Computational studies on the spectroscopic properties of the 2‐pyridylpyrazolate‐based platinum(II) complexes with modified pyrazolate fragment

Electronic structures and spectroscopic properties of a series of platinum(II) complexes based on the 2‐pyridylpyrazolate ligand with modified pyrazolate fragment have been studied by the time‐dependent density functional theory (TD‐DFT) calculations. The ground‐ and excited‐state structures were optimized by the DFT and single‐excitation configuration interaction (CIS) methods, respectively. The calculated structures and spectroscopic properties are in agreement with the corresponding experimental results. The results of the spectroscopic investigations revealed that the lowest‐energy absorptions have ^1,3MLCT/^1,3ILCT mixing characters. When the electron‐withdrawing groups (? CF₃, ? C₃F₇) are introduced into the pyrazolate fragment, the lowest‐energy absorptions are blue‐shifted compared with that without substituents on the pyrazolate fragment, while the opposite case is observed for the electron‐donating groups (? Me, ? ^tBu, etc.). Otherwise, the phosphorescent emissions of these complexes have the ³MLCT/³ILCT character and should be originated from the lowest‐energy absorptions. When the pyrazolate fragment is replaced by the indazole group, the HOMO and LUMO orbitals of the pyridyl‐indazolate ligand platinum(II) complexes have obvious π and π* orbital characters. Therefore, there is no evident MLCT character in the lowest energy absorption and emission. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

"双"吡唑啉类化合物的荧光光谱理论研究

采用量子化学半经验方法RHF／AM1,RHF／PM3对4种“双”吡唑啉衍生物进行构型优化,经振动分析未出现虚频率,在此基础上用RHF／CIS方法分别计算了它们的荧光光谱,所得结果与文献值基本符合。     

三种2-苯乙烯基苯并噻唑类化合物荧光性能的量子化学研究

采用量子化学半经验方法RHF／AM1对3种有较高杀霉活性的2—苯乙烯基苯并噻唑类化合物的电致发光性质进行了理论研究,对探索新型有机发光材料以及设计具有特定光电转换功能材料的分子提供了一种新的研究方法。对各化合物进行的构型优化表明,分子具有一定的平面结构,且具有较大的离域π键。对优化后的构型进行振动分析,其最小振动频率分别为13．50,9．66,7．53cm^-1,均未出现虚频率。4种化合物的HOMO和LUMO之间的能量差△E分别为7．838,7．706,7．288eV,△E较小,离域电子容易激发。在此基础上用RHF／CIS方法分别计算了它们的荧光光谱,选用1153个组态进行计算,所得结果与实验值基本符合。     

Ab initio electronic structure theory as an aid to understanding excited state hydrogen transfer in moderate to large systems

Hypocrellin and hypericin are naturally occurring polycyclic perylene quinones, and they have both been found to exhibit photoactivated antiviral and anticancer activity. One mode of action proposed involves excited-state hydrogen transfer. Consequently these compounds have been widely studied using spectroscopic methods, and are found to both absorb and emit in the visible region. Recently an analog dihydroxy perylene quinone was synthesized in order to examine its antiviral activity in relation to the naturally occurring compounds. Its UV-visible absorption and emission spectra are quite different to those of hypocrellin and hypericin, with very weak absorption and no visibility of emission at all. The ab inito excited-state methods, configuration interaction singles (CIS), state-averaged complete active space self-consistent field (SA–CASSCF), and SA-multireference perturbation theory (SA–MRMP2) are used to examine the origin of this different absorption and emission behavior. Owing to the size of these systems (between 24 and 40 heavy atoms) extensive use of parallel processor algorithms was made, especially a parallel atomic orbital-based CIS energy and gradient code developed at the ABCC. The performance of these methods, and possible ,as well as future directions and prospects are discussed.     

Ion-beam analysis of CuInSe<Subscript>2</Subscript> solar cells deposited on polyimide foil

CuInSe₂ (CIS) solar cells deposited on polyimide foil by the Solarion company in a web-coater-based process using sputter and evaporation techniques were investigated in the ion beam laboratory LIPSION of the University of Leipzig by means of Rutherford backscattering spectrometry (RBS) and particle-induced X-ray emission (PIXE) using high-energy broad ion beams and microbeams. From these measurements the composition of the absorber and the lateral homogeneity and film thicknesses of the individual layers could be determined on the basis of some reasonable assumptions. For the first time, quantitative depth profiling of the individual elements was performed by microPIXE measurements on a beveled section prepared by ion-beam etching of a CIS solar cell. Within the CIS absorber layer no significant concentration–depth gradients were found for Cu, In, and Se, in contrast with results from secondary neutral mass spectrometry (SNMS) depth profiling, which was applied to the same samples for comparison. Furthermore, both PIXE and SNMS showed the presence of a remarkable amount of Cd from the CdS buffer layer in the underlying absorber.     

The spectroscopy, dynamics, and electronic structure of pyrenyl-dU nucleosides: P/dU charge transfer state photophysics

Various spectroscopies including UV-vis absorbance, emission, and emission quantum yield are combined with a variety of kinetics measurements including time resolved emission and nanosecond, picosecond, and femtosecond transient absorbance (TA) to systematize the P⁺/dU⁻ charge transfer (CT) state dynamics of a variety of pyrenyl-dU nucleoside conjugates in several solvents of varying polarity. These results are then analyzed further by means of electronic structure computations in vacuum and using two different solvent models. Finally, the excess electron dynamics of a number of DNA duplex structures substituted with two different pyrenyl-dU nucleosides and 5-XdU, where X=Br or F, electron traps are discussed in terms of achieving high yields of long-lived photoinduced CT products in DNA.     

六种香豆素类染料荧光光谱的量子化学研究

采用量子化学半经验方法AM1对6种香豆素类染料的荧光光谱进行了理论研究。对各化合物优化后的构型作了振动分析,均未出现虚频率。在此基础上,采用单激发组态相互作用方法(CIS)计算荧光光谱,所有计算结果与实验值基本吻合。     

S_2分子的从头算研究

采用了微机版的Gaussian 94程序以及CIS方法和CIS MP2方法对S2 分子的部分单重激发态和三重激发态进行了研究。计算表明 :CIS方法和CIS MP2方法对S2 分子的低单重激发态基本适用 ,可以给出较为满意的结果。但对S2 分子的三重激发态和高激发态 ,CIS方法还需进一步改进。     

四种芳香稠环化合物荧光光谱的量子化学研究

芳香稠环化合物是一类重要的化合物,并且一般具有较大的共轭体系,是一类良好的电致发光材料.这类物质的光谱在近来的科学研究中已经成为了一个热点.对4种芳香稠环化合物的荧光光谱进行了理论研究.采用量子化学半经验方法RHF/PM3对4种化合物的构型进行了全参数的优化.并对优化后的构型作了振动分析,均未出现虚频率,说明所得优化构型基本合理.在此基础上,采用单激发组态相互作用方法(CIS)计算4种化合物的荧光光谱,所有计算结果与实验值基本吻合.