【摘要】 用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)对线型(N-杂环化)硅烷低聚体系与简单聚硅烷的电子结构和吸收光谱性质进行了比较研究。对各体系的基态分子结构在B3LYP/6-31G**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,应用含时密度泛函理论计算了电子吸收光谱的性质。计算结果显示,当主链硅原子被氮杂环环化后,由于空间位阻作用使相邻硅硅键明显伸长,使主链结构变得松散。但同时改善了分子主链的电子离域范围,增强了分子结构的可塑性。随着氮杂环数目的增加,低聚硅烷的电子吸收光谱发生明显的红移。氮杂环的引入对聚硅烷的最大吸收光谱带影响非常大。更多还原

【Abstract】 The electronic structures and absorption spectral properties of chain N-Heterocyclic oligosilanes and simple chain oligosilanes were investigated based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The geometrical structures of six oligosilanes were obtained at the B3LYP/6-31G** level. The charge distribution and the froniter molecular orbitals were also analyzed. The electronic spectra of the above structures were abtained by the time-dependent density functional theory (TD-DFT) with the 6-311+g* basis set. The calculated results show when the silicon atom in the main chain was cyclized by N-heterocycle the Si-Si bond is significantly longer than that in simple chain oligosilane because of the steric hindrance. On the other hand, exist of N-heterocycle in oligosilanes improved the electronic delocalization along main chain and enhanced the molecular plasticity. The absorption bands of N-heterocyclic oligosilanes suffered an evidently bathochromic shift with increasing number of N-heterocycle. The results indicated that N-heterocycle had much more influence for maximum absorption spectrum.更多还原