Photophysical properties of C76

The ground-state absorption spectrum of C76 was measured in toluene solution over the interval 300–1100 nm. Pulse radiolysis and laser flash photolysis have been used to determine properties of the lowest triplet-state of C76 in benzene, including the triplet difference spectrum between 310 and 1100 nm, the difference and absolute molar absorption coefficients at 840 nm (ε=4460 and 5730 M−1 cm−1, respectively), the quantum yield of triplet formation (ΦT =0.03±0.01) and the quantum yield for C76-sensitized formation of singlet oxygen in aerated benzene (ΦΔ =0.04±0.01). Our results suggest that the S1–T1 interval is smaller than in C60. The strongly lipophilic nature of C76, coupled with its low triplet and sensitized singlet oxygen yield, suggests its use as a carrier for delivery of highly polar drugs to hydrophobic sites and tissues without phototoxic sensitization.