Photophysical Properties of C84 Major Isomers

Photophysical properties of C84 isomers have been measured separately and compared. Intrinsic triplet state lifetimes at room temperature are found to differ dramatically: 4.5 μs for the D 2 d (II) isomer, 125 μs for C s (a), and 640 μs for D 2(IV). The triplet lifetime of D 2(IV) C84 represents the second longest found to date among fullerenes. Measurements between 77 and 320 K reveal that the triplet decay kinetics of D 2 d (II) is largely temperature-independent, whereas thermally activated channels dominate triplet decay in the D 2(IV) isomer. Oxygen-quenching studies suggest that the T1 energy of D 2 d (II) lies near 7600 cm-1 but that of D 2(IV) exceeds 8000 cm-1. These results highlight the importance of isomeric separation in exploring the rich photophysics of higher fullerenes.