三种五元化合物的荧光光谱的量子化学研究

Fluorescence Spectra of Three Heterocyclic OrganicCompounds with Five-membered Ring

采用密度泛函理论(DFT)中的B3LYP方法,在6 31G 水平上对三种五元杂环物质进行了构型优化,对优化后的构型做振动分析,均未出现虚频率。在此基础上通过轨道分析,探索了分子内部电子跃迁的机理。结果表明,这三种五元化合物HOMO到LUMO的跃迁是电子从C1、C2、C3和C4转移到杂原子(吡咯中的N原子,呋喃中的O原子和噻吩中的S原子)上,并在6 31G 水平上用单激发组态相互作用(CIS)方法分别计算了三种物质的荧光光谱,所得计算结果与实验值基本符合。

Ab initio calculations of fluorescence spectra have been scarcely reported in references. The fluorescence of three heterocyclic organic compounds with five-membered ring have been studied by B3LYP method of DFT, in this paper. Geometric configurations of three heterocyclic organic compounds are optimized by B3LYP method at the level of 6-31G~* and there are no imaginary frequences in vibrational analyses. On this basis, the mechanics of electronic transition in these molecules has been discussed through molecular orbital analysis. The results show that the transition between HOMO and LUMO in the three compounds is the electronic transformation from C1,C2,C3 and C4 to hetero-atoms (N atom in pyrrole,O atom in furan and S atom in thiofuran).The fluorescence spectra of these three compounds have been calculated by CIS method at the level of 6-31G~*.The results of calculation are essentially consistent with the experimental values. This paper should be valuable for ab initio calculation of electronic spectra of organic compounds.