旋轨耦合从头算方法研究CH2BrI光解离机理

Spin-orbit Coupling ab initio Investigation on the Photolysis Mechnism of CH_2BrI

基于CH2Br I光解离的最新实验报道,采用多态完全活化空间二阶微扰理论和完全活化空间态相互作用-旋轨耦合作用(MS-CASPT2/CASSI-SO)方法,计算了CH2Br I在乙腈、2-丁醇和环己烷3种溶剂中,在266nm的光激发下的旋轨耦合态的势能曲线,指认了实验观测到的解离产物I(2P3/2)和I*(2P1/2)的具体解离途径.为了理解不同溶剂对光产物重新结合成CH2Br—I和CH2I—Br的影响,对CH2Br I在溶剂中光异构化过程的反应机理进行了探讨.

Based on the latest experimental results in solvents, the state-of-the-art quantum chemical calcula- tion, i.e. the multi-state second order multiconfigurational perturbation theory in consideration of the spin- orbit coupling interaction through complete active space state interaction （MS-CASF1E/CASSI-SO） was used for investigating the spin-orbital-coupled states potential energy curves（PECs） of bromoiodomethane（ CH2BrI） at 266 nm in solvents （acetonitrile, 2-butanol and cyclohexane）. The calculated PECs leading to the products I （2 P3/2 ） and I ＊ （2 P1/2 ） are consistent with the experimental observations. The mechanisms of the photoisomerization in solvents were studied in order to understand the effects of solvent polarity on the recombi- nation products（ CH2Br--I and CH2I--Br）. The current calculation assigned the latest experimental observa- tion, and once again evidenced the necessity of involving the spin-orbit coupling effect for heavy atoms like Br and I.