HC60CH2C6H5的结构及光谱的理论研究

用ＩＮＤＯ系列方法研究了由Ｃ６０＾２－制备的衍生物ＨＣ６０ＣＨ２Ｃ６Ｈ５的结构和ＵＶ光谱。结果表明，六元环上的１，２－异构体具有Ｃｓ对称性，１，４－异构体具有Ｃ１对称性。以优化构型为基础，计算两种加成产物的ＵＶ光谱，表明１，２－异构体的特征吸收与实验值相符；同时，对１，４－异构体的ＵＶ光谱进行了理论预测，对电子跃迁进行了理论指认，并分析了光谱红移的原因。     

Electron correlation in weakly coupled transition metal dimers: Bimetallocenylenes and bimetallocenes

The Hartree-Fock (HF) instabilities in a series of bimetallocenes (1) and bimetallocenylenes (2) with Fe, Co, Ni and Cr as 3d centers have been investigated by means of a semiempirical INDO Hamiltonian. The HF picture is only valid in the case of the iron dimers. Strong correlation effects are encountered in the Co, Ni and Cr complexes. The necessary conditions for singlet, non-singlet (triplet) and non-real variations of the HF orbitals are discussed in detail. Singlet fluctuations are the result of intraatomic angular correlation (short-range) at each 3d center. The violation of the spin symmetry corresponds to a long-range interaction between the transition metal centers. Only for MOs with large 3d _xz amplitudes there exists a channel for the interatomic spin decoupling. Consequences for polymetallocenes are shortly discussed.     

四苯基卟啉及其系列衍生物电子光谱的INDO/CI研究

运用ＭＮＤＯ计算和群论,优化得到了较满意的中位取代四苯基卟啉（Ｈ２ＴＰＰ）的分子构型。并结合ＩＮＤＯ／ＣＩ方法,对四苯基卟啉及其系列衍生物进行了电子结构的研究和电子光谱主要吸收带的指认。提出五分子轨道模型,揭示了卟啉类化合物电子光谱典型特征的内在原因,计算结果能与实验值较好符合。对卟啉系列衍生物的取代基效应进行了讨论,得到一些有益的结论。     

硝基取代亚酞菁衍生物的电子光谱和非线性光学性质的理论研究

在AM₁方法优化的几何结构基础上,用INDO/CI-SOS方法深入探讨亚酞菁(C₂₄H₁₂B₁Cl₁N₆)的硝基取代对体系的电子光谱和二阶非线性光学性质的影响.结果表明,吸电子取代基和取代基的共轭链的增长对亚酞菁的分子结构和电子光谱的最大吸收峰影响很小,但对非线性光学性质都有较大影响,随着共轭链的增长,二阶非线性光学系数大幅度增强.未被取代的亚酞菁的β₀计算值与实验值十分相符,分别为-0.73×10^-28和-0.70×10^-28esu,共轭链最长的硝基取代化合物β₀值增大到-1.47×10^-28esu,增加约近1倍.     

C}oS的结构和电子光谱的理论研究

用IND(〕方法研究C,oS的8种构型.表明S原子主要连接在C,。的C,-C}(C,表示C7o的第一种C原子)或C3一 C3键上.且不开环形成三员环状结构.光谱研究表明,C7oS的主要吸收峰与C7。相似,且在500mm以上产生特征吸收峰,可以此作为C,oS形成的依据、     

Theoretical study of solvent influence on the electronic absorption and emission spectra of kynurenine

Neutral/zwitterionic form equilibrium, excited state wave functions, absorption and emission spectra of kynurenine (KN) in various solvents (water, methanol, ethanol, and dimethylsulfoxide) have been studied theoretically. The ground electronic state geometries have been optimized by density functional theory methods; the geometries of the first two singlets excited electronic states have been optimized using the CASSCF technique. The influence of the solvent was taken into account by the calculation of the solvation free energies using the Polarizable Continuum Model (PCM). The spectra of electronic absorption and fluorescence emission have been calculated by the CS‐INDO S‐CI and SDT‐CI methods [Momicchioli, Baraldi, and Bruni, Chem Phys, 1983, 82, 229]. The calculated data reproduce the experimental positions of maxima and the solvent‐induced shifts of the absorption and emission bands well. The energy gap between the two lowest excited states of KN increases from aprotic to protic solvents. This fact suggests that the “proximity effect” cannot be responsible for the ultrafast decay of KN fluorescence in protic solvents. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Theoretical and experimental photophysical studies of the tris(4,4,4-trifluoro-1-(1-naphthyl)-1,3-butanedionate) (2,2′-bipiridyl)-europium(III)

The complexes tris(4,4,4-Trifluoro-1-(1-naphthyl)-1,3-butanedionate) (2,2′-bipiridyl) Ln(III), Ln(tan)₃bipy, where Ln(III)=Eu³⁺ and Gd³⁺ have been synthesized, characterized and their photophysical properties (absorption, excitation and luminescence spectra and emission quantum yield) investigated down to 4.2 K. The Eu(tan)₃bipy complex has its molecular structure experimentally determined using X-ray crystallography and theoretically using the SMLC/AM1 method as well as their electronic singlet and triplet states were calculated, using the INDO/S-CI method with a point charge model to represent the Eu³⁺ ion, where two values were adopted, +3.0e and +3.5e, to investigate the imperfect shielding of the 4f shells. The so calculated +3.5e model electronic absorption spectrum and low lying triplet state energies agreed very well with the experimental ones. The emission quantum yield of the Eu³⁺ complex is quite low at room temperature, namely 7%, probably due to the too low lying triplet state, 19,050 cm^-1, and increases by a factor of three when the temperature is lowered to 4.2 K. This strong thermal effect indicates the presence of a channel deactivating the main emitting state, what can be due to a LMCT state possibly lying in the same spectral region, as usually found in Eu³⁺ compounds.     

Electronic Absorption Spectra of Some 2-Thiouracil Derivatives

Abstract

The electronic absorption spectra of 2-thiouracil and some of its derivatives were investigated using polar and nonpolar solvents. The present analysis is facilitated via computer deconvolution of the observed spectra and molecular orbital (MO) computations. Comparison between the experimentally observed and theoretically computed spectra in addition to a quantitative assignment of all transitions observed were undertaken. The computed dipole moments are used to indicate the polarity of the excited state and hence predict its solvent dependence. The spectra are, in general, very well predicted and assigned using INDO/S computational results. The spectrum of the trifluoro derivative is much more complicated and the corresponding states show much more solvent dependence than those observed for other thiouracil studied.     

C60异噁唑环衍生物的结构、电子光谱和非线性光学性质的研究

应用半经验AM1量子化学方法研究了8种C60异噁唑环衍生物的结构,以AM1优化几何构型为基础,用ZINDO/CIS方法计算了目标分子的电子光谱.结果表明,异噁唑环的引入导致HOMO与LUMO间的能级差减小, C60母体与加成基团之间存在分子内电荷转移.计算所得电子光谱值与实验结果较吻合,几种化合物在400nm以上均产生非C60特征吸收峰,这些峰是电荷从加成基团向C60部分转移产生的.用FF/AM1方法计算了分子非线性光学系数α、β、γ值,在所得计算结果上推测了影响体系非线性光学系数效应的因素.     

2-（4，5-二硫甲基-1，3-二硫环戊烯基）-3，4-富勒吡咯烷的合成表征及电子光谱的INDO/ S研究

通过亚胺叶立德与C60 发生 1,3 偶极环加成反应的方法 ,合成了一种新的具有分子内给 受体系的C60吡咯烷衍生物 2 (4 ,5 二硫甲基 1,3 二硫环戊烯基 ) 3,4 富勒吡咯烷 (C66H9NS4) ,以红外、元素分析、核磁共振氢谱、紫外进行了表征 .运用Gaussian98量子化学程序包 ,利用密度泛函的方法对分子的几何构型进行了优化 ,在优化的基础上 ,应用INDO/S的方法计算了化合物的电子光谱 ,计算结果表明 ,C66H9NS4的光谱吸收在 4 38.9nm ,与实验值 4 31.4nm基本一致