Photoinduced electron-transfer reaction between C-60 and cyclic silicon compounds

Electron transfer from cyclic silicon compounds to photo-excited C-60 in po lar solvents has been investigated by laser photolysis with observation of the transient absorption bands in the near-IR region. For three-, four- and five-membered cyclic silicon compounds in benzonitrile, the rise of the ra dical anion of C-60 [C-60(.-)] was observed with the rapid decay of the tri plet state of C-60 [C-3(60)*], indicating that electron transfer takes plac e via C-3(60)*. The rate constant (k(et)) and quantum yield (Phi(et)) of el ectron transfer decrease with an increase in the number of silicon units. T he k(et) and Phi(et) values of the cyclic silicon compounds are smaller tha n those of the corresponding cyclic germanium compounds; an especially prom inent difference was observed for four-membered cyclic compounds. (C) 2000 Elsevier Science S.A. All rights reserved.