DUAL-STEP CHARGE-SEPARATION IN RETINYL-C_(60) DYAD IN POLAR SOLVENTS

摘要

By time-resolved absorption and fluorescence techniques, intramolecular photoinduced charge separation and recombination in a retinyl-fullerene dyad molecule (Ret-C_(60)), which has been synthesized by the 1,3-dipolar cycloaddition of azomethine ylide to C_(60)) have been investigated in various solvents. In non-polar toluene, intersystem crossing from the singlet excited state of C_(60) (Ret-lC_(60)) to the triplet excited state (Ret-3C_(60)~*), followed by energy transfer yielding 3Ret~*-C_(60) without charge separation. On the other hand, in polar solvents such as DMF and benzonitrile, the charge separation occurs from Ret-lC_(60)~* at rate on the order of 10~(10) S~(-1) in high quantum yields close to unity. After the charge recombination, Ret-3C_(60)~* and ~3Ret~*-C_(60) were generated. Moreover, the charge separated state was also observed in microsecond time region, which was as long as those of Ret-~3C_(60)~* and ~3Ret~*-C_(60), suggesting this long charge separated state may be in equilibrium with the triplet excited states.