中文摘要：

用密度泛函理论（DFT）和含时密度泛函理论（TD—DFT）对线型（饱和N-杂环化）和（苯并N-杂环化）低聚硅烷的电子结构和吸收光谱性质以及溶剂效应进行了比较研究．对各体系的基态电子结构在B3LYP／6—31G（d，P）水平上进行了全优化，讨论了电荷分布和前线分子轨道性质．在获得基态稳定构型的基础上，用B3LYP／6—311＋G（d）方法计算了电子吸收光谱的性质，探讨了主链的线型增长和溶剂对电子吸收光谱的影响．结果表明，随着主链的增长，低聚硅烷的电子结构发生明显扭曲，在（苯并N-杂环化）聚硅烷中形成了邻近苯并N-杂环之间才丌堆积作用，有利于结构的稳定．两类低聚硅烷的吸收光谱都随着主链的增长而发生明显的红移，（苯并N-杂环化）聚硅烷最大吸收光谱红移幅度要比（饱和N-杂环化）聚硅烷大得多．溶剂效应使得光谱略向短波长移动，溶剂的极性改变对吸收波长的影响不明显．

英文摘要：

The electronic structures and absorption spectral properties of the linear （saturated N-heter- ocyclic） and （benzo-N-Heterocyclic） oligosilanes were studied using density functional theory （DFT） and time-dependent density functional theory （TD-DFT）. The geometrical structures of eight oligosi- lanes were obtained at the B3LYP/6-31G（d,p） level. The charge distribution and the frontier molecu- lar orbitals were also analyzed. Based on the optimized structures, the electronic absorption spectra have been investigated at the B3LYP/6-311 ＋ G（d） level, and the effects of the number of N-heterocy- cle and the solvent on the electronic spectra have been discussed. The results show that the molecular framework of oligosilanes twisted with the elongation of the molecular chain, and the π-π overlap in- teraction existed between adjacent benzo-N-heterocycles which leading to stable structures. The ab- sorption bands of （saturated N-heterocyclic） oligosilanes and （benzo-N-heterocyclic） oligosilanes suf- fered an evidently bathochromic shift with increasing number of N-heterocycle and benzoN-heteroey- cle. The maximum absorption peak of （benzo-N-heterocyclic） oligosilanes had much more bathochro- mic shift than （saturated N-heterocyclic） ones. The absorption bands of oligosilanes suffer slightly hypsochromic shift in solvent relative to those in the gas phase, but the influence of solvent polarity is very little.