Photoinduced electron transfer and adduct formation between C60/C70 and optically active 1,1′-binaphthyl-2,2′-diamine

Photoinduced electron transfer and adduct formation between C-60/C-70 and 1,1'-binaphthyl-2,2'-diamine (BNA) have been studied by nanosecond laser flash photolysis and steady-state photolysis as well as circular dichroism measurements. Quantum yields (Phi(et)(T)) and rate constants of electron transfer from BNA to the excited triplet state of C-60/C-70 have been determined by observing the transient absorption bands in the near-IR region where the triplet states and anion radicals of fullerenes appear. Compared with the planar naphthylamine moiety, Phi(et)(T) values of perpendicular bichromophoric BNA are low because of hindrance of approach to round fullerenes. The formation of an optically active adduct between C-60 and BNA in a polar solvent was observed upon excitation with light at lambda > 330 nm where both C-60 and BNA are light-absorbing. The reaction mechanism for the optically active adduct formation can be explained as a result of the addition reaction of the N-centered radical formed by deprotonation of BNA(.+), which is produced by direct photoejection.