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Electron Affinity (electron + affinity)
Selected AbstractsChemInform Abstract: A Gaussian-3 Theoretical Study of Small Silicon,Lithium Clusters: Electronic Structures and Electron Affinities of SinLi - (n = 2,8).CHEMINFORM, Issue 3 2009Dongsheng Hao Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Aromaticity and Electron Affinity of Carbok -[3]radialenes, k = 0, 1, 2.CHEMINFORM, Issue 2 2004Christine Lepetit No abstract is available for this article. [source] ChemInform Abstract: Structure and Electron Affinity of Platinum FluoridesCHEMINFORM, Issue 36 2001Ralf Wesendrup Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Density functional crystal orbital study of cyano-substituted poly(para -phenylene-vinylene) and poly(quinoxaline-vinylene)INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 8 2006F. Bartha Abstract We have calculated the optical and electronic properties of several conjugated organic polymers: poly(p -phenylene-vinylene) (PPV) and its derivatives. Cyano substitutions on the phenylene ring: poly(2,5-dicyano- p -phenylene-vinylene) (2,5-DCN-PPV) and on the vinylene linkage: poly(p -phenylene-7(,8)-(di)cyano-vinylene) are considered. In addition, poly(quinoxaline-vinylene) (PQV) is studied. The infinite isolated quasi-1D chains are treated with periodic boundary conditions, using atomic basis sets. In a comparative study of PPV, some issues regarding the selection of the functionals and basis sets are discussed and excitation energies derived from time-dependent and from ordinary methods are compared. It is concluded that for these polymers the calculations are informative at the B3LYP/6-31G** density functional theory (DFT) level. The absolute values might change with improved methods, but the similarity of the polymers suggests that the relative characterization is adequate. Band structures are communicated along with characteristics of the highest occupied and the lowest unoccupied crystal orbitals (HOCO and LUCO). Electron affinities, ionization potentials, valence and conduction bandwidths, and effective masses at the bandgap are given. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Equivalent orbitals for multiconfigurational spin-tensor electron propagator method (MCSTEP): The vertical ionization potentials of B, NO, CF, and OFINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2008Dongxia Ma Abstract The multiconfigurational spin tensor electron propagator method (MCSTEP) was developed as an implementation of electron propagator/single particle Green's function methods for ionization potentials (IPs) and electron affinities (EAs). MCSTEP was specifically designed for open shell and highly correlated (nondynamically correlated) initial states. For computational efficiency the initial state used in MCSTEP is typically a small complete active space (CAS) multiconfigurational self-consistent field (MCSCF) state. If in a molecule there are some degenerate orbitals which are not fully or half occupied, usual MCSCF calculations will make these orbitals inequivalent, i.e., the occupied ones will be different from the nonoccupied ones, so that the degeneracy is broken. In this article, we use a state averaged MCSCF method to get equivalent orbitals for the initial state and import the integrals into the subsequent MCSTEP calculations. This gives, in general, more reliable MCSTEP vertical IPs. © 2008 Wiley Periodicals, Inc., 2008 [source] Geometries, vibrational frequencies, and electron affinities of X2Cl (X=C,Si,Ge) clustersINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2007Feng-You Hao Abstract Ab initio quantum chemical calculations have been performed on X2Cl, and X2Cl (X = C, Si, Ge) clusters. The geometrical structures, vibrational frequencies, electronic properties and dissociation energies are investigated at the Hartree,Fock (HF), Møller,Plesset second- and fourth-order (MP2, MP4), CCSD(T) level with the 6-311+G(d) basis set. The X2Cl (X = C, Si, Ge) and X2Cl, (X = Si, Ge) take a bent shape obtained at the ground state, while C2Cl, has a linear structure. The impact on internal electron transfer between the X2Cl and the corresponding anional clusters is studied. The three different types of electron affinities (EAs) at the CCSD(T) are reported. The most reliable adiabatic electronic affinities, obtained at the CCSD(T)/cc-pvqz level of theory, are predicted to be 3.30, 2.62, and 1.98 eV for C2Cl, Si2Cl, and Ge2Cl, respectively. The calculated EAs of C2Cl and Ge2Cl are in good agreement with theoretical results reported. The correlation effects and basis sets effects on the geometrical structures and dissociation energies are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Calculation of proton affinity using the CR-CCSD[T]/ECP methodINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 13 2006Nelson H. Morgon Abstract High-level calculations of proton and electron affinities (PA and EA) of CH2X, and CH2CHCHX, (with X = F, Cl, Br, and I) systems were obtained. The methodology employed in the PA and EA calculations is based on CR-CCSD[T]/B1//MP2/B0 and CCSD(T)/B1//MP2/B0 levels, respectively. B0 is a (small) valence basis set developed by Stevens and colleagues (SBKJC), and B1 is a larger basis set, with extra diffuse and polarization functions (B0 + s, p, d, and f functions). This scheme has been tested on systems containing H, C, and X atoms, and is shown to give good results. The differences between calculated results of PA and EA and the experimental values are in the range of 0.2,4.5 kJ · mol,1 and 0.01 to 0.10 eV, respectively. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] A combined ab initio and Franck-Condon factor simulation study on the photodetachment spectrum of ScO2,JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2009Edmond P. F. Lee Abstract Restricted-spin coupled-cluster single-double plus perturbative triple excitation {RCCSD(T)} potential energy functions (PEFs) of the 2B2 state of ScO2 and the 1A1 state of ScO2, were computed, employing the augmented correlation-consistent polarized-weighted core-valence quadruple-zeta (aug-cc-pwCVQZ) basis set for Sc and augmented correlation-consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis set for O, and with the outer core Sc 3s23p6 electrons being explicitly correlated. Franck-Condon factors, which include allowance for Duschinsky rotation and anharmonicity, were calculated using the computed RCCSD(T) PEFs, and were used to simulate the first photodetachment band of ScO2,. The simulated spectrum matches well with the corresponding experimental 355 nm photodetachment spectrum of Wu and Wang, J Phys Chem A 1998, 102, 9129, confirming the assignment of the photodetachment spectrum and the reliability of the RCCSD(T) PEFs used. Further calculations on low-lying electronic states of ScO2 gave adiabatic relative electronic energies (Te's) of, and vertical excitation energies (Tv's) to, the 2A1, 2B1, and 2A2 states of ScO2 (from the 2B2 state of ScO2), as well as electron affinities (EAs) and vertical detachment energies (VDEs) to these neutral states from the 1A1 state of ScO2,. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009 [source] Electronic structures and chemical bonding in diatomic ScX to ZnX (X = S, Se, Te)JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2007Z. J. Wu Abstract Bond distances, vibrational frequencies, electron affinities, ionization potentials, dissociation energies, and dipole moments of the title molecules in neutral, positively, and negatively charged ions were studied using density functional method. Ground electronic state was assigned for each molecule. The bonding patterns were analyzed and compared with both the available data and across the series. It was found that, besides ionic component, covalent bonds are formed between the metal s, d orbitals, and the p orbital of S, Se, and Te. For neutral and cationic molecules, the covalent character increases from ScX to CrX and from FeX to CuX with an exception of decrease at MnX and ZnX, while for anionic molecules, the trend is not obvious. For both neutral and charged molecules, the sulfides have the shortest bond distance and largest vibrational frequency, while tellurides have the largest bond distance and smallest vibrational frequency. For neutral and anionic molecules, the dissociation energy of sulfides is the largest, that of tellurides is the smallest, while this only remains true for cationic molecules from ScX+ to FeX+. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 703,714, 2007 [source] Electronic structures of 3d -metal mononitridesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2006Zhijian Wu Abstract Bond distances, vibrational frequencies, electron affinities, ionization potentials, and dissociation energies of the title molecules in neutral, positively, and negatively charged ions were studied by use of density functional methods B3LYP, BLYP, BHLYP, BPW91, and B3PW91. The calculated results are compared with experiments and previous theoretical studies. It was found that the calculated properties are highly dependent on the functionals employed, in particular for the dissociation energy and vibrational frequency. For neutral species, pure density functional methods BLYP and BPW91 have relatively good performance in reproducing the experimental bond distance and vibrational frequency. For cations, hybrid exchange functional methods B3LYP and B3PW91 are good in predicting the dissociation energy. For both neutral and charged species, BHLYP tends to give smaller dissociation energy. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 267,276, 2006 [source] Reduced basis set for the gold atom in cluster complexesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 7 2004Harold Basch Abstract To extend the metal cluster size used in interfacing between bulk metals and molecules in ab initio studies of molecular electronics and chemisorption, a reduced size atomic orbital basis set for the gold atom has been generated. Based on the SKBJ relativistic effective core potential set, the three component 5d Gaussian orbital basis set is completely contracted. Comparisons between the full and reduced basis set in Au atom clusters and cluster complexes for geometry, bond distances, dipole moments, atomic charges, spin, bond dissociation energies, lowest energy harmonic frequencies, electron affinities, ionization energies, and density of states distributions show the contracted set to be a viable replacement for the full basis set. This result is obtained using both the B3LYP and BPW91 exchange-correlation potentials in density functional theory. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 899,906, 2004 [source] The arsenic clusters Asn (n = 1,5) and their anions: Structures, thermochemistry, and electron affinitiesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 7 2004Yi Zhao Abstract The molecular structures, electron affinities, and dissociation energies of the Asn/As (n = 1,5) species have been examined using six density functional theory (DFT) methods. The basis set used in this work is of double-, plus polarization quality with additional diffuse s - and p -type functions, denoted DZP++. These methods have been carefully calibrated (Chem Rev 2002, 102, 231) for the prediction of electron affinities. The geometries are fully optimized with each DFT method independently. Three different types of the neutral-anion energy separations reported in this work are the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). The first dissociation energies De(Asn,1 -As) for the neutral Asn species, as well as those De(As -As) and De (Asn,1 -As,) for the anionic As species, have also been reported. The most reliable adiabatic electron affinities, obtained at the DZP++ BLYP level of theory, are 0.90 (As), 0.74 (As2), 1.30 (As3), 0.49 (As4), and 3.03 eV (As5), respectively. These EAad values for As, As2, and As4 are in good agreement with experiment (average absolute error 0.09 eV), but that for As3 is a bit smaller than the experimental value (1.45 ± 0.03 eV). The first dissociation energies for the neutral arsenic clusters predicted by the B3LYP method are 3.93 eV (As2), 2.04 eV (As3), 3.88 eV (As4), and 1.49 eV (As5). Compared with the available experimental dissociation energies for the neutral clusters, the theoretical predictions are excellent. Two dissociation limits are possible for the arsenic cluster anions. The atomic arsenic results are 3.91 eV (As , As, + As), 2.46 eV (As , As + As), 3.14 eV (As , As + As), and 4.01 eV (As , As + As). For dissociation to neutral arsenic clusters, the predicted dissociation energies are 2.43 eV (As , As2 + As,), 3.53 eV (As , As3 + As,), and 3.67 eV (As , As4 + As,). For the vibrational frequencies of the Asn series, the BP86 and B3LYP methods produce good results compared with the limited experiments, so the other predictions with these methods should be reliable. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 907,920, 2004 [source] Molecules for materials: Germanium hydride neutrals and anions.JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2002Ge2Hn/Ge2H (n = 0, Molecular structures, electron affinities, thermochemistry of GeHn/GeH (n = 0 Abstract The GeHn (n = 0,4) and Ge2Hn (n = 0,6) systems have been studied systematically by five different density functional methods. The basis sets employed are of double-, plus polarization quality with additional s- and p-type diffuse functions, labeled DZP++. For each compound plausible energetically low-lying structures were optimized. The methods used have been calibrated against a comprehensive tabulation of experimental electron affinities (Chemical Reviews 102, 231, 2002). The geometries predicted in this work include yet unknown anionic species, such as Ge2H,, Ge2H, Ge2H, Ge2H, and Ge2H. In general, the BHLYP method predicts the geometries closest to the few available experimental structures. A number of structures rather different from the analogous well-characterized hydrocarbon radicals and anions are predicted. For example, a vinylidene-like GeGeH structure is the global minimum of Ge2H. For neutral Ge2H4, a methylcarbene-like HGë-GeH3 is neally degenerate with the trans -bent H2GeGeH2 structure. For the Ge2H anion, the methylcarbene-like system is the global minimum. The three different neutral-anion energy differences reported in this research are: the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). For this family of molecules the B3LYP method appears to predict the most reliable electron affinities. The adiabatic electron affinities after the ZPVE correction are predicted to be 2.02 (Ge2), 2.05 (Ge2H), 1.25 (Ge2H2), 2.09 (Ge2H3), 1.71 (Ge2H4), 2.17 (Ge2H5), and ,0.02 (Ge2H6) eV. We also reported the dissociation energies for the GeHn (n = 1,4) and Ge2Hn (n = 1,6) systems, as well as those for their anionic counterparts. Our theoretical predictions provide strong motivation for the further experimental study of these important germanium hydrides. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 1642,1655, 2002 [source] A post-SCF quantum chemistry study on local minima of 8-oxo-guanine stacked with all four nucleic acid bases in B-DNA conformationsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2007Piotr Cysewski The post SCF MP2/6-31G*(d=0.25) method was applied to obtain potential energy surface of 8-oxoguanine stacked with all four canonical DNA bases. The spatial neighbourhood was scanned of stacked complexes found in the native B-DNA. The presented results suggest that the hydroxyl radical modification of guanine at C8 position has significant impact on structural, energetic, orbital and electrostatic properties of stacked complexes with canonical DNA bases. The pair stabilization energy, including electron correlation terms, suggests that the 5,-A/GA-3, pair is the most stable among all of the studied complexes. The 8-oxo-guanine has been found as a source of significant changes in electroaccepting properties compared to stacked pairs formed by canonical guanine since both electron affinities and localization of HOMO orbital were altered. However, electro-donation abilities are not modified after replacement of guanine with 8-oxo-guanine irrespectively on the context of B-DNA bases. [source] Determination of the electron affinities of ,- and ,-naphthyl radicals using the kinetic method with full entropy analysis.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2001H bond dissociation energies of naphthalene, The C Abstract The C , H bond dissociation energies for naphthalene were determined using a negative ion thermochemical cycle involving the gas-phase acidity (,Hacid) and electron affinity (EA) for both the ,- and ,-positions. The gas-phase acidity of the naphthalene ,- and ,-positions and the EAs of the ,- and ,-naphthyl radicals were measured in the gas phase in a flowing afterglow,triple quadrupole apparatus. A variation of the Cooks kinetic method was used to measure the EAs of the naphthyl radicals by collision-induced dissociation of the corresponding ,- and ,-naphthylsulfinate adducts formed by reactions in the flow tube portion of the instrument. Calibration references included both , and , radicals, and full entropy analysis was performed over a series of calibration curves measured at collision energies ranging from 3.5 to 8 eV (center-of-mass). The measured EAs are 33.0 ± 1.4 and 31.4 ± 1.0 kcal mol,1 (1 kcal = 4.184 kJ) for the ,- and ,-naphthyl radicals, respectively. The gas-phase acidities for naphthalene were measured by the DePuy silane cleavage method, which utilizes the relative abundances of aryldimethylsiloxides and trimethylsiloxide that result from competitive cleavages from a proposed pentacoordinate hydroxysiliconate intermediate. The measured acidities are 394.0 ± 5.0 and 397.6 ± 4.8 kcal mol,1 for the ,- and ,- positions, respectively. The C , H bond dissociation energies calculated from the thermochemical cycle are 113.4 ± 5.2 and 115.4 ± 4.9 kcal mol,1 for the ,- and ,-positions, respectively. These energies are, to within experimental error, indistinguishable and are approximately the same as the first bond dissociation energy for benzene. Copyright © 2001 John Wiley & Sons, Ltd. [source] Substituent effect on electron affinity, gas-phase basicity, and structure of monosubstituted propargyl radicals and their anions: a theoretical studyJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2010Gab-Yong Lee Abstract The substituent effect of electron-withdrawing groups on electron affinity and gas-phase basicity has been investigated for substituted propargyl radicals and their corresponding anions. It is shown that when a hydrogen of the , -CH2 group or acetylenic CH in the propargyl system is substituted by an electron-withdrawing substituent, electron affinity increases, whereas gas-phase basicity decreases. The calculated electron affinities are 0.95,eV (CHCCH2,), 1.15,eV (CHCCHF,), 1.38,eV (CHCCHCl,), 1.48,eV (CHCCHBr,) for the isomers with terminal CH and 1.66,eV (CFCCH2,), 1.70,eV (CClCCH2,), 1.86,eV (CBrCCH2,) for the isomers with terminal CX at B3LYP level. The calculated gas-phase basicities for their anions are 378.4,kcal/mol (CHCCH2:,), 371.6,kcal/mol (CHCCHF:,), 365.1,kcal/mol (CHCCHCl:,), 363.5,kcal/mol (CHCCHBr:,) for the isomers with terminal CH and 362.6,kcal/mol (CFCCH2:,), 360.4,kcal/mol (CClCCH2:,), 356.3,kcal/mol (CBrCCH2:,) for the isomers with terminal CX at B3LYP level. It is concluded that the larger the magnitude of electron-withdrawing, the greater is the electron affinity of radical and the smaller is the gas-phase basicity of its anion. This tendency of the electron affinities and gas-phase bacisities is greater in isomers with the terminal CX than isomers with the terminal CH. Copyright © 2009 John Wiley & Sons, Ltd. [source] Theoretical design study on multifunctional triphenyl amino-based derivatives for OLEDsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2009Lu-Yi Zou Abstract The use of triphenyl amino-based derivatives in organic light-emitting diodes (OLEDs) can significantly improve their efficiency and stability and especially their electroluminescence characteristics , most of the new hole-transport materials have this feature. In this study, a series of triphenyl amino-based compounds were computed, including two newly designed molecules. They can function as charge transport materials and emitters with high efficiency and stability. To reveal the relationship between the properties and structures of these bifunctional and multifunctional electroluminescent materials, the ground and excited state geometries were optimized at the B3LYP/6-31G(d), HF/6-31G(d), TD-B3LYP/6-31G(d), and CIS/6-31G(d) levels, respectively. The ionization potentials (IPs) and electron affinities (EAs) were computed. The lowest excitation energies, the maximum absorption, and emission wavelengths of these compounds were calculated by employing the time-dependent density functional theory (TD-DFT) method. Also, the mobilities of holes and electrons were studied computationally based on the Marcus electron transfer theory. The CH2Cl2 solvent effect on the absorption spectra of N,N,-di-1-naphthyl- N,N,-diphenylbenzidine (NPB) was considered by polarizable continuum model (PCM). The results obtained for these compounds are in good agreement with the experimental values. These data show that the proposed compounds 1 and 2 (N,B-di-1-naphthyl-N,B-diphenylbenzidine and Mes2N[p-4,4,-biphenyl-NPh(1-naphthyl)]), are multifunctional and bifunctional materials similar to Mes2B[p -4,4,-biphenyl-NPh(1-naphthyl)] (BNPB) and NPB, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hydrogenation and oxygenation of the (100) diamond surface and the consequences for transfer dopingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2005S. J. Sque Abstract Ab initio density-functional-theory calculations have been performed to determine the structural and electronic properties of the (100) diamond surface with various hydrogen and oxygen terminations. Total energies indicate that an ,OH-terminated surface is favoured over an oxygenated surface plus gas-phase hydrogen. Ionisation potentials and electron affinities (EAs) are reported for the different systems, and the distinction is made between bulk- and surface-related properties. A first-order correction is used to offer estimated surface EAs. A negative bulk EA is found for surfaces terminated with ,H and ,OH groups, although many surfaces have deep traps which can act as positive EA in the absence of band bending. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrochemical Properties and Computations of Stable Radicals of the Heavy Group,14 Elements (Si, Ge, and Sn)CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2009James Abstract A series of stable radicals centered on persilyl-substituted heavy Group,14 elements, (tBu2MeSi)3E. (E=Si, Ge, Sn), was studied by cyclic voltammetry in different solvents to determine their first oxidation and reduction potentials and to compare their ease of oxidation and reduction with known experimental and computed ionization energies (Ei) and electron affinities (Eea), respectively. It has been observed that all of the first oxidation and reduction potentials for the three radicals studied are irreversible in o -dichlorobenzene (o -DCB), whereas the reduction waves are quasi-reversible in THF. A good correlation has been found between measured oxidation potentials and ionization energy values, but no correlation between reduction potentials and electron affinity values was found, probably due to kinetic and surface effects. [source] Comprehensive Analysis of DNA Strand Breaks at the Guanosine Site Induced by Low-Energy Electron AttachmentCHEMPHYSCHEM, Issue 1 2010Jiande Gu Prof. Dr. Abstract To elucidate the role of guanosine in DNA strand breaks caused by low-energy electrons (LEEs), theoretical investigations of the LEE attachment-induced CO ,-bonds and N-glycosidic bond breaking of 2,-deoxyguanosine-3,,5,-diphosphate (3,,5,-dGMP) were performed using the B3LYP/DZP++ approach. The results reveal possible reaction pathways in the gas phase and in aqueous solutions. In the gas phase LEEs could attach to the phosphate group adjacent to the guanosine to form a radical anion. However, the small vertical detachment energy (VDE) of the radical anion of guanosine 3,,5,-diphosphate in the gas phase excludes either CO bond cleavage or N-glycosidic bond breaking. In the presence of the polarizable surroundings, the solvent effects dramatically increase the electron affinities of the 3,,5,-dGDP and the VDE of 3,,5,-dGDP,. Furthermore, the solvent,solute interactions greatly reduce the activation barriers of the CO bond cleavage to 1.06,3.56 kcal,mol,1. These low-energy barriers ensure that either C5,O5, or C3,O3, bond rupture takes place at the guanosine site in DNA single strands. On the other hand, the comparatively high energy barrier of the N-glycosidic bond rupture implies that this reaction pathway is inferior to CO bond cleavage. Qualitative agreement was found between the theoretical sequence of the bond breaking reaction pathways in the PCM model and the ratio for the corresponding bond breaks observed in the experiment of LEE-induced damage in oligonucleotide tetramer CGTA. This concord suggests that the influence of the surroundings in the thin solid film on the LEE-induced DNA damage resembles that of the solvent. [source] N -Acetylation as a Means to Activate Polyfluoroarylamines for Selective ortho -Hydrodefluorination by Zinc in Aqueous Ammonia: A Concise Route to Polyfluorobenzo Azaheterocycles,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2007Sergey S. Laev Abstract N -Acetylation of polyfluoroarylamines is proposed as a meansto remove the amino group blocking effect of their hydrodefluorination by zinc in aqueous ammonia. With pentafluoroacetanilide, the Zn ion specific effect has been demonstrated to be responsible for ortho hydrodefluorination. This regiochemistry is accompanied by the removal of a fluorine atom from the para position, which occurs predominantly in the initial phase of the process in the absence of deliberately added zinc salt. The CuCl2 additive has been found to accelerate the reaction and to propel it to double defluorination. Quantum chemical calculations suggest a diminished electron affinity of pentafluoroaniline, which is responsible for its inertness in relation to the hydrodefluorination reaction. The pentafluoroaniline radical anion, which essentially has a nonplanar structure, is prone to easy fragmentation to give an aminotetrafluorophenyl radical. For pentafluoroacetanilide, CVA experiments and quantum chemical calculations predict that the pentafluorophenyl moiety serves as the electron receptor and that the acetamido group is twisted out of coplanarity with the benzene ring; thus, together with the electron-withdrawing effect of the acetyl group, the amino group blocking effect is suppressed. On this ground, the selective ortho hydrodefluorination of polyfluoroacetanilides is developed as an important protocol for the expeditious and general synthesis of polyfluorobenzo azaheterocycles via readily accessible polyfluoroarylamines from base polyfluoroarenes. Its applicability has been illustrated by preparing quinolines that possess a polyfluorinated benzene moiety by the Skraup synthesis utilizing crude polyfluoroacetanilide hydrodefluorination products as starting materials. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Triplet Formation in Fullerene Multi-Adduct Blends for Organic Solar Cells and Its Influence on Device PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Clare Dyer-Smith Abstract In organic solar cells, high open circuit voltages may be obtained by choosing materials with a high offset between the donor highest occupied molecular orbital (HOMO) and acceptor lowest unoccupied molecular orbital (LUMO). However, increasing this energy offset can also lead to photophysical processes that compete with charge separation. In this paper the formation of triplet states is addressed in blends of polyfluorene polymers with a series of PCBM multi-adducts. Specifically, it is demonstrated that the formation of such triplets occurs when the offset energy between donor ionization potential and acceptor electron affinity is ,1.6 eV or greater. Spectroscopic measurements support a mechanism of resonance energy transfer for triplet formation, influenced by the energy levels of the materials, but also demonstrate that the competition between processes at the donor,acceptor interface is strongly influenced by morphology. [source] Electron-Rich Alcohol-Soluble Neutral Conjugated Polymers as Highly Efficient Electron-Injecting Materials for Polymer Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Fei Huang Abstract We report the design and synthesis of three alcohol-soluble neutral conjugated polymers, poly[9,9-bis(2-(2-(2-diethanolaminoethoxy) ethoxy)ethyl)fluorene] (PF-OH), poly[9,9-bis(2-(2-(2-diethanol-aminoethoxy)ethoxy)ethyl)fluorene- alt -4,4,-phenylether] (PFPE-OH) and poly[9,9-bis(2-(2-(2-diethanolaminoethoxy) ethoxy)ethyl)fluorene- alt -benzothiadizole] (PFBT-OH) with different conjugation length and electron affinity as highly efficient electron injecting and transporting materials for polymer light-emitting diodes (PLEDs). The unique solubility of these polymers in polar solvents renders them as good candidates for multilayer solution processed PLEDs. Both the fluorescent and phosphorescent PLEDs based on these polymers as electron injecting/transporting layer (ETL) were fabricated. It is interesting to find that electron-deficient polymer (PFBT-OH) shows very poor electron-injecting ability compared to polymers with electron-rich main chain (PF-OH and PFPE-OH). This phenomenon is quite different from that obtained from conventional electron-injecting materials. Moreover, when these polymers were used in the phosphorescent PLEDs, the performance of the devices is highly dependent on the processing conditions of these polymers. The devices with ETL processed from water/methanol mixed solvent showed much better device performance than the devices processed with methanol as solvent. It was found that the erosion of the phosphorescent emission layer could be greatly suppressed by using water/methanol mixed solvent for processing the polymer ETL. The electronic properties of the ETL could also be influenced by the processing conditions. This offers a new avenue to improve the performance of phosphorescent PLEDs through manipulating the processing conditions of these conjugated polymer ETLs. [source] Quantum-Chemical Characterization of the Origin of Dipole Formation at Molecular Organic/Organic InterfacesADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Igor Avilov Abstract Recent experiments have reported a vacuum level shift at the interface between organic materials due to the formation of an interface dipole layer. On the basis of quantum-chemical calculations, this paper sheds light on the factors contributing to the formation of an interface dipole between an electron donor and an electron acceptor, considering as model system a complex made of tetrathiafulvalene (TTF) as a donor and tetracyanoquinodimethane (TCNQ) as an acceptor. The results indicate that the interface dipole is governed both by charge-transfer and polarization effects and allow for disentangling of their respective contributions. Two regimes of charge transfer can be distinguished depending on the strength of the electronic coupling: a fractional charge transfer occurs in the strong coupling regime while only integer charges are transferred when the coupling is weak. The polarization contribution can be significant, even in the presence of a pronounced charge transfer between the donor and acceptor molecules. The values of ionization potential and electron affinity of the donor and acceptor molecules may experience shifts as large as several tenths of an eV at the interface with respect to the isolated compounds. [source] Organic Thin-Film Photovoltaic Cells Based on Oligothiophenes with Reduced Bandgap,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007C. Uhrich Abstract The best polymeric solar cells reported so far are based on a so-called bulk heterojunction of a polythiophene as donor and a soluble fullerene derivative as acceptor. However, these cells still suffer from an unsatisfying photovoltage, typically below 0.7,V. Here, we show that we can achieve higher photovoltages using a new terthiophene end-capped with electron withdrawing dicyanovinyl groups (DCV3T) that increase both the ionization energy and even more strongly the electron affinity of the compound. The new material is tested in cells using a photoactive heterojunction to separate the excitons generated in the oligomer and a p-doped wide-gap transport layer. The solar cells show an open circuit voltage of up to 1.04,V and a broad spectral sensitivity band ranging from 420,nm to 650,nm. Solar cells based on such oligothiophenes are promising candidates for stacked organic solar cells tailored to the sun-spectrum. Moreover, we present first examples of a new concept for organic solar cells: By blending DCV3T with fullerene C60, an enhanced generation of triplet excitons on the oligomer can be achieved via a back and forth transfer of excitons (ping-pong-effect). [source] V-Shaped Thiophene-Based Oligomers with Improved Electroluminescence Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2005G. Barbarella Abstract The synthesis via the Stille coupling of a new family of oligomers derived from benzo[b]thiophene is reported. Owing to their branched molecular structure lacking any symmetry element, these compounds display a low tendency to crystallization and better film-forming properties than their linear counterparts. Spin-coated films show photoluminescence efficiencies up to 50,%. Light-emitting diodes with spin-coated films as the active layers display markedly improved performance with respect to similar devices based on linear oligothiophenes, with luminance values up to more than 10,000,cd,m,2. Semiempirical PM3 and ZINDO/S calculations provide insight into the molecular geometries and electron distribution of the frontier orbitals of the new compounds. Cyclic voltammetry data indicates that the transformation of the thienyl sulfur of benzo[b]thiophene to the corresponding thienyl- S,S -dioxide leads an increase in electron affinity by 0.5,0.7,V, analogous to that of the corresponding linear oligomers. [source] White Electroluminescence from a Phosphonate-Functionalized Single-Polymer System with Electron-Trapping EffectADVANCED MATERIALS, Issue 36 2009Xin Guo A novel strategy for obtaining white electroluminescence (EL) is based on the mechanism of electron trapping on host. Phosphonate-functionalized polyfluorene is chosen as host owing to its strong electron affinity. Electrons are confined mostly by host pendants in the EL process, which suppresses charge transfer from host to dopant. White EL with CIE coordinates of (0.34,0.35) is achieved. [source] Nanotechnologies: Tools for sustainability in a new wave of water treatment processesINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 4 2006Jean-Yves Bottero Abstract In the environmental technology industry alone, nanomaterials will enable new means of reducing the production of industrial wastes, using resources more sparingly, remediating industrial contamination, providing potable water, and improving the efficiency of energy production. This paper discusses three new kinds of nanotechnology materials that should be developed in the future: Membranes, oxidants, and adsorbents. Nanoscale control of membrane architecture may yield membranes of greater selectivity and lower cost in both water treatment and water fabrication. Fullerene-based oxidant nanomaterials such as C60 have a high electron affinity and reactivity, and are capable of producing reactive oxygen species such as singlet oxygen and superoxides. Fullerenes might be used in engineered systems to photocatalytically oxidize organic contaminants, or inhibit or inactivate microbes. The ability to tailor surfaces can help to increase adsorbing capacities or recognize specific contaminants. The potential environmental risks are that nanomaterials could interact with biota and that their toxicity adversely may affect ecosystems. As nanochemistry emerges as an important force behind new environmental technologies, we are also presented with the responsibility of considering the environmental implications of an emerging technology at its inception and taking every precaution to ensure that these technologies develop as tools of sustainability rather than becoming future liabilities. [source] Nonrelativistic CI calculations for B+, B, and B, ground statesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2010César X. Almora-Díaz Abstract State of the art configuration interaction (CI) techniques are used to obtain the best possible nonrelativistic CI results for B+, B, and B, ground states using energy-optimized basis sets of 252, 294, and 294 radial Slater-type functions, respectively. For positive boron, E(B+) = ,24.348861 + ,Ebie = ,24.348883(1) a.u.(B) with a basis set incompleteness error ,Ebie = ,0.000022(1), in good agreement with the latest exponentially correlated Gaussian (ECG) result of ,24.348883 a.u.(B) of Komasa et al. (Phys Rev A, 2002, 65, 042507). For neutral B, E(B) = ,24.653837 ,0.000024(2) = ,24.653861(2), which is the most accurate ab initio estimate and lies slightly below a recent (not fully optimized) ECG result of ,24.653840 a.u.(B) of Bubin et al (J Chem Phys, 2009, 131, 044128). For negative boron, E(B,) = ,24.664014 ,0.000024(2) to which an energy error of ,0.000001 must be added to give ,24.664039(2), which is the first fully correlated ab initio result. Comparison with experimental values of ionization energy and electron affinity must await the results of corresponding relativistic calculations, in progress. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Theoretical studies of some sulphonamides as corrosion inhibitors for mild steel in acidic mediumINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2010Eno E. Ebenso Abstract Density functional theory (DFT) at the B3LYP/6-31G (d,p) and BP86/CEP-31G* basis set levels and ab initio calculations using the RHF/6-31G (d,p) methods were performed on four sulfonamides (namely sulfaacetamide (SAM), sulfapyridine (SPY), sulfamerazine (SMR), and sulfathiazole (STI)) used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies (%IE). The order of inhibition efficiency obtained was SMR > SPY > STI > SAM which corresponded with the order of most of the calculated quantum chemical parameters namely EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), the energy gap (,E), the Mulliken charges on the C, O, N, S atoms, hardness (,), softness (S), polarizability (,), dipole moment (,), total energy change (,ET), electrophilicity (,), electron affinity (A), ionization potential (I), the absolute electronegativity (,), and the fraction of electrons transferred (,N). Quantitative structure activity relationship (QSAR) approach has been used and a correlation of the composite index of some of the quantum chemical parameters was performed to characterize the inhibition performance of the sulfonamides studied. The results showed that the %IE of the sulfonamides was closely related to some of the quantum chemical parameters but with varying degrees/order. The calculated %IE of the sulfonamides studied was found to be close to their experimental corrosion inhibition efficiencies. The experimental data obtained fits the Langmuir adsorption isotherm. The negative sign of the EHOMO values and other thermodynamic parameters obtained indicates that the data obtained supports physical adsorption mechanism. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] | ||||||||||||||||||||||||||||||||||