PhotoGreen Lab, Department of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy.
J Org Chem. 2013 Apr 19;78(8):3814-20. doi: 10.1021/jo400269s. Epub 2013 Mar 22.
Calculations with the complete active space self-consistent field (CASSCF) method were carried out for rationalizing the photochemical generation of the three isomeric didehydrotoluenes (DHTs) from the corresponding (n-chlorobenzyl)trimethylsilanes. Moreover, the original CASSCF energies were corrected through the introduction of the dynamic electron correlation term (at the MP2 level) and of an appropriate solvent model (CPCM). The work demonstrated the viability of intersystem crossing (conical intersection located) leading to the lowest lying triplet state of the silanes that fragments to give the corresponding triplet phenyl cations. The para- and ortho-isomers desilylate directly from such states of radical/radical cation character and yield the corresponding DHTs in their triplet state. Different from the other isomers, the meta-cation has a radical/radical cation structure in both spin states and thus two potential accesses to the different spin states of the corresponding DHT.
运用完全活性空间自洽场（CASSCF）方法进行计算，以解释相应的（n-氯苄基）三甲基硅烷通过光化学反应生成三种同分异构的去氢甲苯（DHT）。此外，通过引入动态电子相关项（在 MP2 水平上）和适当的溶剂模型（CPCM），对原始的 CASSCF 能量进行了修正。该工作证明了体系间穿越（位于锥形交叉点）的可行性，这种穿越导致硅烷的最低三重态片段生成相应的三重态苯阳离子。对位和邻位异构体直接从这种自由基/自由基阳离子特征的状态去硅化，并在三重态下生成相应的 DHT。与其他异构体不同，间位阳离子在两种自旋状态下均具有自由基/自由基阳离子结构，因此有两种可能的途径可以进入相应 DHT 的不同自旋状态。
