PHOTOPHYSICAL PROPERTIES OF C-76

The ground-state absorption spectrum of C-76 was measured in toluene s olution over the interval 300-1100 nm. Pulse radiolysis and laser flas h photolysis have been used to determine properties of the lowest trip let-state of C-76 in benzene, including the tripler difference spectru m between 310 and 1100 nm, the difference ana absolute molar absorptio n coefficients at 840 nm (epsilon = 4460 and 5730 M-1 cm(-1), respecti vely), the quantum yield of triplet formation (Phi(T) = 0.03 +/- 0.01) and the quantum yield for C-76-sensitized formation of singlet oxygen in aerated benzene (Phi(Delta) = 0.04 +/- 0.01). Our results suggest that the S-1-T-1 interval is smaller than in C-60. The strongly lipoph ilic nature of C-76, coupled with its low triplet and sensitized singl et oxygen yield, suggests its use as a carrier for delivery of highly polar drugs to hydrophobic sites and tissues without phototoxic sensit ization. (C) 1998 Elsevier Science B.V.