Observation of Both Thermal First-Order and Photochemical Zero-Order Kinetics in the Rearrangement of [6,5] Open Fulleroids to [6,6] Closed Fullerenes

A series of [6,5] open fulleroids with radical stabilizing groups on the methano bridge were synthesized and their rearrangements to the more stable [6,6] closed fullerenes studied. These [6,5] open fulleroids all rearrange both by a zero-order photochemical process and by a higher energy unimolecular pathway involving disrotatory closure to the [6,5] closed fullerene, which subsequently rearranges to the [6,6] closed fullerene via a biradical-like intermediate.