Isolation of C76, a chiral (D2) allotrope of carbon

The isolation and characterization of the C76 molecule, a third molecular form of carbon following C60 and C70, are reported. Substantial quantities of this species were isolated and purified using an extraction technique of Kratschmer et al. (1990) together with chromatography. The C-13 NMR spectrum consists of 19 lines of essentially equal intensity, confirming a compact, cagelike fullerene structure. The spectrum is uniquely consistent with the remarkable structure predicted by theoretical calculations by Manolopolous, a chiral structure with D2 symmetry consisting of a spiralling, double-helical arrangement of edge-sharing pentagons and hexagons. (C.D.)