Spiraling fullerene.

The latest twist in the rapidly unfolding tale of fullerenes is the discovery of one that looks a bit cockeyed. Chemists have speculated on the shapes of these all-carbon molecules, but until now they had isolated and examined the structure of only two members of the fullerene family: the soccerball-shaped, 60-carbon buckyball and its rugbyball-shaped, 70-carbon cousin (SN: 8/24/91, p. 120).

Researchers at the University of California, Los Angeles, have now purified a 76-carbon fullerene with an intriguing corkscrew configuration.

Whereas the buckyball sports a completely symmetric lattice of five- and six-member carbon rings, nuclear magnetic resonance spectroscopy indicates that [C.sub.76]'s atoms form a different sort of compact carbon cage. This fullerene's 28 carbon hexagons attach as if there were two chains of rings that spiral around each other, the team reports in the Sept. 12 NATURE. This slight twisting, they say, means that [C.sub.76] has both right- and lefthanded versions, or isomers. Materials with such configurations tend to have interesting optical, chemical and electronic properties, the scientists note.

This way of fitting together also suggests that "you can build these things of any length," says study coauthor Robert L. Whetten. The UCLA team has since determined that [C.sub.84] has a similar structure, he adds. In theory, says Whetten, chemists could fashion a fullerene molecule into a millimeter-long carbon fiber, with pentagons capping the ends.