A theoretical elucidation on the solvent-dependent photosensitive behaviors of C60

In this paper, the solvent-dependent photosensitive behaviors of fullerene (C(60)) were investigated in polar and nonpolar solvents by time-dependent density functional theory (TD-DFT) calculation. Based on the calculated physicochemical parameters on triplet state, it is revealed that excited-state C(60) only generates (1)O(2) via energy transfer in benzene, but can give birth to O(2)(.-) and (1)O(2) in water via energy transfer and electron transfer, respectively. Considering the fact that electron transfer is more favorable compared with energy transfer in polar biological systems, especially with the presence of electron donors, the O(2)(.-)-generating process will get predominant in physiological systems. These results account well for the experimental observations that O(2)(.-) and (.)OH are primarily responsible for the photoinduced DNA cleavage by C(60) under physiological conditions, whereas (1)O(2) plays a critical role in nonpolar solvents.