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1.
Guochun Yang Yanling Si Yun Geng Fei Yu Qingxiu Wu Zhongmin Su 《Theoretical chemistry accounts》2011,128(2):257-264
The charge transport and photophysical properties of N-heteroquinones, which can function as n-type organic semiconductors
in organic field-effect transistors (OFETs) with high electron mobility, were systematically investigated using hopping model,
band theory, and time-dependent density functional theory (TDDFT). The calculated absorption spectra and electron mobility
are in good agreement with experimental results. To the studied compounds, subtle structural modifications can greatly reduce
the reorganization energy. There are two main kinds of intermolecular interaction forces of the studied compounds in the crystal,
which result from intermolecular π–π and hydrogen bonds interactions, respectively. The results of hopping model show that
the electron transport properties are mainly determined by pathways containing intermolecular π–π interactions, and hole transport
properties are mainly determined by pathways containing intermolecular hydrogen bonds from the standpoint of transfer integral.
Moreover, electronic transfer integral value increases with the enhancement of intermolecular overlap corresponding to the
overlap extent of π–π packing. Hole transfer integral value decreases with decreasing the number of hydrogen bonds. This means
that charge transport properties can be efficiently tuned by controlling the relative positions of the molecules and the number
of hydrogen bonds. The analysis of band structure also supports the conclusion of hopping model. 相似文献
2.
The geometry and electronic structure of 1,4-di(silaethen-1-yl)benzene (2), itsmeta- andbrtho-isomers (3 and4, respectively), and its carbon analog, 1,4-divinylbenzene (5), were studied by the semiempirical MNDO-PM3 method. Unlike5, two pairs of the frontier MOs in isomers2–4 are mainly π-orbitals of Si=C bonds, while the structure of the lowest occupied π-MO indicates delocalization of π-electrons
of the entire system. The main characteristic features of the double Si=C bonds (the high polarity and narrow HOMO-LUMO energy
gap, which favors the [2+2]-cycloaddition reaction) remain in arylsilenes2–4. The interaction between π-electrons of benzene fragment and the double Si=C bonds results in violation of the benzene ring
symmetry, which is most pronounced in structure5. Weakening of the C−H bonds in theortho-positions of the aromatic nucleus in the compounds under study is observed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 256–260, February, 1999. 相似文献
3.
R. S. Rathore K. Sathiyanarayanan N. S. Karthikeyan P. G. Aravindan 《Structural chemistry》2010,21(5):909-914
Derivatives of azabicyclo[3.3.1]nonanone tend to prefer for weak interactions in the crystal over strong N–H···O hydrogen
bonds. The main stabilizing forces in the investigated azatricyclo[7.3.1.02,7]trideca-trienone derivatives are C–H···O, N–H···π and C–H···π interactions, leading to interesting structural patterns. The
azabicyclo[3.3.1]nonanone ring adopts chair-envelope conformation having exo-C2,C4-aromatic substituents. Amino NH is in trigonal
pyramidal configuration. The interesting stereochemistry of azabicyclo[3.3.1]nonanone, driving exceptional preference for
weaker interactions over strong hydrogen bonds serves a useful example toward engineering and design strategy, and structure
prediction methodologies. 相似文献
4.
Gökhan Alpaslan Hasan Tanak Ayşen Alaman Ağar Ahmet Erdönmez Şamil Işık 《Structural chemistry》2010,21(5):1027-1036
The Schiff base compound (E)-2-(1-(2-(4-methylphenylsulfonamido)ethyliminio)ethyl) phenolate has been synthesised and characterized
by IR, UV–Vis, and X-ray single-crystal determination. Ab initio calculations have been carried out for the title compound
using the density functional theory (DFT) and Hartree–Fock (HF) methods at 6-31G(d) basis set. The calculated results show
that the DFT/B3LYP and HF can well reproduce the structure of the title compound. Using the TD-DFT and TD-HF methods, electronic
absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental
ones is determined. Molecular orbital coefficient analyses reveal that the electronic transitions are mainly assigned to n → π* and π → π* electronic transitions. To investigate the tautomeric stability, optimization calculations at B3LYP/6-31G(d)
level were performed for the NH and OH forms of the title compound. Calculated results reveal that the OH form is more stable
than NH form. In addition, molecular electrostatic potential and NBO analysis of the title compound were performed at B3LYP/6-31G(d)
level of theory. 相似文献
5.
Nikolai A. Ustynyuk Oleg V. Gusev Lyudmila N. Novikova Mikhail G. Peterleitner Larisa I. Denisovich Tat’yana A. Peganova Oleg V. Semeikin Dmitry A. Valyaev 《Journal of Solid State Electrochemistry》2007,11(12):1621-1634
In this review, redox-induced reactions of π- and σ,π-complexes leading to the selective formation (or cleavage) of C–H, C–C,
and C–O bonds have been summarized. To illustrate the synthetic potential of such methodology, the following representative
reactions studied in our group are discussed: (1) oxidatively induced hydrogen elimination from “open” cyclic diene and dienyl
complexes resulting in formation of “closed” dienyl and arene complexes, respectively; (2) reductive activation of C–H bonds
in diene, vinylidene, and carbyne complexes forming new multiple C–C bonds; (3) oxidative dehydrodimerization of vinylidene
complexes into binuclear μ-divinylidene species; and (4) oxidatively induced addition of oxygen nucleophiles to μ-divinylidene
complexes affording cyclic μ-dicarbene derivatives.
Oleg V. Gusev, deceased on October 31. 相似文献
6.
Weiliang Zhu Jiande Gu Hualiang Jiang Jianzhong Chen Dongxiang Liu Maowei Lin Kaixian Chen Ruyun Ji Yang Cao 《中国科学B辑(英文版)》1998,41(6):616-622
Quantum chemistry density-functional theory (DFT)B3LYP method with 6-31G basis set has been empolyed to study the electronic
structure and IR spectrum of Huperzine A. The calculation result showed that the characteristic of the predicted IR bands
was in general consistent with the experimental spectrum. 45 vibration modes were assigned clearly from the total of 102 vibration
bands. The strongest IR-intensive band corresponds to the stretching vibration of the C=O bond of the pyridone ring, and the
highest frequency band belongs to the pyridone N-H stretch. The investigation showed that the obvious differences between
the calculated bands and the experimental spectrum existed at the bands involving the hydrogen atoms of amino and pyridone
amide groups, which could form intermolecular hydrogen bond with other Huperzine A in the crystal structure. The hydrogen
bonds can not only affect the orientation of these hydrogen atoms, but also can affect the force property of the chemical
bond, which can change the vibrational frequencies.
Project supported by the “863” High Technology Program of China (No. 863-103-04-01) and the National Natural Science Foundation
of China (Grant No. 29403027). 相似文献
7.
Quantum chemical calculations using gradient-corrected density functional theory (B3LYP) and ab initio methods at the MP2
level are reported for the geometries and bond energies of the nitrido complexes Cl2 (PH3)3ReN–X (X = BH3, BCl3, BBr3, AlH3, AlCl3, AlBr3, GaH3, GaCl3, GaBr3, O, S, Se, Te). The theoretical geometries are in excellent agreement with experimental values of related complexes which
have larger phosphine ligands. The parent nitrido complex Cl2(PH3)3ReN is a very strong Lewis base. The calculated bond dissociation energy of Cl2(PH3)3ReN–AlCl3 is D
e = 43.7 kcal/mol, which is nearly as high as the bond energy of Me3N–AlCl3. The donor-acceptor bonds of the other Cl2(PH3)3ReN–AY3 complexes are also very strong. Even stronger N–X bonds are predicted for most of the nitrido-chalcogen complexes, which
exhibit the trend X = O ≫ S > Se > Te. Analysis of the electronic structure shows that the parent compound Cl2(PH3)3ReN has a Re–N triple bond. The Re–N σ bond is clearly polarized towards nitrogen, while the two π bonds are nearly nonpolar.
The Re–N σ and π bonds become more polarized toward nitrogen when a Lewis acid or a chalcogen atom is attached. Bonding in
AY3 complexes should be described as Cl2(PH3)3ReE≡N→AY3, while the chalcogen complexes should be written with double bonds Cl2(PH3)3Re=N=X. The charge-decomposition analysis indicates that the nitrogen-chalcogen bonds of the heavier chalcogen complexes with
X = S, Se, Te can also be interpreted as donor-acceptor bonds between the nitrido complex acting as a Lewis base and the chalcogen
atom with an empty p(σ) orbital acting as a Lewis acid. The nitrido oxo complex Cl2(PH3)3 Re=N=O has a covalent N–O double bond.
Received: 27 July 1998 / Accepted: 26 October 1998 / Published online: 16 March 1999 相似文献
8.
V. V. Zaitseva T. G. Tyurina A. V. Shtonda S. Yu. Zaitsev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(4):553-562
The self-association of styrene, acrylonitrile, methylmethacrylate, N-vinylpyrrolidone, and maleic anhydride molecules is
considered in dependence on the nature of the monomer, i.e., on the conjugation between functional groups. The AM1, Hartree-Fock
(RHF), and density functional theory (DFT) methods of calculation are used in our investigations. Charge distributions on
the atoms of interacting groups and contributions from overlapping molecular orbitals to the energy of formation of self-associates
are found. The calculated parameters are compared with experimental data on absorption band shifts in IR spectra and on chemical
shifts ΔH and ΔC for the hydrogen and carbon atoms of =CH, =CH2, C=O groups of bound molecules in 1H and 13C NMR spectra. The formation of π-H, CH…O, and CH…N bonds is proved. Analysis of CCl4/monomer dependences shows that dimers are present in dilute solutions, while the presence of trimers in concentrated solutions
cannot be excluded. Self-association constants are determined along with the degree of self-association, which lies within
the range of 40–60% for 50 mol% of a monomer in solution. 相似文献
9.
Oleg S. Sukhanov Oleg V. Shishkin Leonid Gorb Jerzy Leszczynski 《Structural chemistry》2008,19(1):171-180
Abstract Molecular structure of complexes of guanine with 12, 13, 16, and 17 water molecules were calculated using B3LYP/6-311G(d,p)
level of theory. Interaction with water results in some deformation of geometrical parameters of guanine, which can be described
as contribution of zwitter-ionic resonant form into the structure of DNA base. Saturation of water binding sites within guanine
creates possibilities for the formation of the N···H–O hydrogen bond where the nitrogen atom of amino group acts as proton
acceptor. The NBO analysis of guanine–water interactions reveals that hydrogen bonds involving the N(3) and N(7) atoms of
guanine represent a case of mixed N···H–O/π···H–O hydrogen bonds where contribution of π-system into total energy of interaction
varies from 3% to 41%. This contribution significantly depends on orientation of the hydrogen atom of water molecule with
respect to plane of purine bicycle and influence of neighboring water molecules.
Graphical Abstract
相似文献
10.
The structure of tetraaqua-bis(nitrato-O,O′)-(1,10-phenanthroline-N,N′)-lanthanum(III) 1,3,5,7-tetraazatricyclo[3.3.1.13,7]decane nitrate dihydrate, [La(NO3)2 · phen · (H2O)4]+ · hmt · NO
3
−
· 2H2O, is presented. The lanthanum ion exhibits tenfold coordination and the polyhedron can be described as tetradecahedron. The
complex cations, nitrate ions, water and hexamethylenetetramine molecules are assembled via hydrogen bonds, H–π rings and π–π stacking interactions into 3D supramolecular network. The bond strength of coordination sphere was calculated by means of
the bond-valence method. The influence of La:phen stoichiometry and additional ligand on the changes of lanthanum(III) coordination
sphere geometry in ten-coordinated complexes with 1,10-phenanthroline was discussed. The infrared spectrum of structure optimised
by means of quantum mechanical calculations was analysed and compared with measured one. The obtained compound was characterised
by thermogravimetric analysis in conjunction with evolved gases in the air atmosphere. 相似文献
11.
Guang-Wen An Hong Zhang Xin-Lu Cheng Quan-Lu Zhuo Yi-Chao Lv 《Structural chemistry》2008,19(4):613-617
We study the density of state (DOS), band structure (BS), and atomic orbit projected density of state (PDOS) of paracetamol
crystal adopting the density functional theory (DFT) technique in the local density approximation (LDA). The band structure
around the Fermi level and the contributions from p-type orbit of C, N, O, and s-type orbit of H to the total density of state
(TDOS) are addressed, and we find that the electronic characteristic is the key to form the hydrogen bond between O and H
atoms. We show that the structure of paracetamol crystal consists of the –OH···O=C and –NH···OH hydrogen-bonding cycle by
studying a single paracetamol molecule as well as the PDOS graph of O and H atoms in the crystal. 相似文献
12.
G. N. Ten V. V. Nechaev V. I. Berezin V. I. Baranov 《Journal of Structural Chemistry》1997,38(2):268-276
The vibrational structure of the absorption spectra of the first two π-π* singlet transitions of adenine is calculated in
the Franck-Condon approximation including Herzberg-Teller interactions. The effect of excitation-induced changes in molecular
angles on the intensities of the vibrational components is estimated. Structural models of the adenine molecule in the excited
states are constructed. The theoretical and absorption spectra of the first π-π* transition are compared. The results of the
electronic structure calculations of adenine by different CNDO/S methods are discussed.
Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 2, pp. 334–344, March–April, 1997. 相似文献
13.
Conformational analysis of tyrosine (YN) and its ionized counter parts cations (YC), anions (YA) and biologically relevant zwitterionic form (YZ) has been carried out. An exhaustive and systematic exploration of l-tyrosine dimer (YD) conformations resulted in about 59 distinct minima on the potential energy surface. The hydrogen bonds and a variety of
non-covalent interactions such as OH–π, NH–π, CH–π, CH–O and π–π interactions stabilized the different forms of tyrosine and
its dimers. Atoms in molecules analysis was performed to evaluate the nature and strength of the non-covalent interactions.
Over all the NH–O, hydrogen bonds have showed higher stability than other non-covalent interactions in this study. The most
stable dimers predominantly possess hydrogen bonding interactions, while the ones with aromatic side chain interactions are
less stable. A delicate balance of non-covalent interactions governed the stability of different forms of tyrosine and its
dimers. 相似文献
14.
Jie Xu Hui Zhang Lei Wang Guijie Liang Luoxin Wang Xiaolin Shen Weilin Xu 《Monatshefte für Chemie / Chemical Monthly》2010,17(1):549-555
Abstract
The ground-state geometries, electronic structures, and electronic absorption spectra of symmetrical squaraine dyes SQ1–SQ4 were investigated using density functional theory and time-dependent DFT at the B3LYP level. The calculated geometries indicate that strong conjugation effects occur in the dyes. The highest occupied molecular orbital energy levels were calculated to be −4.95, −5.22, −5.09, and −5.06 eV, and the lowest unoccupied molecular orbital energies were −2.72, −3.05, −2.80, and −2.80 eV for SQ1–SQ4, respectively. Taking the conduction band energy of TiO2 into account, these data reveal the sensitized mechanism: the interfacial electron transfer between the semiconductor TiO2 electrode and the dye sensitizers SQ1–SQ4 are electron-injection processes from excited dyes to the semiconductor conduction band. The intense calculated absorption bands are assigned to π → π* transitions, which exhibit appreciable blue-shift compared with the experimental absorption maxima due to the inherent approximations in the TD-DFT. 相似文献15.
Karin Hofstetter Barbara Hinterstoisser Lennart Salmén 《Cellulose (London, England)》2006,13(2):131-145
This paper aims at a better understanding of the interaction between cellulose and moisture. In particular, the role of different
hydrogen bonds in moisture uptake is investigated. Dynamic Fourier transform infrared spectroscopy (FT-IR) has been used in
combination with deuterium exchange, which permits the labelling of cellulose domains with different accessibilities.
The static spectra indicate a marked exchange of deuterium for the O2–H⋯O6 bonds, but only a limited exchange for the O3–H⋯O5
bonds. In the dynamic FT-IR spectra, deuteration gives rise to the growth of a broad band at wavenumbers around 2500 cm−1. The rather unstructured appearance of the band suggests that deuteration is occurring only on the surface of the cellulose
crystallites, i.e. in more or less non-load-carrying parts. This is corroborated by the lack of split peaks related to OD
bonds in this band. In agreement with these observations, the split peak related to O3–H⋯O5 bonds and assigned to the load
carrying cellulose structure increases during both H2O and D2O moisture conditioning, indicating a shift of the load transfer towards the backbone of the cellulose structure. 相似文献
16.
N. I. Medvedeva V. P. Zhukov D. L. Novikov V. A. Gubanov 《Journal of Structural Chemistry》1996,37(1):41-50
The band structure of the fluorite-type δ-Bi2O3 was calculated by the linear LMTO methods in the approximation of overlapping atomic spheres using the basis set of orthogonal
orbitals (LMTO-ASA) and by the full-potential LMTO method (LMTO-FP) for two vacancy orientations over a wide range of oxygen
concentrations. The calculated parameters of chemical bonds—the binding energy Ebin and the pressure of the electron-nuclear system—show that the most stable compound is that with two vacancies per unit cell,
oriented predominantly along the (111) direction. The hybrid Bi−O bonds are weak, and mostly the Bi−Bi bonds are responsible
for the structural stabilization of δ-Bi2O3. The mechanism of the formation of a semiconductor gap in the band structure of δ-Bi2O3 is discussed.
Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 1, pp. 48–58, January–February, 1996.
Translated by I. Izvekova 相似文献
17.
Abstract
A new parametrization for the Harmonic Oscillator Model of Aromaticity (HOMA) index to determine aromaticity of heterocycles is introduced. The new HOMA for Heterocycle Electron Delocalization (HOMHED) is based on the experimental data from electron diffraction X-ray for the reference molecules used to estimate the simple, double, and optimal bond lengths. Bond length of “pure” single and double bonds of non-conjugated systems or systems without π-electrons and/or n-electron delocalization were considered. The HOMHED index was determined for a series of five and six heterocycles with C–C, C–N, C–O, C–S, N–N, N–O, and N–S bonds. The π-electron delocalization of these heterocycles was determined by Krygowski-reformulated HOMA and HOMHED and it was proved that HOMHED worked in line with HOMA for all heterocycles, except those containing oxygen, which were found to be weak aromatic from Krygowski rHOMA calculations. 相似文献18.
Jing-xiang Zhao Bo Gao Qing-hai Cai Xiao-guang Wang Xuan-zhang Wang 《Theoretical chemistry accounts》2011,129(1):85-92
Phenol adsorptions on solid surfaces have attracted considerable attention due to their potential applications. Through density
functional theory (DFT) methods, we study phenol adsorption on a semiconducting (8, 0) silicon carbide nanotube (SiCNT). We
find that the hydroxyl group of phenol prefers to attach to the Si atom of SiCNT. The calculated adsorption energy is −0.494 eV,
and 0.208 electrons are transferred from the adsorbate to the nanotube. Interestingly, the O–H bond of the adsorbed phenol
can be split on the SiCNT, in which the H atom of the O–H group in the phenol is transferred from the Si atom to its neighboring
C atom. Furthermore, we also explore the π–π interaction between the aromatic ring of the phenol and the hexagons of the SiCNT.
The calculated adsorption energy is about −0.285 eV with a neglectable charge transfer (0.064 e). On the basis of the calculated
band structures, we find that the electronic properties of the adsorbed SiCNT by the phenol are little changed. The present
results might be helpful not only to provide an effective way to convert or remove phenol but also to widen the application
fields of the SiCNT. 相似文献
19.
Rodrigo S. Corrêa Marcelo H. dos Santos Tanus J. Nagem Javier Ellena 《Structural chemistry》2010,21(3):555-563
Oxygenated xanthones have been extensively investigated over the years, but there are few reports concerning their crystal
structure. Our chemical investigations of Brazilian plants resulted in the isolation of four natural products named 1-hydroxyxanthone
(I), 1-hydroxy-7-methoxyxanthone (II), 1,5-dihydroxy-3-methoxyxanthone (III), and 1,7-dihydroxy-3,8-dimethoxyxanthone (IV).
The structures of these compounds were established on the basis of single crystal X-ray diffraction. The xanthone nucleus
conformation is essentially planar with the substituents adopting the orientations less sterically hindered. In addition,
classical intermolecular hydrogen bonds (O–H···O) present in III and IV give rise to infinite ribbons. However, the xanthone
I does not present any intermolecular hydrogen bonds, meanwhile the xanthone II presents only a non-classical one (C–H···O).
The crystal packing of all xanthone structures is also stabilized by π–π interactions. The fingerprint plots, derived from
the Hirshfeld surfaces, exhibited significant features of each crystal structures. 相似文献
20.
Hong-Zhen Xie Shi-Jie Huang Jin Zhou Shu-Ping Yu Dan-Yi Wei 《Transition Metal Chemistry》2010,35(7):773-778
Two coordination complexes, namely [Co(phen)(H2O)L]·H2O and [Ni2(phen)2(H2O)2L2]·4H2O (phen = 1,10-phenanthroline, H2L = 1,3-adamantanedicarboxylic acid) have been hydrothermally synthesized and structurally characterized by single crystal
X-ray diffraction. [Co(phen)(H2O)L]·H2O consists of 1D chains of the complex plus lattice H2O molecules. Interchain hydrogen bonds and π–π stacking interactions assemble the 1D chains into 2D layers. [Ni2(phen)2(H2O)2L2]·4H2O is a binuclear complex which is assembled into a 3D supramolecular structure by strong hydrogen bonds and π–π stacking interactions.
Both complexes were characterized by physico-chemical and spectroscopic methods. 相似文献