基于苯并噻二唑和硅芴的一系列红光材料的载流子传输性质及荧光性质(英文)

用密度泛函理论(DFT)方法研究了基于苯并噻二唑和硅芴的一系列聚合物的基态和激发态结构、传输和荧光性质.聚合物的能隙、电离能、电子亲和势、最低激发能以及吸收光谱通过外推法得到.结果表明空穴、电子注入和传输性质受苯并噻唑在硅芴上的位置以及正丁基在噻吩上的位置影响很大.(SiF2-DHTBT1-m)n和(SiF1-DHTBT1-m)n(SiF和DHTBT分别代表硅芴和4,7-二(2-噻吩基)-2,1,3-苯并噻二唑)表现出较好的空穴和电子注入性质,而(SiF1-DHTBT1-o)n和(SiF1-DHTBT1-p)n的电荷注入性质较差.除(SiF1-DHTBT1-o)n外,聚合物的荧光光谱处于红光范围.     

1,3-二氮杂薁类衍生物电子结构和光谱性质的理论研究

对1,3-二氮杂薁类衍生物采用密度泛函理论(DFT)在B3LYP/6-31G(d)的水平上进行了几何构型的全优化, 在此基础上探讨了分子结构和前线分子轨道能量等性质的变化规律, 采用含时密度泛函理论(TD-DFT)计算了分子的电子跃迁性质, 采用二维平面图和三维立体图来直观表示激发态的性质, 研究分子内电子转移特性. 跃迁密度矩阵的二维等高线图反映了电子-空穴相干性, 三维跃迁密度图反映了跃迁偶极矩的方向和强度, 三维电荷差异密度图说明了激发过程中分子内电子转移性质.     

给、吸电子基团封端对低聚9,9 -螺双芴光电性质的改进

采用密度泛函理论(DFT)-B3LYP/6-31G(d)方法研究了给、吸电子基团对称和不对称封端对9,9 -螺双芴光电性质的影响. 全优化得到了9,9 -螺双芴封端前后各分子的稳定构型, 分析了各种封端系列的HOMO-LUMO能隙. 结果表明, 以给电子基团噻吩和吸电子基团噁二唑不对称封端作用于9,9 -螺双芴, 能使LUMO能量大幅降低, HOMO能量略有升高, 能隙明显变窄. 不对称封端低聚9,9 -螺双芴分子[T(SBF)_nO, n＝1～4]在相同计算水平下的全优化结果表明吸、给电子基团的电荷比随n的增大而递增, 揭示了给、吸电子基团间存在分子内电荷转移(ICT), 且这种电荷转移在低聚物中得到加强. 计算得到的电离势、电子亲和势、空穴抽取能、电子抽取能和重组能等相关能量, 证明了在主链上形成的载流子传输通道提高了空穴和电子传输的能力. 用TD-DFT和ZINDO方法计算了T(SBF)_nO (n＝1～4)的吸收光谱, 随着n的增大而激发光所需的能量减小, 光谱红移, 吸收强度增大|用CIS/6-31G(d)方法优化得到了不对称封端9,9 -螺双芴S₁激发态构型, 结果表明, 激发态的平面化程度比基态高.     

CH3和CN取代8-羟基喹啉电子光谱性质的含时密度泛函理论研究

对8－羟基喹啉QH及其代衍生物MQH和CNQH用密度泛函方法（DFT）在B3LYP／6－31G＊水平上进行理论计算，探讨了供电子取代基（－CH3）和吸电子取代基（－CN）对分子电子结构，前线分子轨道能和光谱性质等的影响规律，在此基础上采用含时密度泛涵方法（TD－DFT）计算了电子光谱，计算结果表明，MQH，QH和CNQH的最低激发单重态都是A，激发能分别为3．58，3．72和3．74eV，在高激发态，无论是供电子基团（－CH3）还是拉电子基团（－CN），都导致取代衍生物的电子光谱红移。     

乙烯基噻吩共轭螺噁嗪化合物的密度泛函理论研究

采用密度泛函理论(DFT)方法, 在B3LYP/6-31G^* 水平上对乙烯基噻吩共轭螺噁嗪化合物 SO-SO3 的几何构型、电子结构、前线分子轨道等进行了理论研究, 计算结果表明: SO-SO3的开环过程会使得开环体的左右两个部分键长均等化, 导致共轭体系变大, 能隙明显减小; 乙烯基噻吩基团共轭接入螺噁嗪母体后, 导致体系的共轭作用变大, 在激发态下电子流动增强, 形成由乙烯基噻吩向萘并噁嗪的有效电荷转移与能量转移; 结合前线分子轨道成分分析乙烯基噻吩单元在最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)中的轨道贡献率明显增加. 含时密度泛函理论(TD-DFT)计算的电子吸收光谱结果显示: 当接入的乙烯基噻吩单元达到2-3个时, 影响SO2和SO3开环的最低能量激发态变为第一激发单重态S₁, 并且均源自电子从HOMO至LUMO的跃迁且为π-π^*跃迁; 其最大吸收波长λ_max 达到466-540 nm, 且红移十分明显, 其对应开环体O-SO2与O-SO3的λ_max 达到605和647 nm.     

AMl-MO理论对方酸燃料结构和电子性质的研究

通过对一系列具有C－5取代基的吲哚方酸菁染料的AM1分子轨道计算，研究了染料结构和基态与单线激发态电子特性，并用（＋）（-）sparkles模拟溶剂化作用，通过AM1－CI计算的染料吸收波长接近实际测量值，并通过基态与单线激发态原子电荷密度的变化，讨论取代基效应对吸收波长的影响；循环伏安法测量的染料有两个可逆的氧化电位，电位数值随取代基给电子性的增加而减小．第一氧化电位与AM1计算的染料离子电离势，用测量的跃迁能校正的电子亲和能与AM1计算值均有很好的线性关系．     

3-苯基-6-芳基-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑的电子结构和光谱性质的含时密度泛函理论研究

对3-苯基-6-芳基-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑(PATT)用量子化学密度泛函方法(DFT)在B3LYP/6-31G(d)水平上进行了几何构型的全优化, 探讨了分子电荷转移、前线轨道能量和电子光谱等性质的变化规律, 在此基础上采用含时密度泛函方法(TDDFT)计算了分子激发态的电子跃迁能. 将其与实验所得激发态的电子跃迁能结果相比, 理论计算最大相对偏差为0.071, 最小相对偏差为0.041.     

叶绿素a激发态电子结构的量子化学计算

采用密度泛函理论DFT(B3LYP/6-31G)对氢取代后叶绿素的几何构型进行优化,并用不同的量子化学方法包含TDDFT、SAC/SAC-CI等计算激发态能量和Qy 态跃迁偶极矩的三维夹角等性质,寻找和检验适合于计算色素大分子体系精确较高且易实现的理论化学方法.CAM-B3LYP是最好计算叶绿素a的激发态前四个激发态特征的泛函形式.     

Theoretical Study of Synthesis Mechanism and Electronic Structure for 3-Octylthien-2,5-ylenediethynylenecobenzo[c]- 1 ＇ 2＇ 5＇ -thiadiazo-3,6-ylenedi（2,5-thienylene）

采用密度泛函理论中的广义梯度近似（DFT／GGA）方法,在PW91／DNP水平上研究了4,7-（2-噻吩基）苯并噻二唑-3-辛基噻吩二炔在PdCl2（PPh3）2催化下的合成机理．优化了反应过程中的反应物、中间体、过渡态和产物,通过能量分析结果证实了中间体和过渡态的真实．在同样的方法和精度研究了4,7．二（2．噻吩基）苯并噻二唑．3．辛基噻吩二炔在没有催化剂下的合成机理．通过计算结果得到此反应在有PdCl2（PPh3）2催化情况下的活化能小于没有催化剂情况下的活化能,从而证明了PdCl2（PPh3）2催化剂的催化活性．采用密度泛函理论与周期性平板模型相结合的方法,研究了产物P在Ti02（100）表面的吸附,通过Mulliken charge和前线轨道分析表明：当P吸附在Ti02（100）表面时,P向Ti02（100）表面转移0．692e电荷,前线轨道能隙变窄．理论预测的结果与实验值吻合．     

不同桥联二噻吩低带隙给受体共聚物的电子结构和光物理性质的理论研究

本文主要是通过分析吸收光谱性质来区分用于体异质结聚合物太阳能电池的两种不同桥联低带隙给受体共聚物PCPDTBT和PSBTBTS的激发态特征,进而通过分析电荷转移态（CT）特征来区分二者实现电荷分离的难易程度. 利用密度泛函理论(DFT/TD-DFT)B3LYP和CAM-B3LYP方法计算PSBTBT和PCPDTBT(n=1~4)的电子结构和光谱性质. 结果表明,从吸收光谱来看,PSBTBT与PCPDTBT的光谱相似,与太阳光谱的匹配能力相当. 而激子解离能表明二者的电荷转移态（CT）电荷分离的难易程度也相当. 然而用Si原子取代C原子后,C-Si键长明显长于C-C键长,降低了噻吩环和烷基链间的空间位阻,从而可能有利于其结晶度的提高,更加有利于载流子的传输,因此从理论上说明PSBTBT也可能具备高效太阳能电池给体材料的潜质.     

Do coupling exciton and oscillation of electron-hole pair exist in neutral and charged pi-dimeric quinquethiophenes?

Optical physical properties of neutral and charged quinquethiophene monomer, and neutral and cationic pi-dimeric quinquethiophenes were investigated with density functional theory as well as the two dimensional (2D) site (transition density matrix) and three dimensional (3D) cube (transition density and charge difference density) representations, stimulated by the recent experimental report [T. Sakai et al., J. Am. Chem. Soc. 127, 8082 (2005)]. Transition density shows the orientation and strength of the transition dipole moment of neutral and charged quinquethiophene monomer, and charge difference density reveals the orientation and result of the charge transfer in neutral and charged quinquethiophene monomer. To study if coupling exciton and oscillation of electron-hole pair exist in neutral and cationic pi-dimeric quinquethiophenes, the coupling constants J (coupling exciton of electron-hole pair) and K (coupling oscillation of electron-hole pair) were introduced to the exciton coordinate and momentum operators, respectively, and the 2D and 3D analysis methods were further developed by extending our previous theoretical methods [M. T. Sun, J. Chem. Phys. 124, 054903 (2006)]. With the new developed 2D and 3D analysis methods, we investigated the excited state properties of neutral and cationic pi-dimeric quinquethiophenes, especially on the coupling exciton and oscillation of electron-hole pair between monomers. The 2D results show that there is neither coupling exciton (J=0) nor oscillation (K=0) of electron-hole pair in neutral pi-dimeric quinquethiophenes. For some excited states of cationic pi-dimeric quinquethiophenes, there is no coupling exciton (J=0), but there is coupling oscillation (K not equal0); while for some excited states, there are both coupling exciton and coupling oscillator simultaneously (J not equal0 and K not equal0). The strength of transition dipole moments of pi-dimeric quinquethiophenes were interpreted with 3D transition density, which reveals the orientations of their two subtransition dipole moments. The 3D charge transition density reveals the orientation and result of intermonomer and/or intramonomer charge transfer. The calculated results reveal that excited state properties of neutral pi-dimeric quinquethiophene are significantly different from those of the cationic pi-dimeric quinquethiophenes.     

Assessment of TD-DFT- and TD-HF-based approaches for the prediction of exciton coupling parameters, potential energy curves, and electronic characters of electronically excited aggregates

The reliability of linear response approaches such as time-dependent Hartree-Fock (TD-HF) and time-dependent density functional theory (TD-DFT) for the prediction of the excited state properties of 3,4;9,10-tetracarboxylic-perylene-bisimide (PBI) aggregates is investigated. A dimer model of PBI is investigated as a function of a torsional motion of the monomers, which was shown before to be an important intermolecular coordinate in these aggregates. The potential energy curves of the ground state and the two energetically lowest neutral excited and charge-transfer (CT) states were obtained with the spin-component scaling modification of the approximate coupled-cluster singles-and-doubles (SCS-CC2) method as a benchmark for dispersion corrected TD-HF and a range of TD-DFT approaches. The highly accurate SCS-CC2 results are used to assess the other, computationally less demanding methods. TD-HF predicts similar potential energy curves and transition dipole moments as SCS-CC2, as well as the correct order of neutral and CT states. This supports an exciton trapping mechanism, which was found on the basis of TD-HF data. However, the investigated TD-DFT methods provide generally the opposite character for the excited states. As a consequence, these TD-DFT results have unacceptably large errors for optical properties of these dye aggregates.     

Visualizations of transition dipoles, charge transfer, and electron-hole coherence on electronic state transitions between excited states for two-photon absorption

The one-photon absorption (OPA) properties of donor-pi-bridge-acceptor-pi-bridge-donor (D-pi-A-pi-D)-type 2,1,3-benzothiadiazoles (BTD) were studied with two dimensional (2D) site and three dimensional (3D) cube representations. The 2D site representation reveals the electron-hole coherence on electronic state transitions from the ground state. The 3D representation shows the orientation of transition dipole moment with transition density, and the charge redistribution on the excited states with charge difference density. In this paper, we further developed the 2D site and 3D cube representations to investigate the two-photon absorption (TPA) properties of D-pi-A-pi-D-type BTD on electronic transitions between excited states. With the new developed 2D site and 3D cube representations, the orientation of transition dipole moment, the charge redistribution, and the electron-hole coherence for TPA of D-pi-A-pi-D-type BTD on electronic state transitions between excited states were visualized, which promote deeper understanding to the optical and electronic properties for OPA and TPA.     

Photoinduced Intramolecular Charge Transfer in Donor-acceptor Dyad and Donor-bridge-acceptor Triad

The ground and excited state properties of the 60fullerene, diphenylbenzothiadiazole-triphenylamine (PBTDP-TPA) dyad and fullerene-diphenylbenzothiadiazole-triphenylamine (fullerene-PBTDP-TPA) triad were investigated theoretically using density functional theory with B3LYP functional and 3-21G basis et and time-dependent density functional theory with B3LYP functional and STO-3G basis set as well as 2D and 3D real space analysis methods. The 2D site representation reveals the electron-hole coherence on excitation. The 3D transition density shows the orientation and strength of the transition dipole moment, and the 3D charge difference density gives the orientation and result of the intramolecular charge transfer. Also, photoinduced intermolecular charge transfer (ICT) in PBTDP-TPA-fullerene triad are identified with 2D and 3D representations, which reveals the mechanisms of ICT in donor-bridge-acceptor triad on excitation. Besides that we also found that the direct superexchange ICT from donor to acceptor (tunneling through the bridge) strongly promotes the ICT in the donor-bridge-acceptor triad.     

Excited state properties of neutral, anionic and cationic 1,1-disubstituted 2,3,4,5-tetraphenylsiloles: A quantum chemical characterization

Structure, electronic states, photoluminescence, and carries transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles for light-emitting diodes were investigated experimentally [G. Yu, et al, J. Am. Chem. Soc. 2005, 127, 6335], and the excellent electroluminescent (EL) properties of them have been found. In this paper, excited state properties of neutral, anionic and cationic 1,1-disubstituted 2,3,4,5-tetraphenylsiloles are studied with quantum chemistry method as well as the 3D real space analysis methods. The transition densities of neutral, anionic and cationic 1,1-disubstituted 2,3,4,5-tetraphenylsiloles show that the orientations and strengths of dipole moments the neutral, anionic and cationic ones are significantly different, where the neutral 1,1-disubstituted 2,3,4,5-tetraphenylsiloles show the Frenkel character; while the anionic and cationic 1,1-disubstituted 2,3,4,5-tetraphenylsiloles show the plasmon character. The charge difference densities of neutral, anionic and cationic 1,1-disubstituted 2,3,4,5-tetraphenylsiloles reveal the important diversity of the orientations and the results of intramolecular charge transfer (ICT). The theoretical results also reveal the contribution of the substituents at the 1,1-position to the neutral and charged excited state properties of 2,3,4,5-tetraphenylsiloles. The calculated results are consistent with the experimental results, and further provide the insight of understanding to the excited state properties of neutral, anionic and cationic 1,1-disubstituted 2,3,4,5-tetraphenylsiloles.     

On the accuracy of computed excited-state dipole moments

The dipole moments of furan and pyrrole in many electronically excited singlet states have been determined using coupled cluster theory including large one-electron basis sets. The inclusion of connected triple excitations is shown to uniformly decrease the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) excitation energies by 0.04-0.24 eV, with an average reduction of 0.08 eV. Using a basis set larger than DZP (++)D (double-zeta plus polarization augmented with atom- and molecule-centered diffuse functions) uniformly increases the computed EOM-CCSD excitation energies by 0.03-0.29 eV, with an average increase of 0.20 eV. The corresponding shifts in excited-state dipole moments are more erratic. Including connected triple excitations changes the computed dipole moments by an rms amount of 0.17 au. More importantly, using a larger basis set shifts the dipole moments by an rms amount of 0.52 au, with an increase or a decrease being equally likely. The CC dipole moments are compared to those from time-dependent density functional theory (TD-DFT) computed by Burcl, Amos, and Handy [ Chem. Phys. Lett. 2002, 355, 8]. For 29 excited states of furan and pyrrole, the predicted TD-DFT dipole moments differ from the CC results by rms amounts of 1.6 au (HCTH functional) and 1.5 au (B97-1 functional). Including the asymptotic correction to TD-DFT developed by Tozer and Handy [ J. Chem. Phys. 1998, 109, 10180; J. Comput. Chem. 1999, 20, 106] reduces the rms differences for both functionals to 1.2 au. If those Rydberg excited states with very large polarizabilities are excluded, the rms differences from the CC results for the remaining 17 excited states become 1.31 au (HCTH) and 0.88 au (B97-1). For asymptotically corrected functionals and this subset of states, the rms differences from the CC results are only 0.54 au (HCTHc) and 0.34 au (B97-1c). Thus, the Tozer-Handy asymptotic correction for TD-DFT significantly improves the predictions of excited-state dipole moments. For excited states without very large polarizabilities, good agreement is achieved between excited-state dipole moments computed by coupled cluster theory and by the asymptotically corrected B97-1c density functional.     

Dual Solvatochromism of Neutral Red

Abstract— The effect of solvent polarity on the electronic absorption and fluorescence properties of neutral red (NR), a phenazine-based dye of biological importance has been investigated in several neat and mixed solvents. An unusual dual solvatochromic behavior has been observed that reveals the existence of two closely spaced electronic excited states in NR. In low-polarity solvents the fluorescence of the NR is mainly emitted from the localized excited state, whereas in high-polarity solvents the emission from the charge transfer state dominates. The dipole moments of the localized and charge transfer states of NR have been estimated from the solvatochromic shifts. The dipole moment of the localized excited state (4.8 D) is only slightly higher than that of the ground state (2.0 D), while that of the charge transfer state is drastically higher (17.5 D). Fluorescence quantum yields and the life-times of NR have been determined in different solvents and correlated with the solvatochromic shifts.     

Intermediate state representation approach to physical properties of electronically excited molecules

Propagator methods provide a direct approach to energies and transition moments for (generalized) electronic excitations from the ground state, but they do not usually allow one to determine excited state wave functions and properties. Using a specific intermediate state representation (ISR) concept, we here show how this restriction can be overcome in the case of the algebraic-diagrammatic construction (ADC) propagator approach. In the ISR reformulation of the theory the basic ADC secular matrix is written as a representation of the Hamiltonian (or the shifted Hamiltonian) in terms of explicitly constructable states, referred to as intermediate (or ADC) states. Similar intermediate state representations can be derived for operators other than the Hamiltonian. Together with the ADC eigenvectors, the intermediate states give rise to an explicit formulation of the excited wave functions and allow one to calculate physical properties of excited states as well as transition moments for transitions between different excited states. As for the ground-state excitation energies and transition moments, the ADC excited state properties are size consistent so that the theory is suitable for applications to large systems. The established hierarchy of higher-order [ADC(n)] approximations, corresponding to systematic truncations of the IS configuration space and the perturbation-theoretical expansions of the ISR matrix elements, can readily be extended to the excited state properties. Explicit ISR matrix elements for arbitrary one-particle operators have been derived and coded at the second-order [ADC(2)] level of theory. As a first computational test of the method we have carried out ADC(2) calculations for singlet and triplet excited state dipole moments in H(2)O and HF, where comparison to full CI results can be made. The potential of the ADC(2) method is further demonstrated in an exploratory study of the excitation energies and dipole moments of the low-lying excited states of paranitroaniline. We find that four triplet states, T1-T4, and two singlet states, S1 and S2, lie (vertically) below the prominent charge transfer (CT) excitation, S3. The dipole moment of the S3 state (17.0D) is distinctly larger than that of the corresponding T3 triplet state (11.7D).     

Excited state properties of the chromophore of the asFP595 chromoprotein: 2D and 3D theoretical analyses

The ground and excited state properties (e.g., the intramolecular charge and energy transfer, and electron‐hole coherence) of the chromophore of the asFP595 chromoprotein from Anemonia sulcata in the neutral and anionic forms are theoretically studied with quantum chemistry methods. The ground‐state properties of the asFP595 in the neutral and anionic forms, such as the alternations of the bond lengths and the Mulliken charge distributions, are compared. The calculated transition energies of the asFP595 in the neutral and anionic form are consistent with the experimental results. To study the excited state properties of the asFP595 chromophore, the energies and densities of highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs), as well as the CI main coefficients, are compared between the two forms. The intramolecular charge and energy transfer in the neutral and anionic forms are investigated and compared with the three‐dimensional (3D) real‐space analysis methods, including the strength and orientation of the transition dipoles with transition density, and the orientation and result of the intramolecular charge transfer with charge difference density. The electron‐hole coherence and delocalization on the excitation are studied with the 2D real‐space analysis method of the transition density matrix. In all, the calculated results are remain in good agreement with the experimental data, and the theoretical analysis results supported the proposed models in the experiment. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006