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Sample records for stereoelectronic substituent effects

  1. Stereoelectronic Substituent Effects

    DEFF Research Database (Denmark)

    Bols, Mikael; Jensen, Henrik Helligsø

    2006-01-01

    An investigation was carried Out on the influence of the stereo-chemistry of substituents, particularly hydroxyl groups, on their electronic effects in piperidines, carbohydrates (pyranosides), and related compounds. Polar groups, such as OH, OR, and F, were found in the 3 and 4 position to be much...... more electron-withdrawing when positioned equatorially rather than axially. In contrast, little difference in electronic effects was observed from apolar groups as a result of epimerization. These observations were believed to be caused by differences in charge-dipole interactions and were used...... to explain why stereoisomeric glycosides hydrolyze with different rates. The conformational changes of hydroxylated piperidines and related compounds as a function of pH were likewise explained from the different substituent effects of axial and equatorial OH groups....

  2. Bonded exciplex formation: electronic and stereoelectronic effects.

    Science.gov (United States)

    Wang, Yingsheng; Haze, Olesya; Dinnocenzo, Joseph P; Farid, Samir; Farid, Ramy S; Gould, Ian R

    2008-12-18

    As recently proposed, the singlet-excited states of several cyanoaromatics react with pyridine via bonded-exciplex formation, a novel concept in photochemical charge transfer reactions. Presented here are electronic and steric effects on the quenching rate constants, which provide valuable support for the model. Additionally, excited-state quenching in poly(vinylpyridine) is strongly inhibited both relative to that in neat pyridine and also to conventional exciplex formation in polymers, consistent with a restrictive orientational requirement for the formation of bonded exciplexes. Examples of competing reactions to form both conventional and bonded exciplexes are presented, which illustrate the delicate balance between these two processes when their reaction energetics are similar. Experimental and computational evidence is provided for the formation of a bonded exciplex in the reaction of the singlet excited state of 2,6,9,10-tetracyanoanthracene (TCA) with an oxygen-substituted donor, dioxane, thus expanding the scope of bonded exciplexes.

  3. Stereoelectronic effects on 1H nuclear magnetic resonance chemical shifts in methoxybenzenes

    DEFF Research Database (Denmark)

    Lambert, Maja; Olsen, Lars; Jaroszewski, Jerzy W

    2006-01-01

    the Ar-OCH3 torsion out of the ring plane, resulting in large stereoelectronic effects on the chemical shift of Hpara. Conformational searches and geometry optimizations for 3-16 at the B3LYP/6-31G** level, followed by B3LYP/6-311++G(2d,2p) calculations for all low-energy conformers, gave excellent...

  4. Stereoelectronic Effect-Induced Conductance Switching in Aromatic Chain Single-Molecule Junctions.

    Science.gov (United States)

    Xin, Na; Wang, Jinying; Jia, Chuancheng; Liu, Zitong; Zhang, Xisha; Yu, Chenmin; Li, Mingliang; Wang, Shuopei; Gong, Yao; Sun, Hantao; Zhang, Guanxin; Liu, Zhirong; Zhang, Guangyu; Liao, Jianhui; Zhang, Deqing; Guo, Xuefeng

    2017-02-08

    Biphenyl, as the elementary unit of organic functional materials, has been widely used in electronic and optoelectronic devices. However, over decades little has been fundamentally understood regarding how the intramolecular conformation of biphenyl dynamically affects its transport properties at the single-molecule level. Here, we establish the stereoelectronic effect of biphenyl on its electrical conductance based on the platform of graphene-molecule single-molecule junctions, where a specifically designed hexaphenyl aromatic chain molecule is covalently sandwiched between nanogapped graphene point contacts to create stable single-molecule junctions. Both theoretical and temperature-dependent experimental results consistently demonstrate that phenyl twisting in the aromatic chain molecule produces different microstates with different degrees of conjugation, thus leading to stochastic switching between high- and low-conductance states. These investigations offer new molecular design insights into building functional single-molecule electrical devices.

  5. Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

    Directory of Open Access Journals (Sweden)

    Cesar Garcias-Morales

    2015-10-01

    Full Text Available This paper reports the synthesis of a series of piperidones 1–8 by the Mannich reaction and analysis of their structures and conformations in solution by NMR and mass spectrometry. The six-membered rings in 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones, compounds 1 and 2, adopt a chair–boat conformation, while those in 2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-ones, compounds 3–8, adopt a chair–chair conformation because of stereoelectronic effects. These stereoelectronic effects were analyzed by the 1JC–H coupling constants, which were measured in the 13C satellites of the 1H NMR spectra obtained with the hetero-dqf pulse sequence. In the solid state, these stereoelectronic effects were investigated by measurement of X-ray diffraction data, the molecular geometry (torsional bond angles and bond distances, and inter- and intramolecular interactions, and by natural bond orbital analysis, which was performed using density functional theory at the ωB97XD/6311++G(d,p level. We found that one of the main factors influencing the conformational stability of 3–8 is the interaction between the lone-pair electrons of nitrogen and the antibonding sigma orbital of C(7–Heq (nN→σ*C–H(7eq, a type of hyperconjugative interaction.

  6. Influence of stereoelectronic effects on the non-opioid analgesics gaboxadol and gaboxadol hydrochloride: Spectral and DFT study

    Science.gov (United States)

    Leenaraj, D. R.; Joe, I. Hubert

    2018-05-01

    The stereoelectronic properties of the molecular structure of most stable conformers of gaboxadol and gaboxadol hydrochloride have been studied using DFT/B3P86-LANL2DZ methodology. The energies of stable conformers of gaboxadol and gaboxadol hydrochloride are -494.2689 and -510.0117 hartrees, respectively. The stability of the molecules arising from stereoelectronic interactions, leading to its bioactivity, has been confirmed using natural bond orbital analysis. The natural bond orbital analysis of donor-acceptor (σ→σ* and n→σ*) interactions showed that the stereoelectronic hyperconjugative and anomeric interactions are exhibited in gaboxadol hydrochloride and gaboxadol, respectively. Lengthening of the axial and equatorial C-H bond lengths and natural population analysis support these results. Spectral features of gaboxadol hydrochloride have been explored by the Fourier transform infrared, Raman and Nuclear magnetic resonance spectroscopic techniques combined with density functional theory computations. NH+ … Cl- hydrogen bonding has been noticeable as a broad and strong absorption in the 2800-2400 cm-1 region. Broad peaks obtained by proton NMR are a result of the quadrupole effect of the N+ atom. Docking studies using representative GABA receptor crystal structures revealed that molecules containing azinane and isoxazole cores fit within the ligand binding domains, and the gaboxadol hydrochloride molecule shows the best binding energy with the 3D32 GABA receptor. Also, gaboxadol hydrochloride has obtained a high value of HOMO energy and a narrow HOMO- LUMO energy gap, which enhances reactivity.

  7. Towards a physical interpretation of substituent effect: Quantum chemical interpretation of Hammett substituent constants

    Science.gov (United States)

    Varaksin, Konstantin S.; Szatylowicz, Halina; Krygowski, Tadeusz M.

    2017-06-01

    Quantitative description of substituent effects is of a great importance especially in organic chemistry and QSAR-type treatments. The proposed approaches: substituent effect stabilization energy (SESE) and charge of the substituent active region (cSAR) provide substituent effect characteristics, physically independent of the Hammett's substituent constants, σ. To document abilities of these descriptors the B3LYP/6-311++G(d,p) method is employed to examine changes in properties of a reaction center Y (Y = COOH or COO- groups) and a transmitting moiety (benzene ring) due to substituent effects in a series of meta- and para-X-substituted benzoic acid and benzoate anion derivatives (X = NMe2, NH2, OH, OMe, CH3, H, F, Cl, CF3, CN, CHO, COMe, CONH2, COOH, NO2, NO). The transmitting moiety is described by aromaticity indices HOMA and NICS(1). Furthermore, an advantage of the cSAR characteristic is the ability to use it to describe both electron donating/accepting properties of a substituent as well as a reaction center. It allows demonstration of the reverse substituent effects of COOH and COO- groups on substituent X.

  8. Radiation effects on polyacetylenes having substituents

    International Nuclear Information System (INIS)

    Higashimura, Toshinobu; Tang, Ben-Zhong; Masuda, Toshio; Yamaoka, Hitoshi; Matsuyama, Tomochika.

    1985-01-01

    Effects of γ-ray irradiation on high molecular weight polyacetylenes with various substituents were studied in air and in vacuum. The molecular weights of polymers from aliphatic disubstituted acetylenes (2-octyne and 2-decyne) remarkably reduced with irradiation in air. Their G values for chain scission in air were as high as 3 - 12, whereas no degradation occurred in vacuum. The degraded polymers contain carbonyl and hydroxyl groups, and are soluble in polar solvents such as methyl ethyl ketone and acetone. In contrast, polymers of aromatic disubstituted acetylenes (1-phenyl-1-propyne and 1-chloro-2-phenylacetylene) hardly degraded in air even with irradiation up to 40 Mrad. The degradation behavior of poly(t-butylacetylene) was intermediate between those of the above aliphatic and aromatic polymers. Thus the radiolysis of polyacetylenes was found to be greatly dependent on the kind of substituents. (author)

  9. Investigation of polar and stereoelectronic effects on pure excited-state hydrogen atom abstractions from phenols and alkylbenzenes.

    Science.gov (United States)

    Pischel, Uwe; Patra, Digambara; Koner, Apurba L; Nau, Werner M

    2006-01-01

    The fluorescence quenching of singlet-excited 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by 22 phenols and 12 alkylbenzenes has been investigated. Quenching rate constants in acetonitrile are in the range of 10(8)-10(9) M(-1)s(-1) for phenols and 10(5)-10(6) M(-1)s(-1) for alkylbenzenes. In contrast to the quenching of triplet-excited benzophenone, no exciplexes are involved, so that a pure hydrogen atom transfer is proposed as quenching mechanism. This is supported by (1) pronounced deuterium isotope effects (kH/kD ca 4-6), which were observed for phenols and alkylbenzenes, and (2) a strongly endergonic thermodynamics for charge transfer processes (electron transfer, exciplex formation). In the case of phenols, linear free energy relationships applied, which led to a reaction constant of rho = -0.40, suggesting a lower electrophilicity of singlet-excited DBO than that of triplet-excited ketones and alkoxyl radicals. The reactivity of singlet-excited DBO exposes statistical, steric, polar and stereoelectronic effects on the hydrogen atom abstraction process in the absence of complications because of competitive exciplex formation.

  10. Rationalizing substituent effects in 1-azathioxanthone photophysics

    Science.gov (United States)

    Junker, Anne Kathrine R.; Just Sørensen, Thomas

    2018-01-01

    The influence of an electron donating substituent on the photophysical properties of 1-azathioxanthone dyes has been investigated using optical spectroscopy and theoretical models. The motivation behind the study is based on the fact that thioxanthones are efficient triplet sensitizers, and thus promising sensitizers for lanthanide centered emission. By adding an aza group to one of the phenyl ring systems, direct coordination to a lanthanide center becomes possible, which makes azathoixanthones great candidates as antenna chromophores in lanthanide(III) based dyes. Here, three 1-azathioxanthone derivatives have been synthesized targeting efficient triplet formation following absorption in the visible range of the spectrum. This is achieved by adding methoxy groups to the 1-azathioxanthone core. The derivatives were characterized using absorption, emission, and time-gated emission spectroscopy, where fluorescent quantum yields, singlet and triplet excited states lifetimes were determined. The experimentally determined photophysical properties of the three 1-azathioxanthone compounds are contrasted to those of the parent thioxanthone and is rationalized using the Strickler-Berg equation, Hückel MO theory, and Dewar’s rules in combination with computational chemistry. We find that the transition energies follow predictions, but that the overall photophysical properties are determined by the relative energies as well as the nature of the involved states in both the singlet and the triplet excited state manifolds.

  11. Effect of substituents on the reactivity of ninhydrin with urea

    NARCIS (Netherlands)

    Jong, Jacobus A.W.; Moret, Marc Etienne; Verhaar, Marianne C.; Hennink, Wim E.; Gerritsen, Karin G.F.; Van Nostrum, Cornelus F.

    2018-01-01

    Ninhydrin, i. e. the stable hydrate of the reactive species indanetrione, is a well-known compound used for the quantification of ammonia and amino acids. However, substituent effects on the reactivity of ninhydrin with nucleophiles are not described. In this work, the kinetics of the reaction of

  12. Substituent effects in heterogeneous catalysis--5. The steric hindrance of bulky alkyl substituents in cyclohexanone hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Chihara, T; Tanaka, K

    1979-02-01

    The steric hindrance of bulky alkyl substituents in cyclohexanone hydrogenation was demonstrated by the reactivities of 2-isopropyl and 2-tert.-butyl cyclohexanone relative to cyclohexanone in individual and competitive hydrogenation at 30/sup 0/C over alumina-supported ruthenium, rhodium, and platinum catalysts. The results indicate that the ketone adsorption onto the catalyst is sterically hindered by the alkyl substitution significantly more than the surface reaction which follows the adsorption.

  13. Substituent effect on redox potential of nitrido technetium complexes with Schiff base ligand. Theoretical calculations

    International Nuclear Information System (INIS)

    Takayama, T.; Sekine, T.; Kudo, H.

    2003-01-01

    Theoretical calculations based on the density functional theory (DFT) were performed to understand the effect of substituents on the molecular and electronic structures of technetium nitrido complexes with salen type Schiff base ligands. Optimized structures of these complexes are square pyramidal. The electron density on a Tc atom of the complex with electron withdrawing substituents is lower than that of the complex with electron donating substituents. The HOMO energy is lower in the complex with electron withdrawing substituents than that in the complex with electron donating substituents. The charge on Tc atoms is a good measure that reflects the redox potential of [TcN(L)] complex. (author)

  14. Orchestration of Structural, Stereoelectronic, and Hydrogen-Bonding Effects in Stabilizing Triplexes from Engineered Chimeric Collagen Peptides (Pro(X)-Pro(Y)-Gly)6 Incorporating 4(R/S)-Aminoproline.

    Science.gov (United States)

    Umashankara, Muddegowda; Sonar, Mahesh V; Bansode, Nitin D; Ganesh, Krishna N

    2015-09-04

    Collagens are an important family of structural proteins found in the extracellular matrix with triple helix as the characteristic structural motif. The collagen triplex is made of three left-handed polyproline II (PPII) helices with each PPII strand consisting of repetitive units of the tripeptide motif X-Y-Gly, where the amino acids X and Y are most commonly proline (Pro) and 4R-hydroxyproline (Hyp), respectively. A C4-endo pucker at X-site and C4-exo pucker at Y-site have been proposed to be the key for formation of triplex, and the nature of pucker is dependent on both the electronegativity and stereochemistry of the substituent. The present manuscript describes a new class of collagen analogues-chimeric cationic collagens-wherein both X- and Y-sites in collagen triad are simultaneously substituted by a combination of 4(R/S)-(OH/NH2/NH3(+)/NHCHO)-prolyl units and triplex stabilities measured at different pHs and in EG:H2O. Based on the results a model has been proposed with the premise that any factors which specifically favor the ring puckers of C4-endo at X-site and C4-exo at Y-site stabilize the PPII conformation and hence the derived triplexes. The pH-dependent triplex stability uniquely observed with ionizable 4-amino substituent on proline enables one to define the critical combination of factors C4-(exo/endo), intraresidue H-bonding, stereoelectronic (R/S) and n → π* interactions in dictating the triplex strength. The ionizable NH2 substituent at C4 in R/S configuration is thus a versatile probe for delineating the triplex stabilizing factors and the results have potential for designing of collagen analogues with customized properties for material and biological applications.

  15. Atropisomerism about aryl-Csp(3) bonds: the electronic and steric influence of ortho-substituents on conformational exchange in cannabidiol and linderatin derivatives.

    Science.gov (United States)

    Berber, Hatice; Lameiras, Pedro; Denhez, Clément; Antheaume, Cyril; Clayden, Jonathan

    2014-07-03

    Terpenylation reactions of substituted phenols were used to prepare cannabidiol and linderatin derivatives, and their structure and conformational behavior in solution were investigated by NMR and, for some representative examples, by DFT. VT-NMR spectra and DFT calculations were used to determine the activation energies of the conformational change arising from restricted rotation about the aryl-Csp(3) bond that lead to two unequally populated rotameric epimers. The NBO calculation was applied to explain the electronic stabilization of one conformer over another by donor-acceptor charge transfer interactions. Conformational control arises from a combination of stereoelectronic and steric effects between substituents in close contact with each other on the two rings of the endocyclic epoxide atropisomers. This study represents the first exploration of the stereoelectronic origins of atropisomerism around C(sp(2))-C(sp(3)) single bonds through theoretical calculations.

  16. Effect of substituent structure on pyrimidine electrophilic substitution

    CSIR Research Space (South Africa)

    Van der Westhuyzen, CW

    2007-01-01

    Full Text Available In an investigation into the electrophilic nitrosation reactions of a series of 4,6-disubstituted pyrimidine derivatives, a subtle interplay between the electronic nature of the C-4 and C-6 substituents and reactivity was found where these were...

  17. Effects of the Substituents of Boron Atoms on Conjugated Polymers Containing B←N Units.

    Science.gov (United States)

    Liu, Jun; Wang, Tao; Dou, Chuandong; Wang, Lixiang

    2018-06-15

    Organoboron chemistry is a new tool to tune the electronic structures and properties of conjugated polymers, which are important for applications in organic opto-electronic devices. To investigate the effects of substituents of boron atoms on conjugated polymers, we synthesized three conjugated polymers based on double B←N bridged bipyridine (BNBP) with various substituents on the boron atoms. By changing the substituents from four phenyl groups and two phenyl groups/two fluorine atoms to four fluorine atoms, the BNBP-based polymers show the blue-shifted absorption spectra, decreased LUMO/HOMO energy levels and enhanced electron affinities, as well as the increased electron mobilities. Moreover, these BNBP-based polymers can be used as electron acceptors for all-polymer solar cells. These results demonstrate that the substituents of boron atoms can effectively modulate the electronic properties and applications of conjugated polymers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Towards physical interpretation of substituent effects: the case of N- and C3-substituted pyrrole derivatives

    Czech Academy of Sciences Publication Activity Database

    Zborowski, K. K.; Szatylowicz, H.; Stasyuk, Olga A.; Krygowski, T. M.

    2017-01-01

    Roč. 28, č. 4 (2017), s. 1223-1227 ISSN 1040-0400 Institutional support: RVO:61388963 Keywords : substituent effect * pyrrole derivatives * Hammett equation * charges of the substituent active region Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 1.582, year: 2016 https://link.springer.com/article/10.1007%2Fs11224-017-0938-7

  19. The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI-MSn.

    Science.gov (United States)

    Cui, Xiaoyan; Sun, Can; Zhao, Pei; Wang, Yanyan; Guo, Yanchun; Zhao, Yufen; Cao, Shuxia

    2018-04-01

    The fragmentation pathways of pentacoordinated phenoxyspirophosphoranes were investigated in the positive mode by electrospray ionization multistage mass spectrometry. The results demonstrate that the sodium adducts of the title compounds undergo two competitive fragmentation pathways, and the fragmentation patterns are heavily dependent on the various substituent patterns at the phenolic group. An electron-withdrawing substituent at the ortho-position always results in the removal of a corresponding phenol analogue, while cleavage by spiroring opening becomes the predominant fragmentation pathway if an electron-donating substituent is at the phenolic group. The substituent effects on the competitive fragmentation pathways were further elucidated by theoretical calculations, single crystal structure analysis, and high-resolution mass spectrometry. The results contribute to the understanding of the gas-phase fragmentation reactions and the structure identification of spirophosphorane analogues by electrospray ionization multistage mass spectrometry. Copyright © 2018 John Wiley & Sons, Ltd.

  20. Substituent effects on geometric and electronic properties of iron tetraphenylporphyrin: a DFT investigation.

    Science.gov (United States)

    Wei, Lu; She, Yuanbin; Yu, Yanmin; Yao, Xiaoqian; Zhang, Suojiang

    2012-06-01

    To investigate the effects of the substituents, substituent positions and axial chloride ligand on the geometric and electronic properties of the iron tetraphenylporphyrin (FeTPP), a series of the substituented iron tetraphenylporphyrins and their chlorides, FeT(o/p-R)PP and FeT(o/p-R)PPCl (R = -H, -Cl, -NO(2), -OH, -OCH(3)), were systematically calculated without any symmetry constraint by using DFT method. For geometric structure, the substituent position and axial Cl ligand change the configuration of the iron porphyrin obviously. The ortho-substituents prefer making the phenyls perpendicular to the porphyrin ring; the axial chloride draws the central Fe ion ~0.500 Å out of the porphyrin plane toward the ligand. With regard to electronic properties, it is found that E(LUMO) could be related to the catalytic activity. The electron-withdrawing group always lowers the energies of both frontier orbitals, while the electron-donating one heightens them simultaneously, but they affect the E(HOMO) and E(LUMO) in the same sequence, -NO(2) < -Cl < -H < -OH < -OCH(3). The substituent effects on the central Fe ion were explored by calculating NBO charge distribution, spin density and natural electron configuration.

  1. Substituent Effects on the Hydrogen Bonding Between Phenolate and HF, H2O and NH3

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    B3LYP/6-31+g(d) calculations were performed on the hydrogen bonded complexes between substituted phenolates and HF, H2O as well as NH3. It was found that some properties of the non-covalent complexes, including the interaction energies, donor-acceptor (host-guest) distances, bond lengths, and vibration frequencies, could show well-defined substituent effects. Thus, from the substituent studies we can not only understand the mechanism of a particular non-covalent interaction better, but also easily predict the interaction energies and structures of a particular non-covalent complex, which might otherwise be very hard or resource-consuming to be known. This means that substituent effect is indeed a useful tool to be used in supramolecular chemistry and therefore, many valuable studies remain to be carried out.

  2. The effects of characteristics of substituents on toxicity of the nitroaromatics: HiT QSAR study

    Science.gov (United States)

    Kuz'min, Victor E.; Muratov, Eugene N.; Artemenko, Anatoly G.; Gorb, Leonid; Qasim, Mohammad; Leszczynski, Jerzy

    2008-10-01

    The present study applies the Hierarchical Technology for Quantitative Structure-Activity Relationships (HiT QSAR) for (i) evaluation of the influence of the characteristics of 28 nitroaromatic compounds (some of which belong to a widely known class of explosives) as to their toxicity; (ii) prediction of toxicity for new nitroaromatic derivatives; (iii) analysis of the effects of substituents in nitroaromatic compounds on their toxicity in vivo. The 50% lethal dose concentration for rats (LD50) was used to develop the QSAR models based on simplex representation of molecular structure. The preliminary 1D QSAR results show that even the information on the composition of molecules reveals the main tendencies of changes in toxicity. The statistic characteristics for partial least squares 2D QSAR models are quite satisfactory ( R 2 = 0.96-0.98; Q 2 = 0.91-0.93; R 2 test = 0.89-0.92), which allows us to carry out the prediction of activity for 41 novel compounds designed by the application of new combinations of substituents represented in the training set. The comprehensive analysis of toxicity changes as a function of substituent position and nature was carried out. Molecular fragments that promote and interfere with toxicity were defined on the basis of the obtained models. It was shown that the mutual influence of substituents in the benzene ring plays a crucial role regarding toxicity. The influence of different substituents on toxicity can be mediated via different C-H fragments of the aromatic ring.

  3. Substituent effects in the ortho position: Model compounds with a removed reaction centre

    Czech Academy of Sciences Publication Activity Database

    Böhm, S.; Exner, Otto

    2007-01-01

    Roč. 81, 5/6 (2007), s. 993-1006 ISSN 0137- 5083 Institutional research plan: CEZ:AV0Z40550506 Keywords : substituent effect * density functional theory * ortho effect * steric effect Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.483, year: 2007

  4. Delocalization does not always stabilize : a quantum chemical analysis of -substituent effects on 54 alkyl and vinyl cations

    NARCIS (Netherlands)

    Alem, van K.; Lodder, G.; Zuilhof, H.

    2002-01-01

    The effects of -substituents on alkyl and vinyl cations are studied using high-level ab initio calculations. The geometries, stabilities, and electronic properties of 27 alkyl cations and 27 vinyl cations with -substituents are computed at the B3LYP/6-311 G(d,p), MP2/6-311 G(d,p), and CBS-Q levels.

  5. Substituent effects of the alkyl groups: Polarity vs. polarizability

    Czech Academy of Sciences Publication Activity Database

    Exner, Otto; Böhm, S.

    -, č. 17 (2007), s. 2870-2876 ISSN 1434-193X Institutional research plan: CEZ:AV0Z40550506 Keywords : density functional calculations * hyperconjugation * inductive effect * polarizability Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.914, year: 2007

  6. Theoretical investigation of substituent effects on the dihydroazulene/vinylheptafulvene photoswitch

    DEFF Research Database (Denmark)

    Hansen, Mia Harring; Elm, Jonas; Olsen, Stine Tetzschner

    2016-01-01

    We have investigated the effects of substituents on the properties of the dihydroazulene/vinylheptafulvene photoswitch. The focus is on the changes of the thermochemical properties by placing electron withdrawing and donating groups on the monocyano and dicyano structures of the parent dihydroazu......We have investigated the effects of substituents on the properties of the dihydroazulene/vinylheptafulvene photoswitch. The focus is on the changes of the thermochemical properties by placing electron withdrawing and donating groups on the monocyano and dicyano structures of the parent...... on the substitution pattern, and based on these results, we have outlined molecular design considerations for obtaining new desired target structures exhibiting long energy storage times. Selected candidate systems have also been investigated in terms of optical properties to elucidate how sensitive the absorption...

  7. Topological Substituent Descriptors

    Directory of Open Access Journals (Sweden)

    Mircea V. DIUDEA

    2002-12-01

    Full Text Available Motivation. Substituted 1,3,5-triazines are known as useful herbicidal substances. In view of reducing the cost of biological screening, computational methods are carried out for evaluating the biological activity of organic compounds. Often a class of bioactives differs only in the substituent attached to a basic skeleton. In such cases substituent descriptors will give the same prospecting results as in case of using the whole molecule description, but with significantly reduced computational time. Such descriptors are useful in describing steric effects involved in chemical reactions. Method. Molecular topology is the method used for substituent description and multi linear regression analysis as a statistical tool. Results. Novel topological descriptors, XLDS and Ws, based on the layer matrix of distance sums and walks in molecular graphs, respectively, are proposed for describing the topology of substituents linked on a chemical skeleton. They are tested for modeling the esterification reaction in the class of benzoic acids and herbicidal activity of 2-difluoromethylthio-4,6-bis(monoalkylamino-1,3,5-triazines. Conclusions. Ws substituent descriptor, based on walks in graph, satisfactorily describes the steric effect of alkyl substituents behaving in esterification reaction, with good correlations to the Taft and Charton steric parameters, respectively. Modeling the herbicidal activity of the seo of 1,3,5-triazines exceeded the models reported in literature, so far.

  8. Substituent effects on the optical properties of naphthalenediimides: A frontier orbital analysis across the periodic table.

    Science.gov (United States)

    Mulder, Joshua R; Guerra, Célia Fonseca; Slootweg, J Chris; Lammertsma, Koop; Bickelhaupt, F Matthias

    2016-01-15

    A comprehensive theoretical treatment is presented for the electronic excitation spectra of ca. 50 different mono-, di-, and tetrasubstituted naphthalenediimides (NDI) using time-dependent density functional theory (TDDFT) at ZORA-CAM-B3LYP/TZ2P//ZORA-BP86/TZ2P with COSMO for simulating the effect of dichloromethane (DCM) solution. The substituents -XHn are from groups 14-17 and rows 2-5 of the periodic table. The lowest dipole-allowed singlet excitation (S0 -S1 ) of the monosubstituted NDIs can be tuned from 3.39 eV for -F to 2.42 eV for -TeH, while the S0 -S2 transition is less sensitive to substitution with energies ranging between 3.67 eV for -CH3 and 3.44 eV for -SbH2 . In the case of NDIs with group-15 and -16 substituents, the optical transitions strongly depend on the extent to which -XHn is planar or pyramidal as well as on the possible formation of intramolecular hydrogen bonds. The accumulative effect of double and quadruple substitution leads in general to increasing bathochromic shifts, but the increased steric hindrance in tetrasubstituted NDIs can lead to deformations that diminish the effectiveness of the substituents. Detailed analyses of the Kohn-Sham orbital electronic structure in monosubstituted NDIs reveal the mesomeric destabilization of the HOMO as the primary cause of the bathochromic shift of the S0-S1 transition. © 2015 Wiley Periodicals, Inc.

  9. Electronic effects of substituents in o-hydroxyazo compounds and azoquinone-hydrazone tautomerism

    International Nuclear Information System (INIS)

    Raikhshtat, M.M.; Zhogina, V.V.; Savvin, S.B.

    1987-01-01

    The authors have investigated the electronic structure of p-substituted phenylazonaphthol and some o-hydroxyazo compounds of the general structure X-N=N-Y. The influence of structural changes of the X and Y radicals on the electronic structure of the o-hydroxyazo group was studied. The results are compared with experimental data, obtained by NMR 13 C, by tautomerism of these compounds in solution in CDCl 3 . The electronic structure of o-hydroxyazo compounds was calculated by the PPDP/2 method. This method satisfactorily describes the electronic structure of organic compounds and correctly reproduces electronic effects of the substituents

  10. Substituent Effects on the Stability of Thallium and Phosphorus Triple Bonds: A Density Functional Study.

    Science.gov (United States)

    Lu, Jia-Syun; Yang, Ming-Chung; Su, Ming-Der

    2017-07-05

    Three computational methods (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP and B3LYP/LANL2DZ+dp) were used to study the effect of substitution on the potential energy surfaces of RTl≡PR (R = F, OH, H, CH₃, SiH₃, SiMe(Si t Bu₃)₂, Si i PrDis₂, Tbt (=C₆H₂-2,4,6-(CH(SiMe₃)₂)₃), and Ar* (=C₆H₃-2,6-(C₆H₂-2, 4,6- i -Pr₃)₂)). The theoretical results show that these triply bonded RTl≡PR compounds have a preference for a bent geometry (i.e., ∠R⎼Tl⎼P ≈ 180° and ∠Tl⎼P⎼R ≈ 120°). Two valence bond models are used to interpret the bonding character of the Tl≡P triple bond. One is model [I], which is best described as TlP. This interprets the bonding conditions for RTl≡PR molecules that feature small ligands. The other is model [II], which is best represented as TlP. This explains the bonding character of RTl≡PR molecules that feature large substituents. Irrespective of the types of substituents used for the RTl≡PR species, the theoretical investigations (based on the natural bond orbital, the natural resonance theory, and the charge decomposition analysis) demonstrate that their Tl≡P triple bonds are very weak. However, the theoretical results predict that only bulkier substituents greatly stabilize the triply bonded RTl≡PR species, from the kinetic viewpoint.

  11. DFT study on the effect of exocyclic substituents on the proton affinity of 1-methylimidazole

    International Nuclear Information System (INIS)

    Liu, Haining; Bara, Jason E.; Turner, C. Heath

    2013-01-01

    Highlights: • DFT calculations are used to predict the proton affinity of 1-methylimidazoles. • The electron-withdrawing groups dominate the predicted proton affinity. • The effects of multiple substituents on the proton affinity can be accurately predicted. • Large compound libraries can be screened for imidazoles with tailored reactivity. - Abstract: A deeper understanding of the acid/base properties of imidazole derivatives will aid the development of solvents, polymer membranes and other materials that can be used for CO 2 capture and acid gas removal. In this study, we employ density functional theory calculations to investigate the effect of various electron-donating and electron-withdrawing groups on the proton affinity of 1-methylimidazole. We find that electron-donating groups are able to increase the proton affinity relative to 1-methylimidazole, i.e., making the molecule more basic. In contrast, electron-withdrawing groups cause a decrease of the proton affinity. When multiple substituents are present, their effects on the proton affinity were found to be additive. This finding offers a quick approach for predicting and targeting the proton affinities of this series of molecules, and we show the strong correlation between the calculated proton affinities and experimental pK a values

  12. Kinetic and mechanisms of methanimine reactions with singlet and triplet molecular oxygen: Substituent and catalyst effects

    Science.gov (United States)

    Asgharzadeh, Somaie; Vahedpour, Morteza

    2018-06-01

    Methanimine reaction with O2 on singlet and triplet potential energy surfaces are investigated using B3PW91, M06-2X, MP2 and CCSD(T) methods. Thermodynamic and kinetic parameters are calculated at M06-2X method. The most favorable channel involves H-abstraction of CH2NH+O2 to the formation of HCN + H2O2 products via low level energy barrier. The catalytic effect of water molecule on HCN + H2O2 products pathway are investigated. Result shows that contribution of water molecule using complex formation with methanimine can decreases barrier energy of transition state and the reaction rate increases. Also, substituent effect of fluorine atom as deactivating group are investigated on the main reaction pathway.

  13. Effect of substituents on electronic properties, thin film structure and device performance of dithienothiophene-phenylene cooligomers

    International Nuclear Information System (INIS)

    Zhang Shiming; Guo Yunlong; Xi Hongxia; Di Chongan; Yu Jian; Zheng Kai; Liu Ruigang; Zhan Xiaowei; Liu Yunqi

    2009-01-01

    Dithienothiophene-phenylene cooligomers with n-hexyloxy or n-dodecyloxy substituents have been synthesized and compared to the previously reported unsubstituted parent compound. The effect of substituents on the thermal, electronic, optical, thin film structure and field-effect transistor (OFET) properties was investigated. Structural phase transitions from highly-ordered nanocrystalline to liquid crystalline were observed at 241 and 213 deg. C for n-hexyloxy- and n-dodecyloxy-substituted compounds respectively, different from the parent compound. For the alkoxy-substituted compounds, the absorption spectra in thin film blue shift 50 nm, while the fluorescence spectra in thin film red shift 88-100 nm compared to those in solution. The OFET devices based on the alkoxy-substituted compounds exhibit mobilities as high as ca 0.02 cm 2 V -1 s -1 and their performance is sensitive to the alkoxy substituents and substrate temperatures

  14. Effects of para-substituents of styrene derivatives on their chemical reactivity on platinum nanoparticle surfaces

    Science.gov (United States)

    Hu, Peiguang; Chen, Limei; Deming, Christopher P.; Lu, Jia-En; Bonny, Lewis W.; Chen, Shaowei

    2016-06-01

    Stable platinum nanoparticles were successfully prepared by the self-assembly of para-substituted styrene derivatives onto the platinum surfaces as a result of platinum-catalyzed dehydrogenation and transformation of the vinyl groups to the acetylene ones, forming platinum-vinylidene/-acetylide interfacial bonds. Transmission electron microscopic measurements showed that the nanoparticles were well dispersed without apparent aggregation, suggesting sufficient protection of the nanoparticles by the organic capping ligands, and the average core diameter was estimated to be 2.0 +/- 0.3 nm, 1.3 +/- 0.2 nm, and 1.1 +/- 0.2 nm for the nanoparticles capped with 4-tert-butylstyrene, 4-methoxystyrene, and 4-(trifluoromethyl)styrene, respectively, as a result of the decreasing rate of dehydrogenation with the increasing Taft (polar) constant of the para-substituents. Importantly, the resulting nanoparticles exhibited unique photoluminescence, where an increase of the Hammett constant of the para-substituents corresponded to a blue-shift of the photoluminescence emission, suggesting an enlargement of the HOMO-LUMO band gap of the nanoparticle-bound acetylene moieties. Furthermore, the resulting nanoparticles exhibited apparent electrocatalytic activity towards oxygen reduction in acidic media, with the best performance among the series of samples observed with the 4-tert-butylstyrene-capped nanoparticles due to an optimal combination of the nanoparticle core size and ligand effects on the bonding interactions between platinum and oxygen species.Stable platinum nanoparticles were successfully prepared by the self-assembly of para-substituted styrene derivatives onto the platinum surfaces as a result of platinum-catalyzed dehydrogenation and transformation of the vinyl groups to the acetylene ones, forming platinum-vinylidene/-acetylide interfacial bonds. Transmission electron microscopic measurements showed that the nanoparticles were well dispersed without apparent

  15. The proton transfer reaction in malonaldehyde derivatives: Substituent effects and quasi-aromaticity of the proton bridge

    International Nuclear Information System (INIS)

    Palusiak, Marcin; Simon, Silvia; Sola, Miquel

    2007-01-01

    The proton transfer in malonaldehyde and in some of its derivatives have been considered in order to study the interrelation between the reaction barrier and the π-delocalization in the quasi-ring. A set of simple and mostly common substituents having different properties in resonance effect according to values of substituents constants were chosen in order to simulate the influence of substitution in position 2 or in position 1 (or 3) of malonaldehyde on the quasi-aromaticity and H-bonding. The following substituents have been taken into consideration: NO, NO 2 , CN, CHO, F, H, CH 3 , OCH 3 , OH, and NH 2 . Our results show that when the substituent is attached at position 2 of the quasi-ring, the resonance effect predominates over the field/inductive effect which leads to changes in H-bonding and quasi-aromaticity of the ring motif, while in the case of 1(3) substitution the field/inductive effect is significantly more effective influencing the HB strength, and thus, the proton transfer barrier. Somehow counterintuitively, for the 1(3) substituted systems, the most stable isomer is the one having the weakest HB and lower aromaticity. The reason for this surprising behaviour is discussed

  16. Substituent Effects Dehalogenation of Aryl Bromides with NaAlH2(OCH2CH2OCH3)2

    Czech Academy of Sciences Publication Activity Database

    Czakoová, Marie; Hetflejš, Jiří; Včelák, Jaroslav

    2001-01-01

    Roč. 72, č. 2 (2001), s. 277-287 ISSN 0133-1736 R&D Projects: GA ČR GA203/97/1173 Institutional research plan: CEZ:AV0Z4072921 Keywords : substituent effects * aryl bromides * Co-assisted debromination Subject RIV: CC - Organic Chemistry Impact factor: 0.475, year: 2001

  17. Bipolar Alq3-based complexes: Effect of hole-transporting substituent on the properties of Alq3-center

    International Nuclear Information System (INIS)

    Luo Jianxin; Lu Mangeng; Yang Chaolong; Tong Bihai; Liang Liyan

    2012-01-01

    Two bipolar Alq 3 -based complexes, tris{5-[(carbazole-9'-yl)methyl]-8-hydroxyquinoline} aluminum (Al(CzHQ) 3 ) and tris{5-[(phenothiazine-9'-yl)methyl]-8-hydroxyquinoline} aluminum (Al(PHQ) 3 ), involving an Alq 3 -center and three hole-transporting substituents (carbazole or phenothiazine), were prepared and characterized. Effects of hole-transporting substituent on the properties of Alq 3 -center were investigated in detail. It is found that the two complexes have improved hole-transporting performance and appropriate thermal stability (the 5%-weight-loss temperatures T 5% >260 °C). Photoluminescence (PL) spectra indicate that both energy transfer and electron transfer can take place simultaneously in the PL process of these complexes. Both thermodynamics and dynamics of the electron transfer were studied and corresponding parameters were calculated. Energy transfer is favorable for the PL of Alq 3 -center, while electron transfer is unfavorable for the PL of Alq 3 -center. These results will be useful to explore novel OLEDs material with increased efficiency. - Highlights: ► Effects of substituent on the properties of Alq 3 -center were investigated. ► Energy transfer and electron transfer can transfer from substituent to Alq 3 -center. ► The thermodynamics and dynamics of electron transfer were studied. ► The mechanisms of PL and EL of Al(CzHQ) 3 were studied and compared with each other.

  18. Interplay of stereoelectronic and enviromental effects in tuning the structural and magnetic properties of a prototypical spin probe: further insights from a first principle dynamical approach.

    Science.gov (United States)

    Pavone, Michele; Cimino, Paola; De Angelis, Filippo; Barone, Vincenzo

    2006-04-05

    The nitrogen isotropic hyperfine coupling constant (hcc) and the g tensor of a prototypical spin probe (di-tert-butyl nitroxide, DTBN) in aqueous solution have been investigated by means of an integrated computational approach including Car-Parrinello molecular dynamics and quantum mechanical calculations involving a discrete-continuum embedding. The quantitative agreement between computed and experimental parameters fully validates our integrated approach. Decoupling of the structural, dynamical, and environmental contributions acting onto the spectral observables allows an unbiased judgment of the role played by different effects in determining the overall experimental observables and highlights the importance of finite-temperature vibrational averaging. Together with their intrinsic interest, our results pave the route toward more reliable interpretations of EPR parameters of complex systems of biological and technological relevance.

  19. Stereoelectronic control in peptide bond formation. Ab initio calculations and speculations on the mechanism of action of serine proteases.

    Science.gov (United States)

    Gorenstein, D G; Taira, K

    1984-01-01

    Ab initio molecular orbital calculations have been performed on the reaction profile for the addition/elimination reaction between ammonia and formic acid, proceeding via a tetrahedral intermediate: NH3 + HCO2H----H2NCH(OH)2----NH2CHO + H2O. Calculated transition state energies for the first addition step of the reaction revealed that a lone pair on the oxygen of the OH group, which is antiperiplanar to the attacking nitrogen, stabilized the transition state by 3.9 kcal/mol, thus supporting the hypothesis of stereoelectronic control for this reaction. In addition, a secondary, counterbalancing stereoelectronic effect stabilizes the second step, water elimination, transition state by 3.1 kcal/mol if the lone pair on the leaving water oxygen is not antiperiplanar to the C-N bond. The best conformation for the transition states was thus one with a lone pair antiperiplanar to the adjacent scissile bond and also one without a lone-pair orbital on the scissile bond oxygen or nitrogen antiperiplanar to the adjacent polar bond. The significance of these stereoelectronic effects for the mechanism of action of serine proteases is discussed. PMID:6394065

  20. Substituent effects on furan-phenylene copolymer for photovoltaic improvement: A density functional study

    Science.gov (United States)

    Janprapa, Nuttaporn; Vchirawongkwin, Viwat; Kritayakornupong, Chinapong

    2018-06-01

    The structural, electronic and photovoltaic properties of furan-phenylene copolymer ((Fu-co-Ph)4) and its derivatives were evaluated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The calculated band gaps of pristine furan and phenylene are in good agreement with the available experimental data. The lower band gap value of 2.72 eV was obtained from -NO2 and -NHCH3 substituents, leading to broader solar absorption range. With respected to the reorganization energy, -OCH3, -NHCH3, -OH, -SCH3, -CH3, -CF3, -NO2, and -F substituted (Fu-co-Ph)4 structures were classified as better electron donor materials. For combination with PC61BM, -NO2, -CN, -CF3 and -F functionalized copolymers demonstrated significantly higher open circuit voltage (Voc) values ranging from 1.07 to 2.10 eV. Our results revealed that electron withdrawing group substitution on furan-phenylene copolymers was an effective way for improving electronic and optical properties of donor materials used in photovoltaic applications.

  1. The substituent and solvent effects on the antioxidant activity of the ferulic acid derivations

    International Nuclear Information System (INIS)

    Najafi, M.; Bukhari, S.A.

    2014-01-01

    The antioxidant activity of ortho and meta substituted ferulic acid derivatives have been investigated in the gas phase and water. The reaction enthalpies of antioxidant activity of studied derivatives have been calculated and compared with corresponding values of ferulic acid. Results show that EWG substituents increase the BDE, IP, while EDG ones cause a rise in the PA. The ferulic acid derivatives with lowest BDE, IP and PA values were identified as the compounds with high antioxidant activity. Results show that the substituents at ortho position have high potential for synthesis of novel ferulic acid derivatives. Results show that ferulic acid derivatives can process their protective role via HAT and SPLET mechanism in gas phase and solvent, respectively. The calculated reaction enthalpies of the substituted ferulic acids have linear dependences with Hammett constants and EHOMO that can be utilized in the selection of suitable substituents for the synthesis of novel antioxidants based on ferulic acid. (author)

  2. Effects of p-substituents on electrochemical CO oxidation by Rh porphyrin-based catalysts.

    Science.gov (United States)

    Yamazaki, Shin-ichi; Yamada, Yusuke; Takeda, Sahori; Goto, Midori; Ioroi, Tsutomu; Siroma, Zyun; Yasuda, Kazuaki

    2010-08-21

    Electrochemical CO oxidation by several carbon-supported rhodium tetraphenylporphyrins with systematically varied meso-substituents was investigated. A quantitative analysis revealed that the p-substituents on the meso-phenyl groups significantly affected CO oxidation activity. The electrocatalytic reaction was characterized in detail based on the spectroscopic and X-ray structural results as well as electrochemical analyses. The difference in the activity among Rh porphyrins is discussed in terms of the properties of p-substituents along with a proposed reaction mechanism. Rhodium tetrakis(4-carboxyphenyl)porphyrin (Rh(TCPP)), which exhibited the highest activity among the porphyrins tested, oxidized CO at a high rate at much lower potentials (means that CO is electrochemically oxidized by this catalyst when a slight overpotential is applied during the operation of a proton exchange membrane fuel cell. This catalyst exhibited little H(2) oxidation activity, in contrast to Pt-based catalysts.

  3. Effect of substituents on polarizability and hyperpolarizability values of benzimidazole metal complexes

    Energy Technology Data Exchange (ETDEWEB)

    Praveen, P. A.; Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin films Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli - 620 024, Tamilnadu (India)

    2016-05-23

    In this report, the polarizability and first and second order hyperpolarizability values of bis benzimidazole Zn(II)-2R and bis benzimidazole Cd(II)-2R complexes, with different electron donating moieties R (R= Cl, Br, I, Acetate) were calculated using time dependent Hartree-Fock (TDHF) formalism embedded in MOPAC2012 package. Further the role of substituents on polarizability and hyperpolarizability values is investigated for the first time by analyzing the frontier molecular orbitals of the complexes with respect to the electronegativity of the substituents. It is found that the increase in electronegativity of the substituents correspondingly increases the energy gap of the molecules, which in turn reduces the polarizability values of both Zn and Cd benzimidazole complexes. Similarly, increase in electronegativity reduces the electric quadrupole moments of both the metal complexes, which in turn reduces the hyperpolarizability values.

  4. Substituent Effects on the Hydrogen Bonding between 4-Substituted Phenols and HF, H2O, NH3

    Institute of Scientific and Technical Information of China (English)

    程宇辉; 傅尧; 刘磊; 郭庆祥

    2003-01-01

    Density function theory UB3LYP/6-31+g(d) calculations were performed to study the hydrogen bonds between para-substituted phenols and HF, H2O, or NH3. It revealed that many properties of the non-covalent complexes, such as the interaction energies, donor-acceptor distances, bond lengths and vibration frequencies, showed well-defined substituent effects. Therefore, from the substituent effects not only the mechanism of a certain non-covalent interaction can be better understood, but also the interaction energies and structures of a certain non-covalent complex, which otherwise might be very hard or resource-consuming to estimate, can be easily predicted.

  5. Substituent effects on the excited states of phenyl-capped phenylene vinylene tetramers

    NARCIS (Netherlands)

    Candeias, L.P.; Gelinck, G.H.; Piet, J.J.; Piris, J.; Wegewijs, B.; Peeters, E.; Wildeman, J.; Hadziioannou, G.; Müllen, K.

    2001-01-01

    The singlet and triplet excited states of phenyl-capped tetramers of phenylene vinylene with different alkyl, alkoxy or cyano substituents, were investigated in benzene solution. The lowest singlet states were studied by laser flash-photolysis with time-resolved microwave conductivity and

  6. Substituent Inductive Effects on the Electrochemical Oxidation of Flavonoids Studied by Square Wave Voltammetry and Ab Initio Calculations.

    Science.gov (United States)

    Arroyo-Currás, Netzahualcóyotl; Rosas-García, Víctor M; Videa, Marcelo

    2016-10-27

    Flavonoids are natural products commonly found in the human diet that show antioxidant, anti-inflammatory and anti-hepatotoxic activities. These nutraceutical properties may relate to the electrochemical activity of flavonoids. To increase the understanding of structure-electrochemical activity relations and the inductive effects that OH substituents have on the redox potential of flavonoids, we carried out square-wave voltammetry experiments and ab initio calculations of eight flavonoids selected following a systematic variation in the number of hydroxyl substituents and their location on the flavan backbone: three flavonols, three anthocyanidins, one anthocyanin and the flavonoid backbone flavone. We compared the effect that the number of -OH groups in the ring B of flavan has on the oxidation potential of the flavonoids considered, finding linear correlations for both flavonols and anthocyanidins ( R 2 = 0.98 ). We analyzed the effects that position and number of -OH substituents have on electron density distributions via ab initio quantum chemical calculations. We present direct correlations between structural features and oxidation potentials that provide a deeper insight into the redox chemistry of these molecules.

  7. Pentiptycene-derived light-driven molecular brakes: substituent effects of the brake component.

    Science.gov (United States)

    Sun, Wei-Ting; Huang, Yau-Ting; Huang, Guan-Jhih; Lu, Hsiu-Feng; Chao, Ito; Huang, Shou-Ling; Huang, Shing-Jong; Lin, Ying-Chih; Ho, Jinn-Hsuan; Yang, Jye-Shane

    2010-10-11

    Five pentiptycene-derived stilbene systems (1 R; R = H, OM, NO, Pr, and Bu) have been prepared and investigated as light-driven molecular brakes that have different-sized brake components (1 Hbrake component in the trans form ((E)-1 R), which corresponds to the brake-off state. When the brake is turned on by photoisomerization to the cis form ((Z)-1 R), the pentiptycene rotation can be arrested on the NMR spectroscopic timescale at temperatures that depend on the brake component. In the cases of (Z)-1 NO, (Z)-1 Pr, and (Z)-1 Bu, the rotation is nearly blocked (k(rot)=2-6 s(-1)) at 298 K. It is also demonstrated that the rotation is slower in [D(6)]DMSO than in CD(2)Cl(2). A linear relationship between the free energies of the rotational barrier and the steric parameter A values is present only for (Z)-1 H, (Z)-1 OM, and (Z)-1 NO, and it levels off on going from (Z)-1 NO to (Z)-1 Pr and (Z)-1 Bu. DFT calculations provide insights into the substituent effects in the rotational ground and transition states. The molar reversibility of the E-Z photoswitching is up to 46%, and both the E and Z isomers are stable under the irradiation conditions. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Substituent effects on the redox states of locally functionalized single-walled carbon nanotubes revealed by in situ photoluminescence spectroelectrochemistry.

    Science.gov (United States)

    Shiraishi, Tomonari; Shiraki, Tomohiro; Nakashima, Naotoshi

    2017-11-09

    Single-walled carbon nanotubes (SWNTs) with local chemical modification have been recognized as a novel near infrared (NIR) photoluminescent nanomaterial due to the emergence of a new red-shifted photoluminescence (PL) with enhanced quantum yields. As a characteristic feature of the locally functionalized SWNTs (lf-SWNTs), PL wavelength changes occur with the structural dependence of the substituent structures in the modified aryl groups, showing up to a 60 nm peak shift according to an electronic property difference of the aryl groups. Up to now, however, the structural effect on the electronic states of the lf-SWNTs has been discussed only on the basis of theoretical calculations due to the very limited amount of modifications. Herein, we describe the successfully-determined electronic states of the aryl-modified lf-SWNTs with different substituents (Ar-X SWNTs) using an in situ PL spectroelectrochemical method based on electrochemical quenching of the PL intensities analyzed by the Nernst equation. In particular, we reveal that the local functionalization of (6,5)SWNTs induced potential changes in the energy levels of the HOMO and the LUMO by -23 to -38 meV and +20 to +22 meV, respectively, compared to those of the pristine SWNTs, which generates exciton trapping sites with narrower band gaps. Moreover, the HOMO levels of the Ar-X SWNTs specifically shift in a negative potential direction by 15 meV according to an enhancement of the electron-accepting property of the substituents in the aryl groups that corresponds to an increase in the Hammet substituent constants, suggesting the importance of the dipole effect from the aryl groups on the lf-SWNTs to the level shift of the frontier orbitals. Our method is a promising way to characterize the electronic features of the lf-SWNTs.

  9. Study on effect of substituents in α positron of N,N-diethylamides by nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Martins, M.A.P.

    1982-01-01

    The effect of a substituent in the α position of some N,N-diethylamides, through the 1 H and 13 C n.m.r. spectroscopy is studied. Eight N,N-diethylamides having the structure: Y-CH 2 -C(O) - NEt 2 , where Y=H, Me, Cl, Br, I, OMe, SMe, and NMe 2 were prepared by usual procedures; all these compounds were characterized by their 1 H and 13 C n.m.r. and infrared spectra, as well as by their elementary analysis. (M.J.C.) [pt

  10. Theoretical research on effects of substituents and the solvent on quadruple hydrogen bonded complexes

    Directory of Open Access Journals (Sweden)

    Lingjia Xu

    2007-04-01

    Full Text Available Semiempirical AM1 and INDO/CIS methods were used to study the structures and spectroscopy of hydrogen bonded complexes formed by the oligophenyleneethynylene (monomer A with isophthalic acid (monomer B. The binding energies of the complexes are lowered by increasing electron-donating abilities of the substituents near the hydrogen bonds on monomer A. The first absorptions in the electronic spectra and the vibration frequencies of the N-H bonds in the IR spectra for the complexes are both red-shifted compared with those of the monomers. The presence of dimethylsulfoxide (DMSO can reduce the binding energy of the complex through hydrogen bonding. This results in a blue-shift for the first absorption in the electronic spectrum and red-shift for the vibration frequencies of the N-H bonds in the IR spectrum of the complex.

  11. Dual fluorescence of excited state intra-molecular proton transfer of HBFO: mechanistic understanding, substituent and solvent effects.

    Science.gov (United States)

    Yang, Wenjing; Chen, Xuebo

    2014-03-07

    A combined approach of the multiconfigurational perturbation theory with the Rice-Ramsperger-Kassel-Marcus methodology has been employed to calculate the minimum potential energy profiles and the rates of excited state intra-molecular proton transfer (ESIPT) for the WOLED material molecule of HBFO and its four meta- or para-substituted compounds in gas phase, acetonitrile and cyclohexane solvents. The kinetic control for these reactions is quantitatively determined and extensively studied on the basis of the accurate potential energy surfaces when the thermodynamic factor associated with the free energy change becomes negligible in the case of the existence of a significant barrier in the ESIPT process. These computational efforts contribute to a deep understanding of the ESIPT mechanism, dual emission characteristics, kinetic controlling factor, substituent and solvent effects for these material molecules. The white light emission is generated by the establishment of dynamic equilibrium between enol and keto forms in the charge transfer excited SCT((1)ππ*) state. The performance of white light emission is quantitatively demonstrated to be mainly sensitive to the molecular tailoring approach of the electronic properties of meta- or para- substituents by the modulation of the forward/backward ESIPT rate ratio. The quality of white light emission is slightly tunable through its surrounding solvent environment. These computational results will provide a useful strategy for the molecular design of OLED and WOLED materials.

  12. Substituent effects on the photolysis of methyl 2-carboxylate substituted aliphatic 2 H-azirines

    Science.gov (United States)

    Gómez-Zavaglia, Andrea; Kaczor, Agnieszka; Cardoso, Ana L.; Pinho e Melo, Teresa M. V. D.; Fausto, Rui

    2007-05-01

    In this study, the UV induced photochemical reactions of two 2 H-azirines - methyl 2-chloro-3-methyl-2 H-azirine-2-carboxylate (MCMAC) and methyl 3-methyl-2 H-azirine-2-carboxylate (MMAC) - isolated in argon matrices are compared. For both compounds, irradiation with λ > 235 nm led to observation of two primary photoprocesses: (a) C sbnd C bond cleavage, with production of nitrile ylides (P1-type products), and (b) C sbnd N bond cleavage, with production of methylated ketene imines (P2-type products). However, subsequent photoprocesses were found to be different in the two cases. In MCMAC, both primary photoproducts were shown to undergo further reactions: P1-type products decarboxylate, giving [(1-chloroethylidene)imino]ethanide, which bears a C dbnd N +dbnd C - group (P3-type product); P2-type products decarbonylate, yielding a substituted ylidene methanamine (P4-type product). In MMAC, only P2-type primary photoproducts appeared to react, undergoing decarbonylation or decarboxylation (both reactions leading to P4-type products), whereas P1-type products were found to be non-reactive. The non-observation of any secondary photoproduct resulting from photolysis of P1-MMAC revealed the higher photostability of this species when compared with the corresponding photoproduct obtained from MCMAC. The C sbnd N photochemical cleavage is an unusual process in aliphatic 2 H-azirines. In the studied compounds, its preference over the commonly observed C sbnd C azirine-ring bond photocleavage is attributed to the presence of electron withdrawing substituents (methylcarboxy group in both azirines and also the chlorine atom in MCMAC), which accelerates intersystem crossing towards the triplet state from where the cleavage of the C sbnd N bond takes place. The lack of the chlorine atom in MMAC may be partially compensated by the significantly higher stabilization of the P2-type photoproduct derived from this molecule ( ca. -52 kJ mol -1) relatively to the reactant, when

  13. Substituent and structural effects on the kinetics of the reaction of N-(substituted phenylmethylene-m- and -p-aminobenzoic acids with diazodiphenylmethane

    Directory of Open Access Journals (Sweden)

    BRATISLAV Z. JOVANOVIC

    2007-12-01

    Full Text Available The rate constants for the reaction of twenty-two N-(substituted phenyl methylene-m- and -p-aminobenzoic acids with diazodiphenylmethane were determined in absolute ethanol at 30 °C. The effects of substituents on the reactivity of the investigated compounds were interpreted by correlation of the rate constants with LFER equations. The results of quantum mechanical calculations of the mole cular structure together with experimental results gave a better insight into the effects of structure on the transmission of electronic effects of the substituents. New σ constants for substituted benzylideneamino group were calculated.

  14. Infrared matrix isolation study of hydrogen bonds involving C-H bonds: Substituent effects

    International Nuclear Information System (INIS)

    Jeng, M.L.H.; Ault, B.S.

    1989-01-01

    The matrix isolation technique combined with infrared spectroscopy has been employed to isolate and characterize hydrogen-bonded complexes between a series of substituted alkynes and several oxygen and nitrogen bases. Distinct evidence for hydrogen bond formation was observed in each case, with a characteristic red shift of the hydrogen stretching motion ν r . Shifts between 100 and 300 cm -1 were observed, the largest being for the complex of CF 3 CCH with (CH 3 ) 3 N. The perturbed carbon-carbon triple bond stretching vibration was observed for most complexes, as was the alkynic hydrogen bending motion. Attempts were made to correlate the magnitude of the red shift of ν s with substituent constants for the different substituted alkynes; a roughly linear correlation was found with the Hammett σ parameter. Lack of correlation Δν s with either σ 1 or σ R alone suggests that both inductive and resonance contributions to the strength of the hydrogen-bonding interaction are important

  15. Catharanthine C16 substituent effects on the biomimetic coupling with vindoline: preparation and evaluation of a key series of vinblastine analogues

    Science.gov (United States)

    Tam, Annie; Gotoh, Hiroaki; Robertson, William M.; Boger, Dale L.

    2010-01-01

    The examination of the catharanthine C16 substituent effects on the Fe(III)-promoted biomimetic coupling reaction with vindoline is detailed, confirming the importance of the presence of a C16 electron-withdrawing substituent, and establishing an unanticipated unique role (>10-fold) that the C16 methyl ester plays in the expression of the natural product properties. Thus, replacement of the vinblastine C16′ methyl ester with an ethyl ester (10-fold), a cyano group (100-fold), an aldehyde (100-fold), a hydroxymethyl group (1000-fold), or a primary carboxamide (>1000-fold) led to surprisingly large reductions in cytotoxic activity. PMID:20932748

  16. Phosphorus-containing podands. 14. Effect of alkyl substituents at phosphorus atom on complexing ability of neutral monopodands. On the nature of abnormal alkyl effect

    International Nuclear Information System (INIS)

    Tsvetkov, E.N.; Evreinov, V.I.; Bondarenko, N.A.; Safronova, Z.V.

    1996-01-01

    The previously revealed unusual effect of alkyl substituents at phosphorus atom in phosphorus-containing monopodands of the general formula o-R 2 P(O)C 6 H 4 (OCH 2 CH 2 ) n OC 6 H 4 P(O)R 2 -o, n=1-5, R = Alk, Ph, OEt on their complexing ability towards alkali metals cations has been interpreted. Alkyl radicals create great spatial obstacles to rotation of R 2 P(O) fragments around the C-P bond as compared with other substituents, which gives rise to the appearance of anomalous alkyl effect. Solvation is an additional factor, which can bring about the anomalous effect appearance or a change in the degree of its pronouncement. 47 refs.; 3 figs.; 7 tabs

  17. 13C nuclear magnetic resonance data of lanosterol derivatives—Profiling the steric topology of the steroid skeleton via substituent effects on its 13C NMR

    Science.gov (United States)

    Dias, Jerry Ray; Gao, Hongwu

    2009-12-01

    The 13C NMR spectra of over 24 tetracyclic triterpenoid derivatives have been structurally analyzed. The 13C NMR chemical shifts allow one to probe the steric topology of the rigid steroid skeleton and inductive effects of its substituents. Use of deuterium labeling in chemical shift assignment and B-ring aromatic terpenoids are also featured.

  18. Heavy Atom Substituents as Molecular Probes for Solvent Effects on the Dynamics of Short-lived Triplet Exciplexes

    OpenAIRE

    Winter, Gerhard; Steiner, Ulrich

    1980-01-01

    The influence of heavy atom substituents (Br, I) in the electron donor aniline on the electron transfer reaction with thiopyronine triplet is investigated by flash spectroscopy in solvents of different viscosity and polarity. Triplet quenching constants and radical yields are determined. The results are analysed in terms of decay constants of an intermediate triplet exciplex where the heavy atom substituents significantly enhance the intersystem crossing process leading to singlet ground stat...

  19. Effects of Bulky Substituents of Push-Pull Porphyrins on Photovoltaic Properties of Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Higashino, Tomohiro; Kawamoto, Kyosuke; Sugiura, Kenichi; Fujimori, Yamato; Tsuji, Yukihiro; Kurotobi, Kei; Ito, Seigo; Imahori, Hiroshi

    2016-06-22

    To evaluate the effects of substituent bulkiness around a porphyrin core on the photovoltaic properties of porphyrin-sensitized solar cells, long alkoxy groups were introduced at the meso-phenyl group (ZnPBAT-o-C8) and the anchoring group (ZnPBAT-o-C8Cn, n = 4, 8) of an asymmetrically substituted push-pull porphyrin with double electron-donating diarylamino groups and a single electron-withdrawing carboxyphenylethynyl anchoring group. The spectroscopic and electrochemical properties of ZnPBAT-o-C8 and ZnPBAT-o-C8Cn were found to be superior to those of a push-pull porphyrin reference (YD2-o-C8), demonstrating their excellent light-harvesting and redox properties for dye-sensitized solar cells. A power conversion efficiency (η) of the ZnPBAT-o-C8-sensitized solar cell (η = 9.1%) is higher than that of the YD2-o-C8-sensitized solar cell (η = 8.6%) using iodine-based electrolyte due to the enhanced light-harvesting ability of ZnPBAT-o-C8. In contrast, the solar cells based on ZnPBAT-o-C8Cn, possessing the additional alkoxy chains in the anchoring group, revealed the lower η values of 7.3% (n = 4) and 7.0% (n = 8). Although ZnPBAT-o-C8Cn exhibited higher resistance at the TiO2-dye-electrolyte interface by virtue of the extra alkoxy chains, the reduced amount of the porphyrins on TiO2 by excessive addition of coadsorbent chenodeoxycholic acid (CDCA) for mitigating the aggregation on TiO2 resulted in the low η values. Meanwhile, the ZnPBAT-o-C8-sensitized solar cell showed the lower η value of 8.1% than the YD2-o-C8-sensitized solar cell (η = 9.8%) using cobalt-based electrolyte. The smaller η value of the ZnPBAT-o-C8-sensitized solar cell may be attributed to the insufficient blocking effect of the bulky substituents of ZnPBAT-o-C8 under the cobalt-based electrolyte conditions. Overall, the alkoxy chain length and substitution position around the porphyrin core are important factors to affect the cell performance.

  20. Reactivity of main components and substituent distribution in esterified sugarcane bagasse prepared by effective solid phase reaction.

    Science.gov (United States)

    Gan, Tao; Zhang, Yanjuan; Chen, Yane; Hu, Huayu; Yang, Mei; Huang, Zuqiang; Chen, Dong; Huang, Aimin

    2018-02-01

    Three main components of lignocellulose (cellulose, hemicellulose, and lignin isolated from sugarcane bagasse (SCB)) as well as holocellulose and SCB were modified with maleic acid by mechanical activation (MA)-assisted solid phase reaction (MASPR) technology. The order of reactivity was found to be lignin>hemicellulose>cellulose. The amorphous structure of lignin and hemicellulose mainly attributed to their better reactivity, and the modified lignin could reach a maximum degree of esterification (DE) of 93.45%. MA improved the accessibility and reactivity of cellulose, as the DE of modified cellulose gradually increased with milling time and reached the maximum value of 57.30% at 120min, which had significant effect on structure changes and DE of modified holocellulose and SCB. MA enhanced the esterification of all three components in lignocellulose with relatively high substituent distribution in them, and maleated SCB with a maximum DE of 64.17% was successfully prepared by this simple, green, and effective MASPR technology. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. In vitro phase I metabolism of gamabufotalin and arenobufagin: Reveal the effect of substituent group on metabolic stability.

    Science.gov (United States)

    Feng, Yujie; Wang, Chao; Tian, Xiangge; Huo, Xiaokui; Feng, Lei; Sun, Chengpeng; Ge, Guangbo; Yang, Ling; Ning, Jing; Ma, Xiaochi

    2017-09-01

    Bufadienolides are a major class of bioactive compounds derived from amphibian skin secretion. Gamabufotalin (GB) and arenobufagin (AB) are among the top of the intensively investigated natural bufadienolides for their outstanding biological activities. This study aimed to characterize the phase I metabolism of GB and AB with respect to the metabolic profiles, enzymes involved, and catalytic efficacy, thereafter tried to reveal substituent effects on metabolism. Two mono-hydroxylated products of GB and AB were detected in the incubation mixtures, and they were accurately identified as 1- and 5-hydroxylated bufadienolides by NMR and HPLC-MS techniques. Reaction phenotyping studies demonstrated that CYP3A mediated the metabolism of the two bufadienolides with a high specific selectivity. Further kinetic evaluation demonstrated that the metabolism stability of GB and AB were better than other reported bufadienolides. Additionally, the CYP3A5 preference for hydroxylation of AB was observed, which was different to the selectivity of CYP3As for bufadienolides suggested by our previous report. This study can provide important data for elucidating the phase I metabolism of GB and AB and can lead to a better understanding of the bufadienolide-CYP3A interaction which is helpful for preclinical development and rational use of bufadienolides. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Substituent effects on the relaxation dynamics of furan, furfural and β-furfural: a combined theoretical and experimental approach.

    Science.gov (United States)

    Oesterling, Sven; Schalk, Oliver; Geng, Ting; Thomas, Richard D; Hansson, Tony; de Vivie-Riedle, Regina

    2017-01-18

    For the series furan, furfural and β-furfural we investigated the effect of substituents and their positioning on the photoinduced relaxation dynamics in a combined theoretical and experimental approach. Using time resolved photoelectron spectroscopy with a high intensity probe pulse, we can, for the first time, follow the whole deactivation process of furan through a two photon probe signal. Using the extended 2-electron 2-orbital model [Nenov et al., J. Chem. Phys., 2011, 135, 034304] we explain the formation of one central conical intersection and predict the influence of the aldehyde group of the derivatives on its geometry. This, as well as the relaxation mechanisms from photoexcitation to the final outcome was investigated using a variety of theoretical methods. Complete active space self consistent field was used for on-the-fly calculations while complete active space perturbation theory and coupled cluster theory were used to accurately describe critical configurations. Experiment and theory show the relaxation dynamics of furfural and β-furfural to be slowed down, and together they disclose an additional deactivation pathway, which is attributed to the n O lonepair state introduced with the aldehyde group.

  3. Substituent effects on the electron affinities and ionization energies of tria-, penta-, and heptafulvenes: a computational investigation

    DEFF Research Database (Denmark)

    Dahlstrand, Christian; Yamazaki, Kaoru; Kilså, Kristine

    2010-01-01

    (TCNQ) and tetrathiafulvalene (TTF) as representing strong electron-acceptor and -donor compounds, respectively. The substituents X at the exocyclic positions of the fulvenes were either NH(2), H, or CN, while the substituents Y at the ring positions were H, Cl, F, CN, or NH(2). The variations...... of bis(fulvene)s, i.e., compounds composed of a donor-type heptafulvene fused with an acceptor-type pentafulvene, and it was revealed that these bis(fulvene)s can be designed so that the IE and EA of the two separate fulvene segments are retained, potentially allowing for the design of compact donor...

  4. Substituent effect of phenolic aldehyde inhibition on alcoholic fermentation by Saccharomyces cerevisiae

    Science.gov (United States)

    Rui Xie; Maobing Tu; Thomas Elder

    2016-01-01

    Phenolic compounds significantly inhibit microbial fermentation of biomass hydrolysates. To understand thequantitative structure-inhibition relationship of phenolic aldehydes on alcoholic fermentation, the effect of 11 differentsubstituted benzaldehydes on the final ethanol yield was examined. The results showed that the degree of phenolic...

  5. Characterizing Chemical Similarity with Vibrational Spectroscopy: New Insights into the Substituent Effects in Monosubstituted Benzenes.

    Science.gov (United States)

    Tao, Yunwen; Zou, Wenli; Cremer, Dieter; Kraka, Elfi

    2017-10-26

    A novel approach is presented to assess chemical similarity based the local vibrational mode analysis developed by Konkoli and Cremer. The local mode frequency shifts are introduced as similarity descriptors that are sensitive to any electronic structure change. In this work, 59 different monosubstituted benzenes are compared. For a subset of 43 compounds, for which experimental data was available, the ortho-/para- and meta-directing effect in electrophilic aromatic substitution reactions could be correctly reproduced, proving the robustness of the new similarity index. For the remaining 16 compounds, the directing effect was predicted. The new approach is broadly applicable to all compounds for which either experimental or calculated vibrational frequency information is available.

  6. Application of the Fenske-Hall molecular orbital method to the calculation of 11B NMR chemical shifts. Antipodal substituent effects in deltahedral clusters

    International Nuclear Information System (INIS)

    Fehlner, T.P.; Czech, P.T.; Fenske, R.F.

    1990-01-01

    Utilizing Fenske-Hall wave functions and eigenvalues combined with the Ramsey sum over states (SOS) approximation, it is demonstrated that the sign and magnitude of the paramagnetic contribution to the shielding correlates well with the observed 11 B chemical shifts of a substantial variety of boron- and metal-containing compounds. Analysis of the molecular orbital (MO) contributions in the SOS approximation leads to an explanation of the large downfield shifts associated with metal-rich metallaboranes. A similar analysis demonstrates the importance of selected cluster occupied and unoccupied MO's in explaining both exo-cage substituent effects in which the antipodal boron resonance is shifted upfield and endo-cage substituent effects (interchange of isolobal fragments within the cage framework) in which the antipodal boron resonance is shifted downfield. Exo- and endo-cage substitution perturbs these MO's in an understandable fashion, leading to an internally consistent explanation of the observed chemical shift changes. 36 refs., 8 figs., 4 tabs

  7. Supramolecular Switches Based on the Guanine–Cytosine (GC) Watson–Crick Pair: Effect of Neutral and Ionic Substituents

    NARCIS (Netherlands)

    Guerra, C.F.; van der Wijst, T.; Bickelhaupt, F.M.

    2006-01-01

    We have theoretically analyzed Watson–Crick guanine–cytosine (GC) base pairs in which purine-C8 and/or pyrimidine-C6 positions carry a substituent X = NH−, NH2, NH3+ (N series), O−, OH, or OH2+ (O series), using the generalized gradient approximation (GGA) of density functional theory at the

  8. Effect of Polyhedral Oligomeric Silsesquioxane (POSS) Substituents on the Rheological Behavior in Butyl Methacrylate/POSS Copolymers

    Science.gov (United States)

    2008-10-27

    was repeated twice, dissolving the product in chloroform and diethyl ether, respectively. The polymer was dried at 60 °C under vacuum overnight...the Tg of the i Bu remains the same. Table 1. Tg for Butyl Methacrylate-co- Propyl Methacryl POSS Polymers with Various POSS Substituents

  9. Charge-Shift Corrected Electronegativities and the Effect of Bond Polarity and Substituents on Covalent-Ionic Resonance Energy.

    Science.gov (United States)

    James, Andrew M; Laconsay, Croix J; Galbraith, John Morrison

    2017-07-13

    Bond dissociation energies and resonance energies for H n A-BH m molecules (A, B = H, C, N, O, F, Cl, Li, and Na) have been determined in order to re-evaluate the concept of electronegativity in the context of modern valence bond theory. Following Pauling's original scheme and using the rigorous definition of the covalent-ionic resonance energy provided by the breathing orbital valence bond method, we have derived a charge-shift corrected electronegativity scale for H, C, N, O, F, Cl, Li, and Na. Atomic charge shift character is defined using a similar approach resulting in values of 0.42, 1.06, 1.43, 1.62, 1.64, 1.44, 0.46, and 0.34 for H, C, N, O, F, Cl, Li, and Na, respectively. The charge-shift corrected electronegativity values presented herein follow the same general trends as Pauling's original values with the exception of Li having a smaller value than Na (1.57 and 1.91 for Li and Na respectively). The resonance energy is then broken down into components derived from the atomic charge shift character and polarization effects. It is then shown that most of the resonance energy in the charge-shift bonds H-F, H 3 C-F, and Li-CH 3 and borderline charge-shift H-OH is associated with polarity rather than the intrinsic atomic charge-shift character of the bonding species. This suggests a rebranding of these bonds as "polar charge-shift" rather than simply "charge-shift". Lastly, using a similar breakdown method, it is shown that the small effect the substituents -CH 3 , -NH 2 , -OH, and -F have on the resonance energy (<10%) is mostly due to changes in the charge-shift character of the bonding atom.

  10. Mesomeric Effects of Graphene Modified with Diazonium Salts: Substituent Type and Position Influence its Properties.

    Science.gov (United States)

    Bouša, Daniel; Jankovský, Ondřej; Sedmidubský, David; Luxa, Jan; Šturala, Jiří; Pumera, Martin; Sofer, Zdeněk

    2015-12-01

    In the last decade, graphene and graphene derivatives have become some of the most intensively studied materials. Tuning of the electronic and electrochemical properties of graphene is of paramount importance. In this study, six diazonium-modified graphenes containing different functional groups according to the diazonium salt precursor were investigated. These diazonium moieties have a strong mesomeric (resonance) effect and act as either electron-donating or -withdrawing species. Different graphene precursors, such as thermally and chemically reduced graphenes were studied. All the products were characterized in detail by elemental combustion analysis, FTIR spectroscopy, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. Resistivity and zeta potential measurements were consistent with theoretical (DFT) calculations. The results show that chemical modification of graphene by diazotation strongly influences its properties, creating a huge application potential in microelectronics, energy storage and conversion devices, and electrocatalysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Electronic states of carbon alloy catalysts and nitrogen substituent effects on catalytic activity

    Science.gov (United States)

    Hata, Tomoyuki; Ushiyama, Hiroshi; Yamashita, Koichi

    2013-03-01

    In recent years, Carbon Alloy Catalysts (CACs) are attracting attention as a candidate for non-platinum-based cathode catalysts in fuel cells. Oxygen reduction reactions at the cathode are divided into two elementary processes, electron transfer and oxygen adsorption. The electron transfer reaction is the rate-determining, and by comparison of energy levels, catalytic activity can be evaluated quantitatively. On the other hand, to begin with, adsorption mechanism is obscure. The purpose of this study is to understand the effect of nitrogen substitution and oxygen adsorption mechanism, by first-principle electronic structure calculations for nitrogen substituted models. To reproduce the elementary processes of oxygen adsorption, we assumed that the initial structures are formed based on the Pauling model, a CACs model and nitrogen substituted CACs models in which various points are replaced with nitrogen. When we try to focus only on the DOS peaks of oxygen, in some substituted model that has high adsorption activity, a characteristic partial occupancy state was found. We conclude that this state will affect the adsorption activity, and discuss on why partially occupied states appear with simplification by using an orbital correlation diagram.

  12. Substituent effects on dynamics at conical intersections: Allene and methyl allenes

    Energy Technology Data Exchange (ETDEWEB)

    Neville, Simon P. [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Wang, Yanmei [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Boguslavskiy, Andrey E.; Stolow, Albert, E-mail: albert.stolow@nrc-cnrc.gc.ca [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa ON K1N 6N5 (Canada); Schuurman, Michael S., E-mail: michael.schuurman@nrc-cnrc.gc.ca [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada)

    2016-01-07

    carbon atoms of allene. The interplay between inertial and potential effects is a key to understanding these dynamical branching pathways. The good agreement between the simulated and measured TRPES confers additional confidence to the dynamical picture presented here.

  13. Substituent and solvent effects on spectroscopic properties of 2-amino-1,3-dicyano-5,6,7,8-tetrahydronaphthalene derivatives

    International Nuclear Information System (INIS)

    Józefowicz, M.; Bajorek, A.; Pietrzak, M.; Heldt, J.R.; Heldt, J.

    2014-01-01

    In this article, we report the photophysical properties of six, newly synthesized donor-substituted 2-amino-1,3-dicyano-5,6,7,8-tetrahydronaphthalene fluorophores. The steady-state and time-resolved spectroscopic experiments have been used to investigate the substituent and solvent effects on the locally excited (LE) and intramolecular charge transfer (ICT) emission. We demonstrate that the spectroscopic characteristics (fluorescence quantum yields, fluorescence decay times, radiative rate constants, and ground and excited state dipole moments) of the studied D–A dyes, as well as the reorganization energies characterizing the solute–solvent interactions and intramolecular torsion motions greatly depend on different substituents and microenvironment. On the basis of the experimental results and our previous quantum-chemical calculations, it was shown that two emitting charge transfer states: non-relaxed (ICT) NR and relaxed (ICT) R exist in six biphenyl derivatives dissolved in polar solvents (e.g., THF), whereas in non-polar medium (MCH) the existence of two emissive states have been attributed to non-relaxed and relaxed, locally excited state ((LE) NR , (LE) R ). - Highlights: • Spectroscopic properties greatly depend on different substituents and microenvironment. • Investigated dyes form a typically spectrally inhomogeneous system. • Two emitting charge transfer states (ICT) NR and (ICT) R exist in polar solvents. • In non-polar medium locally excited fluorescence is possible from (LE) NR and (LE) R states

  14. Conformational equilibrium and effects of some 2-mono substituted cyclohexanone substituents; Equilibrio conformacional e efeitos dos substituintes de algumas cicloexanonas 2-monossubstituidas

    Energy Technology Data Exchange (ETDEWEB)

    Basso, Ernani A [Universidade Estadual de Maringa, PR (Brazil); Trevisan, Paulo S [Universidade Estadual de Campinas, SP (Brazil). Inst. de Quimica; Lambert, Joseph B [Northwestern Univ. (United States)

    1992-12-31

    This work re-evaluates, using a high-field device (400 MHz) and the Eliel method, the 2-halo substituted cyclohexanone conformational equilibrium, which applies the chemical shift values ({delta}) and the {alpha} proton coupling constants (J). {sup 13} C NMR spectra were also obtained for investigation of the substituent effects on the cyclohexanone ring carbons chemical shift, since the few works treating the subject are at most incomplete. The results are compared with those obtained for the 2-methoxy cyclohexanone previously described, and reproduced in this work 12 refs., 4 figs., 3 tabs.

  15. Model Studies of the Histidine-Tyrosine Cross-Link in Cytochrome c Oxidase Reveal the Flexible Substituent Effect of the Imidazole Moiety

    Science.gov (United States)

    Pratt, Derek A.; Pesavento, Russell P.; van der Donk, Wilfred A.

    2010-01-01

    Experimental and theoretical studies were carried out to interrogate the effect of an imidazole substituent in each of the ortho, meta, and para positions on the pKa, E°, and O–H BDE of phenol. The results reveal that imidazole substitution lowers the pKa of phenol and increases the E° of phenoxide due to its σ-electron withdrawing ability (σp− = +0.21, σm− = +0.45) but decreases the O–H BDE and E° of phenol due to its σ-electron-donating ability (σp+ = −0.45). PMID:15957934

  16. Substituent effects in heterogeneous catalysis--4. Adsorption estimations during competitive hydrogenation of cyclohexanone and its 2-alkyl derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Chihara, T; Tanaka, K

    1979-02-01

    Adsorption estimations during competitive hydrogenation of cyclohexanone and its 2-alkyl derivatives alumina-supported ruthenium, rhodium, and platinum catalysts were obtained in a study to determine the relative contributions of the rate constants and the adsorption equilibrium constants to the substituent-dependent constant. The reaction rates obtained during competitive hydrogenation were in the order cyclohexanone (A) Vertical Bar3:Vertical Bar3: 2-methyl cyclohexanone (B) Vertical Bar3: 2-ethyl cyclohexanone (C) Vertical Bar3: 2-propyl cyclohexanone (D) for all catalysts, whereas the rates obtained during individual hydrogenation were in the order A Vertical Bar3: B approx. C approx. D. The adsorption equilibrium constants which were estimated by analyzing the kinetic data agreed well with the theoretical values derived from statistical mechanics by using a model in which the substrate ketones were immobilely adsorbed.

  17. Approaching an experimental electron density model of the biologically active trans -epoxysuccinyl amide group-Substituent effects vs. crystal packing

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Ming W.; Stewart, Scott G.; Sobolev, Alexandre N.; Dittrich, Birger; Schirmeister, Tanja; Luger, Peter; Hesse, Malte; Chen, Yu-Sheng; Spackman, Peter R.; Spackman, Mark A.; Grabowsky, Simon (Heinrich-Heine); (Freie); (UC); (Bremen); (JG-UM); (UWA)

    2017-01-24

    The trans-epoxysuccinyl amide group as a biologically active moiety in cysteine protease inhibitors such as loxistatin acid E64c has been used as a benchmark system for theoretical studies of environmental effects on the electron density of small active ingredients in relation to their biological activity. Here, the synthesis and the electronic properties of the smallest possible active site model compound are reported to close the gap between the unknown experimental electron density of trans-epoxysuccinyl amides and the well-known function of related drugs. Intramolecular substituent effects are separated from intermolecular crystal packing effects on the electron density, which allows us to predict the conditions under which an experimental electron density investigation on trans-epoxysuccinyl amides will be possible. In this context, the special importance of the carboxylic acid function in the model compound for both crystal packing and biological activity is revealed through the novel tool of model energy analysis.

  18. Effects of La-Zn substituent and calcination temperature on the microstructure and magnetic properties of Sr-ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiangcheng; Zhao, Zhang; Zhu, Boquan [Wuhan Univ. of Science and Technology (China). State Key Lab. of Refractories and Metallurgy

    2015-01-15

    In this study, La-Zn-substituted SrFe{sub 12}O{sub 19} ferrites were synthesized using the traditional ceramic process. The by-products of iron oxide scales from a steel plant were used as the main raw materials. The influence of the La-Zn substituent and the calcination temperature on the microstructure and magnetic properties of Sr{sub 1-x}La{sub x}Fe{sub 12-x}Zn{sub x}O{sub 19} ferrites was investigated. The results showed that with the increase in the x value, the crystalline lattice constant of the a- and c-axes and the cell volume decreased. There was no α-Fe{sub 2}O{sub 3} phase in the ferrites when the value of x was 0.3. The corresponding saturation magnetization (M{sub s}) and remnant magnetization (M{sub r}) values were, respectively, about 65 emu g{sup -1} and 39.5 emu g{sup -1}. Both values of M{sub s} and M{sub r} rise to the maximum value. When the calcination temperature was reduced from 1200 C to 1150 C, the average particle size decreased from 0.9 μm to 0.7 μm and M{sub s} remained at 65 emu g{sup -1}. However, the coercivity increased from 2690 Oe to 3100 Oe.

  19. Design, synthesis, characterization, and OFET properties of amphiphilic heteroleptic tris(phthalocyaninato) europium(III) complexes. The effect of crown ether hydrophilic substituents.

    Science.gov (United States)

    Gao, Yingning; Ma, Pan; Chen, Yanli; Zhang, Ying; Bian, Yongzhong; Li, Xiyou; Jiang, Jianzhuang; Ma, Changqin

    2009-01-05

    Two amphiphilic heteroleptic tris(phthalocyaninato) europium complexes with hydrophilic crown ether heads and hydrophobic octyloxy tails [Pc(mCn)(4)]Eu[Pc(mCn)(4)]Eu[Pc(OC(8)H(17))(8)] [m = 12, n = 4, H(2)Pc(12C4)(4) = 2,3,9,10,16,17,23,24-tetrakis(12-crown-4)phthalocyanine; m = 18, n = 6, H(2)Pc(18C6)(4) = 2,3,9,10,16,17,23,24-tetrakis(18-crown-6)phthalocyanine; H(2)Pc(OC(8)H(17))(8) = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine] (1, 2) were designed and prepared from the reaction between homoleptic bis(phthalocyaninato) europium compound [Pc(mCn)(4)]Eu[Pc(mCn)(4)] (m = 12, n = 4; m = 18, n = 6) and metal-free H(2)Pc(OC(8)H(17))(8) in the presence of Eu(acac)(3).H(2)O (Hacac = acetylacetone) in boiling 1,2,4-trichlorobenzene. These novel sandwich triple-decker complexes were characterized by a wide range of spectroscopic methods and electrochemically studied. With the help of the Langmuir-Blodgett technique, these typical amphiphilic triple-decker complexes were fabricated into organic field effect transistors (OFET) with top contact configuration on bare SiO(2)/Si substrate, hexamethyldisilazane-treated SiO(2)/Si substrate, and octadecyltrichlorosilane (OTS)-treated SiO(2)/Si substrate, respectively. The device performance is revealed to be dependent on the species of crown ether substituents and substrate surface treatment. OFETs fabricated from the triple decker with 12-crown-4 hydrophilic substituents, 1, allow the hole transfer in the direction parallel to the aromatic phthalocyanine rings. In contrast, the devices of a triple-decker compound containing 18-crown-6 as hydrophilic heads, 2, transfer holes in a direction along the long axis of the assembly composed of face-to-face aggregated triple-decker molecules, revealing the effect of molecular structure, specifically the crown ether substituents on the film structure and OFET functional properties. The carrier mobility for hole as high as 0.33 cm(2) V(-1) s(-1) and current modulation of 7.91 x 10

  20. Substituent effects on the electronic characteristics of pentacene derivatives for organic electronic devices: dioxolane-substituted pentacene derivatives with triisopropylsilylethynyl functional groups.

    Science.gov (United States)

    Griffith, Olga Lobanova; Anthony, John E; Jones, Adolphus G; Shu, Ying; Lichtenberger, Dennis L

    2012-08-29

    The intramolecular electronic structures and intermolecular electronic interactions of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS pentacene), 6,14-bis-(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]-pentacene (TP-5 pentacene), and 2,2,10,10-tetraethyl-6,14-bis-(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]pentacene (EtTP-5 pentacene) have been investigated by the combination of gas-phase and solid-phase photoelectron spectroscopy measurements. Further insight has been provided by electrochemical measurements in solution, and the principles that emerge are supported by electronic structure calculations. The measurements show that the energies of electron transfer such as the reorganization energies, ionization energies, charge-injection barriers, polarization energies, and HOMO-LUMO energy gaps are strongly dependent on the particular functionalization of the pentacene core. The ionization energy trends as a function of the substitution observed for molecules in the gas phase are not reproduced in measurements of the molecules in the condensed phase due to polarization effects in the solid. The electronic behavior of these materials is impacted less by the direct substituent electronic effects on the individual molecules than by the indirect consequences of substituent effects on the intermolecular interactions. The ionization energies as a function of film thickness give information on the relative electrical conductivity of the films, and all three molecules show different material behavior. The stronger intermolecular interactions in TP-5 pentacene films lead to better charge transfer properties versus those in TIPS pentacene films, and EtTP-5 pentacene films have very weak intermolecular interactions and the poorest charge transfer properties of these molecules.

  1. Cu(II) bis(thiosemicarbazone) radiopharmaceutical binding to serum albumin: further definition of species dependence and associated substituent effects

    International Nuclear Information System (INIS)

    Basken, Nathan E.; Green, Mark A.

    2009-01-01

    Introduction: The pyruvaldehyde bis(N 4 -methylthiosemicarbazonato)copper(II) (Cu-PTSM) and diacetyl bis(N 4 -methylthiosemicarbazonato)copper(II) (Cu-ATSM) radiopharmaceuticals exhibit strong, species-dependent binding to the IIA site of human serum albumin (HSA), while the related ethylglyoxal bis(thiosemicarbazonato)copper(II) (Cu-ETS) radiopharmaceutical appears to exhibit only nonspecific binding to HSA and animal serum albumins. Methods: To further probe the structural basis for the species dependence of this albumin binding interaction, we examined protein binding of these three radiopharmaceuticals in solutions of albumin and/or serum from a broader array of mammalian species (rat, sheep, donkey, rabbit, cow, pig, dog, baboon, mouse, cat and elephant). We also evaluated the albumin binding of several copper(II) bis(thiosemicarbazone) chelates offering more diverse substitution of the ligand backbone. Results: Cu-PTSM and Cu-ATSM exhibit a strong interaction with HSA that is not apparent with the albumins of other species, while the binding of Cu-ETS to albumin is much less species dependent. The strong interaction of Cu-PTSM with HSA does not appear to simply correlate with variation, relative to the animal albumins, of a single amino acid lining HSA's IIA site. Those agents that selectively interact with HSA share the common feature of only methyl or hydrogen substitution at the carbon atoms of the diimine fragment of the ligand backbone. Conclusions: The interspecies variations in albumin binding of Cu-PTSM and Cu-ATSM are not simply explained by unique amino acid substitutions in the IIA binding pocket of the serum albumins. However, the specific affinity for this region of HSA is disrupted when substituents bulkier than a methyl group appear on the imine carbons of the copper bis(thiosemicarbazone) chelate.

  2. Cu(II) bis(thiosemicarbazone) radiopharmaceutical binding to serum albumin: further definition of species dependence and associated substituent effects

    Energy Technology Data Exchange (ETDEWEB)

    Basken, Nathan E. [Division of Nuclear Pharmacy, Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, IN 47907 (United States); Green, Mark A. [Division of Nuclear Pharmacy, Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, IN 47907 (United States)], E-mail: magreen@purdue.edu

    2009-07-15

    Introduction: The pyruvaldehyde bis(N{sup 4}-methylthiosemicarbazonato)copper(II) (Cu-PTSM) and diacetyl bis(N{sup 4}-methylthiosemicarbazonato)copper(II) (Cu-ATSM) radiopharmaceuticals exhibit strong, species-dependent binding to the IIA site of human serum albumin (HSA), while the related ethylglyoxal bis(thiosemicarbazonato)copper(II) (Cu-ETS) radiopharmaceutical appears to exhibit only nonspecific binding to HSA and animal serum albumins. Methods: To further probe the structural basis for the species dependence of this albumin binding interaction, we examined protein binding of these three radiopharmaceuticals in solutions of albumin and/or serum from a broader array of mammalian species (rat, sheep, donkey, rabbit, cow, pig, dog, baboon, mouse, cat and elephant). We also evaluated the albumin binding of several copper(II) bis(thiosemicarbazone) chelates offering more diverse substitution of the ligand backbone. Results: Cu-PTSM and Cu-ATSM exhibit a strong interaction with HSA that is not apparent with the albumins of other species, while the binding of Cu-ETS to albumin is much less species dependent. The strong interaction of Cu-PTSM with HSA does not appear to simply correlate with variation, relative to the animal albumins, of a single amino acid lining HSA's IIA site. Those agents that selectively interact with HSA share the common feature of only methyl or hydrogen substitution at the carbon atoms of the diimine fragment of the ligand backbone. Conclusions: The interspecies variations in albumin binding of Cu-PTSM and Cu-ATSM are not simply explained by unique amino acid substitutions in the IIA binding pocket of the serum albumins. However, the specific affinity for this region of HSA is disrupted when substituents bulkier than a methyl group appear on the imine carbons of the copper bis(thiosemicarbazone) chelate.

  3. Effect of the nature of p-substituents in benzene ring of azo compounds based on chromotropic acid on their reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Savvin, S B; Dedkova, V P; Azarashvili, M A; Likhonina, E A

    1988-08-01

    Effect of acceptor and donor substituents in a reagent on degree of contrast and selectivity of spectrophotometric beryllium determination as well as other elements was considered taking derivatives of orthanilic-azo-chromotropic acid as an example. The optimal pH region of aminoorthanilic-azo-chromotropic acid interaction with Be 5-6.5; the optimal wavelength is 640 nm. The solution colour changes from violet-red to blue during complex formation. Selectivity increases after addition of masking substances. Be determination on the background of 4-fold Cu and VO/sup 2+/ amounts 8-fold Al amounts, 2-fold Zn amounts is possible in the presence of 5-fold EDTA amounts unsubstituted reagent is characterized by the lowest degree of contrast and selectivity of reactions with metals.

  4. γ-Glutamyl-dipeptides: Easy tools to rapidly probe the stereoelectronic properties of ionotropic glutamate receptor binding pocket

    DEFF Research Database (Denmark)

    Tamborini, Lucia; Nicosia, Veronica; Conti, Paola

    2016-01-01

    γ-Glutamyl-dipeptides, built by condensing the distal carboxylate of L-Glu (or D-Glu) onto a series of differently functionalized amino acids, were prepared and used as tools for rapidly probing the stereoelectronic properties of iGluRs, searching for subtype-selective ligands.......γ-Glutamyl-dipeptides, built by condensing the distal carboxylate of L-Glu (or D-Glu) onto a series of differently functionalized amino acids, were prepared and used as tools for rapidly probing the stereoelectronic properties of iGluRs, searching for subtype-selective ligands....

  5. Effects of alkyl chain length and substituent pattern of fullerene bis-adducts on film structures and photovoltaic properties of bulk heterojunction solar cells.

    Science.gov (United States)

    Tao, Ran; Umeyama, Tomokazu; Kurotobi, Kei; Imahori, Hiroshi

    2014-10-08

    A series of alkoxycarbonyl-substituted dihydronaphthyl-based [60]fullerene bis-adduct derivatives (denoted as C2BA, C4BA, and C6BA with the alkyl chain of ethyl, n-butyl, and n-hexyl, respectively) have been synthesized to investigate the effects of alkyl chain length and substituent pattern of fullerene bis-adducts on the film structures and photovoltaic properties of bulk heterojunction polymer solar cells. The shorter alkyl chain length caused lower solubility of the fullerene bis-adducts (C6BA > C4BA > C2BA), thereby resulting in the increased separation difficulty of respective bis-adduct isomers. The device performance based on poly(3-hexylthiophene) (P3HT) and the fullerene bis-adduct regioisomer mixtures was enhanced by shortening the alkyl chain length. When using the regioisomerically separated fullerene bis-adducts, the devices based on trans-2 and a mixture of trans-4 and e of C4BA exhibited the highest power conversion efficiencies of ca. 2.4%, which are considerably higher than those of the C6BA counterparts (ca. 1.4%) and the C4BA regioisomer mixture (1.10%). The film morphologies as well as electron mobilities of the P3HT:bis-adduct blend films were found to affect the photovoltaic properties considerably. These results reveal that the alkyl chain length and substituent pattern of fullerene bis-adducts significantly influence the photovoltaic properties as well as the film structures of bulk heterojunction solar cells.

  6. Effect of bulky substituents on thiopyrylium polymethine aggregation in the solid state: A theoretical evaluation of the implications for all-optical switching applications

    KAUST Repository

    Gieseking, Rebecca L.

    2014-11-25

    Polymethine dyes in dilute solutions display many of the optical properties required for all-optical switching applications. However, in thin films, aggregation and polymethine-counterion interactions can substantially modify their properties and limit their utility. Here, we examine the impact of a series of bulky substituents on the solid-state molecular packing of thiopyrylium polymethines by using a theoretical approach combining molecular-dynamics simulations and quantum-chemical calculations. Importantly, it is found that the positions of the substituents near the center and/or ends of the dye determine the extent to which aggregation is reduced; in particular, substituents near the polymethine center primarily modify the type of aggregation that is observed, while substituents near the polymethine ends reduce aggregation and aid in maintaining solution-like properties in the solid state. Our theoretical study elucidates relationships between molecular structure and bulk optical properties and provides design guidelines for all-optical switching materials.

  7. Effect of bulky substituents on thiopyrylium polymethine aggregation in the solid state: A theoretical evaluation of the implications for all-optical switching applications

    KAUST Repository

    Gieseking, Rebecca L.; Mukhopadhyay, Sukrit; Risko, Chad; Marder, Seth R.; Bredas, Jean-Luc

    2014-01-01

    and limit their utility. Here, we examine the impact of a series of bulky substituents on the solid-state molecular packing of thiopyrylium polymethines by using a theoretical approach combining molecular-dynamics simulations and quantum

  8. Pentafluorosulfanyl Substituents in Polymerization Catalysis.

    Science.gov (United States)

    Kenyon, Philip; Mecking, Stefan

    2017-10-04

    Highly electron-withdrawing pentafluorosulfanyl groups were probed as substituents in an organometallic catalyst. In Ni(II) salicylaldiminato complexes as an example case, these highly electron-withdrawing substituents allow for polymerization of ethylene to higher molecular weights with reduced branching due to significant reductions in β-hydrogen elimination. Combined with the excellent functional group tolerance of neutral Ni(II) complexes, this suppression of β-hydrogen elimination allows for the direct polymerization of ethylene in water to nanocrystal dispersions of disentangled, ultrahigh-molecular-weight linear polyethylene.

  9. Pull-push mechanism for the 1,2-hydrogen rearrangement of carbenes. Substituent and deuterium isotope effects for thermal decomposition of 1-phenyl-2-diazopropanes

    International Nuclear Information System (INIS)

    Su, D.T.T.; Thornton, E.R.

    1978-01-01

    Intramolecular and intermolecular deuterium isotope effects have been measured for the thermal carbene H rearrangements of three substituted 1-phenyl-2-diazopropanes-1-d in hexane at 25 0 C. The isotope effects, k/sub H//k/sub D/, vary from ca. 1.2 to 1.5, increasing with electron-withdrawing substituents, for the formation of both cis- and trans-β-methylstyrenes. Product ratios were determined for these compounds as well as the corresponding undeuterated ones, permitting calculation of intermolecular primary and secondary isotope effects. In addition, the competition among the cis and trans products and the product of H migration from the terminal methyl group permitted determination of Hammett rho values of ca. -1 for the competition between benzylic and terminal migration. The results strongly indicate a ''pull-push'' mechanism, which can be pictured roughly as electrophilic attack on the C--H bond by the phantom p orbital of the carbene along with backside nucleophilic attack by the carbene unshared electron pair to push the H away and form the π bond. The data are believed to be consistent only with a nonzero barrier for the carbene hydrogen rearrangement

  10. DFT studies of the substituent effects of dimethylamino on non-heme active oxidizing species: iron(V)-oxo species or iron(IV)-oxo acetate aminopyridine cation radical species?

    Science.gov (United States)

    Wang, Fang; Sun, Wei; Xia, Chungu; Wang, Yong

    2017-10-01

    Through the introduction of dimethylamino (Me 2 N) substituent at the pyridine ring of 2-((R)-2-[(R)-1-(pyridine-2-ylmethyl)pyrrolidin-2-yl]pyrrolidin-1-ylmethyl)pyridine (PDP) ligand, the non-heme Fe II ( Me2N PDP)/H 2 O 2 /AcOH catalyst system was found to exhibit significant higher catalytic activity and enantioselectivity than the non-substituent one in the asymmetric epoxidation experiments. The mechanistic origin of the remarkable substituent effects in these oxidation reactions has not been well established. To ascertain the potent oxidant and the related reaction mechanism, a detailed DFT calculation was performed. Interestingly, a novel Fe(IV)-oxo Me2N PDP cation radical species, [( Me2N PDP) + · Fe IV (O)(OAc)] 2+ ( Me2N 5), with about one spin spreading over the non-heme Me2N PDP ligand was formed via a carboxylic-acid-assisted O-O bond heterolysis, which is reminiscent of Compound I (an Fe(IV)(O)(porphyrin cation radical) species) in cytochrome P450 chemistry. Me2N 5 is energetically comparable with the cyclic ferric peracetate species Me2N 6, while in the pristine Fe(PDP) catalyst system, H 6 is more stable than H 5. Comparison of the activation energy for the ethylene epoxidation promoted by Me2N 5 and Me2N 6, Me2N 5 is supposed as the true oxidant triggering the epoxidation of olefins. In addition, a systematic research on the substituent effects varied from the electron-donating substituent (dMM, the substituents at sites 3, 4, and 5 of the pyridine ring: methyl, methoxyl, and methyl) to the electron-withdrawing one (CF 3 , 2,6-bis(trifluoromethyl)phenyl) on the electronic structure of the reaction intermediates has also been investigated. An alternative cyclic ferric peracetate complex is obtained, indicating that the substituents at the pyridine ring of PDP ligands have significant impacts on the electronic structure of the oxidants.

  11. Calculation of spectral shifts in UV–visible region and photoresponsive behaviour of fluorinated liquid crystals: Effect of solvent and substituent

    International Nuclear Information System (INIS)

    Lakshmi Praveen, P.; Ojha, Durga P.

    2012-01-01

    The photoresponsive behaviour of fluorinated liquid crystals p-phenylene-4-methoxy benzoate-4-trifluoromethylbenzoate (FLUORO1), and 4-propyloxyphenyl-4-(4-trifluoromethylbenzoyloxy) benzoate (FLUORO2) has been systematically investigated using the CNDO/S + CI and INDO/S + CI methods. These methods have been employed to calculate/analyze the spectral shifts, and absorbance measurements in UV–visible region of the systems. The electronic transitions, absorption wavelength, HOMO (highest occupied molecular orbital), and LUMO (lowest unoccupied molecular orbital) energies have been calculated. Further, ultraviolet (UV) stability of the molecules has been discussed in the light of absorption wavelength and electronic transition oscillator strength (f). The effect of different solvent media and substituents on transition energies, oscillator strength, and other absorption parameters have also been reported. The present article provides valuable information regarding enhancing the UV stability of molecules by marinating their conductivity. Highlights: ► The strongest bands of FLUORO molecules can be assigned as π → π ∗ transitions. ► A small red-shift indicates a weak exciton coupling of chromophores. ► No n → π ∗ transition occurs due to the rigidity of the ring system of the molecules. ► The HOMO, LUMO, and E g values have been found to be independent of solvent effect.

  12. Calculation of spectral shifts in UV-visible region and photoresponsive behaviour of fluorinated liquid crystals: Effect of solvent and substituent

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmi Praveen, P. [Liquid Crystal Research Laboratory, Post-Graduate Department of Physics, Andhra Loyola College, Vijayawada 520 008, A.P. (India); Ojha, Durga P., E-mail: durga_ojha@hotmail.com [Liquid Crystal Research Laboratory, Post-Graduate Department of Physics, Andhra Loyola College, Vijayawada 520 008, A.P. (India)

    2012-08-15

    The photoresponsive behaviour of fluorinated liquid crystals p-phenylene-4-methoxy benzoate-4-trifluoromethylbenzoate (FLUORO1), and 4-propyloxyphenyl-4-(4-trifluoromethylbenzoyloxy) benzoate (FLUORO2) has been systematically investigated using the CNDO/S + CI and INDO/S + CI methods. These methods have been employed to calculate/analyze the spectral shifts, and absorbance measurements in UV-visible region of the systems. The electronic transitions, absorption wavelength, HOMO (highest occupied molecular orbital), and LUMO (lowest unoccupied molecular orbital) energies have been calculated. Further, ultraviolet (UV) stability of the molecules has been discussed in the light of absorption wavelength and electronic transition oscillator strength (f). The effect of different solvent media and substituents on transition energies, oscillator strength, and other absorption parameters have also been reported. The present article provides valuable information regarding enhancing the UV stability of molecules by marinating their conductivity. Highlights: Black-Right-Pointing-Pointer The strongest bands of FLUORO molecules can be assigned as {pi} {yields} {pi}{sup Asterisk-Operator} transitions. Black-Right-Pointing-Pointer A small red-shift indicates a weak exciton coupling of chromophores. Black-Right-Pointing-Pointer No n {yields} {pi}{sup Asterisk-Operator} transition occurs due to the rigidity of the ring system of the molecules. Black-Right-Pointing-Pointer The HOMO, LUMO, and E{sub g} values have been found to be independent of solvent effect.

  13. The Diels-Alder Cycloaddition Reaction of Substituted Hemifullerenes with 1,3-Butadiene: Effect of Electron-Donating and Electron-Withdrawing Substituents.

    Science.gov (United States)

    Mojica, Martha; Méndez, Francisco; Alonso, Julio A

    2016-02-12

    The Diels-Alder (DA) reaction provides an attractive route to increase the number of six member rings in substituted Polycyclic Aromatic Hydrocarbons (PAHs). The density functional theory (DFT) B3LYP method has been used in this work to inquire if the substitution of H over the edge of triindenetriphenylene (pristine hemifullerene 1) and pentacyclopentacorannulene (pristine hemifullerene 2), could improve the DA cycloaddition reaction with 1,3-butadiene. The substituents tested include electron-donating (NH₂, OMe, OH, Me, i-Pr) and electron-withdrawing groups (F, COOH, CF₃, CHO, CN, NO₂). The electronic, kinetic and thermodynamic parameters of the DA reactions of the substituted hemifullerenes with 1,3-butadiene have been analyzed. The most promising results were obtained for the NO₂ substituent; the activation energy barriers for reactions using this substituent were lower than the barriers for the pristine hemifullerenes. This leads us to expect that the cycloadditions to a starting fullerene fragment will be possible.

  14. Photochemical generation of highly destabilized vinyl cations: the effects of alpha- and beta-trifluoromethyl versus alpha- and beta-methyl substituents

    NARCIS (Netherlands)

    Alem, van K.; Belder, G.; Lodder, G.; Zuilhof, H.

    2005-01-01

    The photochemical reactions in methanol of the vinylic halides 1-4, halostyrenes with a methyl or a trifluoromethyl substituent at the - or -position, have been investigated quantitatively. Next to E/Z isomerization, the reactions are formation of vinyl radicals, leading to reductive dehalogenation

  15. Substituent effect in spin-crossover behavior of iron(II)-Ar-pybox complexes (Ar-pybox = 4-aryl-2,6-bis(oxazolin-2-yl)pyridine)

    Science.gov (United States)

    Kimura, Akifumi; Ishida, Takayuki

    2018-01-01

    Spin-crossover (SCO) is a reversible transition between low-spin (LS) and high-spin (HS) states by external stimuli like heat. The SCO behavior of [Fe(Ar-pybox)2](ClO4)2 was investigated, where Ar-pybox stands for 4-aryl-2,6-bis(oxazolin-2-yl)pyridine with Ar = 4-pyridyl (4Py), 3-thienyl (3Th), and phenyl (Ph). They were characterized by means of single-crystal X-ray diffraction study, being consistent with the results of the magnetic measurements. The SCO temperatures (T1/2) in the polycrystalline state were determined to be 360 and 230 K for Ar = 4Py and Ph, respectively. The 3Th derivative possessed a HS state in all the temperature range. The solution susceptometry was also performed to purge intermolecular interaction and rigid crystal lattice effects, affording T1/2 = 310, 240, and 240 K for Ar = 4Py, 3Th, and Ph, respectively, in acetone. The substituent effect analysis using the Hammett substituent constant (σp) clarified that electron-withdrawing groups raise T1/2. A plausible model describing the substituent effect on T1/2 is proposed based on d-π interaction. The present result is regarded as a successful example of crystal field engineering.

  16. Substituent effect on the oxidation peak potentials of phenol derivatives at ordered mesoporous carbons modified electrode and its application in determination of acidity coefficients (pKa)

    International Nuclear Information System (INIS)

    Zhang, Tingting; Lang, Qiaolin; Zeng, Lingxing; Li, Tie; Wei, Mingdeng; Liu, Aihua

    2014-01-01

    In this paper, the relationship between the electrochemical characteristics and the structure of a series of substituted phenol derivatives with electron-donating or electron-withdrawing groups were studied by voltammetry using ordered mesoporous carbons (OMCs) modified glassy carbon electrode (GCE) (OMCs/GCE). p-Nitrophenol (p-NP) and p-methylphenol were selected as models of electron-withdrawing and electron-donating groups, respectively, to illustrate the electrochemical behavior and reaction mechanism of substituted phenols. Voltammetric study showed that the oxidation peak potential (E pa ) of substituted phenols with an electron-withdrawing group was systematically higher than that of substituted phenols with an electron-donating group. That is, the direct electrochemical oxidation of substituted phenol with an electron-withdrawing group is more difficult than that of substituted phenol with an electron-donating group. The E pa value shifted negatively with the increase of pKa for both p-substituted phenols and o-substituted phenols with the equations of pKa = −6.986 E pa + 13.261 (for p-substituted phenols) and pKa = −7.929 E pa + 13.831 (for o-substituted phenols). Thus, a simple and novel method was proposed for the precise prediction of the pKa of substituted phenols by determining E pa values with voltammetry at OMCs/GCE, which matched fairly with the results calculated from Hammett's constants. Thus, the present work may provide additional strategy to determine pKa values and investigate possible mechanisms of some organic reactions. In addition, by making use of the substituent effect, different p-substituted phenols (or o-substituted phenols) can be well separated and identified at OMCs/GCE by voltametry, which may find possible applications in simultaneous detection of p-substituted phenols (or o-substituted phenols)

  17. IMIDAZOLE-BASED IONIC LIQUIDS FOR USE IN POLYMER ELECTROLYTE MEMBRANE FUEL CELLS: EFFECT OF ELECTRON-WITHDRAWING AND ELECTRON-DONATING SUBSTITUENTS

    Energy Technology Data Exchange (ETDEWEB)

    Chang, E.; Fu, Y.; Kerr, J.

    2009-01-01

    Current polymer electrolyte membrane fuel cells (PEMFCs) require humidifi cation for acceptable proton conductivity. Development of a novel polymer that is conductive without a water-based proton carrier is desirable for use in automobiles. Imidazole (Im) is a possible replacement for water as a proton solvent; Im can be tethered to the polymer structure by means of covalent bonds, thereby providing a solid state proton conducting membrane where the solvating groups do not leach out of the fuel cell. These covalent bonds can alter the electron availability of the Im molecule. This study investigates the effects of electron-withdrawing and electron-donating substituents on the conductivity of Im complexed with methanesulfonic acid (MSA) in the form of ionic liquids. Due to the changes in the electronegativity of nitrogen, it is expected that 2-phenylimidazole (2-PhIm, electron-withdrawing) will exhibit increased conductivity compared to Im, while 2-methylimidazole (2-MeIm, electron-donating) will exhibit decreased conductivity. Three sets of ionic liquids were prepared at defi ned molar ratios: Im-MSA, 2-PhIm-MSA, and 2-MeIm- MSA. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and 1H-NMR were used to characterize each complex. Impedance analysis was used to determine the conductivity of each complex. Both the 2-PhIm-MSA and 2-MeIm-MSA ionic liquids were found to be less conductive than the Im-MSA complex at base-rich compositions, but more conductive at acid-rich compositions. 1H-NMR data shows a downfi eld shift of the proton on nitrogen in 2-PhIm compared to Im, suggesting that other factors may diminish the electronic effects of the electron withdrawing group at base-rich compositions. Further studies examining these effects may well result in increased conductivity for Im-based complexes. Understanding the conductive properties of Im-derivatives due to electronic effects will help facilitate the development of a new electrolyte

  18. A 3D visualization of the substituent effect : A brief analysis of two components of the operational formula of dual descriptor for open-shell systems.

    Science.gov (United States)

    Martínez-Araya, Jorge I; Yepes, Diana; Jaque, Pablo

    2017-12-27

    Six organometallic compounds coming from a basic Mo-based complex were analyzed from the perspective of the dual descriptor in order to detect subtle influences that a substituent group could exert on the reactive core at a long range. Since the aforementioned complexes are open-shell systems, the used operational formula for the dual descriptor is that one defined for those aforementioned systems, which was then compared with spin density. In addition, dual descriptor was decomposed into two terms, each of which was also applied on every molecular system. The obtained results indicated that components of dual descriptor could become more useful than the operational formula of dual descriptor because differences exerted by the substituents at the para position were better detected by components of dual descriptor rather than the dual descriptor by itself.

  19. Effect of the substituents on the photophysical, electrochemical and electroluminescence properties of OLED dopant Iridium bis(2-phenylbenzothiozolato- N,C2')(acetylacetonate)

    Science.gov (United States)

    Ivanov, P.; Tomova, R.; Petrova, P.

    2014-12-01

    The effect of two substituents: clorine and 1,3-diphenylpropane-1,3-dionate, placed on different position in the molecule of Iridium (III) bis(2-phenylbenzothiozolato-N,C2')- (acetylacetonate) (bt)2Ir(acac), on its electrochemical behaviour, photophysical and electroluminescence properties were investigated. Three complexes (bt)2Ir(acac), Iridium (III) bis[2-(4-chlorophenyl)benzothiazolato-N,C2']-acetylacetonate (Clbt)2Ir(acac), in which the Cl atom was introduced on the 4-position in the benzothiazole ring, and the new Iridium (Ill) bis[2 -phenylbenzothiazolato -N,C2'] -(1,3 -diphenylpropane-1,3 -dionate) (bt)2Ir(dbm), where ancillary acetylacetonate ligand was replaced by 1,3-diphenylpropane-1,3-dionate, were synthesized and characterised by 1H-NMR and elemental analysis. The HOMO/LUMO energy levels of the complexes were determined by cyclic voltammetry (CV) and their properties were established by UV-Visible and fluorescence spectroscopy. The application of (Clbt)2Ir(acac), (bt)2Ir(bsm) and (bt)2Ir(acac) as dopants in hole transporting layer (HTL) of Organic light- emitting diodes(OLEDs). It was found that with respect to the reference (bt)2Ir(acac): both LUMO and HOMO of the substituted complexes were shifted to more positive values accordingly with 0.23 and 0.19 eV for (Clbt)2Ir(acac) and 0.14 and 0.12 eV for (bt)2Ir(dbm). OLEDs doped with 1 w% of the complexes irradiated the warm white light with Commission internationale de l'eclairage (CIE) coordinates: 0.24;0.38 for (Clbt)2Ir(acac), 0.30;0.44 for (bt)2Ir(acac) and 0.28;0.46 for (bt)2Ir(dbm). Devices doped with 10 w% of all complexes irradiated in the yellow orange region of the spectrum.

  20. DFT studies for the substituent effect on the diels-alder reaction of 1,4-diaza-1,3-butadienes

    International Nuclear Information System (INIS)

    Lee, Gab Yong

    2001-01-01

    DFT calculations have been performed on several substituted 1,4-diaza-1,3-butadienes (1,4-DABs) with electron donating and withdrawing groups at the terminal two nitrogens to investigate the reactivity of Diels-Alder reaction with acrolein. The calculated FMO (Frontier Molecular orbital) energies for the optimized 1,4-disubstituted-1,4DABs have been used to explain both normal and inverse electron demand Diels-Alder reactions. It is shown that the electron donating and withdrawing substituents lead to the normal(HOMO diene controlled) and inverse electron demand (LUMO diene controlled) Diels-Alder reactions, respectively

  1. Efficient approach to androstene-fused arylpyrazolines as potent antiproliferative agents. Experimental and theoretical studies of substituent effects on BF(3)-catalyzed intramolecular [3 + 2] cycloadditions of olefinic phenylhydrazones.

    Science.gov (United States)

    Frank, Eva; Mucsi, Zoltán; Zupkó, István; Réthy, Borbála; Falkay, George; Schneider, Gyula; Wölfling, János

    2009-03-25

    Highly diastereoselective Lewis acid induced intramolecular 1,3-dipolar cycloadditions of alkenyl phenylhydrazones (containing various substituents on the aromatic ring) obtained from a d-secopregnene aldehyde were carried out under fairly mild conditions to furnish androst-5-ene-fused arylpyrazolines in good to excellent yields. The ability of phenylhydrazones to undergo cyclization was found to be affected significantly by the electronic features of the substituents on the aromatic moiety. The rates of the ring-closure reactions were observed to be increased by electron-donating and decreased by electron-withdrawing groups. The experimental findings on the BF(3)-catalyzed transformations were supported by calculations of the proposed mechanism at the BLYP/6-31G(d) level of theory, indicating a noteworthy dependence, mainly of the initial complexation step, and hence of the whole process, on the character of the substituent. The cycloaddition was estimated to occur via a zwitterionic intermediate rather than involving a pure concerted mechanism. The antiproliferative activities of the structurally related pyrazoline derivatives were tested in vitro on three malignant human cell lines (HeLa, MCF7, and A431): the microculture tetrazolium assay revealed that several compounds exerted marked cell growth-inhibitory effects. The highest cytotoxic activities, displayed by the p-methoxyphenylpyrazoline derivative 7d (IC(50) values: 2.01, 2.16, and 1.41 microM on HeLa, MCF7, and A341 cells, respectively), were better than those of cisplatin (IC(50) values: 12.43, 9.63, and 2.84 microM, respectively).

  2. Achieving blue luminescence of Alq3 through the pull-push effect of the electron-withdrawing and electron-donating substituents

    International Nuclear Information System (INIS)

    Shi Minmin; Lin Jiajun; Shi Yuewen; Ouyang Mi; Wang Mang; Chen Hongzheng

    2009-01-01

    A novel blue-emissive Alq 3 derivative, tris-(4-methyl-6-fluoro-8-hydroxyquinoline) aluminum (6), has been designed and prepared. Because the strong electronegative F atom at 6-position lowers the HOMO significantly and the weak electron-donating methyl group at 4-position retains the drop of the LUMO, the band gap of 6 is broadened, and a blue-shift by 53 nm of the emission peak (λ em ) with substantially enhanced intensity is demonstrated when compared to that of Alq 3 . It is also found that 6 possesses good thermal stability and solubility in common solvents. Through theoretical simulations of the frontier orbitals, it is disclosed that 6's λ em can be blue-shifted further if methyl is replaced with a stronger electron-donating substituent, such as methoxy or N,N'-dimethylamino group.

  3. Heteroleptic and Homoleptic Iron(III Spin-Crossover Complexes; Effects of Ligand Substituents and Intermolecular Interactions between Co-Cation/Anion and the Complex

    Directory of Open Access Journals (Sweden)

    Wasinee Phonsri

    2017-08-01

    Full Text Available The structural and magnetic properties of a range of new iron(III bis-tridentate Schiff base complexes are described with emphasis on how intermolecular structural interactions influence spin states and spin crossover (SCO in these d5 materials. Three pairs of complexes were investigated. The first pair are the neutral, heteroleptic complexes [Fe(3-OMe-SalEen(thsa] 1 and [Fe(3-MeOSalEen(3-EtOthsa] 2, where 3-R-HSalEen = (E-2-(((2-(ethylaminoethyliminomethyl-6-R-phenol and 3-R-H2thsa = thiosemicarbazone-3-R-salicylaldimine. They display spin transitions above room temperature. However, 2 shows incomplete and gradual change, while SCO in 1 is complete and more abrupt. Lower cooperativity in 2 is ascribed to the lack of π–π interactions, compared to 1. The second pair, cationic species [Fe(3-EtOSalEen2]NO3 3 and [Fe(3-EtOSalEen2]Cl 4 differ only in the counter-anion. They show partial SCO above room temperature with 3 displaying a sharp transition at 343 K. Weak hydrogen bonds from cation to Cl− probably lead to weaker cooperativity in 4. The last pair, CsH2O[Fe(3-MeO-thsa2] 5 and Cs(H2O2[Fe(5-NO2-thsa2] 6, are anionic homoleptic chelates that have different substituents on the salicylaldiminate rings of thsa2−. The Cs cations bond to O atoms of water and the ligands, in unusual ways thus forming attractive 1D and 3D networks in 5 and 6, respectively, and 5 remains HS (high spin at all temperatures while 6 remains LS (low spin. Comparisons are made to other literature examples of Cs salts of [Fe(5-R-thsa2]− (R = H and Br.

  4. Acid- and base-catalysis in the mononuclear rearrangement of some (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole in toluene: effect of substituents on the course of reaction.

    Science.gov (United States)

    D'Anna, Francesca; Frenna, Vincenzo; Ghelfi, Franco; Marullo, Salvatore; Spinelli, Domenico

    2011-04-15

    The reaction rates for the rearrangement of eleven (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole 3a-k into the relevant (2-aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas 4a-k in the presence of trichloroacetic acid or of piperidine have been determined in toluene at 313.1 K. The results have been related to the effect of the aryl substituent by using Hammett and/or Ingold-Yukawa-Tsuno correlations and have been compared with those previously collected in a protic polar solvent (dioxane/water) as well as with those on the analogous rearrangement of the corresponding (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole 1a-k in benzene. Some light can thus be shed on the general differences of chemical reactivity between protic polar (or dipolar aprotic) and apolar solvents.

  5. α-deuterium isotope effects in benzyl halides. 2. Reaction of nucleophiles with substituted benzyl bromides. Evidence for a change in transition-state structure with electron-donating substituents

    International Nuclear Information System (INIS)

    Vitullo, V.P.; Grabowski, J.; Sridharan, S.

    1980-01-01

    Rates and α-D isotope effects have been determined for the following substrates and nucleophiles: p-methoxybenzyl bromide (Et 3 N, SCN - , N 3 - , OH - , S 2 O 3 2- ), benzyl bromide (Et 3 N, SCN - , N 3 - , OH - , S 2 O 3 2- ), and p-nitrobenzyl bromide (Et 3 N, SCN - , N 3 - , S 2 O 3 2- ). In nearly all cases the second-order rate constant for each nucleophile goes through a minimum for the unsubstituted compound while the α-D isotope increases monotonically in the squence p-NO 2 > p-H > p-OCH 3 . These results are consistent with an increasing looseness of the S/sub N/2 transition state as the substituent on the aromatic ring becomes more electron donating. 4 figures, 3 tables

  6. World Wide Web-based system for the calculation of substituent parameters and substituent similarity searches.

    Science.gov (United States)

    Ertl, P

    1998-02-01

    Easy to use, interactive, and platform-independent WWW-based tools are ideal for development of chemical applications. By using the newly emerging Web technologies such as Java applets and sophisticated scripting, it is possible to deliver powerful molecular processing capabilities directly to the desk of synthetic organic chemists. In Novartis Crop Protection in Basel, a Web-based molecular modelling system has been in use since 1995. In this article two new modules of this system are presented: a program for interactive calculation of important hydrophobic, electronic, and steric properties of organic substituents, and a module for substituent similarity searches enabling the identification of bioisosteric functional groups. Various possible applications of calculated substituent parameters are also discussed, including automatic design of molecules with the desired properties and creation of targeted virtual combinatorial libraries.

  7. Stereoelectronic and conformational effects in carbohydrate derived oxocarbenium, iminium and ammonium ions

    NARCIS (Netherlands)

    Rijssel, Erwin Roelof van

    2015-01-01

    Carbohydrates or sugars, the most diverse class of biopolymers, are involved in many different biological processes. To be able to study these processes, well defined sugar structures are required. The synthesis of these sugar structures is at this moment far from ideal and therefore requires

  8. Substituent Effects on Regioselectivity of the Diels-Alder Reactions: Reactions of 10-Allyl-1,8-dichloroanthracene with 2-Chloroacrylonitrile, 1-Cyanovinyl Acetate and Phenyl Vinyl Sulfone

    Directory of Open Access Journals (Sweden)

    Mujeeb A. Sultan

    2016-01-01

    Full Text Available Diels-Alder reaction of 10-allyl-1,8-dichloroanthracene (3 with 2-chloroacrylonitrile (4 and 1-cyanovinyl acetate (5 gives exclusively the ortho isomer while its reaction with phenyl vinyl sulfone (10 yields a mixture of two isomeric adducts with priority to ortho isomer. The reactions proceeded under microwave condition in xylene. Configurations of these isomers have been assigned with the help of NMR spectra. The results indicated that the steric effect is dominating toward the isomer regioselectivity in the Diels-Alder reaction of the present compounds.

  9. THEORETICAL RESEARCH ON EFFECTS OF SUBSTITUENTS ...

    African Journals Online (AJOL)

    The presence of dimethylsulfoxide (DMSO) can reduce the binding energy of the complex through .... The binding energy of complex 11 is less than that of complex 1 because the number of ..... Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; ... J. Chinese Universities 2004, 25, 539. 20.

  10. THEORETICAL RESEARCH ON EFFECTS OF SUBSTITUENTS ...

    African Journals Online (AJOL)

    Semiempirical AM1 and INDO/CIS methods were used to study the structures and spectroscopy of hydrogen bonded complexes formed by the oligophenyleneethynylene (monomer A) with isophthalic acid (monomer B). The binding energies of the complexes are lowered by increasing electron-donating abilities of the ...

  11. Chalcogenidobis(ene-1,2-dithiolate)molybdenum(IV) complexes (chalcogenide E = O, S, Se): probing Mo≡E and ene-1,2-dithiolate substituent effects on geometric and electronic structure.

    Science.gov (United States)

    Sugimoto, Hideki; Tano, Hiroyuki; Suyama, Koichiro; Kobayashi, Tomoya; Miyake, Hiroyuki; Itoh, Shinobu; Mtei, Regina P; Kirk, Martin L

    2011-02-07

    New square-pyramidal bis(ene-1,2-dithiolate)MoSe complexes, [Mo(IV)Se(L)(2)](2-), have been synthesised along with their terminal sulfido analogues, [Mo(IV)S(L)(2)](2-), using alkyl (L(C(4)H(8))), phenyl (L(Ph)) and methyl carboxylate (L(COOMe)) substituted dithiolene ligands (L). These complexes now complete three sets of Mo(IV)O, Mo(IV)S and Mo(IV)Se species that are coordinated with identical ene-1,2-dithiolate ligands. The [alkyl substituted Mo(S/Se)(L(C(4)H(8)))(2)](2-) complexes were reported in prior investigations (H. Sugimoto, T. Sakurai, H. Miyake, K. Tanaka and H. Tsukube, Inorg. Chem. 2005, 44, 6927, H. Tano, R. Tajima, H. Miyake, S. Itoh and H. Sugimoto, Inorg. Chem. 2008, 47, 7465). The new series of complexes enable a systematic investigation of terminal chalcogenido and supporting ene-1,2-dithiolate ligand effects on geometric structure, electronic structure, and spectroscopic properties. X-ray crystallographic analysis of these (Et(4)N)(2)[MoEL(2)] (E = terminal chalocogenide) complexes reveals an isostructural Mo centre that adopts a distorted square pyramidal geometry. The M≡E bond distances observed in the crystal structures and the ν(M≡E) vibrational frequencies indicate that these bonds are weakened with an increase in L→Mo electron donation (L(COOMe) < L(Ph) < L(C(4)H(8))), and this order is confirmed by an electrochemical study of the complexes. The (77)Se NMR resonances in MoSeL complexes appear at lower magnetic fields as the selenido ion became less basic from MoSeL(C(4)H(8)), MoSeL(Ph) and MoSeL(COOMe). Electronic absorption and resonance Raman spectroscopies have been used to assign key ligand-field, MLCT, LMCT and intraligand CT bands in complexes that possess the L(COOMe) ligand. The presence of low-energy intraligand CT transition in these MoEL(COOMe) compounds directly probes the electron withdrawing nature of the -COOMe substituents, and this underscores the complex electronic structure of square pyramidal bis(ene-1

  12. Substituent effif ects on hydrogen bonding in Watson-Crick base pairs. A theoretical study

    NARCIS (Netherlands)

    Fonseca Guerra, C.; van der Wijst, T.; Bickelhaupt, F.M.

    2005-01-01

    We have theoretically analyzed Watson-Crick AT and GC base pairs in which purine C8 and/or pyrimidine C6 positions carry a substituent X = H, F, Cl or Br, using the generalized gradient approximation (GGA) of density functional theory at BP86/TZ2P. The purpose is to study the effects on structure

  13. Cis–Trans Amide Bond Rotamers in β-Peptoids and Peptoids: Evaluation of Stereoelectronic

    DEFF Research Database (Denmark)

    Laursen, Jonas Striegler; Engel-Andreasen, Jens; Fristrup, Peter

    2013-01-01

    to folding propensity. Thus, we here report an investigation of the effect of structural variations on the cis–trans amide bond rotamer equilibria in a selection of monomer model systems. In addition to various side chain effects, which correlated well with previous studies of α-peptoids, we present...... the synthesis and investigation of cis–trans isomerism in the first examples of peptoids and β-peptoids containing thioamide bonds as well as trifluoroacetylated peptoids and β-peptoids. These systems revealed an increase in the preference for cis-amides as compared to their parent compounds, and thus provide...

  14. Effect of methyl substituents on the electronic transitions in simple meso-aniline-BODIPY based dyes: RI-CC2 and TD-CAM-B3LYP computational investigation

    Science.gov (United States)

    Petrushenko, Igor K.; Petrushenko, Konstantin B.

    2018-02-01

    The S0 → Si, i = 1-5 electronic transitions of four 8-(4-aniline)-BODIPY and four 8-(N,N-dimethyl)-BODIPY dyes, differ by number and position of methyl substituents in the BODIPY frame, were investigated theoretically using ab initio the coupled cluster doubles (CC2) and TD-CAM-B3LYP methods. Methyl substituents in the BODIPY frame and the aniline fragment at the meso position disturb energy of local excitations S0 → S1, S0 → S3, and S0 → S4 weakly in comparison with the fully unsubstituted BODIPY molecule. These transitions in experimental spectra form the most long-wave absorption bands at ca. 500 nm as well as absorption bands in the region of 300-400 nm. At the same time, the presence of aniline fragments leads to the appearance of new S0 → S2 transitions of the charge transfer character in electronic spectra of BODIPYs. We also found a linear relationship between vertical energy of these charge transfer transitions and the electron donating power of an aniline fragment and electron accepting power of the BODIPY core depending on the number and position of methyl groups. The CC2 method provides the best overall description of the excitation energies in line with the experimental observations. On average, the quality of TD-CAM-B3LYP is almost equal to that of CC2, however the TD method with the CAM-B3LYP functional slightly underestimates the CT excitation energy.

  15. Interaction of albumin with perylene-diimides with aromatic substituents

    Science.gov (United States)

    Farooqi, Mohammed; Penick, Mark; Burch, Jessica; Negrete, George; Brancaleon, Lorenzo

    2015-03-01

    Polyaromatic hydrocarbons (PAH) binding to proteins remains one of the fundamental aspects of research in biophysics. Ligand binding can regulate the function of proteins. Binding to small ligands remains a very important aspect in the study of the function of many proteins. Perylene diimide or PDI derivatives have attracted initial interest as industrial dyes and pigments. Recently, much attention has been focused on their strong π - π stacks resulting from the large PDI aromatic core. These PDI stacks have distinct optical properties, and provide informative models that mimic the light-harvesting system and initial charge separation and charge transfer in the photosynthetic system. The absorption property of PDI derivatives may be largely tuned from visible to near-infrared region by chemical modifications at the bay-positions. We are currently studying a new class of PDI derivatives with substituents made of the side chains of aromatic amino acids (Tyrosine, Tryptophan and Phenylalanine). We have looked at the fluorescence absorption and emission of these PDIs in water and other organic solvents. PDIs show evidence of dimerization and possible aggregation. We also present binding studies of these PDIs with Human Serum Albumin (HSA). The binding was studied using fluorescence emission quenching of the HSA Tryptophan residue. Stern-Volmer equation is used to derive the quenching constants. PDI binding to HSA also has an effect on the fluorescence emission of the PDIs themselves by red shifting the spectra. Funded by RCMI grant.

  16. Fine-Tuning of Saponification-Triggered Gelation by Strategic Modification of Peripheral Substituents: Gelation Regulators.

    Science.gov (United States)

    Kumar, Ashish; Singh, Roop Shikha; Kumar, Amit; Ali, Afsar; Biswas, Arnab; Pandey, Daya Shankar

    2016-09-19

    A pioneering approach towards controlling the efficiency of saponification assisted gelation in ethyl ester based Zn II -complexes have been described. Using four new ester containing bis-salen Zn II complexes (C1-C4) involving different para-azo phenyl substituted ligands it has been clearly shown that gelation efficiency is greatly influenced by the electronic effects of the substituents (-H (C1), -CH 3 (C2), -NO 2 (C3), and -OCH 3 (C4)). Morphological, photophysical, and rheological investigations corroborated the experimental observations well and established that gelation efficiency was enhanced with electron-withdrawing characteristics of substituents (C4

  17. Organic Semiconductors and Conductors with tert-Butyl Substituents

    Directory of Open Access Journals (Sweden)

    Toshiki Higashino

    2012-08-01

    Full Text Available Tetrathiafulvalene (TTF, pentacene, and quarterthiophene with tert-butyl substituents are synthesized, and the crystal structures and the transistor properties are investigated. The tetracyanoquinodimethane (TCNQ complex of tert-butyl TTF constructs highly one-dimensional segregated columns with tetragonal crystal symmetry.

  18. Synthesis and Crystal Structures of Dimethylsilylene-Bridged (Amidocyclopentadienyl)Dichlorotitanium(IV) Complexes with Various Substituents on the Cyclopentadienyl Ligand

    Czech Academy of Sciences Publication Activity Database

    Zemánek, Jaroslav; Štěpnička, P.; Fejfarová, K.; Gyepes, R.; Císařová, I.; Horáček, Michal; Kubišta, Jiří; Varga, V.; Mach, Karel

    2001-01-01

    Roč. 66, č. 4 (2001), s. 605-620 ISSN 0010-0765 R&D Projects: GA AV ČR IBS4040017 Institutional research plan: CEZ:AV0Z4040901 Keywords : titanium * (amidocyclopentadienyl)dichlorotitanium(IV) complexes * substituent effects Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.778, year: 2001

  19. Disclosure of key stereoelectronic factors for efficient H2 binding and cleavage in the active site of [NiFe]-hydrogenases.

    Science.gov (United States)

    Bruschi, Maurizio; Tiberti, Matteo; Guerra, Alessandro; De Gioia, Luca

    2014-02-05

    A comparative analysis of a series of DFT models of [NiFe]-hydrogenases, ranging from minimal NiFe clusters to very large systems including both the first and second coordination sphere of the bimetallic cofactor, was carried out with the aim of unraveling which stereoelectronic properties of the active site of [NiFe]-hydrogenases are crucial for efficient H2 binding and cleavage. H2 binding to the Ni-SIa redox state is energetically favored (by 4.0 kcal mol(-1)) only when H2 binds to Ni, the NiFe metal cluster is in a low spin state, and the Ni cysteine ligands have a peculiar seesaw coordination geometry, which in the enzyme is stabilized by the protein environment. The influence of the Ni coordination geometry on the H2 binding affinity was then quantitatively evaluated and rationalized analyzing frontier molecular orbitals and populations. Several plausible reaction pathways leading to H2 cleavage were also studied. It turned out that a two-step pathway, where H2 cleavage takes place on the Ni-SIa redox state of the enzyme, is characterized by very low reaction barriers and favorable reaction energies. More importantly, the seesaw coordination geometry of Ni was found to be a key feature for facile H2 cleavage. The discovery of the crucial influence of the Ni coordination geometry on H2 binding and activation in the active site of [NiFe]-hydrogenases could be exploited in the design of novel biomimetic synthetic catalysts.

  20. Spectroscopic study of 2-, 4- and 5-substituents on p Ka values of imidazole heterocycles prone to intramolecular proton-electrons transfer

    Science.gov (United States)

    Eseola, Abiodun O.; Obi-Egbedi, Nelson O.

    2010-02-01

    New 2-(1H-imidazol-2-yl)phenols ( L1Et- L8tBuPt) bearing a phenolic proton in the vicinity of the imidazole base were prepared and characterized. Experimental studies of the dependence of their protonation/deprotonation equilibrium on substituent identities and intramolecular hydrogen bonding tendencies were carried out using electronic absorption spectroscopy at varying pH values. In order to make comparison, 2-(anthracen-10-yl)-4,5-diphenyl-1H-imidazole ( L9Anthr) bearing no phenolic proton and 4,5-diphenyl-2-(4,5-diphenyl-1H-imidazol-2-yl)-1H-imidazole ( L10BisIm) bearing two symmetrical imidazole base fragments were also prepared and experimentally investigated. DFT calculations were carried out to study frontier orbitals of the investigated molecules. While electron-releasing substituents produced increase in protonation-deprotonation p Kas for the hydroxyl group, values for the imidazole base were mainly affected by polarization of the imidazole ring aromaticity across the 2-imidazole carbon and the 4,5-imidazole carbons axis of the imidazole ring. It was concluded that electron-releasing substituents on the phenol ring and/or electron-withdrawing substituents on 4,5-imidazole carbons negatively affects donor strengths/coordination chemistries of 2-(1H-imidazol-2-yl)phenols, and vice versa. Change of substituents on the phenol ring significantly altered the donor strength of the imidazole base. The understanding of p Ka variation on account of electronic effects of substituents in this work should aid the understanding of biochemical properties and substituent environments of imidazole-containing biomacromolecules.

  1. Correlating substituent parameter values to electron transport properties of molecules

    International Nuclear Information System (INIS)

    Vedova-Brook, Natalie; Matsunaga, Nikita; Sohlberg, Karl

    2004-01-01

    There are a vast number of organic compounds that could be considered for use in molecular electronics. Because of this, the need for efficient and economical screening tools has emerged. We demonstrate that the substituent parameter values (σ), commonly found in advanced organic chemistry textbooks, correlate strongly with features of the charge migration process, establishing them as useful indicators of electronic properties. Specifically, we report that ab initio derived electronic charge transfer values for 16 different substituted aromatic molecules for molecular junctions correlate to the σ values with a correlation coefficient squared (R 2 ) of 0.863

  2. Photoelectron spectra and electronic structure of nitrogen analogues of boron β-diketonates with aromatic substituents

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonov, Sergey A., E-mail: allser@bk.ru [Far Eastern Federal University, 8 Sukhanova St., Vladivostok, 690950 (Russian Federation); Vovna, Vitaliy I. [Far Eastern Federal University, 8 Sukhanova St., Vladivostok, 690950 (Russian Federation); Borisenko, Aleksandr V. [Vladivostok Branch of Russian Customs Academy, 16v Strelkovaya St., Vladivostok, 690034 (Russian Federation)

    2016-11-15

    Highlights: • The electronic structures of three nitrogen analogues of boron β-diketonates have been investigated. • UV photoelectron spectra have been interpreted. • The structure of the UV photoelectron spectra is in good agreement with the energies and compositions of Kohn-Sham orbitals. - Abstract: The electronic structure of three nitrogen analogoues of boron β-diketonates containing aromatic substituents was studied by the ultraviolet photoelectron spectroscopy and within the density functional theory. In order to determine effects of heteroatom substitution in the chelate ligand, a comparative analysis was carried out for the electronic structure of three model compounds. In a range of model compounds, the HOMO's nature was revealed to be the same. The HOMO-1 orbital of nitrogen containing compounds is determined by the presence of lone electron pairs of nitrogen. In a range of the complexes under study, the influence of aromatic substituents on the electronic structure was defined. In the imidoylamidinate complex, in contrast to formazanates and β-diketonates, it was found the absence of any noticeable mixing of π-orbitals of the chelate and benzene rings. It was shown that within energy range to 11 eV, the calculated results reproduce well the energy differences between the ionized states of complexes.

  3. The Influence of Substituent Orientation on the Photovoltaic Performance of Phthalocyanine-Sensitized Solar Cells.

    Science.gov (United States)

    Tejerina, Lara; Martínez-Díaz, M Victoria; Nazeeruddin, Mohammad Khaja; Torres, Tomas

    2016-03-18

    Phthalocyanines (Pcs) are used as sensitizers in dye-sensitized solar cells (DSSCs) because of their stability and intense absorption in the red and near-IR regions. Impressive progress has been made in photovoltaic efficiencies by introduction of bulky peripheral substituents to help suppress macrocycle aggregation. To reach benchmark efficiencies reported for other related dyes, new designs need to be explored. Single carboxy-ZnPc regioisomers substituted at the non-peripheral positions by rigid aryl groups have now been studied, which has shed light on the influence of steric hindrance and/or orientation of the substituent around the anchoring group on the photovoltaic response. The regioisomer bearing the aryl group far away from the anchoring group produces a more effective sensitization of the TiO2 films and higher short-circuit photocurrent density (Jsc). Taking advantage of the good photovoltaic performance in the near-IR region of this ZnPc, it was combined with another appropriate dye for panchromatic sensitization of the mesoporous photoelectrode and an increase of the overall device efficiency. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 15. Effects of the pyridyl substituents and fused exocyclic rings on the UV-visible spectroscopic properties of Mg(II)-porphyrazines: a combined experimental and DFT/TDDFT study.

    Science.gov (United States)

    Donzello, Maria Pia; De Mori, Giorgia; Viola, Elisa; Ercolani, Claudio; Ricciardi, Giampaolo; Rosa, Angela

    2014-08-04

    Two new Mg(II) porphyrazine macrocycles, the octakis(2-pyridyl)porphyrazinato-magnesium(II), [Py8PzMg(H2O)], and the tetrakis-[6,7-di(2-pyridyl)quinoxalino]porphyrazinato-magnesium(II), [Py8QxPzMg(H2O)], were prepared by Mg-template macrocyclization processes, and their general physicochemical properties were examined. The previously reported porphyrazine analog, the tetrakis-2,3-[5,6-di(2-pyridyl)-pyrazino]porphyrazinato-magnesium(II), [Py8PyzPzMg(H2O)], has been also considered in the present work. The UV-visible solution spectra in nonaqueous solvents of this triad of externally octapyridinated Mg(II) complexes exhibit the usual profile observed for phthalocyanine and porphyrazine macrocycles, with intense absorptions in the Soret (300-450 nm) and Q band (600-800 nm) regions. It is observed that the Q band maximum sensibly shifts toward the red with peak values at 635 → 658 → 759 nm along the series [Py8PzMg(H2O)], [Py8PyzPzMg(H2O)], and [Py8QxPzMg(H2O)], as the extension of the macrocycle π-system increases. TDDFT calculations of the electronic absorption spectra were performed for the related water-free model compounds [Py8PzMg], [Py8PyzPzMg], and [Py8QxPzMg] to provide an interpretation of the UV-visible spectral changes occurring upon introduction of the pyrazine and quinoxaline rings at the periphery of the Pz macrocycle. To discriminate the electronic effects of the fused exocyclic rings from those of the appended 2-pyridyl rings, the UV-visible spectra of [PzMg] and [PyzPzMg] were also theoretically investigated. The theoretical results prove to agree very well with the experimental data, providing an accurate description of the UV-visible spectra. The observed spectral changes are interpreted on the basis of the electronic structure changes occurring along the series.

  5. Substituent distribution within cross-linked and hydroxypropylated sweet potato starch and potato starch

    NARCIS (Netherlands)

    Zhao, J.; Schols, H.A.; Chen Zenghong,; Jin Zhengyu,; Buwalda, P.L.; Gruppen, H.

    2012-01-01

    Revealing the substituents distribution within starch can help to understand the changes of starch properties after modification. The distribution of substituents over cross-linked and hydroxypropylated sweet potato starch was investigated and compared with modified potato starch. The starches were

  6. Photostability enhancement of the pentacene derivative having two nitronyl nitroxide radical substituents.

    Science.gov (United States)

    Shimizu, Akihiro; Ito, Akitaka; Teki, Yoshio

    2016-02-18

    Pentacene derivatives possessing nitronyl nitroxide radical substituents (1a and 1b) were synthesized, and their photochemical properties were evaluated. 1a with two radical substituents showed a remarkable enhancement of photostability compared with pentacene, 6,13-bis(triisopropylsilylethynyl)pentacene and the monoradical, 1b. This is understood due to the presence of the multiple deactivation pathways in the photoexcited states.

  7. Ring substituents mediate the morphology of PBDTTPD-PCBM bulk-heterojunction solar cells

    KAUST Repository

    Warnan, Julien

    2014-04-08

    Among π-conjugated polymer donors for efficient bulk-heterojunction (BHJ) solar cell applications, poly(benzo[1,2-b:4,5-b′]dithiophene- thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers yield some of the highest open-circuit voltages (VOC, ca. 0.9 V) and fill-factors (FF, ca. 70%) in conventional (single-cell) BHJ devices with PCBM acceptors. In PBDTTPD, side chains of varying size and branching affect polymer self-assembly, nanostructural order, and impact material performance. However, the role of the polymer side-chain pattern in the intimate mixing between polymer donors and PCBM acceptors, and on the development of the BHJ morphology is in general less understood. In this contribution, we show that ring substituents such as furan (F), thiophene (T) and selenophene (S)-incorporated into the side chains of PBDTTPD polymers-can induce significant and, of importance, very different morphological effects in BHJs with PCBM. A combination of experimental and theoretical (via density functional theory) characterizations sheds light on how varying the heteroatom of the ring substituents impacts (i) the preferred side-chain configurations and (ii) the ionization, electronic, and optical properties of the PBDTTPD polymers. In parallel, we find that the PBDT(X)TPD analogs (with X = F, T, or S) span a broad range of power conversion efficiencies (PCEs, 3-6.5%) in optimized devices with improved thin-film morphologies via the use of 1,8-diiodooctane (DIO), and discuss that persistent morphological impediments at the nanoscale can be at the origin of the spread in PCE across optimized PBDT(X)TPD-based devices. With their high VOC ∼1 V, PBDT(X)TPD polymers are promising candidates for use in the high-band gap cell of tandem solar cells. © 2014 American Chemical Society.

  8. Ring substituents mediate the morphology of PBDTTPD-PCBM bulk-heterojunction solar cells

    KAUST Repository

    Warnan, Julien; El Labban, Abdulrahman; Cabanetos, Clement; Hoke, Eric T.; Shukla, Pradeep Kumar; Risko, Chad; Bré das, Jean Luc; McGehee, Michael D.; Beaujuge, Pierre

    2014-01-01

    Among π-conjugated polymer donors for efficient bulk-heterojunction (BHJ) solar cell applications, poly(benzo[1,2-b:4,5-b′]dithiophene- thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers yield some of the highest open-circuit voltages (VOC, ca. 0.9 V) and fill-factors (FF, ca. 70%) in conventional (single-cell) BHJ devices with PCBM acceptors. In PBDTTPD, side chains of varying size and branching affect polymer self-assembly, nanostructural order, and impact material performance. However, the role of the polymer side-chain pattern in the intimate mixing between polymer donors and PCBM acceptors, and on the development of the BHJ morphology is in general less understood. In this contribution, we show that ring substituents such as furan (F), thiophene (T) and selenophene (S)-incorporated into the side chains of PBDTTPD polymers-can induce significant and, of importance, very different morphological effects in BHJs with PCBM. A combination of experimental and theoretical (via density functional theory) characterizations sheds light on how varying the heteroatom of the ring substituents impacts (i) the preferred side-chain configurations and (ii) the ionization, electronic, and optical properties of the PBDTTPD polymers. In parallel, we find that the PBDT(X)TPD analogs (with X = F, T, or S) span a broad range of power conversion efficiencies (PCEs, 3-6.5%) in optimized devices with improved thin-film morphologies via the use of 1,8-diiodooctane (DIO), and discuss that persistent morphological impediments at the nanoscale can be at the origin of the spread in PCE across optimized PBDT(X)TPD-based devices. With their high VOC ∼1 V, PBDT(X)TPD polymers are promising candidates for use in the high-band gap cell of tandem solar cells. © 2014 American Chemical Society.

  9. Interchain interactions in charged diacetylenic oligomers carrying bulk substituents revisited

    International Nuclear Information System (INIS)

    Ottonelli, M.; Izzo, G.M.M.; Comoretto, D.; Musso, G.F.; Dellepiane, G.

    2006-01-01

    We are studying how the electronic properties of an aggregate, built with conjugated oligomers carrying bulk substituents, are affected by intermolecular interactions. In this paper we apply the CEO (Collective Electronic Oscillator) method, on the basis of the semiempirical INDO/S Hamiltonian, to compute the electronic density matrix modifications following the photon absorption in a doubly charged cluster of two units of a fully carbazolyl-substituted oligodiacetylene tetramer, taken as a model system. The picture that had emerged from our previous calculations based on the less sophisticated CIS (Configuration Interaction including Singles) approach is seen to be confirmed. Despite the large separation between the backbones, a through-space charge transfer occurs between the two oligomers due to the fact that the excess charge, contrary to what is generally believed, is not localized on the conjugated backbone, but is spread out over the carbazolyl moieties of the charged molecule. Consideration of this kind of interaction improves the theoretical results obtained for the isolated charged oligomer chain, and aids in better explaining some features of the experimental photoinduced spectra of the corresponding polymer

  10. Halogen–Metal Exchange on Bromoheterocyclics with Substituents Containing an Acidic Proton via Formation of a Magnesium Intermediate

    Directory of Open Access Journals (Sweden)

    Qingqiang Tian

    2017-11-01

    Full Text Available A selective and practical bromine–metal exchange on bromoheterocyclics bearing substituents with an acidic proton under non-cryogenic conditions was developed by a simple modification of an existing protocol. Our protocol of using a combination of i-PrMgCl and n-BuLi has not only solved the problem of intermolecular quenching that often occurred when using alkyl lithium alone as the reagent for halogen–lithium exchange, but also offered a highly selective method for performing bromo–metal exchange on dibrominated arene compounds through chelation effect.

  11. Competitive/co-operative interactions in acid base sandwich: role of cation vs. substituents.

    Science.gov (United States)

    Kalpana, Ayyavoo; Akilandeswari, Lakshminarayanan

    2017-11-15

    The cation-π interaction can be envisaged as a lewis acid base interaction, and it is in line with Pearson's acid base concept. The critical examination of interactions between the π-acids (alkali metal cations - Li + , Na + and alkaline earth metal cations Mg 2+ , Ca 2+ ) on one face and tripodal Cr(CO) 3 moiety on the other π face of substituted arenes demonstrates the role of cation and substitutents in manipulating the interactions between them. The interaction of the two π acids on both faces of arene is not expectedly additive, rather it shows either depreciation of interaction energy revealing the competition of acids toward the base or enhancement of interaction energy denoting a cooperative effect. Among the metal cations under study, Mg 2+ shows a cooperative gesture. Although the substituents play a meek role, they unfailingly exert their electronic effects and are amply documented by excellent correlation of various parameters with the Hammett constant σ m . The elusive switching of λ max from the UV to IR region on binding Mg 2+ with substituted arene-Cr(CO) 3 complex is a characteristic clue that TDDFT can help design the ionic sensors for Mg 2+ cations.

  12. Substituent-directed structural and physicochemical controls of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

    Science.gov (United States)

    Chang, Ho-Chol; Mochizuki, Katsunori; Kitagawa, Susumu

    2005-05-30

    A family of diruthenium complexes with ligand-unsupported Ru-Ru bonds has been systematically synthesized, and their crystal structures and physical properties have been examined. A simple, useful reaction between Ru2(OAc)4Cl (OAc- = acetate) and catechol derivatives in the presence of bases afforded a variety of diruthenium complexes, generally formulated as [Na(n){Ru2(R4Cat)4}] (n = 2 or 3; R4 = -F4, -Cl4, -Br4, -H4, -3,5-di-t-Bu, and -3,6-di-t-Bu; Cat(2-) = catecholate). The most characteristic feature of the complexes is the formation of short ligand-unsupported Ru-Ru bonds (2.140-2.273 A). These comprehensive studies were carried out to evaluate the effects of the oxidation states and the substituents governing the molecular structures and physicochemical properties. The Ru-Ru bond distances, rotational conformations, and bending structures of the complexes were successfully varied. The results presented in this manuscript clearly demonstrate that the complexes with ligand-unsupported Ru-Ru bonds can sensitively respond to redox reactions and ligand substituents on the basis of the greater degree of freedom in their molecular structures.

  13. Influence of different amino substituents in position 1 and 4 on spectroscopic and acid base properties of 9,10-anthraquinone moiety.

    Science.gov (United States)

    Wcisło, Anna; Niedziałkowski, Paweł; Wnuk, Elżbieta; Zarzeczańska, Dorota; Ossowski, Tadeusz

    2013-05-01

    A series of novel 1-amino and 1,4-diamino-9,10-anthraquinones, substituted with different alkyl groups, were synthesized as the result of alkylation with amino substituents. All the obtained aminoanthraquinone derivatives were characterized by NMR, IR spectroscopy and mass spectrometry. The spectroscopic properties of these compounds were determined by using UV-Vis spectroscopy in acetonitrile, and in the mixture of acetonitrile and methanol at different pH ranges. The effects of various substituents present in the newly developed anthraquinone derivatives and their ability to form hydrogen bonds between the carbonyl oxygen atom of anthraquinone moiety and nitrogen atom of N-H group in 1-aminoanthraquinone (1-AAQ) and 1,4-diaminoanthraquinone (1,4-DAAQ) were studied. Additionally, the effects of hydrogen bond formation between O-H group in hydroxyethylamino substituent and the carbonyl oxygen atom of anthraquinone were investigated. The spectroscopic behavior of the studied derivatives strongly depended on the solvent-solute interactions and the nature of solvent. The values of pKa for the new anthraquinones were determined by the combined potentiometric and spectrophotometric titration methods. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. π-face donation from the aromatic N-substituent of N-heterocyclic carbene ligands to metal and its role in catalysis

    KAUST Repository

    Credendino, Raffaele

    2012-05-16

    In this work, we calculate the redox potential in a series of Ir and Ru complexes bearing a N-heterocyclic carbene (NHC) ligand presenting different Y groups in the para position of the aromatic N-substituent. The calculated redox potentials excellently correlate with the experimental ΔE 1/2 potentials, offering a handle to rationalize the experimental findings. Analysis of the HOMO of the complexes before oxidation suggests that electron-donating Y groups destabilize the metal centered HOMO. Energy decomposition of the metal-NHC interaction indicates that electron-donating Y groups reinforce this interaction in the oxidized complexes. Analysis of the electron density in the reduced and oxidized states of representative complexes indicates a clear donation from the C ipso of the N-substituents to an empty d orbital on the metal. In case of the Ru complexes, this mechanism involves the Ru-alkylidene moiety. All of these results suggest that electron-donating Y groups render the aromatic N-substituent able to donate more density to electron-deficient metals through the C ipso atom. This conclusion suggests that electron-donating Y groups could stabilize higher oxidation states during catalysis. To test this hypothesis, we investigated the effect of differently donating Y groups in model reactions of Ru-catalyzed olefin metathesis and Pd-catalyzed C-C cross-coupling. Consistent with the experimental results, calculations indicate an easier reaction pathway if the N-substituent of the NHC ligand presents an electron-donating Y group. © 2012 American Chemical Society.

  15. Identification of substituent groups and related genes involved in salecan biosynthesis in Agrobacterium sp. ZX09.

    Science.gov (United States)

    Xu, Linxiang; Cheng, Rui; Li, Jing; Wang, Yang; Zhu, Bin; Ma, Shihong; Zhang, Weiming; Dong, Wei; Wang, Shiming; Zhang, Jianfa

    2017-01-01

    Salecan, a soluble β-1,3-D-glucan produced by a salt-tolerant strain Agrobacterium sp. ZX09, has been the subject of considerable interest in recent years because of its multiple bioactivities and unusual rheological properties in solution. In this study, both succinyl and pyruvyl substituent groups on salecan were identified by an enzymatic hydrolysis following nuclear magnetic resonance (NMR), HPLC, and MS analysis. The putative succinyltransferase gene (sleA) and pyruvyltransferase gene (sleV) were determined and cloned. Disruption of the sleA gene resulted in the absence of succinyl substituent groups on salecan. This defect could be complemented by expressing the sleA cloned in a plasmid. Thus, the sleA and sleV genes located in a 19.6-kb gene cluster may be involved in salecan biosynthesis. Despite the lack of succinyl substituents, the molecular mass of salecan generated by the sleA mutant did not substantially differ from that generated by the wild-type strain. Loss of succinyl substituents on salecan changed its rheological characteristics, especially a decrease in intrinsic viscosity.

  16. Molecules with Linear π-Conjugated Pathways between All Substituents : Omniconjugation

    NARCIS (Netherlands)

    Veen, Marleen H. van der; Rispens, Minze T.; Jonkman, Harry T.; Hummelen, Jan C.

    2004-01-01

    In this paper, omniconjugation is introduced as a topological phenomenon in π-conjugated systems. Omniconjugated molecules are defined by the fact that they provide direct and fully π-conjugated pathways between all substituents attached to them. Surprisingly, until now such topologies have never

  17. Functional dependency of structures of ionic liquids: do substituents govern the selectivity of enzymatic glycerolysis?

    DEFF Research Database (Denmark)

    Guo, Zheng; Chen, Biqiang; Murillo, Rafael López

    2006-01-01

    hydrophobic substituents and hydrophilic ethoxyl or hydroxyl moieties is found, respectively, to be essential for triglycerides (TG) dissolving and equilibrium shifting. The reactions in the ILs with cations consisting of long chain and free hydroxyl groups gave markedly higher conversion of TG and better...

  18. Evaluation of achiral templates with fluxional Brønsted basic substituents in enantioselective conjugate additions.

    Science.gov (United States)

    Adachi, Shinya; Takeda, Norihiko; Sibi, Mukund P

    2014-12-19

    Enantioselective conjugate addition of malononitrile to pyrazolidinone-derived enoates proceeds in excellent yields and high enantioselectivities. A comparison of fluxional substituents with and without a Brønsted basic site and their impact on selectivity is detailed. Molecular sieves as an additive were found to be essential to achieve high enantioselectivity.

  19. Role of substituents on the reactivity and electron density profile of ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 125; Issue 5. Role of substituents on the reactivity and electron density profile of diimine ligands: A density functional theory based study. Bhakti S Kulkarni Deepti Mishra Sourav Pal. Volume 125 Issue 5 September 2013 pp 1247-1258 ...

  20. Structural dependence of the multi-functionalized carbon nanotubes to the substituents on the grafted diazo compounds

    Science.gov (United States)

    Amiri, Rahebeh; Rasouli, Sousan; Ghasemi, Alireza; Eghbali, Babak; Mohammadi, Soutodeh

    2014-05-01

    Systematic studies on the covalent functionalization of multi-walled carbon nanotubes were performed by a series of azo molecules with different substituents. For this investigation, 4-substituted diazonium reagents have been used in the reaction with the functionalized multi-walled carbon nanotubes. We analyzed the effect of the substituted groups on the diazo component affinity in the grafting. Also, the structural differences of the final products were evaluated by visual dispersion test, UV-Vis absorption. Fourier transforms infrared, Raman, and several complementary techniques (scanning electron microscopy, thermal gravimetric analysis, and colorimetry test). Nuclear magnetic resonance spectroscopy has been used to confirm the allylic protons attached to the surface of carbon nanotubes after functionalization.

  1. The unique role of halogen substituents in the design of modern agrochemicals.

    Science.gov (United States)

    Jeschke, Peter

    2010-01-01

    The past 30 years have witnessed a period of significant expansion in the use of halogenated compounds in the field of agrochemical research and development. The introduction of halogens into active ingredients has become an important concept in the quest for a modern agrochemical with optimal efficacy, environmental safety, user friendliness and economic viability. Outstanding progress has been made, especially in synthetic methods for particular halogen-substituted key intermediates that were previously prohibitively expensive. Interestingly, there has been a rise in the number of commercial products containing 'mixed' halogens, e.g. one or more fluorine, chlorine, bromine or iodine atoms in addition to one or more further halogen atoms. Extrapolation of the current trend indicates that a definite growth is to be expected in fluorine-substituted agrochemicals throughout the twenty-first century. A number of these recently developed agrochemical candidates containing halogen substituents represent novel classes of chemical compounds with new modes of action. However, the complex structure-activity relationships associated with biologically active molecules mean that the introduction of halogens can lead to either an increase or a decrease in the efficacy of a compound, depending on its changed mode of action, physicochemical properties, target interaction or metabolic susceptibility and transformation. In spite of modern design concepts, it is still difficult to predict the sites in a molecule at which halogen substitution will result in optimal desired effects. This review describes comprehensively the successful utilisation of halogens and their unique role in the design of modern agrochemicals, exemplified by various commercial products from Bayer CropScience coming from different agrochemical areas.

  2. New aminoporphyrins bearing urea derivative substituents: synthesis, characterization, antibacterial and antifungal activity

    Directory of Open Access Journals (Sweden)

    Gholamreza Karimipour

    2015-06-01

    Full Text Available This work studied the synthesis of 5,10,15-tris(4-aminophenyl-20-(N,N-dialkyl/diaryl-N-phenylurea porphyrins (P1-P4 with alkyl or aryl groups of Ph, iPr, Et and Me, respectively and also the preparation of their manganese (III and cobalt (II complexes (MnP and CoP. The P1-P4 ligands were characterized by different spectroscopic techniques (1H NMR, FTIR, UV-Vis and elemental analysis, and metalated with Mn and Co acetate salts. The antibacterial and antifungal activities of these compounds in vitro were investigated by agar-disc diffusion method against Escherichia coli (-, Pseudomonas aeruginosa (-, Staphylococcus aureus(+, Bacillus subtilis (+ and Aspergillus oryzae and Candida albicans. Results showed that antibacterial and antifungal activity of the test samples increased with increase of their concentrations and the highest activity was obtained when the concentration of porphyrin compounds was 100 µg/mL. The activity for the porphyrin ligands depended on the nature of the urea derivative substituents and increased in the order P1 > P2 > P3 >P4, which was consistent with the order of their liposolubility. MnP and CoP complexes exhibited much higher antibacterial and antifungal activity than P1-P4ligands. Further, the growth inhibitory effects of these compounds was generally in the order CoP complexes > MnP complexes > P1-P4 ligands. Among these porphyrin compounds, CoP1displayed the highest antibacterial and antifungal activity, especially with a concentration of 100 µg/mL, against all the four tested bacteria and two fungi, and therefore it could be potential to be used as drug.

  3. Anaerobic C1 metabolism of the O-methyl-14C-labeled substituent of vanillate

    International Nuclear Information System (INIS)

    Frazer, A.C.; Young, L.Y.

    1986-01-01

    The O-methyl substituents of aromatic compounds constitute a C 1 growth substrate for a number of taxonomically diverse anaerobic acetogens. In this study, strain TH-001, an O-demethylating obligate anaerobe, was chosen to represent this physiological group, and the carbon flow when cells were grown on O-methyl substituents as a C 1 substrate was determined by 14 C radiotracer techniques. O-[methyl- 14 C]vanillate (4-hydroxy-3-methoxy-benzoate) was used as the labeled C 1 substrate. The data showed that for every O-methyl carbon converted to [ 14 C]acetate, two were oxidized to 14 CO 2 . Quantitation of the carbon recovered in the two products, acetate and CO 2 , indicated that acetate was formed in part by the fixation of unlabeled CO 2 . The specific activity of 14 C in acetate was 70% of that in the O-methyl substrate, suggesting that only one carbon of acetate was derived from the O-methyl group. Thus, it is postulated that the carboxyl carbon of the product acetate is derived from CO 2 and the methyl carbon is derived from the O-methyl substituent of vanillate

  4. Synthesis and Evaluation of Changes Induced by Solvent and Substituent in Electronic Absorption Spectra of New Azo Disperse Dyes Containig Barbiturate Ring

    Directory of Open Access Journals (Sweden)

    Hooshang Hamidian

    2013-01-01

    Full Text Available Six azo disperse dyes were prepared by diazotizing 4-amino hippuric acid and coupled with barbituric acid and 2-thiobarbituric acid. Then, the products were reacted with aromatic aldehyde, sodium acetate, and acetic anhydride, and oxazolone derivatives were formed. Characterization of the dyes was carried out by using UV-Vis, FT-IR, 1H NMR and 13C NMR, and mass spectroscopic techniques. The solvatochromic behavior of azo disperse dyes was evaluated in various solvents. The effects of substituents of aromatic aldehyde, barbiturate, and thiobarbiturate ring on the color of dyes were investigated.

  5. Carborane-stilbene dyads: the influence of substituents and cluster isomers on photoluminescence properties.

    Science.gov (United States)

    Ferrer-Ugalde, A; Cabrera-González, J; Juárez-Pérez, E J; Teixidor, F; Pérez-Inestrosa, E; Montenegro, J M; Sillanpää, R; Haukka, M; Núñez, R

    2017-02-14

    Two novel styrene-containing meta-carborane derivatives substituted at the second carbon cluster atom (C c ) with either a methyl (Me) or a phenyl (Ph) group are introduced herein along with a new set of stilbene-containing ortho- (o-) and meta- (m-) carborane dyads. The latter set of compounds have been prepared from styrene-containing carborane derivatives via a Heck coupling reaction. High regioselectivity has been achieved for these compounds by using a combination of palladium complexes [Pd 2 (dba) 3 ]/[Pd(t-Bu 3 P) 2 ] as a catalytic system, yielding exclusively E isomers. All compounds have been fully characterised and the crystal structures of seven of them were analysed by X-ray diffraction. The absorption spectra of these compounds are similar to those of their respective fluorophore groups (styrene or stilbene), showing a very small influence of the substituent (Me or Ph) linked to the second C c atom or the cluster isomer (o- or m-). On the other hand, fluorescence spectroscopy revealed high emission intensities for Me-o-carborane derivatives, whereas their Ph-o-carborane analogues evidenced an almost total lack of fluorescence, confirming the significant role of the substituent bound to the adjacent C c in o-carboranes. In contrast, all the m-carborane derivatives display similar photoluminescence (PL) behavior regardless of the substituent attached to the second C c , demonstrating its small influence on emission properties. Additionally, m-carborane derivatives are significantly more fluorescent than their o-counterparts, reaching quantum yield values as high as 30.2%. Regarding solid state emission, only stilbene-containing Ph-o-carborane derivatives, which showed very low fluorescence in solution, exhibited notable PL emission in films attributed to aggregation-induced emission. DFT calculations were performed to successfully complement the photoluminescence studies, supporting the experimentally observed photophysical behavior of the styrene and

  6. The Influence of Substituents on the Tautomerism of Symmetrically Substituted 2,2'-Bis-benzimidazoles

    Directory of Open Access Journals (Sweden)

    Dall'Oglio Evandro

    2002-01-01

    Full Text Available The tautomerism of five symmetrically substituted 2,2'-bis-benzimidazoles [5(6,5'(6'-tetramethyl- (1; 5(6,5'(6'-dimethyl-(2; 5(6,5'(6'-dichloro- (3; 5(6,5'(6'-dimethoxy- (4 and 4(7,4'(7'-dimethyl-2,2'-bis-benzimidazole (5], was studied by means of ¹H NMR spectroscopy at variable temperatures, and the influence of the substituents on the energy barriers for tautomeric interconversion was interpreted with the aid of theoretical calculations.

  7. Excited-state dynamics of pentacene derivatives with stable radical substituents.

    Science.gov (United States)

    Ito, Akitaka; Shimizu, Akihiro; Kishida, Noriaki; Kawanaka, Yusuke; Kosumi, Daisuke; Hashimoto, Hideki; Teki, Yoshio

    2014-06-23

    The excited-state dynamics of pentacene derivatives with stable radical substituents were evaluated in detail through transient absorption measurements. The derivatives showed ultrafast formation of triplet excited state(s) in the pentacene moiety from a photoexcited singlet state through the contributions of enhanced intersystem crossing and singlet fission. Detailed kinetic analyses for the transient absorption data were conducted to quantify the excited-state characteristics of the derivatives. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. The influence of different cyclometalated ligand substituents and ancillary ligand on the phosphorescent properties of iridium(III) complexes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qing; Li, Yuanyuan; Wang, Xin; Wang, Li, E-mail: chemwangl@henu.edu.cn; Zhang, Jinglai, E-mail: zhangjinglai@henu.edu.cn

    2016-07-01

    Four iridium(III) complexes, (dfpmpy){sub 2}Ir(pic), (1), (dfpmpy){sub 2}Ir(EO{sub 2}-pic) (2), (dfpmpy){sub 2}Ir(pic-N-O) (3), and (dfpmpy){sub 2}Ir(EO{sub 2}-pic-N-O) (4) (dfpmpy = 2-(2,4-difluorophenyl)-4-methylpyridine, pic = picolinic acid, EO{sub 2}-pic = 4-(2-ethoxyethoxy) picolinic acid, pic-N-O = picolinic acid N-oxide, and EO{sub 2}-pic-N-O = 4-(2-ethoxyethoxy) picolinic acid N-oxide) are investigated by means of the density functional theory/time-dependent density functional theory (DFT/TD-DFT) to explore the influence of the ancillary ligand on the electronic structures, phosphorescent properties, and organic light-emitting diode (OLED) performance. Employing pic-N-O and EO{sub 2}-pic-N-O as the ancillary ligands would decrease the vertical energy and result in the red-shifted wavelength. Then, other four iridium(III) complexes (2a-2d) (See Scheme 1) are designed by introduction of the phenyl and −CHO substituents on the pyridine ring and phenyl ring of complex 2, respectively. As compared with complex 2, theoretical results show that newly designed complexes 2a-2c might be potential candidates for blue-emitting phosphors with better/comparable quantum yield and Δλ. Moreover, the performance of complexes 2a and 2c, i.e., introducing phenyl on the para-position of pyridine ring and phenyl ring in dfpmpy ligand, are better than that of 2b. - Highlights: • The structure-property relationship of Ir(III) complexes are investigated. • The effect of different substituents/positions on properties is explored. • Do the emissions follow the Kasha or non-Kasha scenario? • Newly possible blue-emitting Ir(III) complexes are theoretically designed.

  9. A Computational Study of Structure and Reactivity of N-Substitued-4-Piperidones Curcumin Analogues and Their Radical Anions

    Directory of Open Access Journals (Sweden)

    Maximiliano Martínez-Cifuentes

    2016-12-01

    Full Text Available In this work, a computational study of a series of N-substitued-4-piperidones curcumin analogues is presented. The molecular structure of the neutral molecules and their radical anions, as well as their reactivity, are investigated. N-substituents include methyl and benzyl groups, while substituents on the aromatic rings cover electron-donor and electron-acceptor groups. Substitutions at the nitrogen atom do not significantly affect the geometry and frontier molecular orbitals (FMO energies of these molecules. On the other hand, substituents on the aromatic rings modify the distribution of FMO. In addition, they influence the capability of these molecules to attach an additional electron, which was studied through adiabatic (AEA and vertical electron affinities (VEA, as well as vertical detachment energy (VDE. To study electrophilic properties of these structures, local reactivity indices, such as Fukui (f+ and Parr (P+ functions, were calculated, and show the influence of the aromatic rings substituents on the reactivity of α,β-unsaturated ketones towards nucleophilic attack. This study has potential implications for the design of curcumin analogues based on a 4-piperidone core with desired reactivity.

  10. Stereoelectronic properties of aggregated chlorophyll systems

    Energy Technology Data Exchange (ETDEWEB)

    Christoffersen, R. E.; Maggiora, G. M.

    1979-09-01

    During the first nine months of the current contract, significant progress has occurred in several areas. All SCF CI studies of the singlet and triplet states of the neutral molecules Et-Chl a, Et-Pheo a, Et-BChl a, and Et-BPheo a, and the doublet states of the ..pi..-cation radicals Et-Chl a/sup +/. and Et-BChl a/sup +/. have now been completed. In addition, SCF CI calculations on BPheo a/sup -/. indicate that ..pi..-anion radicals can also be studied using the present approach. Similar work on a number of other ..pi..-cation and ..pi..-anion radicals is currently underway. Preliminary SCF CI studies have also been completed for benzoquinone and dihydroquinone, and studies on benzoquinone/sup -/. should be completed by the end of this year. The development and characterization of an empirical potential function is nearly complete, and data from selected systems is summarized. Implementation of a more efficient, quadratically convergent energy minimization procedure is also being carried out. This procedure should make it possible to study the geometry and properties of dimeric chlorophyll systems as well as various ligand-chlorophyll systems. Developmental work is continuing on the direct calculation of optical rotatory strengths.

  11. Exothermic or Endothermic Decomposition of Disubstituted Tetrazoles Tuned by Substitution Fashion and Substituents.

    Science.gov (United States)

    Jia, Yu-Hui; Yang, Kai-Xiang; Chen, Shi-Lu; Huang, Mu-Hua

    2018-01-11

    Nitrogen-rich compounds such as tetrazoles are widely used as candidates in gas-generating agents. However, the details of the differentiation of the two isomers of disubstituted tetrazoles are rarely studied, which is very important information for designing advanced materials based on tetrazoles. In this article, pairs of 2,5- and 1,5-disubstituted tetrazoles were carefully designed and prepared for study on their thermal decomposition behavior. Also, the substitution fashion of 2,5- and 1,5- and the substituents at C-5 position were found to affect the endothermic or exothermic properties. This is for the first time to the best of our knowledge that the thermal decomposition properties of different tetrazoles could be tuned by substitution ways and substitute groups, which could be used as a useful platform to design advanced materials for temperature-dependent rockets. The aza-Claisen rearrangement was proposed to understand the endothermic decomposition behavior.

  12. Tunable photoluminescent materials based on two phenylcarbazole-based dimers through the substituent groups

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Gui-Mei, E-mail: meiguit@163.com; Chi, Rui-Hai; Wan, Wen-Zhu; Chen, Zhi-Qiang; Yan, Ting-Xiang; Dong, Yan-Ping; Wang, Yong-Tao, E-mail: ceswyt@qlu.edu.cn; Cui, Yue-Zhi

    2017-05-15

    Two phenylcarbazole-based dimers, namely, 9,9'-diphenyl-9H,9'H−3,3'-bicarbazole (1) and 9,9'-bis(4-bromophenyl)−9H,9'H−3,3'-bicarbazole (2), have been obtained through the oxidation of 9-phenylcarbazole and 9-(4’-bromophenyl) in the presence of FeCl{sub 3}, respectively, which show strong photoluminescent properties with the fluorescence quantum yields of 0.2 and 0.21 based on the reference of Quinin sulfate, respectively. The maximal emission peak of compounds 1 and 2 were observed at 465 and 413 nm in the solid state, respectively, revealing that the luminescent properties were tuned by the substituent group. The title compounds were characterized by FI-IR, UV–vis, {sup 1}H-NMR, {sup 13}C-NMR, {sup 1}H−{sup 13}C NMR, mass spectra, elemental analysis (EA) and single-crystal X-ray diffraction. Both compounds 1 and 2 crystallize in space group P-1, and supramolecular hydrogen bondings and stacking interactions between aromatic rings are observed. Compounds 1 and 2 display trans- and cis-formation structures, respectively. Two compounds show high thermal stabilities, in which the decomposition temperature is 414 and 363 °C for 1 and 2, respectively. - Graphical abstract: Two phenylcarbazole-based dimers have been obtained through the oxidation of 9-phenylcarbazole and 9-(4’-bromophenyl) in the presence of FeCl{sub 3}, respectively. The maximal emission peaks of compounds 1 and 2 were observed at 465 and 413 nm, respectively, revealing that the luminescent properties were tuned by the substituent group. Compounds 1 and 2 display trans- and cis-formation structures, respectively, and they show high thermal stabilities.

  13. Amides with nitrogenous heterocyclic substituent, their manufacturing process and their use to draw out selectively Actinium series (III) and to separate them in particular from Lanthanides (III)

    International Nuclear Information System (INIS)

    Cuillerdier, C.; Musikas, C.

    1993-01-01

    Present invention is concerned with new amides with nitrogenous heterocyclic substituent utilizable to separate trivalent actinium series from trivalent lanthanides. In these molecules, it is possible to obtain particularly covalent liaison which has more affinity with 5f series, that is to say actinium series; included a manufacturing process for these amides with nitrogenous heterocyclic substituent

  14. New photoresponsive (meth)acrylate (co)polymers containing azobenzene pendant sidegroups with carboxylic and dimethylamino substituents .1. Synthesis and characterization of the monomers

    NARCIS (Netherlands)

    Haitjema, HJ; Buruma, R; VanEkenstein, GORA; Tan, YY; Challa, G

    1996-01-01

    New azobenzene-based (az.b.) monomers with CO2H (acid) or N(CH3)(2) (basic) substituents were synthesized. For some of these compounds new synthetic routes had to be developed, especially for the az.b. monomers with a CO2H substituent (azoacids) where their synthesis, purification and (thermal)

  15. Transition State Gauche Effects Control the Torquoselectivities of the Electrocyclizations of Chiral 1-Azatrienes.

    Science.gov (United States)

    Patel, Ashay; Vella, Joseph R; Ma, Zhi-Xiong; Hsung, R P; Houk, K N

    2015-12-04

    Hsung et al. have reported a series of torquoselective electrocyclizations of chiral 1-azahexa-1E,3Z,5E-trienes that yield functionalized dihydropyridines. To understand the origins of the torquoselectivities of these azaelectrocyclizations, we modeled these electrocyclic ring closures using the M06-2X density functional. A new stereochemical model that rationalizes the observed 1,2 stereoinduction emerges from these computations. This model is an improvement and generalization of the "inside-alkoxy" model used to rationalize stereoselectivities of the 1,3-dipolar cycloaddition of chiral allyl ethers and emphasizes a stabilizing hyperconjugative effect, which we have termed a transition state gauche effect. This stereoelectronic effect controls the conformational preferences at the electrocyclization transition states, and only in one of the allowed disrotatory electrocyclization transition states is the ideal stereoelectronic arrangement achieved without the introduction of a steric clash. Computational experiments confirm the role of this effect as a stereodeterminant since substrates with electropositive groups and electronegative groups have different conformational preferences at the transition state and undergo ring closure with divergent stereochemical outcomes. This predicted reversal of stereoselectivity for the ring closures of several silyl substituted azatrienes have been demonstrated experimentally.

  16. Molecular binding thermodynamics of spherical guests by β-cyclodextrins bearing aromatic substituents

    Energy Technology Data Exchange (ETDEWEB)

    Li, Nan; Chen, Yong; Zhang, Ying-Ming; Wang, Li-Hua; Mao, Wen-Zhao; Liu, Yu, E-mail: yuliu@nankai.edu.cn

    2014-01-20

    Graphical abstract: - Highlights: • Different conformation of β-CD derivatives. • Enthalpy gain. • High binding ability. - Abstract: The molecular binding behaviors of two β-cyclodextrin (β-CD) derivatives bearing 1,2,3-triazole moieties, i.e. mono-6-deoxy-6-{4-(8-oxymethylquinolino)[1,2,3]triazolyl}-β-CD (1) and mono-6-deoxy-6-{4-(8-oxymethylnaphthol)[1,2,3]triazolyl}-β-CD (3), and their analogs without 1,2,3-triazole moieties, i.e. mono-6-deoxy-6-(8-oxymethylquinolino)-β-CD (2) and mono-6-deoxy-6-(8-oxymethylnaphthol)-β-CD (4) toward spherical guests (±)-borneol and (±)-camphor were investigated to elucidate how substituent moiety of host affects the binding abilities by 2D NMR as well as microcalorimetric titrations in aqueous phosphate buffer solution (pH 7.20) at 298.15 K. The binding modes of host–guest interactions obtained from 2D NMR displayed that host CDs without triazole moieties gave better induce-fit efficiency between hosts and guests, leading to stronger binding abilities. Thermodynamically, the inclusion complexation was driven by enthalpy with the stoichiometry of 1:1. Another factor contributed to the enhanced binding abilities was the enthalpy gain with the smaller entropy loss.

  17. Influence of substituents in vinyl groups on reactivity of parylene during polymerization process

    International Nuclear Information System (INIS)

    Freza, Sylwia; Skurski, Piotr; Bobrowski, Maciej

    2010-01-01

    The MCSCF calculations indicate that both triplet and singlet state of biradical di-para-xylylene can exist during polymerization of parylene in gas phase and both can potentially react with vinyl molecules. The singlet-state open-shell dimer turned out to exhibit multiconfigurational character. In the case of triplet state of the dimer two mechanisms of the reactions with various species containing vinyl groups have been examined at the B3LYP/6-31G level. The kinetic and thermodynamical barriers have been estimated for the reaction path involving the π-bond cleavage as well as for the route describing the hydrogen atom transfer. It was found that the overall reactions are thermodynamically favorable, whereas appropriate kinetic barriers for certain derivatives are very small (close to 0 kcal/mol) which in turn makes allowances for easy reactivity under accessible conditions. The calculated mechanisms indicate the influence of substituents in vinyl groups for reactivity of parylene during LPCVD process.

  18. Influence of Introduced Substituents on the Anion-selectivity of [14]Tetraazaannulene Complexes.

    Science.gov (United States)

    Moriuchi-Kawakami, Takayo; Obita, Minako; Tsujinaka, Toshiki; Shibutani, Yasuhiko

    2015-01-01

    Nickel(II) complexes of [14]tetraazaannulene derivatives incorporating aromatic rings into their azaannulene framework were synthesized, and the anion-selectivity of the [14]tetraazaannulene nickel complexes 1 - 4 was evaluated by potentiometric measurements with solvent polymeric membrane electrodes. All of the [14]Tetraazaannulene nickel complexes, except 3, were found to exhibit high selectivity for the I(-) ion over the SCN(-) ion, although considerable interference of the ClO4(-) ion was observed in all 1 - 4 complexes. Concerning the anion-selectivities of 1 and 4, the incorporation of naphthalene rings into the azaannulene framework decreased not only the interference of the ClO4(-) ion but also the I(-) ion-selectivity over the SCN(-) ion. Comparison studies between the dibenzotetraaza[14]annulene nickel complexes 1 - 3 indicated that differences in the attached substituents of the [14]tetraazaannulene nickel complexes greatly influenced the ion-selectivity as ionophores. According to our computational results, the ionophoric properties of [14]tetraazaannulene nickel complexes 1 - 4 were influenced by their electrostatic properties rather than their topological properties.

  19. The effect of the fused-ring substituent on anthracene chalcones: crystal structural and DFT studies of 1-(anthracen-9-yl-3-(naphthalen-2-ylprop-2-en-1-one and 1-(anthracen-9-yl-3-(pyren-1-ylprop-2-en-1-one

    Directory of Open Access Journals (Sweden)

    Dian Alwani Zainuri

    2018-05-01

    Full Text Available The title chalcone compounds, C27H18O (I and C33H20O (II, were synthesized using a Claisen–Schmidt condensation. Both compounds display an s-trans configuration of the enone moiety. The crystal structures feature intermolecular C—H...O and C—H...π interactions. Quantum chemical analysis of density functional theory (DFT with a B3LYP/6–311++G(d,p basis set has been employed to study the structural properties of the compound. The effect of the intermolecular interactions in the solid state are responsible for the differences between the experimental and theoretical optimized geometrical parameters. The small HOMO–LUMO energy gap in (I (exp : 3.18 eV and DFT: 3.15 eV and (II (exp : 2.76 eV and DFT: 2.95 eV indicates the suitability of these compounds for optoelectronic applications. The intermolecular contacts and weak contributions to the supramolecular stabilization are analysed using Hirshfeld surface analysis.

  20. Influence of substituents of nickel(II) complexes of Schiff bases of substituted (S)-2-N-(benzylpropyl)aminobenzophenones and amino-acids on their asymmetric induction

    International Nuclear Information System (INIS)

    Nadvornik, M.; Lycka, A.; Gee, A.; Popkov, A.

    1999-01-01

    The aim of this work was to study of influence of substituents on benzophenone substituent on thermodynamic controlled induction of complexes as well as influence of substituents on benzyl group and on benzophenone on kinetically controlled asymmetric induction of complexes. [ 13 C]methyl iodide was used in the synthesis. Replace of benzyl group by 2,4,6-trimethylbenzyl group increase kinetically controlled asymmetric induction of synthesis of (S)-α-[ 13 C]methylalanine from 43% d.e. to 66% d.e

  1. Fluoroalkyl Amino Reagents (FARs: A General Approach towards the Synthesis of Heterocyclic Compounds Bearing Emergent Fluorinated Substituents

    Directory of Open Access Journals (Sweden)

    Bruno Commare

    2017-06-01

    Full Text Available Fluorinated heterocycles are important building blocks in pharmaceutical, agrochemical and material sciences. Therefore, organofluorine chemistry has witnessed high interest in the development of efficient methods for the introduction of emergent fluorinated substituents (EFS onto heterocycles. In this context, fluoroalkyl amino reagents (FARs—a class of chemicals that was slightly forgotten over the last decades—has emerged again recently and proved to be a powerful tool for the introduction of various fluorinated groups onto (heteroaromatic derivatives.

  2. Fluoroalkyl Amino Reagents (FARs): A General Approach towards the Synthesis of Heterocyclic Compounds Bearing Emergent Fluorinated Substituents.

    Science.gov (United States)

    Commare, Bruno; Schmitt, Etienne; Aribi, Fallia; Panossian, Armen; Vors, Jean-Pierre; Pazenok, Sergiy; Leroux, Frédéric R

    2017-06-12

    Fluorinated heterocycles are important building blocks in pharmaceutical, agrochemical and material sciences. Therefore, organofluorine chemistry has witnessed high interest in the development of efficient methods for the introduction of emergent fluorinated substituents (EFS) onto heterocycles. In this context, fluoroalkyl amino reagents (FARs)-a class of chemicals that was slightly forgotten over the last decades-has emerged again recently and proved to be a powerful tool for the introduction of various fluorinated groups onto (hetero)aromatic derivatives.

  3. Interaction between D-fructose dehydrogenase and methoxy-substituent-functionalized carbon surface to increase productive orientations

    International Nuclear Information System (INIS)

    Xia, Hong-qi; Hibino, Yuya; Kitazumi, Yuki; Shirai, Osamu; Kano, Kenji

    2016-01-01

    Highlights: • Methoxy-functionalized surface improves the DET-type bioelectrocatalysis of FDH. • Methoxy-functionalized surface increases productive orientations. • The total catalytic activity of FDH is almost independent of the modification. • High current density as well as good stability is useful for biofuel cells. - Abstract: D-Fructose dehydrogenase (FDH) from Gluconobacter japonicus NBRC3260 catalyzes the two-electron oxidation of D-fructose to 5-keto-D-fructose, and it is widely used in biofuel cells and biosensors. In this study, methoxy-substituent-functionalized carbon electrodes are constructed by electrochemical oxidation of methoxy-aniline derivatives on Ketjen Black (KB)-modified electrodes to improve the immobilization and bioelectrocatalysis of FDH. It is proposed that the specific interaction between FDH, especially the heme c moiety, and methoxy substituent(s) of amines on carbon electrode increases the proportion of the productively oriented FDH molecules to the total FDHs. Consequently, the limiting catalytic current density of the D-fructose oxidation increases to as much as 23 ± 2 mA cm −2 in FDH/2,4-dimethoxyaniline/KB/glassy carbon electrode, for example.

  4. Captodative aminoalkenes

    International Nuclear Information System (INIS)

    Rulev, Alexander Yu

    2002-01-01

    Procedures for the synthesis of captodative aminoalkenes, which were developed primarily over the last 15 years, are systematised. The influence of the structural and stereoelectronic effects of the substituents both at the nitrogen atom and at the double bond on the reactivity of these systems is considered. Particular emphasis is given to regio- and stereoselectivity of electrophilic, nucleophilic and radical reactions of captodative aminoalkenes as well as to processes of the construction of carbo- and heterocyclic compounds based on these aminoalkenes. A special section is devoted to the chemistry of methylidene- and arylmethylidenequinuclidin-3-ones. The bibliography includes 327 references.

  5. Effect of Cl substituent in the aromatic tetracycline ring on its reactivity with solvated electrons

    Energy Technology Data Exchange (ETDEWEB)

    Dziegielewski, J O; Glowacki, P [Universytet Slaski, Katowice (Poland). Inst. Chemii; Goracy, J; Orlowska-Dudek, D; Sloma, E [Wroclaw Univ. (Poland) Inst. Chemii

    1984-09-18

    Decomposition yields of tetracycline hydrochloride (TC.HCl) and chlorotetracycline hydrochloride (ClTC.HCl) in methanol solution saturated with Ar or N/sub 2/O were determined. Rate constants of the reaction esub(s)/sup -/ with some antibiotics were obtained. It was demonstrated by /sup 1/H NMR that the radical formed by degradation of 7-C-Cl group is recombined with the H atoms leading to ClTC.HCl being converted into tetracycline hydrochloride (TC.HCl).

  6. Electroreduction of aromatic oximes: Diprotonation, adsorption, imine formation, and substituent effects

    Czech Academy of Sciences Publication Activity Database

    Celik, H.; Ekmekci, F. G.; Ludvík, Jiří; Pícha, J.; Zuman, P.

    2006-01-01

    Roč. 110, č. 13 (2006), s. 6785-6796 ISSN 1520-6106 R&D Projects: GA AV ČR IAA4040304; GA MŠk 1P05ME785 Institutional research plan: CEZ:AV0Z40400503 Keywords : polarographic reduction * electrochemistry * electroorganic preparations Subject RIV: CG - Electrochemistry Impact factor: 4.115, year: 2006

  7. Substituent Effects on Hydrogen Bonds in DNA : A Kohn-Sham DFT Approach

    NARCIS (Netherlands)

    Guerra, Célia Fonseca; Bickelhaupt, F. Matthias

    2006-01-01

    In this Chapter, we discuss how the hydrogen bonds in Watson-Crick base pairs can be tuned both structurally and in terms of bond strength by exposing the DNA bases to different kinds of substitutions: (1) substitution in the X-H Y hydrogen bonding moiety, (2) remote substitution, i.e., introducing

  8. Substituent Effects and Bonding Characteristics in o- Benzoquinonediiminebis(bipyrdine) Ruthenium(II) Complexes

    Science.gov (United States)

    1992-10-23

    C.; Dei, A.; Gatteschi , D.; Pardi, L Inorg. Chem. 1989, 2L 1476; (b) Benel, C.; Dei, A.; Gatteschi , D.; Ckdel, H. U.; Pardi, L Inorg. Ckem. 1989, 28...3091; (c) Benelli, C.; Dei, A.; Gatteschi , D.; Pardi, L Inorg.Chem. 1990,2& 3409. 16. Bruni, S.; Cariati, F.; Dei, A.; Gatteschi , D. Inog Cbim. Ata...1991, 186 157. 17. Dei, A.; Gatteschi , D.; Pardi, L; Barra, A. L; Brunel, L C. Chem, Py. Lett.. 1990, 175. 589; Dei, A.; Pardi, L Inorg, Chim.Acta

  9. Photosensitive chiral self-assembling materials: significant effects of small lateral substituents

    Czech Academy of Sciences Publication Activity Database

    Cigl, Martin; Bubnov, Alexej; Kašpar, Miroslav; Hampl, F.; Hamplová, Věra; Pacherová, Oliva; Svoboda, J.

    2016-01-01

    Roč. 4, č. 23 (2016), 5326-5333 ISSN 2050-7526 R&D Projects: GA ČR GA16-12150S; GA MŠk(CZ) LH15305 Institutional support: RVO:68378271 Keywords : liquid crystals * lateral substitution * azo group * isomerization Subject RIV: JJ - Other Materials Impact factor: 5.256, year: 2016

  10. Substituent effects in reduction-induced synthesis of ansa-titanocenes

    Czech Academy of Sciences Publication Activity Database

    Pinkas, Jiří; Císařová, I.; Gyepes, R.; Kubišta, Jiří; Mach, Karel; Horáček, Michal

    2016-01-01

    Roč. 41, č. 2 (2016), s. 143-152 ISSN 0340-4285 R&D Projects: GA ČR(CZ) GAP207/12/2368 Institutional support: RVO:61388955 Keywords : synthesis * ansa-titanocenes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.358, year: 2016

  11. Substituent Effects on the Coordination Chemistry of Metal-Binding Pharmacophores

    Energy Technology Data Exchange (ETDEWEB)

    Craig, Whitney R. [Department; Baker, Tessa W. [Department; Marts, Amy R. [Department; DeGenova, Daniel T. [Department; Martin, David P. [Department; Reed, Garrett C. [Department; McCarrick, Robert M. [Department; Crowder, Michael W. [Department; Cohen, Seth M. [Department; Tierney, David L. [Department

    2017-09-12

    A combination of XAS, UV–vis, NMR, and EPR was used to examine the binding of a series of α-hydroxythiones to CoCA. All three appear to bind preferentially in their neutral, protonated forms. Two of the three clearly bind in a monodentate fashion, through the thione sulfur alone. Thiomaltol (TM) appears to show some orientational preference, on the basis of the NMR, while it appears that thiopyromeconic acid (TPMA) retains rotational freedom. In contrast, allothiomaltol (ATM), after initially binding in its neutral form, presumably through the thione sulfur, forms a final complex that is five-coordinate via bidentate coordination of ATM. On the basis of optical titrations, we speculate that this may be due to the lower initial pKa of ATM (8.3) relative to those of TM (9.0) and TPMA (9.5). Binding through the thione is shown to reduce the hydroxyl pKa by ~0.7 pH unit on metal binding, bringing only ATM’s pKa close to the pH of the experiment, facilitating deprotonation and subsequent coordination of the hydroxyl. The data predict the presence of a solvent-exchangeable proton on TM and TPMA, and Q-band 2-pulse ESEEM experiments on CoCA + TM suggest that the proton is present. ESE-detected EPR also showed a surprising frequency dependence, giving only a subset of the expected resonances at X-band.

  12. Studies on organic semiconductors. 15: Effects of the substituents on the photoconductivities of substituted anthracenes

    Science.gov (United States)

    Sugimoto, A.; Kato, S.; Inoue, H.; Imoto, E.

    1985-01-01

    The photocurrents of the substituted anthracenes, 1,5-diacetylanthracene (2), 1-acetylanthracene (3), 9-acetylanthracene (4), 1,5-dichloroanthracene (5), 1,5-diethylanthracene (6), 1,5-dimethoxyanthracene (7), 9-cyanoanthracene (8), and anthracene (1) were measured by using their surface type cells in nitrogen. The compounds of (1), (5), (6), (7), and (8) showed the photocurrent spectra which corresponded to the absorption spectra of their evaporated films. In the cases of (2) and (3), however, the anomalous photocurrent appeared in the threshold region of their absorption spectra. The appearance of the anomalous photocurrent was characteristic of anthracenes having the acetyl group at 1- and/or 5-position. The magnitude of the photocurrents of the 1,5-disubstituted anthracenes was similar to that of (1). The photocurrents of the monosubstituted anthracenes were smaller than that of (1). Among the monosubstituted anthracenes, the compound (4) showed no photocurrent under the same conditions. Contrary to the results obtained in the cases of phenazines, the photoconductivities of the anthracene derivatives became better in air.

  13. Substituent effects on the H abstraction by recoil 38Cl in some organic systems

    International Nuclear Information System (INIS)

    Dedgaonkar, V.G.; Mitra, S.; Waghmare, Sunil

    1986-01-01

    Total organic yield following 37 Cl(n,γ) 38 Cl reaction in trichloro solids of acetanilides and anilines is in the range 46-49%. Yield for the dichloro systems is lower: 25%. In general, the organic yields are in the order Ar-OH > Ar-NH 2 > Ar-NHCOCH 3 . Solution state irradiation in various solvents further lower the yield (about 28%) which remains independent of the polarity of the solvents. (author)

  14. Permanganate oxidation of alkenes. Substituent and solvent effects. Difficulties with MP2 calculations

    Czech Academy of Sciences Publication Activity Database

    Wiberg, K. B.; Wang, Y.; Sklenák, Štěpán; Deutsch, C.; Trucks, G.

    2006-01-01

    Roč. 128, č. 35 (2006), s. 11537-11544 ISSN 0002-7863 Grant - others:National Science Foundation Grant(US) CHE-0445847 Institutional research plan: CEZ:AV0Z40400503 Keywords : density-functional theory * polarizable continuum model * fumaric acids Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.696, year: 2006

  15. Basicity of carboxylic acids: resonance in the cation and substituent effects

    Czech Academy of Sciences Publication Activity Database

    Böhm, S.; Exner, Otto

    2005-01-01

    Roč. 29, - (2005), s. 336-342 ISSN 1144-0546 R&D Projects: GA MŠk(CZ) LN00A032 Institutional research plan: CEZ:AV0Z4055905 Keywords : basicity * carboxylic acids Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.574, year: 2005

  16. The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

    Directory of Open Access Journals (Sweden)

    Volodymyr V. Tkachenko

    2014-12-01

    Full Text Available The switchable three-component reactions of 5-amino-3-methylisoxazole, salicylaldehyde and N-aryl-3-oxobutanamides under different conditions were studied and discussed. The unexpected influence of the aryl substituent in N-aryl-3-oxobutanamides on the behavior of the reaction was discovered. The key influence of ultrasonication and Lewis acid catalysts led to an established protocol to selectively obtain two or three types of heterocyclic scaffolds depending on the substituent in the N-aryl moiety.

  17. Preparation of Different Substitued Polypyridine Ligands, Ruthenium(II)-Bridged Complexes and Spectoscopıc Studies.

    Science.gov (United States)

    Obali, Aslihan Yilmaz; Ucan, Halil Ismet

    2016-09-01

    Novel different substitued polypyridine ligands 4-((4-(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)phenoxy)methyl)benzaldehyde (BA-PPY), (E)-N-(4-((4-(1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)phenoxy)methyl)benzylidene)-pyrene-4-amine (PR-PPY), (E)-N-(4-((4-(1H-imidazo[4,5-f][1,10] phenanthroline-2-yl)phenoxy)methyl)benzylidene)-1,10-phenanthroline-5amine (FN-PPY), 2-(4-(bromomethyl)phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (BR-PPY), 2-(4-(azidomethyl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (N3-PPY) and triazole containing polypyridine ligand 3,4-bis[(4-(metoxy)-1,2,3-triazole)1-methylphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline)] benzaldehyde (BA-DIPPY) and Ruthenium(II) complexes were synthesized and characterized. Their photopysical properties were investigated. The complexes RuP(PR-PPY), RuB(PR-PPY, RuP(FN-PPY) and RuB(FN-PPY) exhibited a broad absorption bands at 485, 475, 476, and 453 nm, respectively, assignable to the spin-allowed MLCT (dπ-π*) transition. The emission maxima of the pyrene-appended polypyridine ligand PR-PPY was observed at λems = 616 nm and the phenanthroline-appended polypyridine ligand FN-PPY was observed at λems = 668 nm. And the emission maxima of the complexes RuP(PR-PPY), RuB(PR-PPY), RuP(FN-PPY) and RuB(FN-PPY) were observed at λems = 646, 646, 685 and 685 nm, respectively. As seen in fluorescence spectra, the fluorescence intensities of the ligands are higher than their metal complexes. This is because of quenching effect of Ruthenium(II) metal on chromophore groups.

  18. Influence of Halogen Substituents on the Catalytic Oxidation of 2,4,6-Halogenated Phenols by Fe(III-Tetrakis(p-hydroxyphenyl porphyrins and Potassium Monopersulfate

    Directory of Open Access Journals (Sweden)

    Seiya Nagao

    2011-12-01

    Full Text Available The influence of halogen substituents on the catalytic oxidation of 2,4,6-trihalogenated phenols (TrXPs by iron(III-porphyrin/KHSO5 catalytic systems was investigated. Iron(III-5,10,15,20-tetrakis(p-hydroxyphenylporphyrin (FeTHP and its supported variants were employed, where the supported catalysts were synthesized by introducing FeTHP into hydroquinone-derived humic acids via formaldehyde poly-condensation. F (TrFP, Cl (TrCP, Br (TrBP and I (TrIP were examined as halogen substituents for TrXPs. Although the supported catalysts significantly enhanced the degradation and dehalogenation of TrFP and TrCP, the oxidation of TrBP and TrIP was not enhanced, compared to the FeTHP catalytic system. These results indicate that the degree of oxidation of TrXPs is strongly dependent on the types of halogen substituent. The order of dehalogenation levels for halogen substituents in TrXPs was F > Cl > Br > I, consistent with their order of electronegativity. The electronegativity of a halogen substituent affects the nucleophilicity of the carbon to which it is attached. The levels of oxidation products in the reaction mixtures were analyzed by GC/MS after extraction with n-hexane. The most abundant dimer product from TrFP via 2,6-difluoroquinone is consistent with a scenario where TrXP, with a more electronegative halogen substituent, is readily oxidized, while less electronegative halogen substituents are oxidized less readily by iron(III-porphyrin/KHSO5 catalytic systems.

  19. Phenyl hepta cyclopentyl – polyhedral oligomeric silsesquioxane (ph,hcp-POSS/Polystyrene (PS nanocomposites: the influence of substituents in the phenyl group on the thermal stability

    Directory of Open Access Journals (Sweden)

    I. Blanco

    2012-12-01

    Full Text Available Some new Polystyrene (PS nanocomposites were prepared by using two Polyhedral Oligomeric Silsesquioxanes (POSSs, namely RR’7(SiO1.58 (where R = 4-methoxyphenyl or 2,4-difluorophenyl and R’ = cyclopentyl, as fillers, and their degradation was studied to investigate the effect of the electron-donor or electron-withdrawing character of the phenyl group substituents on thermal stability. Nanocomposites were synthesized by in situ polymerization of styrene in the presence of various concentrations of POSS. Proton nuclear magnetic resonance (1H NMR spectra indicated that the POSS content in the obtained nanocomposites was higher than that in reactant mixtures. Inherent viscosity (ηinh and glass transition temperature (Tg determinations indicated that the average molar mass of polymer in 4-methoxynanocomposites was the same than neat PS, while it was much lower in 2,4-difluoro derivatives. Degradations were carried out in both flowing nitrogen and static air atmospheres, in the scanning mode, at various heating rates, and temperature at 5% mass loss (T5% and the activation energy (Ea of degradation of various nanocomposites were determined. The values obtained for 4-methoxyderivatives were higher than unfilled PS thus indicating higher thermal stability. Conversely, the values found for 2,4-difluoro derivatives were lower, in some cases even than those of neat PS. The results were discussed and interpreted.

  20. Diels-Alder Reactions in Water. Effects of Hydrophobicity and Hydrogen Bonding

    NARCIS (Netherlands)

    Otto, Sijbren; Blokzijl, Wilfried; Engberts, Jan B.F.N.

    1994-01-01

    In order to check whether the activated complex for the Diels-Alder reactions of 5-substituted 1,4-naphthoquinones with cyclopentadiene is more polar in water than in other solvents, we have determined the substituent effects in seven different solvents. The substituent effects gradually decrease

  1. Relative substituent orientation in the structure of cis-3-chloro-1,3-dimethyl-N-(4-nitrophenyl-2-oxocyclopentane-1-carboxamide

    Directory of Open Access Journals (Sweden)

    Matthias Zeller

    2014-09-01

    Full Text Available The structure of the title compound, C14H15ClN2O4, prepared by reaction of a methacryloyl dimer with nitroaniline, was determined to establish the relative substituent orientation on the cyclopentanone ring. In agreement with an earlier proposed reaction mechanism, the amide group and the methyl group adjacent to the chloro substituent adopt equatorial positions and relative cis orientation, whereas the Cl substituent itself and the methyl group adjacent to the amide have axial orientations relative to the mean plane of the five-membered ring. The conformation of the molecule is stabilized by one classical N—H...O (2.18 Å and one non-classical C—H...O (2.23 Å hydrogen bond, each possessing an S(6 graph-set motif. The crystal packing is defined by several non-classical intramolecular hydrogen bonds, as well as by partial stacking of the aromatic rings.

  2. Indolylarylsulfones as HIV-1 non-nucleoside reverse transcriptase inhibitors: new cyclic substituents at indole-2-carboxamide.

    Science.gov (United States)

    La Regina, Giuseppe; Coluccia, Antonio; Brancale, Andrea; Piscitelli, Francesco; Gatti, Valerio; Maga, Giovanni; Samuele, Alberta; Pannecouque, Christophe; Schols, Dominique; Balzarini, Jan; Novellino, Ettore; Silvestri, Romano

    2011-03-24

    New indolylarylsulfone derivatives bearing cyclic substituents at indole-2-carboxamide linked through a methylene/ethylene spacer were potent inhibitors of the WT HIV-1 replication in CEM and PBMC cells with inhibitory concentrations in the low nanomolar range. Against the mutant L100I and K103N RT HIV-1 strains in MT-4 cells, compounds 20, 24-26, 36, and 40 showed antiviral potency superior to that of NVP and EFV. Against these mutant strains, derivatives 20, 24-26, and 40 were equipotent to ETV. Molecular docking experiments on this novel series of IAS analogues have also suggested that the H-bond interaction between the nitrogen atom in the carboxamide chain of IAS and Glu138:B is important in the binding of these compounds. These results are in accordance with the experimental data obtained on the WT and on the mutant HIV-1 strains tested.

  3. Tuning and Quantifying Steric and Electronic Effects of N-Heterocyclic Carbenes

    KAUST Repository

    Falivene, Laura; Poater, Albert; Cavallo, Luigi

    2014-01-01

    This chapter states that the main handles for tuning steric and electronic effects are the substituents on N atoms, the nature of the C4-C5 bridge (either saturated or unsaturated), and the substituents on the C4 and C5 atoms. The initial intuition

  4. Acylated 2-(N-arylaminomethylene)benzo[b]thiophene-3(2H)-Ones: Molecular Switches with Varying Migrants and Substituents

    International Nuclear Information System (INIS)

    Dubonosov, A.D.; Rybalkin, V.P.; Tsukanov, A.V.; Minkin, V.I.; Popova, L.L.; Revinsky, Y.V.; Bren, V.A.; Minkin, V.I.

    2009-01-01

    Synthesis and properties of photo chromic acylated 2-(N-arylaminomethylene)benzo[b]thiophene-3(2H)-ones are described. Their structure largely depends on the nature of acyl migrant and in a less degree on N-aryl substituent.

  5. Dark and Photoinduced Cytotoxic Activity of the New Chlorophyll-a Derivatives with Oligoethylene Glycol Substituents on the Periphery of Their Macrocycles.

    Science.gov (United States)

    Pylina, Yana I; Shadrin, Dmitry M; Shevchenko, Oksana G; Startseva, Olga M; Velegzhaninov, Igor O; Belykh, Dmitry V; Velegzhaninov, Ilya O

    2017-01-05

    In the present work, we investigated the dark and photoinduced cytotoxic activity of the new chlorophyll-a derivatives which contain the substituents of oligoethylene glycol on the periphery of their macrocycles. These compounds were tested using human cell lines to estimate their potential as photosensitizers for photodynamic therapy of cancer. It was shown that all the tested compounds have expressed photoinduced cytotoxic activity in vitro. Detailed study of the biological activity of one of the most perspective compound in this series-pyropheophorbide-a 17-diethylene glycol ester (Compound 21 ) was performed. This new compound is characterized by lower dark cytotoxicity and higher photoinduced cytotoxicity than previously described in a similar compound (DH-I-180-3) and clinically used Photolon TM . Using fluorescent microscopy, it was shown that Compound 21 quickly penetrates the cells. Analysis of caspase-3 activity indicated an apoptosis induction 40 min after exposure to red light (λ = 660 nm). The induction of DNA damages and apoptosis was shown using Comet assay. The results of expression analysis of the stress-response genes indicate an activation of the genes which control the cell cycle and detoxification of the free radicals after an exposure of HeLa cells to Compound 21 and to red light. High photodynamic activity of this compound and the ability to oxidize biomolecules was demonstrated on nuclear-free mice erythrocytes. In addition, it was shown that Compound 21 is effectively activated with low energy 700 nm light, which can penetrate deep into the tissue. Thus, Compound 21 is a prospective substance for development of the new drugs for photodynamic therapy of cancer.

  6. Dark and Photoinduced Cytotoxic Activity of the New Chlorophyll-a Derivatives with Oligoethylene Glycol Substituents on the Periphery of Their Macrocycles

    Directory of Open Access Journals (Sweden)

    Yana I. Pylina

    2017-01-01

    Full Text Available In the present work, we investigated the dark and photoinduced cytotoxic activity of the new chlorophyll-a derivatives which contain the substituents of oligoethylene glycol on the periphery of their macrocycles. These compounds were tested using human cell lines to estimate their potential as photosensitizers for photodynamic therapy of cancer. It was shown that all the tested compounds have expressed photoinduced cytotoxic activity in vitro. Detailed study of the biological activity of one of the most perspective compound in this series—pyropheophorbide-a 17-diethylene glycol ester (Compound 21 was performed. This new compound is characterized by lower dark cytotoxicity and higher photoinduced cytotoxicity than previously described in a similar compound (DH-I-180-3 and clinically used PhotolonTM. Using fluorescent microscopy, it was shown that Compound 21 quickly penetrates the cells. Analysis of caspase-3 activity indicated an apoptosis induction 40 min after exposure to red light (λ = 660 nm. The induction of DNA damages and apoptosis was shown using Comet assay. The results of expression analysis of the stress-response genes indicate an activation of the genes which control the cell cycle and detoxification of the free radicals after an exposure of HeLa cells to Compound 21 and to red light. High photodynamic activity of this compound and the ability to oxidize biomolecules was demonstrated on nuclear-free mice erythrocytes. In addition, it was shown that Compound 21 is effectively activated with low energy 700 nm light, which can penetrate deep into the tissue. Thus, Compound 21 is a prospective substance for development of the new drugs for photodynamic therapy of cancer.

  7. Ligand solvation effect on Dy3+ complexing with benzoic, p-, o-, m-aminobenzoic, 4-pyridinecarboxylic acids., and with pyridine and 4-aminopyridine in aqua and aqua-organic media

    International Nuclear Information System (INIS)

    Elistratova, Yu.G.; Mustafina, A.R.; Devyatov, F.V.; Sarvarova, N.N.

    1996-01-01

    Substituent effect on stability of Dy 3+ complexes with aminobenzoic acids (o , p-, m-isomers), pyridinecarboxylic acids and p-aminopyridine was estimated on the base of pH-metric and magnetooptic data. It was concluded that the more the efficiency of ligand's solvation the less the substituent effects the complex stability. 15 refs., 3 figs., 2 tabs

  8. A Successful Attempt to Obtain the Linear Dependence Between One-Photon and Two-Photon Spectral Properties and Hammett Parameters of Various Aromatic Substituents in New π-Extended Asymmetric Organic Chromophores.

    Science.gov (United States)

    Hu, Nvdan; Gong, Yulong; Wang, Xinchao; Lu, Yao; Peng, Guangyue; Yang, Long; Zhang, Shengtao; Luo, Ziping; Li, Hongru; Gao, Fang

    2015-11-01

    A series of new asymmetric chromophores containing aromatic substituents and possessing the excellent π-extension in space were prepared through multi-steps routes. One-photon and two-photon spectral properties of these new chromophores could be tuned by these substituents finely and simultaneously. The linear correlation of the wave numbers of the one-photon absorption and emission maxima to Hammett parameters of these substituents was presented. Near infrared two-photon absorption emission integrated areas of the target chromophores were correlated linearly to Hammett constants of these substituted groups.

  9. Influence of fluorine substituents on the NMR properties of phenylboronic acids.

    Science.gov (United States)

    Gierczyk, Błażej; Kaźmierczak, Marcin; Popenda, Łukasz; Sporzyński, Andrzej; Schroeder, Grzegorz; Jurga, Stefan

    2014-05-01

    The paper presents results of a systematic NMR studies on fluorinated phenylboronic acids. All possible derivatives were studied. The experimental (1)H, (13)C, (19)F, (11)B, and (17)O spectral data were compared with the results of theoretical calculations. The relation between the calculated natural bond orbital parameters and spectral data (chemical shifts and coupling constants) is discussed. The first examples of (10)B/(11)B isotopic effect on the (19)F spectra and (4)JFO scalar coupling in organic compounds are reported. Copyright © 2014 John Wiley & Sons, Ltd.

  10. Synthesis of some fenchyl-substituted alkenes and enol-ethers containing 3-oxyphenyl substituents by the Barton-Kellogg reaction

    International Nuclear Information System (INIS)

    Ciscato, Luiz Francisco M.L.; Bartoloni, Fernando H.; Baader, Wilhelm Josef; Bastos, Erick L.; Guenther, Wolfgang; Weiss, Dieter; Beckert, Rainer

    2010-01-01

    The synthesis of one fenchyl-substituted alkene and two enol-ethers, containing 3-oxyphenyl substituents by the Barton-Kellogg reaction is described. The tri-substituted aromatic fenchylalkene 1a was prepared in 53% yield from thiofenchone and a diazoanisole; whereas enol-ethers 1b and 1c were obtained (95 and 75% yield, respectively) using an inverse approach based on diazofenchone and aromatic thionoesters. A mixture of Z and E isomers was obtained in all cases; isomer attribution and quantification has been carried out by analysis of NMR spectroscopic data assisted by theoretical calculations (E/Z ratio: 1a = 0.72, 1b = 2.2, 1c = 1.8). Reaction proceeds with low stereoselectivity leading to the preferential formation of diastereoisomeric olefins and enol-ethers where the aromatic substituent resides at the side of the two fenchyl methyl groups. (author)

  11. Synthesis of some fenchyl-substituted alkenes and enol-ethers containing 3-oxyphenyl substituents by the Barton-Kellogg reaction

    Energy Technology Data Exchange (ETDEWEB)

    Ciscato, Luiz Francisco M.L.; Bartoloni, Fernando H.; Baader, Wilhelm Josef, E-mail: wjbaader@iq.usp.b [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Quimica. Dept. de Quimica Fundamental; Bastos, Erick L. [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas; Guenther, Wolfgang; Weiss, Dieter; Beckert, Rainer [Friedrich-Schiller Universitaet Jena (Germany). Institut fuer Organische Chemie und Makromolekulare Chemie

    2010-07-01

    The synthesis of one fenchyl-substituted alkene and two enol-ethers, containing 3-oxyphenyl substituents by the Barton-Kellogg reaction is described. The tri-substituted aromatic fenchylalkene 1a was prepared in 53% yield from thiofenchone and a diazoanisole; whereas enol-ethers 1b and 1c were obtained (95 and 75% yield, respectively) using an inverse approach based on diazofenchone and aromatic thionoesters. A mixture of Z and E isomers was obtained in all cases; isomer attribution and quantification has been carried out by analysis of NMR spectroscopic data assisted by theoretical calculations (E/Z ratio: 1a = 0.72, 1b = 2.2, 1c = 1.8). Reaction proceeds with low stereoselectivity leading to the preferential formation of diastereoisomeric olefins and enol-ethers where the aromatic substituent resides at the side of the two fenchyl methyl groups. (author)

  12. The influence of serum substituents on serum-free Vero cell conditioned culture media manufactured from Dulbecco's modified Eagle medium in mouse embryo culture.

    Science.gov (United States)

    Lee, Jong-Seon; Kim, Ju-Hwan; Seo, Young-Seok; Yang, Jung-Bo; Kim, Yong-Il; Kim, Hye-Jin; Lee, Ki-Hwan

    2013-09-01

    This study was conducted to examine the influences of supplementation of the serum substituents and available period of serum-free Vero cell conditioned media (SF-VCM) manufactured from Dulbecco's modified Eagle medium cultured with Vero cells for in vitro development of mouse preimplantation embryos. A total of 1,099 two-cell embryos collected from imprinting control region mice were cultured in SF-VCM with 10% and 20% human follicular fluid (hFF), serum substitute supplement (SSS), and serum protein substitute (SPS). Development of embryos was observed every 24 hours. Results between different groups were analyzed by chi-square test, and considered statistically significant when P-value was less than 0.05. The rates of embryonic development cultured in SF-VCM supplemented with serum substituents were significantly higher compare with serum-free group (P media up to 4 weeks did not affect on embryonic development.

  13. The hydrophobic substituent in aminophospholipids affects the formation kinetics of their Schiff bases.

    Science.gov (United States)

    Caldés, Catalina; Vilanova, Bartolomé; Adrover, Miquel; Donoso, Josefa; Muñoz, Francisco

    2013-04-01

    Schiff bases (SBs) are the initial products of non-enzymatic glycation reactions, which are associated to some diabetes-related diseases. In this work, we used physiological pH and temperature conditions to study the formation kinetics of the SBs of 1,2-dihexanoyl-sn-glycero-3-phosphoethanolamine (DPHE) and 1,2-dihexanoyl-sn-glycero-3-phospho-l-serine (DHPS) with various glycating compounds and with pyridoxal 5'-phosphate (an effective glycation inhibitor). Based on the obtained results, the hydrophobic environment simultaneously decreases the nucleophilic character of the amino group (k1) and increases its pKa, thereby increasing the formation rate of SB (kobs). Therefore, the presence of hydrophobic chains in aminophospholipids facilitates the formation and stabilization of SBs, and also, in a biological environment, their glycation. Additionally, the results confirm the inhibitory action of B6 vitamers on aminophospholipid glycation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Substituent and environment influence on analytical properties of associates of xanthene dyes with polyhexamethyleneguanidine chloride

    Directory of Open Access Journals (Sweden)

    Tatiana S. Chmilenko

    2014-03-01

    Full Text Available The interaction of 5 anionic xanthene dyes – 9-R-2,3,7-trihydroxy-6-fluorones (ТОF with cationic polyelectrolyte (PE – polyhexamethyleneguanidine chloride (PHMG has been studied by the optical spectroscopy in a concentration range where PHMG has a polyelectrolyte effect. Hammet σ-constants were calculated. The correlations between structure of ТОF and shift of protolytic equilibrium in aqueous-polyelectrolyte solutions were established. Influence of рН, concentration of the ethanol, components ratio in the system PHMG-TOF on the character of the interaction of cationic PE with ТОF and value of the analytical signal were studied based on absorption spectra. The results were compared to those obtained in water solutions. 

  15. Superoxide radical-mediated photocatalytic oxidation of phenolic compounds over Ag{sup +}/TiO{sub 2}: Influence of electron donating and withdrawing substituents

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Jiadong [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xie, Yongbing, E-mail: ybxie@ipe.ac.cn [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Han, Qingzhen [State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Cao, Hongbin [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Wang, Yujiao [Department of Chemical and Biomedical Engineering, University of Science and Technology Beijing (China); Nawaz, Faheem; Duan, Feng [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2016-03-05

    Highlights: • A weak EWG benefited photocatalytic oxidation of phenols the most. • Phenolic compounds were dominantly oxidized by ·O{sub 2}{sup −}, rather than ·OH, {sup 1}O{sub 2} or h{sup +}. • ·O{sub 2}{sup −} preferred to nucleophilically attack EDG substituted phenols. • ·O{sub 2}{sup −} more likely electrophilically attacked EWG substituted phenols. • ·O{sub 2}{sup −} simultaneously nucleophilically and electrophilically assaulted p-chlorophenol. - Abstract: A comparative study was constructed to correlate the electronic property of the substituents with the degradation rates of phenolic compounds and their oxidation pathways under UV with Ag{sup +}/TiO{sub 2} suspensions. It was verified that a weak electron withdrawing substituent benefited photocatalytic oxidation the most, while an adverse impact appeared when a substituent was present with stronger electron donating or withdrawing ability. The addition of p-benzoquinone dramatically blocked the degradation, confirming superoxide radicals (·O{sub 2}{sup −}) as the dominant photooxidant, rather than hydroxyl radicals, singlet oxygen or positive holes, which was also independent of the substituent. Hammett relationship was established based on pseudo-first-order reaction kinetics, and it revealed two disparate reaction patterns between ·O{sub 2}{sup −} and phenolic compounds, which was further verified by the quantum chemical computation on the frontier molecular orbitals and Mulliken charge distributions of ·O{sub 2}{sup −} and phenolic compounds. It was found that electron donating group (EDG) substituted phenols were more likely nucleophilically attacked by ·O{sub 2}{sup −}, while ·O{sub 2}{sup −} preferred to electrophilically assault electron withdrawing group (EWG) substituted phenols. Exceptionally, electrophilic and nucleophilic attack by ·O{sub 2}{sup −} could simultaneously occur in p-chlorophenol degradation, consequently leading to its highest rate

  16. Superoxide radical-mediated photocatalytic oxidation of phenolic compounds over Ag"+/TiO_2: Influence of electron donating and withdrawing substituents

    International Nuclear Information System (INIS)

    Xiao, Jiadong; Xie, Yongbing; Han, Qingzhen; Cao, Hongbin; Wang, Yujiao; Nawaz, Faheem; Duan, Feng

    2016-01-01

    Highlights: • A weak EWG benefited photocatalytic oxidation of phenols the most. • Phenolic compounds were dominantly oxidized by ·O_2"−, rather than ·OH, "1O_2 or h"+. • ·O_2"− preferred to nucleophilically attack EDG substituted phenols. • ·O_2"− more likely electrophilically attacked EWG substituted phenols. • ·O_2"− simultaneously nucleophilically and electrophilically assaulted p-chlorophenol. - Abstract: A comparative study was constructed to correlate the electronic property of the substituents with the degradation rates of phenolic compounds and their oxidation pathways under UV with Ag"+/TiO_2 suspensions. It was verified that a weak electron withdrawing substituent benefited photocatalytic oxidation the most, while an adverse impact appeared when a substituent was present with stronger electron donating or withdrawing ability. The addition of p-benzoquinone dramatically blocked the degradation, confirming superoxide radicals (·O_2"−) as the dominant photooxidant, rather than hydroxyl radicals, singlet oxygen or positive holes, which was also independent of the substituent. Hammett relationship was established based on pseudo-first-order reaction kinetics, and it revealed two disparate reaction patterns between ·O_2"− and phenolic compounds, which was further verified by the quantum chemical computation on the frontier molecular orbitals and Mulliken charge distributions of ·O_2"− and phenolic compounds. It was found that electron donating group (EDG) substituted phenols were more likely nucleophilically attacked by ·O_2"−, while ·O_2"− preferred to electrophilically assault electron withdrawing group (EWG) substituted phenols. Exceptionally, electrophilic and nucleophilic attack by ·O_2"− could simultaneously occur in p-chlorophenol degradation, consequently leading to its highest rate constant. Possible reactive positions on the phenolic compounds were also detailedly uncovered.

  17. Dark and Photoinduced Cytotoxic Activity of the New Chlorophyll-a Derivatives with Oligoethylene Glycol Substituents on the Periphery of Their Macrocycles

    OpenAIRE

    Yana I. Pylina; Dmitry M. Shadrin; Oksana G. Shevchenko; Olga M. Startseva; Igor O. Velegzhaninov; Dmitry V. Belykh; Ilya O. Velegzhaninov

    2017-01-01

    In the present work, we investigated the dark and photoinduced cytotoxic activity of the new chlorophyll-a derivatives which contain the substituents of oligoethylene glycol on the periphery of their macrocycles. These compounds were tested using human cell lines to estimate their potential as photosensitizers for photodynamic therapy of cancer. It was shown that all the tested compounds have expressed photoinduced cytotoxic activity in vitro. Detailed study of the biological activity of one ...

  18. Structural, magnetic and electrical properties of Zr-substitued NiZnCo ferrite nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Li, Le-Zhong, E-mail: lezhongli@cuit.edu.cn; Zhong, Xiao-Xi; Wang, Rui; Tu, Xiao-Qiang

    2017-08-01

    Highlights: • The static magnetic properties of NiZnCoZr ferrite nanopowders have been investigated. • The dielectric constant increases with the increase of Zr substitution. • The relaxation peak of tan δ ∼ T curves is observed for x ≥ 0.10. • Electrical transport behavior is found to follow the impurity semiconductor. • The dc resistivity increases at transition temperature with Zr substitution. - Abstract: Zr-substituted NiZnCo ferrite nanopowders, Ni{sub 0.4−x}Zn{sub 0.5}Zr{sub x}Co{sub 0.1}Fe{sub 2.0}O{sub 4} (0 ≤ x ≤ 0.20), were synthesized by the sol-gel auto-combustion method. The effects of Zr substitution on the structural, magnetic and electrical properties have been investigated. The DTA and TG results indicate that there are three steps of combustion process. The X-ray diffraction patterns show that the lattice parameter and the average crystallite size increase with the increase of Zr substitution. The saturation magnetization increases with the increase of Zr substitution when x ≤ 0.05, and then decreases when x > 0.05. Meanwhile, the coercivity initially decreases with the increase of Zr substitution when x ≤ 0.05, and then increases when x > 0.05. The polarization behavior for all the samples in the test frequency range from100 Hz to10 MHz obeys the charge polarization mechanism, which happens since the frequency of the hopping of electron exchange between Fe{sup 2+} and Fe{sup 3+} ions are far from the frequency of alternating-current field. And the dielectric constant increases with the increase of Zr substitution. The relaxation peak of the frequency dependence of dielectric loss is observed for x ≥ 0.10, which is due to the frequency of charge hopping between the Fe{sup 2+} and Fe{sup 3+} exactly matches with the frequency of the external applied field. Electrical transport behavior of the ferrite nanopowders is found to follow the impurity semiconductor, and the effect of Zr substitution on the temperature dependence

  19. Synthesis, photophysical and photochemical properties of zinc phthalocyanines bearing fluoro-functionalized substituents

    Energy Technology Data Exchange (ETDEWEB)

    Aktaş, Ayşe [Department of Chemistry, Faculty of Sciences, Karadeniz Technical University, 61080 Trabzon (Turkey); Pişkin, Mehmet [Marmara University, Faculty of Art and Science, Department of Chemistry, 34722 Kadikoy-Istanbul (Turkey); Durmuş, Mahmut [Gebze Institute of Technology, Department of Chemistry, PO Box 141, Gebze 41400, Kocaeli (Turkey); Bıyıklıoğlu, Zekeriya, E-mail: zekeriya_61@yahoo.com [Department of Chemistry, Faculty of Sciences, Karadeniz Technical University, 61080 Trabzon (Turkey)

    2014-01-15

    In this study, the synthesis of phthalonitrile derivatives bearing fluoro-functionalized groups and their peripherally-tetra substituted zinc phthalocyanine complexes were reported. The phthalonitrile derivatives 2a–5a were prepared by nucleophilic substitution of 4-nitrophthalonitrile with 2-[3-(trifluoromethyl)phenoxy]ethanol, 2-{2-[3-(trifluoromethyl) phenoxy]ethoxy}ethanol, 2-(2,3,5,6-tetrafluorophenoxy)ethanol, 2-[2-(2,3,5,6-tetrafluorophenoxy)ethoxy]ethanol, respectively. Zinc phthalocyanines bearing fluoro-functionalized groups (2b–5b) were obtained from the corresponding phthalonitrile derivatives. The newly synthesized phthalocyanines displayed good solubility in organic solvents such as chloroform (CHCl{sub 3}), dichloromethane (DCM), tetrahydrofuran (THF), toluene, dimethylformamide (DMF) and dimethylsulfoxide (DMSO). On the other hand, the singlet oxygen, photodegradation, fluorescence quantum yields and fluorescence lifetime of these complexes were determined in DMSO. The effects of the substitution with fluoro-functionalized groups on these parameters were also compared. -- Highlights: • Synthesis of peripherally substituted zinc phthalocyanines. • Photophysical and photochemical properties in DMSO for phthalocyanines. • Photodynamic therapy studies.

  20. Synthesis, photophysical and photochemical properties of zinc phthalocyanines bearing fluoro-functionalized substituents

    International Nuclear Information System (INIS)

    Aktaş, Ayşe; Pişkin, Mehmet; Durmuş, Mahmut; Bıyıklıoğlu, Zekeriya

    2014-01-01

    In this study, the synthesis of phthalonitrile derivatives bearing fluoro-functionalized groups and their peripherally-tetra substituted zinc phthalocyanine complexes were reported. The phthalonitrile derivatives 2a–5a were prepared by nucleophilic substitution of 4-nitrophthalonitrile with 2-[3-(trifluoromethyl)phenoxy]ethanol, 2-{2-[3-(trifluoromethyl) phenoxy]ethoxy}ethanol, 2-(2,3,5,6-tetrafluorophenoxy)ethanol, 2-[2-(2,3,5,6-tetrafluorophenoxy)ethoxy]ethanol, respectively. Zinc phthalocyanines bearing fluoro-functionalized groups (2b–5b) were obtained from the corresponding phthalonitrile derivatives. The newly synthesized phthalocyanines displayed good solubility in organic solvents such as chloroform (CHCl 3 ), dichloromethane (DCM), tetrahydrofuran (THF), toluene, dimethylformamide (DMF) and dimethylsulfoxide (DMSO). On the other hand, the singlet oxygen, photodegradation, fluorescence quantum yields and fluorescence lifetime of these complexes were determined in DMSO. The effects of the substitution with fluoro-functionalized groups on these parameters were also compared. -- Highlights: • Synthesis of peripherally substituted zinc phthalocyanines. • Photophysical and photochemical properties in DMSO for phthalocyanines. • Photodynamic therapy studies

  1. First Spectroscopic Studies and Detection in SgrB2 of 13C-DOUBLY Substitued Ethyl Cyanide

    Science.gov (United States)

    Margulès, L.; Motiyenko, R. A.; Guillemin, J.-C.; Müller, Holger S. P.; Belloche, Arnaud

    2015-06-01

    Ethyl cyanide (CH_3CH_2CN) is one of the most abundant complex organic molecules in the interstellar medium firstly detected in OMC-1 and Sgr B2 in 1977. The vibrationally excited states are enough populated under ISM conditions and could be detected. Apart from the deuterated ones, all mono-substituted isotopologues of ethyl cyanide (13C and 15N have been detected in the ISM. The detection of isotopologues in the ISM is important: it can give information about the formation process of complex organic molecules, and it is essential to clean the ISM spectra from the lines of known molecules in order to detect new ones. The 12C/13C ratio found in SgrB2: 20-30 suggests that the doubly 13C could be present in the spectral line survey recently obtained with ALMA (EMoCA), but no spectroscopic studies exist up to now. We measured and analyzed the spectra of the 13C-doubly-substitued species up to 1 THz with the Lille solid-state based spectrometer. The spectroscopic results and and the detection of the doubly 13C species in SgrB2 will be presented. This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI. This work was also done under ANR-13-BS05-0008-02 IMOLABS. Support by the Deutsche Forschungsgemeinschaft via SFB 956, project B3 is acknowledged D.~R.~Johnson, et al., Astrophys.~J. 1977, 218, L370 A.~Belloche, et al., A&A 2013, 559, A47 A.M.~Daly, et al., Astrophys.~J. 2013, 768, 81 K.~Demyk, et al. A&A 2007 466, 255 Margulès, et al. A&A 2009, 493, 565 Belloche et al. 2014, Science, 345, 1584

  2. Synthesis and characterization of new fluorescent styrene-containing carborane derivatives: the singular quenching role of a phenyl substituent.

    Science.gov (United States)

    Ferrer-Ugalde, Albert; Juárez-Pérez, Emilio José; Teixidor, Francesc; Viñas, Clara; Sillanpää, Reijo; Pérez-Inestrosa, Ezequiel; Núñez, Rosario

    2012-01-09

    A set of neutral and anionic carborane derivatives in which the styrenyl fragment is introduced as a fluorophore group has been successfully synthesized and characterized. The reaction of the monolithium salts of 1-Ph-1,2-C(2)B(10)H(11), 1-Me-1,2-C(2)B(10)H(11) and 1,2-C(2)B(10)H(12) with one equivalent of 4-vinylbenzyl chloride leads to the formation of compounds 1-3, whereas the reaction of the dilithium salt of 1,2-C(2)B(10)H(12) with two equivalents of 4-vinylbenzyl chloride gives disubstituted compound 4. The closo clusters were degraded using the classical method, KOH in EtOH, to afford the corresponding nido species, which were isolated as tetramethylammonium salts. The crystal structure of the four closo compounds 1-4 were analyzed by X-ray diffraction. All compounds, except 1, display emission properties, with quantum yields dependent on the nature of the cluster (closo or nido) and the substituent on the second C(cluster) atom. In general, closo compounds 2-4 exhibit high fluorescence emission, whereas the presence of a nido cluster produces a decrease of the emission intensity. The presence of a phenyl group bonded to the C(cluster) results in an excellent electron-acceptor unit that produces a quenching of the fluorescence. DFT calculations have confirmed the charge-separation state in 1 to explain the quenching of the fluorescence and the key role of the carboranyl fragment in this luminescent process. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Enantioselective copper catalysed intramolecular C-H insertion reactions of α-diazo-β-keto sulfones, α-diazo-β-keto phosphine oxides and 2-diazo-1,3-diketones; the influence of the carbene substituent.

    Science.gov (United States)

    Shiely, Amy E; Slattery, Catherine N; Ford, Alan; Eccles, Kevin S; Lawrence, Simon E; Maguire, Anita R

    2017-03-22

    Enantioselectivities in C-H insertion reactions, employing the copper-bis(oxazoline)-NaBARF catalyst system, leading to cyclopentanones are highest with sulfonyl substituents on the carbene carbon, and furthermore, the impact is enhanced by increased steric demand on the sulfonyl substituent (up to 91%ee). Enantioselective intramolecular C-H insertion reactions of α-diazo-β-keto phosphine oxides and 2-diazo-1,3-diketones are reported for the first time.

  4. Going to extremes

    DEFF Research Database (Denmark)

    Jensen, Henrik Helligsø; Pedersen, Christian Marcus; Bols, Mikael

    2007-01-01

    This concept article gives an overview of stereoelectronic effects in monosaccharide systems and how these can be used to dramatically enhance the reactivity of glycosyl donors in oligosaccharide synthesis.......This concept article gives an overview of stereoelectronic effects in monosaccharide systems and how these can be used to dramatically enhance the reactivity of glycosyl donors in oligosaccharide synthesis....

  5. Reverse cope elimination of hydroxylamines and alkenes or alkynes: theoretical investigation of tether length and substituent effects.

    Science.gov (United States)

    Krenske, Elizabeth H; Davison, Edwin C; Forbes, Ian T; Warner, Jacqueline A; Smith, Adrian L; Holmes, Andrew B; Houk, K N

    2012-02-01

    Quantum mechanical calculations have been used to study the intramolecular additions of hydroxylamines to alkenes and alkynes ("reverse Cope eliminations"). In intermolecular reverse Cope eliminations, alkynes are more reactive than alkenes. However, competition experiments have shown that tethering the hydroxylamine to the alkene or alkyne can reverse the reactivity order from that normally observed. The exact outcome depends on the length of the tether. In agreement with experiment, a range of density functional theory methods and CBS-QB3 calculations predict that the activation energies for intramolecular reverse Cope eliminations follow the order 6-exo-dig hydroxylamine and alkyne. Cyclization onto an alkene in the 5-exo-trig fashion incurs slightly less tether strain than a 6-exo-dig alkyne cyclization, but its activation energy is higher because the hydroxylamine fragment must distort more before the TS is reached. If the alkene terminus is substituted with two methyl groups, the barrier becomes so much higher that it is also disfavored compared to the 5- and 7-exo-dig cyclizations. © 2012 American Chemical Society

  6. The Reverse Cope Elimination of Hydroxylamines and Alkenes or Alkynes: Theoretical Investigation of Tether Length and Substituent Effects

    Science.gov (United States)

    Krenske, Elizabeth H.; Davison, Edwin C.; Forbes, Ian T.; Warner, Jacqueline A.; Smith, Adrian L.; Holmes, Andrew B.; Houk, K. N.

    2012-01-01

    Quantum mechanical calculations have been used to study the intramolecular additions of hydroxylamines to alkenes and alkynes (“reverse Cope eliminations”). In intermolecular reverse Cope eliminations, alkynes are more reactive than alkenes. However, competition experiments have shown that tethering the hydroxylamine to the alkene or alkyne can reverse the reactivity order from that normally observed. The exact outcome depends on the length of the tether. In agreement with experiment, a range of density functional theory methods and CBS-QB3 calculations predict that the activation energies for intramolecular reverse Cope eliminations follow the order 6-exo-dig hydroxylamine and alkyne. Cyclization onto an alkene in the 5-exo-trig fashion incurs slightly less tether strain than a 6-exo-dig alkyne cyclization, but its activation energy is higher because the hydroxylamine fragment must distort more before the TS is reached. If the alkene terminus is substituted with two methyl groups, the barrier becomes so much higher that it is also disfavored compared to the 5- and 7-exo-dig cyclizations. PMID:22280245

  7. Mass Spectrometry in Organic Synthesis: Claisen-Schmidt Base-Catalyzed Condensation and Hammett Correlation of Substituent Effects

    Science.gov (United States)

    Bain, Ryan M.; Pulliam, Christopher J.; Yan, Xin; Moore, Kassandra F.; Mu¨ller, Thomas; Cooks, R. Graham

    2014-01-01

    Undergraduate laboratories generally teach an understanding of chemical reactivity using bulk or semimicroscale experiments with product isolation and subsequent chemical and spectroscopic analysis. In this study students were exposed to mass spectrometry as a means of chemical synthesis as well as analysis. The ionization method used, paper…

  8. Interpretation of substituent effects on 13C and 15N NMR chemical shifts in 6-substituted purines

    Czech Academy of Sciences Publication Activity Database

    Standara, Stanislav; Bouzková, K.; Straka, Michal; Zacharová, Z.; Hocek, Michal; Marek, J.; Marek, R.

    2011-01-01

    Roč. 13, č. 35 (2011), s. 15854-15864 ISSN 1463-9076 R&D Projects: GA ČR GA203/09/2037 Grant - others:CEITEC(XE) CZ.1.05/1.1.00/02.0068; 7th European Community Framework (XE) 230955; GA MŠk(CZ) LC06030 Program:LC Institutional research plan: CEZ:AV0Z40550506 Keywords : purine * nuclear magnetic shielding * localized molecular orbitals * conformational dependence Subject RIV: CC - Organic Chemistry Impact factor: 3.573, year: 2011

  9. The anomalous substituent effect of the ethyl group in the 13 C NMR and IR data of some aliphatic nitriles

    International Nuclear Information System (INIS)

    Garcia, Janaina C.; Barbarini, Jose E.; Rittner, Roberto; Rocco, Silvana A.; Tormena, Claudio F.

    1999-01-01

    This work reports a full assignment of 13 C and 1 H chemical shifts for some aliphatic nitriles from acetonitrile to octanonitrile and the observed shieldings for the carbon cyano group are correlated with the ν CN and with the electronic and steric parameters

  10. Effects of methoxy and formyl substituents on the energetics and reactivity of α-naphthalenes: a calorimetric and computational study.

    Science.gov (United States)

    Silva, Ana L R; Freitas, Vera L S; Ribeiro da Silva, Maria D M C

    2014-07-01

    A combined experimental and computational study was developed to evaluate and understand the energetics and reactivity of formyl and methoxy α-naphthalene derivatives. Static bomb combustion calorimetry and the Calvet microcalorimetry were the experimental techniques used to determine the standard (p(o)=0.1 MPa) molar enthalpies of formation, in the liquid phase, ΔfHm(o)(l), and of vaporization, Δl(g)Hm(o), at T=298.15K, respectively, of the two liquid naphthalene derivatives. Those experimental values were used to derive the values of the experimental standard molar enthalpies of formation, in the gaseous phase, ΔfHm(o)(g), of 1-methoxynaphthalene, (-3.0 ± 3.1)kJmol(-1), and of 1-formylnaphthalene, (36.3 ± 4.1)kJ mol(-1). High-level quantum chemical calculations at the composite G3(MP2)//B3LYP level were performed to estimate the values of the ΔfHm(o)(g) of the two compounds studied resulting in values in very good agreement with experimental ones. Natural bond orbital (NBO) calculations were also performed to determine more about the structure and reactivity of this class of compounds. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Decreasing redox voltage of terephthalate-based electrode material for Li-ion battery using substituent effect

    Science.gov (United States)

    Lakraychi, A. E.; Dolhem, F.; Djedaïni-Pilard, F.; Thiam, A.; Frayret, C.; Becuwe, M.

    2017-08-01

    The preparation and assessment versus lithium of a functionalized terephthalate-based as a potential new negative electrode material for Li-ion battery is presented. Inspired from molecular modelling, a decrease in redox potential is achieved through the symmetrical adjunction of electron-donating fragments (-CH3) on the aromatic ring. While the electrochemical activity of this organic material was maximized when used as nanocomposite and without any binder, the potential is furthermore lowered by 110 mV upon functionalization, consistently with predicted value gained from DFT calculations.

  12. Ab initio computation of electron affinities of substituted benzalacetophenones (chalcones): a new approach to substituent effects in organic electrochemistry

    International Nuclear Information System (INIS)

    Hicks, Latorya D.; Fry, Albert J.; Kurzweil, Vanessa C.

    2004-01-01

    The electron affinities (EAs) of a training set of 29 monosubstituted benzalacetophenones (chalcones) were computed at the ab initio density functional B3LYP/6-31G * level of theory. The EAs and experimental reduction potentials of the training set are highly linearly correlated (correlation coefficient of 0.969 and standard deviation of 10.8 mV). An additional 72 di-, tri-, and tetrasubstituted chalcones were then synthesized. Their reduction potentials were predicted from computed EAs using the linear correlation derived from the training set. Agreement between the experimental and computed reduction potentials is remarkably good, with a standard deviation of less than 22 mV for this very large set of substances whose potentials extend over a range of almost 700 mV

  13. Substituent effects on mono-substituted and poly-substituted nitriles; Efeitos dos substituintes em nitrilas mono- e polissubstituidas

    Energy Technology Data Exchange (ETDEWEB)

    Sofia, Raquel C.R.; Carneiro, Paulo I.B.; Rittner, Roberto [Universidade Estadual de Campinas, SP (Brazil). Inst. de Quimica; Fabi, Marino T [Rhodia S.A., Sao Paulo, SP (Brazil)

    1992-12-31

    This work studies various mono substituted aliphatic nitriles, Y C H{sub 2} (Y=H, F, Cl, Br, I, OMe, S Me, SEt{sub 2}, Me and Ph), and some reference nitriles (Y=Et, n-Pr, n-Bu, n-Am, n-Hex and n-Hept) 12 refs., 3 tabs.

  14. Effect of Substituents on the Electronic Structure and Degradation Process in Carbazole Derivatives for Blue OLED Host Materials

    KAUST Repository

    Hong, Minki; Ravva, Mahesh Kumar; Winget, Paul; Bredas, Jean-Luc

    2016-01-01

    (OLEDs). The C-N bond dissociation energies, calculated at the density functional theory level, are found to depend strongly on the charge states of the parental molecules. In particular, the anionic C-N bond dissociations resulting in a carbazole anion

  15. The effect of substituents in the aromatic ring on carcinogenicity of N-nitrosomethylaniline in F344 rats.

    Science.gov (United States)

    Kroeger-Koepke, M B; Reuber, M D; Iype, P T; Lijinsky, W; Michejda, C J

    1983-01-01

    N-Nitroso-N-methylaniline (NMA) and N-nitroso-N-methyl-4-fluoroaniline (p-F-NMA), both non-mutagenic in Salmonella typhimurium and N-nitroso-N-methyl-4-nitroaniline (p-NO2-NMA), a potent mutagen, were tested for carcinogenicity in F344 rats. NMA was shown to induce a high level of tumors in the upper gastrointestinal tract, particularly in the esophagus. Male rats treated with NMA died with tumors at a slightly higher rate than females, although the final tumor yield was the same. Most of the rats treated with p-F-NMA also developed tumors of the esophagus, but they died less rapidly than the NMA treated rats, indicating that p-F-NMA is a slightly weaker carcinogen than NMA. The powerful, directly acting mutagen, p-NO2-NMA did not appear to induce tumors at all since its tumor spectrum was essentially identical to that of the untreated control rats. Thus, the carcinogenic activities of NMA and its substituted analogs do not appear to correlate with bacterial mutagenesis assays. Additionally, NMA, p-F-NMA and N-nitroso-N-methyl-4-bromoaniline, the last a strong mutagen in S. typhimurium, were shown not to induce sister chromatid exchanges in CHO cells and in a clone of a CHO:liver cell hybrid which had previously been shown to be sensitive to chemical agents which require metabolic activation.

  16. Effect of Substituents on the Electronic Structure and Degradation Process in Carbazole Derivatives for Blue OLED Host Materials

    KAUST Repository

    Hong, Minki

    2016-07-25

    We investigate the dissociation mechanism of the C-N bond between carbazole and dibenzothiophene in carbazole-dibenzothiophene (Cz-DBT) positional isomers, selected as representative systems for blue host materials in organic light-emitting diodes (OLEDs). The C-N bond dissociation energies, calculated at the density functional theory level, are found to depend strongly on the charge states of the parental molecules. In particular, the anionic C-N bond dissociations resulting in a carbazole anion can have low dissociation energies (∼1.6 eV) with respect to blue emission energy. These low values are attributed to the large electron affinity of the carbazole radical, a feature that importantly can be modulated via substitution. Substitution also impacts the energies of the first excited electronic states of the Cz-DBT molecules since these states have an intramolecular charge-transfer nature due to the spatially localized character of the frontier molecular orbitals within the carbazole moiety (for the HOMO) and the dibenzothiophene moiety (for the LUMO). The implications of these results must be considered when designing blue OLED hosts since these materials must combine chemical stability and high triplet energy. © 2016 American Chemical Society.

  17. Effects of HPMC substituent pattern on water up-take, polymer and drug release: An experimental and modelling study.

    Science.gov (United States)

    Caccavo, Diego; Lamberti, Gaetano; Barba, Anna Angela; Abrahmsén-Alami, Susanna; Viridén, Anna; Larsson, Anette

    2017-08-07

    The purpose of this study was to investigate the hydration behavior of two matrix formulations containing the cellulose derivative hydroxypropyl methylcellulose (HPMC). The two HPMC batches investigated had different substitution pattern along the backbone; the first one is referred to as heterogeneous and the second as homogenous. The release of both the drug molecule theophylline and the polymer was determined. Additionally, the water concentrations at different positions in the swollen gel layers were determined by Magnetic Resonance Imaging. The experimental data was compared to predicted values obtained by the extension of a mechanistic Fickian based model. The hydration of tablets containing the more homogenous HPMC batch showed a gradual water concentration gradient in the gel layer and could be well predicted. The hydration process for the more heterogeneous batch showed a very abrupt step change in the water concentration in the gel layer and could not be well predicted. Based on the comparison between the experimental and predicted data this study suggests, for the first time, that formulations with HPMC of different heterogeneities form gels in different ways. The homogeneous HPMC batch exhibits a water sorption behavior ascribable to a Ficḱs law for the diffusion process whereas the more heterogeneous HPMC batches does not. This conclusion is important in the future development of simulation models and in the understanding of drug release mechanism from hydrophilic matrices. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Temperature and pressure variations of d-d luminescence band maxima of bis(pyridylalkenolato)palladium(II) complexes with different ligand substituents: opposite-signed trends.

    Science.gov (United States)

    Poirier, Stéphanie; Czympiel, Lisa; Bélanger-Desmarais, Nicolas; Mathur, Sanjay; Reber, Christian

    2016-04-21

    Luminescence spectra of two d(8)-configured bis(pyridylalkenolato)palladium(ii) complexes, [Pd{PyCHC(C3F7)O}2] and [Pd{PyCHC(CH3)O}2], are presented at variable temperature and pressure. Bands are assigned as d-d transitions. The heptafluoropropyl and methyl substituents on the ligands have different steric demands, influencing luminescence spectra. Broad bands with maxima at approximately 12 700 cm(-1) (790 nm) for ligands with heptafluoropropyl substituents and 12,100 cm(-1) (830 nm) for ligands with methyl substituents and widths of approximately 2100 cm(-1) for both complexes are observed at 80 K. Quenching of the luminescence is observed as temperature increases. The maxima of [Pd{PyCHC(C3F7)O}2] show a shift of -0.9 ± 0.1 cm(-1) K(-1) due to broadening of the spectra to lower energy. The luminescence maxima of [Pd{PyCHC(CH3)O}2] shift in the opposite direction by +7.2 ± 0.7 cm(-1) K(-1). Shifts with different signs are also obtained from variable-pressure luminescence spectra, with values of +13 ± 2 cm(-1) kbar(-1) and -15 ± 7 cm(-1) kbar(-1) for [Pd{PyCHC(C3F7)O}2] and [Pd{PyCHC(CH3)O}2], respectively. The pressure-induced decrease is unusual and likely caused by intermolecular interactions involving the palladium(ii) center and a vinylic proton of a neighboring complex.

  19. Adducts of pyridine with 7,8-dicarbo-nido-undecahydrononaborane and its iodo and bromo substituents: a comparative study of their physicochemical properties

    International Nuclear Information System (INIS)

    Volkov, O.V.; Il'inchik, E.A.; Volkov, V.V.; Voronina, G.S.; Yur'eva, O.P.

    1997-01-01

    The synthesis of bromo- and iodo substituents 7,8-C 2 B 9 H 11 xRu is accomplished and their comparative study is carried out through the methods of NMR 11 B-, PMR-, IR- and UV-spectroscopy. It is established that by introduction of halogen into carborane polyhedron there takes place increase in the acceptor capability of the latter and in the result the adduct stabilization. At the same time the introduction of halogen atom leads to sharp decrease in the intensity of the adduct fluorescence in the crystal state

  20. Electronic optimization of heteroleptic Ru(II) bipyridine complexes by remote substituents: synthesis, characterization, and application to dye-sensitized solar cells.

    Science.gov (United States)

    Han, Won-Sik; Han, Jung-Kyu; Kim, Hyun-Young; Choi, Mi Jin; Kang, Yong-Soo; Pac, Chyongjin; Kang, Sang Ook

    2011-04-18

    We prepared a series of new heteroleptic ruthenium(II) complexes, Ru(NCS)(2)LL' (3a-3e), where L is 4,4'-di(hydroxycarbonyl)-2,2'-bipyridine and L' is 4,4'-di(p-X-phenyl)-2,2'-pyridine (X = CN (a), F (b), H (c), OMe (d), and NMe(2) (e)), in an attempt to explore the structure-activity relationships in their photophysical and electrochemical behavior and in their performance in dye-sensitized solar cells (DSSCs). When substituent X is changed from electron-donating NMe(2) to electron-withdrawing CN, the absorption and emission maxima reveal systematic bathochromic shifts. The redox potentials of these dyes are also significantly influenced by X. The electronic properties of the dyes were theoretically analyzed using density functional theory calculations; the results show good correlations with the experimental results. The solar-cell performance of DSSCs based on dye-grafted nanocrystalline TiO(2) using 3a-3e and standard N3 (bis[(4,4'-carboxy-2,2'-bipyridine)(thiocyanato)]ruthenium(II)) were compared, revealing substantial dependences on the dye structures, particularly on the remote substituent X. The 3d-based device showed the best performance: η = 8.30%, J(SC) = 16.0 mA·cm(-2), V(OC) = 717 mV, and ff = 0.72. These values are better than N3-based device.

  1. /sup 13/C-/sup 13/C spin-spin coupling in structural investigations. VII. Substitution effects and direct carbon-carbon constants of the triple bond in acetyline derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Krivdin, L.B.; Proidakov, A.G.; Bazhenov, B.N.; Zinchenko, S.V.; Kalabin, G.A.

    1989-01-10

    The effects of substitution on the direct /sup 13/C-/sup 13/C spin-spin coupling constants of the triple bond were studied in 100 derivatives of acetylene. It was established that these parameters exhibit increased sensitivity to the effect of substituents compared with other types of compounds. The main factor which determines their variation is the electronegativity of the substituting groups, and in individual cases the /pi/-electronic effects are appreciable. The effect of the substituents with an element of the silicon subgroup at the /alpha/ position simultaneously at the triple bond or substituent of the above-mentioned type and a halogen atom.

  2. (E)-3-(2-Alkyl-10H-phenothiazin-3-yl)-1-arylprop-2-en-1-ones: Preparative, IR, NMR and DFT study on their substituent-dependent reactivity in hydrazinolysis and sonication-assisted oxidation with copper(II)nitrate.

    Science.gov (United States)

    Găină, Luiza; Csámpai, Antal; Túrós, György; Lovász, Tamás; Zsoldos-Mády, Virág; Silberg, Ioan A; Sohár, Pál

    2006-12-07

    A series of novel 3(5)-aryl/ferrocenyl-5(3)-phenothiazinylpyrazoles and pyrazolines were obtained by substituent-dependent regioselective condensation of the corresponding (E)-3-(2-alkyl-10H-phenothiazin-3-yl)-1-aryl/ferrocenylprop-2-en-1-one with hydrazine or methylhydrazine in acetic acid. The different propensity of the primary formed beta-hydrazino adducts to undergo competitive retro-Mannich reaction was interpreted in terms of tautomerisation equilibrium constants calculated by DFT using a solvent model. The regioselectivity of the cyclisation reactions with methylhydrazine and the substituent-dependent redox properties of pyrazolines were also rationalized by comparative DFT calculations performed for simplified model molecules. On the effect of ultrasound-promoted oxidation with copper(II)nitrate phenothiazine-containing pyrazolines, enones and oxo-compounds were selectively transformed into sulfoxides. Only one sulfoxide enone was partially converted into an oxirane derivative. The structure of the novel products was determined by IR and NMR spectroscopy including COSY, HSQC, HMBC and DNOE measurements.

  3. Influence of polyether ring size and of the nature of substituents on the yields of paramagnetic centers in γ-irradiated mono- and dibenzosubstituted crown ethers at 77 K

    International Nuclear Information System (INIS)

    Nesterov, S.V.; Panov, O.Yu.

    1998-01-01

    Intermediates stabilized in γ-irradiated mono- and dibenzosubstituted crown ethers are studied by ESR spectroscopy at 77 K. PhO · radicals and radicals with H-atom abstraction from polyether ring are the main products at low temperature γ-radiolysis. The nature of radicals produced in radiolysis and the yield of radicals, G R , depend on macroring size and on the number of aromatic substituents. Negative deviation from additive rule in function of G R versus ε of substituents is an evidence of efficient transfer of adsorbed energy to the π-system of aromatic group. (author)

  4. Derivatives of 16alpha-hydroxy-dehydroepiandrosterone with an additional 7-oxo or 7-hydroxy substituent: synthesis and gas chromatography/mass spectrometry analysis.

    Science.gov (United States)

    Pouzar, Vladimír; Cerný, Ivan; Hill, Martin; Bicíková, Marie; Hampl, Richard

    2005-10-01

    Derivatives of 16alpha-hydroxy-dehydroepiandrosterone, which have an additional oxygen substituent at position 7 (oxo or hydroxy group), were synthesized. Firstly, 17,17-dimethoxyandrost-5-ene-3beta,16alpha-diyl diacetate was prepared and then oxidized with a complex of chromium(VI) oxide and 2,5-dimethylpyrazole to the respective 7-oxo derivative. This key intermediate was both deprotected or reduced by l-Selectride or sodium borohydride in the presence of cerium(III) chloride and then deprotected to give 7-oxo, 7alpha-hydroxy and 7beta-hydroxy derivatives of 16alpha-hydroxy-dehydroepiandrosterone. The target compounds were characterized by (1)H and (13)C NMR spectra and in the form of O-methyloxime-trimethylsilyl derivatives, by gas chromatography/mass spectrometry methods.

  5. 1-Deoxy-D-galactonojirimycins with dansyl capped N-substituents as β-galactosidase inhibitors and potential probes for GM1 gangliosidosis affected cell lines.

    Science.gov (United States)

    Fröhlich, Richard F G; Furneaux, Richard H; Mahuran, Don J; Saf, Robert; Stütz, Arnold E; Tropak, Michael B; Wicki, Jacqueline; Withers, Stephen G; Wrodnigg, Tanja M

    2011-09-06

    Two simple and reliably accessible intermediates, N-carboxypentyl- and N-aminohexyl-1-deoxy-D-galactonojirimycin were employed for the synthesis of a set of terminally N-dansyl substituted derivatives. Reaction of the terminal carboxylic acid of N-carboxypentyl-1-deoxy-D-galactonojirimycin with N-dansyl-1,6-diaminohexane provided the chain-extended fluorescent derivative. Employing bis(6-dansylaminohexyl)amine, the corresponding branched di-N-dansyl compound was obtained. Partially protected N-aminohexyl-1-deoxy-D-galactonojirimycin served as intermediate for two additional chain-extended fluorescent 1-deoxy-D-galactonojirimycin (1-DGJ) derivatives featuring terminal dansyl groups in the N-alkyl substituent. These new compounds are strong inhibitors of d-galactosidases and may serve as leads en route to pharmacological chaperones for GM1-gangliosidosis. Copyright © 2011. Published by Elsevier Ltd.

  6. Mechanistic studies on the phosphoramidite coupling reaction in oligonucleotide synthesis. I. Evidence for nudeophilic catalysis by tetrazole and rate variations with the phosphorus substituents

    DEFF Research Database (Denmark)

    Dahl, Bjarne H.; Nielsen, John; Dahl, Otto

    1987-01-01

    , and that dialkylammonium tetrazolide salts are inhibitors. These and other facts are evidence that the reactions are subjected to nucleophilic catalysis by tetrazole, in addition to acid catalysis. The rate variations with phosphorus substituents of 1a-h are NEt 2 > NRr12 > N(CH 2CH 2)O > NMePh, and OMe > OCH 2CH 2CN......Tetrazole catalyzed reactions of a series of phosphoramidites, 5′ -O- DMTdT-3′-O-P(OR 1)NRNR22 (1a-h), with 3′ O-SiBu tPh 2-6-N-benzoyl-dA (2a) in acetonitrite solution have been studied. It is found that the coupling rate depends very much on whether tetrazole is added before or after 2a...

  7. N(G)-Acyl-argininamides as NPY Y(1) receptor antagonists: Influence of structurally diverse acyl substituents on stability and affinity.

    Science.gov (United States)

    Weiss, Stefan; Keller, Max; Bernhardt, Günther; Buschauer, Armin; König, Burkhard

    2010-09-01

    N(G)-Acylated argininamides, covering a broad range of lipophilicity (calculated logD values: -1.8-12.5), were synthesized and investigated for NPY Y(1) receptor (Y(1)R) antagonism, Y(1)R affinity and stability in buffer (N(G)-deacylation, yielding BIBP 3226). Broad structural variation of substituents was tolerated. The K(i) (binding) and K(b) values (Y(1)R antagonism) varied from low nM to one-digit muM. Most of the compounds proved to be sufficiently stable at pH 7.4 over 90min to determine reliable pharmacological data in vitro. Exceptionally high instability was detected when a succinyl moiety was attached to the guanidine, probably, due to an intramolecular cleavage mechanism. Copyright 2010 Elsevier Ltd. All rights reserved.

  8. Structural studies of series HIV-1 nonnucleoside reverse transcriptase inhibitors 1-(2,6-difluorobenzyl)-2-(2,6-difluorophenyl)-benzimidazoles with different 4-substituents

    Science.gov (United States)

    Ziółkowska, Natasza E.; Michejda, Christopher J.; Bujacz, Grzegorz D.

    2010-03-01

    Over the past 10 years, several anti-viral drugs have become available to fight the HIV infection. Antiretroviral treatment reduces the mortality of AIDS. Nonnucleoside inhibitors of HIV-1 reverse transcriptase are specific and potentially nontoxic drugs against AIDS. The crystal structures of five nonnucleoside inhibitors of HIV-1 reverse transcriptase are presented here. The structural parameters, especially those describing the angular orientation of the π-electron systems and influencing biological activity, were determined for all of the investigated inhibitors. The chemical character and orientation of the substituent at C4 position of the benzimidazole moiety substantially influences the anti-viral activity. The structural data of the investigated inhibitors is a good basis for modeling enzyme-inhibitor interactions for structure-assisted drug design.

  9. Extraction of uranium(6), transuranium elements and europium by bidentate neutral phosphorus- and phosphorus-nitrogen-containing reagents with substituent in methylene bridge

    International Nuclear Information System (INIS)

    Kochetkova, N.E.; Kojro, O.Eh.; Nesterova, N.P.; Medved', T.Ya.; Chmutova, M.K.; Myasoedov, B.F.; Kabachnik, M.I.

    1986-01-01

    The influence of substituents in methylene bridge on solubility, extractivity and selectivity of bidentate neutral phosphorus- and phosphorus-nitrogen-containing reagents in the process of U(6), TUE, Eu extraction has been studied. It is ascertained that hydrogen substitution in the bridge of tetraphenylmethylenediphosphine dioxide (1) causes a decrease in the extractivity of reagent as to TPE, uranium (6) and europium. There is no visible regular relation between basicity and extractivity of substituted reagents. Hydrogen substitution in the bridge of diphenyl[diethylcarbamoylmethyl]phosphine oxide (2) causes a decrease in extractivity of the reagent as to TPE, uranium (6) and europium. In contrast to monodentate neutral reagents, when bidentate neutral reagents are used, sometimes no increase in the reagent extractivity with an increase in its basicity is observed. When fragments restricting the conformation mobility of bidentate reagent molecule are introduced in it (here substituents in methylene bridge), it may result in the violation of the regularity, since of all the factors affecting the reagent extractivity the spatial factor may become the prevailing one. On hydrogen substitution in the bridge of 1 separation factors of practically all (with few exceptions) studied pairs of elements increase. Hydrogen substitution in the bridge of 2 causes an increase in separation factor of U (6) /Am pair and it does not affect the separation factor of Am/Eu pair. Hydrogen substitution in the bridge of 1 and 2 does not result in the preparation of more efficient and considerably more selective reagents for extractive isolation and separation of the elements, but some of the substituted reagents (Cl-substituted 1, for instance) may turn out useful for the element separation

  10. A new cationic porphyrin derivative (TMPipEOPP with large side arm substituents: a highly selective G-quadruplex optical probe.

    Directory of Open Access Journals (Sweden)

    Li-Na Zhu

    Full Text Available The discovery of uncommon DNA structures and speculation about their potential functions in genes has brought attention to specific DNA structure recognition. G-quadruplexes are four-stranded nucleic acid structures formed by G-rich DNA (or RNA sequences. G-rich sequences with a high potential to form G-quadruplexes have been found in many important genomic regions. Porphyrin derivatives with cationic side arm substituents are important G-quadruplex-binding ligands. For example, 5,10,15,20-Tetrakis(N-methylpyridinium-4-yl-21H,23H-porphyrin (TMPyP4, interacts strongly with G-quadruplexes, but has poor selectivity for G-quadruplex versus duplex DNA. To increase the G-quadruplex recognition specificity, a new cationic porphyrin derivative, 5,10,15,20-tetra-{4-[2-(1-methyl-1-piperidinylethoxy]phenyl} porphyrin (TMPipEOPP, with large side arm substituents was synthesized, and the interactions between TMPipEOPP and different DNA structures were compared. The results show that G-quadruplexes cause large changes in the UV-Vis absorption and fluorescence spectra of TMPipEOPP, but duplex and single-stranded DNAs do not, indicating that TMPipEOPP can be developed as a highly specific optical probe for discriminating G-quadruplex from duplex and single-stranded DNA. Visual discrimination is also possible. Job plot and Scatchard analysis suggest that a complicated binding interaction occurs between TMPipEOPP and G-quadruplexes. At a low [G-quadruplex]/[TMPipEOPP] ratio, one G-quadruplex binds two TMPipEOPP molecules by end-stacking and outside binding modes. At a high [G-quadruplex]/[TMPipEOPP] ratio, two G-quadruplexes bind to one TMPipEOPP molecule in a sandwich-like end-stacking mode.

  11. A new cationic porphyrin derivative (TMPipEOPP) with large side arm substituents: a highly selective G-quadruplex optical probe.

    Science.gov (United States)

    Zhu, Li-Na; Zhao, Shu-Juan; Wu, Bin; Li, Xiao-Zeng; Kong, De-Ming

    2012-01-01

    The discovery of uncommon DNA structures and speculation about their potential functions in genes has brought attention to specific DNA structure recognition. G-quadruplexes are four-stranded nucleic acid structures formed by G-rich DNA (or RNA) sequences. G-rich sequences with a high potential to form G-quadruplexes have been found in many important genomic regions. Porphyrin derivatives with cationic side arm substituents are important G-quadruplex-binding ligands. For example, 5,10,15,20-Tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphyrin (TMPyP4), interacts strongly with G-quadruplexes, but has poor selectivity for G-quadruplex versus duplex DNA. To increase the G-quadruplex recognition specificity, a new cationic porphyrin derivative, 5,10,15,20-tetra-{4-[2-(1-methyl-1-piperidinyl)ethoxy]phenyl} porphyrin (TMPipEOPP), with large side arm substituents was synthesized, and the interactions between TMPipEOPP and different DNA structures were compared. The results show that G-quadruplexes cause large changes in the UV-Vis absorption and fluorescence spectra of TMPipEOPP, but duplex and single-stranded DNAs do not, indicating that TMPipEOPP can be developed as a highly specific optical probe for discriminating G-quadruplex from duplex and single-stranded DNA. Visual discrimination is also possible. Job plot and Scatchard analysis suggest that a complicated binding interaction occurs between TMPipEOPP and G-quadruplexes. At a low [G-quadruplex]/[TMPipEOPP] ratio, one G-quadruplex binds two TMPipEOPP molecules by end-stacking and outside binding modes. At a high [G-quadruplex]/[TMPipEOPP] ratio, two G-quadruplexes bind to one TMPipEOPP molecule in a sandwich-like end-stacking mode.

  12. EFFECTS OF PCB 84 ATROPISOMERS ON [3H]-PHORBOL ESTER BINDING IN RAT CEREBELLAR GRANULE CELLS AND 45CA2+-UPTAKE IN RAT CEREBELLUM.

    Science.gov (United States)

    There is evidence that Polychlorinated biphenyl (PCB) congeners with ortho substituents have potential to cause neurotoxicity. Many PCB congeners implicated in these neurotoxic effects are chiral. It is currently unknown if the enantiomers of a chiral PCB congeners have differe...

  13. Influência do grau de substituição e da distribuição de substituintes sobre as propriedades de equilíbrio de carboximetilcelulose em solução aquosa Influence of the degree of substitution and substituent distribution on the equilibrium properties of carboxymethylcellulose in aqueous solution

    Directory of Open Access Journals (Sweden)

    José Cláudio Caraschi

    1999-06-01

    Full Text Available Amostras de carboximetilcelulose foram preparadas por reação heterogênea de polpa soda/antraquinona obtida de fibras pré-hidrolisadas de bagaço de cana-de-açúcar. As amostras com os menores graus de substituição ( > 1,0 apresentaram comportamentos diferentes quanto a: i variação de constante aparente de acidez (pk ap com o grau de dissociação; ii concordância entre os valores de determinados por titulações e por espectroscopia ¹H rmn e iii concordância entre os valores experimentais de coeficientes de transporte e os previstos pelo modelo de Manning. Todas as amostras apresentaram um padrão de substituição em blocos que, nas amostras menos substituídas são curtos e espaçados, favorecendo interações associativas que levam à agregação. Efeitos de volume excluído eletrostático, mais importantes nas amostras mais substituídas, inibem a agregação e explicam o comportamento observado nesses casos.Samples of carboxymethylcellulose were prepared by the heterogeneous reaction of the soda/anthraquinone pulp obtained from sugar cane bagasse. The less substituted samples (DS 1,0 showed different behaviors concerning to: i the dependence of pk ap on the degree of neutralization; ii the agreement between DS values determined by titrations and by ¹H nmr spectroscopy and iii the agreement between the experimental values of transport coefficients (f and the ones calculated by applying the Manning theoretical approach. All samples showed a block distribution of substituents which, in the case of the less substituted samples, are short and well separated, favoring the occurrence of associative interactions and of aggregation. Electrostatic excluded volume effects, which are more important for the more substituted samples, inhibit the aggregation and may explain the behavior of these samples.

  14. Synthesis, crystal structures, and optical properties of the π-π interacting pyrrolo[2,3-b]quinoxaline derivatives containing 2-thienyl substituent

    Science.gov (United States)

    Goszczycki, Piotr; Stadnicka, Katarzyna; Brela, Mateusz Z.; Grolik, Jarosław; Ostrowska, Katarzyna

    2017-10-01

    Three (E/Z)-diastereoisomers, based on pyrrolo[2,3-b]quinoxaline system as fluorophore and containing: 2-thienylmethyl (1), bis(2-thienylmethyl)-2-aminoethyl (3a), bis(2-thienylmethyl)-3-aminopropyl (3b) groups as substituents, were synthesized and characterized by X-ray structural analysis, PXRD, NMR, UV-Vis as well as fluorescence. These compounds are non-fluorescent in acetonitrile solution, however, they exhibit aggregation induced emission enhancement (AIEE) upon water addition and in solid state. X-ray structural analysis revealed that molecules with 2-thienylmethyl and bis(2-thienylmethyl)-2-aminoethyl groups form dimers and π-stacks through π-π interactions between anitiparallel oriented pyrroloquinoxaline cores with interplanar distances 3.45 Å and 3.20 Å, respectively. Conformation of bis(2-thienylmethyl)-3-aminopropyl group is imposed by incorporated DMSO-d6 solvent molecule and weak intermolecular S-π and CH-π interactions, that prevents π-π interaction between fluorophore cores. The correlation between crystal structure and fluorescent properties of synthesized molecules was discussed. The DFT calculations were performed to rationalize the differences between considered systems.

  15. Synthesis of modified proanthocyanidins: introduction of acyl substituents at C-8 of catechin. Selective synthesis of a C-4-->O-->C-3 ether-linked procyanidin-like dimer.

    Science.gov (United States)

    Beauhaire, Josiane; Es-Safi, Nour-Eddine; Boyer, François-Didier; Kerhoas, Lucien; Guernevé, Christine le; Ducrot, Paul-Henri

    2005-02-01

    The regioselective introduction of substituents at C-8 of (+)-catechin is described, leading to the synthesis of several catechin derivatives with various substitution patterns to be used for the further synthesis of modified proanthocyanidins. Thereafter, a new 3-O-4 ether-linked procyanidin-like derivative was synthesized. Its formation was selectively achieved through TiCl(4)-catalyzed condensation of 4-(2-hydroxyethoxy)tetra-O-benzyl catechin with the 8-trifluoroacetyl adduct of tetra-O-benzyl catechin.

  16. The evolutive aspect of the short jat substituents following the sonant r - a comparison between the Serbian literary language and the dialect of Vuk’s ancestors

    Directory of Open Access Journals (Sweden)

    Ostojić Vladimir B.

    2015-01-01

    Full Text Available The paper discusses the evolutive aspects of short “jat” following the sonant r usage during the formation of the modern Serbian literary language and its treatment in the Serbo-Croatistic and the Serbistic descriptive and normative literature. In addition to the basic issue of the distribution of the short “jat’s” substituent following the sonant r in dialects of Montenegro, particularly in the native dialect of Vuk Karadžić’s ancestors, the author also addresses the question related to the mechanisms that cause short “jat” following the sonant r in ijekavian dialects to be reduced sometimes to e, and sometimes to je. Substitution of short “jat” following the sonant r in Jezera-Šarani dialect had important evolution from the times of “classical Vukovian ijekavism”. In this dialect, forms with rje do not occur, except in the word starješina. Here, r and j remained in the same syllable, which set the stage for iotization and depalatalization. The analysis of the paper describes the situation in Jezera-Šarani dialect as well as the situation in other Montenegrian dialects of the older and newer Eastern-Herzegovian type. The author as well takes into consideration that our Pravopis has already disregarded the Vukovian tradition with omitting j that follows sonant r in the examples pogreška and greška. In order to eliminate the disunity, the author concludes that the status of the group re should not be questioned from the aspect of literary language standards.

  17. Theoretical Investigation on Charge Transfer Properties of 1,3,5-Tripyrrolebenzene (TPB and its Derivatives with Electron-withdrawing Substituents

    Directory of Open Access Journals (Sweden)

    Yong Hu

    2016-06-01

    Full Text Available The electronic structures and charge transport properties of 1,3,5-tripyrrolebenzene (TPB and its substituted derivatives with –F and –CN groups have been investigated by DFT calculations in combination with the Marcus hopping model. The dimer geometry was optimized by density functional theory method with dispersion force correction being included (DFT-D. Consequently, the charge transfer integral was evaluated. The calculation results show that the introduction of electron-withdrawing substituents does not significantly change the bond lengths and molecular symmetry of TPB, but lower the coplanarity between the pyrrole and benzene rings, especially in the case of CN substitution. Meanwhile, the introduction of electron-withdrawing groups can decrease the energy of the frontier molecular orbital and enhance the air stability. Fluorination makes the λe increase obviously while cyanation dose not. Generally speaking, the λe values of the title compounds are larger than their λh. Except for compounds 6 and 9, all others keep the face to face packing or have a slight slip in dimers, but the center of mass distances increase after fluorination or cyanation due to the distortion of the monomer’s coplanarity. The predicted quasi-one-dimensional electron mobility of the dimers is up to 0.433 cm2 V-1 s-1 at 298.15 K. The electron injection barriers of 2 and 7 are lower than that of TPB. The TPB derivatives of 1, 2, and 7 are potential n-channel materials with the high electron mobility. This work is licensed under a Creative Commons Attribution 4.0 International License.

  18. Directing the breathing behavior of pillared-layered metal-organic frameworks via a systematic library of functionalized linkers bearing flexible substituents.

    Science.gov (United States)

    Henke, Sebastian; Schneemann, Andreas; Wütscher, Annika; Fischer, Roland A

    2012-06-06

    Flexible metal-organic frameworks (MOFs), also referred to as soft porous crystals (SPCs), show reversible structural transitions dependent on the nature and quantity of adsorbed guest molecules. In recent studies it has been reported that covalent functionalization of the organic linker can influence or even integrate framework flexibility ("breathing") in MOFs. However, rational fine-tuning of such responsive properties is very desirable but challenging as well. Here we present a powerful approach for the targeted manipulation of responsiveness and framework flexibility of an important family of pillared-layered MOFs based on the parent structure [Zn(2)(bdc)(2)(dabco)](n) (bdc = 1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane). A library of functionalized bdc-type linkers (fu-bdc), which bear additional dangling side groups at different positions of the benzene core (alkoxy groups of varying chain length with diverse functionalities and polarity), was generated. Synthesis of the materials [Zn(2)(fu-bdc)(2)(dabco)](n) yields the respective collection of highly responsive MOFs. The parent MOF is only weakly flexible; however, the substituted frameworks of [Zn(2)(fu-bdc)(2)(dabco)](n) contract drastically upon guest removal and expand again upon adsorption of DMF (N,N-dimethylformamide), EtOH, or CO(2), etc., while N(2) is hardly adsorbed and does not open the narrow-pored form. These "breathing" dynamics are attributed to the dangling side chains that act as immobilized "guests", which interact with mobile guest molecules as well as with themselves and with the framework backbone. The structural details of the guest-free, contracted form and the gas sorption behavior (phase transition pressure, hysteresis loop) are highly dependent on the nature of the substituent at the linker and can therefore be adjusted using our approach. Combining our library of functionalized linkers with the concept of mixed-component MOFs (solid solutions) offers very rich

  19. Kinetic Study on Nucleophilic Substitution Reactions of 4-Chloro-2-nitrophenyl X-Substituted-benzoates with Cyclic Secondary Amines: Effect of Substituent X on Reactivity and Reaction Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Seong Hoon; Kim, Hyun Soo; Han, Young Joon [Sejong Science High School, Seoul (Korea, Republic of); Kim, Minyoung; Um, Ikhwan [Ewha Woman' s Univ., Seoul (Korea, Republic of)

    2013-10-15

    Second-order rate constants (k{sub N}) have been measured spectrophotometrically for the reactions of 4-chloro-2-nitrophenyl X-substituted-benzoates (1a-1h) with a series of cyclic secondary amines in 80 mol % H{sub 2}O/20 mol % DMSO at 25.0 ± 0.1 .deg. C. The Hammett plot for the reactions of 1a-1h with piperidine consists of two intersecting straight lines, while the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρ{sub X} = 1.25 and r = 0.58, indicating that the nonlinear Hammett plot is not due to a change in the rate-determining step (RDS) but is caused by ground-state stabilization through resonance interactions for substrates possessing an electron-withdrawing group in the benzoyl moiety. The Brφnsted-type plot for the reactions of 4-chloro-2-nitrophenyl benzoate (1d) with a series of cyclic secondary amines curves downward with β{sub 2} = 0.85, β{sub 1} = 0.24, and pK{sub a}{sup o} = 10.5, implying that a change in RDS occurs from the k{sub 2} step to the k{sub 1} process as the pK{sub a} of the conjugate acid of the amine exceeds 10.5. Dissection of k{sub N} into the microscopic rate constants k{sub 1} and k{sub 2}/k{sub -1} ratio associated with the reaction of 1d reveals that k{sub 2} is dependent on the amine basicity, which is contrary to generally held views.

  20. Substituent and noncovalent interaction effects in the reactivity of purine derivatives with tetracarboxylato-dirhodium(II) units. Rationalization of a rare binding mode via N3.

    Science.gov (United States)

    Amo-Ochoa, Pilar; Castillo, Oscar; Harrington, Ross W; Zamora, Félix; Houlton, Andrew

    2013-02-18

    Reactions between [Rh(2)(CH(3)COO)(4)] with 2,6-diaminopurine (HDap) or 6-chloro-2-aminopurine (HClap) and [Rh(2)((CH(3))(3)CCOO)(4)] with HClap produce, three new dirhodium(II) carboxylate complexes of the general form, [Rh(2)(RCOO)(4)(Purine)(2)] (R = CH(3), (CH(3))(3)C). Single crystal X-ray diffraction studies confirm that in all cases the purine coordinates to the axial position of the dirhodium(II)tetracarboxylate unit. However, while the complex obtained with HDap features the typical purine binding mode via N(7), complexes containing HClap show unusual N3 coordination. This is an extremely rare instance of an unrestricted purine binding via N3. Some rationalization of these data is offered based on a series of DFT calculations.

  1. "1H and "1"3C NMR Data on Hydroxy/methoxy Flavonoids and the Effects of Substituents on Chemical Shifts

    International Nuclear Information System (INIS)

    Yoon, Hyuk; Eom, Sung Lock; Hyun, Ji Ye; Jo, Geun Hyeong; Hwang, Do Seok; Lee, Sun Hee; Yong, Yeon Joong; Lee, Young Han; Lim, Yoong Ho; Park, Jun Cheol

    2011-01-01

    Polyphenols have recently been examined for such applications, and they are classified based on their carbon skeletons: phenolic acids with C6-C1 skeleton, hydrocinammates with C6-C_3 skeleton, stilbenes with C6-C2-C6 skeleton, and flavonoids with C6-C_3-C6 skeleton.2 Of these compounds, flavonoids are ubiquitously found in most plants. Since flavonoids belong to polyphenols, they have many hydroxy groups. From a bioavailability point of view, hydroxy groups prevent cell membrane transport, and hydroxyflavonoids can be metabolized by O-methyltransferases. However, methoxylated flavonoids may not have these problems. Hydroxylated or methoxylated flavonoids are found from natural sources. Nuclear magnetic resonance (NMR) spectroscopy is widely used to identify different compounds including hydroxylated or methoxylated flavonoids. Because the position and the number of substituted hydroxy or/and methoxy groups will change the "1H and "1"3C chemical shifts, it is important to understand these changes so that the structures of newly isolated hydroxy/methoxy-flavonoids can be easily identified

  2. Picolinamide-Based Iridium Catalysts for Dehydrogenation of Formic Acid in Water: Effect of Amide N Substituent on Activity and Stability.

    Science.gov (United States)

    Kanega, Ryoichi; Onishi, Naoya; Wang, Lin; Murata, Kazuhisa; Muckerman, James T; Fujita, Etsuko; Himeda, Yuichiro

    2018-03-01

    To develop highly efficient catalysts for dehydrogenation of formic acid in water, we investigated several Cp*Ir catalysts with various amide ligands. The catalyst with an N-phenylpicolinamide ligand exhibited a TOF of 118 000 h -1 at 60 °C. A constant rate (TOF>35 000 h -1 ) was maintained for six hours, and a TON of 1 000 000 was achieved at 50 °C. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Benzazepines: Structure-activity relationships between D1 receptor blockade and selected pharmacological effects

    International Nuclear Information System (INIS)

    Iorio, L.C.; Billiard, W.; Gold, E.H.

    1986-01-01

    This chapter describes the displacement of 3 H-23390 and 3 H-spiperone binding by dopamine agonists and antagonists. The authors undertook an evaluation of the ability of selected analogs of SCH 23390 to displace 3 H-SCH 23390 and 3 H-spiperone. Structure-activity relationships of SCH 23390 analogs: 7-position substituents, is shown. It is shown that, in general, benzazepines with a variety of substituents in the 7-position retain their selectivity for D 1 sites. Substituents at the 8-position and at the N-position are also discussed. The authors determine a correlation between displacement of 3 H-SCH 23390 and blockade of dopamine-sensitive adenylate cyclase (DSAC). These effects and inhibition of conditioned avoidance responsing (CAS) in rats was also studied. A detailed evaluation is presented of the effects of SCH 23390 and haloperidol in the Inclined Screen and CAR tests

  4. Investigation of the Effects in ß-Mannosylation & Easy Access to L-Sugars via CH Activation

    DEFF Research Database (Denmark)

    Frihed, Tobias

    The overall themes of the research described in this PhD thesis includes effects in β-mannosylation (part I) and synthesis of L-sugars by C-H activation (part II). Part I: One of the most difficult glycosidic linkage to synthesize is the β-mannosides (Chapter 1). These are tricky to prepare due...... in the glycosylations it was concluded that the β-selectivity arise from a conformational effect induced by the 4,6-O-benzylidene. The stereoelectronic effect of the locked O6 in a tg position was less important. Part II: The rare but biologically important L-hexoses (and 6-deoxy-L-sugars) is not accesible from natural...... sources in large quantaties. Therefore, synthesis of the L-sugars must be prepared chemically in order to study them (Chapter 4). The synthesis of all eight 6-deoxy-L-hexoses as their thiodonors were achieved and is decribed (Chapter 5). The preparation was based on the only two common 6-deoxy...

  5. Effects of stereochemistry on the rates of hydrogen--deuterium exchange of protons α to the nitrosamino group

    International Nuclear Information System (INIS)

    Fraser, R.R.; Ng, L.K.

    1976-01-01

    Measurement of the rates of exchange of four benzylic protons of rigid dibenzazepine were made in tert-butyl alcohol-O-d containing potassium tert-butoxide at several concentrations. Each pseudoaxial proton exchanged 100-fold faster than its geminal partner (pseudoequatorial), likely as a result of a stereoelectronic effect. Each syn proton exchanged 1000-fold faster than the anti proton in the same biaryl environment. The lack of any significant effect of added crown either on the rate of exchange of either a syn or an antiproton indicates lack of involvement of the counterion. A suggested explanation for the unusual preference for syn exchange in this work is based on the symmetry properties of the anionic intermediate. This intermediate, like butadiene dianion, has an attractive interaction between the terminal atoms of the four-atom π system in the highest occupied molecular orbital (HOMO). This explanation is similar to that of Epiotis and co-workers, which accounts for the well-established preferential stability of cis over trans dihalo and dialkoxy ethylenes

  6. Contribution to the study of the {sup 31}P, {sup 1}H spin spin coupling constant N. M. R. in three co-ordinated phosphorus compounds. Influence of the bond orientation and of the nature of the substituent around the phosphorus atom; Contribution a l'etude des constantes de couplage {sup 31}P, {sup 1}H en R.M.N. dans les composes organo-phosphores tricoordines. Influence des facteurs geometriques et de la nature des substituants au niveau du phosphore

    Energy Technology Data Exchange (ETDEWEB)

    Robert, J B [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    In order to investigate the influence of the configuration at the phosphorus atom and the influence of the substituents attached to the phosphorus atom on the J{sub PH} spin spin coupling constant, we have performed the NMR spectrum analysis of some three coordinated organo-phosphorus compounds. The studied coupling constants are {sup 3}J{sub PH} through P-O-C-H and P-C-C-H fragments and {sup 2}J{sub PH} through P-C-H fragment. The results clearly show that on the NMR time scale, in all the studied compounds (1,3,2-dioxaphospholanes, 1,3,2-dioxaphosphorinanes, 3-phospha-cyclopentene and 4-phosphorinanone) there is no inversion of the bonds around phosphorous. This conclusion held also for secondary phosphines. For a given geometry of the bonds joining the P and H atoms, and a given disposition of the bonds around the phosphorus atom, there is only a little influence of the nature of the substituents on the J{sub PH} spin coupling constants. The geometrical dependence of the {sup 3}J{sub PH} cannot be explained by a 'Karplus law'. There is an influence of the bond disposition around phosphorus. In the case of the {sup 2}J{sub P-C-H}, one can plot a curve {sup 2}J{sub P-C-H} = f({alpha}) (0{<=} {alpha} {<=} 180), {alpha} denote the dihedral angle of the two plane defined the first one by the P, C and H atoms, and the second one by the P-C bond together with the three-fold axis of the bond around phosphorus assuming a regular pyramidal arrangement. The function {sup 2}J{sub P-C-H} = f({alpha}) has two maxima, one for {alpha} = 0 degrees and the other for {alpha} = 180 degrees, and also a minimum for {alpha} = 110 degrees. (author) [French] Ce travail consiste en l'analyse par resonance magnetique nucleaire des constantes de couplage phosphore-proton dans des derives organo-phosphores tricoordines dans un double but: examen de la stabilite des liaisons au niveau du phosphore et etude de l'influence de la disposition des liaisons et de la nature de substituants au

  7. Influence of the substituents on the electronic and electrochemical properties of a new square-planar nickel-bis(quinoxaline-6,7-dithiolate) system: synthesis, spectroscopy, electrochemistry, crystallography, and theoretical investigation.

    Science.gov (United States)

    Bolligarla, Ramababu; Reddy, Samala Nagaprasad; Durgaprasad, Gummadi; Sreenivasulu, Vudagandla; Das, Samar K

    2013-01-07

    We describe the synthesis, crystal structures, electronic absorption spectra, and electrochemistry of a series of square-planar nickel-bis(quinoxaline-6,7-dithiolate) complexes with the general formula [Bu(4)N](2)[Ni(X(2)6,7-qdt)(2)], where X = H (1a), Ph (2a), Cl (3), and Me (4). The solution and solid-state electronic absorption spectral behavior and electrochemical properties of these compounds are strongly dependent on the electron donating/accepting nature of the substituent X, attached to the quinoxaline-6,7-dithiolate ring in the system [Bu(4)N](2)[Ni(X(2)6,7-qdt)(2)]. Particularly, the charge transfer (CT) transition bands observed in the visible region are greatly affected by the electronic nature of the substituent. A possible explanation for this influence of the substituents on electronic absorption and electrochemistry is described based on highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) gaps, which is further supported by ground-state electronic structure calculations. In addition to this, the observed CT bands in all the complexes are sensitive to the solvent polarity. Interestingly, compounds 1a, 2a, 3, and 4 undergo reversible oxidation at very low oxidation potentials appearing at E(1/2) = +0.12 V, 0.033 V, 0.18 V, and 0.044 V vs Ag/AgCl, respectively, in MeOH solutions, corresponding to the respective couples [Ni(X(2)6,7-qdt)(2)](-)/[Ni(X(2)6,7-qdt)(2)](2-). Compounds 1a, 3, and 4 have been characterized unambiguously by single crystal X-ray structural analysis; compound 2a could not be characterized by single crystal X-ray structure determination because of the poor quality of the concerned crystals. Thus, we have synthesized the tetraphenyl phosphonium salt of the complex anion of 2a, [PPh(4)](2)[Ni(Ph(2)6,7-qdt)(2)]·3DMF (2b) for its structural characterization.

  8. Proton affinity of diastereoisomers of modified prolines using the kinetic method and density functional theory calculations: role of the cis/trans substituent on the endo/exo ring conformation.

    Science.gov (United States)

    Mezzache, S; Pepe, C; Karoyan, P; Fournier, F; Tabet, J-C

    2005-01-01

    The proton affinity (PA) of cis/trans-3-prolinoleucines and cis/trans-3-prolinoglutamic acids have been studied by the kinetic method and density functional theory (DFT) calculations. Several conformations of the neutral and the protonated modified prolines, in particular the endo and exo ring conformations, were analyzed with respect to their contribution to the PA values. When the substituent is an alkyl, both the diastereoisomers have the same PA value. However, the PA values for the diastereoisomers are different when the substituted chain contains functional groups (e.g. a carboxyl group). This variation in PA values could be attributed to the existence of intramolecular hydrogen bonds. Copyright (c) 2005 John Wiley & Sons, Ltd.

  9. The molecular structure effects in hydrogenation of cycloalkylsubstituted alkynes and alkenes on platinum and palladium catalysts

    Czech Academy of Sciences Publication Activity Database

    Kačer, P.; Kuzma, Marek; Červený, L.

    2004-01-01

    Roč. 259, - (2004), s. 179-183 ISSN 0926-860X R&D Projects: GA ČR GA104/00/1009 Institutional research plan: CEZ:AV0Z5020903 Keywords : adsorptivity * competitive hydrogenation * substituent effects Subject RIV: EE - Microbiology, Virology Impact factor: 2.378, year: 2004

  10. effect of side chain length on the stability and structural properties of 3

    African Journals Online (AJOL)

    Preferred Customer

    We report on the effect of the alkoxy chain length on the thermodynamic ... studied by Hartree-Fock (HF) and Density Functional Theory (DFT) methods. ..... with longer alkoxy substituents on the phenyl ring have lesser value of change in Gibbs ...

  11. Stereoelectronic model to explain the resolution of enantiomeric ibuprofen amides on the Pirkle chiral stationary phase.

    Science.gov (United States)

    Nicoll-Griffith, D A

    1987-07-31

    A chiral recognition model is proposed which incorporates the electronic and steric interactions between amide derivatives of ibuprofen and the (R)-N-(3,5-dinitrobenzoyl)phenylglycine-derived Pirkle chiral stationary phase during high-performance liquid chromatography. Based on this rationale, amide derivatives of ibuprofen were prepared using 4-chloroaniline, 4-bromoaniline, aniline, 4-methoxyaniline and 1-aminonaphthylene to improve the enantiomer separation over previously reported results with this column. The amides prepared gave separation values of 1.16, 1.16, 1.19, 1.21 and 1.23, respectively. These high separation values are consistent with the proposed model.

  12. Bibliography on vapour pressure isotope effects

    International Nuclear Information System (INIS)

    Illy, H.; Jancso, G.

    1976-03-01

    The bibliography of research on vapour pressure isotope effects from 1919 to December 1975 is presented in chronological order. Within each year the references are listed alphabetically according to the name of the first author of each work. The bibliography is followed by a Compound Index containing the names o compounds, but the type of isotopic substituation is not shown. The Author Index includes all authors of the papers. (Sz.N.Z.)

  13. Asymmetric diketopyrrolopyrrole conjugated polymers for field-effect transistors and polymer solar cells processed from a non-chlorinated solvent

    NARCIS (Netherlands)

    Ji, Y.; Xiao, C.; Wang, Q.; Zhang, J.; Li, C.; Wu, Y.; Wei, Z.; Zhan, X.; Hu, W.; Wang, Z.; Janssen, R.A.J.; Li, W.W.

    2016-01-01

    Newly designed asymmetric diketopyrrolopyrrole conjugated polymers with two different aromatic substituents possess a hole mobility of 12.5 cm2 V−1 s−1 in field-effect transistors and a power conversion efficiency of 6.5% in polymer solar cells, when solution processed from a nonchlorinated

  14. pn-Heterojunction effects of perylene tetracarboxylic diimide derivatives on pentacene field-effect transistor.

    Science.gov (United States)

    Yu, Seong Hun; Kang, Boseok; An, Gukil; Kim, BongSoo; Lee, Moo Hyung; Kang, Moon Sung; Kim, Hyunjung; Lee, Jung Heon; Lee, Shichoon; Cho, Kilwon; Lee, Jun Young; Cho, Jeong Ho

    2015-01-28

    We investigated the heterojunction effects of perylene tetracarboxylic diimide (PTCDI) derivatives on the pentacene-based field-effect transistors (FETs). Three PTCDI derivatives with different substituents were deposited onto pentacene layers and served as charge transfer dopants. The deposited PTCDI layer, which had a nominal thickness of a few layers, formed discontinuous patches on the pentacene layers and dramatically enhanced the hole mobility in the pentacene FET. Among the three PTCDI molecules tested, the octyl-substituted PTCDI, PTCDI-C8, provided the most efficient hole-doping characteristics (p-type) relative to the fluorophenyl-substituted PTCDIs, 4-FPEPTC and 2,4-FPEPTC. The organic heterojunction and doping characteristics were systematically investigated using atomic force microscopy, 2D grazing incidence X-ray diffraction studies, and ultraviolet photoelectron spectroscopy. PTCDI-C8, bearing octyl substituents, grew laterally on the pentacene layer (2D growth), whereas 2,4-FPEPTC, with fluorophenyl substituents, underwent 3D growth. The different growth modes resulted in different contact areas and relative orientations between the pentacene and PTCDI molecules, which significantly affected the doping efficiency of the deposited adlayer. The differences between the growth modes and the thin-film microstructures in the different PTCDI patches were attributed to a mismatch between the surface energies of the patches and the underlying pentacene layer. The film-morphology-dependent doping effects observed here offer practical guidelines for achieving more effective charge transfer doping in thin-film transistors.

  15. The 3,7-diazabicyclo[3.3.1]nonane scaffold for subtype selective nicotinic acetylcholine receptor (nAChR) ligands. Part 1: the influence of different hydrogen bond acceptor systems on alkyl and (hetero)aryl substituents.

    Science.gov (United States)

    Eibl, Christoph; Tomassoli, Isabelle; Munoz, Lenka; Stokes, Clare; Papke, Roger L; Gündisch, Daniela

    2013-12-01

    3,7-Diazabicyclo[3.3.1]nonane is a naturally occurring scaffold interacting with nicotinic acetylcholine receptors (nAChRs). When one nitrogen of the 3,7-diazabicyclo[3.3.1]nonane scaffold was implemented in a carboxamide motif displaying a hydrogen bond acceptor (HBA) functionality, compounds with higher affinities and subtype selectivity for α4β2(∗) were obtained. The nature of the HBA system (carboxamide, sulfonamide, urea) had a strong impact on nAChR interaction. High affinity ligands for α4β2(∗) possessed small alkyl chains, small un-substituted hetero-aryl groups or para-substituted phenyl ring systems along with a carboxamide group. Electrophysiological responses of selected 3,7-diazabicyclo[3.3.1]nonane derivatives to Xenopus oocytes expressing various nAChR subtypes showed diverse activation profiles. Compounds with strongest agonistic profiles were obtained with small alkyl groups whereas a shift to partial agonism/antagonism was observed for aryl substituents. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Synthesis, β-haematin inhibition, and in vitro antimalarial testing of isocryptolepine analogues: SAR study of indolo[3,2-c]quinolines with various substituents at C2, C6, and N11.

    Science.gov (United States)

    Wang, Ning; Wicht, Kathryn J; Imai, Kento; Wang, Ming-Qi; Anh Ngoc, Tran; Kiguchi, Ryo; Kaiser, Marcel; Egan, Timothy J; Inokuchi, Tsutomu

    2014-05-01

    A series of indolo[3,2-c]quinolines were synthesized by modifying the side chains of the ω-aminoalkylamines at the C6 position and introducing substituents at the C2 position, such as F, Cl, Br, Me, MeO and NO2, and a methyl group at the N11 position for an SAR study. The in vitro antiplasmodial activities of the derivative agents against two different strains (CQS: NF54 and CQR: K1) and the cytotoxic activity against normal L6 cells were evaluated. The test results showed that compounds 6k and 6l containing the branched methyl groups of 3-aminopropylamino at C6 with a Cl atom at C2 exhibited a very low cytotoxicity with IC50 values above 4000 nM, high antimalarial activities with IC50 values of about 11 nM for CQS (NF54), IC50 values of about 17 nM for CQR (K1), and RI resistance indices of 1.6. Furthermore, the compounds were tested for β-haematic inhibition, and QSAR revealed an interesting linear correlation between the biological activity of CQS (NF54) and three contributing factors, namely solubility, hydrophilic surface area, and β-haematin inhibition for this series. In vivo testing of 6l showed a reduction in parasitaemia on day 4 with an activity of 38%. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Síntese e atividade antibacteriana de imidas cíclicas: 3,4-dicloromaleimidas e 3-cloro-4-substituída-maleimidas

    Directory of Open Access Journals (Sweden)

    Andricopulo Adriano Defini

    1998-01-01

    Full Text Available In the present study, new N-aryl and N-alkylarylcyclic imides were synthesized and their antibacterial properties against Escherichia coli and Staphylococcus aureus were evaluated by using the diffusion method. All compounds were obtained in good yield (54 - 95% and characterized by spectral data (¹H-NMR, MS, IR and elemental analysis (CHN. The biological results indicated that some compounds exert significative antibacterial effects, confirming previous studies on biological activities of cyclic imides.

  18. Design concept for α-hydrogen-substituted nitroxides.

    Science.gov (United States)

    Amar, Michal; Bar, Sukanta; Iron, Mark A; Toledo, Hila; Tumanskii, Boris; Shimon, Linda J W; Botoshansky, Mark; Fridman, Natalia; Szpilman, Alex M

    2015-02-06

    Stable nitroxides (nitroxyl radicals) have many essential and unique applications in chemistry, biology and medicine. However, the factors influencing their stability are still under investigation, and this hinders the design and development of new nitroxides. Nitroxides with tertiary alkyl groups are generally stable but obviously highly encumbered. In contrast, α-hydrogen-substituted nitroxides are generally inherently unstable and rapidly decompose. Herein, a novel, concept for the design of stable cyclic α-hydrogen nitroxides is described, and a proof-of-concept in the form of the facile synthesis and characterization of two diverse series of stable α-hydrogen nitroxides is presented. The stability of these unique α-hydrogen nitroxides is attributed to a combination of steric and stereoelectronic effects by which disproportionation is kinetically precluded. These stabilizing effects are achieved by the use of a nitroxide co-planar substituent in the γ-position of the backbone of the nitroxide. This premise is supported by a computational study, which provides insight into the disproportionation pathways of α-hydrogen nitroxides.

  19. Valency and spin states of substituent cations in Bi2.15Sr1.85CaCu2O8+δ

    Science.gov (United States)

    Benseman, T. M.; Cooper, J. R.; Zentile, C. L.; Lemberger, L.; Balakrishnan, G.

    2011-10-01

    We studied the valency and spin behavior of M = Mn, Fe, Co, Li, and Al in the high-temperature superconducting compound Bi2.15Sr1.85Ca(Cu1-zMz)2O8+δ (Bi-2212) for small values of z. Mn, Fe, and Co retain their magnetic moments, and our thermopower and magnetic susceptibility data imply ionization states Mn3+, Fe2+, and Co2+, while Li and Al are accommodated in the charge reservoir layers. Single-crystal studies show that the susceptibility of Co2+ ions in Bi-2212 is strongly anisotropic, with a weak anisotropy detected for Mn3+ and none for Fe2+. Fits to a pseudogap formula for a pure Bi-2212 crystal suggest that the spin susceptibility of the host compound is more anisotropic than previously realized. Data in the superconducting state allow us to compare the pair-breaking properties of the different impurities. Several aspects of the data, including the stronger suppression of the superconducting transition temperature Tc by Co compared with Fe for underdoped and optimally doped samples, show that the d-level structure of the magnetic ions and multiorbital effects are important. We also find that the temperatures of the magnetization crossing points are equal to the low-field Tc values to within 1% or 2%. This agrees with a 2D thermodynamic fluctuation argument given by Junod

  20. Effect of a bulky lateral substitution by chlorine atom and methoxy group on self-assembling properties of lactic acid derivatives

    International Nuclear Information System (INIS)

    Stojanović, Maja; Bubnov, Alexej; Obadović, Dušanka Ž.; Hamplová, Věra; Cvetinov, Miroslav; Kašpar, Miroslav

    2014-01-01

    Several chiral liquid crystalline materials derived from the lactic acid have been studied with the aim to establish the effect of bulky lateral substituents on their self-assembling properties. A chlorine atom and methoxy group have been used as lateral substituents in ortho position to ether group position on phenyl ring far from the chiral centre. All the studied materials possess tilted ferroelectric smectic C* phase in a broad temperature range. In dependence on the molecular structure namely type of lateral substituent and length of the chiral chain, the cholesteric mesophase, orthogonal paraelectric smectic A* and crystal mesophases have been detected. Lateral chlorine substitution results in decrease of both the clearing point and crystallisation temperature as well as in a distinct increase of spontaneous polarization. Bulky methoxy substitution slightly suppresses the spontaneous polarisation but strongly increases the melting point that results in monotropic peculiarity of the SmC* phase. Mesomorphic, spontaneous, structural and dielectric properties of the substituted compounds were established and compared to those of the non-substituted ones in order to contribute to better understanding of the structure–property relationship for such chiral self-assembling materials. - Highlights: • Chiral liquid crystalline materials derived from the lactic acid have been studied. • Effect of bulky lateral substituents on self-assembling properties has been established. • Bulky methoxy substitution suppresses spontaneous polarisation but increases the melting point. • The compounds might have a strong potential for many advanced electro-optic applications

  1. Mesogenic benzothiazole derivatives with methoxy substituents

    Indian Academy of Sciences (India)

    Unknown

    2003-10-11

    Oct 11, 2003 ... literature. Barbera et al14 have synthesized 2-pyr- azoline derivatives and also studied the optical,. NLO and mesogenic properties of such materials. Highly polar thiophene-based liquid crystals have also been reported15 in the literature. However, fused ring heterocyclic derivatives which are two conden-.

  2. Contribution to the study of the {sup 31}P, {sup 1}H spin spin coupling constant N. M. R. in three co-ordinated phosphorus compounds. Influence of the bond orientation and of the nature of the substituent around the phosphorus atom; Contribution a l'etude des constantes de couplage {sup 31}P, {sup 1}H en R.M.N. dans les composes organo-phosphores tricoordines. Influence des facteurs geometriques et de la nature des substituants au niveau du phosphore

    Energy Technology Data Exchange (ETDEWEB)

    Robert, J.B. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1969-07-01

    In order to investigate the influence of the configuration at the phosphorus atom and the influence of the substituents attached to the phosphorus atom on the J{sub PH} spin spin coupling constant, we have performed the NMR spectrum analysis of some three coordinated organo-phosphorus compounds. The studied coupling constants are {sup 3}J{sub PH} through P-O-C-H and P-C-C-H fragments and {sup 2}J{sub PH} through P-C-H fragment. The results clearly show that on the NMR time scale, in all the studied compounds (1,3,2-dioxaphospholanes, 1,3,2-dioxaphosphorinanes, 3-phospha-cyclopentene and 4-phosphorinanone) there is no inversion of the bonds around phosphorous. This conclusion held also for secondary phosphines. For a given geometry of the bonds joining the P and H atoms, and a given disposition of the bonds around the phosphorus atom, there is only a little influence of the nature of the substituents on the J{sub PH} spin coupling constants. The geometrical dependence of the {sup 3}J{sub PH} cannot be explained by a 'Karplus law'. There is an influence of the bond disposition around phosphorus. In the case of the {sup 2}J{sub P-C-H}, one can plot a curve {sup 2}J{sub P-C-H} = f({alpha}) (0{<=} {alpha} {<=} 180), {alpha} denote the dihedral angle of the two plane defined the first one by the P, C and H atoms, and the second one by the P-C bond together with the three-fold axis of the bond around phosphorus assuming a regular pyramidal arrangement. The function {sup 2}J{sub P-C-H} = f({alpha}) has two maxima, one for {alpha} = 0 degrees and the other for {alpha} = 180 degrees, and also a minimum for {alpha} = 110 degrees. (author) [French] Ce travail consiste en l'analyse par resonance magnetique nucleaire des constantes de couplage phosphore-proton dans des derives organo-phosphores tricoordines dans un double but: examen de la stabilite des liaisons au niveau du phosphore et etude de l'influence de la disposition des liaisons et de la nature de

  3. Displacement of ethene from the decamethyltitanocene-ethene complex with internal alkynes, substituent-dependent alkyne-to-allene rearrangement, and the electronic transition relevant to the back-bonding interaction.

    Science.gov (United States)

    Pinkas, Jiří; Gyepes, Róbert; Císařová, Ivana; Kubišta, Jiří; Horáček, Michal; Mach, Karel

    2015-04-28

    The titanocene-ethene complex [Ti(II)(η(2)-C2H4)(η(5)-C5Me5)2] (1) with simple internal alkynes R(1)C≡CR(2) gives complexes [Ti(II)(η(2)-R(1)C≡CR(2))(η(5)-C5Me5)2] {R(1), R(2): Ph, Ph (3), Ph, Me (4), Me, SiMe3 (5), Ph, SiMe3 (6), t-Bu, SiMe3 (7), and SiMe3, SiMe3 (8). In contrast, alkynes with R(1) = Me and R(2) = t-Bu or i-Pr afford allene complexes [Ti(II)(η(2)-CH2=C=CHR(2))(η(5)-C5Me5)2] (11) and (12), whereas for R(2) = Et a mixture of alkyne complex (13A) and minor allene (13) is obtained. Crystal structures of 4, 6, 7 and 11 have been determined; the latter structure proved the back-bonding interaction of the allene terminal double bond. Only the synthesis of 8 from 1 was inefficient because the equilibrium constant for the reaction [1] + [Me3SiC≡CSiMe3] ⇌ [8] + [C2H4] approached 1. Compound 9 (R(1), R(2): Me), not obtainable from 1, together with compounds 3–6 and 10 (R(1), R(2): Et) were also prepared by alkyne exchange with 8, however this reaction did not take place in attempts to obtain 7. Compounds 1 and 3–9 display the longest-wavelength electronic absorption band in the range 670-940 nm due to the HOMO → LUMO transition. The assignment of the first excitation to be of predominantly a b2 → a1 transition was confirmed by DFT calculations. The calculated first excitation energies for 3–9 followed the order of hypsochromic shifts of the absorption band relative to 8 that were induced by acetylene substituents: Me > Ph ≫ SiMe3. Computational results have also affirmed the back-bonding nature in the alkyne-to-metal coordination.

  4. Studies of a series of [Ni(P(R)2N(Ph)2)2(CH3CN)]2+ complexes as electrocatalysts for H2 production: substituent variation at the phosphorus atom of the P2N2 ligand.

    Science.gov (United States)

    Kilgore, Uriah J; Stewart, Michael P; Helm, Monte L; Dougherty, William G; Kassel, W Scott; DuBois, Mary Rakowski; DuBois, Daniel L; Bullock, R Morris

    2011-11-07

    A series of [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes containing the cyclic diphosphine ligands [P(R)(2)N(Ph)(2) = 1,5-diaza-3,7-diphosphacyclooctane; R = benzyl (Bn), n-butyl (n-Bu), 2-phenylethyl (PE), 2,4,4-trimethylpentyl (TP), and cyclohexyl (Cy)] have been synthesized and characterized. X-ray diffraction studies reveal that the cations of [Ni(P(Bn)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) and [Ni(P(n-Bu)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) have distorted trigonal bipyramidal geometries. The Ni(0) complex [Ni(P(Bn)(2)N(Ph)(2))(2)] was also synthesized and characterized by X-ray diffraction studies and shown to have a distorted tetrahedral structure. These complexes, with the exception of [Ni(P(Cy)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2), all exhibit reversible electron transfer processes for both the Ni(II/I) and Ni(I/0) couples and are electrocatalysts for the production of H(2) in acidic acetonitrile solutions. The heterolytic cleavage of H(2) by [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes in the presence of p-anisidine or p-bromoaniline was used to determine the hydride donor abilities of the corresponding [HNi(P(R)(2)N(Ph)(2))(2)](BF(4)) complexes. However, for the catalysts with the most bulky R groups, the turnover frequencies do not parallel the driving force for elimination of H(2), suggesting that steric interactions between the alkyl substituents on phosphorus and the nitrogen atom of the pendant amines play an important role in determining the overall catalytic rate. © 2011 American Chemical Society

  5. Understanding effects of chemical structure on azo dye decolorization characteristics by Aeromonas hydrophila

    Energy Technology Data Exchange (ETDEWEB)

    Hsueh, Chung-Chuan [Department of Chemical and Materials Engineering, National I-Lan University, I-Lan 260, Taiwan (China); Chen, Bor-Yann, E-mail: bychen@niu.edu.tw [Department of Chemical and Materials Engineering, National I-Lan University, I-Lan 260, Taiwan (China); Yen, Chia-Yi [Department of Chemical and Materials Engineering, National I-Lan University, I-Lan 260, Taiwan (China)

    2009-08-15

    This novel comparative study tended to disclose how the molecular structures present in seven azo dyes including two types of azo dyes (i.e., naphthol type azo dyes - Reactive Black 5 (RB 5), Reactive Blue 171 (RB 171), Reactive Green 19 (RG19), Reactive Red 198 (RR198), Reactive Red 141 (RR141) and non-naphthol type azo dyes - Direct Yellow 86 (DY86), Reactive Yellow 84 (RY84)) affected color removal capability of Aeromonas hydrophila. Generally speaking, the decolorization rate of naphthol type azo dye with hydroxyl group at ortho to azo bond was faster than that of non-naphthol type azo dye without hydroxyl group, except of RG19. The azo dyes with electron-withdrawing groups (e.g., sulfo group in RR198, RB5 and RR141) would be easier to be decolorized than the azo dyes with the electron-releasing groups (e.g., -NH-triazine in RB171 and RG19). In addition, the azo dyes containing more electron-withdrawing groups (e.g., RR198, RB5 and RR141) showed significantly faster rate of decolorization. The azo dyes with electron-withdrawing groups (e.g., sulfo group) at para and ortho to azo bond (e.g., RR198, RB5 and RR141) could be more preferred for color removal than those at meta (e.g., DY86 and RY84). The former azo dyes with para and ortho sulfo group provided more effective resonance effects to withdraw electrons from azo bond, causing azo dyes to be highly electrophilic for faster rates of reductive biodecolorization. However, since the ortho substituent caused steric hindrance near azo linkage(s), azo dyes with para substituent could be more favorable (e.g., SO{sub 2}(CH{sub 2}){sub 2}SO{sub 4}{sup -} in RR198 and RB5) than those with ortho substituent (e.g., sulfo group at RR141) for decolorization. Thus, the ranking of the position for the electron-withdrawing substituent in azo dyes to escalate decolorization was para > ortho > meta. This study suggested that both the positions of substituents on the aromatic ring and the electronic characteristics of

  6. Gene expression of endothelin receptors in replaced rheumatic mitral stenotic valves Expressão gênica de receptores de endotelina em valvas mitrais reumáticas estenóticas substituídas

    Directory of Open Access Journals (Sweden)

    Sydney Correia Leão

    2012-12-01

    Full Text Available OBJECTIVES: Rheumatic fever is a highly prevalent disease in Brazil, and it poses a major public health problem. It is the leading cause of acquired heart disease in childhood and adolescence. The aim of this study was to evaluate the gene expression of ET-3 and its receptors, in replaced rheumatic mitral valves. METHODS: We studied the gene expression of endothelin-3 (ET-3 and its receptors, endothelin receptor A and endothelin receptor B (ETr-A and ETr-B, in the rheumatic mitral valves of 17 patients who underwent valve replacement surgery. The samples also underwent a histological analysis. RESULTS: Our data showed that almost all patients, regardless of individual characteristics such as gender or age, expressed the endothelin receptor genes, but did not express the genes for ET-3. In quantitative analysis, the ETr-A/GAPDH mean ratio was 33.04 ± 18.09%; while the ETr-B/GAPDH mean ratio was 114.58 ± 42.30%. Regarding histopathological individual features, the frequency of fibrosis is 100%, 88.23% of mononuclear infiltrate, 52.94% of neovascularization, 58.82% of calcification and absence of ossification. CONCLUSION: The presence of receptors ETr-A and ETr-B in rheumatic mitral valves suggests its interaction with the system of circulating endothelins, particularly ETr-B (known for acting in the removal of excess endothelin detected in a greater proportion, which could explain the lack of expression of endothelin in rheumatic mitral valve, process to be elucidated.OBJETIVOS: A febre reumática é uma doença altamente prevalente no Brasil, e representa um importante problema de saúde pública. É a principal causa de cardiopatia adquirida na infância e adolescência. O objetivo deste estudo foi avaliar a expressão gênica de ET-3 e seus receptores, em valvas mitrais reumáticas substituídas. Métodos: Estudamos a expressão gênica de endotelina-3 (ET-3 e de seus receptores, receptor da endotelina A e receptor da endotelina B (ETr-A e

  7. Tuning and Quantifying Steric and Electronic Effects of N-Heterocyclic Carbenes

    KAUST Repository

    Falivene, Laura

    2014-07-12

    This chapter states that the main handles for tuning steric and electronic effects are the substituents on N atoms, the nature of the C4-C5 bridge (either saturated or unsaturated), and the substituents on the C4 and C5 atoms. The initial intuition that steric properties of N-heterocyclic carbenes (NHCs) could be modulated and could impact catalytic behavior stimulated the development of steric descriptors to quantify the steric requirement of different NHCs and, possibly, to compare them with tertiary phosphines. NHCs can be classified as typically strong σ-basic/π-acid ligands, although they have been also shown to exhibit reasonable π-basic properties. This electronic modularity allows NHC ligands to adapt flexibly to different chemical environments represented by a transition metal and the other ligands. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA. All rights reserved.

  8. Substituent effects on an inverse electron demand hetero Diels-Alder reaction in aqueous solution and organic solvents : Cycloaddition of substituted styrenes to di(2-pyridyl)-1,2,4,5-tetrazine

    NARCIS (Netherlands)

    Wijnen, Jan W.; Zavarise, Silvia; Engberts, Jan B.F.N.; Charton, Marvin

    1996-01-01

    The kinetics of the Diels-Alder reactions of di(2-pyridyl)-1,2,4,5-tetrazine (1) with substituted styrenes 2 was investigated in aqueous media and in organic solvents. The second-order rate constants ofthis reaction increase dramatically in water-rich media. A decrease in pH accelerates the aqueous

  9. SUBSTITUENT EFFECTS OF LIGANDS ON ASYMMETRIC INDUCTION IN A PROTOTYPICAL PALLADIUM-CATALYZED ALLYLATION REACTION: MAKING BOTH ENANTIOMERS OF A PRODUCT IN HIGH OPTICAL PURITY USING THE SAME SOURCE OF CHIRALITY. (R826120)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  10. Keto - enol, imine - enamine, and nitro - aci-nitro tautomerism and their interrelationship in substituted nitroethylenes. Keto, imine, nitro, and vinyl substituent effects, and the importance of H-bonding

    NARCIS (Netherlands)

    Lammertsma, K.; Bharatam, P.V.

    2000-01-01

    Tautomeric isomers and conformers of 2-nitrovinyl alcohol (1), 2-nitrovinylamine (2), and 1-nitropropene (3) are reported at the MP2 and B3LYP levels of theory, using the 6-31G* basis set, with energy evaluation at B3LYP/6-311+G** and G2MP2. The nitroalkenes are the global minima on their respective

  11. Semiconducting alkyl derivatives of 2,5-bis(2,2'-bithiophene-5-yl)-1,3,4-thiadiazole-effect of the substituent position on the spectroscopic, electrochemical, and structural properties

    Czech Academy of Sciences Publication Activity Database

    Kurach, E.; Kotwica, K.; Zapala, J.; Knor, M.; Nowakowski, R.; Djurado, D.; Toman, Petr; Pfleger, Jiří; Zagorska, M.; Pron, A.

    2013-01-01

    Roč. 117, č. 29 (2013), s. 15316-15326 ISSN 1932-7447 R&D Projects: GA ČR(CZ) GAP205/10/2280; GA MŠk 7E10040 EU Projects: European Commission(XE) 247745 - FlexNet Institutional support: RVO:61389013 Keywords : thiadiazole * density functional theory * absorption spectra Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.835, year: 2013

  12. Transmission of Electronic Substituent Effects across the 1,12-Dicarba-doso-dodecaborane Cage: A Computational Study Based on Structural Variation, Atomic Charges, and C-13 NMR Chemical Shifts

    Czech Academy of Sciences Publication Activity Database

    Campanelli, A.R.; Domenicano, A.; Hnyk, Drahomír

    2015-01-01

    Roč. 119, č. 1 (2015), s. 205-214 ISSN 1089-5639 R&D Projects: GA ČR GAP208/10/2269 Institutional support: RVO:61388980 Keywords : MONOSUBSTITUTED BENZENE RINGS * 4-SUBSTITUTED BIPHENYLS * 3-DIMENSIONAL AROMATICITY * CARBORANES * DERIVATIVES Subject RIV: CA - Inorganic Chemistry Impact factor: 2.883, year: 2015

  13. Effects of solvent and structure on the reactivity of 6-substituted nicotinic acids with diazodiphenylmethane in aprotic solvents

    Directory of Open Access Journals (Sweden)

    BRATISLAV Ž. JOVANOVIĆ

    2009-12-01

    Full Text Available The rate constants for the reactions of diazodiphenylmethane (DDM with 6-substituted nicotinic acids in aprotic solvents at 30 °C were determined. The obtained second order rate constants in aprotic solvents, together with literature data for benzoic and nicotinic acids in protic solvents, were used for the calculation of solvent effects, employing the Kamlet-Taft solvatochromic equation (linear solvation energy relationship – LSER in the form: log k = log k0 + s* + a + b. The correlations of the kinetic data were performed by means of multiple linear regression analysis taking appropriate solvent parameters. The sign of the equation coefficients (s, a and b were in agreement with the postulated reaction mechanism, and the mode of the solvent influences on the reaction rate is discussed based on the correlation results. A similar contribution of the non-specific solvent effect and electrophilic solvation was observed for all acids, while the highest contribution of nucleophilic solvation was influenced by their high acidity. Correlation analysis of the rate data with substituent p parameters in an appropriate solvent using the Hammett equation was also performed. The substituent effect on the acid reactivity was higher in aprotic solvents of higher dipolarity/polarizability. The mode of the transmission of the substituent effect is discussed in light of the contribution of solute–solvent interaction on the acid reactivity.

  14. A nuclear magnetic resonance study of conformational transmission in phosphorylated pyranosides

    International Nuclear Information System (INIS)

    Vries, N.K. de.

    1987-01-01

    This thesis describes an experimental NMR study, combined with MNDO calculations, on the conformational preferences of the exocyclic bond of 6-phosphorylated pyranosides and tetrahydropyran-2-methyl compounds. The various factors influencing the rotamer population distribution around this O-C-C-O fragment, e.g. solvent polarity, stereoelectronic effects and coordination of phosphorus, are analysed. 150 refs.; 25 figs.; 16 tabs

  15. Edge-on gating effect in molecular wires.

    Science.gov (United States)

    Lo, Wai-Yip; Bi, Wuguo; Li, Lianwei; Jung, In Hwan; Yu, Luping

    2015-02-11

    This work demonstrates edge-on chemical gating effect in molecular wires utilizing the pyridinoparacyclophane (PC) moiety as the gate. Different substituents with varied electronic demands are attached to the gate to simulate the effect of varying gating voltages similar to that in field-effect transistor (FET). It was observed that the orbital energy level and charge carrier's tunneling barriers can be tuned by changing the gating group from strong electron acceptors to strong electron donors. The single molecule conductance and current-voltage characteristics of this molecular system are truly similar to those expected for an actual single molecular transistor.

  16. Isotope effects on chemical equilibria

    International Nuclear Information System (INIS)

    Golding, P.D.

    1974-01-01

    The thermodynamic equilibrium constants of three deuterated substituted acetic acids are reported. The calculation of secondary isotope effects of the second kind for the three isotopic acid pairs has been accomplished by the appropriate comparison of thermodynamic equilibrium constants, and by the comparison of isotopic slopes. The effect of substituent variation on the isotope effects reported here disqualifies the simple inductive model as a legitimate description of secondary isotope effects of the second kind. The correlation of diminishing isotope effect per deuterium atom with increasing acidity is also invalidated by the present results. The syntheses of 9-thia-9,10-dihydrophenanthrene-9-oxide and thioxanthene-10-oxide are described. These compounds have been partially deuterated at their respective methylene positions. Spectral evidence indicates stereoselectivity of the methylene protons in the exchange reactions of both compounds. (author)

  17. Steric effects in release of amides from linkers in solid-phase synthesis. Molecular mechanics modeling of key step in peptide and combinatorial chemistry

    DEFF Research Database (Denmark)

    Norrby, Per-Ola; Jensen, Knud Jørgen

    2006-01-01

    Acidolytic release of an amide from a solid support by C-N bond cleavage is all ubiquitous and crucial step in many solid-phase syntheses. We have used molecular modeling of a pseudo-equilibrium to explore substituent and steric effects in the release of peptides. The high acid-lability of the ba......Acidolytic release of an amide from a solid support by C-N bond cleavage is all ubiquitous and crucial step in many solid-phase syntheses. We have used molecular modeling of a pseudo-equilibrium to explore substituent and steric effects in the release of peptides. The high acid......-lability of the backbone amide linkage (BAL), which releases sec. amides, compared to C-terminal amide anchoring, which releases primary amides, was rationalized by steric relief upon cleavage. Thus, the relative stability of the carbenium ion formed from the linker in the acidolytic release is an insufficient measure...

  18. Saturated amine oxides: Part 8. Hydroacridines: Part 27. Effects of N-oxidation and of N-quaternization on the 15N NMR chemical shifts of N-methylpiperidine-derived mono-, bi-, and tricycloaliphatic tertiary amines.

    Science.gov (United States)

    Potmischil, Francisc; Duddeck, Helmut; Nicolescu, Alina; Deleanu, Calin

    2007-03-01

    The (15)N chemical shifts of 13 N-methylpiperidine-derived mono-, bi- and tricycloaliphatic tertiary amines, their methiodides and their N-epimeric pairs of N-oxides were measured, and the contributions of specific structural parameters to the chemical shifts were determined by multilinear regression analysis. Within the examined compounds, the effects of N-oxidation upon the (15)N chemical shifts of the amines vary from +56 ppm to +90 ppm (deshielding), of which approx. +67.7 ppm is due to the inductive effect of the incoming N(+)--O(-) oxygen atom, whereas the rest is due to the additive shift effects of the various C-alkyl substituents of the piperidine ring. The effects of quaternization vary from -3.1 ppm to +29.3 ppm, of which approx. +8.9 ppm is due to the inductive effect of the incoming N(+)--CH(3) methyl group, and the rest is due to the additive shift effects of the various C-alkyl substituents of the piperidine ring. The shift effects of the C-alkyl substituents in the amines, the N-oxides and the methiodides are discussed. Copyright (c) 2007 John Wiley & Sons, Ltd.

  19. Spin-selective depopulation of triplet sublevels in rapidly rotating triplet exciplexes detected by a heavy-atom-induced magnetic field effect

    OpenAIRE

    Steiner, Ulrich

    1980-01-01

    A mechanism is presented explaining a reported heavy-atom-induced magnetic field effect as a consequence of non-equilibrium triplet sublevel population in an intermediate exciplex. The triplet exciplex spin polarization is induced by sub-level-selective intersystem crossing from the exciplex triplet to its singlet ground state and is decreased by an external magnetic field. The theory accounts almost quantitatively for the observed influence of magnetic field strength and heavy-atom substitue...

  20. Suppressing effects of glucan on micronuclei induced by Co60 in mice

    International Nuclear Information System (INIS)

    Chorvatovicova, D.

    1991-01-01

    The effects of glucan on the frequency of micronuclei in polychromatic erythrocytes of A/Ph mouse bone marrow induced by Co 60 irradiation were examined. Suppressing effect of three glucan derivatives was statistically significant (P 3 substituent (DS 0.89). Intraperitoneal application of glucan has to be done earlier than one hour after irradiation. The suppressive effects of glucans can be explained by their ability to trap OH radicals and so decrease the clastogenic effect of irradiation. The results may be useful for therapeutic application of glucan with radiation therapy. (orig.) [de

  1. On the nature of the electronic effect of multiple hydroxyl groups in the 6-membered ring - the effects are additive but steric hindrance plays a role too

    DEFF Research Database (Denmark)

    Pedersen, Christian Marcus; Bols, Mikael

    2017-01-01

    Research during the last two decades has shown a remarkable directional component of the substituent effects of hydroxy groups, which has a profound effect on the properties of hydroxylated compounds such as carbohydrates. While the epimerisation of a single hydroxyl function is well studied...... synthesized and their pKa and conformation were studied. The results show that the large difference in the electronic effect between the axial and equatorial hydroxyls is partially cancelled by counteracting steric hindrance from 1,3-diaxial interactions. Hydrogen bonding does not appear to play any role...

  2. Exploratory conformational study of (+)-catechin. Modeling of the polarizability and electric dipole moment.

    Science.gov (United States)

    Bentz, Erika N; Pomilio, Alicia B; Lobayan, Rosana M

    2014-12-01

    The extension of the study of the conformational space of the structure of (+)-catechin at the B3LYP/6-31G(d,p) level of theory is presented in this paper. (+)-Catechin belongs to the family of the flavan-3-ols, which is one of the five largest phenolic groups widely distributed in nature, and whose biological activity and pharmaceutical utility are related to the antioxidant activity due to their ability to scavenge free radicals. The effects of free rotation around all C-O bonds of the OH substituents at different rings are taken into account, obtaining as the most stable conformer, one that had not been previously reported. One hundred seven structures, and a study of the effects of charge delocalization and stereoelectronic effects at the B3LYP/6-311++G(d,p) level are reported by natural bond orbital analysis, streamlining the order of these structures. For further analysis of the structural and molecular properties of this compound in a biological environment, the calculation of polarizabilities, and the study of the electric dipole moment are performed considering the whole conformational space described. The results are analyzed in terms of accumulated knowledge for (4α → 6″, 2α → O → 1″)-phenylflavans and (+)-catechin in previous works, enriching the study of both types of structures, and taking into account the importance of considering the whole conformational space in modeling both the polarizability and the electric dipole moment, also proposing to define a descriptive subspace of only 16 conformers.

  3. Effects of radiation on hetero-atom-containing polyacetylenes

    International Nuclear Information System (INIS)

    Yamaoka, H.; Matsuyama, T.; Masuda, T.; Higashimura, T.

    1991-01-01

    The effects of radiation on several substituted polyacetylenes containing hetero-atoms such as silicon and chlorine were studied. All the polymers containing silicon atoms degraded in the presence of air, whereas no degradation proceeded in vacuo. In the case of polymers containing chlorine atoms, degradation and crosslinking occurred simultaneously, both in air and in vacuo. The reaction mode of these polymers was found to be strongly dependent on the nature of the substituents. The relationship between the radiation sensitivity and thermal stability of substituted polyacetylenes is discussed on the basis of the obtained results. (author)

  4. A theoretical and experimental study on the molecular and electronic structures of artemisinin and related drug molecules

    International Nuclear Information System (INIS)

    Galasso, V.; Kovac, B.; Modelli, A.

    2007-01-01

    The equilibrium structures of artemisinin and a selection of its derivatives (potent antimalarial drugs) have been studied with the density functional theory ansatz B3LYP. Of the five rings of the artemisinin framework, it is only the pyranose ring B that exhibits a marked conformational flexibility, especially on addition of a pendant side chain at C-10. For the derivatives, the β isomer with the axial substituent group is found to be energetically more stable than the α isomer with the equatorial group. The assignment of the vibrational fundamentals has been supported by calculations on related model molecules and a normal coordinate analysis. This allows for a reliable characterization of the normal modes, mainly involving the peroxide linkage, in the claimed fingerprint region of 1,2,4-trioxanes. The electronic structures have also been studied by measuring and calculating significant features of the NMR, photoelectron and electron transmission spectra. In particular, a representative set of NMR chemical shifts and nuclear spin-spin coupling constants, obtained with DFT formalisms, compares favourably with experiment and fits expectation in terms of stereoelectronic effects of the vicinal oxygen lone pairs. Based on ab initio outer valence Green's function calculations, a consistent interpretation of the uppermost bands in the photoelectron spectra of artemisinin and derivatives has been advanced. The top ionization energies reflect a complex interaction of the various oxygen lone pair orbitals. Electron transmission spectroscopy is applied for the first time to compounds containing the peroxide bond and elucidates the empty level electronic structure of artemisinin and derivatives in the 0-6 eV energy range, with the support of MO calculations and comparison with the spectra of reference molecules. Electron attachment to the lowest-lying empty σ* MO, mainly localized on the O-O bridge, occurs at an energy (1.7 eV) exceptionally low for compounds not

  5. Stereochemistry of 1,2-elimination and proton-transfer reactions: toward a unified understanding.

    Science.gov (United States)

    Mohrig, Jerry R

    2013-07-16

    Many mechanistic and stereochemical studies have focused on the breaking of the C-H bond through base-catalyzed elimination reactions. When we began our research, however, chemists knew almost nothing about the stereospecificity of addition-elimination reactions involving conjugated acyclic carbonyl compounds, even though the carbonyl group is a pivotal functional group in organic chemistry. Over the last 25 years, we have studied the addition-elimination reactions of β-substituted acyclic esters, thioesters, and ketones in order to reach a comprehensive understanding of how electronic effects influence their stereochemistry. This Account brings together our understanding of the stereochemistry of 1,2-elimination and proton-transfer reactions, describing how each study has built upon previous work and contributed to our understanding of this field. When we began, chemists thought that anti stereospecificity in base-catalyzed 1,2-elimination reactions occurred via concerted E2 mechanisms, which provide a smooth path for anti elimination. Unexpectedly, we discovered that some E1cBirrev reactions produce the same anti stereospecificity as E2 reactions even though they proceed through diffusionally equilibrated, "free" enolate-anion intermediates. This result calls into question the conventional wisdom that anti stereochemistry must result from a concerted mechanism. While carrying out our research, we developed insights ranging from the role of historical contingency in the evolution of hydratase-dehydratase enzymes to the influence of buffers on the stereochemistry of H/D exchange in D2O. Negative hyperconjugation is the most important concept for understanding our results. This idea provides a unifying view for the largely anti stereochemistry in E1cBirrev elimination reactions and a basis for understanding the stereoelectronic influence of electron-withdrawing β-substituents on proton-transfer reactions.

  6. Isotope effects on nuclear shielding

    International Nuclear Information System (INIS)

    Hansen, P.E.

    1983-01-01

    This review concentrates upon empirical trends and practical uses of mostly secondary isotope effects, both of the intrinsic and equilibrium types. The text and the tables are arranged in the following fashion. The most 'popular' isotope effect is treated first, deuterium isotope effects on 13 C nuclear shielding, followed by deuterium on 1 H nuclear shieldings, etc. Focus is thus on the isotopes producing the effect rather than on the nuclei suffering the effect. After a brief treatment of each type of isotope effect, general trends are dealt with. Basic trends of intrinsic isotope effects such as additivity, solvent effects, temperature effects, steric effects, substituent effects and hyperconjugation are discussed. Uses of isotope effects for assignment purposes, in stereochemical studies, in hydrogen bonding and in isotopic tracer studies are dealt with. Kinetic studies, especially of phosphates, are frequently performed by utilizing isotope effects. In addition, equilibrium isotope effects are treated in great detail as these are felt to be new and very important and may lead to new uses of isotope effects. Techniques used to obtain isotope effects are briefly surveyed at the end of the chapter. (author)

  7. Bisacenaphthopyrazinoquinoxaline derivatives: Synthesis, physical properties and applications as semiconductors for n-channel field effect transistors

    KAUST Repository

    Tong, Chenhua

    2013-01-01

    Several bisacenaphthopyrazinoquinoxaline (BAPQ) based derivatives 1-3 were synthesized by condensation between the acenaphthenequinones and 1,2,4,5-tetraaminobenzene tetrahydrochloride. Their optical, electrochemical and self-assembling properties are tuned by different substituents. Among them, compound 3 possesses a homogeneously distributed low-lying LUMO due to the peripheral substitution with four cyano groups. The corresponding n-channel field effect transistors showed a field effect electron mobility of 5 × 10-3 cm2 V-1 s-1. © 2013 The Royal Society of Chemistry.

  8. Tuning the thermal conductance of molecular junctions with interference effects

    Science.gov (United States)

    Klöckner, J. C.; Cuevas, J. C.; Pauly, F.

    2017-12-01

    We present an ab initio study of the role of interference effects in the thermal conductance of single-molecule junctions. To be precise, using a first-principles transport method based on density functional theory, we analyze the coherent phonon transport in single-molecule junctions made of several benzene and oligo(phenylene ethynylene) derivatives. We show that the thermal conductance of these junctions can be tuned via the inclusion of substituents, which induces destructive interference effects and results in a decrease of the thermal conductance with respect to the unmodified molecules. In particular, we demonstrate that these interference effects manifest as antiresonances in the phonon transmission, whose energy positions can be tuned by varying the mass of the substituents. Our work provides clear strategies for the heat management in molecular junctions and, more generally, in nanostructured metal-organic hybrid systems, which are important to determine how these systems can function as efficient energy-conversion devices such as thermoelectric generators and refrigerators.

  9. Study of thermodynamics and electronics properties of hybrids of substituted Haucke compounds; Contribution a l'etude des proprietes thermodynamiques et electroniques d'hydrures de composes de Haucke substitues

    Energy Technology Data Exchange (ETDEWEB)

    Crivello, J.C

    2005-06-15

    This manuscript presents a combined experimental and theoretical contribution to the study of the substituted Haucke phase AB5. These compounds can reversibly absorb hydrogen under conditions of pressure and temperature satisfactory for many technological applications including hydrogen storage. The thermodynamic characterization of the solid-gas reaction was carried out for mono and poly-substituted compounds. In the respect of good conditions of growth (decomposition) of the hydride phase, we sought to determine the thermodynamic trajectories allowed during some various transformations. The experimental results showed that the rate of transformation and the hierarchy of the return-points memory are the only parameters allowing to draw a general law related to the irreversible character of hysteresis. These systems evolve in 'static' mode, independent of the time and whatever the nature of host materials. Moreover, the effect of substitution elements on electronic properties has been studied using ab initio band structure calculations for the ANi{sub 5} (A=La, Y, Ca) and LaNi{sub 5-x}M{sub x} compounds, where M is an element of the type s-p (Al, Si, Ge, Sn), of type s (Cu), or a transition metal (Mn, Fe, Co). While dissociating the structural effects, the role of the chemical interaction with hydrogen was analyzed. These results made it possible to identify the factors which control the stability of the hydrides and their maximum absorption capacity. The bulk moduli of these materials were calculated and their variation was discussed in relation to the properties of hydrogen absorption. (author)

  10. Regenerable antioxidants-introduction of chalcogen substituents into tocopherols.

    Science.gov (United States)

    Poon, Jia-Fei; Singh, Vijay P; Yan, Jiajie; Engman, Lars

    2015-02-02

    To improve the radical-trapping capacity of the natural antioxidants, alkylthio-, alkylseleno-, and alkyltelluro groups were introduced into all vacant aromatic positions in β-, γ- and δ-tocopherol. Reaction of the tocopherols with electrophilic chalcogen reagents generated by persulfate oxidation of dialkyl dichalcogenides provided convenient but low-yielding access to many sulfur and selenium derivatives, but failed in the case of tellurium. An approach based on lithiation of the appropriate bromo-tocopherol, insertion of chalcogen into the carbon-lithium bond, air-oxidation to a dichalcogenide, and final borohydride reduction/alkylation turned out to be generally applicable to the synthesis of all chalcogen derivatives. Whereas alkylthio- and alkylseleno analogues were generally poorer quenchers of lipid peroxyl radicals than the corresponding parents, all tellurium compounds showed a substantially improved radical-trapping activity. Introduction of alkyltelluro groups into the tocopherol scaffold also caused a dramatic increase in the regenerability of the antioxidant. In a two-phase lipid peroxidation system containing N-acetylcysteine as a water-soluble co-antioxidant the inhibition time was up to six-fold higher than that recorded for the natural antioxidants. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Mixed-Substituent Cyclophosphazenes with Calamitic and Polycatenar Mesogens.

    Science.gov (United States)

    Jiménez, J; Callizo, L; Serrano, J L; Barberá, J; Oriol, L

    2017-07-17

    A synthetic strategy has been developed to prepare liquid crystalline cyclotriphosphazenes that have two different types of mesogenic units linked to the same phosphorus atom. Hexachlorocyclotriphosphazene, N 3 P 3 Cl 6 , was reacted with 3 mol of the calamitic unit 4-cyano-4'-hydroxybiphenyl to give a mixture of compounds in which the nongem-trans-trisubstituted derivative N 3 P 3 Cl 3 (OC 6 H 4 C 6 H 4 {CN}-p) 3 was the major product. The substitution of all three chlorine atoms in this nongeminal compound gave rise to the hydroxyl-functional phosphazenes, nongem-trans-N 3 P 3 (OC 6 H 4 C 6 H 4 {CN}-p) 3 (OC 6 H 4 {OH}-p) 3 or nongem-trans-N 3 P 3 (OC 6 H 4 C 6 H 4 {CH 3 }-p) 3 (OC 6 H 4 {OH}-p) 3 , from which the second mesogenic unit, a polycatenar one, was introduced. The chemical structure of the resulting materials, deduced from spectroscopic and MALDI-TOF techniques, was in accordance with monodisperse, fully functionalized cyclotriphosphazenes. Mesomorphism is highly dependent on the terminal group of the calamitic units, and liquid crystal phases were only detected on the cyano-derivatives. The calamitic or columnar nature of the mesophase depends on the number of alkyl chains of the polycatenar moieties.

  12. Influence of alkene substituent in dictating the reaction course to ...

    Indian Academy of Sciences (India)

    RITABRATA DATTA

    2017-11-06

    Nov 6, 2017 ... form carbocycles or oxacycles during ring closing metathesis of ... Electronic supplementary material: The online version of this article (https:// doi.org/ ...... tific and Industrial Research for a Senior Research Fellowship.

  13. Asymmetrically substituted calix[4]pyrrole with chiral substituents

    Czech Academy of Sciences Publication Activity Database

    Štěpánek, P.; Šimák, Ondřej; Nováková, Z.; Wimmer, Zdeněk; Drašar, P.

    2011-01-01

    Roč. 9, č. 3 (2011), s. 682-683 ISSN 1477-0520 R&D Projects: GA MŠk 2B06024 Grant - others:NATO(XE) CBP.EAP.CLG.982972 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50380511 Keywords : porphyrin derivatives * anion-binding * aggregation * pyrrole * ketones Subject RIV: CC - Organic Chemistry Impact factor: 3.696, year: 2011

  14. Control of charge transfer by conformational and electronic effects: Donor-donor and donor-acceptor phenyl pyrroles

    International Nuclear Information System (INIS)

    Neubauer, Antje; Bendig, Juergen; Rettig, Wolfgang

    2009-01-01

    Derivatives of N-pyrrolobenzene with a para-donor and a para-acceptor substituent on the benzene ring are compared. It is shown that by a suitable increase of the donor strength of the pyrrolo group, CT fluorescence can be achieved even for donor-donor-substituted benzenes. The ICT emission for sterically hindered compounds is more forbidden than that of unhindered phenyl pyrroles. This suggests conformational effects which induce a narrower twist angle distribution around a perpendicular minimum in the excited state.

  15. Anti-aggregatory effect of cyclodextrins in the refolding process of recombinant growth hormones from Escherichia coli inclusion bodies

    DEFF Research Database (Denmark)

    Bajorunaite, Egle; Cirkovas, Andrejus; Radzevicius, Kostas

    2009-01-01

    Cyclodextrins with different ring size and ring substituents were tested for recombinant mink and porcine growth hormones aggregation suppression in the refolding process from Escherichia coli inclusion bodies. Methyl-β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin show a positive effect...... on the aggregation suppression of both proteins. The influence of different methyl-β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin concentrations on the renaturation yield of both growth hormones was investigated. Moreover, methyl-β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin suppress not only folding...

  16. Synthesis of 2,6-trans- and 3,3,6-trisubstituted tetrahydropyran-4-ones from Maitland-Japp derived 2H-dihydropyran-4-ones: a total synthesis of diospongin B.

    Science.gov (United States)

    Clarke, Paul A; Nasir, Nadiah Mad; Sellars, Philip B; Peter, Alejandra M; Lawson, Connor A; Burroughs, James L

    2016-07-12

    6-Substituted-2H-dihydropyran-4-one products of the Maitland-Japp reaction have been converted into tetrahydropyrans containing uncommon substitution patterns. Treatment of 6-substituted-2H-dihydropyran-4-ones with carbon nucleophiles led to the formation of tetrahydropyran rings with the 2,6-trans-stereochemical arrangement. Reaction of the same 6-substituted-2H-dihydropyran-4-ones with l-Selectride led to the formation of 3,6-disubstituted tetrahydropyran rings, while trapping of the intermediate enolate with carbon electrophiles in turn led to the formation 3,3,6-trisubstituted tetrahydropyran rings. The relative stereochemical configuration of the new substituents was controlled by the stereoelectronic preference for pseudo-axial addition of the nucleophile and trapping of the enolate from the opposite face. Application of these methods led to a synthesis of the potent anti-osteoporotic diarylheptanoid natural product diospongin B.

  17. Isotope effect of optical activity measurements on L-α-alanine

    International Nuclear Information System (INIS)

    Darge, W.; Laczko, I.; Thiemann, W.

    1976-01-01

    If an optically active organic substance is labelled in the chirality center with another isotopic species (such as 15 N for 14 N) a pronounced variation of rotatory power is predicted. It was tried to varify this idea experimentally on L-α-alanine and found an isotope effect in ORD (optical rotatory dispersion). The magnitude of the rotation is mainly dependent on the pH of the solvent. The ratio of the optical activity alanine- 14 N/alanine- 15 N is about 1.02. It can be seen that the ratios of the molecular rotations are consistently lower than the corresponding ratios of the specific rotations. This is of course due to the fact that the molecular mass 15 M is larger than 14 M. This means tthat the mass difference is already taken into account so that the ratio of the molecular rotations could be defined as the ''net'' isotope effect in the ORDs of 15 N-substitued alanine. From the fact the ORD is different for the isotope-substitued alanine, one can reasonably assume that the absorption coefficient is also different. This leads to speculations about certain problems in the chemical evolution of the biosphere, such as the origin of optical activity. (T.G.)

  18. Effect of dipole moment and conformation on the mesophase behavior of di-laterally substituted phenylazophenyl benzoate liquid crystals

    International Nuclear Information System (INIS)

    Naoum, M.M.; Ahmed, H.A.

    2011-01-01

    Highlights: → Four homologous series of di-laterally substituted derivatives were prepared. → Measurement of the dipole moment and comparing it with those calculated for the various planner conformations. → Binary phase diagrams were constructed for mixtures made from any two analogues of different central lateral substituents. → Mesophase behavior is related to conformation. → The two molecules in all mixtures investigated are arranged in a back-to-face pattern. - Abstract: The dipole moments of the previously prepared 4-(3'-fluoro phenylazo)-2-(or 3-) substituted phenyl-4''-alkoxybenzoates (In a-d ), have been determined in benzene at 30 o C. The data obtained were compared with those theoretically calculated by molecular modeling program to deduce the most probable conformations for each individual homologous series. Probable conformations deduced were found to vary according to type and position of the lateral substituent attached to the central benzene ring. The results were used to correlate the mesophase behavior, in pure and mixed derivatives, with the conformation deduced for each series. Each homologous series, that have in common a lateral fluorine atom on the first terminal ring, differs from the other by a second lateral group substituted on the central ring. The latter group varies between 2-CH 3 , 3-CH 3 , 2-Cl and 3-CN groups. Within each homologous series, the number of carbons in the other terminal alkoxy group varies between 8 and 16 carbons. The study aims to investigate the steric effect of the spatial orientation of the central lateral substituent, based on deduced conformations, on the mesomorphic properties in their pure or mixed states. The mesophase behavior was investigated via differential scanning calorimetry, DSC, and mesophases identified by polarized light microscopy, PLM.

  19. Suppressing effects of glucan on micronuclei induced by Co sup 60 in mice

    Energy Technology Data Exchange (ETDEWEB)

    Chorvatovicova, D. (Slovak Academy of Sciences, Bratislava (Czechoslovakia). Inst. of Ecobiology)

    1991-10-01

    The effects of glucan on the frequency of micronuclei in polychromatic erythrocytes of A/Ph mouse bone marrow induced by Co{sup 60} irradiation were examined. Suppressing effect of three glucan derivatives was statistically significant (P<0.01) by intravenous application of glucan one hour after irradiation. The most expressive effect was obvious by K{sub 3} substituent (DS 0.89). Intraperitoneal application of glucan has to be done earlier than one hour after irradiation. The suppressive effects of glucans can be explained by their ability to trap OH radicals and so decrease the clastogenic effect of irradiation. The results may be useful for therapeutic application of glucan with radiation therapy. (orig.).

  20. Influence of the physicochemical and aromatic properties on the chemical reactivity and its relation with carcinogenic and anticoagulant effect of 17β-aminoestrogens

    Energy Technology Data Exchange (ETDEWEB)

    Soriano-Correa, Catalina, E-mail: socc@puma2.zaragoza.unam.mx [Química Computacional, FES-Zaragoza, Universidad Nacional Autónoma de México (UNAM), Iztapalapa, Mexico City (Mexico); Raya, Angélica [Unidad Profesional Interdisciplinaria de Ingeniería Campus Guanajuato, Instituto Politécnico Nacional (IPN), Silao de la Victoria, Guanajuato (Mexico); Barrientos-Salcedo, Carolina [Laboratorio de Química Médica y Quimiogenómica, Facultad de Bioanálisis Campus Veracruz - Boca del Río, Universidad Veracruzana, Veracruz (Mexico); Esquivel, Rodolfo O. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa (UAM-Iztapalapa), Mexico City (Mexico)

    2014-06-25

    Highlights: • The aromatic A-ring of 17β-aminoestrogens contribute to its anticoagulant effect. • The electron-donor substituent groups favored the basicity of 17β-aminoestrogens. • The physicochemical properties are important in the carcinogenic effect of anticoagulant molecules. - Abstract: Activity of steroid hormones is dependent upon a number of factors, as solubility, transport and metabolism. The functional differences caused by structural modifications could exert an influence on the chemical reactivity and biological effect. The goal of this work is to study the influence of the physicochemical and aromatic properties on the chemical reactivity and its relation with the carcinogenic risk that can associate with the anticoagulant effect of 17β-aminoestrogens using quantum-chemical descriptors at the DFT-B3LYP, BH and HLYP and M06-2X levels. The relative acidity of (H1) of the hydroxyl group increases with electron-withdrawing groups. Electron-donor groups favor the basicity. The steric hindrance of the substituents decreases the aromatic character and consequently diminution the carcinogenic effect. Density descriptors: hardness, electrophilic index, atomic charges, molecular orbitals, electrostatic potential and their geometric parameters permit analyses of the chemical reactivity and physicochemical features and to identify some reactive sites of 17β-aminoestrogens.

  1. Mechanism and efficiency of cell death of type II photosensitizers: effect of zinc chelation.

    Science.gov (United States)

    Pavani, Christiane; Iamamoto, Yassuko; Baptista, Maurício S

    2012-01-01

    A series of meso-substituted tetra-cationic porphyrins, which have methyl and octyl substituents, was studied in order to understand the effect of zinc chelation and photosensitizer subcellular localization in the mechanism of cell death. Zinc chelation does not change the photophysical properties of the photosensitizers (all molecules studied are type II photosensitizers) but affects considerably the interaction of the porphyrins with membranes, reducing mitochondrial accumulation. The total amount of intracellular reactive species induced by treating cells with photosensitizer and light is similar for zinc-chelated and free-base porphyrins that have the same alkyl substituent. Zinc-chelated porphyrins, which are poorly accumulated in mitochondria, show higher efficiency of cell death with features of apoptosis (higher MTT response compared with trypan blue staining, specific acridine orange/ethidium bromide staining, loss of mitochondrial transmembrane potential, stronger cytochrome c release and larger sub-G1 cell population), whereas nonchelated porphyrins, which are considerably more concentrated in mitochondria, triggered mainly necrotic cell death. We hypothesized that zinc-chelation protects the photoinduced properties of the porphyrins in the mitochondrial environment. © 2012 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2012 The American Society of Photobiology.

  2. Substitution Effects and Linear Free Energy Relationships During Reduction of 4- Benzoyl-n-(4-substituted Benzyl)pyridinium Cations

    Science.gov (United States)

    Leventis, Nicholas; Zhang, Guo-Hui; Rawashdeh, Abdel-Monem M.; Sotiriou-Leventis, Chariklia; Gray, Hugh R. (Technical Monitor)

    2003-01-01

    In analogy to 4-(para-substituted benzoyl)-N-methylpyridinium cations (1-X's), the title species (2-X's, -X = -OCH3, -CH3, -H, -Br, -COCH3, -NO2) undergo two reversible, well-separated (E(sub 1/2) greater than or equal to 650 mV) one-electron reductions. The effect of substitution on the reduction potentials of 2-X's is much weaker than the effect of the same substituents on 1-X's: the Hammett rho-values are 0.80 and 0.93 for the 1st- and 2nd-e reduction of 2-X's vs. 2.3 and 3.3 for the same reductions of 1-X's, respectively. Importantly, the nitro group of 2-NO2 undergoes reduction before the 2nd-e reduction of the 4-benzoylpyridinium system. These results suggest that the redox potentials of the 4-benzoylpyridinium system can be course-tuned via p-benzoyl substitution and fine-tuned via para-benzyl substitution. Introducing the recently derived substituent constant of the -NO2(sup)- group (sigma para-NO2(sup)- = -0.97) yields an excellent correlation for the 3rd-e reduction of 2- NO2 (corresponding to the reduction of the carbonyl group) with the 2nd-e reduction of the other 2-X's, and confirms the electron donating properties of -NO2(sup)-.

  3. Computational insights into the photocyclization of diclofenac in solution: effects of halogen and hydrogen bonding.

    Science.gov (United States)

    Bani-Yaseen, Abdulilah Dawoud

    2016-08-21

    The effects of noncovalent interactions, namely halogen and hydrogen bonding, on the photochemical conversion of the photosensitizing drug diclofenac (DCF) in solution were investigated computationally. Both explicit and implicit solvent effects were qualitatively and quantitatively assessed employing the DFT/6-31+G(d) and SQM(PM7) levels of theory. Full geometry optimizations were performed in solution for the reactant DCF, hypothesized radical-based intermediates, and the main product at both levels of theories. Notably, in good agreement with previous experimental results concerning the intermolecular halogen bonding of DCF, the SQM(PM7) method revealed different values for d(ClO, Å) and ∠(C-ClO, °) for the two chlorine-substituents of DCF, with values of 2.63 Å/162° and 3.13 Å/142° for the trans and cis orientations, respectively. Employing the DFT/6-31+G(d) method with implicit solvent effects was not conclusive; however, explicit solvent effects confirmed the key contribution of hydrogen and halogen bonding in stabilizing/destabilizing the reactant and hypothesized intermediates. Interestingly, the obtained results revealed that a protic solvent such as water can increase the rate of photocyclization of DCF not only through hydrogen bonding effects, but also through halogen bonding. Furthermore, the atomic charges of atoms majorly involved in the photocyclization of DCF were calculated using different methods, namely Mulliken, Hirshfeld, and natural bond orbital (NBO). The obtained results revealed that in all cases there is a notable nonequivalency in the noncovalent intermolecular interactions of the two chlorine substituents of DCF and the radical intermediates with the solvent, which in turn may account for the discrepancy of their reactivity in different media. These computational results provide insight into the importance of halogen and hydrogen bonding throughout the progression of the photochemical conversion of DCF in solution.

  4. Can acyclic conformational control be achieved via a sulfur-fluorine gauche effect?

    Science.gov (United States)

    Thiehoff, C; Holland, M C; Daniliuc, C; Houk, K N; Gilmour, R

    2015-06-01

    The gauche conformation of the 1,2-difluoroethane motif is known to involve stabilising hyperconjugative interactions between donor (bonding, σ C-H ) and acceptor (antibonding, σ *C-F) orbitals. This model rationalises the generic conformational preference of F-C β -C α -X systems ( φ FCCX ≈ 60°), where X is an electron deficient substituent containing a Period 2 atom. Little is known about the corresponding Period 3 systems, such as sulfur and phosphorus, where multiple oxidation states are possible. Conformational analyses of β-fluorosulfides, -sulfoxides and -sulfones are disclosed here, thus extending the scope of the fluorine gauche effect to the 3rd Period (F-C-C-S(O) n ; φ FCCS ≈ 60°). Synergy between experiment and computation has revealed that the gauche effect is only pronounced in structures bearing an electropositive vicinal sulfur atom (S + -O - , SO 2 ).

  5. Dianthraceno[a,e]pentalenes: Synthesis, crystallographic structures and applications in organic field-effect transistors

    KAUST Repository

    Dai, Gaole

    2015-01-01

    Two soluble and stable dianthraceno[a,e]pentalenes with two (DAP1) and six (DAP2) phenyl substituents were synthesized. Both compounds possess a small energy band gap and show amphoteric redox behaviour due to intramolecular donor-accepter interactions. X-ray crystallographic analysis revealed that DAP2 has a closely packed structure with multi-dimensional [C-H⋯π] interactions although there are no π-π interactions between the dianthraceno[a,e]pentalene cores. As a result, solution-processed field effect transistors based on DAP2 exhibited an average hole mobility of 0.65 cm2 V-1 s-1. Under similar conditions, DAP1 showed an average field effect hole mobility of 0.001 cm2 V-1 s-1. This journal is

  6. Controlled Release Kinetics in Hydroxy Double Salts: Effect of Host Anion Structure

    Directory of Open Access Journals (Sweden)

    Stephen Majoni

    2014-01-01

    Full Text Available Nanodimensional layered metal hydroxides such as layered double hydroxides (LDHs and hydroxy double salts (HDSs can undergo anion exchange reactions releasing intercalated anions. Because of this, these metal hydroxides have found applications in controlled release delivery of bioactive species such as drugs and pesticides. In this work, isomers of hydroxycinnamate were used as model compounds to systematically explore the effects of anion structure on the rate and extent of anion release in HDSs. Following intercalation and subsequent release of the isomers, it has been demonstrated that the nature and position of substituent groups on intercalated anions have profound effects on the rate and extent of release. The extent of release was correlated with the magnitude of dipole moments while the rate of reaction showed strong dependence on the extent of hydrogen bonding within the layers. The orthoisomer showed a more sustained and complete release as compared to the other isomers.

  7. Synthesis of N-(β-D-glycuronopyranosyl)alkanamides and 1-(β-D-glycuronopyranosyl)-4-phenyl-[1,2,3]-triazoles as N-glycoprotein linkage region analogs: examination of the effect of C5 substituent on the N-glycosidic torsion (ΦN) based on X-ray crystallography.

    Science.gov (United States)

    Mathiselvam, Manoharan; Loganathan, Duraikkannu; Varghese, Babu

    2013-10-18

    The torsion angle around the N-glycoprotein linkage region (GlcNAc-Asn) is an important factor for presenting sugar on the cell surface which is crucial for many biological processes. Earlier studies using model and analogs showed that this important torsion angle is greatly influenced by substitutions in the sugar part. In the present work, uronic acid alkanamides and triazole derivatives have been designed and synthesized as newer analogs of N-glycoprotein linkage region to understand the influence of the carboxylic group on linkage region torsion as well as on molecular packing. Crystal structure of N-(β-D-galacturonopyranosyl)acetamide is solved with the space group of P22121. Comparison of the torsion angle and molecular packing of this compound with N-(β-D-galactopyranosyl)acetamide showed that changing the C6-hydoxymethyl group to the carboxylic acid group has minimum influence on the N-glycosidic torsion angle, ΦN and significant influence on the molecular packing. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Effects of modified β-cyclodextrin on thermal stability and conformation of lysozyme

    International Nuclear Information System (INIS)

    Kamiyama, Tadashi; Satoh, Megumi; Tateishi, Takahiro; Nojiri, Tomoaki; Takeuchi, Daisuke; Kimura, Takayoshi

    2012-01-01

    Highlights: ► Effects of cyclodextrin on stability and conformation of lysozyme were clarified. ► The CD influences the hydrophobic interaction of lysozyme by the inclusion. ► The CD relatively destabilized the folded state by stabilizing the unfolded state. ► The destabilization depends on the concentration and the substituent of CD. ► The conformation of lysozyme was more spread at unfolded state by inclusion of CD. - Abstract: Effects of cyclic oligosaccharide cyclodextrin (CD) on stability and conformation of lysozyme were clarified thermodynamically and rheologically by DSC, viscosity, and circular dichroism measurements. The modified β-CD relatively destabilized the folded state of lysozyme by stabilizing the unfolded state due to inclusion of hydrophobic part into the hydrophobic interior of CD. The order of higher destabilization effect was acetyl-β-CD > methyl-β-CD > hydroxypropyl-β-CD. Apparent number of bound CD to unfolded state for methyl-, hydroxypropyl-, and acetyl-β-CD is 6.7 ± 0.7, 4.2 ± 1.1, and 18.6 ± 4.3 and the binding constant is 5.5 ± 0.8, 6.7 ± 2.4, and 4.4 ± 1.2 L mol −1 , respectively. The viscosity for unfolded state was increased with an increase in the each modified β-CD concentration, suggesting that the inclusion of CD on a part of hydrophobic core at unfolded state leads to break the hydrophobic core, then lysozyme would be more spread structure. The substituent of CD can accelerate instability by directly breaking hydrogen bond and/or can restrain instability by increase in hydrophobic interaction. The fact that the each modified CDs has different destabilization effect shows a possibility to control the stability of protein by the substitution of CD.

  9. Constructing a mixed π-conjugated bridge to effectively enhance the nonlinear optical response in the Möbius cyclacene-based systems.

    Science.gov (United States)

    Chen, Liwei; Yu, Guangtao; Chen, Wei; Tu, Chunyun; Zhao, Xingang; Huang, Xuri

    2014-06-14

    Using density functional theory computations, employing the concept of a mixed π-conjugated bridge can effectively improve the first hyperpolarizability (β0) of Möbius cyclacene (MC)-based systems with a D-π-A framework. This mixed π-conjugated bridge is constructed by applying a -(CH=CH)x-NH2 or -(CH=CH)x-NO2 chain to modify [8]MC, which can lead to a considerable β0 value (e.g. [8]MC-(CH=CH)12-NO2 (9.87 × 10(5) au) with only a certain chain length), much larger than the sole [8]MC (261 au) and the corresponding NH2/NO2-modified polyethylene chain with the same π-conjugated length. It is revealed that the substituent sites and the chain length can play a crucial role in improving β0 values of these MC-chain systems, where the β0 value can monotonically increase with increasing -(CH=CH)x- length, and the substituent electron-withdrawing -(CH=CH)x-NO2 chain is superior to the parallel electron-donating -(CH=CH)x-NH2. These appealing findings can provide valuable insights into the design of novel NLO materials based on MC.

  10. Kinetics of cyclopropane formation by 1,3-deoxystannylation. A kinetic isotope effect as a probe for the mechanism of neighboring group participation

    International Nuclear Information System (INIS)

    McWilliam, D.C.; Balasubramanian, T.R.; Kuivila, H.G.

    1978-01-01

    1-Aryl-3-trimethylstannyl 3,5-dinitrobenzoates, Me 3 SnCH 2 CH 2 CHAr(ODNB), 4H, undergo solvolysis in 2,2,2-trifluoroethanol to form arylcyclopropanes and trimethylstannyl dinitrobenzoate. The rates for nine substituents on Ar are correlated by sigma + with a rho value of -3.63 at 100 0 C. The rates for a series of model compounds, Me 3 CCH 2 CH 2 CHAr(ODNB), 5H (six substituents), are also correlated by sigma + with a rho value of -4.90. In each case the rate for a given 4H is greater than that for the corresponding 5H. The Winstein-Grunwald m values for 4H and 5H in aqueous acetic acid at 100 0 C are 0.41 and 0.46, respectively. Measurements of the rates of solvolyses in trifluoroethanol of the 2.2-d 2 analogues of 4H and 5H revealed kinetic isotope effects of 0.94 and 1.08, respectively. These results are taken as evidence that the mechanism for the rate acceleration observed in the 4H series is due to direct participation of the C--Sn sigma electrons in the transition state of the rate-determining step of the 1,3-elimination reaction

  11. NMR Study of Solvation Effect on Geometry of Proton-Bound Homodimers of Increasing Size

    KAUST Repository

    Gurinov, Andrei A.; Denisov, Gleb S.; Borissova, Alexandra O.; Goloveshkin, Alexander S.; Greindl, Julian; Limbach, Hans-Heinrich; Shenderovich, Ilya G.

    2017-01-01

    Hydrogen bond geometries in the proton-bound homodimers of quinoline and acridine derivatives in an aprotic polar solution have been experimentally studied using 1H NMR at 120 K. The reported results show that increase of the dielec-tric permittivity of the medium results in contraction of the N…N distance. The degree of contraction depends on the homodimer's size and its substituent-specific solvation features. Neither of these effects can be reproduced using conven-tional implicit solvent models employed in computational studies. In general, the N…N distance in the homodimers of pyridine, quinoline, and acridine derivatives decreases in the sequence gas phase > solid state > polar solvent.

  12. NMR Study of Solvation Effect on Geometry of Proton-Bound Homodimers of Increasing Size

    KAUST Repository

    Gurinov, Andrei A.

    2017-10-24

    Hydrogen bond geometries in the proton-bound homodimers of quinoline and acridine derivatives in an aprotic polar solution have been experimentally studied using 1H NMR at 120 K. The reported results show that increase of the dielec-tric permittivity of the medium results in contraction of the N…N distance. The degree of contraction depends on the homodimer\\'s size and its substituent-specific solvation features. Neither of these effects can be reproduced using conven-tional implicit solvent models employed in computational studies. In general, the N…N distance in the homodimers of pyridine, quinoline, and acridine derivatives decreases in the sequence gas phase > solid state > polar solvent.

  13. Substitution effect in nuclear magnetic resonance of C-13: α methoxicyclohexanones

    International Nuclear Information System (INIS)

    Lopez Holland, M.A.G.

    1984-01-01

    Eletronic and steric interactions between the carbonyl and methoxyl groups in α-methoxicyclohexanones by H-1 and C-13 nuclear magnetic resonance spectroscopy (n.m.r) is studied. Interpretation of H-1 n.m.r measurements based on the carbonyl group anisotropy is made. The asigment of spectral lines to specific nuclear by Lanthanide Shift Reagent Experiments is confirmed. Interpretation of C-13 n.m.r. spectra with respect to molecular effects and emphirical relationships associated with the substituent was analysed. The C-13 chemical shift asignment by comparison with results of partially (SFORD) and fully decompled spectra and also by relating the measured chemical shift with values cited in the literature for similar compounds are made. A qualitative study using I.R. spectroscopy in attempt to evaluate the predominance of one the conformers of the studied compounds in solutions of n-hexan and chloroform is made. (M.J.C.) [pt

  14. Effect of methyl substitution on optoelectronic properties of 1,3,6,8-tetraphenyl pyrenes

    Directory of Open Access Journals (Sweden)

    LIU Yanling

    2014-06-01

    Full Text Available Geometric structures of the ground states and excited states,frontier molecular orbitals,ionization potentials,electron affinities,reorganization energies,and absorption and emission spectra of three novel methyl-substituted 1,3,6,8-tetra-phenylpyrenes were studied theoretically by quantum-chemical methods,such as density functional theory (DFT.The results show that the position of methyl substituent on benzene ring has much effect on the optoelectronic properties of methyl-substituted 1,3,6,8-tetra-phenylpyrenes.Interestingly,the geometric structures and optoelectronic properties of the designed compound 1,3,6,8-tetra-p-tolylpyrene (TPPy are similar to those of 1,3,6,8-tetrakis(3,5-dimethylphenylpyrene (TDMPPy,which is worthy of being further researched.

  15. Electron inductive effects in the radiolysis of substituted phenylboronic acid solutions

    International Nuclear Information System (INIS)

    Brown, B.J.; Fitch, P.G.; Sangster, D.F.

    1976-01-01

    The pulse radiolysis of aqueous solutions of phenylboronic acid PhB(OH) 2 and its m-nitro and m-amino derivatives has been investigated. The transient optical absorption spectra indicate the presence of three intermediate species absorbing with independent maxima at 297, 317 and 400 nm. The 297-nm band has been assigned to the anion formed in an electron capture reaction, i.e. PhB(OH) 2 +epsilonsub(aq) - → PhB(OH) 2 - and the 317-nm band to cyclohexadienyl radicals formed from OH and H attack on OhB(OH) 2 . Hydroxyphenylboronic acid has been identified as the major stable radiation product. For each of the systems studied the respective yield and reactivity of observed intermediate species can be interpreted relative to the inductive effects of substituent groups in agreement with the Hammett relationship. (author)

  16. Vectorization efforts to increase Gram-negative intracellular drug concentration: a case study on HldE-K inhibitors.

    Science.gov (United States)

    Atamanyuk, Dmytro; Faivre, Fabien; Oxoby, Mayalen; Ledoussal, Benoit; Drocourt, Elodie; Moreau, François; Gerusz, Vincent

    2013-03-14

    In this paper, we present different strategies to vectorize HldE kinase inhibitors with the goal to improve their gram-negative intracellular concentration. Syntheses and biological effects of siderophoric, aminoglycosidic, amphoteric, and polycationic vectors are discussed. While siderophoric and amphoteric vectorization efforts proved to be disappointing in this series, aminoglycosidic and polycationic vectors were able for the first time to achieve synergistic effects of our inhibitors with erythromycin. Although these effects proved to be nonspecific, this study provides information about the required stereoelectronic arrangement of the polycationic amines and their basicity requirements to fulfill outer membrane destabilization resulting in better erythromycin synergies.

  17. Effects of shape, size, and pyrene doping on electronic properties of graphene nanoflakes.

    Science.gov (United States)

    Kuamit, Thanawit; Ratanasak, Manussada; Rungnim, Chompoonut; Parasuk, Vudhichai

    2017-11-25

    Effects of size, shape, and pyrene doping on electronic properties of graphene nanoflakes (GNFs) were theoretically investigated using density functional theory method with PBE, B3PW91, and M06-2X functionals and cc-pVDZ basis set. Two shapes of zigzag GNFs, hexagonal (HGN) and rhomboidal (RGN), were considered. The energy band gap of GNF depends on shape and decreases with size. The HGN has larger band gap energy (1.23-3.96 eV) than the RGN (0.13-2.12 eV). The doping of pyrene and pyrene derivatives on both HGN and RGN was also studied. The adsorption energy of pyrene and pyrene derivatives on GNF does not depend on the shape of GNFs with energies between 21 and 27 kcal mol -1 . The substituent on pyrene enhances the binding to GNF but the strength does not depend on electron withdrawing or donating capability. The doping by pyrene and pyrene derivatives also shifts the HOMO and LUMO energies of GNFs. Both positive (destabilizing) and negative (stabilizing) shifts on HOMO and LUMO of GNFs were seen. The direction and magnitude of the shift do not follow the electron withdrawing and donating capability of pyrene substituents. However, only a slight shift was observed for doped RGN. A shift of 0.19 eV was noticed for HOMO of HGN doped with 1-aminopyrene (pyNH 2 ) and of 0.04 eV for LUMO of HGN doped with 1-pyrenecarboxylic acid (pyCOOH). Graphical Abstract HOMO and LUMO Energies of pyrene/pyrene derivatives doped Graphene Nanoflakes.

  18. Effect of symmetric substitution on the phenyl groups of Eu{sup 3+}-dibenzoyl methane complexes on their luminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, P. [Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Sudarsan, V.; Vatsa, R.K. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Nayak, S.K. [Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Chattopadhyay, S., E-mail: schatt@barc.gov.i [Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2010-10-15

    Complexes of Eu{sup 3+} ion and ligands like dibenzoylmethane (DBM) as well as flouro- and methoxy-substituted DBMs have been prepared and characterized. Peak maxima and line shapes of the {pi}-{pi}{sup *} transitions arising from the ligands in these complexes were very sensitive to the nature of the substituents attached to the phenyl groups of DBM. Symmetric substitution at both the phenyl groups led to improved luminescence in terms of higher quantum yields of emission and longer lifetime of the excited state ({sup 5}D{sub 0}) of Eu{sup 3+} ions. Effective averaging/cancellation of the dipole-dipole interactions in symmetrically substituted ligands and the associated decrease in the extent of quenching were responsible for the improved luminescence from such complexes.

  19. Simultaneous incorporation of carbonate and fluoride in synthetic apatites: Effect on crystallographic and physico-chemical properties.

    Science.gov (United States)

    Yao, Fang; LeGeros, John P; LeGeros, Racquel Z

    2009-07-01

    The mineral in bone is an impure hydroxyapatite, with carbonate as the chief minor substituent. Fluoride has been shown to stimulate osteoblastic activity and inhibit osteoclastic resorption in vitro. CO(3)- and F-substituted apatite (CFA) has been considered as potential bone graft material for orthopedic and dental applications. The objective of this study was to determine the effects of simultaneously incorporated CO(3) and F on the crystallographic physico-chemical properties of apatite. The results showed that increasing CO(3) and Na content in apatites with relatively constant F concentration caused a decrease in crystallite size and an increase in the extent of calcium release; increasing F content in apatites with relatively constant CO(3) concentration caused an increase in crystallite size and a decrease in the extent of Ca release. These findings suggest that CFAs as bone graft materials of desired solubility can be prepared by manipulating the relative concentrations of CO(3) and F incorporated in the apatite.

  20. The cytotoxic effect of spiroflavanone derivatives, their binding ability to human serum albumin (HSA) and a DFT study on the mechanism of their synthesis

    Science.gov (United States)

    Budzisz, Elzbieta; Paneth, Piotr; Geromino, Inacrist; Muzioł, Tadeusz; Rozalski, Marek; Krajewska, Urszula; Pipiak, Paulina; Ponczek, Michał B.; Małecka, Magdalena; Kupcewicz, Bogumiła

    2017-06-01

    This paper examines the cytotoxic effect of nine compounds with spiropyrazoline structures, and determines the reaction mechanism between diazomethane and selected benzylideneflavanones, their lipophilicity, and their binding ability to human serum albumin. The cytotoxic effect was determined on two human leukaemia cell lines (HL-60 and NALM-6) and melanoma WM-115 cells, as well as on normal human umbilical vein endothelial cells (HUVEC). The highest cytotoxicity was exhibited by compound B7: it was found to have an IC50 of less than 10 μM for all three cancer cell lines, with five to 12-fold lower sensitivity against normal cells (HUVEC). All the compounds exhibit comparable affinity energy in human serum albumin binding (from -8.1 to -8.6 kcal mol-1) but vary in their binding sites depending on the substituent. X-ray crystallography of two derivatives confirmed their synthetic pathway, and their structures were carefully examined.

  1. Free radical generation from an aniline derivative in HepG2 cells: a possible captodative effect.

    Science.gov (United States)

    Horinouchi, Yuya; Summers, Fiona A; Ehrenshaft, Marilyn; Mason, Ronald P

    2015-01-01

    Xenobiotic metabolism can induce the generation of protein radicals, which are believed to play an important role in the toxicity of chemicals and drugs. It is therefore important to identify chemical structures capable of inducing macromolecular free radical formation in living cells. In this study, we evaluated the ability of four structurally related environmental chemicals, aniline, nitrosobenzene, N,N-dimethylaniline, and N,N-dimethyl-4-nitrosoaniline (DMNA), to induce free radicals and cellular damage in the hepatoma cell line HepG2. Cytotoxicity was assessed using lactate dehydrogenase assays, and morphological changes were observed using phase contrast microscopy. Protein free radicals were detected by immuno-spin trapping using in-cell western experiments and confocal microscopy to determine the subcellular locale of free radical generation. DMNA induced free radical generation, lactate dehydrogenase release, and morphological changes in HepG2 cells, whereas aniline, nitrosobenzene, N,N-dimethylaniline did not. Confocal microscopy showed that DMNA induced free radical generation mainly in the cytosol. Preincubation of HepG2 cells with N-acetylcysteine and 2,2'-dipyridyl significantly prevented free radical generation on subsequent incubation with DMNA, whereas preincubation with apocynin and dimethyl sulfoxide had no effect. These results suggest that DMNA is metabolized to reactive free radicals capable of generating protein radicals which may play a critical role in DMNA toxicity. We propose that the captodative effect, the combined action of the electron-releasing dimethylamine substituent, and the electron-withdrawing nitroso substituent, leads to a thermodynamically stabilized radical, facilitating enhanced protein radical formation by DMNA. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. Effect of flavin compounds on uranium(VI) reduction- kinetic study using electrochemical methods with UV-vis spectroscopy

    International Nuclear Information System (INIS)

    Yamasaki, Shinya; Tanaka, Kazuya; Kozai, Naofumi; Ohnuki, Toshihiko

    2017-01-01

    The reduction of uranium hexavalent (U(VI)) to tetravalent (U(IV)) is an important reaction because of the change in its mobility in the natural environment. Although the flavin mononucleotide (FMN) has acted as an electron shuttle for the U(VI) reduction in vivo system, which is called an electron mediator, only the rate constant for the electron transfer from FMN to U(VI) has been determined. This study examined the rate constant for the U(VI) reduction process by three flavin analogues (riboflavin, flavin mononucleotide, flavin adenine dinucleotide) to elucidate their substituent group effect on the U(VI) reduction rate by electrochemical methods. The formation of the U(IV) was monitored by UV-vis spectrometry at 660 nm during the constant potential electrolysis of the U(VI) solution in the presence of the mediator. The cyclic voltammograms indicated that the three flavin analogues behaved as electron mediator to reduce U(VI). The logarithmic rate constant for the U(VI) reduction was related to the standard redox potential of the mediators. This linear relationship indicated that the redox-active group of the mediator and the substituent group of the mediator dominate capability of the U(VI) reduction and its rate, respectively. The apparent reduction potential of U(VI) increased about 0.2 V in the presence of the mediators, which strongly suggests that the biological electron mediator makes the U(VI) reduction possible even under more oxidative conditions. - Highlights: • The rate constant for the U(VI) reduction by flavin analogues was determined. • The flavins showed a mediator effect on the U(VI) reduction. • The logarithmic rate constants for the U(VI) reduction was proportional to redox potential of the mediator. • The presence of the mediator increased about 0.2 V apparent redox potential of U(VI) to U(IV).

  3. Substituent-specific antibody against glucuronoxylan reveals close association of glucuronic acid and acetyl substituents and distinct labeling patterns in tree species

    DEFF Research Database (Denmark)

    Koutaniemi, Sanna; Guillon, Fabienne; Tranquet, Olivier

    2012-01-01

    Immunolabeling can be used to locate plant cell wall carbohydrates or other components to specific cell types or to specific regions of the wall. Some antibodies against xylans exist; however, many partly react with the xylan backbone and thus provide limited information on the type of substituen...

  4. Macrocyclic ligand decorated ordered mesoporous silica with large-pore and short-channel characteristics for effective separation of lithium isotopes: synthesis, adsorptive behavior study and DFT modeling.

    Science.gov (United States)

    Liu, Yuekun; Liu, Fei; Ye, Gang; Pu, Ning; Wu, Fengcheng; Wang, Zhe; Huo, Xiaomei; Xu, Jian; Chen, Jing

    2016-10-18

    Effective separation of lithium isotopes is of strategic value which attracts growing attention worldwide. This study reports a new class of macrocyclic ligand decorated ordered mesoporous silica (OMS) with large-pore and short-channel characteristics, which holds the potential to effectively separate lithium isotopes in aqueous solutions. Initially, a series of benzo-15-crown-5 (B15C5) derivatives containing different electron-donating or -withdrawing substituents were synthesized. Extractive separation of lithium isotopes in a liquid-liquid system was comparatively studied, highlighting the effect of the substituent, solvent, counter anion and temperature. The optimal NH 2 -B15C5 ligands were then covalently anchored to a short-channel SBA-15 OMS precursor bearing alkyl halides via a post-modification protocol. Adsorptive separation of the lithium isotopes was fully investigated, combined with kinetics and thermodynamics analysis, and simulation by using classic adsorption isotherm models. The NH 2 -B15C5 ligand functionalized OMSs exhibited selectivity to lithium ions against other alkali metal ions including K(i). Additionally, a more efficient separation of lithium isotopes could be obtained at a lower temperature in systems with softer counter anions and solvents with a lower dielectric constant. The highest value separation factor (α = 1.049 ± 0.002) was obtained in CF 3 COOLi aqueous solution at 288.15 K. Moreover, theoretical computation based on the density functional theory (DFT) was performed to elucidate the complexation interactions between the macrocyclic ligands and lithium ions. A suggested mechanism involving an isotopic exchange equilibrium was proposed to describe the lithium isotope separation by the functionalized OMSs.

  5. Evaluation of sunlight induced structural changes and their effect on the photocatalytic activity of V{sub 2}O{sub 5} for the degradation of phenols

    Energy Technology Data Exchange (ETDEWEB)

    Aslam, M. [Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Ismail, Iqbal M.I. [Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Salah, Numan [Centre of Nanotechnology, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Chandrasekaran, S. [Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Qamar, M.Tariq [Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Hameed, A., E-mail: afmuhammad@kau.edu.sa [Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589 (Saudi Arabia); National Centre for Physics, Quaid-e-Azam University, Islamabad 44000 (Pakistan)

    2015-04-09

    Highlights: • The interaction of UV photons of sunlight induces defects in V{sub 2}O{sub 5}. • The photon induced defects promotes the trapping and transfer of excited electrons. • The nature of the substituent at 2-position affects the degradation process. • The formation of the intermediates is influenced by the nature of substituents. • The released ions are subjected further transformation. - Abstract: Despite knowing the fact that vanadium pentoxide is slightly soluble in aqueous medium, its photocatalytic activity was evaluated for the degradation of phenol and its derivatives (2-hydroxyphenol, 2-chlorophenol, 2-aminophenol and 2-nitrophenol) in natural sunlight exposure. The prime objective of the study was to differentiate between the homogeneous and heterogeneous photocatalysis incurred by dissolved and undissolved V{sub 2}O{sub 5} in natural sunlight exposure. V{sub 2}O{sub 5} was synthesized by chemical precipitation procedure using Triton X-100 as morphology mediator and characterized by DRS, PLS, Raman, FESEM and XRD. A lower solubility of ∼5% per 100 ml of water at 23 °C was observed after calcination at 600 °C. The study revealed no contribution of the dissolved V{sub 2}O{sub 5} in the photocatalytic process. In sunlight exposure, V{sub 2}O{sub 5} powder exhibited substantial activity for the degradation, however, a low mineralization of phenolic substrates was observed. The initial low activity of V{sub 2}O{sub 5} followed by a sharp increase both in degradation and mineralization in complete spectrum sunlight exposure, was further investigated that revealed the decrease in the bandgap and the reduction in the particle size with the interaction of UV photons (<420 nm) as this effect was not observable in the exposure of visible region of sunlight. The role of the chemically different substituents attached to an aromatic ring at 2-positions and the secondary interaction of released ions during the degradation process with the reactive

  6. Zinc Porphyrins Possessing Three p-Carboxyphenyl Groups: Effect of the Donor Strength of Push-Groups on the Efficiency of Dye Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Ram B. Ambre

    2016-06-01

    Full Text Available Zinc porphyrins decorated with three p-carboxyphenyl anchoring groups and various “push” substituents of varied electron-donating strengths were prepared in good yields by facile and straightforward ways. The effect of electron-donating strength of the donor molecules on the overall power conversion efficiency was evaluated with the help of photophysical, electrochemical, photovoltaic spectroscopy and quantum chemical calculations. It is observed from the photophysical and Infrared (IR spectroscopic data that multi-anchoring dyes are more stable and bind more strongly to the TiO2 surface than their one-anchor counterparts. The properties like a three-step synthesis, high overall yields, possible mass production on a gram-scale and strong binding affinities with TiO2 surfaces make them a suitable choice for commercial applications. Zn1NH3A, with electron donating and anti-aggregation characteristics, achieved the highest efficiency of 6.50%.

  7. Electronic and photophysical properties of 2-(2′-hydroxyphenyl)benzoxazole and its derivatives enhancing in the excited-state intramolecular proton transfer processes: A TD-DFT study on substitution effect

    Energy Technology Data Exchange (ETDEWEB)

    Daengngern, Rathawat; Kungwan, Nawee, E-mail: naweekung@gmail.com

    2015-11-15

    The effect of electron donating and withdrawing substituents on the enol absorption and keto emission spectra of 2-(2′-hydroxyphenyl)benzoxazole (HBO) and its derivatives has been systematically investigated by means of density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The enol absorption spectra of HBO were simulated by using five different DFTs with various exchange-correlation functions to validate a suitable functional prior to being further used as a method of choice to study the effect of substituents on the spectral characteristics of HBO derivatives. The popular B3LYP (Becke, three-parameter, Lee–Yang–Parr) exchange-correlation functional is found to provide the best desirable result in predicting the absorption spectrum close to experimental data. In the ground state, enol forms of HBO and its derivatives are more stable than those of keto forms, while in the first lowest excited state, keto forms are found to be more stable than their enol forms. Overall, simulated absorption and emission spectra of HBO and its derivatives from TD-B3LYP calculations are in good agreement with the experimental data. For enol, absorption maxima of HBO derivatives having electron-withdrawing groups are red-shift corresponding to their lower HOMO–LUMO energy gaps compared to that of HBO. For keto emission, HBO having electron donating groups (m-MeHBO and MHBO) and withdrawing group (CNHBO) at 4′-position on the phenol fragment as well as electron donating groups (HBOMe and HBOM) at 6-position on the benzoxazole fragment make the position of keto emission peak shift to shorter wavelength (blue-shift). However, HBO derivatives with electron withdrawing groups (HBOF, HBOCl, HBOA and HBOE) at 6-position give redshifted emission compared to the parent compound (HBO). The type of substituent on both 4′- and 6-positions certainly has a pronounced effect on the absorption and emission spectra of HBO derivatives. - Highlights: • Simulated spectra

  8. Electronic and photophysical properties of 2-(2′-hydroxyphenyl)benzoxazole and its derivatives enhancing in the excited-state intramolecular proton transfer processes: A TD-DFT study on substitution effect

    International Nuclear Information System (INIS)

    Daengngern, Rathawat; Kungwan, Nawee

    2015-01-01

    The effect of electron donating and withdrawing substituents on the enol absorption and keto emission spectra of 2-(2′-hydroxyphenyl)benzoxazole (HBO) and its derivatives has been systematically investigated by means of density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The enol absorption spectra of HBO were simulated by using five different DFTs with various exchange-correlation functions to validate a suitable functional prior to being further used as a method of choice to study the effect of substituents on the spectral characteristics of HBO derivatives. The popular B3LYP (Becke, three-parameter, Lee–Yang–Parr) exchange-correlation functional is found to provide the best desirable result in predicting the absorption spectrum close to experimental data. In the ground state, enol forms of HBO and its derivatives are more stable than those of keto forms, while in the first lowest excited state, keto forms are found to be more stable than their enol forms. Overall, simulated absorption and emission spectra of HBO and its derivatives from TD-B3LYP calculations are in good agreement with the experimental data. For enol, absorption maxima of HBO derivatives having electron-withdrawing groups are red-shift corresponding to their lower HOMO–LUMO energy gaps compared to that of HBO. For keto emission, HBO having electron donating groups (m-MeHBO and MHBO) and withdrawing group (CNHBO) at 4′-position on the phenol fragment as well as electron donating groups (HBOMe and HBOM) at 6-position on the benzoxazole fragment make the position of keto emission peak shift to shorter wavelength (blue-shift). However, HBO derivatives with electron withdrawing groups (HBOF, HBOCl, HBOA and HBOE) at 6-position give redshifted emission compared to the parent compound (HBO). The type of substituent on both 4′- and 6-positions certainly has a pronounced effect on the absorption and emission spectra of HBO derivatives. - Highlights: • Simulated spectra

  9. Synthesis and biological screening of 4-(1-pyrrolidinyl) piperidine derivatives as effective analgesics

    International Nuclear Information System (INIS)

    Saify, Z.S.; Malick, T.Z.; Mallick, T.Z.

    2014-01-01

    A variety of 4(1-pyrrolidinyl) piperidine analogs 2-6 with variable substituents on phenyl ring of phenacyl moiety were synthesized and evaluated for their analgesic inhibitory potential by tail flick method revealed significant analgesic activity. The synthetic compounds exhibit analgesic inhibitory potential was ranging from significant to highly significant activity. Compounds were evaluated by thermal stimuli (tail immersion method) at the dose of 50 mg/kg of body weight. The compounds 2-5 showed significant and highly significant analgesic activity. Pethidine was used as reference drug. Same compounds tested at the dose of 75mg/kg of body weight showed toxicity. The size of the substituent, electron donating or withdrawing affect of substituents as well as the position of substituent on phenyl ring affected the activity. These compounds could be considered to develop a new class of analgesics. (author)

  10. Solvent and electronic effects on kinetics of cyclization of thermolabile aryllithium reagents. A comparison between 1-bromo-2-(2-bromoethylbenzene and 4,5-dimethoxy-1-bromo-2-(2-bromoethylbenzene

    Directory of Open Access Journals (Sweden)

    David A. Hunt

    2009-05-01

    Full Text Available A dramatic solvent effect on the stability and kinetics of intramolecular cyclization is described for the aryllithium species generated from 2-bromo-4,5-dimethoxy-(2-bromoethylbenzene. The aryllithium generated by the halogen-metal exchange reaction with n-butyllithium, is stable for > 1h when generated at -95 to -100 oC in diethyl ether/hexane and can be trapped with electrophiles. However, when the reaction is conducted in a THF/hexane mixture, the intermediate undergoes instantaneous intramolecular cyclization to afford 4,5-dimethoxybenzocyclobutene. By comparison, the corresponding 1-lithio-2-(2-bromoethyl-benzene intermediate is stable for >1h in either THF/hexane or diethyl ether/hexane at -95 to -100 oC. These results indicate that substituent effects as well as the nature of aggregation of these intermediates play key roles in determining the reaction pathway of functionalized aryllithium intermediates when quenched with electrophiles.

  11. Ligand field effects in the nuclear magnetic shielding of nitrogen-15 and cobalt-59 in bent nitrosyl complexes of cobalt(III)

    International Nuclear Information System (INIS)

    Duffin, P.A.; Larkworthy, L.F.; Mason, J.; Stephens, A.N.; Thompson, R.M.

    1987-01-01

    A range of square-pyramidal complexes of cobalt(III) with a bent apical nitrosyl ligand has been prepared and examined by 15 N and 59 Co NMR spectroscopy, in a study of nephelauxetic and spectrochemical effects at the metal and nitrogen nuclei in the bent Co-NO chromophore. The basal ligands in this comparison include dithiocarbamate, quadridentate Schiff base or porphine, and bis-chelating diamine or oximate, so as to give S 4 , S 2 N 2 , N 4 , OONN, or ONON coordination in the plane and a range of substituents in the chelate and phenylene rings. The shielding of both cobalt and nitrogen tends to decrease with decrease in the M(d) → π*(NO) back-bonding, as indicated by the MN and NO bond distances, the MNO angle and the NO stretching frequency. The shieldings decrease from sulfur to nitrogen to oxygen coligators and also with electron withdrawal by ring substituents (and vice versa), i.e. with decrease in the ligand field splitting and in the nephelauxetism of the coligands. These parallelisms of the cobalt and nitrogen shielding accord with the orbital theory that was developed to explain the bending of the MNO ligand and influences of the metal and coligands. Significant interdependence of spectrochemical and nephelauxetic effects at cobalt and nitrogen arises from the degree of overlap and similarity in energies of the frontier orbitals for the paramagnetic circulation at nitrogen [n(N) → π* (NO)] and at cobalt (d-d). 43 references, 5 figures, 2 tables

  12. Influence of plants on the distribution and composition of PBDEs in soils of an e-waste dismantling area: Evidence of the effect of the rhizosphere and selective bioaccumulation

    International Nuclear Information System (INIS)

    Wang, Yan; Luo, Chunling; Li, Jun; Yin, Hua; Zhang, Gan

    2014-01-01

    Rhizosphere effects on the distribution of PBDEs in e-waste contaminated soils were investigated. The geometric means of the PBDEs in the rhizosphere and non-rhizosphere soils were 32.6 ng/g and 12.2 ng/g, whereas the geometric means of the PBDEs in vegetable shoots and roots were 2.15 ng/g and 3.02 ng/g, respectively. PBDEs in soil at different distances from the root surface may first rise appreciably and then decrease to a non-rhizosphere level for long-term contaminated soils. Different PBDE compositions in roots and shoots indicated that PBDEs in shoots may be mainly taken up from the air. The ratios of BDE99/100 and BDE153/154 in plants and their corresponding soils were different. The bioaccumulations of BDEs 100 and 154 were much higher than those of BDEs 99 and 153, respectively. This indicated that the bioaccumulation was selective and influenced by the substitution pattern, with ortho-substituted isomers being more prevalent than meta-substituted isomers. -- Highlights: • PBDEs in rhizosphere soils were higher than those in non-rhizosphere soils. • PBDEs in soil may first be accumulated and then reduced towards root surface. • Bioaccumulation of PBDEs is selective and influenced by substituent effect. • Bioaccumulations of BDEs 100 and 154 were much higher than BDEs 99 and 153. -- The bioaccumulation of PBDE isomers was selective and influenced by the substituent effect, with ortho-substitution being favored over meta-substitution

  13. Effects of Introducing Methoxy Groups into the Ancillary Ligands in Bis(diimine Copper(I Dyes for Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Annika Büttner

    2018-04-01

    Full Text Available A systematic investigation of four heteroleptic bis(diimine copper(I dyes in n-type Dye-Sensitized Solar Cells (DSSCs is presented. The dyes are assembled using a stepwise, on-surface assembly. The dyes contain a phosphonic acid-functionalized 2,2′-bipyridine (bpy anchoring domain (5 and ancillary bpy ligands that bear peripheral phenyl (1, 4-methoxyphenyl (2, 3,5-dimethoxyphenyl (3, or 3,4,5-trimethoxyphenyl (4 substituents. In masked DSSCs, the best overall photoconversion efficiency was obtained with the dye [Cu(5(4]+ (1.96% versus 5.79% for N719. Values of JSC for both [Cu(5(2]+ (in which the 4-MeO group is electron releasing and [Cu(5(4]+ (which combines electron-releasing and electron-withdrawing effects of the 4- and 3,5-substituents and are enhanced with respect to [Cu(5(1]+. DSSCs with [Cu(5(3]+ show the lowest JSC. Solid-state absorption spectra and external quantum efficiency spectra reveal that [Cu(5(4]+ benefits from an extended spectral range at higher energies. Values of VOC are in the order [Cu(5(4]+ > [Cu(5(1]+ > [Cu(5(2]+ > [Cu(5(3]+. Density functional theory calculations suggest that methoxyphenyl character in MOs within the HOMO manifold in [Cu(5(2]+ and [Cu(5(4]+ may contribute to the enhanced performances of these dyes with respect to [Cu(5(1]+.

  14. Solid-State Organization and Ambipolar Field-Effect Transistors of Benzothiadiazole-Cyclopentadithiophene Copolymer with Long Branched Alkyl Side Chains

    Directory of Open Access Journals (Sweden)

    Martin Baumgarten

    2013-06-01

    Full Text Available The solid-state organization of a benzothiadiazole-cyclopentadithiophene copolymer with long, branched decyl-tetradecyl side chains (CDT-BTZ-C14,10 is investigated. The C14,10 substituents are sterically demanding and increase the π-stacking distance to 0.40 nm from 0.37 nm for the same polymer with linear hexadecyls (C16. Despite the bulkiness, the C14,10 side chains tend to crystallize, leading to a small chain-to-chain distance between lamellae stacks and to a crystal-like microstructure in the thin film. Interestingly, field-effect transistors based on solution processed layers of CDT-BTZ-C14,10 show ambipolar behavior in contrast to CDT-BTZ-C16 with linear side chains, for which hole transport was previously observed. Due to the increased π-stacking distance, the mobilities are only 6 × 10−4 cm²/Vs for electrons and 6 × 10−5 cm²/Vs for holes, while CDT-BTZ-C16 leads to values up to 5.5 cm²/Vs. The ambipolarity is attributed to a lateral shift between stacked backbones provoked by the bulky C14,10 side chains. This reorganization is supposed to change the transfer integrals between the C16 and C14,10 substituted polymers. This work shows that the electronic behavior in devices of one single conjugated polymer (in this case CDT-BTZ can be controlled by the right choice of the substituents to place the backbones in the desired packing.

  15. Synthesis of specifically 15N- and 13C-labeled antitumor (2-Haloethyl)nitrosoureas. The study of their conformations in solution by nitrogen-15 and carbon-13 nuclear magnetic resonance and evidence for stereoelectronic control in their aqueous decomposition

    International Nuclear Information System (INIS)

    Lown, J.W.; Chauhan, S.M.S.

    1981-01-01

    The synthesis of certain specifically 15 N, 13 C, and 2 H isotope labeled 1-(2-chloroethyl)-3-alkyl-1-nitrosoureas (CENUs) is described. Spectroscopic examination of CENUs and their isotope-labeled counterparts by 1 H, 15 N, and 13 C NMR and infrared spectra indicates that they adopt preferred conformations in nonpolar aprotic solvents in which the NO group is aligned toward the 2-chloroethyl group. The result is in accord with the conformation of MeCCNU in the crystalline state derived from X-ray diffraction. The chemical shifts and coupling constants in the CENUs change with both solvent polarity and basicity. In aqueous phosphate buffer there is evidence for the formation of a tetrahedral intermediate, the conformation of which alters according to the reaction conditions and ultimately controls the formation of the aqueous decomposition products of CENUs. This is revealed most clearly by 13 C NMR of carbonyl- 13 C- and nitroso- 15 N-labeled BCNU and CCNU where two distinct 15 N-coupled 13 C doublets with different chemical shifts are observed. The rate of conformational change is comparable with the rate of decomposition of CENUs (via the second conformer) and may therefore represent the critical initial step of the latter process in vivo. The intermediacy of the postulated tetrahedral intermediates for CENUs is supported by observed 18 O exchange into the carbonyl group in 18 O-enriched water. Consideration of the conformations of the intermediates and of the alignment of the heteroatom lone pairs provides a satisfactory interpretation of the reactions of CENUs in aqueous solution as well as their pH dependence in terms of strict steroelectronic control and accounts for the formation of the observed products

  16. Can acyclic conformational control be achieved via a sulfur–fluorine gauche effect?† †Electronic supplementary information (ESI) available. CCDC 1048074–1048078. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc00871a

    Science.gov (United States)

    Thiehoff, C.; Holland, M. C.; Daniliuc, C.

    2015-01-01

    The gauche conformation of the 1,2-difluoroethane motif is known to involve stabilising hyperconjugative interactions between donor (bonding, σC–H) and acceptor (antibonding, σ*C–F) orbitals. This model rationalises the generic conformational preference of F–Cβ–Cα–X systems (φFCCX ≈ 60°), where X is an electron deficient substituent containing a Period 2 atom. Little is known about the corresponding Period 3 systems, such as sulfur and phosphorus, where multiple oxidation states are possible. Conformational analyses of β-fluorosulfides, -sulfoxides and -sulfones are disclosed here, thus extending the scope of the fluorine gauche effect to the 3rd Period (F–C–C–S(O)n; φFCCS ≈ 60°). Synergy between experiment and computation has revealed that the gauche effect is only pronounced in structures bearing an electropositive vicinal sulfur atom (S+–O–, SO2). PMID:29511517

  17. Molecules with linear pi-conjugated pathways between all substituents : Omniconjugation

    NARCIS (Netherlands)

    van der Veen, M.H.; Rispens, M.T; Jonkman, H.T.; Hummelen, J.C.

    In this paper, omniconjugation is introduced as a topological phenomenon in pi-conjugated systems. Omniconjugated molecules are defined by the fact that they provide direct and fully pi-conjugated pathways between all subdstituents attached to them. Surprisingly, until now such topologies have never

  18. Promotion of selective pathways in isomerizing functionalization of plant oils by rigid framework substituents

    KAUST Repository

    Christl, Josefine T.

    2014-10-14

    The 1,2-(CH2P(1-adamantyl)2)2C6H4 (dadpx) coordinated palladium complex [(dadpx)Pd(OTf)2] (1) is a catalyst precursor for the isomerizing methoxycarbonylation of the internal double bond of methyl oleate, with an unprecedented selectivity (96%) for the linear diester 1,19-dimethyl nonadecanedioate. Rapid formation of the catalytically active solvent-coordinated hydride species [(dadpx)PdH(MeOH)]+ (3-MeOH) is evidenced by NMR spectroscopy, and further isolation and X-ray crystal structure analysis of [(dadpx)PdH(PPh3)]+ (3-PPh3). DFT calculations of key steps of the catalytic cycle unravel methanolysis as the decisive step for enhanced selectivity and the influence of the rigid adamantyl framework on this step by destabilization of transition states of unselective pathways.

  19. Recommended Ideal-Gas Thermochemical Functions for Heavy Water and its Substituent Isotopologues

    Czech Academy of Sciences Publication Activity Database

    Simkó, I.; Furtenbacher, T.; Hrubý, Jan; Zobov, N. F.; Polyansky, O. L.; Tennyson, J.; Gamache, R. R.; Szidarovszky, T.; Dénes, N.; Császár, A. G.

    2017-01-01

    Roč. 46, č. 2 (2017), č. článku 023104. ISSN 0047-2689 R&D Projects: GA ČR GA16-02647S Institutional support: RVO:61388998 Keywords : heavy water * ideal-gas thermochemical functions * partition function Subject RIV: BJ - Thermodynamics OBOR OECD: Thermodynamics Impact factor: 4.204, year: 2016

  20. Influence of substituents in meso-aryl groups of iron l-oxo porphyrins\

    Czech Academy of Sciences Publication Activity Database

    Tabor, Edyta; Poltowicz, J.; Pamin, K.; Basag, S.; Kubiak, W.

    2016-01-01

    Roč. 119, NOV 2016 (2016), s. 342-349 ISSN 0277-5387 Institutional support: RVO:61388955 Keywords : iron porphyrins * μ-Oxo porphyrins * oxidation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.926, year: 2016

  1. Dinuclear ruthenium sawhorse-type complexes containing carboxylato bridges and ferrocenyl substituents: Synthesis and electrochemistry

    Czech Academy of Sciences Publication Activity Database

    Auzias, M.; Süss-Fink, G.; Štěpnička, P.; Ludvík, Jiří

    2007-01-01

    Roč. 360, č. 6 (2007), s. 2023-2028 ISSN 0020-1693 Institutional research plan: CEZ:AV0Z40400503 Keywords : carboxylato bridges * dinuclear complexes * ruthenium * electrochemistry Subject RIV: CG - Electrochemistry Impact factor: 1.713, year: 2007

  2. Novel fluorescent pH sensor based on coumarin with piperazine and imidazole substituents.

    Science.gov (United States)

    Saleh, Na'il; Al-Soud, Yaseen A; Nau, Werner M

    2008-12-01

    A new coumarin derivative containing piperazine and imidazole moieties is reported as a fluorophore for hydrogen ions sensing. The fluorescence enhancement of the studied sensor with an increase in hydrogen ions concentration is based on the hindering of photoinduced electron transfer from the piperazinyl amine and the imidazolyl amine to the coumarin fluorophore by protonation. The presented sensor has a novel design of fluorophore-spacer-receptor(1)-receptor(2) format, which is proposed to sense two ranges of pH (from 2.5 to 5.5) and (from 10 to 12) instead of sensing one pH range. A model compound, in which the piperazinyl ring is absent, was synthesized as well to confirm the novel pH sensing of the proposed sensor.

  3. Influence of the substituent on azobenzene side-chain polyester optical storage materials

    DEFF Research Database (Denmark)

    Pedersen, M; Hvilsted, Søren; Holme, NCR

    1999-01-01

    , chloro, and bromo. C-13 NMR spectroscopic and molecular mass investigations substantiate good film forming characteristics. The optical storage performance of thin polyester films are investigated through polarization holography. The resulting diffraction efficiency is mapped and discussed as a function...... of irradiation power and exposure time. Polytetradecanedioates with cyano-, nitro-, methyl-, fluoro-, or trinuoromethyl-azobenzene reach more than 50% diffraction efficiency. Investigations of anisotropy induced at different temperatures reveal that the polyesters are only photosensitive in a narrow temperature...

  4. SUBSTITUED COUMARINS Hülya Çelik Onar1*and Begüm

    African Journals Online (AJOL)

    the most widely applied for the synthesis of coumarins due to simple reaction conditions and good yields. Nowadays ... oxalic acid (10 mol%) was heated to 80 oC till completion of the reaction (monitored using. TLC). Then, the .... coumarin anticoagulants via hetero-Diels–Alder cycloaddition Tetrahedron Asymm. 2001,.

  5. Photomechanical Deformation of Azobenzene-Functionalized Polyimides Synthesized with Bulky Substituents (Postprint)

    Science.gov (United States)

    2017-12-06

    comparative UV − vis result (Figure S6, Supporting Information) that azoCBODA-BPADA has the lowest absorbance change for its azobenzene trans−cis...or trans−cis−trans reorientation processes upon irradiation of 365 nm UV or blue-green light (440−530 nm), respectively. Exposure of these materials...to UV light induces a trans−cis isomerization, resulting in a length reduction of the molecular axis of azobenzene from 9 Å (trans) to 5.5 Å (cis).10

  6. Comparison of setting time and temperature hydration in mortar with substituent ceramic

    International Nuclear Information System (INIS)

    Rodrigues, R.A.; Alves, L.S.; Evangelista, A.C.J.; Almeida, V.C.

    2011-01-01

    The workability of mortar is determined mainly by the kinetics of hydration of the hydraulic binder, the process of gelation / hydration of this material in aqueous solutions is significantly influenced by the presence of additives. As a result, this work aims at studying changes in setting time and temperature of hydration of mortars with 10, 15 and 30% of Portland cement replaced by residues of porcelain and ceramic bricks. The influence of these residues in the cement hydration process was studied by testing takes time, temperature, hydration and X-ray diffraction. The results indicate that the mortar setting time not changed significantly since the temperature of hydration has a minor variation on what is preferred because it reduces the microcracks created in mortar during drying.(author)

  7. Synthesis and optoelectronic characterization of some triphenylamine-based compounds containing strong acceptor substituents

    Energy Technology Data Exchange (ETDEWEB)

    Grigoras, Mircea, E-mail: grim@icmpp.ro; Ivan, Teofilia; Vacareanu, Loredana; Catargiu, Ana Maria; Tigoianu, Radu

    2014-09-15

    Three novel triphenylamine-based compounds containing strong electron acceptor groups have been synthesized and their comparative photophysical properties are presented. These compounds were obtained by a two-step method: (i) triphenylamine compounds with one, two and three phenylacetylene arms were synthesized by Sonogashira reaction between iodine-substituted triphenylamines and phenylacetylene, followed by (ii) post-modification of these electron-rich alkynes by addition of the strong electron acceptor, tetracyanoethylene. Characterization of all oligomers was made by FTIR, {sup 1}H-NMR, UV–vis and fluorescence spectroscopy. A batochromic shifting of the UV and photoluminescence maxima was observed with the increase of the acceptor group number. The electrochemical behavior was studied by cyclic voltammetry. The cyclic voltammograms have evidenced that triphenylamine-phenylacetylene compounds undergo only oxidation processes while compounds modified with tetracyanoethylene show both oxidation and reduction peaks associated with donor and acceptor groups, respectively. The donor–acceptor compounds coordinate metal ions (i.e., Hg{sup 2+} and Sn{sup 2+}) by cyano groups resulting in the decreasing of charge transfer band intensity, and they can be used as chemosensors. - Highlights: • Three triphenylamine-based ethynylene compounds were prepared by Sonogashira reaction. • Post-modification of ethynylene linkages by tetracyanethylene cycloaddition and retroconversion led to donor–acceptor compounds. • Photophysical properties of donor–acceptor oligomers were studied in different solvents.

  8. 1-Deoxynojirimycins with dansyl capped N-substituents as probes for Morbus Gaucher affected cell lines.

    Science.gov (United States)

    Fröhlich, Richard F G; Furneaux, Richard H; Mahuran, Don J; Rigat, Brigitte A; Stütz, Arnold E; Tropak, Michael B; Wicki, Jacqueline; Withers, Stephen G; Wrodnigg, Tanja M

    2010-07-02

    Cyclization by double reductive amination of d-xylo-hexos-5-ulose with methyl 6-aminohexanoate gave (methoxycarbonyl)pentyl-1-deoxynojirimycin. Reaction of the terminal carboxylic acid with N-dansyl-1,6-diaminohexane provided the corresponding chain-extended fluorescent derivative. By reaction with bis(6-dansylaminohexyl)amine, the corresponding branched di-N-dansyl compound was obtained. Both compounds are strong inhibitors of d-glucosidases and could also be shown to distinctly improve, at sub-inhibitory concentrations, the activity of beta-glucocerebrosidase in a Gaucher fibroblast (N370S) cell-line through chaperoning of the enzyme to the lysosome. Copyright 2010 Elsevier Ltd. All rights reserved.

  9. Structural differences of half-sandwich complexes of scandium and yttrium containing bulky substituents

    Czech Academy of Sciences Publication Activity Database

    Fridrichová, Adéla; Růžička, A.; Lamač, Martin; Horáček, Michal

    2017-01-01

    Roč. 76, FEB 2017 (2017), s. 62-66 ISSN 1387-7003 R&D Projects: GA ČR(CZ) GAP207/12/2368 Institutional support: RVO:61388955 Keywords : scandium * yttrium * half-sandwich Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 1.640, year: 2016

  10. Mechanism of the Zn(IIPhthalocyanines’ Photochemical Reactions Depending on the Number of Substituents and Geometry

    Directory of Open Access Journals (Sweden)

    Leandro Henrique Zucolotto Cocca

    2016-05-01

    Full Text Available In this work, the synthesis and the nonlinear absorption and population dynamics investigation of a series of zinc phthalocyanines (ZnPcs dissolved in chloroform are reported. In order to determine the relevant spectroscopic parameters, such as absorption cross-sections of singlet and triplet excited states, fluorescence relaxation times, intersystem crossing, radiative decay and internal conversion, different optical and spectroscopic techniques were used. By single pulse and pulse train Z-scan techniques, respectively, singlet and triplet excited states‘ absorption cross-section were determined at 532 nm. Furthermore, the intersystem crossing time was obtained by using both techniques combined with the fluorescence lifetime determined by time-resolved fluorescence. The radiative and internal conversion rates were determined from the fluorescence quantum yield of the samples. Such spectroscopy parameters are fundamental for selecting photosensitizers used in photodynamic therapy, as well as for many other applications.

  11. Synthesis and Optical Properties of Trioxatriangulenium Dyes with One and Two Peripheral Amino Substituents

    DEFF Research Database (Denmark)

    Sørensen, Thomas Just; Laursen, Bo Wegge

    2010-01-01

    -substituted triphenylmethylium (TPM) compounds by aromatic nucleophilic substitution with secondary amines and subsequent intramolecular ring closure. The optical properties of the new triangulenium dyes and their TPM precursors were investigated and compared to those of known TPM and xanthenium dyes. The optical properties...

  12. Quantitative investigations of xylose and arabinose substituents in hydroxypropylated and hydroxyvinylethylated arabinoxylans.

    Science.gov (United States)

    Lorenz, Dominic; Knöpfle, Anna; Akil, Youssef; Saake, Bodo

    2017-11-01

    The chemical structures obtained by the modification of arabinoxylans with the cyclic carbonates propylene carbonate (PC) and 4-vinyl-1,3-dioxolan-2-one (VEC) with varying degrees of substitution were investigated. Therefore, a new analytical method was developed that is based on a microwave-assisted hydrolysis of the polysaccharides with trifluoroacetic acid and the reductive amination with 2-aminobenzoic acid. The peak assignment was achieved by HPLC-MS and the carbohydrate derivatives were quantified by HPLC-fluorescence. The obtained maximum molar substitution of PC-derivatized xylan (X HP ) was 1.8; the molar substitution of VEC-derivatized xylan (X HVE ) was 2.3. Investigations of xylose and arabinose based mono- and disubstituted derivatives revealed a preferred reaction of the cyclic carbonates with arabinose. Conversion rates were up to 2.4 times higher for monosubstitution and up to 3.0 times for disubstitution compared to xylose. Furthermore, the reaction with VEC was preferred due to higher reactivity of the newly introduced side chains. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. PLE CATALYZED HYDROLYZES OF ALPHA-SUBSTITUTED ALPHA-HYDROXY ESTERS - THE INFLUENCE OF THE SUBSTITUENTS

    NARCIS (Netherlands)

    MOORLAG, H; KELLOGG, RM

    1991-01-01

    The enzymatic hydrolyses of a variety of alpha-substituted mandelic and lactic esters using pig liver esterase (PLE) have been investigated. High to moderate enantioselectivity was found for various alpha-substituted mandelic esters, whereas PLE showed low to no enantioselectivity for

  14. Synthesis and reduction of uranium(V) imido complexes with redox-active substituents

    Energy Technology Data Exchange (ETDEWEB)

    Mullane, Kimberly C.; Carroll, Patrick J.; Schelter, Eric J. [P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA (United States)

    2017-04-27

    Organic azides that contain naphthyl functional groups were used to prepare uranium(V) imido complexes U{sup V}[=NC(2-naph)Ph{sub 2}][N(SiMe{sub 3}){sub 2}]{sub 3} (2), U{sup V}[=NC(2-naph){sub 3}][N(SiMe{sub 3}){sub 2}]{sub 3} (3), and U{sup V}[=N(2-naph)][N(SiMe{sub 3}){sub 2}]{sub 3} (4), and their properties were compared with U{sup V}[=NCPh{sub 3}][N(SiMe{sub 3}){sub 2}]{sub 3} (1). The electronic structures of these compounds were investigated by solution electrochemistry studies, which revealed accessible U{sup V/VI}, U{sup IV/V}, and naphthalene{sup 0}/naphthalene{sup -1} couples. The uranium(V) naphthylimido complexes were reduced by potassium graphite to yield their uranium(IV) congeners K[U{sup IV}[=NC(2-naph)Ph{sub 2}][N(SiMe{sub 3}){sub 2}]{sub 3}] (2-K), K[U{sup IV}[=NC(2-naph){sub 3}][N(SiMe{sub 3}){sub 2}]{sub 3}] (3-K), and K[U{sup IV}[=N(2-naph)][N(SiMe{sub 3}){sub 2}]{sub 3}] (4-K). The electronic structure of the dianionic compounds were investigated by DFT calculations, and this revealed that the second reduction was ligand-based, which opens the possibility of accomplishing multi-electron redox chemistry by using a tailored multiply-bonded ligand. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Efficient Hydroformylation in Dense Carbon Dioxide using Phosphorus Ligands without Perfluoroalkyl Substituents

    NARCIS (Netherlands)

    Koeken, Ard C.J.; Benes, Nieck Edwin; van den Broeke, Leo J.P.; Keurentjes, Jos T.F.

    2009-01-01

    Rhodium catalysts modified with triphenylphosphine, triphenyl phosphite, and tris(2,4-di-tert-butylphenyl) phosphite have been evaluated for their performance in the hydroformylation of 1-octene using carbon dioxide as the solvent. It is demonstrated that these catalysts are very efficient for the

  16. Using remote substituents to control solution structure and anion binding in lanthanide complexes

    DEFF Research Database (Denmark)

    Tropiano, Manuel; Blackburn, Octavia A.; Tilney, James A.

    2013-01-01

    A study of the anion-binding properties of three structurally related lanthanide complexes, which all contain chemically identical anion-binding motifs, has revealed dramatic differences in their anion affinity. These arise as a consequence of changes in the substitution pattern on the periphery ...

  17. Multichromic Polymers Containing Alternating Bi(3-Methoxythiophene and Triphenylamine Based Units with Para-Protective Substituents

    Directory of Open Access Journals (Sweden)

    Yingfei Hou

    2016-09-01

    Full Text Available Two novel triphenylamine-based thiophene derivative monomers, 4-cyano-4′,4″-di(4-methoxythiophen-2-yltriphenylamine and 4-methoxy-4′,4″-di(4-methoxythiophen-2-yltriphenylamine, were successfully synthesized. The corresponding polymers including poly (4-cyano-4′,4″-di(4-methoxythiophen-2-yltriphenylamine and poly (4-methoxy-4′,4″-di(4-methoxythiophen-2-yltriphenylamine were electrochemically synthesized and characterized by multiple test method. The electrochemical measurements and spectroelectrochemical analyses revealed that both of the two polymers had quasi-reversible redox behavior and multi-electrochromic properties. The two polymer films showed reversible electrochemical oxidation, excellent optical contrasts in NIR region (62% at 1070 nm for the first polymer, and 86% at 1255 nm for the second polymer, satisfactory coloration efficiencies and fast switching times. The research on the application of the as prepared polymer in the fabrication of electrochromic device was also conducted, employing PCMTPA or PMMTPA as the anodically coloring materials.

  18. Role of substituents on the reactivity and electron density profile of ...

    Indian Academy of Sciences (India)

    In addition, the possible strength of interaction of these ligands ... The measure of some important electronic properties such as .... contributes to the lowering of the total binding energy ... ties like ionization energies and electron affinities, etc.

  19. <研究論文>置換基導入がアゾール型イオン液体の粘度に及ぼす影響

    OpenAIRE

    北岡, 賢; 藤本, 泰徳; 西中, 信之祐

    2014-01-01

    [Abstract] We investigated the substituent effects on the viscosity of azole based ionic liquids. Introducing some electro withdrawing groups to the azole anion and some electron donating groups to the azole cation decreased the viscosity of ionic liquids. In these substituent effects to azole anion and azole cation, the anion and cation charge are delocalized over substituent groups. The decrease in the anion and cation charge density weakens the cation-anion interaction of ionic liquids. As...

  20. Effect of chitosan ethers on fresh state properties of lime mortars

    Science.gov (United States)

    Vyšvařil, M.; Žižlavský, T.

    2017-10-01

    The fresh state properties of mortars are eminently important since determine the material workability and also have a great influence on its hardened state characteristics. In this paper, the behaviour of fresh lime mortars modified by etherified derivatives of chitosan (hydroxypropylchitosan (HPCH) and carboxymethylchitosan (CMCH)) is assessed with the purpose of exploring a new application of such derivatives as lime mortar admixtures. The rheological parameters (relative yield stress, consistency coefficient and fluidity index) and viscoelastic properties were correlated with flow table tests, relative density measurements, water retention abilities of mortars and air content in mortars. Results were seen to be strongly dependent on substituents of the chitosan. Non-ionic derivative (HPCH) had a plasticizing influence on the mortars; the ionic CMCH showed the thickening effect. The effect of chitosan ethers was found to be dosage-dependent. CMCH had low impact on water retention, while HPCH displayed high water retention capability. It was concluded, that the ionic derivative (CMCH) is very similar by its viscosity enhancing effect to starch ether.

  1. Halogenated salicylaldehyde azines: The heavy atom effect on aggregation-induced emission enhancement properties

    International Nuclear Information System (INIS)

    Chen, Xiao-tong; Tong, Ai-jun

    2014-01-01

    This study investigates the heavy-atom effect (HAE) on aggregation-induced emission enhancement (AIEE) properties of salicylaldehyde azines. For this purpose, a series of halogenated salicylaldehyde azine derivatives, namely, chloro-salicylaldehyde azine (1), bromo-salicylaldehyde azine (2) and iodo-salicylaldehyde azine (3) are synthesized. 1 and 2 display typical AIEE characteristics of salicylaldehyde azine compounds; whereas for the iodo-substituent in 3, is found to be effective “external” heavy atom quenchers to salicylaldehyde azine fluorescence in aggregated state. Based on its weak fluorescence in aggregated state and relative strong fluorescence in dispersed state, 3 can also be applied as a turn-on fluorescence probe for egg albumin detection attributed to hydrophobic interaction. -- Highlights: • This study investigates the heavy-atom effect (HAE) on aggregation-induced emission enhancement (AIEE) properties of salicylaldehyde azines. • Chloro- and bromo-salicylaldehyde display typical AIEE properties of salicylaldehyde azine, whereas the iodo-substitute quenches AIEE in aggregated state. • Iodo-salicylaldehyde can be applied as a turn-on fluorescence probe for egg albumin detection attributed to hydrophobic interaction

  2. Effects of chemical form of sodium on the product characteristics of alkali lignin pyrolysis.

    Science.gov (United States)

    Guo, Da-liang; Yuan, Hong-you; Yin, Xiu-li; Wu, Chuang-zhi; Wu, Shu-bin; Zhou, Zhao-qiu

    2014-01-01

    The effects of Na as organic bound form or as inorganic salts form on the pyrolysis products characteristics of alkali lignin were investigated by using thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG-FTIR), tube furnace and thermo-gravimetric analyzer (TGA). Results of TG-FTIR and tube furnace indicated that the two chemical forms Na reduced the releasing peak temperature of CO and phenols leading to the peak temperature of the maximum mass loss rate shifted to low temperature zone. Furthermore, organic bound Na obviously improved the elimination of alkyl substituent leading to the yields of phenol and guaiacol increased, while inorganic Na increased the elimination of phenolic hydroxyl groups promoting the formation of ethers. It was also found the two chemical forms Na had different effects on the gasification reactivity of chars. For inorganic Na, the char conversion decreased with increasing the char forming temperature, while organic bound Na was opposite. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  3. Antiproliferative and Pro-Apoptotic Effect of Novel Nitro-Substituted Hydroxynaphthanilides on Human Cancer Cell Lines

    Directory of Open Access Journals (Sweden)

    Tereza Kauerova

    2016-07-01

    Full Text Available Ring-substituted hydroxynaphthanilides are considered as cyclic analogues of salicylanilides, compounds possessing a wide range of pharmacological activities, including promising anticancer properties. The aim of this study was to evaluate the potential anticancer effect of novel nitro-substituted hydroxynaphthanilides with a special focus on structure-activity relationships. The antiproliferative effect was assessed by Water Soluble Tetrazolium Salts-1 (WST-1 assay, and cytotoxicity was evaluated via dye exclusion test. Flow cytometry was used for cell cycle analysis and detection of apoptosis using Annexin V-FITC/PI assay. Protein expression was estimated by Western blotting. Our data indicate that the potential to cause the antiproliferative effect increases with the shift of the nitro substituent from the ortho- to the para-position. The most potent compounds, 3-hydroxy-N-(3-nitrophenylnaphthalene-2-carboxamide (2, and 2-hydroxy-N-(4-nitrophenyl-naphthalene-1-carboxamide (6 showed antiproliferative activity against THP-1 and MCF-7 cancer cells without affecting the proliferation of 3T3-L1 non-tumour cells. Compounds 2 and 6 induced the accumulation of THP-1 and MCF-7 cells in G1 phase associated with the downregulation of cyclin E1 protein levels, while the levels of cyclin B1 were not affected. Moreover, compound 2 was found to exert the pro-apoptotic effect on the THP-1 cells. These results suggest that hydroxynaphthanilides might represent a potential model structure for the development of novel anticancer agents.

  4. Effects of synthetic and naturally occurring flavonoids on mitogen-induced proliferation of human peripheral-blood lymphocytes

    International Nuclear Information System (INIS)

    Hirano, Toshihiko; Oka, Kitaro; Kawashima, Etsuko; Akiba, Mitsuo

    1989-01-01

    Examination was made of the effects of 17 synthetic and naturally occurring flavonoids on human lymphocyte proliferation in the presence of concanavalin A as a mitogen. Twelve of the flavonoids examined were mono-hydroxy of methoxy derivatives. The mitogen-induced response of lymphocytes was evaluated from the extent of the incorporation of [ 3 H]thymidine into cells in vitro. All the compounds showed inhibitory effects; 4.5-77.7% of [ 3 H] thymidine incorporation was blocked by an 1.0 μg/ml concentration. The viability of lymphocytes before and after treatment, as assessed by a dye exclusion test, indicated no change, and thus the flavonoids may inhibit DNA synthesis. The flavonoids possessing 5-hydroxyl, 5-methoxyl and 6-methoxyl groups, and those with cyclohexyl instead of phenyl substituent (i.e. 2-cyclohexyl-benzopyran-4-one), showed the greatest inhibition. The inhibitory effect of any one of them was less than one half that of prednisolone, but essentially the same or somewhat exceeding that of bredinine of azathioprine. It would thus appear that the well-known anti-inflammatory effects of flavonoids may possibly arise in part from the inhibition of the proliferative response of lymphocytes

  5. The effect of the environment on the structure, quantity and composition of spruce needle wax

    International Nuclear Information System (INIS)

    Guenthardt-Goerg, M.S.

    1994-01-01

    The tubular structure (10-nonacosanol), as formed in spring on the wax surface of new spruce needles (Picea abies (L.)Karst.), or as regenerated on previous-year needles, becomes gradually fused and flattened in relation to needle exposure, particularly wind and rain. Structural flattening does not necessarily imply changes in wax quantity, composition or lead to changes in needle transpiration or photosynthesis, and was approximately reproduced by bathing excised twigs in water (with pH having little effect). In 4-year-old plants of one clone planted out at a Swiss plateau and alpine sites, changes in wax structure were similar to those found in mature trees. No such changes were found in plants with O 3 , SO 2 , ambient air, charcoal-filtered air, or in plants grown outside the chambers but shielded from rain. Area-related needle wax quantity in mature trees differed between the two sites, but did not differ in young plants under different treatments (fumigation or planted out at the sites). Minor differences in wax composition, however, were found to be related to the ozone dose of the fumigation or the ambient ozone dose at the sites. In each needle wax sample, 68 compounds grouped into 12 constituent classes were quantified. The quantity of the individual substituent classes varied among wax samples from genetically different mature trees at the two sites in a tree-specific way. Variation of these quantities was not larger than among young cloned plants after different treatments. (orig.)

  6. Effects of chemical structure on the thermodynamic efficiency of radical chain carriers for organic synthesis.

    Science.gov (United States)

    Lin, Ching Yeh; Peh, Jessie; Coote, Michelle L

    2011-03-18

    The chain carrier index (CCI), defined as the ratio of the bond dissociation free energies (BDFE) of corresponding chain carrier halides and hydrides, is proposed as a measure of the thermodynamic efficiency of chain carriers for radical dehalogenation. The larger this value is relative to the corresponding value of the organic substrate, the more thermodynamically efficient the process. The chloride and bromide CCIs were evaluated at the G3(MP2)-RAD(+) level of theory for 120 different R-groups, covering a broad range of carbon-centered and noncarbon-centered species; the effects of solvent and temperature have also been studied. The broad finding from this work is that successful chain carriers generally maximize the strength of their halide (versus hydride bonds) through charge-shift bonding. As a result, the thermodynamic efficiency of a chain carrier tends to increase down the periodic table, and also with the inclusion of stronger electron donating substituents. The CCIs of carbon-centered species fall into a relatively narrow range so that, even when the CCI is maximized through inclusion of lone pair donor OMe or NMe(2) groups, the thermodynamic driving force for dehalogenation of other organic substrates is modest at best, and the process is likely to be kinetically hampered. Among the noncarbon-centered species studied, bismuth- and borane-centered compounds have some of the highest CCI values and, although their kinetics requires further optimization, these classes of compounds would be worth further investigation as tin-free radical reducing agents.

  7. Effects of solution P H on the adsorption of aromatic compounds from aqueous solutions by activated carbon

    International Nuclear Information System (INIS)

    Nouri, S.; Haghseresht, F.; Lu, M.

    2002-01-01

    Absorption of p-Cresol, Benzoic acid and Nitro Benzene by activated carbon from dilute aqueous solutions was carried out under controlled ph conditions at 310 k. In acidic conditions, well below the pK a of all solutes, it was observed that the adsorbate solubility and the electron density of its aromatic ring were the influencing factors on the extent of the adsorption by affecting the extent of London dispersion forces. In higher solution ph conditions, on the other hand, it was found that the electrostatic forces played a significant role on the extent of adsorption. The Effect of ph must be considered from its combined effects on the carbon surface and on the solute molecules. It was found that the uptake of the molecular forms of the aromatic solutes was dependent on the substituents of the aromatic ring. Adsorption of the solutes in higher P H values was found to be dependent on the concentration of anionic form of the solutes. All isotherms were fitted into Freundlich Isotherm Equations

  8. Synergistic effect of pyrazoles derivatives and doxorubicin in claudin-low breast cancer subtype.

    Science.gov (United States)

    Saueressig, Silvia; Tessmann, Josiane; Mastelari, Rosiane; da Silva, Liziane Pereira; Buss, Julieti; Segatto, Natalia Vieira; Begnini, Karine Rech; Pacheco, Bruna; de Pereira, Cláudio Martin Pereira; Collares, Tiago; Seixas, Fabiana Kömmling

    2018-02-01

    Breast cancer is a global public health problem. For some subtypes, such as Claudin-low, the prognosis is poorer and the treatment is still a challenge. Pyrazoles are an important class of heterocyclic compounds and are promising anticancer agents based on their chemical properties. The present study was aimed not only at testing pyrazoles previously prepared by our research group in two breast cancer cell lines characterized by intermediated response to conventional chemotherapy but also at analyzing the possible synergistic effect of these pyrazoles associated with doxorubicin. Four 1-thiocarbamoyl-3,5-diaryl-4,5-dihydro-1H pyrazoles were tested for the first time in MCF-7 and MDA-MB-231 culture cells. The pyrazoles with best results in cytotoxicity were used in combination with doxorubicin and compared with this drug alone as standard. The synergic effect was analyzed using Combination Index method. In addition, cell death and apoptosis assays were carried out. Two pyrazoles with cytotoxic effect in MCF-7 and especially in MDA-MB-231 were identified. This activity was markedly higher in pyrazoles containing bromine and chlorine substituents. The combination of these pyrazoles with doxorubicin had a significant synergic effect in both cells tested and mainly in MDA-MB-231. These data were confirmed with apoptosis and cell death analysis. The synergic effect observed with combination of these pyrazoles and doxorubicin deserves special attention in Claudin-low breast cancer subtype. This should be explored in order to improve treatment results and minimize side effects. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  9. Are Effective Properties Effective?

    International Nuclear Information System (INIS)

    Han, Ru; Ingber, Marc S.; Hsiao, S.-C.

    2008-01-01

    The effective moduli (effective Young's modulus, effective Poisson's ratio, effective shear modulus, and effective bulk modulus) of dispersed-phase-reinforced composite materials are determined at the mesoscopic level using three-dimensional parallel boundary element simulations. By comparing the mesoscopic BEM results and the macroscopic results based on effective properties, limitations in the effective property approach have been examined

  10. Direct Effects of Physcion, Chrysophanol, Emodin, and Pachybasin on Germination and Appressorium Formation of the Barley ( Hordeum vulgare L.) Powdery Mildew Fungus Blumeria graminis f. sp. hordei (DC.) Speer.

    Science.gov (United States)

    Hildebrandt, Ulrich; Marsell, Alexander; Riederer, Markus

    2018-04-04

    Several anthraquinone derivatives are active components of fungicidal formulations particularly effective against powdery mildew fungi. The antimildew effect of compounds such as physcion and chrysophanol is largely attributed to host plant defense induction. However, so far a direct fungistatic/fungicidal effect of anthraquinone derivatives on powdery mildew fungi has not been unequivocally demonstrated. By applying a Formvar-based in vitro system we demonstrate a direct, dose-dependent effect of physcion, chrysophanol, emodin, and pachybasin on conidial germination and appressorium formation of Blumeria graminis f. sp. hordei (DC.) Speer, the causative agent of barley ( Hordeum vulgare L.) powdery mildew. Physcion was the most effective among the tested compounds. At higher doses, physcion mainly inhibited conidial germination. At lower rates, however, a distinct interference with appressorium formation became discernible. Physcion and others may act by modulating both the infection capacity of the powdery mildew pathogen and host plant defense. Our results suggest a specific arrangement of substituents at the anthraquinone backbone structure being crucial for the direct antimildew effect.

  11. The chemistry of cycloheptatriene part XII : the thermal behaviour of substituted cycloheptatrienes : preliminary communication

    NARCIS (Netherlands)

    Borg, ter A.P.; Razenberg, E.; Kloosterziel, H.

    1965-01-01

    cf. CA 63, 457a. The effect of substituents on 1-5 intramol. shifts of H in cycloheptatriene (I) was investigated at 100-140 Deg (CA 59, 14771b). Conversion of 7-substituted I to the 3-substituted isomer was accelerated by all of the substituents studied, including NMe2, OMe, SMe, Me, Ph, and CN,

  12. Effect of ionic strength and cationic DNA affinity binders on the DNA sequence selective alkylation of guanine N7-positions by nitrogen mustards

    International Nuclear Information System (INIS)

    Hartley, J.A.; Forrow, S.M.; Souhami, R.L.

    1990-01-01

    Large variations in alkylation intensities exist among guanines in a DNA sequence following treatment with chemotherapeutic alkylating agents such as nitrogen mustards, and the substituent attached to the reactive group can impose a distinct sequence preference for reaction. In order to understand further the structural and electrostatic factors which determine the sequence selectivity of alkylation reactions, the effect of increase ionic strength, the intercalator ethidium bromide, AT-specific minor groove binders distamycin A and netropsin, and the polyamine spermine on guanine N7-alkylation by L-phenylalanine mustard (L-Pam), uracil mustard (UM), and quinacrine mustard (QM) was investigated with a modification of the guanine-specific chemical cleavage technique for DNA sequencing. The result differed with both the nitrogen mustard and the cationic agent used. The effect, which resulted in both enhancement and suppression of alkylation sites, was most striking in the case of netropsin and distamycin A, which differed from each other. DNA footprinting indicated that selective binding to AT sequences in the minor groove of DNA can have long-range effects on the alkylation pattern of DNA in the major groove

  13. Carbon-14 kinetic isotope effects and mechanisms of addition of 2,4-dinitrobenzenesulfenyl chloride to substituted styrenes-1-14C and styrenes-2-14C

    International Nuclear Information System (INIS)

    Kanska, M.; Fry, A.

    1983-01-01

    As the first reported examples of carbon isotope effects in simple electrophilic addition reactions we have measured the carbon-14 kinetic isotope effects in the addition of 2,4-dinitrobenzenesulfenyl chloride to a series of para-substituted α and β-labeled styrenes in acetic acid at 30.1 0 C: for para substituents Cl, H, and CH 3 the k/ 14 K values for α labeling are 1.027, 1.022, and 1.004, and the k/ 14 k values for β labeling are 1.035, 1.032, and 1.037, all +/-approx.0.004. The kinetics of the reaction were measured for the p-CH 3 O,p-CH 3 , unsubstituted, p-Cl, and m-NO 2 styrenes; electron-donating groups strongly accelerate the reaction, and electron-withdrawing groups retard it. The Hammett plot is curved with p + values ranging from about -4.6 at the electron-donating group (EDG) end to about -1.8 at the electron-withdrawing group (EWG) end. Both the isotope effect and kinetic data, and related data from the literature, are interpreted in terms of a changing mechanism, with the activated complexes of the rate-determining steps having much open carbenium ion (ion pair) character for EDG-substituted styrenes and much cyclic thiiranium io (ion par) character for EWG-substituted styrenes. 1 figure, 2 tables

  14. Computational and biological evidences on the serotonergic involvement of SeTACN antidepressant-like effect in mice.

    Directory of Open Access Journals (Sweden)

    Mariana G Fronza

    Full Text Available A series of phenylselanyl-1H-1,2,3-triazole-4-carbonitriles with different substituents were screened for their binding affinity with serotonin transporter (SERT and dopamine transporter (DAT by docking molecular. 5-(4methoxyphenyl-1-(2-(phenylselanylphenyl-1H-1,2,3-triazole-4-carbonitrile (SeTACN exhibited the best conformation with SERT even higher than fluoxetine and serotonin, suggesting a competitive inhibition. SeTACN demonstrated additional affinity to other serotonergic receptors involved in antidepressant effects: 5HT1a, 5HT2a and 5HT3. In another set of experiments, SeTACN led to significant reductions in the immobility time of mice submitted to forced swimming test (FST in the dose range of 0.1- 20mg/kg, suggesting an antidepressant-like effect. The possible mechanism of action was investigated using serotonergic and dopaminergic antagonists. The antidepressant-like effect of SeTACN (0.1mg/kg i.g. was prevented by the pretreatment with WAY100635 (a selective 5HT1a antagonist, ketanserin (a 5HT2a/c antagonist and ondansetron (a selective 5ht3 antagonist, PCPA (an inhibitor of serotonin synthesis but not with SCH23390 (dopaminergic D1 antagonist and sulpiride (D2 antagonist. Sub-effective dose of fluoxetine was able to potentiate the effects of a sub-effective dose of SeTACN in FST. None of the treatments affected locomotor activity in open field test (OFT. These results together, suggest that the SeTACN antidepressant-like effect is mediate, at least in parts, by serotonergic system.

  15. Chlorine isotope effects from isotope ratio mass spectrometry suggest intramolecular C-Cl bond competition in trichloroethene (TCE) reductive dehalogenation.

    Science.gov (United States)

    Cretnik, Stefan; Bernstein, Anat; Shouakar-Stash, Orfan; Löffler, Frank; Elsner, Martin

    2014-05-20

    Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (bio)chemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE) dehalogenation was investigated. Selective biotransformation reactions (i) of tetrachloroethene (PCE) to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii) of TCE to cis-1,2-dichloroethene (cis-DCE) in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were -19.0‰ ± 0.9‰ (PCE) and -12.2‰ ± 1.0‰ (TCE) (95% confidence intervals). Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (-5.0‰ ± 0.1‰) and TCE (-3.6‰ ± 0.2‰). In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by -16.3‰ ± 1.4‰ (standard error)) than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of -2.4‰ ± 0.3‰ and the product chloride an isotope effect of -6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals). A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect). These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition). This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I) or single electron transfer as reductive dehalogenation mechanisms.

  16. Chlorine Isotope Effects from Isotope Ratio Mass Spectrometry Suggest Intramolecular C-Cl Bond Competition in Trichloroethene (TCE Reductive Dehalogenation

    Directory of Open Access Journals (Sweden)

    Stefan Cretnik

    2014-05-01

    Full Text Available Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (biochemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE dehalogenation was investigated. Selective biotransformation reactions (i of tetrachloroethene (PCE to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii of TCE to cis-1,2-dichloroethene (cis-DCE in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were −19.0‰ ± 0.9‰ (PCE and −12.2‰ ± 1.0‰ (TCE (95% confidence intervals. Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (−5.0‰ ± 0.1‰ and TCE (−3.6‰ ± 0.2‰. In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by −16.3‰ ± 1.4‰ (standard error than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of −2.4‰ ± 0.3‰ and the product chloride an isotope effect of −6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals. A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect. These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition. This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I or single electron transfer as reductive dehalogenation mechanisms.

  17. Effect of hydration on the amide I band in the binary solvents dioxane-D2O and dioxane-H2O

    International Nuclear Information System (INIS)

    Kobayashi, M.; Kobayashi, M.

    1980-01-01

    Hydration of amides in aqueous solutions has been studied by measuring the infrared spectra of amides (benzamide, p-methoxybenzamide, and ropionamide) in dioxane-D 2 O and dioxane-H 2 O mixtures. The absorption due to the C=O stretching (or amide I band) exhibited a very remarkable red shift accompanied by a characteristic change of the band shape as the water content in the medium increased. The spectral change is attributed to the change of the hydration state at the carbonyl oxygen. In the aqueous mixtures, amide molecules participate in an equilibrium among various states of hydration. The weighted mean frequency of the ν/sub C = O/ absorption, anti ν/sub C = O/, varied in proportion to the water contained in the medium. The difference between the anti ν/sub C = O/ value in pure water and that in pure dioxane,Δ anti ν, was used as a measure of the maximum degree of hydration. It was larger for propionamide than for the aromatic amides, suggesting that the steric effect of the substituents is of major importance in hydration. The isotope effect, Δ anti ν/sub D 2 O//Δ anti ν/sub H 2 O/, in the range from 1.4 to 1.6 for all cases examined, indicated that stronger hydration of amides occurred with D 2 O than with H 2 O

  18. Reductive decarboxylation of bicyclic prolinic systems: a new approach to the enantioselective synthesis of the Geissman-Waiss lactone. X-ray structure determination of a key lactone intermediate

    Directory of Open Access Journals (Sweden)

    Ambrósio João Carlos L.

    2003-01-01

    Full Text Available Two concise and enantioselective syntheses of the necine base precursors (1R,5R-N-Cbz and N-Boc-2-oxa-6-azabicyclo[3.3.0]octan-3-ones (Geissman-Waiss lactones were carried out from two enantiomerically pure endocyclic five-membered enecarbamates with overall yields of 23% and 26%, respectively. The synthetic strategy made use of a highly effective and stereoselective [2+2]cycloaddition of enantiomerically pure endocyclic enecarbamates with dichloroketene, as well as an efficient decarboxylation step of a bicyclic alpha-amino acid employing Boger's acyl selenide protocol employing tributyltin hydride. Interesting aspects concerning the regiochemical outcome of Baeyer-Villiger oxidations of bicyclic cyclobutanones are also reported, in which the usual stereoelectronic bias of Baeyer-Villiger oxidation seems to be counterbalanced by steric effects on the putative Criegee intermediate.

  19. Effect of intramolecular hydrogen bonding and electron donation on substituted anthrasemiquinone characteristics

    International Nuclear Information System (INIS)

    Pal, H.; Mukherjee, T.

    1994-01-01

    The acid-base and redox characteristics of the semiquinones of a number of hydroxy and amino-substituted anthraquinones have been investigated. Results are explained on the basis of electron-donating properties and intramolecular hydrogen bond forming capabilities of the substituents. (author). 4 refs., 1 tab., 1 fig

  20. The Conformational Behaviour of Glucosamine

    Science.gov (United States)

    Peña, Isabel; Kolesniková, Lucie; Cabezas, Carlos; Bermúdez, Celina; Berdakin, Matías; Simao, Alcides; Alonso, José L.

    2014-06-01

    A laser ablation method has been successfully used to vaporize the bioactive amino monosaccharide D-glucosamine. Three cyclic α-4C1 pyranose forms have been identified using a combination of CP-FTMW and LA-MB-FTMW spectroscopy. Stereoelectronic hyperconjugative factors, like those associated with anomeric or gauche effects, as well as the cooperative OH\\cdotsO, OH\\cdotsN and NH\\cdotsO chains, extended along the entire molecule, are the main factors driving the conformational behavior. All observed conformers exhibit a counter-clockwise arrangement (cc) of the network of intramolecular hydrogen bonds. The results are compared with those recently obtained for D-glucose. J. L. Alonso, M. A. Lozoya, I. Peña, J. C. López, C. Cabezas, S. Mata, S. Blanco, Chem. Sci. 2014, 5, 515.

  1. Acyclic diastereoselection in prochiral radical addition to prochiral olefins.

    Science.gov (United States)

    Sibi, Mukund P; Rheault, Tara R; Chandramouli, Sithamalli V; Jasperse, Craig P

    2002-03-27

    The stereochemical preference (syn or anti) when prochiral radicals add to prochiral acceptors is of fundamental interest. The primary focus of this research was to determine which factors influence the relative stereochemistry between the beta and gamma chiral centers when these are formed concurrently. While moderate diastereoselectivity was found for addition of alkyl (6a-d) and alpha-alkoxy radicals (16a-c) (15:1 anti). Steric influence in alkyl radical additions was difficult to evaluate due to decreased reactivity when using bulky reaction partners; however, more reactive alpha-alkoxy radicals, it was found that increasing steric bulk leads to moderate increases in selectivity. In addition, higher selectivity was observed when employing lanthanide Lewis acids whose environment (reactivity) was modified using achiral additives, suggesting a potentially simple means for selectivity enhancements in radical reactions. Overall these results indicate that significant stereoelectronic effects are necessary to achieve high levels of selectivity in prochiral radical additions to prochiral acceptors.

  2. Effects of solubilization of short and medium-chain molecules in the self-assembly of two amphiphilic drugs in solution

    International Nuclear Information System (INIS)

    Barbosa, Silvia; Cheema, Mohammad Arif; Siddiq, Mohammad; Taboada, Pablo; Mosquera, Victor

    2009-01-01

    The effect of short and medium chain length alcohols ethanol, propanol, and butanol on the thermodynamic properties of aqueous solutions of the ionic amphiphilic antidepressants imipramine and clomipramine hydrochlorides has been investigated at T = 293 K. Critical concentrations of the drugs were obtained from ultrasound velocity measurements. Experimental results have shown a strong dependence of the ultrasound velocity with the alcohol concentration and chain length. Differences in the aggregate properties of both amphiphiles arise from the presence of the extra Cl - substituent on the ring system of clomipramine. Density and ultrasound measurements have been used to obtain the apparent molar volumes, V φ , and isentropic apparent molar compressibilities, K φ(S) , for the aqueous drug/water-alcohol solutions. The distribution coefficient of the amount solubilized between water and the aggregates, K, has been determined using an indirect method based on the pseudo-phase model by using apparent molar volume values. This method allows the calculation of the distribution coefficients at concentrations below saturation. The standard molar Gibbs free energy change on transfer from the aqueous to the micellar, ΔG 0 , phase was calculated from the partition coefficient. The results have highlighted the structural differences between both amphiphiles

  3. Hydrogen/deuterium exchange, a unique and effective method for MS fragmentation behavior elucidation of ginkgolides and its application to systematic research in Ginkgo biloba.

    Science.gov (United States)

    Niu, Xingliang; Luo, Jun; Xu, Deran; Zou, Hongyan; Kong, Lingyi

    2017-02-05

    Ginkgolides, the main active constituents of Ginkgo biloba, possess significant selectively inhibition on platelet-activating factor and pancreatic lipase and attract wide attention in pharmacological research area. In our study, an effective hydrogen/deuterium (H/D) exchange method was developed by exchanging the α-Hs of lactone groups in ginkgolides with Ds, which was very useful for the elucidation of the fragmentation patterns of ginkgolides in Quadrupole Time-of-flight Mass Spectrometry (Q-TOF-MS), especially in accurately distinguishing the type and position of substituent in framework of ginkgolides. Then, a systematic research strategy for qualitative and quantitative analysis of ginkgolides, based on H/D exchange, tandem solid-phase extraction and LC-Q-TOF-MS, was developed, which was successfully applied in each medicinal part of G. biloba, which indicated that ginkgolide B was the most abundant ginkgolide in the seeds of G. biloba (60.6μg/g). This research was the successful application of H/D exchange in natural products, and proved that H/D exchange is a potential method for analysis research of complex TCMs active constituents. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Effect of the ultrasound-Fenton oxidation process with the addition of a chelating agent on the removal of petroleum-based contaminants from soil.

    Science.gov (United States)

    Li, Ying; Li, Fangmin; Li, Fanxiu; Yuan, Fuqian; Wei, Pingfang

    2015-12-01

    The effects of ultrasonic irradiation, the chelating agent modified Fenton reaction, and a combination of ultrasound and the Fenton method in removing petroleum contaminants from a soil were studied. The results showed that the contaminant removal rate of the Fenton treatment combined with an oxalic acid chelating agent was 55.6% higher than that without a chelating agent. The average removal rate of the contaminants using the ultrasound-Fenton treatment was 59.0% higher than that without ultrasonic treatment. A combination of ultrasound and an Fe(2+)/Fe(3+)-oxalate complex-modified Fenton reagent resulted in significantly higher removal rates of n-alkanes (C(n)H(2n+2), n Fenton method. The Fenton reaction and the ultrasound-Fenton treatment can unselectively remove multiple components of residual hydrocarbons and a number of benzene rings in polycyclic aromatic hydrocarbons. The chemistry of the heterocyclic compounds and the position and number of substituents can affect the degradation process.

  5. Synthesis and electrochemical and in situ spectroelectrochemical characterization of manganese, vanadyl, and cobalt phthalocyanines with 2-naphthoxy substituents

    International Nuclear Information System (INIS)

    Ozcesmeci, Ibrahim; Koca, Atif; Guel, Ahmet

    2011-01-01

    Highlights: → Metallo (Mn, Co, VO) phthalocyanines bearing peripheral 2-naphthoxy-groups were synthesized by cyclotetramerisation of the corresponding phthalonitrile derivative. → Incorporation of the redox active metal ions into the phthalocyanine core extends the redox capabilities of the Pc ring. → The presence of O 2 in the electrolyte system influences both oxygen reduction reaction and the electrochemical and spectral behaviors of the complexes. → Homogeneous catalytic ORR process occurs via an 'inner sphere' chemical catalysis process. - Abstract: Metallo (Mn, Co, VO) phthalocyanines bearing peripheral 2-naphthoxy groups were synthesized by cyclotetramerisation of the corresponding phthalonitrile derivative. The phthalocyanine compounds were characterized by elemental analyses, mass, FT-IR and UV-vis spectral data. Three intense bands in the electronic spectra clearly indicate the absorptions resulting from naphthyl groups along with the Q and B bands of the phthalocyanines. Electrochemical and spectroelectrochemical measurements exhibit that incorporation of redox active metal ions, Co II and Mn III , into the phthalocyanine core extends the redox capabilities of the Pc ring including the metal-based reduction and oxidation couples of the metal. Presence of molecular oxygen in the electrolyte system affects the voltammetric and spectroelectrochemical responses of the cobalt and manganese phthalocyanines due to the interaction between the complexes and molecular oxygen. Interaction reaction of oxygen with CoPc occurs via an 'inner sphere' chemical catalysis process. While CoPc gives the intermediates [O 2 - -Co II Pc -2 ] - and [O 2 2 -Co II Pc -2 ] 2- , MnPc forms μ-oxo MnPc species. An in situ electrocolorimetric method has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes for possible electrochromatic applications.

  6. Thermal Properties of 1-Alkyl-3-Methylimidazolium bis(trifluoromethylsulfonyl)Imide Ionic Liquids with Linear, Branched and Cyclic Alkyl Substituents.

    Czech Academy of Sciences Publication Activity Database

    Rotrekl, Jan; Storch, Jan; Kloužek, Jaroslav; Vrbka, P.; Husson, P.; Andresová, Adéla; Bendová, Magdalena; Wagner, Zdeněk

    2017-01-01

    Roč. 443, JUL 15 (2017), s. 32-43 ISSN 0378-3812 R&D Projects: GA MŠk LD14090 Institutional support: RVO:67985858 ; RVO:67985891 Keywords : ionic liquids * thermophysical properties * structure-property relationship Subject RIV: CF - Physical ; Theoretical Chemistry; CC - Organic Chemistry (USMH-B) OBOR OECD: Physical chemistry; Organic chemistry (USMH-B) Impact factor: 2.473, year: 2016

  7. Sequential Camouflage of the arachno-6,9-C2B8H14 Cage by Substituents

    Czech Academy of Sciences Publication Activity Database

    Bakardjiev, Mario; Štíbr, Bohumil; Holub, Josef; Tok, Oleg L.; Švec, Petr; Růžičková, Z.; Růžička, A.

    2016-01-01

    Roč. 55, č. 14 (2016), s. 7068-7074 ISSN 0020-1669 R&D Projects: GA ČR(CZ) GA16-01618S Institutional support: RVO:61388980 Keywords : boranes * derivatives * magnetic - resonance -spectroscopy Subject RIV: CA - Inorganic Chemistry Impact factor: 4.857, year: 2016

  8. Piperazines as nootropic agents: New derivatives of the potent cognition-enhancer DM235 carrying hydrophilic substituents.

    Science.gov (United States)

    Martino, Maria Vittoria; Guandalini, Luca; Di Cesare Mannelli, Lorenzo; Menicatti, Marta; Bartolucci, Gianluca; Dei, Silvia; Manetti, Dina; Teodori, Elisabetta; Ghelardini, Carla; Romanelli, Maria Novella

    2017-03-15

    The piperazine ring of the potent nootropic drug DM235 has been decorated with H-bond donor and acceptor groups (CH 2 OH, CH 2 OMe, CH 2 OCOMe, COOEt); the aim was to insert new functional groups, suitable for further chemical manipulation. The influence of these modifications on nootropic activity was assessed by means of the mouse passive avoidance test; some of the newly synthesized molecules (alcohol 7b, acetate 8b and ester 10d) showed interesting in vivo potency. This makes it possible to use these functional groups for adding other residues, in order to increase molecular diversity, or for anchoring a biotin group, to obtain compounds useful to capture the biological target. Moreover, the new compounds will improve our knowledge of structure activity relationships of this family of drugs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Steric congestion at, and proximity to, a ferrous center leads to hydration of α-nitrile substituents forming coordinated carboxamides.

    Science.gov (United States)

    Thallaj, Nasser K; Orain, Pierre-Yves; Thibon, Aurore; Sandroni, Martina; Welter, Richard; Mandon, Dominique

    2014-08-04

    The question of the conversion of nitrile groups into amides (nitrile hydration) by action of water in mild and eco-compatible conditions and in the presence of iron is addressed in this article. We come back to the only known example of hydration of a nitrile function into carboxamide by a ferrous [Fe(II)] center in particularly mild conditions and very efficiently and demonstrate that these unusual conditions result from the occurrence of steric stress at the reaction site and formation of a more stable end product. Two bis(cyano-substituted) (tris 2-pyridyl methyl amine) ligands have been prepared, and the structures of the corresponding FeCl2 complexes are reported, both in the solid state and in solution. These two ligands only differ by the position of the nitrile group on the tripod in the α and β position, respectively, with respect to the pyridine nitrogen. In any case, intramolecular coordination is impossible. Upon action of water, the nitrile groups are hydrated however only if they are located in the α position. The fact that the β-substituted β-(NC)2TPAFeCl2 complex is not water sensitive suggests that the reaction proceeds in an intramolecular way at the vicinity of the metal center. In the bis α-substituted α-(NC)2TPAFeCl2 complex, both functions are converted in a very clean fashion, pointing out that this complex exhibits ligand flexibility and is not deactivated after the first hydration. At a preparative scale, this reaction allows the one-pot conversion of the bis(cyano-substituted) tripod into a bis(amido-substituted) one in particularly mild conditions with a very good yield. Additionally, the XRD structure of a ferric compound in which the two carboxamido ligands are bound to the metal in a seven-coordinate environment is reported.

  10. Influence of the anion nature and alkyl substituents in the behavior of ionic liquids derived from phenylpyridines

    Science.gov (United States)

    Dreyse, Paulina; Alarcón, Antonia; Galdámez, Antonio; González, Iván; Cortés-Arriagada, Diego; Castillo, Francisco; Mella, Andy

    2018-02-01

    Quaternary alkyl 2-phenylpyridinium and 2-(2,4-difluorophenyl)pyridinium amines with iodide, hexafluorophosphate and bis(trifluoromethylsulfonyl)imide anions have been fully characterized by 1H NMR, FT-IR and MALDI mass spectroscopic methods and studied by quantum chemistry calculations. The compounds with bis(trifluoromethylsulfonyl)imide anion can be classified as ionic liquids, because they melt at room temperature. The quaternary amines with iodide and hexafluorophosphate anions are solid at 25 °C. The X-ray diffraction characterization of the 2-(2,4-difluorophenyl)-1-methylphenylpyridinium hexafluorophosphate and 1-ethyl-2-(2,4-difluorophenyl)phenylpyridinium hexafluorophosphate show an extensive series of Csbnd H⋯F, Csbnd F⋯π and Psbnd F⋯π intermolecular interactions, which give rise to a supramolecular network. The relationship between the solid-state structures and the melting points is discussed by the evaluation of the thermal behavior based on experimental data from Differential Scanning Calorimetry (DSC) studies, and also using the analysis of the ion pairs binding energies. These new compounds based on phenylpyridine allow us to grow the diversity of ionic liquids and their crystalline salts, increasing the knowledge about the chemical and physical properties of these ionic species.

  11. Syntheses, experimental and theoretical studies on absorption/emission properties of pyrazoline-containing aryl/methoxy naphthyl substituents

    Energy Technology Data Exchange (ETDEWEB)

    Trilleras, Jorge; González-López, Edwin; León-Jaramillo, Jhair; Pérez-Gamboa, Alfredo; Puello-Polo, Esneyder, E-mail: jorgetrilleras@mail.uniatlantico.edu.co [Universidad del Atlántico (Colombia); Romo, Pablo; Ortíz, Alejandro; Quiroga, Jairo [Centre for Bioinformatics and Photonics, Cali (Colombia)

    2018-05-01

    5-Aryl-3-(2-methoxynaphthalen-6-yl)-1-phenylpyrazoline derivatives were synthesized starting from (E)-1-(3-aryl)-(2-methoxynaphthalen-6-yl)-prop-2-en-1-one and phenylhydrazine. The compounds were characterized by {sup 1} H and {sup 13}C nuclear magnetic resonance (NMR), elemental analyses and mass spectrometry. Some compounds showed promising luminescence properties in solution and in solid state; the absorption and emission characteristics were measured and the fluorescence quantum yield of two of the derivatives [4,5-dihydro-3-(2-methoxynaphthalen6-yl)-5-(3,4,5-trimethoxyphenyl)-1- phenyl-1H-pyrazoline and 5-(4-chlorophenyl)-4,5-dihydro3-(2-methoxynaphthalen-6-yl)-1-phenyl-1H- pyrazoline] were found to have excellent values compared to rhodamine B standard. Theoretical calculations at time-dependent density functional theory (TD-DFT) level are in agreement with the experimental measurements and are helpful to explain the electronic behavior. (author)

  12. Novel Bradykinin Analogues Modified in the N-Terminal Part of the Molecule with a Variety of Acyl Substituents

    Czech Academy of Sciences Publication Activity Database

    Sleszynska, M.; Wierzba, T. H.; Malinowski, K.; Tůmová, Tereza; Lammek, B.; Slaninová, Jiřina; Prahl, A.

    2012-01-01

    Roč. 18, č. 2 (2012), s. 117-124 ISSN 1573-3149 Institutional research plan: CEZ:AV0Z40550506 Keywords : bradykinin analogues * B-2 receptor antagonists * bulky acyl groups * in vivo rat blood pressure test * in vitro rat uterus test Subject RIV: CE - Biochemistry Impact factor: 1.280, year: 2012

  13. Novel Countercation in MMX-Type Mixed-Valence Chain Compound: Coexistence of Neutral and Protonated Amino Substituents

    Directory of Open Access Journals (Sweden)

    Hiroaki Iguchi

    2011-10-01

    Full Text Available The first MMX-type quasi-one-dimensional (Q1D Pt chain complex (MMX chain that contains a mono-protonated diamine as countercation, {o-(H3NC6H4NH2}4[Pt2(pop4I]·H2O (pop = P2H2O52–, was synthesized. According to the crystal structural analysis, –NH2 group was hydrogen-bonded to either lattice H2O molecule or –NH3+ group in addition to typical hydrogen bond between –NH3+ group and pop ligand. To control the partial deprotonation of the countercation will be an important method for achieving the high-conductive MMX-chain polymer by the hole doping.

  14. Role of trivalent Sr substituents and Sr vacancies in tetragonaland polar states of SrTiO.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Tkach, A.; Correia, T.M.; Almeida, A.; Moreira, J.A.; Chaves, M. R.; Okhay, O.; Vilarinho, P. M.; Gregora, Ivan; Petzelt, Jan

    2011-01-01

    Roč. 59, č. 14 (2011), 5388-5397 ISSN 1359-6454 R&D Projects: GA AV ČR KAN301370701 Institutional research plan: CEZ:AV0Z10100520 Keywords : phase transformations * dynamic phenomena * Raman spectroscopy * lattice defect vacancies * perovskites Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.755, year: 2011 http://www.sciencedirect.com/science/article/pii/S1359645411003417

  15. Synthesis, Structures, and Electrochemistry of Group 6 Aminocarbenes with a P -Chelating 1''-(Diphenylphosphino)ferrocenyl Substituent

    Czech Academy of Sciences Publication Activity Database

    Meca, L.; Dvořák, D.; Ludvík, Jiří; Císařová, I.; Štěpnička, P.

    2004-01-01

    Roč. 23, č. 10 (2004), s. 2541-2551 ISSN 0276-7333 R&D Projects: GA ČR GA203/04/0487; GA ČR GA203/99/M037; GA ČR GP203/01/P002 Institutional research plan: CEZ:AV0Z4040901 Keywords : synthesis * electrochemistry of group 6 * chelating Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.196, year: 2004

  16. Synthesis of purines bearing functionalized C-substituents by the conjugate addition of nucleophiles to 6-vinylpurines and 6-ethynylpurines

    Czech Academy of Sciences Publication Activity Database

    Kuchař, Martin; Pohl, Radek; Votruba, Ivan; Hocek, Michal

    -, č. 22 (2006), s. 5083 -5098 ISSN 1434-193X R&D Projects: GA MŠk(CZ) 1M0508; GA AV ČR(CZ) 1QS400550501 Institutional research plan: CEZ:AV0Z40550506 Keywords : purines * Michael addition * conjugate additions * cross-coupling Subject RIV: CC - Organic Chemistry Impact factor: 2.769, year: 2006

  17. Geometrical criteria versus quantum chemical criteria for assessment of intramolecular hydrogen bond (IMHB) interaction: A computational comparison into the effect of chlorine substitution on IMHB of salicylic acid in its lowest energy ground state conformer

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Bijan Kumar [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India); Guchhait, Nikhil, E-mail: nikhil.guchhait@rediffmail.com [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India)

    2013-02-01

    Highlights: ► Intramolecular hydrogen bonding (IMHB) in salicylic acid and its chloro derivatives. ► A complex effect of +R and −I effect of chlorine substituents on IMHB energy. ► Interplay between IMHB energy and aromaticity. ► Directional nature of IMHB from quantum chemical assessment. ► Quantum chemical treatment vs. geometrical criteria to assess weak interaction. - Abstract: Density functional theory based computational study has been performed to characterize intramolecular hydrogen bonding (IMHB) interaction in a series of salicylic acid derivatives varying in chlorine substitution on the benzene ring. The molecular systems studied are salicylic acid, 5-chlorosalicylic acid, 3,5-dichlorosalicylic acid and 3,5,6-tricholorosalicylic acid. Major emphasis is rendered on the analysis of IMHB interaction by calculation of electron density ρ(r) and Laplacian ∇{sup 2}ρ(r) at the bond critical point using atoms-in-molecule theory. Topological features, energy densities based on ρ(r) through perturbing the intramolecular H-bond distances suggest that at equilibrium geometry the IMHB interaction develops certain characteristics typical of covalent interaction. The interplay between aromaticity and resonance-assisted hydrogen bonding (RAHB) is discussed using both geometrical and magnetic criteria as the descriptors of aromaticity. The optimized geometry features, molecular electrostatic potential map analysis are also found to produce a consensus view in relation with the formation of RAHB in these systems.

  18. Geometrical criteria versus quantum chemical criteria for assessment of intramolecular hydrogen bond (IMHB) interaction: A computational comparison into the effect of chlorine substitution on IMHB of salicylic acid in its lowest energy ground state conformer

    International Nuclear Information System (INIS)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2013-01-01

    Highlights: ► Intramolecular hydrogen bonding (IMHB) in salicylic acid and its chloro derivatives. ► A complex effect of +R and −I effect of chlorine substituents on IMHB energy. ► Interplay between IMHB energy and aromaticity. ► Directional nature of IMHB from quantum chemical assessment. ► Quantum chemical treatment vs. geometrical criteria to assess weak interaction. - Abstract: Density functional theory based computational study has been performed to characterize intramolecular hydrogen bonding (IMHB) interaction in a series of salicylic acid derivatives varying in chlorine substitution on the benzene ring. The molecular systems studied are salicylic acid, 5-chlorosalicylic acid, 3,5-dichlorosalicylic acid and 3,5,6-tricholorosalicylic acid. Major emphasis is rendered on the analysis of IMHB interaction by calculation of electron density ρ(r) and Laplacian ∇ 2 ρ(r) at the bond critical point using atoms-in-molecule theory. Topological features, energy densities based on ρ(r) through perturbing the intramolecular H-bond distances suggest that at equilibrium geometry the IMHB interaction develops certain characteristics typical of covalent interaction. The interplay between aromaticity and resonance-assisted hydrogen bonding (RAHB) is discussed using both geometrical and magnetic criteria as the descriptors of aromaticity. The optimized geometry features, molecular electrostatic potential map analysis are also found to produce a consensus view in relation with the formation of RAHB in these systems

  19. Substitution effect of pentavalent bismuth ions on the electronic structure and physicochemical properties of perovskite-structured Ba(In0.5Ta0.5-xBix)O3 semiconductors

    International Nuclear Information System (INIS)

    Kim, Tae Woo; Hur, Su Gil; Hwang, Seong-Ju; Park, Hyunwoong; Park, Yiseul; Choi, Wonyong; Choy, Jin-Ho

    2007-01-01

    We have investigated the substitution effect of pentavalent bismuth ions on the electronic structure and physicochemical properties of barium indium tantalate. X-ray diffraction, X-ray absorption spectroscopic, and energy dispersive spectroscopic microprobe analyses reveal that, under oxygen atmosphere of 1 atm, pentavalent Bi ions are successfully stabilized in the octahedral site of the perovskite tantalate lattice. According to diffuse reflectance UV-vis spectroscopic analysis, the Bi substitution gives rise to the significant narrowing of band gap of barium indium tantalate even at a low Bi content of ∼5%, underscoring a high efficiency of Bi substitution in the band gap engineering. Such an effective narrowing of the band gap upon the Bi substitution would be attributable to the lowering of conduction band position due to the high electronegativity of Bi V substituent. As a result of band gap engineering, the Ba(In 0.5 Ta 0.5-x Bi x )O 3 compounds with x ≥ 0.03 can generate photocurrents under visible light irradiation (λ > 420 nm). Based on the present experimental findings, it becomes clear that the substitution of highly electronegative p-block element like Bi V ion can provide a very powerful tool for tailoring the electronic structure and physicochemical properties of wide band gap semiconductors

  20. Identification of C-geranylated flavonoids from Paulownia catalpifolia Gong Tong fruits by HPLC-DAD-ESI-MS/MS and their anti-aging effects on 2BS cells induced by H2O2.

    Science.gov (United States)

    Tang, Wen-Zhao; Wang, Ying-Ai; Gao, Tian-Yang; Wang, Xiao-Jing; Zhao, Yun-Xue

    2017-05-01

    The fruits of Paulownia catalpifolia Gong Tong are used as a Chinese folk herbal medicine for the treatment of enteritis, tonsillitis, bronchitis, and dysentery, etc. Our previous study has identified new C-geranylated flavanones with obvious anti-proliferative effects in lung cancer A549 cells. In the present study, a new C-geranylated flavone, paucatalinone C (1) and five known C-geranylated flavanones (2-6) were isolated. In addition, a total of 34 C-geranylated flavonoids were detected by HPLC-DAD-ESI-MS/MS coupling techniques from the CH 2 Cl 2 extract of P. catalpifolia. Futhermore, anti-aging effects of isolated compounds were evaluated in vitro with premature senescent 2BS cells induced by H 2 O 2 . Phytochemical results indicated that P. catalpifolia was a natural resource of abundant C-geranylated flavonoids. Diplacone (3) and paucatalinone A (5) were the potent anti-aging agents in the premature senescent 2BS cells induced by H 2 O 2 and the C-geranyl substituent may be an important factor because of its lipophilic character. Copyright © 2017 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

  1. A 3D QSAR pharmacophore model and quantum chemical structure--activity analysis of chloroquine(CQ)-resistance reversal.

    Science.gov (United States)

    Bhattacharjee, Apurba K; Kyle, Dennis E; Vennerstrom, Jonathan L; Milhous, Wilbur K

    2002-01-01

    Using CATALYST, a three-dimensional QSAR pharmacophore model for chloroquine(CQ)-resistance reversal was developed from a training set of 17 compounds. These included imipramine (1), desipramine (2), and 15 of their analogues (3-17), some of which fully reversed CQ-resistance, while others were without effect. The generated pharmacophore model indicates that two aromatic hydrophobic interaction sites on the tricyclic ring and a hydrogen bond acceptor (lipid) site at the side chain, preferably on a nitrogen atom, are necessary for potent activity. Stereoelectronic properties calculated by using AM1 semiempirical calculations were consistent with the model, particularly the electrostatic potential profiles characterized by a localized negative potential region by the side chain nitrogen atom and a large region covering the aromatic ring. The calculated data further revealed that aminoalkyl substitution at the N5-position of the heterocycle and a secondary or tertiary aliphatic aminoalkyl nitrogen atom with a two or three carbon bridge to the heteroaromatic nitrogen (N5) are required for potent "resistance reversal activity". Lowest energy conformers for 1-17 were determined and optimized to afford stereoelectronic properties such as molecular orbital energies, electrostatic potentials, atomic charges, proton affinities, octanol-water partition coefficients (log P), and structural parameters. For 1-17, fairly good correlation exists between resistance reversal activity and intrinsic basicity of the nitrogen atom at the tricyclic ring system, frontier orbital energies, and lipophilicity. Significantly, nine out of 11 of a group of structurally diverse CQ-resistance reversal agents mapped very well on the 3D QSAR pharmacophore model.

  2. Calculations of kinetic isotope effects in the Hofmann eliminations of substituted (2-phenylethyl)trimethylammonium ions

    International Nuclear Information System (INIS)

    Lewis, D.E.; Sims, L.B.; Yamataka, H.; McKenna, J.

    1980-01-01

    Theoretical calculations of kinetic isotope effects (KIE) for the Hofmann elimination of the (2-phenylethyl)trimethylammonium ion (I,Z = H) have been carried out for an extensive series of transition-state models encompassing the Elcb-like region of the E2 mechanistic spectrum. The reaction coordinate employed corresponded to the irreversible fragmentation of the base-H'-C/sub β/-C/sub α/-N system, with proton transfer being the dominant contributor. Structural parameters (bond distances and angles) were related to the independent bond orders n/sub α-N/ and n/sub β-H'/ by empirical and semiempirical relationships. The most probable transition-state structure for the reaction was determined by interpolation of the experimental values for the β-D 2 and 15 N KIE into plots of the trends of the calculated KIE. The nonsolvated models obtained in this manner gave only poor agreement between calculated and experimental secondary deuterium (α-D 2 ) and leaving group deuterium [N(CD 3 )/sub x/(CH 3 )/sub 3-x/, x = 1 to 3) KIE; explicit consideration of differential solvation of the reactant and transition state afforded the most chemically reasonable resolution of these discrepancies. Using solvated models, transition-state structures were also determined for the Hofmann elimination of parasubstituted derivatives of I (Z = OCH 3 , Cl, CF 3 ). These transition states are related by a shift parallel to the central E2 diagogonal of an O'Ferrall-Jencks reaction diagram, as predicted by Thorton, indicating that, in the absence of other factors (differing solvent or base, etc.), the extent to which negative charge is accumulated at Cβ in the transition state is solely a factor of the leaving group. Both independent bond orders (n/sub α-N/ and n/sub β-H'/) exhibit a linear dependence on the sigma value of the substituent, allowing for the first time prediction of transition states

  3. Vasodilator effects and putative guanylyl cyclase stimulation by 2-nitro-1-phenylethanone and 2-nitro-2-phenyl-propane-1,3-diol on rat aorta.

    Science.gov (United States)

    Vasconcelos, Thiago Brasileiro de; Ribeiro-Filho, Helder Veras; Lahlou, Saad; Pereira, José Geraldo de Carvalho; Oliveira, Paulo Sérgio Lopes de; Magalhães, Pedro Jorge Caldas

    2018-07-05

    Compounds containing a nitro group may reveal vasodilator properties. Several nitro compounds have a NO 2 group in a short aliphatic chain connected to an aromatic group. In this study, we evaluated in rat aorta the effects of two nitro compounds, with emphasis on a putative recruitment of the soluble guanylate cyclase (sGC) pathway to induce vasodilation. Isolated aortic rings were obtained from male Wistar rats to compare the effects induced by 2-nitro-1-phenylethanone (NPeth) or 2-nitro-2-phenyl-propane-1,3-diol (NPprop). In aortic preparations contracted with phenylephrine or KCl, NPeth and NPprop induced vasorelaxant effects that did not depend on the integrity of vascular endothelium. NPeth had a lesser vasorelaxant efficacy than NPprop and only the NPprop effects were inhibited by pretreatment with the sGC inhibitors, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or methylene blue. In an ODQ-preventable manner, NPprop inhibited the contractile component of the phenylephrine-induced response mediated by intracellular Ca 2+ release or by extracellular Ca 2+ recruitment through receptor- or voltage-operated Ca 2+ channels. In contrast, NPprop was inert against the transient contraction induced by caffeine in Ca 2+ -free medium. In an ODQ-dependent manner, NPprop inhibited the contraction induced by the protein kinase C activator phorbol 12,13-dibutyrate or by the tyrosine phosphatase inhibitor sodium orthovanadate. In silico docking analysis of a sGC homologous protein revealed preferential site for NPprop. In conclusion, the nitro compounds NPeth and NPprop induced vasorelaxation in rat aortic rings. Aliphatic chain substituents selectively interfered in the ability of these compounds to induce vasorelaxant effects, and only NPprop relaxed aortic rings via a sGC pathway. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Effects of new fluorinated analogues of GABA, pregabalin bioisosters, on the ambient level and exocytotic release of [3H]GABA from rat brain nerve terminals.

    Science.gov (United States)

    Borisova, T; Pozdnyakova, N; Shaitanova, E; Gerus, I; Dudarenko, M; Haufe, G; Kukhar, V

    2017-01-15

    Recently, we have shown that new fluorinated analogues of γ-aminobutyric acid (GABA), bioisosters of pregabalin (β-i-Bu-GABA), i.e. β-polyfluoroalkyl-GABAs (FGABAs), with substituents: β-CF 3 -β-OH (1), β-CF 3 (2); β-CF 2 CF 2 H (3), are able to increase the initial rate of [ 3 H]GABA uptake by isolated rat brain nerve terminals (synaptosomes), and this effect is higher than that of pregabalin. So, synthesized FGABAs are structural but not functional analogues of GABA. Herein, we assessed the effects of synthesized FGABAs (100μM) on the ambient level and exocytotic release of [ 3 H]GABA in nerve terminals and compared with those of pregabalin (100μM). It was shown that FGABAs 1-3 did not influence the ambient level of [ 3 H]GABA in the synaptosomal preparations, and this parameter was also not altered by pregabalin. During blockage of GABA transporters GAT1 by specific inhibitor NO-711, FGABAs and pregabalin also did not change ambient [ 3 H]GABA in synaptosomal preparations. Exocytotic release of [ 3 H]GABA from synaptosomes decreased in the presence of FGABAs 1-3 and pregabalin, and the effects of FGABAs 1 &3 were more significant than those of FGABAs 2 and pregabalin. FGABAs 1-3/pregabalin-induced decrease in exocytotic release of [ 3 H]GABA from synaptosomes was not a result of changes in the potential of the plasma membrane. Therefore, new synthesized FGABAs 1 &3 were able to decrease exocytotic release of [ 3 H]GABA from nerve terminals more effectively in comparison to pregabalin. Absence of unspecific side effects of FGABAs 1 &3 on the membrane potential makes these compounds perspective for medical application. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Cyclopentadithiophene-Benzothiadiazole Donor-Acceptor Polymers as Prototypical Semiconductors for High-Performance Field-Effect Transistors.

    Science.gov (United States)

    Li, Mengmeng; An, Cunbin; Pisula, Wojciech; Müllen, Klaus

    2018-05-15

    Donor-acceptor (D-A) conjugated polymers are of great interest as organic semiconductors, because they offer a rational tailoring of the electronic properties by modification of the donor and acceptor units. Nowadays, D-A polymers exhibit field-effect mobilities on the order of 10 -2 -10 0 cm 2 V -1 s -1 , while several examples showed a mobility over 10 cm 2 V -1 s -1 . The development of cyclopentadithiophene-benzothiadiazole (CDT-BTZ) copolymers one decade ago represents an important step toward high-performance organic semiconductors for field-effect transistors. The significant rise in field-effect mobility of CDT-BTZ in comparison to the existing D-A polymers at that time opened the door to a new research field with a large number of novel D-A systems. From this point, the device performance of CDT-BTZ was gradually improved by a systematic optimization of the synthesis and polymer structure as well as by an efficient solution processing into long-range ordered thin films. The key aspect was a comprehensive understanding of the relation between polymer structure and solid-state organization. Due to their fundamental role for the field of D-A polymers in general, this Account will for the first time explicitly focus on prototypical CDT-BTZ polymers, while other reviews provide an excellent general overview on D-A polymers. The first part of this Account discusses strategies for improving the charge carrier transport, focusing on chemical aspects. Improved synthesis as an essential stage toward high purity, and high molecular weight is a prerequisite for molecular order. The modification of substituents is a further crucial feature to tune the CDT-BTZ packing and self-assembly. Linear alkyl side chains facilitate intermolecular π-stacking interactions, while branched ones increase solubility and alter the polymer packing. Additional control over the supramolecular organization of CDT-BTZ polymers is introduced by alkenyl substituents via their cis

  6. The investigation of Fe-Mn-based alloys with shape memory effect by small-angle scattering of polarized neutrons

    International Nuclear Information System (INIS)

    Kopitsa, G.P.; Runov, V.V.; Grigoriev, S.V.; Bliznuk, V.V.; Gavriljuk, V.G.; Glavatska, N.I.

    2003-01-01

    The small-angle polarized neutron scattering (SAPNS) technique has been used to study a nuclear and magnetic homogeneity in the distribution of both substituent (Si, Cr, Ni) and interstitial (C, N) alloying elements on the mesoscopic range in Fe-Mn-based alloys with shape memory effect (SME). The four groups of alloys with various basic compositions: FeMn 18 (wt%), FeMn 20 Si 6 , FeMn 20 Cr 9 N 0.2 and FeMn 17 Cr 9 Ni 4 Si 6 were investigated. It was found that the small-angle scattering of neutrons and depolarization on these alloys are very small altogether. The scattering did not exceed 1.5% from the incident beam and depolarization ∼2% for all samples. It means that these alloys are well nuclear and magnetically homogeneous on the scale of 10-1000 A. However, the difference in the homogeneity depending on the compositions still takes place. Thus, the adding of Si in FeMn 18 and FeMn 20 Cr 9 N 0.2 alloys improves the homogeneity pronouncedly. At once, the effect of the doping by C or N atoms on the homogeneity in FeMn 20 Si 6 and FeMn 17 Cr 9 Ni 4 Si 6 alloys is multivalued and depend on the presence of substitutional atoms (Ni and Cr). The capability of SAPNS as a method for the study of mesoscopic homogeneity in materials with SME and testing of the quality of their preparation is discussed

  7. Extended-gate field-effect transistor (EG-FET) with molecularly imprinted polymer (MIP) film for selective inosine determination.

    Science.gov (United States)

    Iskierko, Zofia; Sosnowska, Marta; Sharma, Piyush Sindhu; Benincori, Tiziana; D'Souza, Francis; Kaminska, Izabela; Fronc, Krzysztof; Noworyta, Krzysztof

    2015-12-15

    A novel recognition unit of chemical sensor for selective determination of the inosine, renal disfunction biomarker, was devised and prepared. For that purpose, inosine-templated molecularly imprinted polymer (MIP) film was deposited on an extended-gate field-effect transistor (EG-FET) signal transducing unit. The MIP film was prepared by electrochemical polymerization of bis(bithiophene) derivatives bearing cytosine and boronic acid substituents, in the presence of the inosine template and a thiophene cross-linker. After MIP film deposition, the template was removed, and was confirmed by UV-visible spectroscopy. Subsequently, the film composition was characterized by spectroscopic techniques, and its morphology and thickness were determined by AFM. The finally MIP film-coated extended-gate field-effect transistor (EG-FET) was used for signal transduction. This combination is not widely studied in the literature, despite the fact that it allows for facile integration of electrodeposited MIP film with FET transducer. The linear dynamic concentration range of the chemosensor was 0.5-50 μM with inosine detectability of 0.62 μM. The obtained detectability compares well to the levels of the inosine in body fluids which are in the range 0-2.9 µM for patients with diagnosed diabetic nephropathy, gout or hyperuricemia, and can reach 25 µM in certain cases. The imprinting factor for inosine, determined from piezomicrogravimetric experiments with use of the MIP film-coated quartz crystal resonator, was found to be 5.5. Higher selectivity for inosine with respect to common interferents was also achieved with the present molecularly engineered sensing element. The obtained analytical parameters of the devised chemosensor allow for its use for practical sample measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Heterogeneous substitution effects in chlorocyanomethyl radical and chlorocyanocarbene.

    Science.gov (United States)

    Khuseynov, Dmitry; Dixon, Andrew R; Goebbert, Daniel J; Sanov, Andrei

    2013-10-17

    We report a photoelectron-imaging investigation of the chlorocyanomethyl radical (CHClCN) and the corresponding carbene (CClCN). The results are discussed in comparison with the corresponding dichloro- and dicyano-substituted species, focusing on the divergent effects of the halogen and pseudohalogen (CN) substitutions. A cooperative (captodative) interaction of the π-donor Cl and π-acceptor cyano groups favors the increased stability of the CHClCN radical, but a competition of the two substituents is observed in the singlet-triplet splitting of the carbene. The vertical detachment energy (VDE) of CHClCN(-) is determined to be 2.39 ± 0.04 eV, with the broad photoelectron band consistent with the significant geometry change predicted by theory for the detachment transition. The adiabatic electron affinity of CHClCN, EA = 1.86 ± 0.08 eV, is estimated on the basis of the experimental VDE and the computed difference between the VDE and EA values. This result allows the calculation of the bond dissociation energy of chloroacetonitrile, DH298(H-CHClCN) = 87.0 ± 2.7 kcal/mol. Photoelectron imaging of CClCN(-) reveals two main transitions, assigned to the singlet ((1)A') and triplet ((3)A″) states of the CClCN carbene. The respective VDEs are 2.76 ± 0.05 and 3.25 ± 0.05 eV. The experimental results are in good agreement with the theoretically predicted singlet-triplet vertical energy gap at the anion geometry, but inconclusive with regard to the adiabatic singlet-triplet splitting in CClCN. Consistent with the experimental findings, ab initio calculations using the spin-flip approach in combination with the coupled-cluster theory, indicate that the (1)A' and (3)A″ states are nearly degenerate, with the singlet state lying adiabatically only ∼0.01 eV below the triplet.

  9. NMR spectroscopy of selenium and tellurium organic compounds

    International Nuclear Information System (INIS)

    Kalabin, G.A.; Projdakov, A.G.; Radchenko, S.I.

    1980-01-01

    13 C NMR spectra of the substituted methylthio (seleno, telluro) acetylenes, CH 3 EC 1 identity sign C 2 R, E=S, Se, Te are measured. High sensitivity of the chemical shifts of ternary bond carbons to specific effects of heteroatoms is established. The substituent nature produces considerable effect on the sensitivity of C 1 -carbon atom to these effects. Chemical shifts of the substituent carbons do not depend on heteroatoms nature

  10. C60 Fullerene Effects on Diphenyl-N-(trichloroacetyl)-amidophosphate Interaction with DNA In Silico and Its Cytotoxic Activity Against Human Leukemic Cell Line In Vitro

    Science.gov (United States)

    Grebinyk, A.; Prylutska, S.; Grynyuk, I.; Kolp, B.; Hurmach, V.; Sliva, T.; Amirkhanov, V.; Trush, V.; Matyshevska, O.; Slobodyanik, M.; Prylutskyy, Yu.; Frohme, M.; Ritter, U.

    2018-03-01

    New representative of carbacylamidophosphates - diphenyl-N-(trichloroacetyl)-amidophosphate (HL), which contains two phenoxy substituents near the phosphoryl group, was synthesized, identified by elemental analysis and IR and NMR spectroscopy, and tested as a cytotoxic agent itself and in combination with C60 fullerene. According to molecular simulation results, C60 fullerene and HL could interact with DNA and form a rigid complex stabilized by stacking interactions of HL phenyl groups with C60 fullerene and DNA G nucleotide, as well as by interactions of HL CCl3 group by ion-π bonds with C60 molecule and by electrostatic bonds with DNA G nucleotide. With the use of MTT test, the cytotoxic activity of HL against human leukemic CCRF-CM cells with IC50 value detected at 10 μM concentration at 72 h of cells treatment was shown. Under combined action of 16 μM C60 fullerene and HL, the value of IC50 was detected at lower 5 μM HL concentration and at earlier 48 h period of incubation, besides the cytotoxic effect of HL was observed at a low 2.5 μM concentration at which HL by itself had no influence on cell viability. Binding of C60 fullerene and HL with minor DNA groove with formation of a stable complex is assumed to be one of the possible reasons of their synergistic inhibition of CCRF-CEM cells proliferation. Application of C60 fullerene in combination with 2.5 μM HL was shown to have no harmful effect on structural stability of blood erythrocytes membrane. Thus, combined action of C60 fullerene and HL in a low concentration potentiated HL cytotoxic effect against human leukemic cells and was not followed by hemolytic effect.

  11. Acetylenes bearing Aromatic Terminal Groups. : II 13C-NMR Spectra of Monosubstituted Diphenylacetylenes

    OpenAIRE

    野本, 健雄; Nomoto, Takeo

    1986-01-01

    Six monosubstituted diphenylacetylenes, p-X-C6H4-C≡C-C6H5 1 (Ⅹ=NMe2, NH2, OMe, Cl, and NO2), were synthesized, and 13C-NMR spectra of their acetylenic carbons were measured. Hammett plots of the chemical shifts of the acetylenic α-13C and β-13C (against substituent constants σ) respectively showed a linear relationship, eXCept for β-13C on NMe2 and NH2 groups. The effects of substituents on 13C-Chemical shifts of diphenylacetylenes and effeciency of the C≡C bonds in transmitting the substitue...

  12. 2-arylureidobenzoic acids

    DEFF Research Database (Denmark)

    Valgeirsson, Jon; Nielsen, Elsebet Ø; Peters, Dan

    2003-01-01

    A series of 2-arylureidobenzoic acids (AUBAs) was prepared by a short and effective synthesis, and the pharmacological activity at glutamate receptors was evaluated in vitro and in vivo. The compounds showed noncompetitive antagonistic activity at the kainate receptor subtype GluR5. The most potent...... on the benzoic acid moiety (ring A), whereas ring B tolerated a variety of substituents, but with a preference for lipophilic substituents. The most potent compounds had a 4-chloro substituent on ring A and 3-chlorobenzene (6b), 2-naphthalene (8h), or 2-indole (8k) as ring B and had IC(50) values of 1.3, 1...

  13. 13C-NMR of diterpenes with pimarane skeleton

    International Nuclear Information System (INIS)

    Garcez, W.S.; Pereira, A.L.; Silva Queiroz, P.P. da; Silva, R.S. da; Valente, L.M.M.; Peixoto, E.M.; Cunha Pinto, A. da

    1981-01-01

    The effect of substituent groups on the chemical shift of carbons using nuclear magnetic resonance spectra of carbon 13 ( 13 C-NMR) is discussed. Diterpenes having pimarane skeleton, isolated from plants of Velloziaceae family are analysed. (ARHC) [pt

  14. Cantharidin biosynthesis in a blister beetle: inhibition by 6-fluoromevalonate causes chemical disarmament.

    Science.gov (United States)

    Carrel, J E; Doom, J P; McCormick, J P

    1986-07-15

    Biosynthesis of cantharidin in a blister beetle, Lytta polita, is effectively inhibited by 6-fluoromevalonate. Inhibition is attributed specifically to the fluorine substituent. Biochemical inhibition has not been demonstrated previously for an arthropod's defensive substance.

  15. Fasina et al (2)

    African Journals Online (AJOL)

    DELL

    ligands and complexes was dependent on the electronic effect of the halogen substituent, which ... the desired ligand (4 mmol) in ethanol (30 mL) ... for 3 h and allowed to cool to room temperature. ..... oxide-quinoxaline-2-ylmethylene.

  16. Two steps simultaneous analysis of reactivity of L-norvaline in the T-for-H exchange reaction. Application of Taft equation to influence of Polar effect and steric effect

    International Nuclear Information System (INIS)

    Kataoka, Noriaki; Imaizumi, Hiroshi; Saito, Hiroshi; Sato, Takayuki; Kano, Naoki

    2010-01-01

    In order to quantitatively evaluate the influence of tritium ( 3 H or T) on ecosystem and the reactivity of materials having H atoms, the hydrogen isotope exchange reaction (T-for-H exchange reaction) between L-norvaline and HTO vapor was observed at 50-70degC in the gas-solid system. Applying the A''-McKay plot method to data obtained in the reaction, the rate constants of the functional groups in the material were obtained. Comparing these rate constants, following seven matters have been found in the T-for-H exchange reaction. (1) The reactivity of the functional groups in L-norvaline increases with increasing temperature. (2) As to L-norvaline, 1) the temperature dependence of each functional group increases with the following order: COOH group > NH 2 one. 2) the reactivity of COOH group is 2.2 times greater than that of NH 2 one. (3) As to the influence of the substituent, the reactivity of COOH group is larger than that of the NH 2 one. (4) It seems that the reactivity of the amino acid follows Taft equation. (5) Applying Taft equation, the ratio of influence of polar effect to steric one is 10:0 in NH 2 group, and is 3:7 in COOH one. (6) Using the A - McKay plot method, the reactivity of each functional group in an amino acid is able to be nondestructively, quantitatively and simultaneously analyzed without using masking reagent. (7) The method used in this work may be useful to quickly determine the reactivity of the functional groups in the materials. (author)

  17. Effect of heat reflux extraction on the structure and composition of a high-volatile bituminous coal

    International Nuclear Information System (INIS)

    Tian, Bin; Qiao, Ying-yun; Tian, Yuan-yu; Xie, Ke-chang; Li, Da-wei

    2016-01-01

    Highlights: • A novel HRE process with CYC is proposed to dissolve coal. • Most of the aliphatic compounds in coal are extracted during HRE process. • The carbon crystallite structure of coal changes after HRE process with CYC. • The thermal degradation behavior of ER is significantly different from that of the SFHB. - Abstract: Heat reflux extraction (HRE) process with cyclohexanone (CYC) in a high-performance mass transfer extractor was applied to dissolve Shenmu-Fugu high-volatile bituminous (SFHB) coal for the first time to afford extract (E) and extract residue (ER) from the extraction. SFHB, E, and ER were characterized by elemental analysis, solid-state "1"3C NMR spectrometry, FTIR spectrometry, XRD, SEM, and TG-FTIR to elucidate the effect of HRE on the evolution of functional groups and macromolecular structure of coal during extraction. The soluble portion in SFHB was 24.37% in the course of HRE with CYC. The aromaticity of SFHB derived from both curve-fitting of "1"3C NMR and FTIR spectra was obviously increased after extraction suggesting that most of the aliphatic fractions were extracted during HRE process. It was clarified that the substituted degree of aromatic ring in SFHB became low but the substituents on aromatics were larger after extraction. Due to irreversibly swelling crystal structure of SFHB, its interlayer spacing became larger and the stacking height of crystallite decreased after extraction. Moreover, significant amounts of volatile matters were extracted, which caused relatively lower mass loss rate and contents of gaseous products (CO_2, aliphatic moieties, CH_4, and CO) of ER than SFHB during main pyrolysis stage.

  18. Synthesis, Structure, Characterization, and Decomposition of Nickel Dithiocarbamates: Effect of Precursor Structure and Processing Conditions on Solid-State Products

    Science.gov (United States)

    Hepp, Aloysius F.; Kulis, Michael J.; McNatt, Jeremiah S.; Duffy, Norman V.; Hoops, Michael D.; Gorse, Elizabeth; Fanwick, Philip E.; Masnovi, John; Cowen, Jonathan E.; Dominey, Raymond N.

    2016-01-01

    Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the homoleptic mixed-organic bis-dithiocarbamates Ni[S2CN(isopropyl)(benzyl)]2, Ni[S2CN(ethyl)(n-butyl)]2, and Ni[S2CN(phenyl)(benzyl)]2, as well as the heteroleptic mixed-ligand complex NiCl[P(phenyl)3][(S2CN(phenyl)(benzyl)], were determined. Synthetic, spectroscopic, structural, thermal, and sulfide materials studies are discussed in light of prior literature. The spectroscopic results are routine. A slightly distorted square-planar nickel coordination environment was observed for all four complexes. The organic residues adopt conformations to minimize steric interactions. Steric effects also may determine puckering, if any, about the nickel and nitrogen atoms, both of which are planar or nearly so. A trans-influence affects the Ni-S bond distances. Nitrogen atoms interact with the CS2 carbons with a bond order of about 1.5, and the other substituents on nitrogen display transoid conformations. There are no strong intermolecular interactions, consistent with prior observations of the volatility of nickel dithiocarbamate complexes. Thermogravimetric analysis of the homoleptic species under inert atmosphere is consistent with production of 1:1 nickel sulfide phases. Thermolysis of nickel dithiocarbamates under flowing nitrogen produced hexagonal or -NiS as the major phase; thermolysis under flowing forming gas produced millerite (-NiS) at 300 C, godlevskite (Ni9S8) at 325 and 350 C, and heazlewoodite (Ni3S2) at 400 and 450 C. Failure to exclude oxygen results in production of nickel oxide. Nickel sulfide phases produced seem to be primarily influenced by processing conditions, in agreement with prior literature. Nickel dithiocarbamate complexes demonstrate significant promise to serve as single-source precursors to nickel sulfides, a quite interesting family of materials with numerous potential applications.

  19. Development of Effective Solvent Modifiers for the Solvent Extraction of Cesium from Alkaline High-Level Tank Waste

    International Nuclear Information System (INIS)

    Bonnesen, Peter V.; Delmau, Laetitia H.; Moyer, Bruce A.; Lumetta, Gregg J.

    2003-01-01

    A series of novel alkylphenoxy fluorinated alcohols were prepared and investigated for their effectiveness as modifiers in solvents containing calix(4)arene-bis-(tert-octylbenzo)-crown-6 for extracting cesium from alkaline nitrate media. A modifier that contained a terminal 1,1,2,2-tetrafluoroethoxy group was found to decompose following long-term exposure to warm alkaline solutions. However, replacement of the tetrafluoroethoxy group with a 2,2,3,3-tetrafluoropropoxy group led to a series of modifiers that possessed the alkaline stability required for a solvent extraction process. Within this series of modifiers, the structure of the alkyl substituent (tert-octyl, tert-butyl, tert-amyl, and sec-butyl) of the alkylphenoxy moiety was found to have a profound impact on the phase behavior of the solvent in liquid-liquid contacting experiments, and hence on the overall suitability of the modifier for a solvent extraction process. The sec-butyl derivative(1-(2,2,3,3-tetrafluoropropoxy)-3- (4-sec-butylphenoxy)-2-propanol) (Cs-7SB) was found to possess the best overall balance of properties with respect to third phase and coalescence behavior, cleanup following degradation, resistance to solids formation, and cesium distribution behavior. Accordingly, this modifier was selected for use as a component of the solvent employed in the Caustic-Side Solvent Extraction (CSSX) process for removing cesium from high level nuclear waste (HLW) at the U.S. Department of Energy's (DOE) Savannah River Site. In batch equilibrium experiments, this solvent has also been successfully shown to extract cesium from both simulated and actual solutions generated from caustic leaching of HLW tank sludge stored in tank B-110 at the DOE's Hanford Site.

  20. Rational Design of Novel Allosteric Dihydrofolate Reductase Inhibitors Showing Antibacterial Effects on Drug-Resistant Escherichia coli Escape Variants.

    Science.gov (United States)

    Srinivasan, Bharath; Rodrigues, João V; Tonddast-Navaei, Sam; Shakhnovich, Eugene; Skolnick, Jeffrey

    2017-07-21

    In drug discovery, systematic variations of substituents on a common scaffold and bioisosteric replacements are often used to generate diversity and obtain molecules with better biological effects. However, this could saturate the small-molecule diversity pool resulting in drug resistance. On the other hand, conventional drug discovery relies on targeting known pockets on protein surfaces leading to drug resistance by mutations of critical pocket residues. Here, we present a two-pronged strategy of designing novel drugs that target unique pockets on a protein's surface to overcome the above problems. Dihydrofolate reductase, DHFR, is a critical enzyme involved in thymidine and purine nucleotide biosynthesis. Several classes of compounds that are structural analogues of the substrate dihydrofolate have been explored for their antifolate activity. Here, we describe 10 novel small-molecule inhibitors of Escherichia coli DHFR, EcDHFR, belonging to the stilbenoid, deoxybenzoin, and chalcone family of compounds discovered by a combination of pocket-based virtual ligand screening and systematic scaffold hopping. These inhibitors show a unique uncompetitive or noncompetitive inhibition mechanism, distinct from those reported for all known inhibitors of DHFR, indicative of binding to a unique pocket distinct from either substrate or cofactor-binding pockets. Furthermore, we demonstrate that rescue mutants of EcDHFR, with reduced affinity to all known classes of DHFR inhibitors, are inhibited at the same concentration as the wild-type. These compounds also exhibit antibacterial activity against E. coli harboring the drug-resistant variant of DHFR. This discovery is the first report on a novel class of inhibitors targeting a unique pocket on EcDHFR.

  1. Chemical modification of a phenoxyfuranone-type strigolactone mimic for selective effects on rice tillering or Striga hermonthica seed germination.

    Science.gov (United States)

    Takahashi, Ikuo; Fukui, Kosuke; Asami, Tadao

    2016-11-01

    We previously reported that a series of phenoxyfuranone compounds, designated 'debranones', mimic strigolactone (SL) activity. 4-Bromodebranone (4BD) is a functionally selective SL mimic that reduces the number of shoot branches on rice more potently than GR24, a typical synthetic SL analogue, but does not induce seed germination in the root-parasitic plant Striga hermonthica. To enhance the selective activity of debranones in stimulating the seed germination of root-parasitic plants, we prepared several analogues of 4BD in which the chlorine atom was substituted with an H atom at the o-, m- or p-position on the phenyl ring (designated 2-, 3-, or 4-chlorodebranone, respectively) or had a bicyclic group instead of the phenyl ring. We evaluated the biological activities of the compounds with rice tillering assays and S. hermonthica seed germination assays. Both assays showed that the substituent position affected debranone efficiency, and among the monochlorodebranones, 2-chlorodebranone was more effective than the other two isomers in both assays. When the activities of the bicyclic debranones were compared in the same two assays, one was more active than GR24 in the rice tillering assay. This debranone also stimulated the germination of S. hermonthica seeds. Thus, some debranone derivatives induced the germination of S. hermonthica seeds, although their activities were still ∼1/20 that of GR24. These results strongly suggest that further and rigorous structure-activity relationship studies of the debranones will identify derivatives that more potently stimulate the suicidal germination of S. hermonthica seeds. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  2. Electrospun fibers of layered double hydroxide/biopolymer nanocomposites as effective drug delivery systems

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yue-E.; Zhu Hong; Chen Dan; Wang Ruiyu [State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200433 (China); Tjiu, Weng Weei [Institute of Materials Research and Engineering, A-STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore); Liu Tianxi, E-mail: txliu@fudan.edu.cn [State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200433 (China)

    2012-06-15

    Ibuprofen intercalated layered double hydroxide (LDH-IBU)/polycaprolactone (PCL) and LDH-IBU/polylactide (PLA) nanocomposite fibers are electrospun based on a combination of LDH-IBU with two kinds of biopolymers (i.e. PCL and PLA), to act as effective drug delivery systems. Ibuprofen (IBU) is chosen as a model drug, which is intercalated in MgAl-LDH by coprecipitation. Poly(oxyethylene-b-oxypropylene-b-oxyethylene) (Pluronic) is also added into PLA-based fibers as hydrophilicity enhancer and release modulator. LDH-IBU nanoparticles are uniformly dispersed throughout the nanocomposite fibers, as evidenced by transmission electron microscopy (TEM) observations. In vitro drug release studies show that initial IBU liberation from LDH-IBU/PCL composite fibers is remarkably slower than that from IBU/PCL fibers due to the sustained release property of LDH-IBU and heterogeneous nucleation effect of LDH-IBU on PCL chain segments. Surprisingly, the initial IBU release from LDH-IBU/PLA and LDH-IBU/PLA/Pluronic composite fibers is faster than that from the corresponding IBU/PLA and IBU/PLA/Pluronic fibers. This effect can be attributed to the strong interaction between alkyl groups in IBU molecules and methyl substituent groups of PLA as well as the hydrophilicity of LDH-IBU, which lead to an easier diffusion of water with a faster release of IBU from LDH-IBU/PLA and LDH-IBU/PLA/Pluronic composite fibers. - Graphical abstract: Ibuprofen intercalated layered double hydroxide (LDH-IBU)/polycaprolactone (PCL) and LDH-IBU/polylactide (PLA) nanocomposite fibers are electrospun based on the combination of LDHs with two kinds of biopolymers (i.e. PCL and PLA). LDH-IBU nanoparticles are uniformly dispersed throughout all the electrospun nanocomposite fibers even at a high loading level of 5 wt%. By combining the tunable drug release property of LDHs and electrospinning technique, the new drug delivery system is anticipated for effective loading and sustained release of drugs

  3. Electrospun fibers of layered double hydroxide/biopolymer nanocomposites as effective drug delivery systems

    International Nuclear Information System (INIS)

    Miao, Yue-E.; Zhu Hong; Chen Dan; Wang Ruiyu; Tjiu, Weng Weei; Liu Tianxi

    2012-01-01

    Ibuprofen intercalated layered double hydroxide (LDH-IBU)/polycaprolactone (PCL) and LDH-IBU/polylactide (PLA) nanocomposite fibers are electrospun based on a combination of LDH-IBU with two kinds of biopolymers (i.e. PCL and PLA), to act as effective drug delivery systems. Ibuprofen (IBU) is chosen as a model drug, which is intercalated in MgAl-LDH by coprecipitation. Poly(oxyethylene-b-oxypropylene-b-oxyethylene) (Pluronic) is also added into PLA-based fibers as hydrophilicity enhancer and release modulator. LDH-IBU nanoparticles are uniformly dispersed throughout the nanocomposite fibers, as evidenced by transmission electron microscopy (TEM) observations. In vitro drug release studies show that initial IBU liberation from LDH-IBU/PCL composite fibers is remarkably slower than that from IBU/PCL fibers due to the sustained release property of LDH-IBU and heterogeneous nucleation effect of LDH-IBU on PCL chain segments. Surprisingly, the initial IBU release from LDH-IBU/PLA and LDH-IBU/PLA/Pluronic composite fibers is faster than that from the corresponding IBU/PLA and IBU/PLA/Pluronic fibers. This effect can be attributed to the strong interaction between alkyl groups in IBU molecules and methyl substituent groups of PLA as well as the hydrophilicity of LDH-IBU, which lead to an easier diffusion of water with a faster release of IBU from LDH-IBU/PLA and LDH-IBU/PLA/Pluronic composite fibers. - Graphical abstract: Ibuprofen intercalated layered double hydroxide (LDH-IBU)/polycaprolactone (PCL) and LDH-IBU/polylactide (PLA) nanocomposite fibers are electrospun based on the combination of LDHs with two kinds of biopolymers (i.e. PCL and PLA). LDH-IBU nanoparticles are uniformly dispersed throughout all the electrospun nanocomposite fibers even at a high loading level of 5 wt%. By combining the tunable drug release property of LDHs and electrospinning technique, the new drug delivery system is anticipated for effective loading and sustained release of drugs

  4. Mononuclear nonheme iron(III) complexes that show superoxide dismutase-like activity and antioxidant effects against menadione-mediated oxidative stress.

    Science.gov (United States)

    Hitomi, Yutaka; Iwamoto, Yuji; Kashida, Akihiro; Kodera, Masahito

    2015-05-21

    This communication describes the superoxide dismutase (SOD)-like activity of mononuclear iron(III) complexes with pentadentate monocarboxylamido ligands. The SOD activity can be controlled by the electronic nature of the substituent group on the ligand. The nitro-substituted complex showed clear cytoprotective activity against menadione-mediated oxidative stress in cultured cells.

  5. Studies of. gamma. -ray irradiation effects on tris(. beta. -diketonato)iron(III) and cobalt(III) coordination compounds by means of Moessbauer spectroscopy and magnetic susceptibility measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, Y.; Endo, K.; Sano, H. (Tokyo Metropolitan Univ. (Japan). Faculty of Science)

    1981-06-01

    Both absorption Moessbauer spectroscopy and magnetic susceptibility measurements on tris(..beta..-diketonato)iron(III) and cobalt(III) compounds indicate that ligands which have phenyl group as a substituent are more stable to ..gamma..-ray radiolysis, in accordance with previous results of emission Moessbauer spectroscopic studies of /sup 57/Co-labelled tris (..beta..-diketonato)cobalt(III) compounds.

  6. Side Effects

    Science.gov (United States)

    Side effects are problems that occur when cancer treatment affects healthy tissues or organs. Learn about side effects caused by cancer treatment. Know what signs and symptoms to call your doctor about. Learn about treatments for side effects.

  7. Long-lived and largely red-shifted photoluminescence of solid-state rhodamine dyes: Molecular exciton coupling and structural effect

    International Nuclear Information System (INIS)

    Zhang, Xian-Fu; Zhang, Ya-Kui

    2015-01-01

    The optical absorption and fluorescence properties of five rhodamine dyes in solid-state are measured and show large difference from that in their gas phase or liquid solvents. All solid-state rhodamine dyes strongly absorb all light in UV and visible region, but emit only red and NIR fluorescence (680–800 nm, >100 nm red-shifted from that in solution). Further more, the absorption maxima of a solid-state rhodamine show a large red-shifted band (~100 nm) and blue-shifted peak (~125 nm) compared to that in solutions, indicating a strong molecular exciton coupling between molecules. All solid-state rhodamines still show reasonably good fluorescence quantum yield (Φ f ). In particular, solid-state Rhodamine B butyl ester and sulfonyl Rhodamine B showed a much longer emission lifetime (τ f ) than that of the corresponding molecular rhodamine, i.e. 4.12 and 4.14 ns in solid state compared to 1.61 and 2.47 ns in solution. The chemical structure of a rhodamine molecule showed dramatic effect on Φ f and τ f values for solid state rhodamine. The larger substituent in the benzene moiety favors higher Φ f and τ f values of rhodamine solids. These effects can be elucidated by the relation between structure-molecular distance and molecular exciton couplings. - Highlights: • Optical properties of solid rhodamines show large difference from that in solutions. • Solid-state rhodamine dyes emit red and NIR fluorescence (680–800 nm). • Solid-state rhodamines still show reasonably good fluorescence quantum yield. • Solid-state rhodamines have much longer fluorescence lifetimes than that in solutions

  8. Long-lived and largely red-shifted photoluminescence of solid-state rhodamine dyes: Molecular exciton coupling and structural effect

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xian-Fu, E-mail: zhangxianfu@tsinghua.org.cn [Institute of Applied Photochemistry & Center of Analysis and Measurements, Hebei Normal University of Science and Technology, Qinhuangdao 066004, Hebei Province (China); MPC Technologies, Hamilton, ON, Canada L8S 3H4 (Canada); Zhang, Ya-Kui [Institute of Applied Photochemistry & Center of Analysis and Measurements, Hebei Normal University of Science and Technology, Qinhuangdao 066004, Hebei Province (China)

    2015-10-15

    The optical absorption and fluorescence properties of five rhodamine dyes in solid-state are measured and show large difference from that in their gas phase or liquid solvents. All solid-state rhodamine dyes strongly absorb all light in UV and visible region, but emit only red and NIR fluorescence (680–800 nm, >100 nm red-shifted from that in solution). Further more, the absorption maxima of a solid-state rhodamine show a large red-shifted band (~100 nm) and blue-shifted peak (~125 nm) compared to that in solutions, indicating a strong molecular exciton coupling between molecules. All solid-state rhodamines still show reasonably good fluorescence quantum yield (Φ{sub f}). In particular, solid-state Rhodamine B butyl ester and sulfonyl Rhodamine B showed a much longer emission lifetime (τ{sub f}) than that of the corresponding molecular rhodamine, i.e. 4.12 and 4.14 ns in solid state compared to 1.61 and 2.47 ns in solution. The chemical structure of a rhodamine molecule showed dramatic effect on Φ{sub f} and τ{sub f} values for solid state rhodamine. The larger substituent in the benzene moiety favors higher Φ{sub f} and τ{sub f} values of rhodamine solids. These effects can be elucidated by the relation between structure-molecular distance and molecular exciton couplings. - Highlights: • Optical properties of solid rhodamines show large difference from that in solutions. • Solid-state rhodamine dyes emit red and NIR fluorescence (680–800 nm). • Solid-state rhodamines still show reasonably good fluorescence quantum yield. • Solid-state rhodamines have much longer fluorescence lifetimes than that in solutions.

  9. Temperature shift effect on the Chlorobaculum tepidum chlorosomes.

    Science.gov (United States)

    Tang, Joseph Kuo-Hsiang; Xu, Ying; Muhlmann, Guillermo M; Zare, Farrokh; Khin, Yadana; Tam, Sun W

    2013-05-01

    Chlorobaculum [Cba.] tepidum is known to grow optimally at 48-52 °C and can also be cultured at ambient temperatures. In this paper, we prepared constant temperature, temperature shift, and temperature shift followed by backshift cultures and investigated the intrinsic properties and spectral features of chlorosomes from those cultures using various approaches, including temperature-dependent measurements on circular dichroism (CD), UV-visible, and dynamic light scattering. Our studies indicate that (1) chlorosomes from constant temperature cultures at 50 and 30 °C exhibited more resistance to heat relative to temperature shift cultures; (2) as temperature increases bacteriochlorophyll c (BChl c) in chlorosomes is prone to demetalation, which forms bacteriopheophytin c, and degradation under aerobic conditions. Some BChl c aggregates inside reduced chlorosomes prepared in low-oxygen environments can reform after heat treatments; (3) temperature shift cultures synthesize and incorporate more BChl c homologs with a smaller substituent at C-8 on the chlorin ring and less BChl c homologs with a larger long-chain alcohol at C-17(3) versus constant-temperature cultures. We hypothesize that the long-chain alcohol at C-17(3) (and perhaps together with the substituent at C-8) may account for thermal stability of chlorosomes and the substituent at C-8 may assist self-assembling BChls; and (4) while almost identical absorption spectra are detected, chlorosomes from different growth conditions exhibited differences in the rotational length of the CD signal, and aerobic and reduced chlorosomes also display different Qy CD intensities. Further, chlorosomes exhibited changes of CD features in response to temperature increases. Additionally, we compare temperature-dependent studies for the Cba. tepidum chlorosomes and previous studies for the Chloroflexus aurantiacus chlorosomes. Together, our work provides useful and novel insights on the properties and organization of

  10. Kinetic Effects Of Increased Proton Transfer Distance On Proton-Coupled Oxidations Of Phenol-Amines

    Science.gov (United States)

    Rhile, Ian J.

    2011-01-01

    To test the effect of varying the proton donor-acceptor distance in proton-coupled electron transfer (PCET) reactions, the oxidation of a bicyclic amino-indanol (2) is compared with that of a closely related phenol with an ortho CPh2NH2 substituent (1). Spectroscopic, structural, thermochemical and computational studies show that the two amino-phenols are very similar, except that the O⋯N distance (dON) is >0.1 Å longer in 2 than in 1. The difference in dON is 0.13 ± 0.03 Å from X-ray crystallography and 0.165 Å from DFT calculations. Oxidations of these phenols by outer-sphere oxidants yield distonic radical cations •OAr–NH3+ by concerted proton-electron transfer (CPET). Simple tunneling and classical kinetic models both predict that the longer donor-acceptor distance in 2 should lead to slower reactions, by ca. two orders of magnitude, as well as larger H/D kinetic isotope effects (KIEs). However, kinetic studies show that the compound with the longer proton-transfer distance, 2, exhibits smaller KIEs and has rate constants that are quite close to those of 1. For example, the oxidation of 2 by the triarylamminium radical cation N(C6H4OMe)3•+ (3a+) occurs at (1.4 ± 0.1) × 104 M-1 s-1, only a factor of two slower than the closely related reaction of 1 with N(C6H4OMe)2(C6H4Br)•+ (3b+). This difference in rate constants is well accounted for by the slightly different free energies of reaction: ΔG°(2 + 3a+) = +0.078 V vs. ΔG°(1 + 3b+) = +0.04 V. The two phenol-amines do display some subtle kinetic differences: for instance, compound 2 has a shallower dependence of CPET rate constants on driving force (Brønsted α, Δln(k)/Δln(Keq)). These results show that the simple tunneling model is not a good predictor of the effect of proton donor-acceptor distance on concerted-electron transfer reactions involving strongly hydrogen-bonded systems. Computational analysis of the observed similarity of the two phenols emphasizes the importance of the highly

  11. Effects of technological learning and uranium price on nuclear cost: Preliminary insights from a multiple factors learning curve and uranium market modeling

    International Nuclear Information System (INIS)

    Kahouli, Sondes

    2011-01-01

    This paper studies the effects of returns to scale, technological learning, i.e. learning-by-doing and learning-by-searching, and uranium price on the prospects of nuclear cost decrease. We use an extended learning curve specification, named multiple factors learning curve (MFLC). In a first stage, we estimate a single MFLC. In a second stage, we estimate the MFLC under the framework of simultaneous system of equations which takes into account the uranium supply and demand. This permits not only to enhance the reliability of the estimation by incorporating the uranium price formation mechanisms in the MFLC via the price variable, but also to give preliminary insights about uranium supply and demand behaviors and the associated effects on the nuclear expansion. Results point out that the nuclear cost has important prospects for decrease via capacity expansion, i.e. learning-by-doing effects. In contrast, they show that the learning-by-searching as well as the scale effects have a limited effect on the cost decrease prospects. Conversely, results also show that uranium price exerts a positive and significant effect on nuclear cost, implying that when the uranium price increases, the nuclear power generation cost decreases. Since uranium is characterized by important physical availability, and since it represents only a minor part in the total nuclear cost, we consider that in a context of increasing demand for nuclear energy the latter result can be explained by the fact that the positive learning effects on the cost of nuclear act in a way to dissipate the negative ones that an increase in uranium price may exert. Further, results give evidence of important inertia in the supply and demand sides as well as evidence of slow correlation between the uranium market and oil market which may limit the inter-fuels substituability effects, that is, nuclear capacity expansion and associated learning-by-doing benefits. - Highlights: → We study the prospects of nuclear cost

  12. Tuning the mesomorphic properties of phenoxy-terminated smectic liquid crystals: the effect of fluoro substitution.

    Science.gov (United States)

    Thompson, Matthew; Carkner, Carolyn; Mosey, Nicholas J; Kapernaum, Nadia; Lemieux, Robert P

    2015-05-21

    The mesomorphic properties of phenoxy-terminated 5-alkoxy-2-(4-alkoxyphenyl)pyrimidine liquid crystals can be tuned in a predictable fashion with fluoro substituents on the phenoxy end-group. We show that an ortho-fluoro substituent promotes the formation of a tilted smectic C (SmC) phase whereas a para-fluoro substituent promotes the formation of an orthogonal smectic A (SmA) phase. The balance between SmA and SmC phases may be understood in terms of the energetic preference of the phenoxy end-groups to self-assemble via arene-arene interactions in a parallel or antiparallel geometry, and how these non-covalent interactions may cause either a suppression or enhancement of out-of-layer fluctuations at the interface of smectic layers. Calculations of changes in the potential energy of association ΔE for non-covalent dimers of fluoro-substituted n-butyloxybenzene molecules in parallel and antiparallel geometries support this hypothesis. We also show how mesomorphic properties can be further tuned by difluoro and perfluoro substitution, including difluoro substitution at the ortho positions, which uniquely promotes the formation of a SmC-nematic phase sequence.

  13. Electronegativity of aromatic amines as a basis for the development of ground state inhibitors of lysyl oxidase

    International Nuclear Information System (INIS)

    Williamson, P.R.; Kagan, H.M.

    1987-01-01

    Benzylamine derivatives containing para substituents of differing electronegativity as well as isomers of aminomethylpyridine have been assessed for their substrate and inhibitor potentials toward lysyl oxidase. Substituted benzylamines with increasingly electronegative para substituents had the lowest KI values and thus were the most effective inhibitors of the oxidation of elastin by lysyl oxidase. The kcat values for these compounds as substrates of lysyl oxidase were also reduced with increasingly electronegative para substituents. Both the Dkcat and D(kcat/Km) kinetic isotope effects decreased with increasingly electronegative p-substituents in [alpha, alpha'- 2 H]benzylamines. In contrast, there was no Dkcat solvent isotope effect with [ 2 H] H 2 O while the D(kcat/Km) solvent isotope effect tended to increase with increasingly electronegative p-substituents. These results are consistent with the stabilization of an enzyme-generated substrate carbanion and the retardation of substrate oxidation by electronegative substituents. Such ground state stabilization can result in compounds with increased potential for the inhibition of the oxidation of protein substrates of lysyl oxidase

  14. The mechanism for enhanced oxidation degradation of dioxin-like PCBs (PCB-77) in the atmosphere by the solvation effect.

    Science.gov (United States)

    Xin, Mei-Ling; Yang, Jia-Wen; Li, Yu

    2017-07-11

    The reaction pathways of PCB-77 in the atmosphere with ·OH, O 2 , NO x , and 1 O 2 were inferred based on density functional theory calculations with the 6-31G* basis set. The structures the reactants, transition states, intermediates, and products were optimized. The energy barriers and reaction heats were obtained to determine the energetically favorable reaction pathways. To study the solvation effect, the energy barriers and reaction rates for PCB-77 with different polar and nonpolar solvents (cyclohexane, benzene, carbon tetrachloride, chloroform, acetone, dichloromethane, ethanol, methanol, acetonitrile, dimethylsulfoxide, and water) were calculated. The results showed that ·OH preferentially added to the C5 atom of PCB-77, which has no Cl atom substituent, to generate the intermediate IM5. This intermediate subsequently reacted with O 2 via pathway A to generate IM5a, with an energy barrier of 7.27 kcal/mol and total reaction rate of 8.45 × 10 -8  cm 3 /molecule s. Pathway B involved direct dehydrogenation of IM5 to produce the OH-PCBs intermediate IM5b, with an energy barrier of 28.49 kcal/mol and total reaction rate of 1.15 × 10 -5  cm 3 /molecule s. The most likely degradation pathway of PCB-77 in the atmosphere is pathway A to produce IM5a. The solvation effect results showed that cyclohexane, carbon tetrachloride, and benzene could reduce the reaction energy barrier of pathway A. Among these solvents, the solvation effect of benzene was the largest, and could reduce the total reaction energy barrier by 25%. Cyclohexane, carbon tetrachloride, benzene, dichloromethane, acetone, and ethanol could increase the total reaction rate of pathway A. The increase in the reaction rate of pathway A with benzene was 8%. The effect of solvents on oxidative degradation of PCB-77 in the atmosphere is important. Graphical abstract The reaction pathways of PCB-77 in the atmosphere with •OH, O2, NOx, and 1O2 were inferred based on density functional theory

  15. Electrochemistry of chromium(0)-aminocarbene complexes

    International Nuclear Information System (INIS)

    Hoskovcova, Irena; Rohacova, Jana; Meca, Ludek; Tobrman, Tomas; Dvorak, Dalimil; Ludvik, Jiri

    2005-01-01

    Two series of chromium(0)-(aryl)aminocarbene complexes substituted on the ligand phenyl ring were prepared and electrochemically investigated: pentacarbonyl((N,N-dimethylamino)(phenyl)carbene(chromium(0) (Ia-e) and chelated tetracarbonyl((η 2 -N-allyl-N-allylamino)(phenyl)carbene(chromium(0) (IIa, c-e). For comparison, a tungsten analogue of IIc (III) and a chromium chelate bearing a methyl substituent instead of the phenyl group IV were taken into the study. The intramolecular interactions of p-substituents on the ligand phenyl ring with the reduction and oxidation centres of the molecule of complex (followed electrochemically using LFER [P. Zuman, Substituent Effects in Organic Polarography, Plenum Press, New York, 1967]) enabled to localize the corresponding electron transfer. The influence of the type of coordination, the substituent on the ligand phenyl ring and the central metal atom on oxidation and reduction potentials is discussed

  16. Effects of Structural Deformations on Optical Properties of Tetrabenzoporphyrins: Free-Bases and Pd Complexes

    Science.gov (United States)

    Lebedev, Artem Y.; Filatov, Mikhail A.; Cheprakov, Andrei V.; Vinogradov, Sergei A.

    2009-01-01

    A recently developed method of synthesis of π-extended porphyrins made it possible to prepare a series of tetrabenzoporphyrins (TBP) with different numbers of meso-aryl substituents. The photophysical parameters of free-bases and Pd complexes of meso-unsubstituted TBP’s, 5,15-diaryl-TBP’s (Ar2TBP’s) and 5,10,15,20-tetraaryl-TBP’s (Ar4TBP’s) were measured. For comparison, similarly meso-arylsubstituted porphyrins fused with nonaromatic cyclohexeno-rings, i.e. Arn-tetracyclohexenoporphyrins (ArnTCHP’s, n = 0, 2, 4), were also synthesized and studied. Structural information was obtained by ab initio (DFT) calculations and X-ray crystallography. It was found that: 1) Free-base Ar4TBP’s are strongly distorted out-of-plane (saddled), possess broadened, red-shifted spectra, short excited-state lifetimes and low fluorescence quantum yields (τfl = 2–3 ns, ϕfl = 0.02–0.03). These features are characteristic of other nonplanar free-base porphyrins, including Ar4TCHP’s. 2) Ar2TBP free-bases possess completely planar geometries, although with significant in-plane deformations. These deformations have practically no effect on the singlet excited-state properties of Ar2TBP’s as compared to planar meso-unsubstituted TBP’s. Both types of porphyrins retain strong fluorescence (τfl = 10–12 ns, ϕfl = 0.3–0.4), and their radiative rate constants (kr) are 3–4 times higher than those of planar H2TCHP’s. 3) Nonplanar deformations dramatically enhance nonradiative decay of triplet states of regular Pd porphyrins. For example, planar PdTCHP phosphoresces with high quantum yield (ϕphos = 0.45, τphos = 1118 µs), while saddled PdPh4TCHP is practically nonemissive. In contrast, both ruffled and saddled PdArnTBP’s retain strong phosphorescence at ambient temperatures (PdPh2TBP: τphos = 496 µs, ϕphos = 0.15; PdPh4TBP: τphos = 258 µs, ϕphos = 0.08). It appears that π-extension is capable of counterbalancing deleterious effects of nonplanar

  17. Theoretical study of X⁻ · 1 · YF (1 = triazine, X = Cl, Br and I, Y = H, Cl, Br, I, PH₂ and AsH₂): noncovalently electron-withdrawing effects on anion-arene interactions.

    Science.gov (United States)

    Chen, Yishan; Yao, Lifeng

    2014-01-01

    The ternary complexes X(-) · 1 · YF (1 = triazine, X = Cl, Br and I, Y = H, Cl, Br, I, PH2 and AsH2) have been investigated by MP2 calculations to understand the noncovalently electron-withdrawing effects on anion-arene interactions. The results indicate that in binary complexes (1 · X(-)), both weak σ-type and anion-π complexes can be formed for Cl(-) and Br(-), but only anion-π complex can be formed for I(-). Moreover, the hydrogen-bonding complex is the global minimum for all three halides in binary complexes. However, in ternary complexes, anion-π complex become unstable and only σ complex can retain in many cases for Cl(-) and Br(-). Anion-π complex keeps stable only when YF = HF. In contrast with binary complexes, σ complex become the global minimum for Cl(-) and Br(-) in ternary complexes. These changes in binding mode and strength are consistent with the results of covalently electron-withdrawing effects. However, in contrast with the covalently electron-withdrawing substituents, Cl(-) and Br(-) can attack the aromatic carbon atom to form a strong σ complex when the noncovalently electron-withdrawing effect is induced by halogen bonding. The binding behavior for I(-) is different from that for Cl(-) and Br(-) in two aspects. First, the anion-π complex for I(-) can also keep stable when the noncovalent interaction is halogen bonding. Second, the anion-π complex for I(-) is the global minimum when it can retain as a stable structure.

  18. 1H NMR spectra. Part 30(+): 1H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group.

    Science.gov (United States)

    Abraham, Raymond J; Griffiths, Lee; Perez, Manuel

    2013-03-01

    The (1)H spectra of 37 amides in CDCl(3) solvent were analysed and the chemical shifts obtained. The molecular geometries and conformational analysis of these amides were considered in detail. The NMR spectral assignments are of interest, e.g. the assignments of the formamide NH(2) protons reverse in going from CDCl(3) to more polar solvents. The substituent chemical shifts of the amide group in both aliphatic and aromatic amides were analysed using an approach based on neural network data for near (≤3 bonds removed) protons and the electric field, magnetic anisotropy, steric and for aromatic systems π effects of the amide group for more distant protons. The electric field is calculated from the partial atomic charges on the N.C═O atoms of the amide group. The magnetic anisotropy of the carbonyl group was reproduced with the asymmetric magnetic anisotropy acting at the midpoint of the carbonyl bond. The values of the anisotropies Δχ(parl) and Δχ(perp) were for the aliphatic amides 10.53 and -23.67 (×10(-6) Å(3)/molecule) and for the aromatic amides 2.12 and -10.43 (×10(-6) Å(3)/molecule). The nitrogen anisotropy was 7.62 (×10(-6) Å(3)/molecule). These values are compared with previous literature values. The (1)H chemical shifts were calculated from the semi-empirical approach and also by gauge-independent atomic orbital calculations with the density functional theory method and B3LYP/6-31G(++) (d,p) basis set. The semi-empirical approach gave good agreement with root mean square error of 0.081 ppm for the data set of 280 entries. The gauge-independent atomic orbital approach was generally acceptable, but significant errors (ca. 1 ppm) were found for the NH and CHO protons and also for some other protons. Copyright © 2013 John Wiley & Sons, Ltd.

  19. Effects of structure of fatty acid collectors on the adsorption of fluorapatite (0 0 1) surface: A first-principles calculations

    Science.gov (United States)

    Xie, Jun; Li, Xianhai; Mao, Song; Li, Longjiang; Ke, Baolin; Zhang, Qin

    2018-06-01

    Effects of carbon chain length, carbon chain isomerism, Cdbnd C double bonds number on fatty acid adsorption on FAP (0 0 1) surface have been investigated based on DFT. The results revealed that fatty acid collector can form stable adsorption configuration at Ca1 (surf) site. Chemical adsorption was formed between O (mole) of fatty acid collector and the Ca1 (surf) of fluorapatite (0 0 1) surface; hydrogen bond adsorption was formed between the H (mole) of fatty acid and the O (surf) of-[PO4]- of FAP (0 0 1) surface. Fatty acid collectors and FAP (0 0 1) surface are bonding by means of the hybridization of O (mole) 2p and Ca (surf) 4d orbitals, H (mole) 1s and O (surf) 2p orbital. The analysis of adsorption energy, DOS, electron density, Mulliken charge population and Mulliken bond population revealed that with the carbon chain growing within certain limits, the absolute value of the adsorption energy and the overlapping area between the DOS curve of O (mole) and Ca (surf) was greater, while that of H (mole) 1s and O (surf) 2p basically remained unchanged. As Cdbnd C double bonds of fatty acids increased within certain limits, the adsorption energy and the overlapping area between the state density curve of O (mole) and Ca (surf), H (mole) and O (surf) basically remained unchanged. The substituent groups of fatty acid changed, the absolute value of the adsorption energy and the overlapping area between the state density curve had a major change. The influence of fatty acids adsorption on FAP (0 0 1) surface depends mainly on the interaction between O (mole) and Ca (surf).

  20. Placebo Effect

    Science.gov (United States)

    ... C. Spencer, MD Steven Karceski, MD The placebo effect Joseph H. Friedman, MD Richard Dubinsky, MD WHAT ... placebo: a “dummy” medication that should have no effect on the condition. Placebos are not only drugs. ...

  1. Quinone 1 e and 2 e /2 H + Reduction Potentials: Identification and Analysis of Deviations from Systematic Scaling Relationships

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, Mioy T.; Anson, Colin W.; Cavell, Andrew C.; Stahl, Shannon S.; Hammes-Schiffer, Sharon

    2016-11-10

    Quinones participate in diverse electron transfer and proton-coupled electron transfer processes in chemistry and biology. An experimental study of common quinones reveals a non-linear correlation between the 1 e and 2 e/2 H+ reduction potentials. This unexpected observation prompted a computational study of 128 different quinones, probing their 1 e reduction potentials, pKa values, and 2 e/2 H+ reduction potentials. The density functional theory calculations reveal an approximately linear correlation between these three properties and an effective Hammett constant associated with the quinone substituent(s). However, deviations from this linear scaling relationship are evident for quinones that feature halogen substituents, charged substituents, intramolecular hydrogen bonding in the hydroquinone, and/or sterically bulky substituents. These results, particularly the different substituent effects on the 1 e versus 2 e /2 H+ reduction potentials, have important implications for designing quinones with tailored redox properties.

  2. Structure–property relationships in ionic liquids: Influence of branched and cyclic groups on vaporization enthalpies of imidazolium-based ILs

    International Nuclear Information System (INIS)

    Zaitsau, Dzmitry H.; Varfolomeev, Mikhail A.; Verevkin, Sergey P.; Stanton, Alexander D.; Hindman, Michelle S.; Bara, Jason E.

    2016-01-01

    Highlights: • Ionic liquids [Rmim][NTf_2] with iso-alkyl and cyclic substituents were synthesized. • Vaporization enthalpies were measured using quartz-crystal microbalance. • Data consistency was tested by comparison with the homomorph compounds. • Vaporization enthalpies of branched ILs are generally on the same level as for linear. • These findings are useful for the quick estimation of vaporization enthalpies. - Abstract: Ionic liquids (ILs) with branched and cyclic substituents are seldom studied in the literature, and as such there are little to no data characterizing their thermophysical properties. ILs with branched and cyclic substituents are just as convenient to synthesize and study as their counterparts with linear substituents, but the effects of these substituents on IL properties are not yet well-defined due to the preference for linear substituents. Standard molar vaporization enthalpies of six imidazolium based ionic liquids [Rmim][NTf_2] with iso-alkyl and cyclic substituents (R = iso-propyl, iso-butyl, sec-butyl, methylcyclopropyl, cyclopentyl and methylcyclohexyl) were derived from quartz-crystal microbalance (QCM) method. Enthalpies of vaporization measured at elevated temperatures have been adjusted to the reference temperature 298 K and tested for consistency by comparison with the homomorphy alkane, alkylbenzenes and alkyl-imidazoles. It was found that vaporization enthalpies of ILs with the iso-alkyl and cyclic groups are generally on the same level within (±2 to 3) kJ · mol"−"1 significantly compared to the analogous ILs with the imidazolium cation substituted with the linear alkyl substituents of the same chain length. These findings are useful for the quick estimation of vaporization enthalpies of various substituted IL cations (e.g. pyrrolidinium, ammonium, pyridinium, etc.).

  3. Solvent Annealing Effects in Dithieno[3,2-b:2',3'-d]pyrrole–5,6-Difluorobenzo[c][1,2,5]thiadiazole Small Molecule Donors for BHJ Solar Cells

    KAUST Repository

    Wang, Kai; Azouz, Mehdi; Babics, Maxime; Cruciani, Federico; Marszalek, Tomasz; Saleem, Qasim; Pisula, Wojciech; Beaujuge, Pierre

    2016-01-01

    Low-bandgap small molecule (SM) donors that can be solution-processed with fullerene acceptors (e.g. PC61/71BM) are proving particularly promising in bulk-heterojunction (BHJ) solar cells. Compared to their π-conjugated polymer counterparts, SM donors are well defined (monodispersed) and more synthetically modular –with relatively wide ranges of bandgaps achievable in stepwise couplings of various donor and acceptor motifs. However, the optimization of SM-fullerene morphologies and BHJ device efficiencies relies more specifically on the use of processing additives, post-processing thermal or solvent vapor annealing (SVA) approaches, and achieving adequate interpenetrating networks and structural order in BHJ thin films can be challenging. In this report, we examine the correlated effects of molecular structure and post-processing SVA on the BHJ solar cell performance of a set of π-extended SM donors composed of dithieno[3,2-b:2',3'-d]pyrrole (DTP) and 5,6-difluorobenzo[c][1,2,5]thiadiazole ([2F]BT) units. In these systems (SM1-3), the introduction of additional alkyl substituents and unsubstituted thiophene rings on the peripheral unit groups critically impacts the effects of SVA steps on BHJ solar cell efficiency. We show that the more π-extended and alkyl-substituted analogue SM3 stands out –with BHJ device efficiencies of ca. 6% obtained from SVA with CS2– while SVA-treated SM3-based active layers also show the most favorable ordering and carrier mobility patterns. However, unlike numbers of SM donors reported in recent years, DTP–[2F]BT SM analogues are in general not prone to dramatic performance variations in BHJ thin films cast with processing additives. Our results indicate that the role of SVA steps is not independent of the molecular structure of the SM donors used in the BHJ solar cells.

  4. Solvent Annealing Effects in Dithieno[3,2-b:2',3'-d]pyrrole–5,6-Difluorobenzo[c][1,2,5]thiadiazole Small Molecule Donors for BHJ Solar Cells

    KAUST Repository

    Wang, Kai

    2016-06-17

    Low-bandgap small molecule (SM) donors that can be solution-processed with fullerene acceptors (e.g. PC61/71BM) are proving particularly promising in bulk-heterojunction (BHJ) solar cells. Compared to their π-conjugated polymer counterparts, SM donors are well defined (monodispersed) and more synthetically modular –with relatively wide ranges of bandgaps achievable in stepwise couplings of various donor and acceptor motifs. However, the optimization of SM-fullerene morphologies and BHJ device efficiencies relies more specifically on the use of processing additives, post-processing thermal or solvent vapor annealing (SVA) approaches, and achieving adequate interpenetrating networks and structural order in BHJ thin films can be challenging. In this report, we examine the correlated effects of molecular structure and post-processing SVA on the BHJ solar cell performance of a set of π-extended SM donors composed of dithieno[3,2-b:2\\',3\\'-d]pyrrole (DTP) and 5,6-difluorobenzo[c][1,2,5]thiadiazole ([2F]BT) units. In these systems (SM1-3), the introduction of additional alkyl substituents and unsubstituted thiophene rings on the peripheral unit groups critically impacts the effects of SVA steps on BHJ solar cell efficiency. We show that the more π-extended and alkyl-substituted analogue SM3 stands out –with BHJ device efficiencies of ca. 6% obtained from SVA with CS2– while SVA-treated SM3-based active layers also show the most favorable ordering and carrier mobility patterns. However, unlike numbers of SM donors reported in recent years, DTP–[2F]BT SM analogues are in general not prone to dramatic performance variations in BHJ thin films cast with processing additives. Our results indicate that the role of SVA steps is not independent of the molecular structure of the SM donors used in the BHJ solar cells.

  5. Systems effectiveness

    CERN Document Server

    Habayeb, A R

    1987-01-01

    Highlights three principal applications of system effectiveness: hardware system evaluation, organizational development and evaluation, and conflict analysis. The text emphasizes the commonality of the system effectiveness discipline. The first part of the work presents a framework for system effectiveness, partitioning and hierarchy of hardware systems. The second part covers the structure, hierarchy, states, functions and activities of organizations. Contains an extended Appendix on mathematical concepts and also several project suggestions.

  6. "Further Effects"

    Science.gov (United States)

    Kinigstein, Steven Michael

    In writing Further Effects, I intended to illustrate the benefits that are to be had from the use of effects - processing, when applied at the compositional level, rather than as a post-compositional afterthought. When effects are used creatively in the compositional stage, they will influence the very nature of a piece. They are capable of expressing rhythmic and metric ideas. They can alter the natural timbre of an instrument. This can be done on levels of abstraction ranging from discreet subtlety to disguise beyond recognition. There is one effect (known as "pitch shift.") that allows an instrument to play pitches that are well outside of its range. In Further Effects, I direct the performers to use a volume pedal (which I view as a tool, rather than an effect) for the broadened creative use of dynamics that it so efficiently grants. The use of an effects processor and volume pedal creates a need for ancillary equipment. An amplifier, cables, and an electric hook-up (a microphone or a pickup) will be required for each instrument. While an amplifier serves to project the processed sound, there must also be a device or method to suppress unprocessed sound. A great deal of thought and work goes into the use of effects; yet I feel it is wasteful to use this musical resource merely as post-compositional decoration.

  7. Greenhouse effect

    International Nuclear Information System (INIS)

    1992-01-01

    This special issue is devoted to the greenhouse effect and reviews the possible climate change by mankind, paleoclimates, climate models, measurement of terrestrial temperature, CO 2 concentration and energy policy

  8. Biological effects

    International Nuclear Information System (INIS)

    Trott, K.R.

    1973-01-01

    Following an introduction into the field of cellular radiation effect considering the most important experimental results, the biological significance of the colony formation ability is brought out. The inactivation concept of stem cells does not only prove to be good, according to the present results, in the interpretation of the pathogenesis of acute radiation effects on moult tissue, it also enables chronicle radiation injuries to be interpreted through changes in the fibrous part of the organs. Radiation therapy of tumours can also be explained to a large extent by the radiation effect on the unlimited reproductiveness of tumour cells. The more or less similar dose effect curves for healthy and tumour tissue in practice lead to intermittent irradiation. The dependence of the intermittent doses and intervals on factors such as Elkind recovery, synchronisation, redistribution, reoxygenation, repopulation and regeneration are reviewed. (ORU/LH) [de

  9. Effective Programming

    DEFF Research Database (Denmark)

    Frost, Jacob

    To investigate the use of VTLoE as a basis for formal derivation of functional programs with effects. As a part of the process, a number of issues central to effective formal programming are considered. In particular it is considered how to develop a proof system suitable for pratical reasoning......, how to implement this system in the generic proof assistant Isabelle and finally how to apply the logic and the implementation to programming....

  10. Facebook Effect

    OpenAIRE

    STOICA, Anamaria

    2011-01-01

    This research paper is intended to understand the effects that Facebook, the social networking site has upon us, whether it influences our lives in a good or in a bad way. In order to understand the Facebook Effect we are trying to see how it impacts our lives at economic level,social level, political level, terminology level , psychological level and cultural level . Starting from the question : What does Facebook want? we found several answers consisting in pros and cons of this phenomenon ...

  11. Effective leadership

    OpenAIRE

    Vávrová, Zuzana

    2010-01-01

    In my bachelor thesis I describe problems of effective leadership in organization in relation with organization's objectives filling. I focus here on main principles of leadership process. I characterize process of leadership and personality of leader, who is active executor of this process in organization. The effective leadership is here evaluated mainly from organization theory point of view and in relation with requirements to management, especially its relation with leadership and its de...

  12. On the relationship between corrosion inhibiting effect and molecular structure of 2,5-bis(n-pyridyl)-1,3,4-thiadiazole derivatives in acidic media: Ac impedance and DFT studies

    Energy Technology Data Exchange (ETDEWEB)

    Bentiss, F., E-mail: fbentiss@enscl.f [Laboratoire de Chimie de Coordination et d' Analytique (LCCA), Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco); Mernari, B. [Laboratoire de Chimie de Coordination et d' Analytique (LCCA), Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco); Traisnel, M. [Unite Materiaux et Transformations (UMET), Ingenierie des Systemes Polymeres, CNRS UMR 8207, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France); Vezin, H. [Laboratoire de Spectrochimie Infrarouge et Raman (LASIR), UMR-CNRS 8516, Universite des Sciences et Technologies de Lille, Batiment C5, F-59655 Villeneuve d' Ascq Cedex (France); Lagrenee, M., E-mail: michel.lagrenee@ensc-lille.f [Unite de Catalyse et de Chimie du Solide (UCCS), UMR-CNRS 8181, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France)

    2011-01-15

    Research highlights: {yields}2,5-Bis(n-pyridyl)-1,3,4-thiadiazoles (n-PTH) act as good inhibitors for the mild steel in acidic media. {yields}The inhibiting protection depends on the position of the nitrogen on the pyridinium substituent according to order 3-PTH > 2-PTH > 4-PTH. {yields}The adsorption of n-PTH is found to follow the Langmuir's adsorption isotherm. {yields}Data obtained from quantum chemical calculations using DFT method were correlated to the experimentally obtained inhibition efficiencies. - Abstract: The inhibition properties of 2,5-bis(n-pyridyl)-1,3,4-thiadiazoles (n-PTH) on corrosion of mild steel in different acidic media (1 M HCl, 0.5 M H{sub 2}SO{sub 4} and 1 M HClO{sub 4}) were analyzed by electrochemical impedance spectroscopy (EIS). The n-PTH derivatives exhibit good inhibition properties in different acidic solutions and the calculated values of {Delta}G{sub ads}{sup 0} revealed that the adsorption mechanism of n-PTH on steel surface is mainly due to chemisorption. While in 1 M HClO{sub 4}, both 2-PTH and 4-PTH isomers stimulate the corrosion process especially at low concentrations. Quantum chemical calculations using the density functional theory (DFT) were performed on n-PTH derivatives to determine the relationship between molecular structure and their inhibition efficiencies. The results of the quantum chemical calculations and experimental inhibition efficiency were subjected to correlation analysis and indicate that the inhibition effects of n-PTH may be explained in terms of electronic properties.

  13. [Effective delegation].

    Science.gov (United States)

    Fang, Li; Hung, Chich-Hsiu

    2008-12-01

    Ninety-seven percent of middle level managers feel they face work overload. The source of this problem may lie in a failure to delegate tasks effectively. If a manager does not effectively delegate, he/she is more likely to report fatigue, stress and depression. Conversely, effectively delegating tasks will improve overall job quality, professional growth in subordinates and cooperation within the team. While it is necessary for managers to delegate tasks effectively, few can be considered to be good natural 'delegators'. Learning and training is necessary for managers to develop the necessary confidence and maturity. This article describes the definitions, purpose and benefits of delegation; factors related to effective delegation; strategies related to successful delegation and skills related to performing cross-cultural delegations. Such issues have seldom been addressed in previous articles. Moreover, nursing implications and suggested applications in nursing practice, education, management and research are mentioned. This article is intended to provide directions to nursing managers and subordinates to promote delegation knowledge and skills.

  14. Treatment Effects

    DEFF Research Database (Denmark)

    Heckman, James J.; Lopes, Hedibert F.; Piatek, Rémi

    2014-01-01

    This paper contributes to the emerging Bayesian literature on treatment effects. It derives treatment parameters in the framework of a potential outcomes model with a treatment choice equation, where the correlation between the unobservable components of the model is driven by a low-dimensional v......This paper contributes to the emerging Bayesian literature on treatment effects. It derives treatment parameters in the framework of a potential outcomes model with a treatment choice equation, where the correlation between the unobservable components of the model is driven by a low...... to observe the same person in both the treated and untreated states, but it also turns out to be straightforward to implement. Formulae are provided to compute mean treatment effects as well as their distributional versions. A Monte Carlo simulation study is carried out to illustrate how the methodology can...

  15. A novel shogaol analog suppresses cancer cell invasion and inflammation, and displays cytoprotective effects through modulation of NF-κB and Nrf2-Keap1 signaling pathways

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Fei-Fei; Ling, Hui; Ang, Xiaohui; Reddy, Shridhivya A.; Lee, Stephanie S-H.; Yang, Hong; Tan, Sock-Hoon [Department of Pharmacy, Faculty of Science, National University of Singapore (Singapore); Hayes, John D. [Jacqui Wood Cancer Centre, Division of Cancer Research, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland (United Kingdom); Chui, Wai-Keung [Department of Pharmacy, Faculty of Science, National University of Singapore (Singapore); Chew, Eng-Hui, E-mail: phaceh@nus.edu.sg [Department of Pharmacy, Faculty of Science, National University of Singapore (Singapore)

    2013-11-01

    Natural compounds containing vanilloid and Michael acceptor moieties appear to possess anti-cancer and chemopreventive properties. The ginger constituent shogaol represents one such compound. In this study, the anti-cancer potential of a synthetic novel shogaol analog 3-phenyl-3-shogaol (3-Ph-3-SG) was assessed by evaluating its effects on signaling pathways. At non-toxic concentrations, 3-Ph-3-SG suppressed cancer cell invasion in MDA-MB-231 and MCF-7 breast carcinoma cells through inhibition of PMA-activated MMP-9 expression. At similar concentrations, 3-Ph-3-SG reduced expression of the inflammatory mediators nitric oxide (NO), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and prostanglandin-E{sub 2} (PGE{sub 2}) in RAW 264.7 macrophage-like cells. Inhibition of cancer cell invasion and inflammation by 3-Ph-3-SG were mediated through suppression of the nuclear factor-kappaB (NF-κB) signaling pathway. The 3-Ph-3-SG also demonstrated cytoprotective effects by inducing the antioxidant response element (ARE)-driven genes NAD(P)H quinone oxidoreductase-1 (NQO1) and heme oxygenase-1 (HO-1). Cytoprotection by 3-Ph-3-SG was achieved at least partly through modification of cysteine residues in the E3 ubiquitin ligase substrate adaptor Kelch-like ECH-associated protein 1 (Keap1), which resulted in accumulation of transcription factor NF-E2 p45-related factor 2 (Nrf2). The activities of 3-Ph-3-SG were comparable to those of 6-shogaol, the most abundant naturally-occurring shogaol, and stronger than those of 4-hydroxyl-null deshydroxy-3-phenyl-3-shogaol, which attested the importance of the 4-hydroxy substituent in the vanilloid moiety for bioactivity. In summary, 3-Ph-3-SG is shown to possess activities that modulate stress-associated pathways relevant to multiple steps in carcinogenesis. Therefore, it warrants further investigation of this compound as a promising candidate for use in chemotherapeutic and chemopreventive strategies. - Highlights:

  16. Preference for occupany of axial positions by substituents bonded to the heterocyclic ring in penta-O-acetyl-(+)-catechin in the crystalline state

    Science.gov (United States)

    Frank R. Fronczek; Garret Gannuch; Wayne L. Mattice; Richard W. Hemingway; Giacomo Chiari; Fred L. Tobiason; Karl Houglum; Armen Shanafelt

    1985-01-01

    The structure of penta-O-acetyl-(+)-catechin has been determined in the crystalline state. Crystals are monoclinic, space group C2, a=2320.0(7), b=980.1 (2), c=1108.0(3) pm, β=100.64(2)., Z=4, Dc=1.342 g cm-3, R=0.058 for 1121 observations. One of the acetyl groups is disordered. Axial positions...

  17. Utilizing alkoxyphenyl substituents for side-chain engineering of efficient benzo[1,2-b:4,5-b ']dithiophene-based small molecule organic solar cells

    DEFF Research Database (Denmark)

    Du, Zhengkun; Chen, Weichao; Qiu, Meng

    2015-01-01

    -processed organic solar cells (OSCs) as an electron donor material, in which an alkoxyphenyl group was introduced as a weak electrondonating side chain of the BDT moiety. The DCA3TBDTP molecule exhibited good solubility, a deep highest occupied molecular orbital (HOMO) level (-5.25 eV), an appropriate optical band......-gap (1.82 eV) and a high decomposition temperature (362 degrees C). By applying the simple solution spin-coating fabrication process, the bulk heterojunction (BHJ) OSCs based on DCA3TBDTP and [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) exhibited a good power conversion efficiency (PCE) of 4...

  18. A comparative study of fluorine substituents for enhanced stability of flexible and ITO-free high-performance polymer solar cells

    DEFF Research Database (Denmark)

    Carlé, Jon Eggert; Helgesen, Martin; Zawacka, Natalia Klaudia

    2014-01-01

    lifetime in flexible large area roll-coated bulk heterojunction solar cells. The two polymer series have different side chains on the BDT unit, namely 2-hexyldecyloxy (BDTHDO) (P1-P3) or 2-hexyldecylthiophene (BDT THD) (P4-P6). The photochemical stability clearly shows that the stability enhances along...... with the number of fluorine atoms incorporated on the polymer backbone. Fabrication of the polymer solar cells based on the materials was carried out in ambient atmosphere on a roll coating/printing machine employing flexible and indium-tin-oxide-free plastic substrates. Solar cells based on the P4-P6 series...... in the performance followed by a much slower decay rate, still retaining 40-55% of their initial performance after 250 h of testing under ISOS-L-1 conditions. © 2014 Wiley Periodicals, Inc....

  19. A ditopic calix[6]arene ligand with N-methyl-imidazole and 1,2,3-triazole substituents: Synthesis and coordination with Zn(II) cations

    Czech Academy of Sciences Publication Activity Database

    Colasson, B.; Save, M.; Milko, Petr; Roithová, Jana; Schröder, Detlef; Reinaud, O.

    2007-01-01

    Roč. 9, č. 24 (2007), s. 4987-4990 ISSN 1523-7060 R&D Projects: GA AV ČR KJB400550704 Grant - others:CNRS(FR) ANR-05-BLAN-0003 Institutional research plan: CEZ:AV0Z40550506 Keywords : calixarenes * mass spectroscopy * supramolecular chemistry * zinc Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.802, year: 2007

  20. Influence of polystyrene/phenyl substituents in precursors on microstructures of Si-O-C composite anodes for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Fukui, Hiroshi; Ohsuka, Hisashi; Hino, Takakazu [Dow Corning Toray Company, Ltd., Chigusa-Kaigan, Ichihara 299-0108 (Japan); Kanamura, Kiyoshi [Department of Applied Chemistry, Tokyo Metropolitan University, Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan)

    2011-01-01

    Pyrolysis of methylphenyl-substituted branched polysilane-polystyrene polymer blends led to the formation of silicon oxycarbide (Si-O-C) glasses with microstructures similar to those found in hard carbon. Electrochemical measurements showed that the Si-O-C composite materials had lithium storage capacities of more than 500 mA h g{sup -1}, with a short but characteristic pseudo-voltage plateau at ca. 0.1 V upon delithiation. This voltage plateau indicates the existence of micropores where less-ionic lithium species can be formed, as seen in the case of hard carbon. The micropores were minor electrochemically active sites but led to an increase in the capacities. {sup 7}Li NMR spectra of the Si-O-C composite materials had two resonances in the fully lithiated state, and one resonance could be attributed to less-ionic lithium species in the micropores. No voltage plateau was observed upon delithiation, and only a singular {sup 7}Li NMR resonance was observed when the polysilanes alone were pyrolyzed. Although there was no decrease in the capacities, the voltage plateau disappeared with electrochemical cycling. Furthermore, different {sup 7}Li NMR resonances from those observed in the first lithiation were clearly seen. These results indicate changes in the lithium environments in the Si-O-C composite materials. (author)

  1. The photophysical and photochemical properties of new unmetallated and metallated phthalocyanines bearing four 5-chloroquinolin-8-yloxy substituents on peripheral sites

    Energy Technology Data Exchange (ETDEWEB)

    Nas, Asiye; Demirbaş, Ümit [Department of Chemistry, Karadeniz Technical University, 61080 Trabzon (Turkey); Pişkin, Mehmet [Marmara University, Faculty of Art and Science, Department of Chemistry, 34722 Kadıkoy-Istanbul (Turkey); Durmuş, Mahmut [Gebze Institute of Technology, Department of Chemistry, PO Box 141, Gebze, 41400 Kocaeli (Turkey); Kantekin, Halit, E-mail: halit@ktu.edu.tr [Department of Chemistry, Karadeniz Technical University, 61080 Trabzon (Turkey)

    2014-01-15

    The synthesis and characterization of novel peripherally tetrakis-(5-chloroquinolin-8-yloxy) substituted metal-free (4), zinc(II) (5), lead(II) (6), cobalt(II) (7), copper(II) (8) and nickel(II) (9) phthalocyanines are described for the first time in this study. The spectroscopic, photophysical (fluorescence quantum yields and lifetimes) and photochemical properties (singlet oxygen production and photodegradation under light irradiation) of metal-free (4), zinc(II) (5) and lead(II) (6) phthalocyanines are investigated in N,N-dimetilformamid (DMF). The newly synthesized cobalt(II) (7), copper(II) (8) and nickel(II) (9) phthalocyanine compounds were not evaluated for this purpose due to open shell nature of these central metals in the phthalocyanine cavity. The influence of various the nature of the central metal ion (zinc, lead or without metal) on these properties has also been investigated and compared. -- Highlights: • The synthesis and characterization of novel peripherally tetrakis-(5-chloroquinolin-8-yloxy) substituted metal-free (4), zinc(II) (5), lead(II) (6), cobalt(II) (7), copper(II) (8) and nickel(II) (9) phthalocyanines. • The spectroscopic, photophysical (fluorescence quantum yields and lifetimes) and photochemical properties of metal-free (4), zinc(II) (5) and lead(II) (6)phthalocyanines in N, N-dimetilformamid (DMF). • The influence of various the nature of the central metal ion (zinc, lead or without metal) on these properties.

  2. Diarylhalotelluronium(IV) cations [(8-Me2NC10H6)2TeX]+ (X = Cl, Br, I) stabilized by intramolecularly coordinating N-donor substituents.

    Science.gov (United States)

    Beckmann, Jens; Bolsinger, Jens; Duthie, Andrew; Finke, Pamela

    2013-09-14

    The stoichiometrically controlled halogenation of the intramolecularly coordinated diaryltelluride (8-Me2NC10H6)2Te using SO2Cl2, Br2 and I2 was studied. At an equimolar ratio, the diarylhalotelluronium cations [(8-Me2NC10H6)2TeX](+) (1, X = Cl; 2, X = Br; 3, X = I) formed and were isolated as 1·Cl(-)·H2O·1/2THF, 2·Br(-), and 3·I(-), respectively. When the same reactions were carried out in the presence of KPF6, 1·PF6(-) and 22·Br(-)·PF6(-) were obtained. The chlorination of (8-Me2NC10H6)2Te with an excess of SO2Cl2 occurred with a double electrophilic substitution at the 8-dimethylaminonaphthyl residues (in the ortho- and para-positions) and afforded the diaryltellurium dichloride (5,7-Cl2-8-Me2NC10H4)2TeCl2 (4). The bromination of (8-Me2NC10H6)2Te with three equivalents of Br2 took place with a single electrophilic substitution at the 8-dimethylaminonaphthyl residues (in the para-positions) and provided the diaryltellurium dibromide (5-Br-8-Me2NC10H5)2TeBr2 (5), while an excess of Br2 produced the diarylbromotelluronium cation [(5-Br-8-Me2NC10H5)2TeBr](+) (6) that was isolated as 6·Br3(-). The reaction of (8-Me2NC10H6)2Te with two or three equivalents of iodine provided 3·I3(-) and 3·I3(-)·I2, respectively. In the presence of water, 1·Cl(-)·H2O·1/2THF, 2·Br(-), 3·I(-) and 3·I3(-) hydrolyzed to give the previously known diarylhydroxytelluronium cation [(8-Me2NC10H6)2TeOH](+) (7) that was isolated as 7·Cl(-), 7·Br(-)·H2O·THF, 7·I(-) and 7·I3(-)·H2O, respectively. The molecular structures of 1-7 were investigated in the solid-state by (125)Te MAS NMR spectroscopy and X-ray crystallography and in solution by multinuclear NMR spectroscopy ((1)H, (13)C, (125)Te), electrospray mass spectrometry and conductivity measurements. The stabilization of cations 1-3 by the intramolecular coordination was estimated by DFT calculations at the B3PW91/TZ level of theory.

  3. New photoresponsive (meth)acrylate (co)polymers containing azobenzene pendant sidegroups with carboxylic and dimethylamino substituents .2. Synthesis and characterization of polymers and copolymers

    NARCIS (Netherlands)

    Haitjema, HJ; Buruma, R; VanEkenstein, GORA; Tan, YY; Challa, G

    1996-01-01

    The title (co)polymers, used for our investigations on their photoresponsive behaviour were obtained by free radical (co)polymerization. The monomer was either an acrylate or a methacrylate to which an azobenzene group, modified with a para-placed dimethylamino or a carboxylic pendant group, was

  4. Theoretical study on the Diels-Alder reaction of bromo-substituted 2H-pyrane-2-ones and some substituent vinyls

    Directory of Open Access Journals (Sweden)

    Haghdadi Mina

    2015-01-01

    Full Text Available A DFT study of the reactivity, regio- and stereoselectivity of Diels-Alder reaction between 3-bromo, 5-bromo, and 3,5-dibromo-2(H-pyran-2-ones and some weakly activated and unactivated alkenes has been carried out using density functional theory (DFT. Four possible reaction channels, which are related to the formation of meta- and para- and endo- and exo-cycloadducts have been explored and characterized. The energy and natural bond orbital analysis shows that the meta-regioselectivity on the exo pathway is preferred and follows an asynchronous concerted mechanism with a polar nature in all Diels-Alder cycloadditions. Moreover, the activation free energies of Diels-Alder cycloadditions of 3,5-dibromo-2(H-pyran-2one are lower than 3- bromo-2(H-pyran-2one and 5-bromo-2(H-pyran-2one, which are in line with experimental observation. DFT-based reactivity indices clearly predict the regiochemistry of the isolated cycloadducts.

  5. Métodos sintéticos para preparação de 2,2'-bipiridinas substituídas

    Directory of Open Access Journals (Sweden)

    Donnici Claudio Luis

    2002-01-01

    Full Text Available The 2,2'-bipyridine has been entitled as the most widely used ligand. Nowadays there is a large variety of known molecules comprising at least two 2,2'-bipyridine units and the number of applications in many areas such as catalysis, new materials, optoeletronics and electrochemistry have increased very much in the past decades. Nevertheless, there is no article that gives an overview of the main synthetic methods for obtaining the substituted 2,2'-bipyridines, generally non available. This article presents a synthetic discussion about the three different methods (coupling reaction, ciclo-functionalization and functionalization of the heteroaromatic rings of 2,2'-bipyridine for preparing these heterocyclic compounds and also provides a practical and fundamental guide, for obtaining more than eighty different symmetric and unsymmetrical substituted 2,2'-bipyridines, shown in a table with the corresponding references.

  6. Synthesis and characterization of organic dyes with various electron-accepting substituents for p-type dye-sensitized solar cells.

    Science.gov (United States)

    Weidelener, Martin; Powar, Satvasheel; Kast, Hannelore; Yu, Ze; Boix, Pablo P; Li, Chen; Müllen, Klaus; Geiger, Thomas; Kuster, Simon; Nüesch, Frank; Bach, Udo; Mishra, Amaresh; Bäuerle, Peter

    2014-11-01

    Four new donor-π-acceptor dyes differing in their acceptor group have been synthesized and employed as model systems to study the influence of the acceptor groups on the photophysical properties and in NiO-based p-type dye-sensitized solar cells. UV/Vis absorption spectra showed a broad range of absorption coverage with maxima between 331 and 653 nm. Redox potentials as well as HOMO and LUMO energies of the dyes were determined from cyclic voltammetry measurements and evaluated concerning their potential use as sensitizers in p-type dye-sensitized solar cells (p-DSCs). Quantum-chemical density functional theory calculations gave further insight into the frontier orbital distributions, which are relevant for the electronic processes in p-DSCs. In p-DSCs using an iodide/triiodide-based electrolyte, the polycyclic 9,10-dicyano-acenaphtho[1,2-b]quinoxaline (DCANQ) acceptor-containing dye gave the highest power conversion efficiency of 0.08%, which is comparable to that obtained with the perylenemonoimide (PMI)-containing dye. Interestingly, devices containing the DCANQ-based dye achieve a higher V(OC) of 163 mV compared to 158 mV for the PMI-containing dye. The result was further confirmed by impedance spectroscopic analysis showing higher recombination resistance and thus a lower recombination rate for devices containing the DCANQ dye than for PMI dye-based devices. However, the use of the strong electron-accepting tricyanofurane (TCF) group played a negative role in the device performance, yielding an efficiency of only 0.01% due to a low-lying LUMO energy level, thus resulting in an insufficient driving force for efficient dye regeneration. The results demonstrate that a careful molecular design with a proper choice of the acceptor unit is essential for development of sensitizers for p-DSCs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Shedding light on the photophysical properties of newly designed platinum(II) complexes by adding substituents on functionalized ligands as highly efficient OLED emitters from a theoretical viewpoint

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jieqiong [Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004 (China); Wang, Li, E-mail: chemwangl@henu.edu.cn [Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004 (China); Wang, Xin [Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004 (China); He, Chaozheng, E-mail: hecz2013@nynu.edu.cn [College of Physics and Electronic Engineering, Nanyang Normal University, Nanyang 473061 (China); Zhang, Jinglai, E-mail: zhangjinglai@henu.edu.cn [Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004 (China)

    2015-08-01

    The phosphorescent properties of three synthesized and three new designed platinum(II) complexes are focused on in this work. To reveal their structure–property relationships, a density functional theory/time-dependent density functional theory (DFT/TDDFT) investigation is performed on the geometric and electronic structures, absorption and emission spectra. The electroluminescent (EL) properties are evaluated by the ionization potential (IP), electron affinity (EA), and reorganization energy (λ). Furthermore, the radiative rate constant (k{sub r}) is qualitatively elucidated by various factors including the strength of the SOC interaction between the higher-lying singlet excited states (S{sub n}) and the T{sub 1} state, the oscillator strength (f) of the S{sub n} states that can couple with the T{sub 1} state, and the energy separation between the coupled states. A combined analysis of various elements that could affect the phosphorescent efficiency is beneficial to exploring efficient triplet phosphors in OLEDs. Consequently, complexes Pt-1 and 1 would be more suitable blue-emitting phosphorescent materials with balance of EL properties and acceptable quantum yields. - Graphical abstract: Display Omitted - Highlights: • The absorption and phosphorescence spectra of Pt(II) complexes are investigated. • Their Φ{sub em}, IP, EA, and reorganization energy are compared. • Three new Pt(II) complexes are designed.

  8. π-face donation from the aromatic N-substituent of N-heterocyclic carbene ligands to metal and its role in catalysis

    KAUST Repository

    Credendino, Raffaele; Falivene, Laura; Cavallo, Luigi

    2012-01-01

    excellently correlate with the experimental ΔE 1/2 potentials, offering a handle to rationalize the experimental findings. Analysis of the HOMO of the complexes before oxidation suggests that electron-donating Y groups destabilize the metal centered HOMO

  9. Potent, selective, orally bioavailable inhibitors of tumor necrosis factor-alpha converting enzyme (TACE): discovery of indole, benzofuran, imidazopyridine and pyrazolopyridine P1' substituents.

    Science.gov (United States)

    Lu, Zhonghui; Ott, Gregory R; Anand, Rajan; Liu, Rui-Qin; Covington, Maryanne B; Vaddi, Krishna; Qian, Mingxin; Newton, Robert C; Christ, David D; Trzaskos, James; Duan, James J-W

    2008-03-15

    Potent and selective inhibitors of tumor necrosis factor-alpha converting enzyme (TACE) were discovered with several new heterocyclic P1' groups in conjunction with cyclic beta-amino hydroxamic acid scaffolds. Among them, the pyrazolopyridine provided the best overall profile when combined with tetrahydropyran beta-amino hydroxamic acid scaffold. Specifically, inhibitor 49 showed IC(50) value of 1 nM against porcine TACE and 170 nM in the suppression of LPS-induced TNF-alpha of human whole blood. Compound 49 also displayed excellent selectivity over a wide panel of MMPs as well as excellent oral bioavailability (F%>90%) in rat n-in-1 PK studies.

  10. Two-dimensional NMR evidence for cleavage of lignin and xylan substituents in wheat straw through hydrothermal pretreatment and enzymatic hydrolysis

    DEFF Research Database (Denmark)

    Yelle, Daniel J.; Kaparaju, Laxmi-Narasimha Prasad; Hunt, Christopher G.

    2013-01-01

    correlation spectroscopy, via an heteronuclear single quantum coherence experiment, revealed substantial lignin β-aryl ether cleavage, deacetylation via cleavage of the natural acetates at the 2-O- and 3-O-positions of xylan, and uronic acid depletion via cleavage of the (1 → 2)-linked 4-O....... g., further deacylation revealed by the depletion in ferulate and p-coumarate structures). Supplementary chemical analyses showed that the hydrothermal pretreatment increased the cellulose and lignin concentration with partial removal of extractives and hemicelluloses. The subsequent enzymatic...

  11. Liquid Phase Behaviour in Systems of 1-Butyl-3-Alkylimidazolium bis(trifluoromethyl)SulfonylimideIonic Liquids with Water: Influence of the Structure of the C5 Alkyl Substituent.

    Czech Academy of Sciences Publication Activity Database

    Rotrekl, Jan; Storch, Jan; Velíšek, Petr; Schröer, W.; Jacquemin, J.; Wagner, Zdeněk; Husson, P.; Bendová, Magdalena

    2017-01-01

    Roč. 46, č. 7 (2017), s. 1456-1474 ISSN 0095-9782 R&D Projects: GA MŠk LD14090 Institutional support: RVO:67985858 Keywords : ionic liquids * liquid phase behaviour * ising model Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 1.342, year: 2016

  12. Two-Dimensional NMR Evidence for Cleavage of Lignin and Xylan Substituents in Wheat Straw Through Hydrothermal Pretreatment and Enzymatic Hydrolysis

    Science.gov (United States)

    Daniel J. Yelle; Prasad Kaparaju; Christopher G. Hunt; Kolby Hirth; Hoon Kim; John Ralph; Claus Felby

    2012-01-01

    Solution-state two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy of plant cell walls is a powerful tool for characterizing changes in cell wall chemistry during the hydrothermal pretreatment process of wheat straw for second-generation bioethanol production. One-bond 13C-1H NMR correlation spectroscopy, via...

  13. Generalized cytochrome P450-mediated oxidation and oxygenation reactions in aromatic substrates with activated N-H, O-H, C-H, or S-H substituents

    NARCIS (Netherlands)

    Koymans, L.; Donné-Op den Kelder, G M; te Koppele, J.M.; Vermeulen, N P

    1. The general mechanism of metabolic oxidation of substrates by cytochromes P450 (P450s) appears to consist of sequential one-electron oxidation steps rather than of a single concerted transfer of activated oxygen species from P450 to substrates. 2. In case of the acetanilides paracetamol (PAR),

  14. Electrochemical and spectroscopic properties of 1:2 Ni complexes of 1,3-substitued (CH3, OCH3) phenyl-5-phenylformazans

    International Nuclear Information System (INIS)

    Tezcan, Habibe; Uzluk, Elif; Aksu, Mehmet Levent

    2008-01-01

    In this study, new 1:2 nickel complexes of 1-[o-, m-, p-(methyl, metoxyphenyl)]-3-(p-metoxyphenyl)-5-phenylformazans were synthesized. Their structures were elucidated and spectral behaviors were investigated with the use of elemental analysis, GC-mass, 1 H NMR, 13 C NMR, IR, and UV-vis spectra. The redox characteristics of these compounds have been investigated in nonaqueous dimethylsulfoxide at platinum and ultramicro platinum (10 μm) electrodes. Through controlled potential electrolysis, the oxidation products of each class of compounds can be separated and identified. The oxidation mechanism is suggested and it is proved. It was observed the oxidation mechanism take place in a single step two-electron or one-electron transfer to a disproportionation or dimerization reactions following the radical formation step. Eventually the relation between their absorption properties and electrochemical properties was examined

  15. Ortho-substituent correlated retention of polychlorinated biphenyls on a 50% n-octyl-methylpolysiloxane stationary phase by HRGC/MSD

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, R.; Ballschmiter, K.

    1988-11-01

    Polychlorinated biphenyls (PCB) have been known as ubiquitous environmental pollutants since the late 60s. They are found partitioned between all environmental compartments according to their physico-chemical properties. Investigation of their partitioning, degradation, and transport behaviour demands sensitive and selective analytical methods for this complex mixture of up to 209 theoretically possible compounds. Congener-specific separation by high-resolution gas chromatography coupled with mass-selective detection would be a suitable approach to this multi-compound problem. In this paper, the separation of PCB congeners by capillary gas chromatography (HRGC) on a 50% n-octyl-methylpolysiloxane phase is presented.

  16. Substituent influence on the structural, vibrational and electronic properties of 2,5-dihydrothiophene-1,1-dioxide by experimental and DFT methods.

    Science.gov (United States)

    Arjunan, V; Thirunarayanan, S; Durga Devi, G; Mohan, S

    2015-11-05

    Spectroscopic and theoretical quantum chemical studies of 2,5-dihydrothiophene-1,1-dioxide and 3-methyl-2,5-dihydrothiophene-1,1-dioxide have been carried out by FTIR and FT-Raman spectral techniques along with B3LYP methods. The geometry of the compounds have been optimised by B3LYP method with 6-311++G(∗∗) and cc-pVTZ basis sets. The geometrical parameters obtained at B3LYP levels have been compared with the experimental values. Molecular electrostatic potential surface, total electron density distribution and frontier molecular orbital are constructed at B3LYP/cc-pVTZ level to understand the electronic properties. The charge density distribution and sites of chemical reactivity of the molecules have been obtained by mapping electron density isosurface with electrostatic potential surfaces. Natural bond orbital analysis of the molecules are carried out and the occupancies and the atomic hybrid contributions are calculated. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Competitive photocyclization/rearrangement of 4-aryl-1,1-dicyanobutenes controlled by intramolecular charge-transfer interaction. Effect of medium polarity, temperature, pressure, excitation wavelength, and confinement.

    Science.gov (United States)

    Ito, Tadashi; Nishiuchi, Emi; Fukuhara, Gaku; Inoue, Yoshihisa; Mori, Tadashi

    2011-09-01

    A series of 4-aryl-1,1-dicyanobutenes (1a-1f) with different substituents were synthesized to control the intramolecular donor-acceptor or charge-transfer (C-T) interactions in the ground state. Photoexcitation of these C-T substrates led to competitive cyclization and rearrangement, the ratio being critically controlled by various environmental factors, such as solvent polarity, temperature and static pressure, and also by excitation wavelength and supramolecular confinement (polyethylene voids). In non-polar solvents, the rearrangement was dominant (>10 : 1) for all examined substrates, while the cyclization was favoured in polar solvents, in particular at low temperatures. Selective excitation at the C-T band further enhanced the cyclization up to >50 : 1 ratios. More importantly, the cyclization/rearrangement ratio was revealed to be a linear function of the C-T transition energy. However, the substrates with a sterically demanding or highly electron-donating substituent failed to give the cyclization product.

  18. Genetic effects

    International Nuclear Information System (INIS)

    Kato, Hiroo

    1975-01-01

    In 1948-1953 a large scale field survey was conducted to investigate the possible genetic effects of A-bomb radiation on over 70,000 pregnancy terminations in the cities of Hiroshima and Nagasaki. The indices of possible genetic effect including sex ratio, birth weight, frequency of malformation, stillbirth, neonatal death, deaths within 9 months and anthropometric measurements at 9 months of age for these children were investigated in relation to their parent's exposure status to the A-bomb. There were no detectable genetic effects in this sample, except for a slight change in sex ratio which was in the direction to be expected if exposure had induced sex-linked lethal mutations. However, continued study of the sex ratio, based upon birth certificates in Hiroshima and Nagasaki for 1954-1962, did not confirm the earlier trend. Mortality in these children of A-bomb survivors is being followed using a cohort of 54,000 subjects. No clearly significant effect of parental exposure on survival of the children has been demonstrated up to 1972 (age 17 on the average). On the basis of the regression data, the minimal genetic doubling dose of this type of radiation for mutations resulting in death is estimated at 46 rem for the father and 125 rem for the mother. (auth.)

  19. Ventilation Effectiveness

    DEFF Research Database (Denmark)

    Mundt, M.; Mathisen, H. M.; Moser, M.

    Improving the ventilation effectiveness allows the indoor air quality to be significantly enhanced without the need for higher air changes in the building, thereby avoiding the higher costs and energy consumption associated with increasing the ventilation rates. This Guidebook provides easy-to-un...

  20. Listening Effectively.

    Science.gov (United States)

    Freshour, Frank W.

    1987-01-01

    Research indicates that people spend roughly 45 to 65 percent of their waking moments listening to other persons. To help administrators improve their listening effectiveness, a format to develop a profile of personal listening styles is provided. The strengths and weaknesses of six different listening styles are explored along with ways to…

  1. Effective Consumerism.

    Science.gov (United States)

    Daugherty, Mabel

    This module, consisting of materials for use in conducting a consumer education mini-course, deals with effective consumerism. Covered in the individual lessons are the following topics: being prepared with information (sources of consumer information and subscription forms); evaluating warranties and service contracts; evaluating advertising and…

  2. Health effects

    Energy Technology Data Exchange (ETDEWEB)

    Mahieu, L

    1998-07-01

    The main objectives of research in the field of health effects at the Belgian Nuclear Research Centre SCK-CEN are: (1) to study cancer mortality and morbidity in nuclear workers in Belgium; (2) to document the feasibility of retrospective cohort studies in Belgium; (3) to participate in the IARC study; (4) to elucidate the mechanisms of the effects of ionizing radiation on the mammalian embryo during the early phases of its development; (5) to assess the genetic risks of material exposure to ionizing radiation; (6) to elucidate the cellular mechanisms leading to brain damage after prenatal irradiation; (7) to advise authorities and to provide the general population with adequate information concerning the health risk arising from radiation exposure. Progress and major achievements in these topical areas for 1997 are reported.

  3. Health effects

    International Nuclear Information System (INIS)

    Mahieu, L.

    1998-01-01

    The main objectives of research in the field of health effects at the Belgian Nuclear Research Centre SCK-CEN are: (1) to study cancer mortality and morbidity in nuclear workers in Belgium; (2) to document the feasibility of retrospective cohort studies in Belgium; (3) to participate in the IARC study; (4) to elucidate the mechanisms of the effects of ionizing radiation on the mammalian embryo during the early phases of its development; (5) to assess the genetic risks of material exposure to ionizing radiation; (6) to elucidate the cellular mechanisms leading to brain damage after prenatal irradiation; (7) to advise authorities and to provide the general population with adequate information concerning the health risk arising from radiation exposure. Progress and major achievements in these topical areas for 1997 are reported

  4. Effective interactions

    International Nuclear Information System (INIS)

    Elliott, J.P.

    1981-01-01

    This chapter attempts to describe and compare some of the more important nucleon-nucleon interactions that have been used in nuclear structure calculations, and to relate them where possible to the real nucleon-nucleon interaction. Explains that different interactions have been used depending on whether one is fitting to total binding energies and densities with a Hartree Fock (HF) calculation or fitting to spectra and spectroscopic data in a shell model calculation. Examines both types of calculation after two preliminary sections concerned with notation and with the philosophy underlying the use of model spaces and effective interactions. Discusses Skyrme interactions, finite range interactions, small model space, large model space, and the Sussex potential matrix elements. Focuses on the more empirical approaches in which a simple form is chosen for the effective interaction in a given model space and the parameters are deduced from fitting many-body data

  5. CORRELATION ANALYSIS OF IR, 1 H- AND 13 C-NMR SPECTRAL DATA OF N-ALKYL AND N-CYCLOALKYL CYANOACETAMIDES

    Directory of Open Access Journals (Sweden)

    Aleksandar D. Marinković

    2011-09-01

    Full Text Available Linear free energy relationships (LFER were applied to the IR, 1H- and 13C--NMR spectral data in N-alkyl and N-cycloalkyl cyanoacetamides. N-alkyl and N-cycloalkyl cyanocetamides were synthesized from corresponding amine and ethyl cyanoacetate. A number of substituents were employed for alkyl substitution, and fairly good correlations were obtained, using simple Hammett equation. In N-alkyl and N-cycloalkyl cyanoacetamides substituent cause SCS of N-H hydrogen primarily by steric interaction, polar subtituent effect influences SCS shift of C=O carbon, while steric effect of N-alkyl substituent causes IR stretching frequencies of N-H, C=O and CN group. The conformations of investigated compounds have been studied by the use of semiempirical PM6 method, and together with LFER analysis, give a better insight into the influence of such a structure on the transmission of electronic substituent effects. Negative ρ values for several correlations (reverse substituent effect were found.

  6. Ventilation effectiveness

    CERN Document Server

    Mathisen, Hans Martin; Nielsen, Peter V; Moser, Alfred

    2004-01-01

    Improving the ventilation effectiveness allows the indoor air quality to be significantly enhanced without the need for higher air changes in the building, thereby avoiding the higher costs and energy consumption associated with increasing the ventilation rates. This Guidebook provides easy-to-understand descriptions of the indices used to mesure the performance of a ventilation system and which indices to use in different cases.

  7. 8-Methoxypsoralen-nucleic acid photoreaction. Effect of methyl substitution on pyrone vs. furan photoaddition

    International Nuclear Information System (INIS)

    Kanne, D.; Rapoport, H.; Hearst, J.E.

    1984-01-01

    We have synthesized a series of 8-[3H]methoxypsoralens in which methyl and hydrogen are systematically varied at the 4- and 5'-positions. Analysis of the products resulting from the photoaddition of these four psoralens with the nucleic acid poly(dA-dT) reveals that the product distribution depends on the presence or absence of a 4-methyl substituent. Compounds with the 4-methyl group show an overwhelming preference (approximately 98%) for addition to the furan double bond, while compounds without the 4-methyl show a substantial amount (approximately 18%) of addition to the pyrone double bond

  8. Solvent polarity effects on hyperfine couplings of cyclohexadienyl-type radicals

    International Nuclear Information System (INIS)

    Vujosevic', D.; Scheuermann, R.; Dilger, H.; Tucker, I.M.; Martyniak, A.; McKenzie, I.; Roduner, E.

    2006-01-01

    In this study muon-spin rotation (μSR) serves as a tool for sensitive monitoring of the environment of muoniated radicals in isotropic liquids. A systematic investigation of the behaviour of the hyperfine coupling constants of cyclohexadienyl-type radicals is performed, and it is found that they are in linear dependence on solvent polarity, with certain deviations. These deviations are discussed in detail. It is found that with increasing length of the hydroxyalkyl substituent group the perturbation of the phenyl ring becomes smaller

  9. Solvent polarity effects on hyperfine couplings of cyclohexadienyl-type radicals

    Energy Technology Data Exchange (ETDEWEB)

    Vujosevic' , D. [Institut fuer Physikalische Chemie, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany); Scheuermann, R. [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen (Switzerland); Dilger, H. [Institut fuer Physikalische Chemie, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany); Tucker, I.M. [Unilever Research and Development, Port Sunlight, Wirral CH63 3JW (United Kingdom); Martyniak, A. [Institut fuer Physikalische Chemie, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany); McKenzie, I. [Institut fuer Physikalische Chemie, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany); Roduner, E. [Institut fuer Physikalische Chemie, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany)]. E-mail: e.rodunder@ipc.uni-stuttgart.de

    2006-03-31

    In this study muon-spin rotation ({mu}SR) serves as a tool for sensitive monitoring of the environment of muoniated radicals in isotropic liquids. A systematic investigation of the behaviour of the hyperfine coupling constants of cyclohexadienyl-type radicals is performed, and it is found that they are in linear dependence on solvent polarity, with certain deviations. These deviations are discussed in detail. It is found that with increasing length of the hydroxyalkyl substituent group the perturbation of the phenyl ring becomes smaller.

  10. Greenhouse effect

    International Nuclear Information System (INIS)

    Lepetit, J.P.

    1992-01-01

    This book speaks about the growth of greenhouse gases content in the atmosphere and try to forecast the different scenarios which may happen. But, in spite of international cooperation and coordinated research programs, nobody owns the answer. So possible future climatic changes depend on the behavior of the concerned actors. A review of energy policy driven by USA, Japan, Sweden, United Kingdom and Federal Republic of Germany is given. Political management of this file and public opinion in front of greenhouse effect are also described. 7 refs., 3 figs., 6 tabs

  11. C-C bond unsaturation degree in monosubstituted ferrocenes for molecular electronics investigated by a combined near-edge x-ray absorption fine structure, x-ray photoemission spectroscopy, and density functional theory approach

    International Nuclear Information System (INIS)

    Boccia, A.; Lanzilotto, V.; Marrani, A. G.; Zanoni, R.; Stranges, S.; Alagia, M.; Fronzoni, G.; Decleva, P.

    2012-01-01

    We present the results of an experimental and theoretical investigation of monosubstituted ethyl-, vinyl-, and ethynyl-ferrocene (EtFC, VFC, and EFC) free molecules, obtained by means of synchrotron-radiation based C 1s photoabsorption (NEXAFS) and photoemission (C 1s XPS) spectroscopies, and density functional theory (DFT) calculations. Such a combined study is aimed at elucidating the role played by the C-C bond unsaturation degree of the substituent on the electronic structure of the ferrocene derivatives. Such substituents are required for molecular chemical anchoring onto relevant surfaces when ferrocenes are used for molecular electronics hybrid devices. The high resolution C 1s NEXAFS spectra exhibit distinctive features that depend on the degree of unsaturation of the hydrocarbon substituent. The theoretical approach to consider the NEXAFS spectrum made of three parts allowed to disentangle the specific contribution of the substituent group to the experimental spectrum as a function of its unsaturation degree. C 1s IEs were derived from the experimental data analysis based on the DFT calculated IE values for the different carbon atoms of the substituent and cyclopentadienyl (Cp) rings. Distinctive trends of chemical shifts were observed for the substituent carbon atoms and the substituted atom of the Cp ring along the series of ferrocenes. The calculated IE pattern was rationalized in terms of initial and final state effects influencing the IE value, with special regard to the different mechanism of electron conjugation between the Cp ring and the substituent, namely the σ/π hyperconjugation in EtFC and the π-conjugation in VFC and EFC.

  12. Effective Teachers

    Directory of Open Access Journals (Sweden)

    Beverly A. King Miller

    2015-09-01

    Full Text Available This article focuses on the educational strategies that can be used to support female students of African descent in their persistence in science, technology, engineering, and mathematics (STEM education and careers. STEM careers have historically been White male and White female dominated, which has yielded an underrepresentation of those of African descent. Drawing from a grounded qualitative case study, the data used for this article share the responses of Afro-Caribbean females in STEM who have immigrated to the United States from the country of Panama. As Latinas, they are representative of the changing face in the American educational system—bilingual, multicultural, and of African descent. The strategies offered reflect their own teaching practices, their former teachers, or experiences with their children’s teachers. What emerged were descriptions of four strategies and behaviors of effective teachers that align with Ladson-Billings’s culturally relevant pedagogy and Gay’s culturally responsive teaching. Included in the findings are the high standards and expectations embodied by effective teachers that serve to positively inspire their students. Culturally responsive teachers create an atmosphere of learning that supports academic success, conveying their belief in their students’ ability based upon their own reflectivity. As the U.S. educational system continues to become multilingual and multicultural, there is need for strategies for the successful inclusion and progression of students in STEM educational pathways and careers. This will occur as teachers challenge themselves to be the agents of change in the lives of their students.

  13. 2H Kinetic Isotope Effects and pH Dependence of Catalysis as Mechanistic Probes of Rat Monoamine Oxidase A: Comparisons with the Human Enzyme‡

    Science.gov (United States)

    Wang, Jin; Edmondson, Dale E.

    2011-01-01

    Monoamine oxidase A (MAO A) is a mitochondrial outer membrane-bound flavoenzyme important in the regulation of serotonin and dopamine levels. Since the rat is extensively used as an animal model in drug studies, it is important to understand how rat MAO A behaves in comparison with the more extensively studied human enzyme. For many reversible inhibitors, rat MAO A exhibits Ki values similar to those of human MAO A. The pH profile of kcat for rat MAO A shows a pKa of 8.2±0.1 for the benzylamine ES complex and pKa values of 7.5±0.1 and 7.6±0.1 for the respective ES complexes with p-CF3-1H and p-CF3-2H-benzylamine. In contrast to the human enzyme, the rat enzyme exhibits a single pKa value (8.3±0.1) with kcat/Km benzylamine vs. pH and pKa values of 7.8±0.1 and 8.1±0.2 are found for the ascending limbs, respectively, of kcat/Km vs. pH profiles for p-CF3-1H and p-CF3-2H-benzylamine and 9.3±0.1 and 9.1±0.2 for their respective descending limbs. The oxidation of para-substituted benzylamine substrate analogues by rat MAO A exhibit large deuterium kinetic isotope effects on kcat and on kcat/Km. These effects are pH-independent, and range from 7 to 14, demonstrating a rate-limiting α-C-H bond cleavage step in catalysis. Quantitative structure-activity correlations of log kcat with the electronic substituent parameter (σ) at pH 7.5 and at 9.0 show a dominant contribution with positive ρ values (+1.2 – 1.3) and a pH-independent negative contribution from the steric term. Quantitative structure-activity relationship analysis of the binding affinities of the para-substituted benzylamine analogues to rat MAO A show an increased van der Waals volumes (Vw) increases the affinity of the deprotonated amine for the enzyme. These results demonstrate that rat MAO A exhibits similar but not identical functional properties with the human enzyme and provide additional support for C-H bond cleavage via a polar nucleophilic mechanism. PMID:21819071

  14. ²H kinetic isotope effects and pH dependence of catalysis as mechanistic probes of rat monoamine oxidase A: comparisons with the human enzyme.

    Science.gov (United States)

    Wang, Jin; Edmondson, Dale E

    2011-09-06

    Monoamine oxidase A (MAO A) is a mitochondrial outer membrane-bound flavoenzyme important in the regulation of serotonin and dopamine levels. Because the rat is extensively used as an animal model in drug studies, it is important to understand how rat MAO A behaves in comparison with the more extensively studied human enzyme. For many reversible inhibitors, rat MAO A exhibits K(i) values similar to those of human MAO A. The pH profile of k(cat) for rat MAO A shows a pK(a) of 8.2 ± 0.1 for the benzylamine ES complex and pK(a) values of 7.5 ± 0.1 and 7.6 ± 0.1 for the ES complexes with p-CF(3)-(1)H- and p-CF(3)-(2)H-benzylamine, respectively. In contrast to the human enzyme, the rat enzyme exhibits a single pK(a) value (8.3 ± 0.1) with k(cat)/K(m) for benzylamine versus pH and pK(a) values of 7.8 ± 0.1 and 8.1 ± 0.2 for the ascending limbs, respectively, of k(cat)/K(m) versus pH profiles for p-CF(3)-(1)H- and p-CF(3)-(2)H-benzylamine and 9.3 ± 0.1 and 9.1 ± 0.2 for the descending limbs, respectively. The oxidation of para-substituted benzylamine substrate analogues by rat MAO A has large deuterium kinetic isotope effects on k(cat) and on k(cat)/K(m). These effects are pH-independent and range from 7 to 14, demonstrating a rate-limiting α-C-H bond cleavage step in catalysis. Quantitative structure-activity correlations of log k(cat) with the electronic substituent parameter (σ) at pH 7.5 and 9.0 show a dominant contribution with positive ρ values (1.2-1.3) and a pH-independent negative contribution from the steric term. Quantitative structure-activity relationship analysis of the binding affinities of the para-substituted benzylamine analogues for rat MAO A shows an increased van der Waals volume (V(w)) increases the affinity of the deprotonated amine for the enzyme. These results demonstrate that rat MAO A exhibits functional properties similar but not identical with those of the human enzyme and provide additional support for C-H bond cleavage via a polar

  15. Steric Effects on the Binding of Phosphate and Polyphosphate Anions by Zinc(II) and Copper(II) Dinuclear Complexes of m-Xylyl-bis-cyclen.

    Science.gov (United States)

    Esteves, Catarina V; Esteban-Gómez, David; Platas-Iglesias, Carlos; Tripier, Raphaël; Delgado, Rita

    2018-05-11

    The triethylbenzene-bis-cyclen (cyclen = 1,4,7,10-tetraazacyclododecane) compound (tbmce) was designed with an imposed structural rigidity at the m-xylyl spacer to be compared to a less restrained and known parent compound (bmce). The framework of both compounds differs only in the substituents of the m-xylyl spacer. The study was centered in the differences observed in the acid-base reactions of both compounds, their copper(II) and zinc(II) complexation behaviors, as well as in the uptake of phosphate and polyphosphate anions (HPPi 3- , ATP 4- , ADP 3- , AMP 2- , PhPO 4 2- , and HPO 4 2- ). On the one hand, the acid-base reactions showed lower values for the third and fourth protonation constants of tbmce than for bmce, suggesting that the ethyl groups of the spacer in tbmce force the two cyclen units to more conformational restricted positions. On the other hand, the stability constant values for copper(II) and zinc(II) complexes revealed that bmce is a better chelator than tbmce pointing out to additional conformational restraints imposed by the triethylbenzene spacer. The binding studies of phosphates by the dinuclear copper(II) and zinc(II) complexes showed much smaller effective association constants for the dicopper complexes. Single-crystal X-ray and computational (density functional theory) studies suggest that anion binding promotes the formation of tetranuclear entities in which anions are bridging the metal centers. Our studies also revealed the dinuclear zinc(II) complex of bmce as a promising receptor for phosphate anions, with the largest effective association constant of 5.94 log units being observed for the formation of [Zn 2 bmce(HPPi)] + . Accordingly, a colorimetric study via an indicator displacement assay to detect phosphates in aqueous solution found that the [Zn 2 bmce] 4+ complex acts as the best receptor for pyrophosphate displaying a detection limit of 2.5 nM by changes visible to naked eye.

  16. Radiation effects

    International Nuclear Information System (INIS)

    Collings, E.W.

    1986-01-01

    An important cause of deterioration in superconducting magnets intended for high-energy physics and fusion-reactor applications is radiation damage. The present chapter deals chiefly with the effects of electron, proton, gamma and neutron irradiation on the properties of stabilized Ti-Nb-base composite superconductors. The authors examine the particle-accelerator environment, electron irradiation of Ti-Nb superconductor, proton irradiation of Ti-Nb superconductor and its stabilizer, and deuteron irradiation of Ti-Nb superconductor. A section discussing the fusion reactor environment in general is presented, and the two principal classes of fusion reactor based on the magnetic-confinement concept, namely the tokamak and the mirrormachine are examined. Also discussed is neutron irradiation of Cu/TiNb composite superconductors and critical current density of neutronirradiated Ti-Nb. Finally, radiation damage to stabilizer and insulating materials is described

  17. Health effects

    International Nuclear Information System (INIS)

    Mahieu, L.

    1998-01-01

    The objectives of the research in the field of epidemiology , performed at the Belgian Nuclear Research Centre SCK-CEN are (1) to study cancer mortality and morbidity in nuclear workers in Belgium; (2) to document the feasibility of retrospective cohort studies in Belgium; (3) to participate in the IARC study. For radiobiology, the main objectives are: (1) to elucidate the mechanisms of the effects of ionizing radiation on the mammalian embryo during the early phase of its development, (2) to assess the genetic risks of maternal exposure to ionizing radiation, (3) to elucidate the mechanisms by which damage to the brain and mental retardation are caused in man after prenatal irradiation. The main achievements in these domains for 1997 are presented

  18. Condom effectiveness.

    Science.gov (United States)

    Porche, D J

    1998-01-01

    People who choose not to abstain from sexual intercourse can use barrier contraceptive methods, such as condoms, to reduce their risk of contracting HIV and other sexually transmitted diseases (STDs). Health care providers who provide safer sex education and counseling should provide information on condoms as a way of reducing the risk of HIV/STD transmission. Since latex condoms are regulated by the US Food and Drug Administration (FDA) as medical devices, FDA regulations govern latex condom manufacturing and testing in accordance with stringent national standards. The FDA randomly tests imported condoms according to the same stringent quality control standards as US-produced condoms. Condom effectiveness, however, depends upon their correct and consistent use during every sexual act. Relevant data and guidelines are presented on the correct use of male latex and female polyurethane condoms. Both male latex and female polyurethane condoms can prevent the transmission of HIV and other STDs.

  19. Thermodynamic Studies of (H2Rh(diphosphine)2)+ and (HRh(diphosphine)2(CH3CN))2+ Complexes in Acetonitrile

    International Nuclear Information System (INIS)

    Wilson, Aaron D.; Miller, Alexander J.M.; DuBois, Daniel L.; Labinger, Jay A.; Bercaw, John E.

    2011-01-01

    Thermodynamic studies of a series of (H2Rh(PP)2)+ and (HRh(PP)2(CH3CN))2+ complexes have been carried out in acetonitrile. Seven different diphosphine (PP) ligands were selected to allow variation of the electronic properties of the ligand substituents, the cone angles, and the natural bite angles (NBAs). Oxidative addition of H2 to (Rh(PP)2)+ complexes is favored by diphosphine ligands with large NBAs, small cone angles, and electron donating substituents, with the NBA being the dominant factor. Large pKa values for (HRh(PP)2(CH3CN))2+ complexes are favored by small ligand cone angles, small NBAs, and electron donating substituents with the cone angles playing a major role. The hydride donor abilities of (H2Rh(PP)2)+ complexes increase as the NBAs decrease, the cone angles decrease, and the electron donor abilities of the substituents increase. These results indicate that if solvent coordination is involved in hydride transfer or proton transfer reactions, the observed trends can be understood in terms of a combination of two different steric effects, NBAs and cone angles, and electron-donor effects of the ligand substituents.

  20. Photophysical, Photochemical, and BQ Quenching Properties of Zinc Phthalocyanines with Fused or Interrupted Extended Conjugation

    Directory of Open Access Journals (Sweden)

    Gülşah Gümrükçü

    2014-01-01

    Full Text Available The effects of substituents and solvents on the photophysical and photochemical parameters of zinc(II phthalocyanines containing four Schiff’s base substituents attached directly and through phenyleneoxy-bridges on peripheral positions are reported. The group effects on peripheral position and the continual and intermittent conjugation of the phthalocyanine molecules on the photophysical and photochemical properties are also investigated. General trends are described for photodegradation, singlet oxygen, and fluorescence quantum yields of these compounds in dimethylsulfoxide (DMSO, dimethylformamide (DMF, and tetrahydrofurane (THF. Among the different substituents, phthalocyanines with cinnamaldimine moieties (1c and 2c have the highest singlet oxygen quantum yields (ΦΔ and those with nitro groups (1a and 2a have the highest fluorescence quantum yields in all the solvents used. The fluorescence of the substituted zinc(II phthalocyanine complexes is effectively quenched by 1,4-benzoquinone (BQ in these solvents.