Analysis of Isomers of the Higher Fullerenes by 3He NMR Spectroscopy

The high-pressure, high-temperature {sup 3}He labeling procedure previously used with C{sub 60} and C{sub 70} was applied to mixtures of isomers of the higher fullerenes C{sub 76}, C{sub 78}, and C{sub 84}. Sufficient helium was introduced inside them to allow helium NMR spectra to be obtained. Each isomer yields a single, sharp, characteristic NMR peak resolved from the others. Our results show that there are more isomers of these fullerenes than previously reported. Three C{sub 78} isomers and three C{sub 84} isomers have been described, but we have shown that there are at least five C{sub 78} isomers and nine C{sub 84} isomers. 39 refs., 2 figs., 1 tab.