电子传输材料噻二唑衍生物的密度泛函研究

用密度泛函B3LYP方法对7种3-(3'-吡啶基)-6-芳基-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑分子进行全优化, 所有化合物都是平面分子. 计算了分子的垂直电子亲和势(VEA)、绝热电子亲和势(AEA)、分子内重组能以及绝对硬度等相关能量, 结果显示化合物的HOMO 与LUMO能级可通过连接不同取代基进行调节, 变化幅度为0.346～1.10 eV. 分子内重组能证实3-(4'-氰基-3'-吡啶基)-6-芳基-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑是很有前途的电子传输材料, 不同取代基所对应的化合物分子内重组能也不同. 绝对硬度数据与分子内重组能都表明, 化合物E, G难于传输电子. 用TDDFT方法计算了化合物A, B和C的吸收光谱, 与实验值相比, 最大吸收峰的差值在3～10 nm之间.     

Cyanation: providing a three-in-one advantage for the design of n-type organic field-effect transistors

The theoretical work presented here demonstrates that, when substitution takes place at appropriate positions, cyanation could be a useful tool for reducing the internal reorganization energy of molecules. A molecular-orbital-based explanation is given for this fundamentally important phenomenon. Some of the cyanated pentacene derivatives (nCN-PENT-n) not only have internal reorganization energies for electron transfer (lambda(-)) smaller than that of pentacene, but the lambda(-) values are even of the same magnitude as the internal reorganization energy for hole transfer (lambda(+)) of pentacene, a small value that few organic compounds have surpassed. In addition, cyanation raises the electron affinity of the parent compound and may afford good electronic couplings between neighboring molecules, because of its ability in promoting pi-stacking. For the design of high performance n-Type Organic field-effect transistors, high electron affinities, large intermolecular electronic couplings, and small reorganization energies are necessary. Cyanation may help in all three aspects. Two cyanated trialkylsilylethynyl pentacene derivatives with known pi-stacking structures are predicted to provide reasonably small internal reorganization energies, large electronic couplings, and high electron affinities. They have the potential to outperform N-fluoroalkylated dicyanoperylene-3,4:9,10-bis(dicarboximides) (PDI-FCN(2)) in terms of electron mobility.     

Probing the electronic structure and property of neutral and charged arsenic clusters (As(n)(+1,0,-1), n≤8) using Gaussian-3 theory

The structures and energies of As(n) (n = 2-8) neutrals, anions, and cations have been systematically investigated by means of the G3 schemes. The electron affinities, ionization potentials, binding energies, and several dissociation energies have been calculated and compared with limited experimental values. The results revealed that the potential surfaces of neutral As(n) clusters are very shallow, and two types of structural patterns compete with each other for the ground-state structure of As(n) with n ≥ 6. One type is derived from the benzvalene form of As(6), and another is derived from the trigonal prism of As(6). The previous photoelectron spectrum (taken from J. Chem. Phys. 1998 , 109 , 10727 ) for As(3) has been reassigned in light of the G3 results. The experimental electron affinities of As(3) were measured to be 1.81 eV, not 1.45 eV. We inferred from the conclusion of G3 and density functional theory that the experimental electron affinities of 1.7 and 3.51 eV for As(5) are unreliable. The reliable electron affinities were predicted to be 0.83 eV for As(2), 1.80 eV for As(3), 0.54 eV for As(4), 3.01 eV for As(5), 2.08 eV for As(6), 2.93 eV for As(7), and 2.02 eV for As(8). The G3 ionization potentials were calculated to be 9.87 eV for As(2), 7.33 eV for As(3), 8.65 eV for As(4), 6.68 eV for As(5), 7.97 eV for As(6), 6.58 eV for As(7), and 7.65 eV for As(8). The binding energies per atom were evaluated to be 1.99 eV for As(2), 2.01 eV for As(3), 2.61 eV for As(4), 2.39 eV for As(5), 2.51 eV for As(6), 2.55 eV for As(7), and 2.67 eV for As(8). These theoretical values of As(2), As(3), and As(4) are in excellent agreement with those of experimental results. Several dissociation energies were carried out to examine relative stabilities. This characterized the even-numbered clusters as more stable than the odd-numbered species.     

Hydrogen atom and hydride anion addition to adenine: structures and energetics.

The radicals and anions derived from the 9H tautomer of adenine by adding a hydrogen atom to one of the four double bonds of the adenine framework have been studied. Computations were carried out using a carefully calibrated density functional (B3LYP) method and basis set (DZP++). Optimized geometries, energies, and vibrational frequencies are predicted for eight radicals and anions. The radicals are found to lie in a range of 22 kcal mol(-1), with the radical derived by addition to the C(8) carbon atom being the lowest lying energetically. The anions are predicted to be bound species in the gas phase with an energetic range of 43 kcal mol(-1). Anions produced by addition of a hydride ion to adenine carbon atoms are found to be the most favorable. Six of the anions are predicted to be stable species with respect to electron detachment. The adiabatic electron affinities, vertical electron affinities, and vertical detachment energies are computed for the first time. Electron affinities for these radicals range from 0.0 to 2.0 eV. Radicals produced by addition to a nitrogen atom have near-zero adiabatic electron affinities, while radicals produced by addition at carbon atoms have considerably higher electron affinities.     

Reorganization energies of ferrocene-peptide monolayers

To deepen understanding of the electron transfer through a peptide backbone, we have investigated a series of noncyclic and cyclic ferrocene-peptide (Fc-peptide) cystamine conjugates immobilized on the gold microelectrode. Interaction of the ferrocenium group with BF4-, ClO4-, and PF6- as counterions was explored and the electron-transfer rates and reorganization energies were determined by variable temperature cyclic voltammetry. The highest reorganization energy was observed for the BF4- counterion, which has the weakest ability to associate with the ferrocenium cation. In addition, the more rigid cyclic Fc-peptide conjugates have a smaller reorganization energy ranging from 0.3 to 0.5 eV compared to less rigid noncyclic Fc-peptide cystamine conjugates which have higher reorganization energies in the range of 0.5-1.0 eV, which suggests that the dynamic properties of the conjugate play a role in mediating electron transfer in these systems.     

How dual bridging atoms tune structural and optoelectronic properties of ladder-type heterotetracenes?--a theoretical study

Ladder-type heterotetracenes possessing fully ring-fused structures are a promising class of optoelectronic materials in terms of the lack of any conformational disorder, intense emission and high carrier mobility. To uncover how dual bridging atoms tune their structural and optoelectronic properties, the heterotetracenes were systematically investigated by theoretical calculations from several aspects, such as (i) the geometrical structures of ground and excited states; (ii) the highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO); (iii) ionization potentials (IP), electron affinities (EA), hole extraction potentials (HEP), electron extraction potentials (EEP), internal reorganization energies (λ(int)) and transfer integrals (V); (iv) the absorption and emission spectra in vacuum and the dichloromethane (CH(2)Cl(2)) solvent, band gaps (E(g)), excitation energies at the lowest singlet (E(S1)) or triplet (E(T1)) states as well as radiative lifetimes (τ). The theoretical investigations may be useful for finding new leading materials and are likely to provide important information for improving their photoelectric performance.     

Electron attachment to dye-sensitized solar cell components: cyanoacetic acid

The energies of electron attachment associated with temporary occupation of the lower-lying virtual orbitals of cyanoacetic acid (CAA), proposed as a possible component of dye-sensitized solar cells, and its derivative methyl cyanoacetate (MCA) are measured in the gas phase with electron transmission spectroscopy (ETS). The corresponding orbital energies of the neutral molecule, supplied by B3LYP/6-31G(d) calculations and scaled using an empirically calibrated linear equation, are compared with the experimental vertical attachment energies (VAEs). The vertical and adiabatic electron affinities are also evaluated at the B3LYP/6-31+G(d) level as the anion/neutral total energy difference. Dissociative electron attachment spectroscopy (DEAS) is used to measure the total anion current as a function of the incident electron energy in the 0-4 eV energy range, and the negative fragments generated through the dissociative decay channels of the molecular anion are detected with a mass filter. In both compounds only two intense fragment anion currents are observed, that due to loss of a hydrogen atom from the molecular anion ([M - H](-)) and that due to formation of CN(-). In CAA the former signal displays a very sharp feature at 0.68 eV, assigned to a vibrational Feshbach resonance arising from coupling between a dipole bound anion state and a temporary σ* anion state.     

Theoretically Rational Designs of Transport Organic Semiconductors Based on Heteroacenes

A Marcus electron transfer theory coupled with an incoherent polaron hopping and charge diffusion model in combining with first‐principle quantum chemistry calculation was applied to investigating the effects of heteroatom on the intermolecular charge transfer rate for a series of heteroacene molecules. The influences of intermolecular packing and charge reorganization energy were discussed. It was found that the sulphur and nitrogen substituted heteroacenes were intrinsically hole‐transporting materials due to the reduced hole reorganization energy and the enhanced overlap between HOMOs. For the oxygen‐substituted heteroacene, it was found that both the electronic couplings and the reorganization energies for holes and electrons were comparative, indicating the application potential of ambipolar devices. Most interestingly, for the boron‐substituted heteroacenes, theoretical calculations predicted a promising electron‐transport material, which is rare for organic materials. These findings provide insights into rationally designing organic semiconductors with specific properties.     

DFT/TDDFT Studies on the Electronic Structures and Spectral Properties of Carbazole‐based Blue Light‐emitting Dendrimers

The purpose of this paper is to provide an in‐depth investigation of the electronic and optical properties of two series of carbazole‐based blue light‐emitting dendrimers, including 1 – 6 six oligomers. These materials show great potential for application in organic light‐emitting diodes as efficient blue‐light and red‐light emitting materials due to the tuning of the optical and electronic properties by the use of different electron donors (D) and electron acceptors (A). The geometric and electronic structures of these compounds in the ground state are calculated using density functional theory (DFT) and the ab initio HF, whereas the lowest singlet excited states were optimized by ab initio single excitation configuration interaction (CIS). All DFT calculations are performed using the B3LYP functional on 6‐31G* basis set. The outcomes show that the highest occupied molecular orbitals (HOMOs), lowest occupied molecular orbitals (LUMOs), energies gaps, ionization potentials, electron affinities and reorganization energies of each molecular are affected by different D and A moieties and different substitute positions.     

An inner-sphere reorganization model of hetero-exchange electron transfer reaction of diatomic reactants

An accurate theoretical scheme for obtaining directly the inner-sphere reorganization energies of the hetero-exchange electron transfer reactions from ionization potentials and electron affinities is first reported in this paper. Ionization potentials and electron affinities are alternatively obtained from the Rydberg spectroscopic data via a numerical procedure for some diatomic molecules. The inner-sphere reorganization energy values are calculated for the hetero-exchange electron transfer reactions (AB + CD⁺ → AB⁺ + CD) of diatomic molecules and are compared with those from other approximate methods.     

A Gaussian-3 theoretical study of small silicon-lithium clusters: electronic structures and electron affinities of SinLi(-) (n = 2-8)

The molecular structures of neutral Si n Li ( n = 2-8) species and their anions have been studied by means of the higher level of the Gaussian-3 (G3) techniques. The lowest energy structures of these clusters have been reported. The ground-state structures of neutral clusters are "attaching structures", in which the Li atom is bound to Si n clusters. The ground-state geometries of anions, however, are "substitutional structures", which is derived from Si n+1 by replacing a Si atom with a Li (-). The electron affinities of Si n Li and Si n have been presented. The theoretical electron affinities of Si n are in good agreement with the experiment data. The reliable electron affinities of Si n Li are predicted to be 1.87 eV for Si 2Li, 2.06 eV for Si 3Li, 2.01 eV for Si 4Li, 2.61 eV for Si 5Li, 2.36 eV for Si 6Li, 2.21 eV for Si 7Li, and 3.18 eV for Si 8Li. The dissociation energies of Li atom from the lowest energy structures of Si n Li and Si atom from Si n clusters have also been estimated respectively to examine relative stabilities.     

Photoionization and ab initio study of Ba(H2O)n (n = 1-4) clusters

An experimental and theoretical study of the photoionization energies (IE's) of Ba(H(2)O)(n) clusters containing up to n = 4 water molecules has been performed. The clusters were generated by a pick-up source combining laser vaporization with pulsed supersonic expansion, and then photoionized by radiation of 272.5-340 nm. The experimentally determined IE(e)'s for n = 1 to 4 are 4.56 ± 0.05, 4.26 ± 0.05, 3.90 ± 0.05 and 3.71 ± 0.05 eV. This cluster size dependence of IE is reproduced within ±0.06 eV employing the mPW1PW91 density-functional and CCSD(T, Full) quantum-chemical methods combined with the 6-311++G(d,p) basis set for the H and O atoms and three different relativistic effective core potentials for Ba atoms. The calculations indicate that the lowest energy hydration structures represent the most relevant contributions to both the vertical and adiabatic ionization energies. Experimental and theoretical evidence correlates with the progressive surface-delocalization of the electron from the hydration cavity around the Ba atom and suggests that the intra-cluster electron transfer is possible even for small aggregates.     

New relativistic ANO basis sets for transition metal atoms

New basis sets of the atomic natural orbital (ANO) type have been developed for the first, second, and third row transition metal atoms. The ANOs have been obtained from the average density matrix of the ground and lowest excited states of the atom, the positive and negative ions, and the atom in an electric field. Scalar relativistic effects are included through the use of a Douglas-Kroll-Hess Hamiltonian. Multiconfigurational wave functions have been used with dynamic correlation included using second order perturbation theory (CASSCF/CASPT2). The basis sets are applied in calculations of ionization energies, electron affinities, and excitation energies for all atoms and polarizabilities for spherically symmetric atoms. These calculations include spin-orbit coupling using a variation-perturbation approach. Computed ionization energies have an accuracy better than 0.2 eV in most cases. The accuracy of computed electron affinities is the same except in cases where the experimental values are smaller than 0.5 eV. Accurate results are obtained for the polarizabilities of atoms with spherical symmetry. Multiplet levels are presented for some of the third row transition metals.     

Calculations of ionization energies and electron affinities for atoms and molecules: A comparative study with different methods

In the present work, we examined the performance of 36 density functionals, including the newly developed doubly hybrid density functional XYG3 (Y. Zhang, X. Xu, and W. A. Goddard III, Proc. Natl. Acad. Sci, USA, 2009, 106, 4963), to calculate ionization energies (IEs) and electron affinities (EAs). We used the well-established G2-1 set as reference, which contains 14 atoms and 24 molecules for IE, along with 7 atoms and 18 molecules for EA. XYG3 leads to mean absolute deviations (MADs) of 0.057 and 0.080 eV for IEs and EAs, respectively, using the basis set of 6-311 + G (3df,2p). In comparison with some other functionals, MADs for IEs are 0.109 (B2PLYP), 0.119 (M06-2X), 0.159 (X3LYP), 0.161 (PBE), 0.162 (B3LYP), 0.165 (PBE0), 0.173 (TPSS), 0.200 (BLYP), and 0.215 eV (LC-BLYP). MADs for EAs are 0.090 (X3LYP), 0.090 (B2PLYP), 0.102 (PBE), 0.103 (M06-2X), 0.104 (TPSS), 0.105 (BLYP), 0.106 (B3LYP), 0.126 (LC-BLYP), and 0.128 eV (PBE0).     

苯-噻吩低聚物电子结构及载流子传输性质的理论研究

采用密度泛函理论(DFT)的B3LYP/6-31G(d)方法对以低聚噻吩为端基、 苯并二噻吩(TPT)和并三噻吩(TTT)为共轭桥、 炔键为连接臂的20个模型化合物进行了计算研究. 在优化中性与离子态几何构型基础上, 获得了前线轨道能级、 电离能(IPs)、 电子亲和势(EAs)、 空穴/电子重组能(λ_h/λ_e)、 载流子迁移率(μ_h/μ_e)及吸收光谱等信息. 结果表明, 炔键的引入及端基低聚噻吩的增加对LUMO能级的调控作用较为显著, 而共轭桥的类型对HOMO能级影响较大; 合理选择端基、 共轭桥和连接臂等结构单元可对该类材料吸光波段及强度进行有效调节. 一维电荷传输模型结果表明, 所设计的化合物均是潜在的双极性有机半导体材料, 其中2,7-二([2,2':5',2'-三噻吩]-5-基)苯并[1,2-b:6,5-b']二噻吩(A3)和2,7-二(二噻吩并噻吩-2-基乙炔基)苯并[1,2-b:6,5-b']二噻吩(a-3)具有较高的电子迁移率, 值得进一步的实验探索研究.     

Theoretical study on photophysical properties of multifunctional electroluminescent molecules with different pi-conjugated bridges

The photophysics of a series of molecular organic light-emitting diodes (OLEDs) has been studied by theoretical calculation. These molecular OLEDs have been integrated by an electron- and hole-transporting components as well as an emitting components into the donor-pi-acceptor (D-pi-A) structures: 2-carbazolyl-7-dimesitylboryl-9,9-diethylfluorene (1), trans-4'-N-carbazolyl-4-dimesitylborylstilbene (2), and trans-2-[(4'-N-carbazolyl)styryl]-5-dimesitylborylthiophene (3). To reveal the relationship between the structures and properties of these multifunctional electroluminescent materials, the ground- and excited-state geometries were optimized at the B3LYP/6-31G(d), HF/6-31G(d), and CIS/6-31G(d) levels, respectively. The ionization potentials and electron affinities were computed. The mobilities of hole and electron in these compounds were studied computationally based on the Marcus electron transfer theory. The lowest excitation energies (E(g)) and the maximum absorption and emission wavelengths of these compounds were calculated by time-dependent density functional theory methods. The solvent effect on the emission spectra of these compounds was considered by a polarizable continuum model. As a result of these calculations, it was concluded that the electron injections of these compounds are much easier than Mes(2)B[p-4,4'-biphenyl-NPh(1-naphthyl)], and the diethylfluorene-based compound has higher electron mobility and better equilibrium properties as compared to the stilbene-based and styrylthiophene-based compounds.     

Contemplation on Some Prismatic Polynitrogen Structures – A DFT Treatment

Polynitrogen compounds, are rare molecules having only nitrogen atoms. In recent years, they have been considered as promising candidates of clean (green) high energy density materials. They possess high energy content and their sole decomposition product is N₂. Presently some prismatic polynitrogen structures (N₆ – N₁₄) are considered within the limitations of density functional theory at the levels of B3LYP/6‐311++G(d,p) and B3LYP/cc‐PVTZ. The calculations reveal that they are all highly endothermic but stable. Certain quantum chemical properties, IR and UV/Vis spectra are reported. Homolytic bond cleavage of top rings are considered. Then, the transition state and activation energies, and also homolytic bond dissociation energies for the top rings have been calculated at the level of UB3LYP/6‐311++G(d,p). Also NICS(0) values have been calculated at the level of B3LYP/6‐311++G(d,p). The results indicate that N₆ and N₁₀ have aromatic and nonaromatic top (and also base) rings, respectively. All the rest of the structures have antiaromatic rings (all the structures have antiaromatic N₄ rings).     

Protonation processes and electronic spectra of histidine and related ions

A full structural assignment of the neutral, protonated, and deprotonated histidine conformers in the gas phase is presented. A total of 3024 unique trial structures were generated by all combinations of internal single-bond rotamers of these species and optimized at the B3LYP/6-311G* level and further optimized at the B3LYP/6-311++G** level. A set of unique conformers is found, and their relative energies, free energies, dipole moments, rotational constants, electron affinities, ionization energies, and harmonic frequencies are determined. The population ratio of histidine and its tautomer is 1:0.16 at 298 K. Massive conformational changes are observed due to protonation and deprotonation, and the intramolecular H-bonds are characterized with the atoms in molecules theory. The calculated proton dissociation energy, gas-phase acidity, proton affinity, and gas-phase basicity are in excellent agreement with the experiments. The deprotonation and protonation of gaseous histidine both occur on the imidazole ring, explaining the versatile biofunctions of histidine in large biomolecules. The UV spectra of neutral and singly and doubly protonated histidine are investigated with the TDDFT/B3LYP/6-311+G(2df,p) calculations. The S0-S1, S0-S2, and S0-S3 excitations of histidine are mixed pipi*/npi* transitions at 5.37, 5.44, and 5.69 eV, respectively. The three excitation energies for histidine tautomer are 4.85, 5.47, and 5.52 eV, respectively. The three excitations for protonated histidine are mainly npi* transitions at 5.45, 5.67, and 5.82 eV, respectively. The S0-S1 excitation of protonated histidine produces ImH-CbetaH2-CalphaH(COOH)-NH2+, while the S0-S2 and S0-S3 transitions produce ImH-CbetaH2-CalphaH(NH2)-(COOH)+. These data may help to understand the mechanisms of the UV fragmentation of biomolecules.     

Theoretical study of the stability and electronic structure of Al(BH4)n=1→4 and Al(BF4)n=1→4 and their hyperhalogen behavior

Using density functional theory (DFT), we have systematically calculated the equilibrium geometries, electronic structure, and electron detachment energies of Al(BH(4))(n=1→4) and Al(BF(4))(n=1→4) at the B3LYP/6-311+G(2d,p) level of theory. The electron affinities of Al(BH(4))(n) not only exhibit odd-even alternation, just as seen in (BH(4))(n), but also, for n = 3 and 4, show a remarkable behavior: whereas the electron affinities of BH(3) and BH(4) are, respectively, 0.06 and 3.17 eV, those of Al(BH(4))(3) and Al(BH(4))(4) are 0.71 and 5.56 eV. Results where H is replaced by F are also very different. The electron affinities of BF(3) and BF(4) are, respectively, -0.44 and +6.86 eV, and those of Al(BF(4))(3) and Al(BF(4))(4) are 1.82 and 8.86 eV. The results demonstrate not only marked difference when H is replaced by F but also substantially enhanced electron affinities by almost 2 eV when BH(4) and BF(4) units are allowed decorate a metal atom, confirming the recently observed hyperhalogen behavior of superhalogen building blocks.     

The 6-31B(d) basis set and the BMC-QCISD and BMC-CCSD multicoefficient correlation methods

Three new multicoefficient correlation methods (MCCMs) called BMC-QCISD, BMC-CCSD, and BMC-CCSD-C are optimized against 274 data that include atomization energies, electron affinities, ionization potentials, and reaction barrier heights. A new basis set called 6-31B(d) is developed and used as part of the new methods. BMC-QCISD has mean unsigned errors in calculating atomization energies per bond and barrier heights of 0.49 and 0.80 kcal/mol, respectively. BMC-CCSD has mean unsigned errors of 0.42 and 0.71 kcal/mol for the same two quantities. BMC-CCSD-C is an equally effective variant of BMC-CCSD that employs Cartesian rather than spherical harmonic basis sets. The mean unsigned error of BMC-CCSD or BMC-CCSD-C for atomization energies, barrier heights, ionization potentials, and electron affinities is 22% lower than G3SX(MP2) at an order of magnitude less cost for gradients for molecules with 9-13 atoms, and it scales better (N6 vs N,7 where N is the number of atoms) when the size of the molecule is increased.