四种芳香稠环化合物荧光光谱的量子化学研究

Quantum Chemistry Study on Fluorescence Spectra of Four Polycyclic Aromatic Hydrocarbons

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。

Polycyclic aromatic compounds are the important compounds in scientific research and practical applications. Generally speaking, they have a bigger conjugate system. Almost atoms of them are in one plane. So they are good electroluminescence materials. The study of spectra for these substances has become a focus in recent scientific researches. A theoretical study on fluorescence spectra of four polycyclic aromatic compounds is given. Their geometric configurations have been optimized by semi-empirical method RHF/PM3. The structure analysis indicates that double C=C bond length in four compounds is longer than normal double bond and shorter than normal C-C bond, which shows that their electrons partly shift. From the analysis of the torsion angles, it is found that all benzene cycles of four compounds are in one plane, which, to some extent, enhances the compounds＇ stability. For all optimal configurations, we have calculated the IR spectra and there is no imaginary frequency in vibrational analyses, which indicates that the opitimized geometries are basically reasonable. On this basis, the electronic spectra have been calculated by CIS method. All calculated results are basically consistent with experimental values.