联苯桥联的PPV齐聚物基态构型、电子能级和吸收光谱的理论研究

用密度泛函方法对联苯桥联的PPV齐聚物(TSB)的反式结构进行全优化,得到基态分子的最优几何构型和电子能级,并用ZINDO和TD-DFT方法分别计算其吸收光谱,分析了不同类型的端位取代基团对前线分子轨道能量和能隙的影响. 结果表明,联苯桥联后的PPV齐聚物在结构上形成了链间交叉链内扭曲的构象,这种交叉扭曲的构象降低了分子的对称性,减弱了共轭分子在固体中的π-π堆积作用,这可能是减少荧光猝灭效应,提高固体发光器件效率的重要原因.     

BPh-2(mqp)的电子结构和光谱性质的含时密度泛函理论研究

采用abinitioHF和DFTB3LYP方法,对配合物BPh₂(mqp)基态结构进行优化,分析了前线分子轨道特征和能级分布.用abinitioCIS方法优化体系激发态结构.用含时密度泛函理论(TD-DFT)对BPh₂(mqp)的电子光谱进行了研究.结果发现,该物质是配体发光配合物,其发光源于mqp配体内π^*→π的电子跃迁.这表明在mqp配体上进行修饰,可有效地影响配合物前线分子轨道分布,达到调整发光波段的目的.     

气相水杨酸激发态分子内质子转移特性分析

采用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)研究了气相水杨酸(SA)分子的激发态氢键动力学过程。通过对水杨酸分子基态和激发态结构的优化,以及对其稳态吸收和发射光谱特性、前线分子轨道、红外振动光谱和势能曲线的计算分析,阐明水杨酸分子内质子转移可在激发态下自发地发生,导致其激发态可存在烯醇式和酮式两种异构体结构,并揭示了这种质子转移源于分子内电荷转移的激发态氢键的加强机制。     

7-甲氧基香豆素-3-甲酰二乙醇胺的电子结构和光谱性质的理论研究

采用密度泛函的B3LYP和单激发组态相互作用(CIS)方法分别对基态和第一、第二单重激发态(S1和S2)结构进行优化,均采用6-31G(d)基组.在优化的基态和第一单重激发态的结构基础上,用含时密度泛函理论(TD-DFT),成功模拟了7-甲氧基香豆素-3-甲酰二乙醇胺的吸收光谱和荧光发射光谱,并用极化连续模型考虑了溶剂的影响.利用前线轨道、电荷密度差(CDD)和态密度(DOS)图分析了电子跃迁的特性.计算结果与实验结果吻合得很好.该量子计算方法对此类化合物的定性和定量研究是有效的.     

8-羟基喹啉铍及其衍生物电子光谱性质的含时密度泛函理论研究

运用密度泛函理论(DFT)B3LYP方法和abinitioHF单激发组态相互作用(CIS)法分别优化了有机金属配合物8-羟基喹啉铍(BeQ₂)及其3种衍生物分子的基态及最低激发单重态几何结构.系统分析了分子结构、前线分子轨道特征和能级分布规律以探索电子跃迁机理.应用含时密度泛函理论(TD-DFT)计算分子的电子光谱,揭示了BeQ₂及其衍生物的发光源于配体中π→π^*电子跃迁,指出通过配体修饰可以有效地影响配合物前线分子轨道分布,调整发光波段,并有效提高电荷转移量.     

8-羟基喹啉锰配合物电子结构和光谱性质的含时密度泛函研究

采用密度泛函理论(DFT)B3LYP方法, 对8-羟基喹啉锰配合物进行结构优化, 探讨了配合物的结构、分子轨道能级和组成、电荷分布和转移等; 采用含时密度泛函理论(TDDFT)B3LYP/6-31G(d,p)方法对配合物的电子结构进行计算, 获得其吸收光谱. 结果表明, Mn(Ⅲ)与8-羟基喹啉中的N原子和O原子形成不对称六配位的稳定配合物, 金属锰对前线轨道的贡献很大, 在HOMO轨道中占28.53%, 在LUMO轨道中占68.30%; 中心金属锰(Ⅲ)强烈地参与发光, 电子在基态与激发态之间的跃迁, 主要是中心金属锰及8-羟基喹啉配体间的电荷转移, 在可见光区存在2个强度较大的吸收峰, 分别位于756.8 nm和532.7 nm处. 通过对双分子体系的研究发现, 相邻2个分子之间能够进行微量电荷的转移, 分子间的相互作用对前线轨道组成有明显的影响.     

染料敏化太阳能电池中具有不同电子给体的吩噻嗪类有机光敏染科的理论研究

采用密度泛函理论和含时密度泛函理论方法计算了2个吩噻嗪类染料及其吸附到TiO2上后分子的基态和激发态光物理性质与热力学参数.结果表明,电子给体的改变虽未明显改变染料的光谱性质(垂直跃迁能和振子强度),但可以改变分子的前线轨道能级,进而影响染料分子的激子结合能Eb及激发态电子注入到半导体TiO2中的驱动力△Gint的大小...     

硅杂环戊二烯衍生物电子结构与光谱性质的理论研究

采用密度泛函理论(DFT)B3LYP/6-31G*方法, 对2,5位取代的硅杂环戊二烯(Silole)系列衍生物进行几何结构优化, 通过计算得到电离能、电子亲和势、空穴抽取能及电子抽取能等相关能量, 并使用TD-DFT方法研究其吸收光谱, 分析相关能量及光谱的变化规律. 采用单组态相互作用(CIS/6-31G*)方法优化得到它们的最低单重激发态(S1)结构, 在此基础上, 使用TD-DFT方法计算对应的发射光谱. 分析2,5位芳基取代硅杂环戊二烯衍生物(DADPS)激发态与基态的结构差异及原因, 研究前线分子轨道的分布情况, 并讨论发光特征及载流子传输性能. 研究结果表明, 激发态结构弛豫主要发生在Silole环和直接与2,5位芳基相连的部位; 前线轨道主要分布在Silole环和2,5位芳基上; 二吡咯取代物有望成为空穴传输材料, 二噻吩取代物和二呋喃取代物有望在发光器件中表现出较高的发光效率.     

取代对N,N-二甲基苯乙烯基蒽的含时密度泛函研究

运用B3LYP方法和HF单激发态相互作用（CIS）方法分别优化了2-对N,N-二甲基苯乙烯基蒽（2-pNC）和9-对N,N-二甲基苯乙烯基蒽（9-pNC）分子的基态及最低激发单重态几何结构.系统分析了前线分子轨道特征,并探索了电子跃迁机理,应用含时密度泛函理论计算了分子的电子光谱.     

推/拉电子取代基对PCBM结构及光谱性质影响的理论研究

应用密度泛函理论(DFT)方法计算[6,6]-苯基-C₆₁-丁酸甲酯(PCBM)及其苯环对位取代得到的4种衍生物的几何和电子结构. 采用第一激发能校正了分子的最低未占据分子轨道(LUMO)能级, 探讨了推/拉电子基团对分子前线轨道的影响. 在全优化几何构型的基础上, 采用含时密度泛函理论(TD-DFT)方法研究了电子吸收光谱特征和电荷转移态性质, 并讨论了推/拉电子基团对体系电子吸收光谱性质的影响. 通过对重组能和电子亲和势的计算, 预测了PCBM与4种衍生物的电子能力及电子迁移率大小的关系. 结果表明, 在PCBM中, 在苯环的对位引入推电子基团可以提高分子的前线轨道能级, 改变前线轨道电子云分布, 明显增强可见光范围内的吸收强度, 增加可见光范围内的电荷转移吸收, 且激发态的电荷转移随着引入基团推电子能力的增加而增强. 化合物5的激发态分子内电荷转移性质最强, 且具有较独特的光伏性质. 而在同样位置引入拉电子基团, 则降低了分子前线轨道能级对电子吸收光谱的影响.     

Theoretical study on structural, electronic, and optical properties of ambipolar diphenylamino end-capped oligofluorenylthiophenes and fluoroarene-thiophene as light-emitting materials

Ambipolar diphenylamino end-capped oligofluorenylthiophenes and fluoroarene-thiophene show great potential for application in organic light-emitting diodes (OLEDs). Here, we provide an in-depth investigation on the optical and electronic properties of OF(2)TP-NPh ( 1a), OF(2)DTP-NPh ( 2a), OF(2)TTP-NPh ( 3a), OF(2)QTP-NPh ( 4a), and 2,5-bis-(2,3,5,6-tetrafluoro-4-trifluoromethyl-phenyl)-2,2':5',2':5',2'-quaterthiophene ( 5a). The geometric and electronic structures of the oligomers in the ground-state are studied with density functional theory (DFT) and ab initio Hartree-Fock, whereas the lowest singlet excited states are optimized by ab initio CIS. The energies of the lowest singlet excited states are calculated by employing time-dependent density functional theory (TDDFT). The results show that the highest occupied molecular orbitals, lowest unoccupied molecular orbitals, energy gaps, ionization potentials, and electron affinities for the oligomers are affected by the thiophene chain length and the different end-caps. The absorption and emission spectra exhibit red shifts to some extent due to the increasing thiophene chain length and the enhancing electron-donating property of the end-caps. Furthermore, the large Stokes shifts ranging from 58 to 80 nm are examined, resulting from a more planar conformation of the excited-state between the two adjacent units in the oligomers. All the calculated data show that the fluoroarene-thiophene has improved electron transport rate and charge transfer balance performance, and all the studied molecules can be used as ambipolar-transporting materials in OLEDs.     

DFT study of conjugational electronic structures of aminoalkyl end-capped oligothiophenes up to octamers

The molecular geometries and electronic properties of a series of bis(aminoalkyl) end-capped oligothiophenes (BRnTs) were investigated by means of the density functional theory (DFT). The calculations were performed on dimers up to octamers in the neutral and ionic species using the B3LYP/6-31G(d,p) level of theory. The results obtained show that the conjugated systems in the p- and n-doped oligomers had more aromaticity, with expanded and planar chains. The calculated energy gap values between the frontier molecular orbitals for the end-capped oligomers were larger than those for the unsubstituted oligomers, in which with increase in the oligomer chain length, the conduction band gap decreased. The calculated first excitation energies of BRnTs at the TD-B3LYP/6-31G(d,p) level indicated that both doped oligomers (p- and n-type) had lower excitation energies than the neutral states, and that they displayed red shifts in their absorption spectra. Moreover, the results obtained for the natural bond orbital (NBO) analysis showed that closing the end-side oligothiophene chains with the aminoalkyl groups eased the hole or electron transfer, owning to better charge delocalization through the backbone structures of BRnTs.     

Optical and Electrical Properties of Triphenylamine Derivatives for Dye-sensitized Solar Cells and Designing of Novel Molecule

With density functional theory(DFT) method, the optimization of molecular configurations and the calculation of frontier molecular orbitals were achieved for triphenylamine(TPA)-based dye-sensitized solar cell materials at the B3LYP/6-31G(d, p) level. Time-dependent density functional theory(TD-DFT) was applied to calculating the probability of the transition from the ground state to the excited state. And UV-Vis absorption spectra were derived with Franck-Condon approximation. The conjugation length, substitution groups and spatial effects show a slight influence on the dihedral angle of the TPA group. The increase of conjugation length may cause a smaller energy gap as well as a higher highest occupied molecular orbital(HOMO) and a lower lowest unoccupied molecular orbital (LUMO). The introduction of methoxyl group and TPA group could lower the energy gap while the HOMO and LUMO were elevated in energy.     

Investigation of the electronic spectra and excited-state geometries of poly(para-phenylene vinylene) (PPV) and poly(para-phenylene) (PP) by the symmetry-adapted cluster configuration interaction (SAC-CI) method

The symmetry-adapted cluster-configuration interaction (SAC-CI) method has been used to investigate the optical and geometric properties of the oligomers of poly(para-phenylene vinylene) (PPV) and poly(para-phenylene) (PP). Vertical singlet and triplet absorption spectra and emission spectra have been calculated accurately; the mean average deviation from available experimental results lies within 0.2 eV. The chain length dependence of the transition energies has been improved in comparison to earlier TDDFT and MRSDCI calculations. The present analysis suggests that conventional TDDFT with the B3LYP functional should be used carefully, as it can provide inaccurate estimates of the chain length dependence of the excitation energies of these molecules with long pi conjugation. The T1 state was predicted to be at a lower energy, by 1.0-1.5 eV for PPV and by 0.9-1.7 eV for PP, than the S1 state, which indicates a localized T1 state with large exchange energy. By calculating the SAC-CI electron density difference between the ground and excited states, the geometry relaxations due to excitations can be analyzed in detail using electrostatic force theory. For trans-stilbene, the doubly excited 21Ag state was studied, and the calculated transition energy of 4.99 eV agrees very well with the experimental value of 4.84 eV. In contrast to previous ab initio calculations, we predict this doubly excited 21Ag state to lie above the 11Bu state.     

Star-shaped Organic Molecules That Comprise a 1,3,5-Trisubs-tituted Benzene Core and Three Oligoaryleneethynylene Arms as Light-emitting Materials

Star‐shaped rigid molecules that comprise a 1,3,5‐trisubstitued benzene core and three oligoaryleneethynylene arms have great potential application in organic light‐emitting devices (OLEDs). Their optical and electronic properties are tuned by the star‐shaped molecular size. To reveal the relationship between the properties and structures, we perform a systemic investigation for these organic molecules. The ground and excited state molecules are studied using density functional theory (DFT), the ab initio HF, and the single excitation configuration interaction (CIS), respectively. And the electronic absorption and emission spectra are investigated with time‐dependent density functional theory (TDDFT) and Zerner's intermediate neglect of differential overlap (ZINDO) methods. The results show that the HOMOs, LUMOs, energy gaps, ionization potentials (IP), electron affinities (EA), absorption and emission spectra are controlled by the star‐shaped molecular size, which favor the hole and electron injection into OLEDs. With increasing the molecular conjugated length, the absorption and emission spectra exhibit red shifts to some extent and are in good agreement with the experimental ones. Also, the calculated emission spectra range from 330 to 440 nm. All the calculated show that the star‐shaped molecules are promising as blue light emitting materials     

9,9′-螺双芴的光电性能

采用密度泛函理论(DFT)-B3LYP/6-31G(d)方法对9,9'-螺双芴低聚物[(SBF)_n(n=1-4)]体系进行全优化,得到各分子的最高占据轨道(HOMO)和最低空轨道(LUMO)能量及HOMO-LUMO能隙,结果表明各分子整体表现出很好的共轭性质.并在分子的阳离子和阴离子状态的优化结构基础上,计算得到电离势(IP)、电子亲和势(EA)、空穴抽取能(HEP)、电子抽取能(EEP)和重组能等相关能量.利用单激发组态相瓦作用(CIS)/3-21G方法优化得到9,9'-螺双芴单体的S_1激发态的几何构型.用含时密度泛函理论(TD-DFT)方法计算得到了分子吸收光谱和荧光光谱的相关数据.随着聚合长度的增加,能隙变窄,空穴注入和电子转移的能力都相应提高,吸收光所需能量减小,吸收强度(f)增大,光谱红移.采用线性外推法,利用低聚物分子的各种性质与聚合度n之间的关系,得到高聚物的相应性质.为考察9位螺芴化的影响,将(SBF)_n的相关性质与母体芴的低聚物[(FL)_n(n=1-4)]进行比较,由两者的计算结果对比显示,在芴的9位螺芴化可以提高电子和空穴的传输能力,并同时保留芴优良的发光性质.     

9,9’-螺双芴的光电性能

采用密度泛函理论(DFT)-B3LYP/6-31G(d)方法对9,9'-螺双芴低聚物[(SBF)n(n=1-4)]体系进行全优化, 得到各分子的最高占据轨道(HOMO)和最低空轨道(LUMO)能量及HOMO-LUMO能隙, 结果表明各分子整体表现出很好的共轭性质. 并在分子的阳离子和阴离子状态的优化结构基础上, 计算得到电离势(IP)、电子亲和势(EA)、空穴抽取能(HEP)、电子抽取能(EEP)和重组能等相关能量. 利用单激发组态相互作用(CIS)/3-21G方法优化得到9,9'-螺双芴单体的S1激发态的几何构型. 用含时密度泛函理论(TD-DFT)方法计算得到了分子吸收光谱和荧光光谱的相关数据. 随着聚合长度的增加, 能隙变窄, 空穴注入和电子转移的能力都相应提高, 吸收光所需能量减小, 吸收强度(f)增大, 光谱红移. 采用线性外推法, 利用低聚物分子的各种性质与聚合度n之间的关系, 得到高聚物的相应性质.为考察9位螺芴化的影响, 将(SBF)n的相关性质与母体芴的低聚物[(FL)n(n=1-4)]进行比较, 由两者的计算结果对比显示, 在芴的9位螺芴化可以提高电子和空穴的传输能力, 并同时保留芴优良的发光性质.     

烷基取代对罗丹明的电子结构与光谱的影响

在密度泛函理论(DFT)的B3LYP水平对不同烷基在不同位置取代形成的8种罗丹明化合物进行结构优化,并在此基础上应用含时密度泛函理论(TD-DFT)和单激发组态相互作用(CIS)方法分析了取代基对罗丹明的电子结构、前线分子轨道及电子光谱的影响.计算结果表明,前线分子轨道主要分布在罗丹明分子的氧杂蒽环上,罗丹明分子中两个N端的H各只有1个H被烷基取代时,最高占据轨道(HOMO)在主要共轭环分布最多,且HOMO和最低未占据轨道(LUMO)分布比例相差最小,两个N端4个H同时被甲基取代时,能隙最窄,对气相最大吸收波长红移程度最大,两个N端4个H同时被乙基取代时,气相荧光最大,发射波长最长.