Fullerene Isomerism: Isolation of C2v,-C78 and D3-C78

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Science  20 Dec 1991:
Vol. 254, Issue 5039, pp. 1768-1770
DOI: 10.1126/science.254.5039.1768


Early reports on the formation of the higher fullerenes C76, C78, C84, C90, and C94 by resistive heating of graphite stimulated theoretical calculations of possible cage structures for these all-carbon molecules. Among the five fullerene structures with isolated pentagons found for C78, a closed-shell D3h-isomer was predicted to form preferentially. Two distinct C78-isomers were formed in a ratio of ∼5:1 and could be separated by high-performance liquid chromatography. The carbon-13 nuclear magnetic resonance (NMR) spectrum of the major isomer is uniquely consistent with a C2v-structure. The NMR data also support a chiral D3-structure for the minor isomer. The isolation of specifically these two isomers of C78 provides insight into the stability of higher fullerene structures and into the mechanism for fullerene formation in general.

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