Dynamic quenching processes of the excited states of C60 with amine donors have been studied by changing donor strength, donor concentration, and solvent polarity using steady-state and transient absorption and fluorescence spectroscopic techniques. Fluorescence quenching of C60 by amines was observed, which suggests a dynamic quenching process via the excited singlet state of C60 (1C60*) in polar and nonpolar solvents. In polar solvents, electron transfer via the excited triplet state of C60 (3C60*) producing radical ions (C60.- and amine.+) was observed by the nanosecond laser flash photolysis (ca. 6 ns laser pulse). When the donor concentrations are below 10-20 mmoll dm-3, the concentrations of the radical ions increased with the donor concentrations. With further increase of the concentrations of the donors up to 100 mmoldm -3, on the other hand, the yields of the radical ions generated via 3C60* decreased. These findings indicate that dynamic quenching of 1C60* by amines increases with donor concentrations, resulting in a decrease of the intersystem crossing path to 3C60*; thus, the yields of the radical ions generated via 3C60* decreased even in the highly polar solvent. This implies that the radical ions generated by the dynamic quenching of 1C60* may be quite short-lived, even in polar solvents, compared with the radical ions via 3C 60*.
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