Nanosecond Laser Flash Photolysis Steady-State Photolysis Studies of Benzyltrimethylsilane and Trimethylsilyldiphenylmethane

摘要

Photophysical and photochemical processes of benzyltrimethylsilane and trimethylsilyldiphenylmethane have been studied by fluorescence measurements and by steady-state and nanosecond laser flash photolyses. A remarkable solvent effect was observed for the laser flash photolysis of benzyltrimethylsilane; in methanol, absorption bands due to benzyl-type radicals and the triplet were observed, while in cyclohexane, only T-T absorption was observed. On the other hand, no solvent effect was observed for the laser flash photolysis of trimethylsilyldiphenylmethane; a transient absorption attributable to the 1,3-trimethylsilyl-shifted intermediate was observed with a lifetime of ca. 27 ms in both solvents, and no absorption band ascribable to diphenylmethyl radicals or the triplet was observed. GC-MS spectra of photoproducts resulting from trimethylsilyldiphenylmethane were consistent with the assignment of the transient absorption. These results were explained in terms of the calculated molecular structure for the excited singlet states of these molecules by the PM3 method.