Materials science

A stable non-classical metallofullerene family

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In the evolving field of fullerenes, nanotubes and endohedral metallofullerenes, the isolated-pentagon rule (IPR)1 is sacrosanct — exceptions have been predicted2,3, but no bare carbon cages with adjacent pentagons have been characterized. Small organic molecules with metal-stabilized fused five-membered rings (pentalenes) have been created4, however, and here we describe a family of non-classical endohedral metallofullerenes with the general structure AxSc3−xN@C68 (where x = 0–2, A is a rare-earth metal, Sc is scandium and N is nitrogen) that has a non-IPR cage of only 68 carbon atoms containing annelated five-membered rings. This internal ring network is metal-stabilized and is accessible for external organic reaction chemistry.

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Figure 1: Mass-spectral data for purified Sc3N@C68 and ErSc2@C68.
Figure 2: Three-fold symmetry isomers of C68 and proposed Sc3N@C68 structure (isomer 6,140).


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Correspondence to H. C. Dorn.

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