 of DLC coated sample. In addition the influence of argon/acetylene gas flow ratio on the growth of a-C:H films was studied.

  10. Deposition of a-C:H films on UHMWPE substrate and its wear-resistance

    Energy Technology Data Exchange (ETDEWEB)

    Xie Dong [Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031 (China); Liu Hengjun; Deng Xingrui [Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Leng, Y.X., E-mail: yxleng@263.net [Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Huang Nan [Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

    2009-10-15

    In prosthetic hip replacements, ultrahigh molecular weight polyethylene (UHMWPE) wear debris is identified as the main factor limiting the lifetime of the artificial joints. Especially UHMWPE debris from the joint can induce tissue reactions and bone resorption that may lead to the joint loosening. The diamond like carbon (DLC) film has attracted a great deal of interest in recent years mainly because of its excellent tribological property, biocompatibility and chemically inert property. In order to improve the wear-resistance of UHMWPE, a-C:H films were deposited on UHMWPE substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-PECVD) technology. During deposition, the working gases were argon and acetylene, the microwave power was set to 800 W, the biased pulsed voltage was set to -200 V (frequency 15 kHz, duty ratio 20%), the pressure in vacuum chamber was set to 0.5 Pa, and the process time was 60 min. The films were analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, anti-scratch and wear test. The results showed that a typical amorphous hydrogenated carbon (a-C:H) film was successfully deposited on UHMWPE with thickness up to 2 {mu}m. The nano-hardness of the UHMWPE coated with a-C:H films, measured at an applied load of 200 {mu}N, was increased from 10 MPa (untreated UHMWPE) to 139 MPa. The wear test was carried out using a ball (O 6 mm, SiC) on disk tribometer with an applied load of 1 N for 10000 cycles, and the results showed a reduction of worn cross-sectional area from 193 {mu}m{sup 2} of untreated UHMWPE to 26 {mu}m{sup 2} of DLC coated sample. In addition the influence of argon/acetylene gas flow ratio on the growth of a-C:H films was studied.

  11. Deposition of a-C:H films on UHMWPE substrate and its wear-resistance

    International Nuclear Information System (INIS)

    In prosthetic hip replacements, ultrahigh molecular weight polyethylene (UHMWPE) wear debris is identified as the main factor limiting the lifetime of the artificial joints. Especially UHMWPE debris from the joint can induce tissue reactions and bone resorption that may lead to the joint loosening. The diamond like carbon (DLC) film has attracted a great deal of interest in recent years mainly because of its excellent tribological property, biocompatibility and chemically inert property. In order to improve the wear-resistance of UHMWPE, a-C:H films were deposited on UHMWPE substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-PECVD) technology. During deposition, the working gases were argon and acetylene, the microwave power was set to 800 W, the biased pulsed voltage was set to -200 V (frequency 15 kHz, duty ratio 20%), the pressure in vacuum chamber was set to 0.5 Pa, and the process time was 60 min. The films were analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, anti-scratch and wear test. The results showed that a typical amorphous hydrogenated carbon (a-C:H) film was successfully deposited on UHMWPE with thickness up to 2 μm. The nano-hardness of the UHMWPE coated with a-C:H films, measured at an applied load of 200 μN, was increased from 10 MPa (untreated UHMWPE) to 139 MPa. The wear test was carried out using a ball (O 6 mm, SiC) on disk tribometer with an applied load of 1 N for 10000 cycles, and the results showed a reduction of worn cross-sectional area from 193 μm2 of untreated UHMWPE to 26 μm2 of DLC coated sample. In addition the influence of argon/acetylene gas flow ratio on the growth of a-C:H films was studied.

  12. Dichotomy in regioselectivity of Pd-catalyzed direct C-H arylation of protected uracils

    Czech Academy of Sciences Publication Activity Database

    Čerňová, Miroslava; Hocek, Michal

    Praha : Institute of Organic Chemistry and Biochemistry AS CR, v. v. i., 2011 - (Hocek, M.), s. 314-316 ISBN 978-80-86241-37-1. - (Collection Symposium Series. 12). [ Chemistry of Nucleic Acid Components /15./. Český Krumlov (CZ), 05.06.2011-10.06.2011] R&D Projects: GA MŠk(CZ) LC06077 Institutional research plan: CEZ:AV0Z40550506 Keywords : direct C-H arylation * uracils * pyrimidines * palladium Subject RIV: CC - Organic Chemistry

  13. Overcoming the "oxidant problem": strategies to use O2 as the oxidant in organometallic C-H oxidation reactions catalyzed by Pd (and Cu).

    Science.gov (United States)

    Campbell, Alison N; Stahl, Shannon S

    2012-06-19

    Oxidation reactions are key transformations in organic chemistry because they can increase chemical complexity and incorporate heteroatom substituents into carbon-based molecules. This principle is manifested in the conversion of petrochemical feedstocks into commodity chemicals and in the synthesis of fine chemicals, pharmaceuticals, and other complex organic molecules. The utility and function of these molecules correlate directly with the presence and specific placement of oxygen and nitrogen heteroatoms and other functional groups within the molecules. Methods for selective oxidation of C-H bonds have expanded significantly over the past decade, and their role in the synthesis of organic chemicals will continue to increase. Our group's contributions to this field are linked to our broader interest in the development and mechanistic understanding of aerobic oxidation reactions. Molecular oxygen (O(2)) is the ideal oxidant. Its low cost and lack of toxic byproducts make it a highly appealing reagent that can address key "green chemistry" priorities in industry. With strong economic and environmental incentives to use O(2), the commmodity chemicals industry often uses aerobic oxidation reactions. In contrast, O(2) is seldom used to prepare more-complex smaller-volume chemicals, a limitation that reflects, in part, the limited synthetic scope and utility of existing aerobic reactions. Pd-catalyzed reactions represent some of the most versatile methods for selective C-H oxidation, but they often require stoichiometric transition-metal or organic oxidants, such as Cu(II), Ag(I), or benzoquinone. This Account describes recent strategies that we have identified to use O(2) as the oxidant in these reactions. In Pd-catalyzed C-H oxidation reactions that form carbon-heteroatom bonds, the stoichiometric oxidant is often needed to promote difficult reductive elimination steps in the catalytic mechanism. To address this challenge, we have identified new ancillary ligands for

  14. Cross-dehydrogenative coupling for the intermolecular C-O bond formation.

    Science.gov (United States)

    Krylov, Igor B; Vil', Vera A; Terent'ev, Alexander O

    2015-01-01

    The present review summarizes primary publications on the cross-dehydrogenative C-O coupling, with special emphasis on the studies published after 2000. The starting compound, which donates a carbon atom for the formation of a new C-O bond, is called the CH-reagent or the C-reagent, and the compound, an oxygen atom of which is involved in the new bond, is called the OH-reagent or the O-reagent. Alcohols and carboxylic acids are most commonly used as O-reagents; hydroxylamine derivatives, hydroperoxides, and sulfonic acids are employed less often. The cross-dehydrogenative C-O coupling reactions are carried out using different C-reagents, such as compounds containing directing functional groups (amide, heteroaromatic, oxime, and so on) and compounds with activated C-H bonds (aldehydes, alcohols, ketones, ethers, amines, amides, compounds containing the benzyl, allyl, or propargyl moiety). An analysis of the published data showed that the principles at the basis of a particular cross-dehydrogenative C-O coupling reaction are dictated mainly by the nature of the C-reagent. Hence, in the present review the data are classified according to the structures of C-reagents, and, in the second place, according to the type of oxidative systems. Besides the typical cross-dehydrogenative coupling reactions of CH- and OH-reagents, closely related C-H activation processes involving intermolecular C-O bond formation are discussed: acyloxylation reactions with ArI(O2CR)2 reagents and generation of O-reagents in situ from C-reagents (methylarenes, aldehydes, etc.). PMID:25670997

  15. Palladium-catalysed norbornene-mediated C-H functionalization of arenes

    Science.gov (United States)

    Ye, Juntao; Lautens, Mark

    2015-11-01

    The Catellani reaction -- a palladium-catalysed C-H functionalization reaction mediated by norbornene -- was first reported in 1997. The capacity to functionalize both the ortho and ipso positions of aryl halides in a single transformation held great appeal. We reported an annulative Catellani reaction in 2000. Since then, our two groups have explored the synthetic utility of this reaction and dramatic progress has been made by a number of groups in the past five years. Whereas the original Catellani reaction uses Pd(0) catalysts, recent studies have shown that Pd(II) catalysts can be used in combination with norbornene to effect (1) direct 2-alkylation of indoles and pyrroles and (2) selective meta-C-H functionalization of arenes bearing commonly used ortho-directing groups, thereby opening new avenues for future research. We describe the most recent developments concerning the Pd-catalysed norbornene-mediated C-H functionalization of arenes, including applications in natural products synthesis. We outline challenges and future opportunities.

  16. Thermal shock and thermal cycling behaviour of amorphous a-C:H films on molybdenum substrates

    International Nuclear Information System (INIS)

    The thermal behaviour of a-C:H films (a stands for amorphous) deposited by the TEXTOR carbonization technique on molybdenum substrates was investigated in high power electron beam testing device for single and multiple shot sequences. The stationary thermal behaviour was also measured. The results for single shot testing are presented in a threshold damage diagram and show that the stability of a-C:H films on molybdenum is superior to that on steel. At higher or repeated loadings the films are converted gradually to molybdenum carbide. AES and SIMS depth profiling was used to investigate the concentration profiles and interface compositions of the films after various heat treatments. Their 1-h thermal stability on molybdenum extends to approximately 700 degree C in a stationary test. Results show that a-C:H films on molybdenum should be effective in shielding the molybdenum substrate from the plasma in a fusion device as long as the stated loading limits are not exceeded. (author)

  17. Transition Metal Catalyzed Hydroarylation of Multiple Bonds: Exploration of Second Generation Ruthenium Catalysts and Extension to Copper Systems

    Energy Technology Data Exchange (ETDEWEB)

    T. Brent Gunnoe

    2011-02-17

    Catalysts provide foundational technology for the development of new materials and can enhance the efficiency of routes to known materials. New catalyst technologies offer the possibility of reducing energy and raw material consumption as well as enabling chemical processes with a lower environmental impact. The rising demand and expense of fossil resources has strained national and global economies and has increased the importance of accessing more efficient catalytic processes for the conversion of hydrocarbons to useful products. The goals of the research are to develop and understand single-site homogeneous catalysts for the conversion of readily available hydrocarbons into useful materials. A detailed understanding of these catalytic reactions could lead to the development of catalysts with improved activity, longevity and selectivity. Such transformations could reduce the environmental impact of hydrocarbon functionalization, conserve energy and valuable fossil resources and provide new technologies for the production of liquid fuels. This project is a collaborative effort that incorporates both experimental and computational studies to understand the details of transition metal catalyzed C-H activation and C-C bond forming reactions with olefins. Accomplishments of the current funding period include: (1) We have completed and published studies of C-H activation and catalytic olefin hydroarylation by TpRu{l_brace}P(pyr){sub 3}{r_brace}(NCMe)R (pyr = N-pyrrolyl) complexes. While these systems efficiently initiate stoichiometric benzene C-H activation, catalytic olefin hydroarylation is hindered by inhibition of olefin coordination, which is a result of the steric bulk of the P(pyr){sub 3} ligand. (2) We have extended our studies of catalytic olefin hydroarylation by TpRu(L)(NCMe)Ph systems to L = P(OCH{sub 2}){sub 3}CEt. Thus, we have now completed detailed mechanistic studies of four systems with L = CO, PMe{sub 3}, P(pyr){sub 3} and P(OCH{sub 2}){sub 3}CEt

  18. Direct C-H arylation of purines: Development of methodology and its use in regioselective synthesis of 2,6,8-trisubstituted purines

    Czech Academy of Sciences Publication Activity Database

    Čerňa, Igor; Pohl, Radek; Klepetářová, Blanka; Hocek, Michal

    2006-01-01

    Roč. 8, č. 23 (2006), s. 5389-5392. ISSN 1523-7060 R&D Projects: GA ČR(CZ) GA203/05/0043; GA MŠk(CZ) LC06077 Institutional research plan: CEZ:AV0Z40550506 Keywords : purines * cross-coupling * C-H activation * arylation Subject RIV: CC - Organic Chemistry Impact factor: 4.659, year: 2006

  19. Mezzanine finance and corporate bonds

    OpenAIRE

    Libena TETREVOVA

    2009-01-01

    The article deals with the problems of mezzanine finance in relation to corporate bonds. Firstly, attention is paid to definition of mezzanine finance. The term mezzanine finance is used as a term for hybrid forms of financing that combine elements of debt and equity financing. Mezzanine finance represents an alternative form of financing corporate activities. Secondly, possible forms of mezzanine finance are characterized. We can say that special types of corporate bonds (convertible bonds a...

  20. Metal-catalyzed activation of ethers via C-O bond cleavage: a new strategy for molecular diversity.

    Science.gov (United States)

    Cornella, Josep; Zarate, Cayetana; Martin, Ruben

    2014-12-01

    In 1979, the seminal work of Wenkert set the standards for the utilization of aryl and vinyl ethers as coupling partners via C-O bond-cleavage. Although the topic remained dormant for almost three decades, the last few years have witnessed a renaissance in this area of expertise, experiencing an exponential growth and becoming a significant discipline within the cross-coupling arena. The means to utilize readily accessible aryl or vinyl ethers as counterparts does not only represent a practical, powerful and straightforward alternative to organic halides, but also constitutes an excellent opportunity to improve our chemical knowledge about a relatively unexplored area of expertise. This review summarizes the most significant developments in the area of C-O bond-cleavage when employing aryl or vinyl ethers, providing a detailed overview of the current state of the art and including future aspects, when applicable. PMID:25157613

  1. Isomerization of Olefins Triggered by Rhodium-Catalyzed C–H Bond Activation: Control of Endocyclic β-Hydrogen Elimination**

    OpenAIRE

    Yip, Stephanie Y Y; Aïssa, Christophe

    2015-01-01

    Five-membered metallacycles are typically reluctant to undergo endocyclic β-hydrogen elimination. The rhodium-catalyzed isomerization of 4-pentenals into 3-pentenals occurs through this elementary step and cleavage of two C–H bonds, as supported by deuterium-labeling studies. The reaction proceeds without decarbonylation, leads to trans olefins exclusively, and tolerates other olefins normally prone to isomerization. Endocyclic β-hydrogen elimination can also be controlled in an enantiodiverg...

  2. Shear bond strength of glass-ionomer cements to dentin: Effects of dentin depth and type of material activation

    OpenAIRE

    Elda PISANESCHI; Rubens Corte Real de CARVALHO; Edmir MATSON

    1997-01-01

    The purpose of this study was to determine, through the shear bond strength of in vitro tests, that the type of glass-ionomer cements (conventional or hybrid) and dentin depth (superficial or deep) are factors that may influence the adhesion of these materials to the dentin structure. Specimens of two conventional glass-ionomer cements (Vidrion Rregistered - SS White and Chelon Filregistered- Espe) and a hybrid-glass ionomer cement (Vitremerregistered - 3M) were separated in groups and prepar...

  3. Microstructure characterization of advanced protective Cr/CrN+a-C:H/a-C:H:Cr multilayer coatings on carbon fibre composite (CFC).

    Science.gov (United States)

    Major, L; Janusz, M; Lackner, J M; Kot, M; Major, B

    2016-06-01

    Studies of advanced protective chromium-based coatings on the carbon fibre composite (CFC) were performed. Multidisciplinary examinations were carried out comprising: microstructure transmission electron microscopy (TEM, HREM) studies, micromechanical analysis and wear resistance. Coatings were prepared using a magnetron sputtering technique with application of high-purity chromium and carbon (graphite) targets deposited on the CFC substrate. Selection of the CFC for surface modification in respect to irregularities on the surface making the CFC surface more smooth was performed. Deposited coatings consisted of two parts. The inner part was responsible for the residual stress compensation and cracking initiation as well as resistance at elevated temperatures occurring namely during surgical tools sterilization process. The outer part was responsible for wear resistance properties and biocompatibility. Experimental studies revealed that irregularities on the substrate surface had a negative influence on the crystallites growth direction. Chromium implanted into the a-C:H structure reacted with carbon forming the cubic nanocrystal chromium carbides of the Cr23 C6 type. The cracking was initiated at the coating/substrate interface and the energy of brittle cracking was reduced because of the plastic deformation at each Cr interlayer interface. The wear mechanism and cracking process was described in micro- and nanoscale by means of transmission electron microscope studies. Examined materials of coated CFC type would find applications in advanced surgical tools. PMID:26788794

  4. Diffusion bonding

    Science.gov (United States)

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  5. Reaction Pathways and Energetics of Etheric C–O Bond Cleavage Catalyzed by Lanthanide Triflates

    Energy Technology Data Exchange (ETDEWEB)

    Assary, Rajeev S.; Atesin, Abdurrahman C.; Li, Zhi; Curtiss, Larry A.; Marks, Tobin J.

    2013-09-06

    Efficient and selective cleavage of etheric C-O bonds is crucial for converting biomass into platform chemicals and liquid transportation fuels. In this contribution, computational methods at the DFT B3LYP level of theory are employed to understand the efficacy of lanthanide triflate catalysts (Ln(OTf)3, Ln = La, Ce, Sm, Gd, Yb, and Lu) in cleaving etheric C-O bonds. In agreement with experiment, the calculations indicate that the reaction pathway for C-O cleavage occurs via a C-H → O-H proton transfer in concert with weakening of the C-O bond of the coordinated ether substrate to ultimately yield a coordinated alkenol. The activation energy for this process falls as the lanthanide ionic radius decreases, reflecting enhanced metal ion electrophilicity. Details of the reaction mechanism for Yb(OTf)3-catalyzed ring opening are explored in depth, and for 1-methyl-d3-butyl phenyl ether, the computed primary kinetic isotope effect of 2.4 is in excellent agreement with experiment (2.7), confirming that etheric ring-opening pathway involves proton transfer from the methyl group alpha to the etheric oxygen atom, which is activated by the electrophilic lanthanide ion. Calculations of the catalytic pathway using eight different ether substrates indicate that the more rapid cleavage of acyclic versus cyclic ethers is largely due to entropic effects, with the former C-O bond scission processes increasing the degrees of freedom/particles as the transition state is approached.

  6. The conserved His8 of the Moloney murine leukemia virus Env SU subunit directs the activity of the SU-TM disulphide bond isomerase

    International Nuclear Information System (INIS)

    Murine leukemia virus (MLV) fusion is controlled by isomerization of the disulphide bond between the receptor-binding surface (SU) and fusion-active transmembrane subunits of the Env-complex. The bond is in SU linked to a CXXC motif. This carries a free thiol that upon receptor binding can be activated (ionized) to attack the disulphide and rearrange it into a disulphide isomer within the motif. To find out whether His8 in the conserved SPHQ sequence of Env directs thiol activation, we analyzed its ionization in MLV vectors with wtEnv and Env with His8 deleted or substituted for Tyr or Arg, which partially or completely arrests fusion. The ionization was monitored by following the pH effect on isomerization in vitro by Ca2+ depletion or in vivo by receptor binding. We found that wtEnv isomerized optimally at slightly basic pH whereas the partially active mutant required higher and the inactive mutants still higher pH. This suggests that His8 directs the ionization of the CXXC thiol

  7. Mechanistic Insight into the Intramolecular Benzylic C-H Nitrene Insertion Catalyzed by Bimetallic Paddlewheel Complexes: Influence of the Metal Centers.

    Science.gov (United States)

    Zhang, Xuepeng; Xu, Huiying; Liu, Xueping; Phillips, David Lee; Zhao, Cunyuan

    2016-05-17

    The intramolecular benzylic C-H amination catalyzed by bimetallic paddlewheel complexes was investigated by using density functional theory calculations. The metal-metal bonding characters were investigated and the structures featuring either a small HOMO-LUMO gap or a compact SOMO energy scope were estimated to facilitate an easier one-electron oxidation of the bimetallic center. The hydrogen-abstraction step was found to occur through three manners, that is, hydride transfer, hydrogen migration, and proton transfer. The imido N species are more preferred in the Ru-Ru and Pd-Mn cases whereas coexisting N species, namely, singlet/triplet nitrene and imido, were observed in the Rh-Rh and Pd-Co cases. On the other hand, the triplet nitrene N species were found to be predominant in the Pd-Ni and Pd-Zn systems. A concerted asynchronous mechanism was found to be modestly favorable in the Rh-Rh-catalyzed reactions whereas the Pd-Co-catalyzed reactions demonstrated a slight preference for a stepwise pathway. Favored stepwise pathways were seen in each Ru-Ru- and Pd-Mn-catalyzed reactions and in the triplet nitrene involved Pd-Ni and Pd-Zn reactions. The calculations suggest the feasibility of the Pd-Mn, Pd-Co, and Pd-Ni paddlewheel complexes as being economical alternatives for the expensive dirhodium/diruthenium complexes in C-H amination catalysis. PMID:27061588

  8. Additional disulfide bonds in insulin

    DEFF Research Database (Denmark)

    Vinther, Tine N; Pettersson, Ingrid; Huus, Kasper;

    2015-01-01

    -chain is flexible and can adapt multiple conformations. We examined how well disulfide bond predictions algorithms could identify disulfide bonds in this region of insulin. In order to identify stable insulin analogues with additional disulfide bonds, which could be expressed, the Cβ cut-off distance had...... higher yields in comparison to analogues with additional disulfide bonds that were more difficult to predict. In contrast, addition of the fourth disulfide bond rendered all analogues resistant to fibrillation under stress conditions and all stable analogues bound to the insulin receptor with picomolar...... predicts four additional four disulfide insulin analogues which could be expressed. Although the location of the additional disulfide bonds is only slightly shifted, this shift impacts both stability and activity of the resulting insulin analogues....

  9. Effect of the charge localization in the C+-H+ fragmentation pathway of the ethyne dication

    International Nuclear Information System (INIS)

    The C+-H+ channel in the fragmentation of the ethyne dication following inner-shell ionization has been studied by Auger electron-ion-ion coincidence spectroscopy. The ion-ion coincidence map shows a peculiar feature which corresponds to the emission of both the H+ and C+ ions in the same direction. The analysis of the data, complemented by ab initio calculations, suggests an interpretation in terms of a two-step, asynchronous concerted reaction, in which the charge of the ethynyl intermediate ion localizes on the terminal carbon atom.

  10. Kinetics of Hydrocarbon formation in a- C:H Film deposition plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Cal, E. de la; Tabares, F. L.

    1993-07-01

    The formation of C2 and Cp hydrocarbons during the PACVD of a-C:H films from admixtures of methane with H2 and He has been investigated by mass spectrometry under several deposition condition. The time evolution of the observed species indicates that the formation mechanisms of ethylene and acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene formation was found to be directly related to the formation of the film on top of the carburized metal. (Author) 12 refs.

  11. Production of iron carbide using the metastable Fe-C-H-O system

    Energy Technology Data Exchange (ETDEWEB)

    Conejo, A.N.; Estrada, R.S.; Rodriguez, R.A. [Instituto Tecnologico Morelia (Mexico)

    2003-04-01

    The production of iron carbide without the formation of free carbon was explored using a metastable thermodynamic approach. Phase stability diagrams, at constant pressure and constant temperature, indicating the phase fields for the condensed phases in total equilibrium with a reactant gas phase were employed as the initial point analysis of the present study. With the aid of this information it was possible to identify the phase fields corresponding to metastable iron carbide in a ternary diagram (C-H-O). Experimental evidence confirms the validity of this information. The metastable diagrams are proposed to be used as a method to control the production of iron carbide in the industrial practice. (orig.)

  12. Kinetics of Hydrocarbon formation in a-C:H film deposition plasmas

    International Nuclear Information System (INIS)

    The formation of C2 and C3 hydrocarbons during the PACVD of a-C-H films from admixtures of methane with H2 and He has been investigated by mass spectrometry under several deposition condition. The time evolution of the observed species indicates that the formation mechanism of ethylene and acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene are sensitive to the conditions of the wall during the growing of the carburized metal. (Author)

  13. Formal Gold- and Rhodium-Catalyzed Regiodivergent C-H Alkynylation of 2-Pyridones.

    Science.gov (United States)

    Li, Yunyun; Xie, Fang; Li, Xingwei

    2016-01-15

    Formal regiodivergent C-H alkynylation of 2-pyridones bearing different N-substituents has been realized under Au(I) and Rh(III) catalysis using a hypervalent iodine alkyne reagent. When catalyzed by Au(I), the alkynylation occurred at the most electron-rich 5-position via an electrophilic alkynylation pathway. The selectivity was switched to the 6-position under assistance of an N-chelation group when a Rh(III) catalyst was employed. A rhodacylic complex has been isolated as a key intermediate. PMID:26709449

  14. Compositional, structural and optical properties of Si-rich a-SiC:H thin films deposited by ArF-LCVD

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, E. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain)]. E-mail: fani@uvigo.es; Chiussi, S. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Kosch, U. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Gonzalez, P. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Serra, J. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Serra, C. [CACTI, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Leon, B. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain)

    2005-07-30

    Silicon-rich amorphous hydrogenated silicon carbon (a-SiC:H) films with C content up to 23% have been grown on Si and Corning glass substrates using ArF laser induced chemical vapor deposition (ArF-LCVD). This technique allows tailoring film composition by controlling deposition parameters such as precursor gas mixture (disilane and ethylene diluted in helium) and substrate temperature (180-400 deg. C). The influence of both parameters on composition and bonding were studied by Fourier transform infrarred (FTIR) and X-Ray photoelectron spectroscopy (XPS). The optical gap of these semiconductors deposited at 250 deg. C varied from 1.6 to 2.4 eV and was determined by UV-vis spectroscopy. An additional analysis by profilometry and atomic force microscopy (AFM) have been done for determining the deposition rate and the roughness (rms < 6 nm) of the films as well as their surface morphology.

  15. Pi Bond Orders and Bond Lengths

    Science.gov (United States)

    Herndon, William C.; Parkanyi, Cyril

    1976-01-01

    Discusses three methods of correlating bond orders and bond lengths in unsaturated hydrocarbons: the Pauling theory, the Huckel molecular orbital technique, and self-consistent-field techniques. (MLH)

  16. New Insights into Mechanism of Molybdenum(VI)-Dioxo Complex Catalyzed Hydrosilylation of Carbonyls: An Alternative Model for Activating Si-H Bond.

    Science.gov (United States)

    Ning, Xiaoshuang; Wang, Jiandi; Wei, Haiyan

    2016-06-23

    Recently, a series of oxo/nitrido-Re(V)/Mo(VI)/Ru(VI)/Mn(V) complexes were demonstrated to be efficient catalysts in activating silanes and catalyzing hydrosilylations of unsaturated organic substrates. In the present study, the high-valent molybdenum(VI)-dioxo complex MoO2Cl2 catalyzed hydrosilylations of carbonyls was reinvestigated using density functional theory method. Previous experimental and theoretical investigations suggested a [2 + 2] addition pathway for MoO2Cl2 catalyzed hydrosilylations of ketones. In the present study, we propose an ionic outer-sphere mechanistic pathway to be the most favorable pathway. The key step in the ionic outer-sphere pathway is oxygen atom of C═O bonds nucleophilically attacking the silicon atom in an η(1)-silane molybdenum adduct. The Si-H bond is then cleaved heterolytically. This process features a novel SN2@Si transition state, which then generates a loosely bound ion pair: anionic molybdenum hydride paired with silylcarbenium ion ([MoO2Cl2H](-) [SiR3(OCR'R″)](+)) in solvent. The last step is silylcarbenium ion abstracting the hydride on molybdenum hydride to yield silyl ether. The calculated activation free energy barrier of the rate-determing step was 24.1 kcal/mol for diphenylketone (PhC═OPh) and silane of PhMe2SiH. Furthermore, the ionic outer-sphere pathway is calculated to be ∼10.0 kcal/mol lower than the previously proposed [2 + 2] addition pathway for a variety of silanes and aldehyde/ketone substrates. This preference arises from stronger electrophilicity of the high-valent molybdenum(VI) metal center toward a hydride. Here, we emphasize MoO2Cl2 behaves similar to Lewis acidic trispentafluorophenyl borane B(C6F5)3 in activating Si-H bond. PMID:27243271

  17. Ion beam analysis of a-C:H films on alloy steel substrate

    International Nuclear Information System (INIS)

    An a-C:H thin film deposited by plasma immersion ion implantation and deposition on alloy steel (16MnCr5) was analyzed using a self-consistent ion beam analysis technique. In the self-consistent analysis, the results of each individual technique are combined in a unique model, increasing confidence and reducing simulation errors. Self-consistent analysis, then, is able to improve the regular ion beam analysis since several analyses commonly used to process ion beam data still rely on handling each spectrum independently. The sample was analyzed by particle-induced x-ray emission (for trace elements), elastic backscattering spectrometry (for carbon), forward recoil spectrometry (for hydrogen) and Rutherford backscattering spectrometry (for film morphology). The self-consistent analysis provided reliable chemical information about the film, despite its “heavy” substrate. As a result, we could determine precisely the H/C ratio, contaminant concentration and some morphological characteristics of the film, such as roughness and discontinuities. - Highlights: • Self-consistent approach of ion beam analysis was used to characterize an a-C:H film. • The self-consistent analysis provided a unequivocal and reliable model of the sample. • Morphological aspects of the film were assessed with the ion beam analysis

  18. The role of C-H$\\ldots$ interaction in the stabilization of benzene and adamantane clusters

    Indian Academy of Sciences (India)

    R Mahesh Kumar; M Elango; R Parthasarathi; Dolly Vijay; V Subramanian

    2012-01-01

    In this investigation, a systematic attempt has been made to understand the interaction between adamantane and benzene using both ab initio and density functional theory methods. C-H$\\ldots$ type of interaction between C-H groups of adamantane and cloud of benzene is found as the important attraction for complex formation. The study also reveals that the methylene (-CH2) and methine (-CH) groups of adamantane interact with benzene resulting in different geometrical structures. And it is found that the former complex is stronger than the later. The diamondoid structure of adamantane enables it to interact with a maximum of four benzene molecules, each one along the four faces. The stability of the complex increases with increase in the number of benzene molecules. The energy decomposition analysis of adamantane-benzene complexes using DMA approach shows that the origin of the stability primarily arises from the dispersive interaction. The theory of atoms in molecules (AIM) supports the existence of weak interaction between the two systems. The electrostatic topography features provide clues for the mode of interaction of adamantane with benzene.

  19. Novel Stable Compounds in the C-H-O Ternary System at High Pressure.

    Science.gov (United States)

    Saleh, Gabriele; Oganov, Artem R

    2016-01-01

    The chemistry of the elements is heavily altered by high pressure, with stabilization of many new and often unexpected compounds, the emergence of which can profoundly change models of planetary interiors, where high pressure reigns. The C-H-O system is one of the most important planet-forming systems, but its high-pressure chemistry is not well known. Here, using state-of-the-art variable-composition evolutionary searches combined with quantum-mechanical calculations, we explore the C-H-O system at pressures up to 400 GPa. Besides uncovering new stable polymorphs of high-pressure elements and known molecules, we predicted the formation of new compounds. A 2CH4:3H2 inclusion compound forms at low pressure and remains stable up to 215 GPa. Carbonic acid (H2CO3), highly unstable at ambient conditions, was predicted to form exothermically at mild pressure (about 1 GPa). As pressure rises, it polymerizes and, above 314 GPa, reacts with water to form orthocarbonic acid (H4CO4). This unexpected high-pressure chemistry is rationalized by analyzing charge density and electron localization function distributions, and implications for general chemistry and planetary science are also discussed. PMID:27580525

  20. Effect of Ar/CH4 Mixture Ratio on Properties of Ag/C:H Nanocomposite Prepared by DC Sputtering

    OpenAIRE

    E. Mohsen Soltani; Ghorannevis, Z.; M. Shirazi

    2013-01-01

    Ag/C:H films were deposited by DC sputtering method on Si substrates with different Ar/CH4 gas mixture ratios. Effect of Ar/CH4 gas mixture ratios was investigated on optical and structural properties of Ag/C:H films by FTIR spectroscopy analysis, X-Ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. In order to evaluate the effect of gas flow ratio on the optical and structural properties of Ag/C:H films, Ar/CH4 gas ratio was changed...

  1. Pair-bonding in birds and the active role of females: a critical review of the empirical evidence.

    Science.gov (United States)

    Cézilly; Préault; Dubois; Faivre; Patris

    2000-10-01

    Over the recent years the role of females in maintaining or breaking the pair-bond in socially monogamous birds has received growing attention. Here, we review the overall evidence for a direct and predominant role of female behaviour in initiating or preventing divorce and its relevance for the understanding of both interspecific and intraspecific variation in divorce rate in monogamous bird species. The evidence is so far limited to a few species. We discuss the relevance of some alternative explanations and confounding factors. We conclude that the possible predominance of females in both initiating divorce or limiting its occurrence deserves further consideration. Future studies should favour experimental approaches, such as mate-removal experiments. PMID:11074313

  2. Polyvinylpyrrolidone surface modification with SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx films using Hall-type closed drift ion beam source

    International Nuclear Information System (INIS)

    In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) films were deposited on polyvinylpyrrolidone (PVP) templates of variable thickness using a Hall-type closed drift ion beam source with constant irradiation parameters. A detailed surface characterization was followed using atomic force microscopy (AFM) topography images, surface morphology parameters, height distribution histograms and bearing ratio curves with hybrid parameters. The AFM analysis directly showed that the a-C:H/SiOx/PVP and a-C:H:N/SiOx/PVP composite films represent different morphologies with characteristic surface textures. Surface adhesive properties were evaluated by measuring the force required to separate the AFM tip from the surface by means of AFM force-distance curves. The variance in adhesion force detected was lower for a-C:H/SiOx/PVP composite films due to lower structural homogeneity of the surfaces. Fourier transform infrared spectroscopy analysis was performed to study the blend behavior of PVP upon a-C:H/SiOx and a-C:H:N/SiOx direct ion beam deposition. It was determined that interfacial interactions of PVP with the direct ion beam induced changes in the carbonyl group of the PVP and are dependent on the carrier gas used for the synthesis of the amorphous hydrogenated carbon films. - Highlights: ► Polyvinylpyrrolidone (PVP) surface was modified with diamond-like carbon (DLC). ► Hall-type closed drift ion beam source was used for synthesis of DLC films. ► Surface morphological, adhesive properties and blend behavior were studied. ► Depending on thickness of PVP different surface textures were obtained. ► Changes in carbonyl group of PVP upon modification with DLC were observed

  3. A novel β-glucosidase from Aspergillus fumigates releases diosgenin from spirostanosides of Dioscorea zingiberensis C. H. Wright (DZW).

    Science.gov (United States)

    Lei, Jing; Niu, Hai; Li, Tianhong; Huang, Wen

    2012-03-01

    A β-glucosidase effectively releasing diosgenin from spirostanosides of Dioscorea zingiberensis C. H. Wright (DZW), named AfG, was purified from a strain of Aspergillus fumigates. The molecular weight of AfG was 113 kDa. Analysis of protein fragments by ESI-Q-TOF indicated that AfG was a β-glucosidase. The circular dichroism spectrum suggested that the main secondary structure of AfG in Milli-Q water was α-helixes. Atomic force microscopy revealed that it was a globular protein. AfG maintained high activity from pH 3.6 to 5.0 and from 50 to 90°C. With the strong heat stability, AfG retained 55% of its original activity at 65°C for 120 h. AfG utilized muti-3-O-glycosides of various steroidal saponins from DZW as substrate, such as trillin, diosgenin diglucoside, dioscin, deltonin and gracillin, to yield diosgenin, suggesting the possibility of producing diosgenin from total saponins of DZW using a single enzyme. PMID:22805852

  4. Studies of beauty baryon decays to $D^0 ph^-$ and $\\Lambda_c^+ h^-$ final states

    CERN Document Server

    Aaij, Roel; Adinolfi, Marco; Adrover, Cosme; Affolder, Anthony; Ajaltouni, Ziad; Albrecht, Johannes; Alessio, Federico; Alexander, Michael; Ali, Suvayu; Alkhazov, Georgy; Alvarez Cartelle, Paula; Alves Jr, Antonio; Amato, Sandra; Amerio, Silvia; Amhis, Yasmine; Anderlini, Lucio; Anderson, Jonathan; Andreassen, Rolf; Andreotti, Mirco; Andrews, Jason; Appleby, Robert; Aquines Gutierrez, Osvaldo; Archilli, Flavio; Artamonov, Alexander; Artuso, Marina; Aslanides, Elie; Auriemma, Giulio; Baalouch, Marouen; Bachmann, Sebastian; Back, John; Badalov, Alexey; Balagura, Vladislav; Baldini, Wander; Barlow, Roger; Barschel, Colin; Barsuk, Sergey; Barter, William; Batozskaya, Varvara; Bauer, Thomas; Bay, Aurelio; Beddow, John; Bedeschi, Franco; Bediaga, Ignacio; Belogurov, Sergey; Belous, Konstantin; Belyaev, Ivan; Ben-Haim, Eli; Bencivenni, Giovanni; Benson, Sean; Benton, Jack; Berezhnoy, Alexander; Bernet, Roland; Bettler, Marc-Olivier; van Beuzekom, Martinus; Bien, Alexander; Bifani, Simone; Bird, Thomas; Bizzeti, Andrea; Bjørnstad, Pål Marius; Blake, Thomas; Blanc, Frédéric; Blouw, Johan; Blusk, Steven; Bocci, Valerio; Bondar, Alexander; Bondar, Nikolay; Bonivento, Walter; Borghi, Silvia; Borgia, Alessandra; Bowcock, Themistocles; Bowen, Espen Eie; Bozzi, Concezio; Brambach, Tobias; van den Brand, Johannes; Bressieux, Joël; Brett, David; Britsch, Markward; Britton, Thomas; Brook, Nicholas; Brown, Henry; Bursche, Albert; Busetto, Giovanni; Buytaert, Jan; Cadeddu, Sandro; Calabrese, Roberto; Callot, Olivier; Calvi, Marta; Calvo Gomez, Miriam; Camboni, Alessandro; Campana, Pierluigi; Campora Perez, Daniel; Carbone, Angelo; Carboni, Giovanni; Cardinale, Roberta; Cardini, Alessandro; Carranza-Mejia, Hector; Carson, Laurence; Carvalho Akiba, Kazuyoshi; Casse, Gianluigi; Castillo Garcia, Lucia; Cattaneo, Marco; Cauet, Christophe; Cenci, Riccardo; Charles, Matthew; Charpentier, Philippe; Cheung, Shu-Faye; Chiapolini, Nicola; Chrzaszcz, Marcin; Ciba, Krzystof; Cid Vidal, Xabier; Ciezarek, Gregory; Clarke, Peter; Clemencic, Marco; Cliff, Harry; Closier, Joel; Coca, Cornelia; Coco, Victor; Cogan, Julien; Cogneras, Eric; Collins, Paula; Comerma-Montells, Albert; Contu, Andrea; Cook, Andrew; Coombes, Matthew; Coquereau, Samuel; Corti, Gloria; Couturier, Benjamin; Cowan, Greig; Craik, Daniel Charles; Cruz Torres, Melissa Maria; Cunliffe, Samuel; Currie, Robert; D'Ambrosio, Carmelo; Dalseno, Jeremy; David, Pascal; David, Pieter; Davis, Adam; De Bonis, Isabelle; De Bruyn, Kristof; De Capua, Stefano; De Cian, Michel; De Miranda, Jussara; De Paula, Leandro; De Silva, Weeraddana; De Simone, Patrizia; Decamp, Daniel; Deckenhoff, Mirko; Del Buono, Luigi; Déléage, Nicolas; Derkach, Denis; Deschamps, Olivier; Dettori, Francesco; Di Canto, Angelo; Dijkstra, Hans; Dogaru, Marius; Donleavy, Stephanie; Dordei, Francesca; Dorosz, Piotr; Dosil Suárez, Alvaro; Dossett, David; Dovbnya, Anatoliy; Dupertuis, Frederic; Durante, Paolo; Dzhelyadin, Rustem; Dziurda, Agnieszka; Dzyuba, Alexey; Easo, Sajan; Egede, Ulrik; Egorychev, Victor; Eidelman, Semen; van Eijk, Daan; Eisenhardt, Stephan; Eitschberger, Ulrich; Ekelhof, Robert; Eklund, Lars; El Rifai, Ibrahim; Elsasser, Christian; Falabella, Antonio; Färber, Christian; Farinelli, Chiara; Farry, Stephen; Ferguson, Dianne; Fernandez Albor, Victor; Ferreira Rodrigues, Fernando; Ferro-Luzzi, Massimiliano; Filippov, Sergey; Fiore, Marco; Fiorini, Massimiliano; Fitzpatrick, Conor; Fontana, Marianna; Fontanelli, Flavio; Forty, Roger; Francisco, Oscar; Frank, Markus; Frei, Christoph; Frosini, Maddalena; Furfaro, Emiliano; Gallas Torreira, Abraham; Galli, Domenico; Gandelman, Miriam; Gandini, Paolo; Gao, Yuanning; Garofoli, Justin; Garosi, Paola; Garra Tico, Jordi; Garrido, Lluis; Gaspar, Clara; Gauld, Rhorry; Gersabeck, Evelina; Gersabeck, Marco; Gershon, Timothy; Ghez, Philippe; Gibson, Valerie; Giubega, Lavinia-Helena; Gligorov, Vladimir; Göbel, Carla; Golubkov, Dmitry; Golutvin, Andrey; Gomes, Alvaro; Gordon, Hamish; Grabalosa Gándara, Marc; Graciani Diaz, Ricardo; Granado Cardoso, Luis Alberto; Graugés, Eugeni; Graziani, Giacomo; Grecu, Alexandru; Greening, Edward; Gregson, Sam; Griffith, Peter; Grillo, Lucia; Grünberg, Oliver; Gui, Bin; Gushchin, Evgeny; Guz, Yury; Gys, Thierry; Hadjivasiliou, Christos; Haefeli, Guido; Haen, Christophe; Hafkenscheid, Tom; Haines, Susan; Hall, Samuel; Hamilton, Brian; Hampson, Thomas; Hansmann-Menzemer, Stephanie; Harnew, Neville; Harnew, Samuel; Harrison, Jonathan; Hartmann, Thomas; He, Jibo; Head, Timothy; Heijne, Veerle; Hennessy, Karol; Henrard, Pierre; Hernando Morata, Jose Angel; van Herwijnen, Eric; Heß, Miriam; Hicheur, Adlène; Hicks, Emma; Hill, Donal; Hoballah, Mostafa; Hombach, Christoph; Hulsbergen, Wouter; Hunt, Philip; Huse, Torkjell; Hussain, Nazim; Hutchcroft, David; Hynds, Daniel; Iakovenko, Viktor; Idzik, Marek; Ilten, Philip; Jacobsson, Richard; Jaeger, Andreas; Jans, Eddy; Jaton, Pierre; Jawahery, Abolhassan; Jing, Fanfan; John, Malcolm; Johnson, Daniel; Jones, Christopher; Joram, Christian; Jost, Beat; Jurik, Nathan; Kaballo, Michael; Kandybei, Sergii; Kanso, Wallaa; Karacson, Matthias; Karbach, Moritz; Kenyon, Ian; Ketel, Tjeerd; Khanji, Basem; Klaver, Suzanne; Kochebina, Olga; Komarov, Ilya; Koopman, Rose; Koppenburg, Patrick; Korolev, Mikhail; Kozlinskiy, Alexandr; Kravchuk, Leonid; Kreplin, Katharina; Kreps, Michal; Krocker, Georg; Krokovny, Pavel; Kruse, Florian; Kucharczyk, Marcin; Kudryavtsev, Vasily; Kurek, Krzysztof; Kvaratskheliya, Tengiz; La Thi, Viet Nga; Lacarrere, Daniel; Lafferty, George; Lai, Adriano; Lambert, Dean; Lambert, Robert W; Lanciotti, Elisa; Lanfranchi, Gaia; Langenbruch, Christoph; Latham, Thomas; Lazzeroni, Cristina; Le Gac, Renaud; van Leerdam, Jeroen; Lees, Jean-Pierre; Lefèvre, Regis; Leflat, Alexander; Lefrançois, Jacques; Leo, Sabato; Leroy, Olivier; Lesiak, Tadeusz; Leverington, Blake; Li, Yiming; Li Gioi, Luigi; Liles, Myfanwy; Lindner, Rolf; Linn, Christian; Lionetto, Federica; Liu, Bo; Liu, Guoming; Lohn, Stefan; Longstaff, Ian; Lopes, Jose; Lopez-March, Neus; Lu, Haiting; Lucchesi, Donatella; Luisier, Johan; Luo, Haofei; Luppi, Eleonora; Lupton, Oliver; Machefert, Frederic; Machikhiliyan, Irina V; Maciuc, Florin; Maev, Oleg; Malde, Sneha; Manca, Giulia; Mancinelli, Giampiero; Maratas, Jan; Marconi, Umberto; Marino, Pietro; Märki, Raphael; Marks, Jörg; Martellotti, Giuseppe; Martens, Aurelien; Martín Sánchez, Alexandra; Martinelli, Maurizio; Martinez Santos, Diego; Martins Tostes, Danielle; Martynov, Aleksandr; Massafferri, André; Matev, Rosen; Mathe, Zoltan; Matteuzzi, Clara; Maurice, Emilie; Mazurov, Alexander; McCann, Michael; McCarthy, James; McNab, Andrew; McNulty, Ronan; McSkelly, Ben; Meadows, Brian; Meier, Frank; Meissner, Marco; Merk, Marcel; Milanes, Diego Alejandro; Minard, Marie-Noelle; Molina Rodriguez, Josue; Monteil, Stephane; Moran, Dermot; Morawski, Piotr; Mordà, Alessandro; Morello, Michael Joseph; Mountain, Raymond; Mous, Ivan; Muheim, Franz; Müller, Katharina; Muresan, Raluca; Muryn, Bogdan; Muster, Bastien; Naik, Paras; Nakada, Tatsuya; Nandakumar, Raja; Nasteva, Irina; Needham, Matthew; Neubert, Sebastian; Neufeld, Niko; Nguyen, Anh Duc; Nguyen, Thi-Dung; Nguyen-Mau, Chung; Nicol, Michelle; Niess, Valentin; Niet, Ramon; Nikitin, Nikolay; Nikodem, Thomas; Nomerotski, Andrey; Novoselov, Alexey; Oblakowska-Mucha, Agnieszka; Obraztsov, Vladimir; Oggero, Serena; Ogilvy, Stephen; Okhrimenko, Oleksandr; Oldeman, Rudolf; Onderwater, Gerco; Orlandea, Marius; Otalora Goicochea, Juan Martin; Owen, Patrick; Oyanguren, Maria Arantza; Pal, Bilas Kanti; Palano, Antimo; Palutan, Matteo; Panman, Jacob; Papanestis, Antonios; Pappagallo, Marco; Pappalardo, Luciano; Parkes, Christopher; Parkinson, Christopher John; Passaleva, Giovanni; Patel, Girish; Patel, Mitesh; Patrignani, Claudia; Pavel-Nicorescu, Carmen; Pazos Alvarez, Antonio; Pearce, Alex; Pellegrino, Antonio; Penso, Gianni; Pepe Altarelli, Monica; Perazzini, Stefano; Perez Trigo, Eliseo; Pérez-Calero Yzquierdo, Antonio; Perret, Pascal; Perrin-Terrin, Mathieu; Pescatore, Luca; Pesen, Erhan; Pessina, Gianluigi; Petridis, Konstantin; Petrolini, Alessandro; Picatoste Olloqui, Eduardo; Pietrzyk, Boleslaw; Pilař, Tomas; Pinci, Davide; Playfer, Stephen; Plo Casasus, Maximo; Polci, Francesco; Polok, Grzegorz; Poluektov, Anton; Polycarpo, Erica; Popov, Alexander; Popov, Dmitry; Popovici, Bogdan; Potterat, Cédric; Powell, Andrew; Prisciandaro, Jessica; Pritchard, Adrian; Prouve, Claire; Pugatch, Valery; Puig Navarro, Albert; Punzi, Giovanni; Qian, Wenbin; Rachwal, Bartolomiej; Rademacker, Jonas; Rakotomiaramanana, Barinjaka; Rangel, Murilo; Raniuk, Iurii; Rauschmayr, Nathalie; Raven, Gerhard; Redford, Sophie; Reichert, Stefanie; Reid, Matthew; dos Reis, Alberto; Ricciardi, Stefania; Richards, Alexander; Rinnert, Kurt; Rives Molina, Vincente; Roa Romero, Diego; Robbe, Patrick; Roberts, Douglas; Rodrigues, Ana Barbara; Rodrigues, Eduardo; Rodriguez Perez, Pablo; Roiser, Stefan; Romanovsky, Vladimir; Romero Vidal, Antonio; Rotondo, Marcello; Rouvinet, Julien; Ruf, Thomas; Ruffini, Fabrizio; Ruiz, Hugo; Ruiz Valls, Pablo; Sabatino, Giovanni; Saborido Silva, Juan Jose; Sagidova, Naylya; Sail, Paul; Saitta, Biagio; Salustino Guimaraes, Valdir; Sanmartin Sedes, Brais; Santacesaria, Roberta; Santamarina Rios, Cibran; Santovetti, Emanuele; Sapunov, Matvey; Sarti, Alessio; Satriano, Celestina; Satta, Alessia; Savrie, Mauro; Savrina, Darya; Schiller, Manuel; Schindler, Heinrich; Schlupp, Maximilian; Schmelling, Michael; Schmidt, Burkhard; Schneider, Olivier; Schopper, Andreas; Schune, Marie Helene; Schwemmer, Rainer; Sciascia, Barbara; Sciubba, Adalberto; Seco, Marcos; Semennikov, Alexander; Senderowska, Katarzyna; Sepp, Indrek; Serra, Nicola; Serrano, Justine; Seyfert, Paul; Shapkin, Mikhail; Shapoval, Illya; Shcheglov, Yury; Shears, Tara; Shekhtman, Lev; Shevchenko, Oksana; Shevchenko, Vladimir; Shires, Alexander; Silva Coutinho, Rafael; Sirendi, Marek; Skidmore, Nicola; Skwarnicki, Tomasz; Smith, Anthony; Smith, Edmund; Smith, Eluned; Smith, Jackson; Smith, Mark; Sokoloff, Michael; Soler, Paul; Soomro, Fatima; Souza, Daniel; Souza De Paula, Bruno; Spaan, Bernhard; Sparkes, Ailsa; Spradlin, Patrick; Stagni, Federico; Stahl, Sascha; Steinkamp, Olaf; Stevenson, Scott; Stoica, Sabin; Stone, Sheldon; Storaci, Barbara; Stracka, Simone; Straticiuc, Mihai; Straumann, Ulrich; Subbiah, Vijay Kartik; Sun, Liang; Sutcliffe, William; Swientek, Stefan; Syropoulos, Vasileios; Szczekowski, Marek; Szczypka, Paul; Szilard, Daniela; Szumlak, Tomasz; T'Jampens, Stephane; Teklishyn, Maksym; Tellarini, Giulia; Teodorescu, Eliza; Teubert, Frederic; Thomas, Christopher; Thomas, Eric; van Tilburg, Jeroen; Tisserand, Vincent; Tobin, Mark; Tolk, Siim; Tomassetti, Luca; Tonelli, Diego; Topp-Joergensen, Stig; Torr, Nicholas; Tournefier, Edwige; Tourneur, Stephane; Tran, Minh Tâm; Tresch, Marco; Tsaregorodtsev, Andrei; Tsopelas, Panagiotis; Tuning, Niels; Ubeda Garcia, Mario; Ukleja, Artur; Ustyuzhanin, Andrey; Uwer, Ulrich; Vagnoni, Vincenzo; Valenti, Giovanni; Vallier, Alexis; Vazquez Gomez, Ricardo; Vazquez Regueiro, Pablo; Vázquez Sierra, Carlos; Vecchi, Stefania; Velthuis, Jaap; Veltri, Michele; Veneziano, Giovanni; Vesterinen, Mika; Viaud, Benoit; Vieira, Daniel; Vilasis-Cardona, Xavier; Vollhardt, Achim; Volyanskyy, Dmytro; Voong, David; Vorobyev, Alexey; Vorobyev, Vitaly; Voß, Christian; Voss, Helge; de Vries, Jacco; Waldi, Roland; Wallace, Charlotte; Wallace, Ronan; Wandernoth, Sebastian; Wang, Jianchun; Ward, David; Watson, Nigel; Webber, Adam Dane; Websdale, David; Whitehead, Mark; Wicht, Jean; Wiechczynski, Jaroslaw; Wiedner, Dirk; Wiggers, Leo; Wilkinson, Guy; Williams, Matthew; Williams, Mike; Wilson, Fergus; Wimberley, Jack; Wishahi, Julian; Wislicki, Wojciech; Witek, Mariusz; Wormser, Guy; Wotton, Stephen; Wright, Simon; Wu, Suzhi; Wyllie, Kenneth; Xie, Yuehong; Xing, Zhou; Yang, Zhenwei; Yuan, Xuhao; Yushchenko, Oleg; Zangoli, Maria; Zavertyaev, Mikhail; Zhang, Feng; Zhang, Liming; Zhang, Wen Chao; Zhang, Yanxi; Zhelezov, Alexey; Zhokhov, Anatoly; Zhong, Liang; Zvyagin, Alexander

    2014-01-01

    Decays of beauty baryons to the $D^0 p h^-$ and $\\Lambda_c^+ h^-$ final states (where $h$ indicates a pion or a kaon) are studied using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb detector. The Cabibbo-suppressed decays $\\Lambda_b^0\\to D^0 p K^-$ and $\\Lambda_b^0\\to \\Lambda_c^+ K^-$ are observed and their branching fractions are measured with respect to the decays $\\Lambda_b^0\\to D^0 p \\pi^-$ and $\\Lambda_b^0\\to \\Lambda_c^+ \\pi^-$. In addition, the first observation is reported of the decay of the neutral beauty-strange baryon $\\Xi_b^0$ to the $D^0 p K^-$ final state, and a measurement of the $\\Xi_b^0$ mass is performed. Evidence of the $\\Xi_b^0\\to \\Lambda_c^+ K^-$ decay is also reported.

  5. Recommended Thermal Rate Coefficients for the C + H$_3^+$ Reaction and Some Astrochemical Implications

    CERN Document Server

    Vissapragada, S; Miller, K A; O'Connor, A P; de Ruette, N; Urbain, X; Savin, D W

    2016-01-01

    We have incorporated our experimentally derived thermal rate coefficients for C + H$_3^+$ forming CH$^+$ and CH$_2^+$ into a commonly used astrochemical model. We find that the Arrhenius-Kooij equation typically used in chemical models does not accurately fit our data and use instead a more versatile fitting formula. At a temperature of 10 K and a density of 10$^4$ cm$^{-3}$, we find no significant differences in the predicted chemical abundances, but at higher temperatures of 50, 100, and 300 K we find up to factor of 2 changes. Additionally, we find that the relatively small error on our thermal rate coefficients, $\\sim15\\%$, significantly reduces the uncertainties on the predicted abundances compared to those obtained using the currently implemented Langevin rate coefficient with its estimated factor of 2 uncertainty.

  6. Rapid thermal annealing of Amorphous Hydrogenated Carbon (a-C:H) films

    Science.gov (United States)

    Alterovitz, Samuel A.; Pouch, John J.; Warner, Joseph D.

    1987-01-01

    Amorphous hydrogenated carbon (a-C:H) films were deposited on silicon and quartz substrates by a 30 kHz plasma discharge technique using methane. Rapid thermal processing of the films was accomplished in nitrogen gas using tungsten halogen light. The rapid thermal processing was done at several fixed temperatures (up to 600 C), as a function of time (up to 1800 sec). The films were characterized by optical absorption and by ellipsometry in the near UV and the visible. The bandgap, estimated from extrapolation of the linear part of a Tauc plot, decreases both with the annealing temperature and the annealing time, with the temperature dependence being the dominating factor. The density of states parameter increases up to 25 percent and the refractive index changes up to 20 percent with temperature increase. Possible explanations of the mechanisms involved in these processes are discussed.

  7. Erosion of a-C:H in the afterglow of ammonia plasma

    Science.gov (United States)

    Drenik, Aleksander; Mourkas, Angelos; Zaplotnik, Rok; Primc, Gregor; Mozetič, Miran; Panjan, Peter; Alegre, Daniel; Tabarés, Francisco L.

    2016-07-01

    Amorphous hydrogenated carbon (a-C:H) deposits were eroded in the afterglow of a NH3 plasma, created with an inductively coupled RF generator in pure NH3 at the gas pressure of 50 Pa. The plasma system was characterised by optical emission spectroscopy and mass spectrometry, and the erosion process was monitored in-situ with a laser interferometry system. Based on the mass spectrometry measurements, the degree of dissociation of the NH3 molecules was estimated at 90% at the highest generator forward power in the discharge region, however the densities of N and H atoms were significantly smaller at the location of the sample holder. The erosion rates were found to increase with surface temperature and forward generator power. In the high dissociation regime, the composition of the afterglow and the reaction products highlight the role of N atoms in the erosion process.

  8. R.E.A.C.H. to Teach: Making Patient and Family Education "Stick".

    Science.gov (United States)

    Cutilli, Carolyn Crane

    2016-01-01

    Healthcare professionals teach patients and families about their health every day. Regulatory and accreditation organizations mandate patient and family education to promote better health outcomes. And recently, financial rewards for healthcare organizations are being tied to patient satisfaction (Hospital Consumer Assessment of Healthcare Providers and Systems-HCAHPS). A University of Pennsylvania Health System group of staff and patients, devoted to excellence in patient and family education, developed the graphic "R.E.A.C.H. to Teach." The purpose of the graphic is to make evidence-based practice (EBP) for patient and family education "stick" with staff. The group used concepts from the marketing book, Made to Stick, to demonstrate how to develop effective staff and patient and family education. Ideas (education) that survive ("stick") have the following attributes: simple, unexpected, concrete, credible, emotional, and narrative (story). This article demonstrates how to apply these principles and EBP to patient and family education. PMID:27441879

  9. C-H arylation of azaheterocycles: a direct ligand-free and Cu-catalyzed approach using diaryliodonium salts.

    Science.gov (United States)

    Kumar, Dalip; Pilania, Meenakshi; Arun, V; Pooniya, Savita

    2014-09-01

    An efficient and high yielding Cu-catalyzed direct C-H arylation of azaheterocycles including oxadiazoles, thiadiazoles, benzoxazoles and benzothiazoles has been achieved by employing easily accessible diaryliodonium salts. PMID:25017573

  10. Deposition of a-C:H films on inner surface of high-aspect-ratio microchannel

    Science.gov (United States)

    Hirata, Yuki; Choi, Junho

    2016-08-01

    Hydrogenated amorphous carbon (a-C:H) films were prepared on inner surface of 100-μm-width microchannel by using a bipolar-type plasma based ion implantation and deposition. The microchannel was fabricated using a silicon plate, and two kinds of microchannels were prepared, namely, with a bottom layer (open at one end) and without a bottom layer (open at both ends). The distribution of thickness and hardness of films was evaluated by SEM and nanoindentation measurements, respectively, and the microstructures of films were evaluated by Raman spectroscopy. Furthermore, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision and Direct Simulation Monte Carlo to investigate the coating mechanism for the microchannel. It was found that the film thickness decreased as the depth of the coating position increased in the microchannels where it is open at one end. The uniformity of the film thickness improved by increasing the negative pulse voltage because ions can arrive at the deeper part of the microchannel. In addition, the hardness increased as the depth of the coating position increased. This is because the radicals do not arrive at the deeper part of the microchannel, and the incident proportion of ions relative to that of radicals increases, resulting in a high hardness due to the amorphization of the film. The opening area of the microchannel where the aspect ratio is very small, radicals dominate the incident flux, whereas ions prevail over radicals above an aspect ratio of about 7.5. On the other hand, in the microchannels that are open at both ends, there were great improvements in uniformity of the film thickness, hardness, and the film structure. The a-C:H films were successfully deposited on the entire inner surface of a microchannel with an aspect ratio of 20.

  11. Accurate NMR determination of C-H or N-H distances for unlabeled molecules.

    Science.gov (United States)

    Nishiyama, Y; Malon, M; Potrzebowski, M J; Paluch, P; Amoureux, J P

    2016-02-01

    Cross-Polarization with Variable Contact-time (CP-VC) is very efficient at ultra-fast MAS (νR ≥ 60 kHz) to measure accurately the dipolar interactions corresponding to C-H or N-H short distances, which are very useful for resonance assignment and for analysis of dynamics. Here, we demonstrate the CP-VC experiment with (1)H detection. In the case of C-H distances, we compare the CP-VC signals with direct ((13)C) and indirect ((1)H) detection and find that the latter allows a S/N gain of ca. 2.5, which means a gain of ca. 6 in experimental time. The main powerful characteristics of CP-VC methods are related to the ultra-fast spinning speed and to the fact that most of the time only the value of the dipolar peak separation has to be used to obtain the information. As a result, CP-VC methods are: (i) easy to set up and to use, and robust with respect to (ii) rf-inhomogeneity thus allowing the use of full rotor samples, (iii) rf mismatch, and (iv) offsets and chemical shift anisotropies. It must be noted that the CP-VC 2D method with indirect (1)H detection requires the proton resolution and is thus mainly applicable to small or perdeuterated molecules. We also show that an analysis of the dynamics can even be performed, with a reasonable experimental time, on unlabeled samples with (13)C or even (15)N natural abundance. PMID:26169913

  12. Enantioselective Allylic C-H Oxidation of Terminal Olefins to Isochromans by Palladium(II)/Chiral Sulfoxide Catalysis.

    Science.gov (United States)

    Ammann, Stephen E; Liu, Wei; White, M Christina

    2016-08-01

    The enantioselective synthesis of isochroman motifs has been accomplished by palladium(II)-catalyzed allylic C-H oxidation from terminal olefin precursors. Critical to the success of this goal was the development and utilization of a novel chiral aryl sulfoxide-oxazoline (ArSOX) ligand. The allylic C-H oxidation reaction proceeds with the broadest scope and highest levels of asymmetric induction reported to date (avg. 92 % ee, 13 examples with greater than 90 % ee). PMID:27376625

  13. Convergent Synthesis of Diverse Nitrogen Heterocycles via Rh(III)-Catalyzed C-H Conjugate Addition/Cyclization Reactions.

    Science.gov (United States)

    Weinstein, Adam B; Ellman, Jonathan A

    2016-07-01

    The development of Rh(III)-catalyzed C-H conjugate addition/cyclization reactions that provide access to synthetically useful fused bi- and tricyclic nitrogen heterocycles is reported. A broad scope of C-H functionalization substrates and electrophilic olefin coupling partners is effective, and depending on the nature of the directing group, cyclic imide, amide, or heteroaromatic products are obtained. An efficient synthesis of a pyrrolophenanthridine alkaloid natural product, oxoassoanine, highlights the utility of this method. PMID:27337641

  14. CQ-397 and CQ-414: antimicrobial activity and spectrum of two fluoroquinolone---cephalosporin, dual-action compounds with carboxamido bonds.

    Science.gov (United States)

    Johnson, David M.; Jones, Ronald N.

    1997-06-01

    OBJECTIVE: To evaluate the potential spectrum of activity of two novel dual-action compounds with carboxamido bonds (CQ-397 and CQ-414; Laboratorios Aranda, San Rafael, Mexico) against human pathogens. METHODS: Approximately 800 Gram-positive and Gram-negative aerobic clinical bacteria were tested in vitro using the Mueller-Hinton broth microdilution method of the National Committee of Clinical Laboratory Standards. RESULTS: CQ-397 (cefamandole+enrofloxacin) and CQ-414 (cefamandole+norfloxacin) were equally potent against Enterobacteriaceae (MIC90 range, 0.06--0.5 microg/mL and 0.06--1 microg/mL, respectively). Citrobacter freundii (MIC90, 4 microg/mL) and Providencia spp. (MIC90, >32 microg/mL) exhibited elevated study drug MICs. Enterobacteriaceae resistant to fluoroquinolones generally remained resistant. CQ-397 and CQ-414 were active against Stenotrophomonas maltophilia (MIC90, 4 microg/mL) and oxacillin-susceptible staphylococci (MIC90, 0.25 microg/mL), but not oxacillin-resistant Staphylococcus aureus (MIC90, >32 microg/mL), Staphylococcus epidermidis (MIC90, 8 microg/mL), and enterococci (MIC90s, 8 to >32 microg/mL). There was no difference in the dual-action drug activity (MIC90, 2 microg/mL) between penicillin-susceptible and -resistant pneumococci. Haemophilus influenzae and Moraxella catarrhalis were very susceptible (MIC range, less-than-or-equal0.015--0.06 microg/mL) to both compounds. CONCLUSIONS: The activity of these novel dual-action compounds, formed from the bonding of older antimicrobials, warrants further investigation for potential human and/or animal health use, including toxicology and pharmacokinetics. PMID:11864130

  15. Study of optical sensors of the form Al/a-SiC:H/c-Si(n with high sensitivity.

    Directory of Open Access Journals (Sweden)

    L. Magafas

    2008-06-01

    Full Text Available In the present work optical sensors of the form Al/a-SiC:H/c-Si(n, for different thickness of a-SiC:H thin films are stud-ied. More specifically, a-SiC:H thin films were deposited by rf sputtering technique on c-Si(n substrates for different thickness of the amorphous semiconductor and, subsequently, the samples were annealed in the temperature range from 300oC up to 675 oC. Experimental measurements of the optical response of these sensors showed that for thicknesses of a-SiC:H greater than a critical value, which depends on annealing temperature, a mechanism of losses is appeared in the region of wavelengths from 525nm up to 625nm. This behaviour is attributed to the recombination of photo-generated electrons-hole pairs in the neutral region of a-SiC:H, when this exceeds the diffusion length of minority carries, Lp. Also, the value of the reverse bias voltage appears to influence considerably the optical response of these sensors when d > Lp in the case where the a-SiC: H thin films were annealed at 600oC.

  16. The C--H Stretching Features at 3.2--3.5 Micrometer of Polycyclic Aromatic Hydrocarbons with Aliphatic Sidegroups

    CERN Document Server

    Yang, Xuejuan; Glaser, Rainer; Zhong, Jianxin

    2016-01-01

    The so-called unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 micrometer are ubiquitously seen in a wide variety of astrophysical regions. The UIE features are characteristic of the stretching and bending vibrations of aromatic hydrocarbon materials, e.g., polycyclic aromatic hydrocarbon (PAH) molecules. The 3.3 micrometer aromatic C--H stretching feature is often accompanied by a weaker feature at 3.4 micrometer. The latter is often thought to result from the C--H stretch of aliphatic groups attached to the aromatic systems. The ratio of the observed intensity of the 3.3 micrometer aromatic C--H feature to that of the 3.4 micrometer aliphatic C--H feature allows one to estimate the aliphatic fraction of the UIE carriers, provided that the intrinsic oscillator strengths of the 3.3 micrometer aromatic C--H stretch (A3.3) and the 3.4 micrometer aliphatic C--H stretch (A3.4) are known. While previous studies on the aliphatic fraction of the UIE carriers were mostly based on the A3.4...

  17. Oxidative coupling between C(sp(2))-H and C(sp(3))-H bonds of indoles and cyclic ethers/cycloalkanes.

    Science.gov (United States)

    Yang, Qingjing; Choy, Pui Ying; Wu, Yinuo; Fan, Baomin; Kwong, Fuk Yee

    2016-02-24

    Cross-dehydrogenative-coupling (CDC) between C-H/C-H bonds of indoles and cyclic ethers/cycloalkanes is made viable through a simple transition-metal-free pathway. With the aid of only di-tert-butyl peroxide, a number of inactive cyclic ethers and cycloalkanes can be directly coupled with indole derivatives in satisfactory yields. PMID:26842403

  18. Subsurface defect detection in first layer of pavement structure and reinforced civil engineering structure by FRP bonding using active infrared thermography

    Science.gov (United States)

    Dumoulin, Jean; Ibos, Laurent

    2010-05-01

    In many countries road network ages while road traffic and maintenance costs increase. Nowadays, thousand and thousand kilometers of roads are each year submitted to surface distress survey. They generally lean on pavement surface imaging measurement techniques, mainly in the visible spectrum, coupled with visual inspection or image processing detection of emergent distresses. Nevertheless, optimisation of maintenance works and costs requires an early detection of defects within the pavement structure when they still are hidden from surface. Accordingly, alternative measurement techniques for pavement monitoring are currently under investigation (seismic methods, step frequency radar). On the other hand, strengthening or retrofitting of reinforced concrete structures by externally bonded Fiber Reinforced Polymer (FRP) systems is now a commonly accepted and widespread technique. However, the use of bonding techniques always implies following rigorous installing procedures. To ensure the durability and long-term performance of the FRP reinforcements, conformance checking through an in situ auscultation of the bonded FRP systems is then highly suitable. The quality-control program should involve a set of adequate inspections and tests. Visual inspection and acoustic sounding (hammer tap) are commonly used to detect delaminations (disbonds) but are unable to provide sufficient information about the depth (in case of multilayered composite) and width of debonded areas. Consequently, rapid and efficient inspection methods are also required. Among the non destructive methods under study, active infrared thermography was investigated both for pavement and civil engineering structures through experiments in laboratory and numerical simulations, because of its ability to be also used on field. Pulse Thermography (PT), Pulse Phase Thermography (PPT) and Principal Component Thermography (PCT) approaches have been tested onto pavement samples and CFRP bonding on concrete

  19. Purinyl N(3)-Directed Palladium-Catalyzed C-H Alkoxylation of N(9)-Arylpurines: A Late-Stage Strategy to Synthesize N(9)-(ortho-Alkoxyl)arylpurines.

    Science.gov (United States)

    Yu, Mingwu; Wang, Zhiqian; Tian, Miao; Lu, Chenghu; Li, Shunlai; Du, Hongguang

    2016-04-15

    A palladium-catalyzed alkoxylation of N(9)-arylpurines with primary or secondary alcohols has been developed successfully, which is a rare C-H activation reaction of polynitrogenated purines and offers a late-stage strategy to synthesize N(9)-(ortho-alkoxyl)arylpurines. Although there are more than four nitrogen atoms present in the purine moiety, the reaction can be effectively conducted by sterically blocking the N(1) site for catalyst coordination and first employing the purinyl N(3) atom as a directing group. PMID:27015589

  20. J.C.H. de Meijere (1866-1947, een voorzichtig geneticus en evolutiebioloog

    Directory of Open Access Journals (Sweden)

    W.J. van der Schoor

    1991-04-01

    Full Text Available

    J.C.H. de Meijere (1866-1947, a cautious geneticist and evolutionary biologist

    After the success of Hugo de Vries' 'mutationism' during the socalled 'Eclipse of Darwinism' (see Bowler, 1983, Dutch biologists in the 20's and 30's had little interest in evolutionary theory. A remarkable exception was the entomologist J.C.H. de Meijere, who thought technical zoology and (1921-1936 genetics at Amsterdam University. De Meijere's career as a systematist, morphologist and (at the same time geneticist contradicts G.E. Allen's 'revolt from morphology' hypothesis, following which a generation conflict was involved in the rise of experimental biology (see Allen, 1975. Although he had been trained in the nineteenth-century 'classical' descriptive tradition, his early articles on Mendelian genetics (1910-1915 showed distinctly 'experimental'-analytical features concerning their problem-definition. He did not carry out genetic experiments himself, due to a lack of time.

    In this paper I have analysed De Meijere's work on phylogenetic morphology, genetics and evolutionary biology. As a morphologist, De Meijere fits perfectly in the pattern of Dutch academical zoology of this period (see Theunissen and Donath, 1986. As a geneticist, he focussed on transmission genetics. He adopted Morgan's concept of gene mutation but at the same time he refused to reject neo-Lamarckian inheritance.

    His opinions on evolutionary issues were eclectic and somewhat cautious. He held a pluralistic view on the mechanisms of evolution, including Morgan mutation, 'moderate' Darwinian natural selection and neo-Lamarckian inheritance of acquired characters. Population genetics was absent in his writings.

    De Meijere's opinions on evolution united elements of descriptive and experimental traditions in biology, but this did not result in an evolutionary synthesis in a neo- Darwinian or any other sense. This stresses the importance of

  1. Hydrogen bonded C-H···Y (Y = O, S, Hal) molecular complexes: A natural bond orbital analysis

    Science.gov (United States)

    Isaev, A. N.

    2016-03-01

    Hydrogen bonded C-H···Y complexes formed by H2O, H2S molecules, hydrogen halides, and halogen-ions with methane, halogen substituted methane as well as with the C2H2 and NCH molecules were studied at the MP2/aug-cc-pVDZ level. The structure of NBOs corresponding to lone pair of acceptor Y, n Y, and vacant anti-σ-bond C-H of proton donor was analyzed and estimates of second order perturbation energy E(2) characterizing donor-acceptor n Y → σ C-H * charge-transfer interaction were obtained. Computational results for complexes of methane and its halogen substituted derivatives show that for each set of analogous structures, the EnY→σ*C-H (2) energy tends to grow with an increase in the s-component percentage in the lone pair NBO of acceptor Y. Calculations for different C···Y distances show that the equilibrium geometries of complexes lie in the region where the E(2) energy is highest and it changes symbatically with the length of the covalent E-H bond when the R(C···Y) distance is varied. The performed analysis allows us to divide the hydrogen bonded complexes into two groups, depending on the pattern of overlapping for NBOs of the hydrogen bridge.

  2. N-Methylphthalimide-substituted benzimidazolium salts and PEPPSI Pd–NHC complexes: synthesis, characterization and catalytic activity in carbon–carbon bond-forming reactions

    Science.gov (United States)

    Gök, Yetkin; İlhan, İlhan Özer

    2016-01-01

    Summary A series of novel benzimidazolium salts (1–4) and their pyridine enhanced precatalyst preparation stabilization and initiation (PEPPSI) themed palladium N-heterocyclic carbene complexes [PdCl2(NHC)(Py)] (5–8), where NHC = 1-(N-methylphthalimide)-3-alkylbenzimidazolin-2-ylidene and Py = 3-chloropyridine, were synthesized and characterized by means of 1H and 13C{1H} NMR, UV–vis (for 5–8), ESI-FTICR-MS (for 2, 4, 6–8) and FTIR spectroscopic methods and elemental analysis. The synthesized compounds were tested in Suzuki–Miyaura cross-coupling (for 1–8) and arylation (for 5–8) reactions. As catalysts, they demonstrated a highly efficient route for the formation of asymmetric biaryl compounds even though they were used in very low loading. For example, all compounds displayed good catalytic activity for the C–C bond formation of 4-tert-butylphenylboronic acid with 4-chlorotoluene. PMID:26877810

  3. Carbon dioxide as a carbon source in organic transformation: carbon-carbon bond forming reactions by transition-metal catalysts.

    OpenAIRE

    Tsuji, Yasushi; Fujihara, Tetsuaki

    2012-01-01

    Recent carbon-carbon bond forming reactions of carbon dioxide with alkenes, alkynes, dienes, aryl zinc compounds, aryl boronic esters, aryl halides, and arenes having acidic C-H bonds are reviewed in which transition-metal catalysts play an important role.

  4. Studies of beauty baryon decays to D0ph- and Λc+h- final states

    Science.gov (United States)

    Aaij, R.; Adeva, B.; Adinolfi, M.; Adrover, C.; Affolder, A.; Ajaltouni, Z.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; Anderlini, L.; Anderson, J.; Andreassen, R.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Aquines Gutierrez, O.; Archilli, F.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Bachmann, S.; Back, J. J.; Badalov, A.; Balagura, V.; Baldini, W.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Batozskaya, V.; Bauer, Th.; Bay, A.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Belogurov, S.; Belous, K.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Benton, J.; Berezhnoy, A.; Bernet, R.; Bettler, M.-O.; van Beuzekom, M.; Bien, A.; Bifani, S.; Bird, T.; Bizzeti, A.; Bjørnstad, P. M.; Blake, T.; Blanc, F.; Blouw, J.; Blusk, S.; Bocci, V.; Bondar, A.; Bondar, N.; Bonivento, W.; Borghi, S.; Borgia, A.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Brambach, T.; van den Brand, J.; Bressieux, J.; Brett, D.; Britsch, M.; Britton, T.; Brook, N. H.; Brown, H.; Bursche, A.; Busetto, G.; Buytaert, J.; Cadeddu, S.; Calabrese, R.; Callot, O.; Calvi, M.; Calvo Gomez, M.; Camboni, A.; Campana, P.; Campora Perez, D.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carranza-Mejia, H.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Castillo Garcia, L.; Cattaneo, M.; Cauet, Ch.; Cenci, R.; Charles, M.; Charpentier, Ph.; Cheung, S.-F.; Chiapolini, N.; Chrzaszcz, M.; Ciba, K.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Coca, C.; Coco, V.; Cogan, J.; Cogneras, E.; Collins, P.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coombes, M.; Coquereau, S.; Corti, G.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Cruz Torres, M.; Cunliffe, S.; Currie, R.; D'Ambrosio, C.; Dalseno, J.; David, P.; David, P. N. Y.; Davis, A.; De Bonis, I.; De Bruyn, K.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Silva, W.; De Simone, P.; Decamp, D.; Deckenhoff, M.; Del Buono, L.; Déléage, N.; Derkach, D.; Deschamps, O.; Dettori, F.; Di Canto, A.; Dijkstra, H.; Dogaru, M.; Donleavy, S.; Dordei, F.; Dorosz, P.; Dosil Suárez, A.; Dossett, D.; Dovbnya, A.; Dupertuis, F.; Durante, P.; Dzhelyadin, R.; Dziurda, A.; Dzyuba, A.; Easo, S.; Egede, U.; Egorychev, V.; Eidelman, S.; van Eijk, D.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; El Rifai, I.; Elsasser, Ch.; Falabella, A.; Färber, C.; Farinelli, C.; Farry, S.; Ferguson, D.; Fernandez Albor, V.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fiore, M.; Fiorini, M.; Fitzpatrick, C.; Fontana, M.; Fontanelli, F.; Forty, R.; Francisco, O.; Frank, M.; Frei, C.; Frosini, M.; Furfaro, E.; Gallas Torreira, A.; Galli, D.; Gandelman, M.; Gandini, P.; Gao, Y.; Garofoli, J.; Garosi, P.; Garra Tico, J.; Garrido, L.; Gaspar, C.; Gauld, R.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gibson, V.; Giubega, L.; Gligorov, V. V.; Göbel, C.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gordon, H.; Grabalosa Gándara, M.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graziani, G.; Grecu, A.; Greening, E.; Gregson, S.; Griffith, P.; Grillo, L.; Grünberg, O.; Gui, B.; Gushchin, E.; Guz, Yu.; Gys, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Hafkenscheid, T. W.; Haines, S. C.; Hall, S.; Hamilton, B.; Hampson, T.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Harrison, J.; Hartmann, T.; He, J.; Head, T.; Heijne, V.; Hennessy, K.; Henrard, P.; Hernando Morata, J. A.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hicks, E.; Hill, D.; Hoballah, M.; Hombach, C.; Hulsbergen, W.; Hunt, P.; Huse, T.; Hussain, N.; Hutchcroft, D.; Hynds, D.; Iakovenko, V.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jaeger, A.; Jans, E.; Jaton, P.; Jawahery, A.; Jing, F.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kaballo, M.; Kandybei, S.; Kanso, W.; Karacson, M.; Karbach, T. M.; Kenyon, I. R.; Ketel, T.; Khanji, B.; Klaver, S.; Kochebina, O.; Komarov, I.; Koopman, R. F.; Koppenburg, P.; Korolev, M.; Kozlinskiy, A.; Kravchuk, L.; Kreplin, K.; Kreps, M.; Krocker, G.; Krokovny, P.; Kruse, F.; Kucharczyk, M.; Kudryavtsev, V.; Kurek, K.; Kvaratskheliya, T.; La Thi, V. N.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lambert, D.; Lambert, R. W.; Lanciotti, E.; Lanfranchi, G.; Langenbruch, C.; Latham, T.; Lazzeroni, C.; Le Gac, R.; van Leerdam, J.; Lees, J.-P.; Lefèvre, R.; Leflat, A.; Lefrançois, J.; Leo, S.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, Y.; Li Gioi, L.; Liles, M.; Lindner, R.; Linn, C.; Lionetto, F.; Liu, B.; Liu, G.; Lohn, S.; Longstaff, I.; Lopes, J. H.; Lopez-March, N.; Lu, H.; Lucchesi, D.; Luisier, J.; Luo, H.; Luppi, E.; Lupton, O.; Machefert, F.; Machikhiliyan, I. V.; Maciuc, F.; Maev, O.; Malde, S.; Manca, G.; Mancinelli, G.; Maratas, J.; Marconi, U.; Marino, P.; Märki, R.; Marks, J.; Martellotti, G.; Martens, A.; Martín Sánchez, A.; Martinelli, M.; Martinez Santos, D.; Martins Tostes, D.; Martynov, A.; Massafferri, A.; Matev, R.; Mathe, Z.; Matteuzzi, C.; Maurice, E.; Mazurov, A.; McCann, M.; McCarthy, J.; McNab, A.; McNulty, R.; McSkelly, B.; Meadows, B.; Meier, F.; Meissner, M.; Merk, M.; Milanes, D. A.; Minard, M.-N.; Molina Rodriguez, J.; Monteil, S.; Moran, D.; Morawski, P.; Mordà, A.; Morello, M. J.; Mountain, R.; Mous, I.; Muheim, F.; Müller, K.; Muresan, R.; Muryn, B.; Muster, B.; Naik, P.; Nakada, T.; Nandakumar, R.; Nasteva, I.; Needham, M.; Neubert, S.; Neufeld, N.; Nguyen, A. D.; Nguyen, T. D.; Nguyen-Mau, C.; Nicol, M.; Niess, V.; Niet, R.; Nikitin, N.; Nikodem, T.; Nomerotski, A.; Novoselov, A.; Oblakowska-Mucha, A.; Obraztsov, V.; Oggero, S.; Ogilvy, S.; Okhrimenko, O.; Oldeman, R.; Onderwater, G.; Orlandea, M.; Otalora Goicochea, J. M.; Owen, P.; Oyanguren, A.; Pal, B. K.; Palano, A.; Palutan, M.; Panman, J.; Papanestis, A.; Pappagallo, M.; Pappalardo, L.; Parkes, C.; Parkinson, C. J.; Passaleva, G.; Patel, G. D.; Patel, M.; Patrignani, C.; Pavel-Nicorescu, C.; Pazos Alvarez, A.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perez Trigo, E.; Pérez-Calero Yzquierdo, A.; Perret, P.; Perrin-Terrin, M.; Pescatore, L.; Pesen, E.; Pessina, G.; Petridis, K.; Petrolini, A.; Picatoste Olloqui, E.; Pietrzyk, B.; Pilař, T.; Pinci, D.; Playfer, S.; Plo Casasus, M.; Polci, F.; Polok, G.; Poluektov, A.; Polycarpo, E.; Popov, A.; Popov, D.; Popovici, B.; Potterat, C.; Powell, A.; Prisciandaro, J.; Pritchard, A.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Punzi, G.; Qian, W.; Rachwal, B.; Rademacker, J. H.; Rakotomiaramanana, B.; Rangel, M. S.; Raniuk, I.; Rauschmayr, N.; Raven, G.; Redford, S.; Reichert, S.; Reid, M. M.; dos Reis, A. C.; Ricciardi, S.; Richards, A.; Rinnert, K.; Rives Molina, V.; Roa Romero, D. A.; Robbe, P.; Roberts, D. A.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Perez, P.; Roiser, S.; Romanovsky, V.; Romero Vidal, A.; Rotondo, M.; Rouvinet, J.; Ruf, T.; Ruffini, F.; Ruiz, H.; Ruiz Valls, P.; Sabatino, G.; Saborido Silva, J. J.; Sagidova, N.; Sail, P.; Saitta, B.; Salustino Guimaraes, V.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santovetti, E.; Sapunov, M.; Sarti, A.; Satriano, C.; Satta, A.; Savrie, M.; Savrina, D.; Schiller, M.; Schindler, H.; Schlupp, M.; Schmelling, M.; Schmidt, B.; Schneider, O.; Schopper, A.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Seco, M.; Semennikov, A.; Senderowska, K.; Sepp, I.; Serra, N.; Serrano, J.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, O.; Shevchenko, V.; Shires, A.; Silva Coutinho, R.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, N. A.; Smith, E.; Smith, E.; Smith, J.; Smith, M.; Sokoloff, M. D.; Soler, F. J. P.; Soomro, F.; Souza, D.; Souza De Paula, B.; Spaan, B.; Sparkes, A.; Spradlin, P.; Stagni, F.; Stahl, S.; Steinkamp, O.; Stevenson, S.; Stoica, S.; Stone, S.; Storaci, B.; Stracka, S.; Straticiuc, M.; Straumann, U.; Subbiah, V. K.; Sun, L.; Sutcliffe, W.; Swientek, S.; Syropoulos, V.; Szczekowski, M.; Szczypka, P.; Szilard, D.; Szumlak, T.; T'Jampens, S.; Teklishyn, M.; Tellarini, G.; Teodorescu, E.; Teubert, F.; Thomas, C.; Thomas, E.; van Tilburg, J.; Tisserand, V.; Tobin, M.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Topp-Joergensen, S.; Torr, N.; Tournefier, E.; Tourneur, S.; Tran, M. T.; Tresch, M.; Tsaregorodtsev, A.; Tsopelas, P.; Tuning, N.; Ubeda Garcia, M.; Ukleja, A.; Ustyuzhanin, A.; Uwer, U.; Vagnoni, V.; Valenti, G.; Vallier, A.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vázquez Sierra, C.; Vecchi, S.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Vesterinen, M.; Viaud, B.; Vieira, D.; Vilasis-Cardona, X.; Vollhardt, A.; Volyanskyy, D.; Voong, D.; Vorobyev, A.; Vorobyev, V.; Voß, C.; Voss, H.; de Vries, J. A.; Waldi, R.; Wallace, C.; Wallace, R.; Wandernoth, S.; Wang, J.; Ward, D. R.; Watson, N. K.; Webber, A. D.; Websdale, D.; Whitehead, M.; Wicht, J.; Wiechczynski, J.; Wiedner, D.; Wiggers, L.; Wilkinson, G.; Williams, M. P.; Williams, M.; Wilson, F. F.; Wimberley, J.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wright, S.; Wu, S.; Wyllie, K.; Xie, Y.; Xing, Z.; Yang, Z.; Yuan, X.; Yushchenko, O.; Zangoli, M.; Zavertyaev, M.; Zhang, F.; Zhang, L.; Zhang, W. C.; Zhang, Y.; Zhelezov, A.; Zhokhov, A.; Zhong, L.; Zvyagin, A.; LHCb Collaboration

    2014-02-01

    Decays of beauty baryons to the D0ph- and Λc+h- final states (where h indicates a pion or a kaon) are studied using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb detector. The Cabibbo-suppressed decays Λb0→D0pK- and Λb0→Λc+K- are observed, and their branching fractions are measured with respect to the decays Λb0→D0pπ- and Λb0→Λc+π-. In addition, the first observation is reported of the decay of the neutral beauty-strange baryon Ξb0 to the D0pK- final state, and a measurement of the Ξb0 mass is performed. Evidence of the Ξb0→Λc+K- decay is also reported.

  5. Transport Coefficients of Ar/C/H/O/N Systems Thermal Plasma at Atmospheric Pressure

    International Nuclear Information System (INIS)

    The transport coefficients of thermal plasma composed of Ar/C/H/O/N elements are presented in the temperature range from 1000 to 15000 K. Several chemical composition calculations with different proportions of the elements lead us to retain 35 major species. We have characterized 595 interactions the between these species and derived the collision integrals necessary for the calculation of transport coefficients by Chapman-Enskog method. The following approximation orders have been used: 3rd for electrical conductivity and electrons translation thermal conductivity, 2nd for heavy particles translation thermal conductivity and 1st for viscosity, reaction and internal thermal conductivity. The development of thermal plasma processes lead to the use of plasma gases or gases mixtures more and more complexes. If data concerning the transport coefficients of simple gases like argon, hydrogen, oxygen or nitrogen or some binary mixtures like argon-hydrogen, argon-oxygen or oxygen-nitrogen can be early found in literature, those concerning ternary mixtures or more are not available. Ar/H/O and N brought together and C is added permitting to take into account hydrocarbons. First ours results for simple gases or gases mixtures are compared with recently published data of the literature and finally we present the transport coefficients of oxygen-nitrogen-methane, and argon-steam mixtures.

  6. Thermal effects on the Ga+ ion beam induced structural modification of a-SiC:H

    International Nuclear Information System (INIS)

    The effects of implantation temperature and post-implantation thermal annealing on the Ga+ ion beam induced optical contrast formation in hydrogenated silicon-carbon alloy (a-SiC:H) films and underlying structural modifications have been studied. The optical contrast formed (between implanted and unimplanted regions of the film material) has been made use of in the form of optical pattern formation by computer-operated Ga+-focused ion beam. Possible applications of this effect in the area of submicron lithography and high-density optical data storage have been suggested with regard to the most widely spread focused micro-beam systems based on Ga+ liquid metal ion sources. The implanted samples were structurally analysed using vibrational spectroscopies, like Raman and infra-red (IR) spectroscopy, to define optimum implantation conditions. The precise role of implantation temperature effects, i.e. the target temperature during Ga+ ion irradiation, on the structural modification obtainable has been therefore a key part of this study. Appropriate post-implantation annealing treatments were also studied, since these are expected to offer further benefits in reducing the required ion dose and enhancing the optical contrast, thus increasing the cost-effectiveness of the method.

  7. Modification of Pyrrolo[2,3-d]pyrimidines by C-H Borylation Followed by Cross-Coupling or Other Transformations: Synthesis of 6,8-Disubstituted 7-Deazapurine Bases

    Czech Academy of Sciences Publication Activity Database

    Klečka, Martin; Poštová Slavětínská, Lenka; Hocek, Michal

    2015-01-01

    Roč. 2015, č. 36 (2015), s. 7943-7961. ISSN 1434-193X Institutional support: RVO:61388963 Keywords : synthetic methods * cross-coupling * C-H activation * nitrogen heterocycles * nucleobases * deazapurines Subject RIV: CC - Organic Chemistry Impact factor: 3.065, year: 2014

  8. Intramolecular Direct C-H Arylation Approach to Fused Purines. Synthesis of Purino[8,9-f]phenanthridines and 5,6-Dihydropurino[8,9-a]isoquinolines

    Czech Academy of Sciences Publication Activity Database

    Čerňa, Igor; Pohl, Radek; Klepetářová, Blanka; Hocek, Michal

    2010-01-01

    Roč. 75, č. 7 (2010), s. 2302-2308. ISSN 0022-3263 R&D Projects: GA MŠk(CZ) LC06077 Institutional research plan: CEZ:AV0Z40550506 Keywords : purines * cross-coupling * fused heterocycles * C-H activation Subject RIV: CC - Organic Chemistry Impact factor: 4.002, year: 2010

  9. Weak C-H acids as protonophores can carry hydrogen ions through lipid membranes and mitochondria: a case of o-carborane.

    Science.gov (United States)

    Rokitskaya, Tatyana I; Khailova, Ljudmila S; Makarenkov, Anton V; Ol'shevskaya, Valentina A; Kalinin, Valery N; Antonenko, Yuri N

    2016-06-28

    ortho-Carborane (1,2-C2B10H12) was found to be a carrier of protons in both mitochondrial and artificial lipid membranes, suggesting that this dicarborane can reversibly release hydrogen ions and diffuse through the membranes in neutral and anionic forms. Similar to conventional uncouplers (e.g. 2,4-dinitrophenol), o-carborane stimulated mitochondrial respiration and decreased the membrane potential at concentrations of tens of micromoles. Protonophoric activity of o-carborane was observed both by a fluorometric assay using pyranine-loaded liposomes and electrical current measurements across planar lipid bilayers. Substantial contribution of the proton flux to the o-carborane-mediated current was proved by a shift of the zero current voltage upon imposing a pH gradient across the membrane. Meta-carborane (1,7-C2B10H12) lacked the protonophoric activity in line with its reduced C-H acidity. The results suggest that weak C-H acids can exhibit protonophoric activity in the biological environment. The finding of a new class of protonophoric compounds is of substantial interest due to promising anti-obesity and anti-diabetic properties of uncouplers. PMID:27265316

  10. Cross Shear Roll Bonding

    DEFF Research Database (Denmark)

    Bay, Niels; Bjerregaard, Henrik; Petersen, Søren. B;

    1994-01-01

    The present paper describes an investigation of roll bonding an AlZn alloy to mild steel. Application of cross shear roll bonding, where the two equal sized rolls run with different peripheral speed, is shown to give better bond strength than conventional roll bonding. Improvements of up to 20......-23% in bond strength are found and full bond strength is obtained at a reduction of 50% whereas 65% is required in case of conventional roll bonding. Pseudo cross shear roll bonding, where the cross shear effect is obtained by running two equal sized rolls with different speed, gives the same results....

  11. Structural and mechanical properties of nc-TiC/a-C:H nanocomposite film prepared by dual plasma technique

    International Nuclear Information System (INIS)

    Nanocomposite nc-TiC/a-C:H film, with an unusual combination of superhardness, high elastic modulus and high elastic recovery, are prepared by using the dual plasma technique. The effects of the filter coil current on the compositional, structural and mechanical properties of the nc-TiC/a-C:H films have been investigated. X-ray photoelectron spectroscopy (XPS) and Raman analyses show that deposition rate, composition and nanostructure of the nc-TiC/a-C:H films could be changed by varying the filter coil current. Fortunately, by selecting the proper value for the filter coil current, 2.5 A, one could remarkably enhance mechanical properties of films such as the superhardness (66.4 GPa), the high elastic modulus (510 GPa) and the high elastic recovery (83.3%)

  12. Wire bonding in microelectronics

    CERN Document Server

    Harman, George G

    2010-01-01

    Wire Bonding in Microelectronics, Third Edition, has been thoroughly revised to help you meet the challenges of today's small-scale and fine-pitch microelectronics. This authoritative guide covers every aspect of designing, manufacturing, and evaluating wire bonds engineered with cutting-edge techniques. In addition to gaining a full grasp of bonding technology, you'll learn how to create reliable bonds at exceedingly high yields, test wire bonds, solve common bonding problems, implement molecular cleaning methods, and much more. Coverage includes: Ultrasonic bonding systems and technologies, including high-frequency systems Bonding wire metallurgy and characteristics, including copper wire Wire bond testing Gold-aluminum intermetallic compounds and other interface reactions Gold and nickel-based bond pad plating materials and problems Cleaning to improve bondability and reliability Mechanical problems in wire bonding High-yield, fine-pitch, specialized-looping, soft-substrate, and extreme-temperature wire bo...

  13. Paramagnetic states in {mu}c-SiC:H thin films prepared by Hot-Wire CVD at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Lihong; Astakhov, Oleksandr; Carius, Reinhard; Finger, Friedhelm [IEF-5 Photovoltaik, Forschungszentrum Juelich (Germany); Chen, Tao [IEF-5 Photovoltaik, Forschungszentrum Juelich (Germany); State Key Lab of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang (China); Wang, Haiyan [IEF-5 Photovoltaik, Forschungszentrum Juelich (Germany); School of Physical Engineering, Zhengzhou University, Henan (China); Stutzmann, Martin [Walter Schottky Institut, Technische Universitaet Muenchen, Garching (Germany)

    2010-04-15

    The relationship between the structure, electrical conductivity and paramagnetic states in microcrystalline hydrogenated silicon carbide ({mu}c-SiC:H) prepared by HWCVD is investigated. The study includes undoped and Al-doped (p -type) {mu}c-SiC:H of different crystalline volume fraction (I{sub C}{sup IR}). High densities of paramagnetic states are observed in undoped material over a wide range of crystallinity whereas the conductivity increases by 10 orders of magnitude up to 10{sup -2} S/cm as the material becomes more crystalline. This dramatic increase of the conductivity attributed to unintentional n -type doping has a clear effect on the ESR spectrum which changes from a broad featureless resonance in the low crystallinity material to a sharp line with a pair of distinct satellites in highly crystalline n -type {mu}c-SiC:H. Al-doping results in compensation and then effective p -type doping in {mu}c-SiC:H at higher doping concentration. Al-doping seems to hinder the crystalline growth in p -type {mu}c-SiC:H. For I{sub C}{sup IR} {<=} 20% the spin resonance signature is a broad (peak-to-peak linewidth {delta}H{sub pp}{approx}30 G) featureless slightly asymmetric line at g {approx} 2.01. The nature and behavior of the ESR spectra in different types of {mu}c-SiC:H are investigated with respect to the Fermi level position and crystalline volume fraction (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Reactions of [Cu(X)(BPEP-Ph)] (X = PF6, SbF6) with silyl compounds. Cooperative bond activation involving non-coordinating anions.

    Science.gov (United States)

    Nakajima, Yumiko; Tsuchimoto, Takahiro; Chang, Yung-Hung; Takeuchi, Katsuhiko; Ozawa, Fumiyuki

    2016-02-01

    Bond activation of silyl compounds, assisted by the cooperative action of non-coordinating anions, is achieved using Cu(I) complexes coordinated with a PNP-pincer type phosphaalkene ligand, [Cu(X)(BPEP-Ph)] (X = PF6 (1a), SbF6 (1b); BPEP-Ph = 2,6-bis[1-phenyl-2-(2,4,6-tri-tert-butylphenyl)-2-phosphaethenyl]pyridine). Complexes 1a and 1b react with Me3SiCN to form Me3SiF and Cu(i) cyanide complexes of the formula [Cu(CN-EF5)(BPEP-Ph)] (E = P (2a), Sb (2b)), in which the CN ligand is associated with the EF5 group arising from EF6(-). Formation of the intermediary isonitrile complex [Cu(CNSiMe3)(BPEP-Ph)](+)SbF6(-) (3b) is confirmed by its isolation. Thus, a two-step reaction process involving coordination of Me3SiCN, followed by nucleophilic attack of SbF6(-) on the silicon atom of 3b is established for the conversion of 1b to 2b. Complex 1b cleaves the H-Si bond of PhMe2SiH as well. The isolation and structural identification of [Cu(BPEP-Ph)](+)BAr(F)4(-) (1c) (BAr(F)4 = B{3,5-(CF3)2C6H3}4) as a rare example of a T-shaped, three-coordinated Cu(i) complex is reported. PMID:26455594

  15. Influence of energetic ion bombardment on W-C: H coatings deposited with W and WC targets

    OpenAIRE

    Strondl, C.; Carvalho, NM; de Hosson, JTM; Krug, TG

    2005-01-01

    Tungsten containing diamond-like carbon (W-C:H) coatings have been produced by unbalanced magnetron sputtering using two different target materials. In the first series of coatings, W has been used as target material, and in the second series, WC has been used as target material. In both series of W-C:H coatings, the deposition energy has been varied by changing the ion current density and the bias voltage on the substrate. The aim of the investigation has been to study the changes in the mic...

  16. Experimentally calibrated computational chemistry of tryptophan hydroxylase: Trans influence, hydrogen-bonding, and 18-electron rule govern O-2-activation

    DEFF Research Database (Denmark)

    Haahr, Lærke Tvedebrink; Kepp, Kasper Planeta; Boesen, Jane;

    2010-01-01

    Insight into the nature of oxygen activation in tryptophan hydroxylase has been obtained from density functional computations. Conformations of O2-bound intermediates have been studied with oxygen trans to glutamate and histidine, respectively. An O2-adduct with O2 trans to histidine (Ohis) and a...... peroxo intermediate with peroxide trans to glutamate (Pglu) were found to be consistent (0.57–0.59 mm/s) with experimental Mössbauer isomer shifts (0.55 mm/s) and had low computed free energies. The weaker trans influence of histidine is shown to give rise to a bent O2 coordination mode with O2 pointing...

  17. Comparative anti-inflammatory activities of curcumin and tetrahydrocurcumin based on the phenolic O-H bond dissociation enthalpy, ionization potential and quantum chemical descriptor.

    Science.gov (United States)

    Murakami, Yukio; Ishii, Hiroaki; Takada, Naoki; Tanaka, Shoji; Machino, Mamoru; Ito, Shigeru; Fujisawa, Seiichiro

    2008-01-01

    Curcumin and its reduced derivative tetrahydrocurcumin have been shown to exhibit chemopreventive activity. Cyclooxygenase-2 (COX-2) inhibition in lipopolysaccharide (LPS)- or Porphyromonas gingivalis fimbria-stimulated RAW 264.7 cells was investigated using Northern blot analysis. The fimbria-stimulated expression of the COX-2 gene was inhibited by curcumin but not by tetrahydrocurcumin. LPS-stimulated COX-2 gene expression was completely inhibited by curcumin, but an increase in the concentration of tetrahydrocurcumin did not cause complete inhibition of COX-2 expression. The inhibitory effect of curcumin on nuclear factor kappa B (NF-kappaB) activation in the cells was clearly observed, but that of tetrahydrocurcumin was incomplete even at a concentration of 20 microM. To explain the difference in effect between the two compounds, analysis of the frontier orbital was performed using ab initio 6-31G* wave function. The calculated chemical hardness (eta) for curcumin was clearly smaller, whereas its electronegativity (chi) and electrophilicity (omega) were clearly greater than the corresponding values for the curcumin-related compounds tetrahydrocurcumin, isoeugenol and eugenol. This suggested that the anti-inflammatory activities of curcumin may be related to eta-, chi- and/or omega-controlled enzymes. In addition, the bond dissociation enthalpy (BDE) of the phenolic OH was calculated using the density function theory (DFT)/B3LY. The total BDE values of curcumin and tetrahydrocurcumin were almost identical, but the BDE of one-electron oxidation and ionization potential (IP) for curcumin were lower than those for tetrahydrocurcumin, suggesting the highly pro-oxidative activity of curcumin. Curcumin has both oxidant and antioxidant properties. A causal link between the anti-inflammatory activities and molecular properties of phenolic antioxidants is suggested. PMID:18507010

  18. On Bond Portfolio Management

    OpenAIRE

    Vladislav Kargin

    2002-01-01

    This paper describes a new method of bond portfolio optimization based on stochastic string models of correlation structure in bond returns. The paper shows how to approximate correlation function of bond returns, compute the optimal portfolio allocation using Wiener-Hopf factorization, and check whether a collection of bonds presents arbitrage opportunities.

  19. Positioning a Carbon-Fluorine Bond over the π Cloud of an Aromatic Ring: A Different Type of Arene Activation.

    Science.gov (United States)

    Holl, Maxwell Gargiulo; Struble, Mark D; Singal, Prakhar; Siegler, Maxime A; Lectka, Thomas

    2016-07-11

    It is known that the fluoro group has only a small effect on the rates of electrophilic aromatic substitutions. Imagine instead a carbon-fluorine (C-F) bond positioned tightly over the π cloud of an aryl ring-such an orthogonal, noncovalent arrangement could instead stabilize a positively charged arene intermediate or transition state, giving rise to novel electrophilic aromatic substitution chemistry. Herein, we report the synthesis and study of molecule 1, containing a rigid C-F⋅⋅⋅Ar interaction that plays a prominent role in both its reaction chemistry and spectroscopy. For example, we established that the C-F⋅⋅⋅Ar interaction can bring about a >1500 fold increase in the relative rate of an aromatic nitration reaction, affording functionalization on the activated ring exclusively. Overall, these results establish fluoro as a through-space directing/activating group that complements the traditional role of fluorine as a slightly deactivating aryl substituent in nitrations. PMID:27145463

  20. Multicenter bonds, bond valence and bond charge apportion

    International Nuclear Information System (INIS)

    In the same way that the valence of an atom issues from the definition of bond index, we shoe here that the three-center bond index lends itself to the definition of a bond valence. Within the charge of a bond, we show that its self-charge (i.e., the amount of electron kept by the atoms involved in the bond) is parted in a such a way that the more electronegative atom tends to allot more electronic charge than the other atom. We give examples of these quantities and discuss the results for different kinds of chemical systems. We also show some results for four-center indices and report six-center indices for hexagonal rings. (author). 54 refs., 4 figs., 8 tabs

  1. NUV/VIS sensitive multicolor thin film detector based on a-SiC:H/a-Si:H/μc-SiGeC:H alloys with an in-situ structured transparent conductive oxide front contact without etching

    International Nuclear Information System (INIS)

    An innovative family of hydrogenated amorphous silicon (a-Si:H) multicolor p–i–n photo sensors, sensitive in the VIS and the near UV spectrum, is presented. Typical values of the quantum efficiency at 350 nm and 580 nm are 5.4% and 54.7%, respectively, with − 0.4 V and − 12 V bias. Electro-optical studies were performed to explore the effect of combining linearly graded a-SiGe:H/μc-SiGeC:H layers with linearly graded a‐SiC:H-layers. The devices presented additionally contain a buried a-Si:H region. Low-reflective aluminum doped zinc oxide (ZnO:Al) back contacts improve the spectral color separation. μτ-products and absorption coefficients of graded absorbers were determined. Discrete absorbers were substituted by a linear graded a-SiC:H absorption zone in the top structure, an interior a-Si:H region and a graded a-SiGe:H/a-SiC:H alloy combination. In this paper we demonstrate a reduction of interference fringes and operation at low bias voltages, combined with a highly precise adjustment of the spectral sensitivity, even in the near UV-spectrum. The device dynamic range exceeds 50 dB at 1000 lx white-light illumination. As the deposited upper layers adopt the roughness of μc-SiGeC:H clusters in the rear absorber, we present an in-situ structured front contact without etching ZnO:Al. - Highlights: ► Structuring zinc oxide anode without etching ► UV/VIS amorphous silicon sensor ► Microcrystalline narrow gap absorber ► Significant color separation improvement

  2. NUV/VIS sensitive multicolor thin film detector based on a-SiC:H/a-Si:H/{mu}c-SiGeC:H alloys with an in-situ structured transparent conductive oxide front contact without etching

    Energy Technology Data Exchange (ETDEWEB)

    Bablich, A., E-mail: andreas.bablich@uni-siegen.de; Boehm, M., E-mail: m.boehm@t-online.de

    2012-10-01

    An innovative family of hydrogenated amorphous silicon (a-Si:H) multicolor p-i-n photo sensors, sensitive in the VIS and the near UV spectrum, is presented. Typical values of the quantum efficiency at 350 nm and 580 nm are 5.4% and 54.7%, respectively, with - 0.4 V and - 12 V bias. Electro-optical studies were performed to explore the effect of combining linearly graded a-SiGe:H/{mu}c-SiGeC:H layers with linearly graded a-SiC:H-layers. The devices presented additionally contain a buried a-Si:H region. Low-reflective aluminum doped zinc oxide (ZnO:Al) back contacts improve the spectral color separation. {mu}{tau}-products and absorption coefficients of graded absorbers were determined. Discrete absorbers were substituted by a linear graded a-SiC:H absorption zone in the top structure, an interior a-Si:H region and a graded a-SiGe:H/a-SiC:H alloy combination. In this paper we demonstrate a reduction of interference fringes and operation at low bias voltages, combined with a highly precise adjustment of the spectral sensitivity, even in the near UV-spectrum. The device dynamic range exceeds 50 dB at 1000 lx white-light illumination. As the deposited upper layers adopt the roughness of {mu}c-SiGeC:H clusters in the rear absorber, we present an in-situ structured front contact without etching ZnO:Al. - Highlights: Black-Right-Pointing-Pointer Structuring zinc oxide anode without etching Black-Right-Pointing-Pointer UV/VIS amorphous silicon sensor Black-Right-Pointing-Pointer Microcrystalline narrow gap absorber Black-Right-Pointing-Pointer Significant color separation improvement.

  3. Tribological Performance of Hydrogenated Amorphous Carbon (a-C: H DLC Coating when Lubricated with Biodegradable Vegetal Canola Oil

    Directory of Open Access Journals (Sweden)

    H.M. Mobarak

    2014-06-01

    Full Text Available Increasing environmental awareness and demands for lowering energy consumptions are strong driving forces behind the development of the vehicles of tomorrow. Without the advances of lubricant chemistry and adequate lubricant formulation, expansion of modern engines would not have been possible. Considering environmental awareness factors as compared to mineral oils, vegetal oil based biolubricants are renewable, biodegradable, non-toxic and have a least amount of greenhouse gases. Furthermore, improvement in engine performance and transmission components, which were impossible to achieve by applying only lubricants design, is now possible through diamond like carbon (DLC coatings. DLC coatings exhibit brilliant tribological properties, such as good wear resistance and low friction. In this regard, tribological performance of a-C: H DLC coating when lubricated with Canola vegetal oil has been investigated by the help of a ball-on-flat geometry. Experimental results demonstrated that the a-C: H DLC coating exhibited better performance with Canola oil in terms of friction and wear as compared to the uncoated materials. Large amount of polar components in the Canola oil significantly improved the tribological properties of the a-C:H coating. Thus, usage of a-C: H DLC coating with Canola oil in the long run may have a positive impact on engine life.

  4. Spin-forbidden and spin-allowed cyclopropenone (c-H2C3O) formation in interstellar medium

    International Nuclear Information System (INIS)

    Three proposed mechanisms of cyclopropenone (c-H2C3O) formation from neutral species are studied using high-level electronic structure methods in combination with nonadiabatic transition state and collision theories to deduce the likelihood of each reaction mechanism under interstellar conditions. The spin-forbidden reaction involving the singlet electronic state of cyclopenylidene (c-C3H2) and the triplet state of atomic oxygen is studied using nonadiabatic transition state theory to predict the rate constant for c-H2C3O formation. The spin-allowed reactions of c-C3H2 with molecular oxygen and acetylene with carbon monoxide were also investigated. The reaction involving the ground electronic states of acetylene and carbon monoxide has a very large reaction barrier and is unlikely to contribute to c-H2C3O formation in interstellar medium. The spin-forbidden reaction of c-C3H2 with atomic oxygen, despite the high probability of nonadiabatic transition between the triplet and singlet states, was found to have a very small rate constant due to the presence of a small (3.8 kcal mol–1) reaction barrier. In contrast, the spin-allowed reaction between c-C3H2 and molecular oxygen is found to be barrierless, and therefore can be an important path to the formation of c-H2C3O molecule in interstellar environment.

  5. An overview on the applications of `Doyle catalysts’ in asymmetric cyclopropanation, cyclopropenation and C-H insertion reactions

    Indian Academy of Sciences (India)

    Thomas J Colacot

    2000-06-01

    The chiral dirhodium(II) carboxamidates are a unique class of chiral catalysts useful for asymmetric inter- and intramolecular cyclopropanation, cyclopropenation and C-H insertion reactions with excellent enantioselectivities. The broad applications of these catalysts in organic syntheses are briefly reviewed.

  6. Simulation of the Efficiency of a-SiC:H/a-Si:H Tandem Multilayer Solar Cells

    CERN Document Server

    Muminov, Khikmat Kh

    2016-01-01

    In this paper we carried out theoretical study of the general issues related to the efficiency of SiC:H/a-Si:H single- and multi-junction tandem solar cells. Implementation of numerical simulations by the use of AMPS-1D program of one-dimensional analysis of microelectronic and photonic structures for the analysis of hydrogenated silicon solar cells allowed us to formulate the optimal design of new kind of multi-junction tandem solar cells, providing its most efficient operation. The numerical analysis of SiC:H/a-Si:H single-junction solar cell whith doped i-layer used as the intermediate absorbing layer (a -Si: H) placed between layers of p-type (a-SiC: H) and n-type (a-Si: H) has been conducted. It has been established that after optimizing the solar cell parameters its highest efficiency of 19.62% is achieved at 500 nm thickness of i-layer. The optimization of the newly developed multi-junction structure of a-SiC:H/a-Si:H tandem solar cell has been conducted. It has been shown numerically that its highest ...

  7. Density functional theory study of O-H and C-H bond scission of methanol catalyzed by a chemisorbed oxygen layer on Cu(111)

    Science.gov (United States)

    Li, Jonathan; Zhou, Guangwen

    2016-04-01

    Using the density-functional theory within the generalized gradient approximation, we have studied the partial oxidation of methanol on a Cu(111) surface covered with a chemisorbed oxygen layer that resembles a Cu2O layer. Adsorption energies and geometries were computed for methanol, methoxy, hydroxymethyl and formaldehyde on both clean Cu(111) and Cu2O/Cu(111) and electronic structures were computed for the reaction intermediates on Cu2O/Cu(111). We also calculated the energy barrier for partial oxidation of methanol to formaldehyde on Cu2O/Cu(111). These results show that the Cu2O monolayer slightly lowers the stability of each of the surface adsorbates and the oxygen strongly promotes hydrogen dissociation by lowering the energy barrier of methanol decomposition and causing the spontaneous dissociation of methanol into methoxy.

  8. Magnetism, chemical bonding and hyperfine properties in the nanoscale antiferromagnet [Fe(O Me)2(O2 C C H2 Cl)]10

    International Nuclear Information System (INIS)

    The electronic and magnetic properties of the nanometer-size antiferromagnet (the ferric wheel molecule) are investigated with the first-principles spin-polarized Discrete Variational Method, in the framework of Density Functional theory. Magnetic moments, densities of the states and charge and spin-density maps are obtained. The Moessbauer hyperfine parameters Isomer shift, Quadrupole Splitting and Hyperfine Field are obtained from the calculations and compared to reported experimental values when available. (author). 33 refs., 8 figs., 4 tabs

  9. A theoretical study of the effects of polar substitution on the activation barriers for internal rotation around the C-N bond in p-substituted nitrosobenzenes: comparison of DFT and MP2 calculations

    OpenAIRE

    PİRİNÇÇİOĞLU, Şafak ÖZHAN KOCAKAYA and Necmettin

    2010-01-01

    The activation barriers for internal rotation around the C-N bond in p-substituted nitrosobenzenes were calculated using the density functional theory (DFT) and second-order Møller-Plesset (MP2) methods with the 6-31+g(d) basis set. The polarisable continuum model (PCM) was used to model the solvent effect. An explicit water molecule was also introduced to form a hydrogen bond with the nitrosogroup and its effect on the barrier was studied by DFT. The barriers were well-correlated wi...

  10. Development of Blocked-Impurity-Band-Type Ge Detectors Fabricated with the Surface-Activated Wafer Bonding Method for Far-Infrared Astronomy

    Science.gov (United States)

    Hanaoka, M.; Kaneda, H.; Oyabu, S.; Yamagishi, M.; Hattori, Y.; Ukai, S.; Shichi, K.; Wada, T.; Suzuki, T.; Watanabe, K.; Nagase, K.; Baba, S.; Kochi, C.

    2016-07-01

    We report the current status of the development of our new detectors for far-infrared (FIR) astronomy. We develop Blocked-Impurity-Band (BIB)-type Ge detectors to realize large-format compact arrays covering a wide FIR wavelength range up to 200 \\upmu m. We fabricated Ge junction devices of different physical parameters with a BIB-type structure, using the room temperature, surface-activated wafer bonding (SAB) method. We measured the absolute responsivity and the spectral response curve of each device at low temperatures, using an internal blackbody source in a cryostat and a Fourier transform spectrometer, respectively. The results show that the SAB Ge junction devices have significantly higher absolute responsivities and longer cut-off wavelengths of the spectral response than the conventional bulk Ge:Ga device. Based upon the results, we discuss the optimum parameters of SAB Ge junction devices for FIR detectors. We conclude that SAB Ge junction devices possess a promising applicability to next-generation FIR detectors covering wavelengths up to ˜ 200 \\upmu m with high responsivity. As a next step, we plan to fabricate a BIB-type Ge array device in combination with a low-power cryogenic readout integrated circuit.

  11. Acetaldehyde partial oxidation on the Au(111) model catalyst surface: C-C bond activation and formation of methyl acetate as an oxidative coupling product

    Science.gov (United States)

    Karatok, Mustafa; Vovk, Evgeny I.; Shah, Asad A.; Turksoy, Abdurrahman; Ozensoy, Emrah

    2015-11-01

    Partial oxidation of acetaldehyde (CH3CHO) on the oxygen pre-covered Au(111) single crystal model catalyst was investigated via Temperature Programmed Desorption (TPD) and Temperature Programmed Reaction Spectroscopy (TPRS) techniques, where ozone (O3) was utilized as the oxygen delivery agent providing atomic oxygen to the reacting surface. We show that for low exposures of O3 and small surface oxygen coverages, two partial oxidation products namely, methyl acetate (CH3COOCH3) and acetic acid (CH3COOH) can be generated without the formation of significant quantities of carbon dioxide. The formation of methyl acetate as the oxidative coupling reaction product implies that oxygen pre-covered Au(111) single crystal model catalyst surface can activate C-C bonds. In addition to the generation of these products; indications of the polymerization of acetaldehyde on the gold surface were also observed as an additional reaction route competing with the partial and total oxidation pathways. The interplay between the partial oxidation, total oxidation and polymerization pathways reveals the complex catalytic chemistry associated with the interaction between the acetaldehyde and atomic oxygen on catalytic gold surfaces.

  12. Hydrogen bonded supramolecular structures

    CERN Document Server

    Li, Zhanting

    2015-01-01

    This book covers the advances in the studies of hydrogen-bonding-driven supramolecular systems  made over the past decade. It is divided into four parts, with the first introducing the basics of hydrogen bonding and important hydrogen bonding patterns in solution as well as in the solid state. The second part covers molecular recognition and supramolecular structures driven by hydrogen bonding. The third part introduces the formation of hollow and giant macrocycles directed by hydrogen bonding, while the last part summarizes hydrogen bonded supramolecular polymers. This book is designed to b

  13. Microstructure of a-C:H films prepared on a microtrench and analysis of ions and radicals behavior

    International Nuclear Information System (INIS)

    Amorphous carbon films (a-C:H) were prepared on a microtrench (4-μm pitch and 4-μm depth), and the uniformity of film thickness and microstructure of the films on the top, sidewall, and bottom surfaces of the microtrench were evaluated by scanning electron microscopy and Raman spectroscopy. The a-C:H films were prepared by bipolar-type plasma based ion implantation and deposition (bipolar PBII&D), and the negative pulse voltage, which is the main parameter dominating the film structure, was changed from −1.0 to −15 kV. Moreover, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision (PIC-MCC) and Direct Simulation Monte Carlo (DSMC) to investigate the coating mechanism for the microtrench. The results reveal that the thickness uniformity of a-C:H films improves with decreasing negative pulse voltage due to the decreasing inertia of incoming ions from the trench mouth, although the film thickness on the sidewall tends to be much smaller than that on the top and bottom surfaces of the trench. The normalized flux and the film thickness show similar behavior, i.e., the normalized flux or thickness at the bottom surface increases at low negative pulse voltages and then saturates at a certain value, whereas at the sidewall it monotonically decreases with increasing negative voltage. The microstructure of a-C:H films on the sidewall surface is very different from that on the top and bottom surfaces. The film structure at a low negative pulse voltage shifts to more of a polymer-like carbon (PLC) structure due to the lower incident energy of ions. Although the radical flux on the sidewall increases slightly, the overall film structure is not significantly changed because this film formation at a low negative voltage is originally dominated by radicals. On the other hand, the flux of radicals is dominant on the sidewall in the case of high negative pulse voltage, resulting in a

  14. Hard TiCx/SiC/a-C:H nanocomposite thin films using pulsed high energy density plasma focus device

    International Nuclear Information System (INIS)

    Highlights: •The energetic ions and electron beams are used to synthesize TiCx/SiC/a-C:H films. •As-deposited crystalline and hard nanocomposite TiCx/SiC/a-C:H films are synthesized. •Very high average deposition rates of 68 nm/shot are achieved using dense plasma focus. •The maximum hardness of 22 GPa is achieved at the surface of the film. -- Abstract: Thin films of TiCx/SiC/a-C:H were synthesized on Si substrates using a complex mix of high energy density plasmas and instability accelerated energetic ions of filling gas species, emanated from hot and dense pinched plasma column, in dense plasma focus device. The conventional hollow copper anode of Mather type plasma focus device was replaced by solid titanium anode for synthesis of TiCx/SiC/a-C:H nanocomposite thin films using CH4:Ar admixture of (1:9, 3:7 and 5:5) for fixed 20 focus shots as well as with different number of focus shots with fixed CH4:Ar admixture ratio 3:7. XRD results showed the formation of crystalline TiCx/SiC phases for thin film synthesized using different number of focus shots with CH4:Ar admixture ratio fixed at 3:7. SEM results showed that the synthesized thin films consist of nanoparticle agglomerates and the size of agglomerates depended on the CH4:Ar admixture ratio as well as on the number of focus shots. Raman analysis showed the formation of polycrystalline/amorphous Si, SiC and a-C for different CH4:Ar ratio as well as for different number of focus shots. The XPS analysis confirmed the formation of TiCx/SiC/a-C:H composite thin film. Nanoindentation results showed that the hardness and elastic modulus values of composite thin films increased with increasing number of focus shots. Maximum values of hardness and elastic modulus at the surface of the composite thin film were found to be about 22 and 305 GPa, respectively for 30 focus shots confirming the successful synthesis of hard composite TiCx/SiC/a-C:H coatings

  15. Microstructure of a-C:H films prepared on a microtrench and analysis of ions and radicals behavior

    Energy Technology Data Exchange (ETDEWEB)

    Hirata, Yuki; Choi, Junho, E-mail: choi@mech.t.u-tokyo.ac.jp [Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2015-08-28

    Amorphous carbon films (a-C:H) were prepared on a microtrench (4-μm pitch and 4-μm depth), and the uniformity of film thickness and microstructure of the films on the top, sidewall, and bottom surfaces of the microtrench were evaluated by scanning electron microscopy and Raman spectroscopy. The a-C:H films were prepared by bipolar-type plasma based ion implantation and deposition (bipolar PBII&D), and the negative pulse voltage, which is the main parameter dominating the film structure, was changed from −1.0 to −15 kV. Moreover, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision (PIC-MCC) and Direct Simulation Monte Carlo (DSMC) to investigate the coating mechanism for the microtrench. The results reveal that the thickness uniformity of a-C:H films improves with decreasing negative pulse voltage due to the decreasing inertia of incoming ions from the trench mouth, although the film thickness on the sidewall tends to be much smaller than that on the top and bottom surfaces of the trench. The normalized flux and the film thickness show similar behavior, i.e., the normalized flux or thickness at the bottom surface increases at low negative pulse voltages and then saturates at a certain value, whereas at the sidewall it monotonically decreases with increasing negative voltage. The microstructure of a-C:H films on the sidewall surface is very different from that on the top and bottom surfaces. The film structure at a low negative pulse voltage shifts to more of a polymer-like carbon (PLC) structure due to the lower incident energy of ions. Although the radical flux on the sidewall increases slightly, the overall film structure is not significantly changed because this film formation at a low negative voltage is originally dominated by radicals. On the other hand, the flux of radicals is dominant on the sidewall in the case of high negative pulse voltage, resulting in a

  16. Molecular Dynamics Study of Twister Ribozyme: Role of Mg(2+) Ions and the Hydrogen-Bonding Network in the Active Site.

    Science.gov (United States)

    Ucisik, Melek N; Bevilacqua, Philip C; Hammes-Schiffer, Sharon

    2016-07-12

    The recently discovered twister ribozyme is thought to utilize general acid-base catalysis in its self-cleavage mechanism, but the roles of nucleobases and metal ions in the mechanism are unclear. Herein, molecular dynamics simulations of the env22 twister ribozyme are performed to elucidate the structural and equilibrium dynamical properties, as well as to examine the role of Mg(2+) ions and possible candidates for the general base and acid in the self-cleavage mechanism. The active site region and the ends of the pseudoknots were found to be less mobile than other regions of the ribozyme, most likely providing structural stability and possibly facilitating catalysis. A purported catalytic Mg(2+) ion and the closest neighboring Mg(2+) ion remained chelated and relatively immobile throughout the microsecond trajectories, although removal of these Mg(2+) ions did not lead to any significant changes in the structure or equilibrium motions of the ribozyme on the microsecond time scale. In addition, a third metal ion, a Na(+) ion remained close to A1(O5'), the leaving group atom, during the majority of the microsecond trajectories, suggesting that it might stabilize the negative charge on A1(O5') during self-cleavage. The locations of these cations and their interactions with key nucleotides in the active site suggest that they may be catalytically relevant. The P1 stem is partially melted at its top and bottom in the crystal structure and further unwinds in the trajectories. The simulations also revealed an interconnected network comprised of hydrogen-bonding and π-stacking interactions that create a relatively rigid network around the self-cleavage site. The nucleotides involved in this network are among the highly conserved nucleotides in twister ribozymes, suggesting that this interaction network may be important to structure and function. PMID:27295275

  17. Deposition and characterisation of multilayer hard coatings. Ti/TiN delta/TiC sub x N sub y /(TiC) a-C H/(Ti) a-C H

    CERN Document Server

    Burinprakhon, T

    2001-01-01

    mixture. The top layer (Ti) a-C:H was found to contain approximately 10 atomic % nitrogen, due to N sub 2 contamination during deposition caused by low conductance of N sub 2 through the nominally closed valve of the mass flow controller. The change of the CH sub 4 concentration during deposition of the top layer (Ti) a-C:H, however, showed a strong influence on the hydrogen content. The comparison of the fluorescence background of the Raman spectra revealed that hydrogen-less (Ti) a-C:H was deposited at a CH sub 4 concentration of less than 50 % flow rate in Ar. The hardness and adhesion of the multilayer coated titanium substrates were assessed by using microindentation hardness and scratch tests, respectively. A simple hardness model containing parameters that assess the contributions from the coating and the substrate to the measured hardness was developed to describe hardness variation as a function of indentation size. This model allowed the determination of a coating hardness and an effective substrate...

  18. Control of Reactivity and Regioselectivity for On-Surface Dehydrogenative Aryl-Aryl Bond Formation.

    Science.gov (United States)

    Kocić, Nemanja; Liu, Xunshan; Chen, Songjie; Decurtins, Silvio; Krejčí, Ondřej; Jelínek, Pavel; Repp, Jascha; Liu, Shi-Xia

    2016-05-01

    Regioselectivity is of fundamental importance in chemical synthesis. Although many concepts for site-selective reactions are well established for solution chemistry, it is not a priori clear whether they can easily be transferred to reactions taking place on a metal surface. A metal will fix the chemical potential of the electrons and perturb the electronic states of the reactants because of hybridization. Additionally, techniques to characterize chemical reactions in solution are generally not applicable to on-surface reactions. Only recent developments in resolving chemical structures by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) paved the way for identifying individual reaction products on surfaces. Here we exploit a combined STM/AFM technique to demonstrate the on-surface formation of complex molecular architectures built up from a heteroaromatic precursor, the tetracyclic pyrazino[2,3-f][4,7]phenanthroline (pap) molecule. Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation occurs on Au(111) upon thermal annealing under ultrahigh vacuum (UHV) conditions. A full atomistic description of the different reaction products based on an unambiguous discrimination between pyrazine and pyridine moieties is presented. Our work not only elucidates that ortho-hydrogen atoms of the pyrazine rings are preferentially activated over their pyridine equivalents, but also sheds new light onto the participation of substrate atoms in metal-organic coordination bonding during covalent C-C bond formation. PMID:27059121

  19. Hydrogen bonds in 1-indanone: Charge density analysis and simulation of the inelastic neutron scattering spectrum in solid phase

    International Nuclear Information System (INIS)

    The influence of the intermolecular interactions on the vibrational dynamics of 1-indanone has been checked by simulating the INS spectrum from molecular and DFT periodic calculations, showing that, even in the case of weak hydrogen bonds, those modes associated with lower energy transfer are affected in the solid state. The electron charge distribution of solid 1-indanone has also been studied from a DFT periodic calculation. In order to obtain some insight into the intermolecular interactions Bader's atoms in molecules theory has been used. After a careful analysis of the topological properties of the calculated electron density, bond paths, critical points and other related properties, most of the C-H...π and C-H...O weak hydrogen bonds predicted in the experimental X-ray structure are confirmed. In addition some new H?H interactions were found. Furthermore, a natural bond orbital analysis was performed describing each hydrogen bond as donor-acceptor interactions

  20. Bonding silicones with epoxies

    Energy Technology Data Exchange (ETDEWEB)

    Tira, J.S.

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.

  1. Australia's Bond Home Bias

    OpenAIRE

    Mishra, Anil V; Umaru B. Conteh

    2014-01-01

    This paper constructs the float adjusted measure of home bias and explores the determinants of bond home bias by employing the International Monetary Fund's high quality dataset (2001 to 2009) on cross-border bond investment. The paper finds that Australian investors' prefer investing in countries with higher economic development and more developed bond markets. Exchange rate volatility appears to be an impediment for cross-border bond investment. Investors prefer investing in countries with ...

  2. Performance of microstrip gas chambers with conductive surface coating of doped amorphous silicon carbide (a-Si:C:H)

    International Nuclear Information System (INIS)

    A new technique involves the use of doped amorphous silicon carbide (a-Si:C:H) as a conductive surface coating in the fabrication of microstrip gas chambers, to eliminate the effect of charge accumulation on the substrate surface. The performance of these detectors made in this way has been tested, measuring gas gains with respect to several operating parameters such as time, anode voltage (Va), backplane voltage (Vb), and drift voltage (Vd). Doped a-Si:C:H film is a conductive surface coating that works well, and is an attractive alternative to other surface treatments of the substrate, because its resistivity can be easily controlled over a wide range by doping, it has a naturally good radiation hardness, and large areas can be coated at relatively low cost. (orig.)

  3. Hot reactions in the systems 11C/H2O(l), 11C/H2O-NH3(l) and 13N/H2O(g)

    International Nuclear Information System (INIS)

    The chemical reactions of hot 11C with liquid water and a water ammonia mixture of mass ratio 3:1 and of 13N with water vapour were studied at T = 295 K. 11C was generated by the nuclear processes 16O(p,α,pn)11C and 14N(p,α)11C. 13N was produced via the 16O(p,α)13N nuclear reaction. The proton radiation dose was varied from D* = 2.8x10-3 to 0.28 eV per target molecule for the system 11C/H2O(l), from D* = 2.2 to 32 eV for the system 11C/H2O-NH3(l) and from D* = 0.13 to 6.2 eV for the system 13N/H2O(g), in order to follow radiolytic changes of the reaction products. Products of the system 11C/H2O(l) were 11CO2 (98-100% radiochemical yield) and 11CO (max. 1.5%). For the system 11C/H2O-NH3(l) six products (11CO2, 11CO, H11COOH, 11CH2O, 11CH3OH and 11CH4) were observed at radiation doses up to D* = 32 eV. In the system 13N/H2O(g) five products were detected: 13NO2, 13NO, 13NN, 13NNO and some 13NH3. 13NO is the main product at lowest doses with radiochemical yields exceeding 45%. With increasing radiolysis 13NO is changed to 13NO2. At higher doses 13NN becomes the main product. The system 11C/H2O-NH3(l) seems to bear some importance for the production of labelled precursors for the synthesis of radiopharmaceuticals. The interesting products 11CH2O and 11CH3OH are still formed under intensive irradiation which is necessary for the production of high radioactivities for nuclear medical application. (orig./RB)

  4. Carboxylate-Assisted Iridium-Catalyzed C-H Amination of Arenes with Biologically Relevant Alkyl Azides.

    Science.gov (United States)

    Zhang, Tao; Hu, Xuejiao; Wang, Zhen; Yang, Tiantian; Sun, Hao; Li, Guigen; Lu, Hongjian

    2016-02-24

    An iridium-catalyzed C-H amination of arenes with a wide substrate scope is reported. Benzamides with electron-donating and -withdrawing groups and linear, branched, and cyclic alkyl azides are all applicable. Cesium carboxylate is crucial for both reactivity and regioselectivity of the reactions. Many biologically relevant molecules, such as amino acid, peptide, steroid, sugar, and thymidine derivatives can be introduced to arenes with high yields and 100 % chiral retention. PMID:26712274

  5. Performance of microdot (MDOT) detectors with conductive coating of doped amorphous silicon carbide (a-Si:C:H)

    International Nuclear Information System (INIS)

    A conductive coating of doped amorphous silicon carbide (a-Si:C:H) has been used in the fabrication of microdot (MDOT) detectors, to minimize the defocusing, away from the anodes, of the drifting primary electrons. This defocusing is caused by the existence of the readout line passing below the insulating layer. The defocusing effect and other effects of the conductive coating on the performance of these detectors fabricated in this way have been investigated

  6. Malaysia : Bond Market Development

    OpenAIRE

    International Monetary Fund; World Bank

    2013-01-01

    This paper pertains to the bond market development in Malaysia, and provides an overview of the market scenario in the country. Malaysia has been successful in developing the capital markets, particularly bond markets, in the recent past. Now, it faces the challenge of how to improve broader access and efficiency of the bond market. A high degree of investor concentration, dominated by gov...

  7. Chemical bond fundamental aspects of chemical bonding

    CERN Document Server

    Frenking, Gernot

    2014-01-01

    This is the perfect complement to ""Chemical Bonding - Across the Periodic Table"" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemica

  8. Superhard nanocomposite nc-TiC/a-C:H film fabricated by filtered cathodic vacuum arc technique

    International Nuclear Information System (INIS)

    Superhard nanocomposite nc-TiC/a-C:H films, with an excellent combination of high elastic recovery, low friction coefficient and good H/E ratio, were prepared by filtered cathodic vacuum arc technique using the C2H2 gas as the precursor. The effect of C2H2 flow rate on the microstructure, phase composition, mechanical and tribological properties of nanocomposite nc-TiC/a-C:H films have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy disperse spectroscopy (EDS), microindentation and tribotester measurements. It was observed that the C2H2 flow rate significantly affected the Ti content and hardness of films. Furthermore, by selecting the proper value for C2H2 flow rate, 20 sccm, one can deposit the nanocomposite film nc-TiC/a-C:H with excellent properties such as superhardness (66.4 GPa), high elastic recovery (83.3%) and high H/E ratio (0.13)

  9. FINAL TECHNICAL REPORT for grant DE-FG02-93ER14353 "Carbon-Hydrogen Bond Functionalization Catalyzed by Transition Metal Systems"

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, Alan S

    2012-05-21

    Alkanes are our most abundant organic resource but are highly resistant to selective chemical transformations. Alkenes (olefins) by contrast are the single most versatile class of molecules for selective transformations, and are intermediates in virtually every petrochemical process as well as a vast range of commodity and fine chemical processes. Over the course of this project we have developed the most efficient catalysts to date for the selective conversion of alkanes to give olefins, and have applied these catalysts to other dehydrogenation reactions. We have also developed some of the first efficient catalysts for carbonylation of alkanes and arenes to give aldehydes. The development of these catalysts has been accompanied by elucidation of the mechanism of their operation and the factors controlling the kinetics and thermodynamics of C-H bond activation and other individual steps of the catalytic cycles. This fundamental understanding will allow the further improvement of these catalysts, as well as the development of the next generation of catalysts for the functionalization of alkanes and other molecules containing C-H bonds.

  10. A Series of Diamagnetic Pyridine Monoimine Rhenium Complexes with Different Degrees of Metal-to-Ligand Charge Transfer: Correlating (13) C NMR Chemical Shifts with Bond Lengths in Redox-Active Ligands.

    Science.gov (United States)

    Sieh, Daniel; Kubiak, Clifford P

    2016-07-18

    A set of pyridine monoimine (PMI) rhenium(I) tricarbonyl chlorido complexes with substituents of different steric and electronic properties was synthesized and fully characterized. Spectroscopic (NMR and IR) and single-crystal X-ray diffraction analyses of these complexes showed that the redox-active PMI ligands are neutral and that the overall electronic structure is little affected by the choices of the substituent at the ligand backbone. One- and two-electron reduction products were prepared from selected starting compounds and could also be characterized by multiple spectroscopic methods and X-ray diffraction. The final product of a one-electron reduction in THF is a diamagnetic metal-metal-bonded dimer after loss of the chlorido ligand. Bond lengths in and NMR chemical shifts of the PMI ligand backbone indicate partial electron transfer to the ligand. Two-electron reduction in THF also leads to the loss of the chlorido ligand and a pentacoordinate complex is obtained. The comparison with reported bond lengths and (13) C NMR chemical shifts of doubly reduced free pyridine monoaldimine ligands indicates that both redox equivalents in the doubly reduced rhenium complex investigated here are located in the PMI ligand. With diamagnetic complexes varying over three formal reduction stages at the PMI ligand we were, for the first time, able to establish correlations of the (13) C NMR chemical shifts with the relevant bond lengths in redox-active ligands over a full redox series. PMID:27319753

  11. Strong covalent bonding between two graphene layers

    OpenAIRE

    Andres, P. L. de; Ramírez, Rafael; Vergés, José A.

    2008-01-01

    We show that two graphene layers stacked directly on top of each other (AA stacking) form strong chemical bonds when the distance between planes is 0.156 nm. Simultaneously, C-C in-plane bonds are considerably weakened from partial double-bond (0.141 nm) to single bond (0.154 nm). This polymorphic form of graphene bilayer is meta-stable w.r.t. the one bound by van der Waals forces at a larger separation (0.335 nm) with an activation energy of 0.16 eV/cell. Similarly to the structure found in ...

  12. 75 FR 39730 - Tribal Economic Development Bonds

    Science.gov (United States)

    2010-07-12

    ... for the issuance of tax-exempt bonds by Indian ] tribal governments under Section 7871. See 71 FR... 54AA upon satisfaction of the additional eligibility requirements for Build America Bonds. See IRS... hotels or convention centers, as well as projects involving certain qualified private activities, to...

  13. Formation, Characterization, and O-O Bond Activation of a Peroxomanganese(III) Complex Supported by a Cross-Clamped Cyclam Ligand.

    Science.gov (United States)

    Colmer, Hannah E; Howcroft, Anthony W; Jackson, Timothy A

    2016-03-01

    Although there have been reports describing the nucleophilic reactivity of peroxomanganese(III) intermediates, as well as their conversion to high-valent oxo-bridged dimers, it remains a challenge to activate peroxomanganese(III) species for conversion to high-valent, mononuclear manganese complexes. Herein, we report the generation, characterization, and activation of a peroxomanganese(III) adduct supported by the cross-clamped, macrocyclic Me2EBC ligand (4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane). This ligand is known to support high-valent, mononuclear Mn(IV) species with well-defined spectroscopic properties, which provides an opportunity to identify mononuclear Mn(IV) products from O-O bond activation of the corresponding Mn(III)-peroxo adduct. The peroxomanganese(III) intermediate, [Mn(III)(O2)(Me2EBC)](+), was prepared at low-temperature by the addition of KO2 to [Mn(II)(Cl)2(Me2EBC)] in CH2Cl2, and this complex was characterized by electronic absorption, electron paramagnetic resonance (EPR), and Mn K-edge X-ray absorption (XAS) spectroscopies. The electronic structure of the [Mn(III)(O2)(Me2EBC)](+) intermediate was examined by density functional theory (DFT) and time-dependent (TD) DFT calculations. Detailed spectroscopic investigations of the decay products of [Mn(III)(O2)(Me2EBC)](+) revealed the presence of mononuclear Mn(III)-hydroxo species or a mixture of mononuclear Mn(IV) and Mn(III)-hydroxo species. The nature of the observed decay products depended on the amount of KO2 used to generate [Mn(III)(O2)(Me2EBC)](+). The Mn(III)-hydroxo product was characterized by Mn K-edge XAS, and shifts in the pre-edge transition energies and intensities relative to [Mn(III)(O2)(Me2EBC)](+) provide a marker for differences in covalency between peroxo and nonperoxo ligands. To the best of our knowledge, this work represents the first observation of a mononuclear Mn(IV) center upon decay of a nonporphyrinoid Mn(III)-peroxo center. PMID:26908013

  14. Special Issue: Intramolecular Hydrogen Bonding

    Directory of Open Access Journals (Sweden)

    Ronald K. Castellano

    2014-09-01

    Full Text Available Intramolecular hydrogen bonds play critical structure- and function-serving roles in biological and synthetic molecular systems. This special issue, through eight contributions, showcases the prominence of these non-covalent interactions within several scientific disciplines, and in various structural contexts and environments. Reported, for example, are the consequences of intramolecular hydrogen bonds on the structures of molecules that show biological activity, for biological mechanisms, and for the conformational switching of functional synthetic molecules. Also showcased in the contributions are the state-of-the-art experimental and theoretical methods available for the characterization of intramolecular hydrogen bonds, which critically report on their strengths, geometries, and spectroscopic signatures in the gas, solid, and solution phases.

  15. The role of p19 C-H-Ras protein in metastasis and proliferative pathways

    OpenAIRE

    García Cruz, Roseli Marlen

    2013-01-01

    Ras is an evolutionary and conserved family of genes present in many organisms, in humans, Ras is conformed by three members called N-Ras, K-Ras and H-Ras located on chromosomes 1, 11 and 12 respectively (1, 2). Ras proteins act as a molecular switch, activating many signalling pathways through phosphorylation of GTPases; so their punctual mutations promote a constitutive activation in their GTPase function that fosters carcinogenesis, loss of adhesion and invasion of malignant cells (3-9). I...

  16. 2006 C. H. McCloy Research Lecture: Defining Learning as Conceptual Change in Physical Education and Physical Activity Settings

    Science.gov (United States)

    Ennis, Catherine D.

    2007-01-01

    The author discusses a line of research examining the acquisition, organization, and use of knowledge associated with conceptual change in which she is engaged at the University of Maryland. It builds on foundational research by scholars in science, mathematics, and reading education as well as in motor learning and physical education pedagogy,…

  17. Photocatalytic/Cu-Promoted C-H Activations: Visible-light-Induced ortho-Selective Perfluoroalkylation of Benzamides.

    Science.gov (United States)

    Chen, Xiang; Tan, Ze; Gui, Qingwen; Hu, Liang; Liu, Jidan; Wu, Jing; Wang, Guangwei

    2016-04-25

    A visible-light-induced and copper-promoted perfluoroalkylation of benzamides was successfully developed under the assistance of an 8-aminoquinoline directing group. It provides a straightforward method for the synthesis of ortho-perfluoroalkyl-substituted benzoic acid derivatives. The reaction employs a cheap organic dye eosin Y as the photoredox catalyst and is run under the irradiation of a 26 W fluorescent LED light bulb. PMID:26933840

  18. The pseudohydrogen bond structures between 2-F-epoxy-butane and three kinds of bimolecular

    International Nuclear Information System (INIS)

    The weak intermolecular interactions between 2-F-epoxy-butane and Iminazole, Thiazole and Oxazole were theoretically discussed by using density functional B3LYP (Becke, three-parameter, Lee- Yang-Parr)/6-311++G** and HF (Hartree Fock)/6-311++G** methods. The results showed that both the N…H conventional hydrogen bond and C-F…H-C pseudohydrogen bond (PHB) structures are coexisting in the three complexes. The weak intermolecular interactions energies indicate the relative stabilities of the three complexes are proportionable. The calculated results showed that the stretch vibrational frequency of C-H bond (electronic acceptor) presents blue shift, but that of C-F bond, which is intensely related to F group (electronic donor), presents red shift. Electron density topological properties demonstrates that the covalent and ionic characteristics of the C-F…H-C pseudohydrogen bond are proportional to that of convention hydrogen bond. (authors)

  19. Weak bond screening system

    Science.gov (United States)

    Chuang, S. Y.; Chang, F. H.; Bell, J. R.

    Consideration is given to the development of a weak bond screening system which is based on the utilization of a high power ultrasonic (HPU) technique. The instrumentation of the prototype bond strength screening system is described, and the adhesively bonded specimens used in the system developmental effort are detailed. Test results obtained from these specimens are presented in terms of bond strength and level of high power ultrasound irradiation. The following observations were made: (1) for Al/Al specimens, 2.6 sec of HPU irradiation will screen weak bond conditions due to improper preparation of bonding surfaces; (2) for composite/composite specimens, 2.0 sec of HPU irradiation will disrupt weak bonds due to under-cured conditions; (3) for Al honeycomb core with composite skin structure, 3.5 sec of HPU irradiation will disrupt weak bonds due to bad adhesive or oils contamination of bonding surfaces; and (4) for Nomex honeycomb with Al skin structure, 1.3 sec of HPU irradiation will disrupt weak bonds due to bad adhesive.

  20. Intermolecular Dehydrative Coupling Reaction of Arylketones with Cyclic Alkenes Catalyzed by a Well-Defined Cationic Ruthenium-Hydride Complex: A Novel Ketone Olefination Method via Vinyl C–H Bond Activation

    OpenAIRE

    Yi, Chae S.; Lee, Do W.

    2010-01-01

    The cationic ruthenium-hydride complex [(η6-C6H6)(PCy3)(CO)RuH]+BF4− was found to be a highly effective catalyst for the intermolecular olefination reaction of arylketones with cycloalkenes. The preliminary mechanistic analysis revealed that electrophilic ruthenium-vinyl complex is the key species for mediating both vinyl C–H bond activation and the dehydrative olefination steps of the coupling reaction.

  1. Ligand-Promoted Borylation of C(sp(3))-H Bonds with Palladium(II) Catalysts.

    Science.gov (United States)

    He, Jian; Jiang, Heng; Takise, Ryosuke; Zhu, Ru-Yi; Chen, Gang; Dai, Hui-Xiong; Dhar, T G Murali; Shi, Jun; Zhang, Hao; Cheng, Peter T W; Yu, Jin-Quan

    2016-01-11

    A quinoline-based ligand effectively promotes the palladium-catalyzed borylation of C(sp(3))-H bonds. Primary β-C(sp(3))-H bonds in carboxylic acid derivatives as well as secondary C(sp(3))-H bonds in a variety of carbocyclic rings, including cyclopropanes, cyclobutanes, cyclopentanes, cyclohexanes, and cycloheptanes, can thus be borylated. This directed borylation method complements existing iridium(I)- and rhodium(I)-catalyzed C-H borylation reactions in terms of scope and operational conditions. PMID:26611496

  2. XPS study of target poisoning during the plasma assisted deposition of a-C:H/Au thin films

    International Nuclear Information System (INIS)

    The X-ray photoelectron spectroscopic (XPS) study of the target poisoning during the deposition of a-C:H/Au using combined radio frequency (RF) powered magnetron sputtering at 100 W and plasma-assisted chemical vapor deposition (PACVD) with a mass flow ratio of 0.5 between CH4 and at is made by Gampp. In this paper we extend this study to both RF and bipolar pulsed (BPP) powered magnetron sputtering in gas mixtures of different values of CH4/Ar mass flow ratio. Elemental compositions of deposited a-C:H/Au layers have been determined by in situ X-ray photoelectron spectroscopy. To determine the elemental content of a sample, the integration over Au 4f7/2, C 1s and 0 1s core level signals (oxygen shows up as an impurity of max. 1 at.%) was used. One may generally conclude that the character of target poisoning process is steep and step-like in time regardless of the type of magnetron power supply, i.e. that it is inherent to the deposition of a-C:H/Au using present deposition setup. Therefore, in the attempts to obtain stable and reproducible deposition conditions and homogeneous coatings, the target had to be driven to the certain degree of poisoning. This is done by conditioning in pure CH4 (covering) and in pure Ar plasma (cleaning) subsequently and alternatively, until the desired Au content is reached. Then, for deposition purposes, a CH4/Ar gas mixture was selected so that steady state of target covering and cleaning is sustained

  3. Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding. Technical progress report, March 1, 1992--February 28, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenberger, D.L.

    1997-06-01

    During this period of the project we have (1) accomplished the high-resolution gas phase photoelectron spectra of C{sub 60} and C{sub 70}, (2) characterized the electronic features of imaging C{sub 60} on gold by STM, (3) evaluated the orbital distributions of C{sub 60} and the bonding interactions with metals, (4) revealed details of the bonding of phosphines to metals, including the subtleties of a geometrical twist in sterically crowded situations, (5) determined the formal electron distribution in the bonding of {eta}{sup 3} -cyclopropenyl with metals, (6) related gas-phase ionization energies to electron transfer kinetics and ion salvation thermochemistry of metallocenes, (7) correlated lone-pair ionization energies with proton affinities for a variety of amino acids and related compounds, (8) examined sigma-pi interactions in non-conjugated polyalkynes, (9) characterized extensive metal-ligand {pi} interactions in metal-acetylide compounds, and (10) continued to develop the experimental and theoretical methods for these studies. All of these studies have contributed significantly to expanding our understanding of the electronic structure and bonding of organic molecules and the ways this electronic structure is altered by interaction with metals. Further developments in the instrumentation and methods of gas phase and surface photoelectron spectroscopy are underway. Most notable is the progress on the new gas phase photoelectron spectrometer that combines improved capabilities for He I/He II UPS, XPS, and Auger investigations of organometallic molecules.

  4. Activation of wood surfaces for glue bonds by mechanical pre-treatment and its effects on some properties of veneer surfaces and plywood panels

    Science.gov (United States)

    Aydin, İsmail

    2004-06-01

    Some chemical pre-treatments with chemical reagents are widely applied to wood surfaces in order to improve bonding ability, wettability and reactivate wood surfaces for glue-wood bonds. Besides these chemical treatments, some mechanical pre-treatments such as sanding and planing can be applied to get a fresh surface which eliminates bonding problems and improves glue bonding of wood. In this study, 2 mm thick rotary cut veneers obtained from steamed beech ( Fagus orientalis) logs were used as material. Both air-drying and oven-drying methods were used for drying veneer. After drying, the surfaces of some veneers were sanded with 100 and 180 grit sandpapers. Three-layer-plywood panels were produced from sanded and non-sanded veneers by using urea formaldehyde and phenol formaldehyde glue resins to evaluate the effects of sanding some mechanical properties of plywood. Changes in pH, surface roughness and adhesive wettability of veneers were evaluated. Wettability of veneers was assessed with contact angle measurements according to the sessile drop method. Both veneer and plywood properties investigated in this study improved clearly after the sanding process. Shear and bending strength values of plywood panels manufactured from sanded and non-sanded veneers were vary depending on glue types and veneer drying methods.

  5. The cheap preparation technology of A-, μC-SiC:H films for thin film solar cells

    International Nuclear Information System (INIS)

    We propose the use of a cheap liquid methyltrichlorosilane (MTCS) as a precursor in the modified plasma enhanced- chemical-vapor-deposition (PECVD) system with a very high frequency (VHF) discharge for preparing high quality hydrogenated amorphous silicon carbide (αSi1-xCx:H) films with the large carbon content. This method allows to control the composition and the morphology of the films in the region of 0.3< x<0.7. The monocrystalline fraction, consisting of 3C-SiC crystallites in an amorphous network (μc-SiC:H), is revealed in the films with the composition of about 0.5. (Author)

  6. C H Rautenbach, P S Dreyer en C K Oberholzer: Hulle nalatenskap en die pad vorentoe1

    Directory of Open Access Journals (Sweden)

    Johann Beukes

    2000-01-01

    Full Text Available C H Rautenbach, P S Dreyer and C K Oberholzer: Their legacy and the way ahead. This article explores the legacy of three early philosophers at the University of Pretoria (1939-1987, who contributed substantially to the Nederduitsch Hervormde Kerk's perspectives on the relation between (modern theology and (modern philosophy. The authors consider their legacy to be an essentially Kantian stabilisation of the complex and problematic relationship between reason and faith, church and society, and theology and philosophy. The article then proceeds to interpret the changes in these relationships that were brought about by the postmodern discourse.

  7. The cheap preparation technology of A-, mC-SiC:H films for thin film solar cells

    International Nuclear Information System (INIS)

    We propose the use of a cheap liquid methyltriclorosilane (MTCS) as a precursor in the modified plasma-enhanced-chemical-vapor-deposition (PECVD) system with a very high frequency (VHF) discharge for preparing high quality hydrogenated amorphous silicon carbide (a-Si1-xCx:H) films with the large carbon content. This method allows to control the composition and the morphology of the films in the region of 0.3< x<0.7. The monocrystalline fraction, consisting of 3C-SiC crystallites in an amorphous network (mc-SiC:H), is reveled in the films with the composition of about 0.5. (Author)

  8. Bond Markets in Africa

    OpenAIRE

    Yibin Mu; Peter Phelps; Janet Gale Stotsky

    2013-01-01

    African bond markets have been steadily growing in recent years, but nonetheless remain undeveloped. African countries would benefit from greater access to financing and deeper financial markets. This paper compiles a unique set of data on corporate bond markets in Africa. It then applies an econometric model to analyze the key determinants of African government securities market and corporate bond market capitalization. Government securities market capitalization is directly related to bette...

  9. Build America Bonds

    OpenAIRE

    Andrew Ang; Vineer Bhansali; Yuhang Xing

    2010-01-01

    Build America Bonds (BABs) are a new form of municipal financing introduced in 2009. Investors in BAB municipal bonds receive interest payments that are taxable, but issuers receive a subsidy from the U.S. Treasury. The BAB program has succeeded in lowering the cost of funding for state and local governments with BAB issuers obtaining finance 54 basis points lower, on average, compared to issuing regular municipal bonds. For institutional investors, BAB issue yields are 116 basis points highe...

  10. Two-dimensional supramolecular networks via C-H$\\cdots$Cl and N-H$\\cdots$Cl interactions utilizing bidentate neutral pyridine amide coordinated MnIICl2 tectons

    Indian Academy of Sciences (India)

    Wilson Jacob; Rabindranath Mukherjee

    2008-09-01

    Reaction of -(phenyl)-2-pyridinecarboxamide (HL1) and -(-tolyl)-2-pyridinecarboxamide (HL2) ligands with MnCl2.4H2O affords complexes [(HL1)2MnCl2] 1 and [(HL2)2MnCl2] 2. The structures of 1 and 2 were determined by three-dimensional X-ray crystallography revealing that the MnII ions assume distorted octahedral geometry with coordination by two HL1/HL2 ligands providing two pyridine N and two amide O and two chloride ions. Notably, secondary interactions [C-H$\\cdots$Cl (pyridine 3-H hydrogen) and N-H$\\cdots$Cl (amide NH hydrogen)] triggered by MnII-coordinated chloride ions acting as hydrogen bonding acceptors generate self-complementary dimeric tectons, which lead to 2D supramolecular architectures.

  11. The Bond Market's q

    OpenAIRE

    Thomas Philippon

    2006-01-01

    I propose an implementation of the q-theory of investment using bond prices instead of equity prices. Credit risk makes corporate bond prices sensitive to future asset values, and q can be inferred from bond prices. The bond market's q performs much better than the usual measure in standard investment equations. With aggregate data, the fit is three times better, cash flows are driven out and the implied adjustment costs are reduced by more than an order of magnitude. The new measure also imp...

  12. Copper wire bonding

    CERN Document Server

    Chauhan, Preeti S; Zhong, ZhaoWei; Pecht, Michael G

    2014-01-01

    This critical volume provides an in-depth presentation of copper wire bonding technologies, processes and equipment, along with the economic benefits and risks.  Due to the increasing cost of materials used to make electronic components, the electronics industry has been rapidly moving from high cost gold to significantly lower cost copper as a wire bonding material.  However, copper wire bonding has several process and reliability concerns due to its material properties.  Copper Wire Bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes—bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation.  In addition, the bond–pad metallurgies and the use of bare and palladium-coated copper wires on aluminum are presented, and gold, nickel and palladium surface finishes are discussed.  The book also discusses best practices and re...

  13. Hydrogen bonding and anaesthesia

    Science.gov (United States)

    Sándorfy, C.

    2004-12-01

    General anaesthetics act by perturbing intermolecular associations without breaking or forming covalent bonds. These associations might be due to a variety of van der Waals interactions or hydrogen bonding. Neurotransmitters all contain OH or NH groups, which are prone to form hydrogen bonds with those of the neurotransmitter receptors. These could be perturbed by anaesthetics. Aromatic rings in amino acids can act as weak hydrogen bond acceptors. On the other hand the acidic hydrogen in halothane type anaesthetics are weak proton donors. These two facts together lead to a probable mechanism of action for all general anaesthetics.

  14. Weak C-H$\\cdots$F-C interactions in carboxylate anion binding: Synthesis, spectroscopic and X-ray structural studies of [Co(phen)2CO3]2 (C7H3O2FCl)Cl$\\cdots$11H2O and [Co(phen)2CO3](C7H3NO4Cl)$\\cdot$6H2O

    Indian Academy of Sciences (India)

    A Singh; R P Sharma; T Aree; P Venugopalan

    2010-09-01

    Two new complex salts containing 2,5-substituted benzoate ions, [Co(phen)2CO3]2 (C7H3O2FCl)Cl$\\cdot$11H2O (1) and [Co(phen)2CO3](C7H3NO4Cl)$\\cdot$6H2O (2) (where phen = 1,10-phenanthroline, C7H3O2FCl = 2-chloro-5-fluorobenzoate (cfbz) and C7H3NO4Cl = 2-chloro-5-nitrobenzoate(cnbz)) were synthesized by reacting carbonatobis(1,10-phenanthroline)cobalt(III) chloride with appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C-H$\\cdots$F and C-H$\\cdots$O interactions amid other heteroatom interactions. The complex salts have been characterized by elemental analyses, spectroscopic studies (IR, UV/Visible, multinuclear NMR), conductance and solubility product measurements. Single crystal X-ray structure determination revealed ionic structures of both the complex salts having discrete ions along with lattice water molecules. Crystal lattice is stabilized by a variety of hydrogen bonding interactions, i.e. O-H$\\cdots$O, C-H$\\cdots$O and C-H$\\cdots$F involving second sphere coordination besides - interaction. Furthermore, packing analyses reveal that C-H…F interactions can manifest even in the presence of a large number of heteroatom interactions.

  15. Modeling of the gas-phase chemistry in C-H-O gas mixtures for diamond chemical vapor deposition

    Science.gov (United States)

    Petherbridge, James R.; May, Paul W.; Ashfold, Michael N. R.

    2001-05-01

    The boundaries of the diamond deposition region in the C-H-O (Bachmann) atomic phase composition diagram have been reproduced successfully for 38 different C, H, and O containing gas mixtures using the CHEMKIN computer package, together with just two criteria—a minimum mole fraction of methyl radicals [CH3] and a limiting value of the [H]/[C2H2] ratio. The diamond growth/no-growth boundary coincides with the line along which the input mole fractions of C and O are equal. For every gas mixture studied, no-growth regions are found to coincide with a negligible (<10-10) mole fraction of CH3 radicals, while for gas mixtures lying within the diamond growth region the CH3 mole fraction is ˜10-7. Each no-growth→diamond growth boundary is seen to be accompanied by a 2-3 order of magnitude step in CH3 mole fraction. The boundary between diamond and nondiamond growth is less clearly defined, but can be reproduced by assuming a critical, temperature dependent [H]/[C2H2] ratio (0.2, in the case that Tgas=2000 K) that reflects the crucial role of H atoms in the etching of nondiamond phases. The analysis allows prediction of the composition process window for good quality diamond growth for all stable input gas mixtures considered in this study.

  16. Reactively co-sputter deposited a-C:H/Cr thin films: Material characteristics and optical properties

    International Nuclear Information System (INIS)

    Various chromium-containing amorphous hydrogenated carbon (a-C:H/Cr) coatings were deposited on oxygen-free copper and silicon substrates for use as solar selective absorber coatings. The deposition was performed using a magnetron co-sputter deposition method under various methane/Ar ratios, ranging from 0 to 8%. The obtained films were characterized using glazing incident X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, secondary ion mass spectrometer, and X-ray photoelectron spectroscopy. The optical absorptance and emittance at 100 °C were determined using UV–vis-NIR spectroscopy and Fourier transform infrared spectrometry, respectively. Effects of the material characteristics on the optical properties are reported and discussed. - Highlights: ► a-C:H/Cr coatings were prepared using reactive magnetron co-sputtering deposition. ► Cr exists as crystallites having diameters in between 1 to 2 nm. ► Coating prepared with 3% methane in the gas fed exhibits the best optical absorptance

  17. Adaptation of the C.H.A.D. computer library to nuclear simulations

    Science.gov (United States)

    Rock, Daniel Thomas

    The Computational Hydrodynamics for Automotive Design computer program, CHAD, is a modern, three-dimensional computational fluid dynamics code that holds promise for fulfilling a need in the nuclear industry and academia. Because CHAD may be freely distributed to non export controlled countries, it offers a cheap and customizable CFD capability. Several modifications were made to CHAD to make it more usable to those in industry and academia. A first order up-winding scheme for momentum and enthalpy and a reformulated continuity equation were migrated from a historical version of CHAD developed at Argonne National Laboratory. The Portable, Extensible Toolkit for Scientific Computing, PETSc, was also added as an optional solver package for the original and reformulated continuity equations. PETSc's highly optimized parallel solvers can be activated from either CHAD's input file or the command line. Solution times for PETSc based calculations depend in large part on convergence criteria provided, however improvements in CPU time of approximately one-third have been observed. CHAD was further extended by adding a capability to monitor solution progress by specifying a coordinate in space, as well as monitoring the residuals in the problem. The ability to model incompressible fluids was also added to the code. Incompressible fluid comparisons were made using several test cases against the commercial CFD code Fluent and found to agree well. A major limitation of CHAD in the academic environment is a limited mesh generation capability. A tool for CHAD was developed that translates Gambit based neutral mesh files into a CHAD usable format. This tool was used to translate a large mesh representing a simplified cooling jacket of a BWR control rod drive. This model serves as a practical, demonstration application of a nuclear application for CHAD and PETSc. Both CHAD with PETSc and Fluent were used to obtain solutions to this problem. The overall agreement between the two

  18. Inhibition of C: H Co-deposit Formation by Ammonia Injection in Remote Areas of ITER

    International Nuclear Information System (INIS)

    results point to the presence of a fast reaction between ammonia and the carbon radicals created in the methane plasma. In this work, these results will be presented and their implication on the strategy for hydrogen retention control by the scavenger technique in the non-activated phase of ITER will be addressed. (author)

  19. Enhancement of laccase activity through the construction and breakdown of a hydrogen bond at the type I copper center in Escherichia coli CueO and the deletion mutant Δα5-7 CueO.

    Science.gov (United States)

    Kataoka, Kunishige; Hirota, Shun; Maeda, Yasuo; Kogi, Hiroki; Shinohara, Naoya; Sekimoto, Madoka; Sakurai, Takeshi

    2011-02-01

    CueO is a multicopper oxidase involved in a copper efflux system of Escherichia coli and has high cuprous oxidase activity but little or no oxidizing activity toward various organic substances. However, its activity toward oxidization of organic substrates was found to be considerably increased by the removal of the methionine-rich helical segment that covers the substrate-binding site (Δα5-7 CueO) [Kataoka, K., et al. (2007) J. Mol. Biol. 373, 141]. In the study presented here, mutations at Pro444 to construct a second NH-S hydrogen bond between the backbone amide and coordinating Cys500 thiolate of the type I copper are shown to result in positive shifts in the redox potential of this copper center and enhanced oxidase activity in CueO. Analogous enhancement of the activity of Δα5-7 CueO has been identified only in the Pro444Gly mutant because Pro444 mutants limit the incorporation of copper ions into the trinuclear copper center. The activities of both CueO and Δα5-7 CueO were also enhanced by mutations to break down the hydrogen bond between the imidazole group of His443 that is coordinated to the type I copper and the β-carboxy group of Asp439 that is located in the outer sphere of the type I copper center. A synergetic effect of the positive shift in the redox potential of the type I copper center and the increase in enzyme activity has been achieved by the double mutation of Pro444 and Asp439 of CueO. Absorption, circular dichroism, and resonance Raman spectra indicate that the characteristics of the Cu(II)-S(Cys) bond were only minimally perturbed by mutations involving formation or disruption of a hydrogen bond from the coordinating groups to the type I copper. This study provides widely applicable strategies for tuning the activities of multicopper oxidases. PMID:21142169

  20. Comparison of Gold Bonding with Mercury Bonding

    NARCIS (Netherlands)

    Kraka, Elfi; Filatov, Michael; Cremer, Dieter

    2009-01-01

    Nine AuX molecules (X = H, O, S, Se, Te, F, Cl, Br, I), their isoelectronic HgX(+) analogues, and the corresponding neutral HgX diatomics have been investigated using NESC (Normalized Elimination of the Small Component) and B3LYP theory to determine relativistic effects for bond dissociation energie

  1. Molecular dynamics simulation of liquid methanol. II. Unified assignment of infrared, raman, and sum frequency generation vibrational spectra in methyl C-H stretching region

    Science.gov (United States)

    Ishiyama, Tatsuya; Sokolov, Vladimir V.; Morita, Akihiro

    2011-01-01

    Vibrational spectra of methyl C-H stretching region are notoriously complicated, and thus a theoretical method of systematic assignment is strongly called for in condensed phase. Here we develop a unified analysis method of the vibrational spectra, such as infrared (IR), polarized and depolarized Raman, and ssp polarized sum frequency generation (SFG), by flexible and polarizable molecular dynamics simulation. The molecular model for methanol has been developed by charge response kernel model to allow for analyzing the methyl C-H stretching vibrations. The complicated spectral structure by the Fermi resonance has been unraveled by empirically shifting potential parameters, which provides clear information on the coupling mechanism. The analysis confirmed that for the IR, polarized Raman, and SFG spectra, two-band structure at about 2830 and 2950 cm^{-1} results from the Fermi resonance splitting of the methyl C-H symmetric stretching and bending overtones. In the IR spectrum, the latter, higher-frequency band is overlapped with prominent asymmetric C-H stretching bands. In the depolarized Raman spectrum, the high frequency band at about 2980 cm^{-1} is assigned to the asymmetric C-H stretching mode. In the SFG spectrum, the two bands of the splitted symmetric C-H stretching mode have negative amplitudes of imaginary nonlinear susceptibility χ ^{(2)}, while the higher-frequency band is partly cancelled by positive imaginary components of asymmetric C-H stretching modes.

  2. The problem of dose in homeopaty: evaluation of the effect of high dilutions of Arsenicum album 30cH on rats intoxicasted with arsenic

    Directory of Open Access Journals (Sweden)

    Maria Imaculada Lima Montebelo

    2011-09-01

    Full Text Available Background: Although scientific studies have confirmed the action of homeopathic high dilutions in living organisms an endless debate on the choice of the most fitting dilution, the frequency of administration and the dose (amount of medicine still remains. Aims: This study sought to assess the in vivo effect of 2 different concentrations of Arsenicum album 30cH in order to elucidate some problems in the homeopathic notion of dose. Methods: Male Wistar rats previously intoxicated with sodium arsenate by peritoneal injection were treated with undiluted Ars 30cH and Ars 30cH in 1% solution administered by oral route. Atomic absorption spectroscopy was employed to measure the levels of arsenic retained in the animals as well as the amounts eliminated through urine. Urine samples were collected before and after and during treatment. A positive control group (intoxicated animals and negative control group (non-intoxicated animals were administered only the vehicle used to prepare the medicine (ethanol. Results: The groups treated with undiluted Ars 30cH and Ars 30cH in 1% solution eliminated significant amounts of arsenic through urine when compared to the control groups. The group treated with undiluted Ars 30cH eliminated significantly higher amounts of arsenic than the group treated with the same medicine in 1% solution. Conclusion: These results suggest that undiluted Ars 30cH was more effective than in 1% solution in this experimental model.

  3. Coupled valence bond theory

    NARCIS (Netherlands)

    Havenith, R.W.A.

    2005-01-01

    In this Letter, the formulation and implementation of a parallel response property code for non-orthogonal, valence bond wave-functions are described. Test calculations on benzene and cyclobutadiene show that the polarisability and magnetisability tensors obtained using valence bond theory are compa

  4. Bonded labour in Pakistan

    OpenAIRE

    Ercelawn, Aly; Nauman, Muhammad

    2001-01-01

    Examines the continuing prevalence of debt bondage in the 1990s despite the introduction of national legislation banning the practice. Makes recommendations to the Government and the international community for actions to be taken to eliminate bonded labour and provide rehabilitation for freed workers. Includes texts of Land Reforms Regulations, 1972, the Sindh Tenancy Act, 1950 and the Bonded Labour System (Abolition) Act, 1992.

  5. The samurai bond market

    OpenAIRE

    Frank Packer; Elizabeth Reynolds

    1997-01-01

    Issuance in the samurai bond market has more than tripled over the past several years. Some observers have attributed this growth to a systematic underestimation of credit risk in the market. A detailed review of credit quality, ratings differences, and initial issue pricing in the samurai bond market, however, turns up little evidence to support this concern.

  6. Money and Nominal Bonds

    OpenAIRE

    Marchesiani, Alessandro; Senesi, Pietro

    2007-01-01

    This paper studies an economy with trading frictions, ex post heterogeneity and nominal bonds in a model à la Lagos and Wright (2005). It is shown that a strictly positive interest rate is a sufficient condition for the allocation with nominal bonds to be welfare improving. This result comes from the protection against the inflation tax.

  7. Hydrogen bonding in polyanilines

    Energy Technology Data Exchange (ETDEWEB)

    Bahceci, S. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)); Toppare, L. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)); Yurtsever, E. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey))

    1994-11-29

    Hydrogen bonding between poly(bisphenol A carbonate) (PC) and polyaniline (PAn) is analyzed using semi-empirical quantum methodology. Fully optimized AM1 molecular orbital calculations are reported for various aniline structures (monomer, dimer and trimer), the monomer of the PC and the hydrogen-bonded model of PAn-PC oligomer. ((orig.))

  8. Characterization of a-SiC:H as a window material for p-i-n a-Si solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Tawada, Y.; Hamakawa, Y.; Kondo, M.; Nishimura, K.; Okamoto, H.; Tsuge, K.

    1982-01-01

    Films of a-SiC:H were settled by method of plasma breakdown of a mixture of silane with methane (SM) or silane with ethylene (SET). For optical and optical-electron measurements, films of a-SiC:H were applied to a substrate made of glass or monocrystalline Si. Photoelectrical properties were studied on solar cells with structure glass/Sn0/sub 2//p-a-SiC:H/5-n-aSi:H/Al in which a layer of a-SiC:H of thickness 10 mm was alloyed by B. With increase in the width of the forbidden zone of a-SiC:H from 1.75 to 2.15 eV, current density of short circuiting of the solar cell rises from 10.5 to 12.5 mA/cm/sub 2/, if a-SiC:H was obtained from SM, and roughly from 9 to 10.5 mA/cm/sub 2/ if from SET. The photoelectromotive force changes in this case approximately from 0.8 to 0.9 V. The jump in potential on the boundary of the valent zone in the p-i-heterotransition, where a-SiC:H was obtained from the SET limits the collection of light-generated holes from the i-layer. The film of a-Si-C:H obtained from the SET contains C mainly in the form of C/sup 2/H/sup 5/ groups, while a-SiC:H from CM is an amorphous alloy close to the ideal with small quantity of the CH/sup 3/ groups.

  9. Synthesis, characterization and molecular modelling of a novel dipyridamole supramolecule - X-ray structure, quantum mechanics and molecular dynamics study to comprehend the hydrogen bond structure-activity relationship

    Science.gov (United States)

    Vepuri, Suresh B.; Devarajegowda, H. C.; Soliman, Mahmoud E.

    2016-02-01

    Hydrochloride salt formation for Active Pharmaceutical Ingredients (APIs) is the primary choice to impart aqueous solubility and to promote dissolution. Dipyridamole (DIP) is a cardiovascular drug which is practically insoluble in water. We discovered a new form of DIP called as dipyridamole hydrochloride trihydrate (DIPHT), which was prepared by an unusual method of reacting the DIP with hydrated hydrochloric acid (HCl) that was liberated in situ by the reaction of ferric chloride with water. The liberated HCl was consumed as reagent in situ by the scavenger (API) and was converted to a hydrochloride trihydrate. The product was characterized by FTIR, mass spectroscopy, PXRD and DSC. Supramolecular structure of this novel DIPHT was revealed by single crystal XRD. A sustained intramolecular hydrogen bond alliance was found in DIP and the DIPHT. Stability of this hydrogen bond was further evaluated by means of molecular modelling studies. We performed electron calculations using quantum mechanics (QM) on both the base and salt structures to compare their geometry and molecular orbital energy levels. Molecular Dynamics (MD) simulations were also conducted in explicit solvent models to provide more insights into the hydrogen bond strength and conformational preferences of the base and salt structure. Together with QM and MD, we were able to explain the influence of hydrogen bonds on proton uptake activity of DIP and stability of DIP and DIPHT. DIPHT which can dissolve faster than DIP in water may enhance the dissolution and bioavailability of the drug. As the current drug development research is shifting to repurpose the existing drugs in order to subside the untoward risks in new drug development, we believe that DIPHT with its intrinsic aqueous solubility could bring more application for DIP and generate interest within the pharmaceutical industry.

  10. Influence of Water Storage and Bonding Material on Bond Strength of Metallic Brackets to Ceramic.

    Science.gov (United States)

    Costa, Ana Rosa; Correr, Américo Bortolazzo; Consani, Simonides; Giorgi, Maria Cecília Caldas; Vedovello, Silvia Amélia; Vedovello Filho, Mário; Santos, Eduardo Cesar Almada; Correr-Sobrinho, Lourenço

    2015-10-01

    This study investigated the influence of water storage (24 h and 6 months), and Transbond XT and Fuji Ortho LC bonding materials on the bond strength of metallic brackets bonded to feldspathic ceramic. Four cylinders of feldspathic ceramic were etched with 10% hydrofluoric acid for 60 s. Each cylinder received two layers of silane. Metallic brackets were bonded to the cylinders using Transbond XT or Fuji Ortho LC. Light-activation was carried out with 40 s total exposure time using Bluephase G2. Half the specimens for each bonding materials (n=20) were stored in distilled water at 37 °C for 24 h and the other half for 6 months. Shear bond strength testing was performed after storage times at a crosshead speed of 1 mm/min. The adhesive remnant index (ARI) was used to evaluate the amount of adhesive remaining on the ceramic surface at ×8 magnification. Data were subjected to two-way ANOVA and Tukey's test (p<0.05). Transbond XT showed significantly higher bond strength (p<0.05) than Fuji Ortho LC. Significant differences in bond strength (p<0.05) were found when 24 h and 6 months storage times were compared between materials. ARI showed a predominance of score 0 for all groups, and higher scores at 1, 2 and 3 for 24 h storage time. In conclusion, storage time and bonding materials showed significant influence on the bond strength of brackets to ceramic. PMID:26647936

  11. Shape Bonding method

    Science.gov (United States)

    Pontius, James T. (Inventor)

    2010-01-01

    The present invention is directed to a method of bonding at least two surfaces together. The methods step of the present invention include applying a strip of adhesive to a first surface along a predefined outer boundary of a bond area and thereby defining a remaining open area there within. A second surface, or gusset plate, is affixed onto the adhesive before the adhesive cures. The strip of adhesive is allowed to cure and then a second amount of adhesive is applied to cover the remaining open area and substantially fill a void between said first and second surfaces about said bond area. A stencil may be used to precisely apply the strip of adhesive. When the strip cures, it acts as a dam to prevent overflow of the subsequent application of adhesive to undesired areas. The method results in a precise bond area free of undesired shapes and of a preferred profile which eliminate the drawbacks of the prior art bonds.

  12. Water's Hydrogen Bond Strength

    CERN Document Server

    Chaplin, Martin

    2007-01-01

    Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperature...

  13. Stereoselective Synthesis of 1,3-Diaminotruxillic Acid Derivatives: An Advantageous Combination of C-H-ortho-Palladation and On-Flow [2+2]-Photocycloaddition in Microreactors.

    Science.gov (United States)

    Serrano, Elena; Juan, Alberto; García-Montero, Angel; Soler, Tatiana; Jiménez-Márquez, Francisco; Cativiela, Carlos; Gomez, M Victoria; Urriolabeitia, Esteban P

    2016-01-01

    The stereoselective synthesis of ε-isomers of dimethyl esters of 1,3-diaminotruxillic acid in three steps is reported. The first step is the ortho-palladation of (Z)-2-aryl-4-aryliden-5(4H)-oxazolones 1 to give dinuclear complexes 2 with bridging carboxylates. The reaction occurs through regioselective activation of the ortho-CH bond of the 4-arylidene ring in carboxylic acids. The second step is the [2+2]-photocycloaddition of the CC exocyclic bonds of the oxazolone skeleton in 2 to afford the corresponding dinuclear ortho-palladated cyclobutanes 3. This key step was performed very efficiently by using LED light sources with different wavelengths (465, 525 or 625 nm) in flow microreactors. The final step involved the depalladation of 3 by hydrogenation in methanol to afford the ε-1,3-diaminotruxillic acid derivatives as single isomers. PMID:26597315

  14. Carbodiimide Inactivation of MMPs and Effect on Dentin Bonding

    OpenAIRE

    Mazzoni, A.; Apolonio, F.M.; Saboia, V.P.A.; de Santi, S; Angeloni, V; Checchi, V.; Curci, R.; Di Lenarda, R.; Tay, F.R.; Pashley, D.H.; Breschi, L.

    2014-01-01

    The use of protein cross-linking agents during bonding procedures has been recently proposed to improve bond durability. This study aimed to use zymography and in situ zymography techniques to evaluate the ability of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) cross-linker to inhibit matrix metalloproteinase (MMP) activity. The hypotheses tested were that: (1) bonding procedures increase dentin gelatinolytic activity and (2) EDC pre-treatment prevents this enzymatic activity. The zym...

  15. Fields, particles and analyticity: recent results or 30 goldberg (ER) variations on B.A.C.H

    International Nuclear Information System (INIS)

    As it is known, Axiomatic Field Theory (A) implies double analyticity of the η-point functions in space-time and energy-momentum Complex Variables (C), with various interconnections by Fourier-Laplace analysis. When the latter is replaced by. Harmonic Analysis (H) on spheres and hyperboloids, a new kind of double analyticity results from (A) (i.e. from locality, spectral condition, temperateness and invariance): complex angular momentum is thereby introduced (a missing chapter in (A)). Exploitation of Asymptotic Completeness via Bethe-Salpeter-type equations (B) leads to new developments of the previous theme on (A, C, H) (complex angular momentum) and of other themes on (A,C) (crossing, Haag-Swieca property etc...). Various aspects of (A) + (B) have been implemented in Constructive Field Theory (composite spectrum, asymptotic properties etc...) by a combination of specific techniques and of model-independent methods

  16. Grain-size effect on the preferred orientation of TiC/α-C:H thin films

    International Nuclear Information System (INIS)

    The grain-size effect on the preferred orientation has been revealed in TiC/α-C:H nanocomposite films grown by magnetron sputtering, in which the grain size of TiC can be adjusted through changing C content in films. The finding is that the preferred orientation of films is significantly affected by the grain size, and the crystallographic orientation changes from face-centered cubic (fcc) TiC(1 1 1) to (2 0 0) as the grain size of nanocrystallite TiC decreases from ∼22.3 to ∼4.7 nm. This size-dependent preferred orientation is explained via thermodynamic calculations, from which the size-dependent Gibbs free energies are found to be a key factor that controls the texture development in thin films if the grain size in films is sufficient small.

  17. Kinetic model of C/H/N/O emissions in laser-induced breakdown spectroscopy of organic compounds

    International Nuclear Information System (INIS)

    A kinetic model to predict the relative intensities of the atomic C/H/N/O emission lines in laser-induced breakdown spectroscopy (LIBS) has been developed for organic compounds. The model includes a comprehensive set of chemical processes involving both neutral and ionic chemistry and physical excitation and de-excitation of atomic levels affecting the neutral, ionic, and excited-state species concentrations. The relative excited-state atom concentrations predicted by this modeling are compared with those derived from the observed LIBS intensities for 355 nm ns laser irradiation of residues of two organic compounds on aluminum substrate. The model reasonably predicts the relative excited-state concentrations, as well as their time profiles. Comparison of measured and computed concentrations has also allowed an estimation of the degree of air entrainment.

  18. Modeling the absorption behavior of solar thermal collector coatings utilizing graded alpha-C:H/TiC layers.

    Science.gov (United States)

    Gruber, D P; Engel, G; Sormann, H; Schüler, A; Papousek, W

    2009-03-10

    Wavelength selective coatings are of common use in order to enhance the efficiency of devices heated by radiation such as solar thermal collectors. The use of suitable materials and the optimization of coating layer thicknesses are advisable ways to maximize the absorption. Further improvement is achievable by embedding particles in certain layers in order to modify material properties. We focus on optimizing the absorption behavior of a solar collector setup using copper as substrate, a layer of amorphous hydrogenated carbon with embedded titanium carbide particles (a-C:H/TiC), and an antireflection coating of amorphous silicon dioxide (aSiO(2)). For the setup utilizing homogeneous particle distribution, a relative absorption of 90.98% was found, while inhomogeneous particle embedding yielded 98.29%. These results are particularly interesting since until now, absorption of more than 95% was found only by using embedded Cr but not by using the more biocompatible Ti. PMID:19277084

  19. Nature of the Xe(VI) -N Bonds in F6 XeNCCH3 and F6 Xe(NCCH3 )2 and the Stereochemical Activity of Their Xenon Valence Electron Lone Pairs.

    Science.gov (United States)

    Haner, Jamie; Matsumoto, Kazuhiko; Mercier, Hélène P A; Schrobilgen, Gary J

    2016-03-24

    The recently reported syntheses and X-ray crystal structures of the highly endothermic compounds F6 XeNCCH3 and F6 Xe(NCCH3 )2 ⋅CH3 CN provide the first, albeit weakly covalent, Xe(VI) -N bonds. The XeF6 unit of F6 XeNCCH3 possesses distorted octahedral (C3v ) symmetry similar to gas-phase XeF6 , whereas the XeF6 unit of F6 Xe(NCCH3 )2 ⋅CH3 CN possesses C2v symmetry. Herein, the natural bond orbital (NBO), atoms in molecules (AIM), electron localization function (ELF), and molecular electrostatic potential surface (MEPS) analyses show that the Xe valence electron lone pairs (VELPs) of both compounds are stereochemically active. The Xe VELPS are diffuse and ineffectively screen their Xe cores so that the Xe VELP positions correspond to the most electrophilic regions of the MEPS, which enables the opposing N VELP of CH3 CN to coordinate to this region. These bonds are predominantly electrostatic in nature and are interpreted as σ-hole interactions. PMID:26918266

  20. Surface morphology and grain analysis of successively industrially grown amorphous hydrogenated carbon films (a-C:H) on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Catena, Alberto [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany); McJunkin, Thomas [Department of Physics, The Ohio State University, 43210 Columbus, Ohio (United States); Agnello, Simonpietro; Gelardi, Franco M. [Department of Physics and Chemistry, University of Palermo, 90100 Palermo (Italy); Wehner, Stefan [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany); Fischer, Christian B., E-mail: chrbfischer@uni-koblenz.de [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany)

    2015-08-30

    Graphical abstract: - Highlights: • Two different a-C:H coatings in various thicknesses on Si (1 0 0) have been studied. • For both types no significant difference in surface morphology is detectable. • The grain number with respect to their height appears randomly distributed. • In average no grain higher than 14 nm and larger than 0.05 μm{sup 2} was observed. • A height to area correlation confines all detected grains to a limited region. - Abstract: Silicon (1 0 0) has been gradually covered by amorphous hydrogenated carbon (a-C:H) films via an industrial process. Two types of these diamond-like carbon (DLC) coatings, one more flexible (f-DLC) and one more robust (r-DLC), have been investigated. Both types have been grown by a radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. Surface morphologies have been studied in detail by atomic force microscopy (AFM) and Raman spectroscopy has been used to investigate the DLC structure. Both types appeared to have very similar morphology and sp{sup 2} carbon arrangement. The average height and area for single grains have been analyzed for all depositions. A random distribution of grain heights was found for both types. The individual grain structures between the f- and r-type revealed differences: the shape for the f-DLC grains is steeper than for the r-DLC grains. By correlating the average grain heights to the average grain areas for all depositions a limited region is identified, suggesting a certain regularity during the DLC deposition mechanisms that confines both values. A growth of the sp{sup 2} carbon entities for high r-DLC depositions is revealed and connected to a structural rearrangement of carbon atom hybridizations and hydrogen content in the DLC structure.