Homolytic cleavage of C–Si bond of p-trimethylsilylmethylacetophenone upon stepwise two-photon excitation using two-color two-laser flash photolysis

Abstract

C–Si bond cleavage of p-trimethylsilylmethylacetophenone( 1) occurred in a higher triplet excited state (T n ), giving mainly p-acetylbenzyl radical with the transient absorption in the region of 295–360 nm, with a quantum yield of 0.046 ± 0.008 using the two-color two-laser photolysis techniques. In contrast, the C–Si bond cleavage of p-trimethylsilylmethylbenzophenone( 2) was absent in the T n state whose energy is larger than the C–Si bond cleavage energy. The results can explain existence of a bond cleavage crossing between potential surfaces of the T n state and a dissociative state of the C–Si bond for 1, but not for 2.