Photoinduced electron-transfer reaction between C₆₀ and cyclic silicon compounds

Electron transfer from cyclic silicon compounds to photo-excited C₆₀ in polar 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 radical anion of C₆₀ [C₆₀· ^-] was observed with the rapid decay of the triplet state of C₆₀ [³C₆₀*], indicating that electron transfer takes place via ³C₆₀*. The rate constant (k_et) and quantum yield (Φ_et) of electron transfer decrease with an increase in the number of silicon units. The k_et and Φ_et values of the cyclic silicon compounds are smaller than those of the corresponding cyclic germanium compounds; an especially prominent difference was observed for four-membered cyclic compounds.