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.