旋轨耦合从头算方法研究CH2 BrI光解离机理

摘要

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-CASPT2/CASSI-SO) was used for investigating the spin-orbital-coupled states potential energy curves( PECs) of bromoiodomethane( CH2 BrI) 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( CH2 Br—I and CH2 I—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.%基于CH2 BrI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CH2 BrI在乙腈、2-丁醇和环己烷3种溶剂中，在266 nm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CH2 Br—I和CH2 I—Br的影响，对CH2 BrI在溶剂中光异构化过程的反应机理进行了探讨。