Synthesis of Fullerenones through Peroxide-Mediated Stepwise Cleavage of Fullerene Skeleton Bonds and X-ray Structures of Their Water-Encapsulated Open-Cage Complexes
2007-12-26T00:00:00Z (GMT) by
Fullerene skeleton modification has been investigated through selective cleavage of the fullerene carbon−carbon bonds under mild conditions. Several cage-opened fullerene derivatives including three fullerenones with an 18-membered-ring orifice and one fullerenone with a 19-membered-ring orifice have been prepared starting from the fullerene mixed peroxide 1, C60(OOtBu)6. The prepositioned tert-butyl peroxy groups in 1 serve as excellent oxygen sources for formation of hydroxyl and carbonyl groups. The cage-opening reactions were initiated by photoinduced homolysis of the tBu−O bond, followed by sequential ring expansion steps. A key step of the ring expansion reactions is the oxidation of adjacent fullerene hydroxyl and amino groups by diacetoxyliodobenzene (DIB). Aminolysis of a cage-opened fullerene derivative containing an anhydride moiety resulted in multiple bond cleavage in one step. A domino mechanism was proposed for this reaction. Decarboxylation led to elimination of one carbon atom from the C60 cage and formation of fullerenones. The cage-opened fullerenones were found to encapsulate water under mild conditions. All compounds were characterized by spectroscopic data. Single-crystal structures were also obtained for five skeleton-modified derivatives including two water-encapsulated fulleroids.