Paramagnetic states and dynamics of photoexcited C₆₀

Photoexcited triplet and photoinduced doublet states of C₆₀, oriented in a nematic liquid crystal (LC) and toluene, were studied by time-domain EPR. The data indicate that in both matrices, ³C₆₀ undergoes temperature dependent molecular rotation. However, whereas in the LC the rotation rate is increased monotonously between 7 and 298 K, the dynamics in toluene depends strongly on its phase diagram. About the melting point of toluene, a polarized doublet is observed concurrently with the disappearance of the triplet. At higher temperatures, where the liquid phase prevails, the dynamics of the photoinduced doublet suggests an unpaired electron delocalized on an aggregate of C₆₀ in toluene, with relatively long-lived magnetization of ∼25 μs.