N－甲基-吡咯烷并[3,4]C60衍生物的结构、电子光谱 和二阶非线性光学性质的 理论研究

利用半经验AM1量子化学方法研究了N－甲基－吡咯烷并[3,4]C60(MPC)及其噻吩取代衍生物(TMPC)的几何结构。电子结构研究表明，MPC及TMPC衍生物的前沿轨道主要由C60部分决定，C60母体与成基团之间存在较强的分子内电荷转移，C60部分是电子受体，而噻吩环部分和吡咯环部分为电子给体。在AM1优化几何构型的基础上，用INDO/SCI方法计算了MPC及TMPC的电子光谱，用完全态求和(SOS)公式计算了其二阶非线性光学性质。结果表明，MPC与TMPC在400nm以上均存在吸收峰，TMPC的这些吸收峰(400nm以上)比MPC的吸收峰强得多，与实验所得结果一致。对于TMPC来说，其二阶非线性光学系数β0值随分子构型不同而有较大的变化，β0值最大可达60×10^-30esu。

Theoretical investigation on electronic spectra and second-order nonlinear optical properties of N-methyl-pyrrolo [3,4]C60 derivatives

By using AM1 semiempirical quantum calculation method, the structures and electronic properties of N-methyl- pyrrolo[3,4]C60(MPC) and N-methyl-2-(2'-dimethylaniline- substituted dithienylen-thylene)- pyrrolo[3,4]C60(TMPC) have been studied. The froniter molecular orbitals of the C60 moiety dominate those of MPC and TMPC. For MPC and TMPC, there exists strong intramolecular electron transfer. The C60 moiety is electron acceptor while the thiophene and pyrrolidine parts are electron donor. Based on the AM1 optimizing geometry, the electronic spectra and seccond- order nonlinear optical polarizabilites (β) of TMPC and MPC are calculated by using INDO/SCI method combined with sum-over-states (SOS) expression. The calculated results reveal that there exist absorption peaks above 400 nm both for TMPC and MPC and those of TMPC are much stronger than those of MPC. For TMPC, β values vary with different isomers.