Isolation, characterization, and chemical reactions of fullerenes

Extension of the chromatographic work that led to the first isolation of pure C₆₀ and C₇₀ has resulted in the isolation and characterisation of C₇₆ and three isomers of C₇₈. Comparison with other work indicates the composition ratio of C₇₈ to be dependent upon the method of carbon production. Halogenation of C₆₀ gives derivatives that have been characterised either by NMR, or by single crystal X-ray diffraction. The halogeno derivatives readily undergo nucleophilic substitution, which provides a route to the formation of many fullerene compounds, but precludes use of the fluoro derivatives as lubricants. In the presence of Friedel-Crafts catalysts, the bromo derivatives substitute into aromatics to give aryl derivatives of C₆₀. especially those containing either 6, 8, 12, or 16 aryl groups per C₆₀ molecule. Possible structures for these are compared with those for addition products which have only low eclipsing steric interactions.