Photochemical processes of benzyltrimethylsilane at 77 K remarkable solvent effects and reaction mechanism

Abstract

Photophysical and photochemical processes of benzyltrimethylsilane have been studied in 3-methylpentane and ethanol glass at 77 K. Remarkable solvent effects were observed in the UV photolysis: in ethanol glass, benzyl radicals were produced, while in 3-methylpentane glass α-trimethylsilylbenzyl radicals and benzyltrimethylsilane radical cations were produced. It was confirmed that the α-trimethylsilylbenzyl radicals and benzyltrimethylsilane radical cations were formed via the lowest triplet state and the benzyl radicals via the excited singlet state or higher triplet state. The molecular structure of the excited-state benzyl-trimethylsilane has been studied by MNDO-PM3 calculations. Based on the results, a possible mechanism involving the excited state of radical pair character has been proposed for the photochemical process of benzyltrimethylsilane.