Addition of Ketene Silyl Acetals to the Triplet Excited State of C₆₀ via Photoinduced Electron Transfer Leading to the Fullereneacetates

The photochemical carbon—carbon bond formation of C₆₀ with ketene silyl acetals is described to give a new way for fullerene functionalization chemistry. The photoaddition of ketene silyl acetals to C₆₀occurs efficiently under irradiation of the visible light in benzene as well as benzonitrile to yield the fullereneacetates. The comparison of the observed rate constants determined from the dependence of the quantum yields on the concentrations of ketene silyl acetals as well as the quenching of triplet excited state of C₆₀ by ketene silyl acetals with those predicted for the electron transfer processes indicates that the photoaddition proceeds via photoinduced electron transfer from ketene silyl acetals to the triplet excited state of C₆₀. The negative shift in the one-electron reduction potentials by the adduct formation of C₆₀ is examined by the cyclic voltammetry measurements. The factors to control the formation of mono- and bisadducts of C₆₀ are clarified based on the rates of photoinduced electron transfer from ketene silyl acetals to the triplet excited states of C₆₀ and the adducts.