VERSATILE NITRONIUM CHEMISTRY FOR C-60 FULLERENE FUNCTIONALIZATION

We have demonstrated the high reactivity of fullerene molecules toward the electrophilic attack of the nitronium ion in the presence of nucleophilic reagents, such as aromatic carboxylic acids, under mild reaction conditions. The observed nucleophilicity of fullerenes in terms of their vulnerability to electrophilic additions in solution compensates for difficulties that have been encountered in achieving the electronic oxidation of C60 molecules for further functionalization. It also represents a versatile synthetic methodology for introducing multiple polar functionalities, especially hydroxyl and functionalized carboxylic ester groups, onto fullerene molecules, leading to an enormous variation of novel fullerene derivatives. The structure of these new fullerene derivatives was characterized as consisting of a chemical composition of an average of 13-15 hydroxyl substituents and 4-5 p-bromobenzoate moieties per C60 molecule. Hydrolysis of these derivatives in alkaline aqueous solution affords the corresponding water-soluble fullerols consisting of 18-20 hydroxyl groups per C60 molecule on average.