Scientists in the United States and Germany have produced the smallest possible fullerene* a C₂₀ molecule. The best known fullerene is a C₆₀ molecule. Its 60 carbon atoms are arranged at the vertices of a truncated icosahedron. This shape, with 12 pentagons and 20 hexagons as faces, is familiar as a football (or soccer ball in the USA). C₂₀ has no hexagons, just the 12 pentagons.

It was known for some time that a C₂₀ fullerene was theoretically possible – SEED Expert Bernd Eggen predicted it 10 years ago – but it has been hard to produce one. One reason is that since it is smaller than other fullerenes its surface has more curvature and a greater tendency to spring open. It is also highly reactive so it tends to combine with other elements to form different molecules.

Successful production of C₂₀ was accomplished by starting with dodecahedrane, C₂₀H₂₀, a stable hydrocarbon consisting of 20 carbon atoms and 20 hydrogen atoms. In a two-step process the hydrogen atoms were replaced by bromine atoms, which have a weaker bond with carbon. Then the bromine was removed leaving C₂₀.

The C₂₀ molecules that were produced were rather unstable, but their fleeting existence was confirmed using spectroscopy.

In addition to this tiniest Bucky Ball, the researchers also generated two other forms – called "isomers" – of C₂₀, one in ring and the other shaped like a bowl.

*"Gas-phase production and photoelectron spectroscopy of the smallest fullerene, C20," Horst Prinzbach, Andreas Weiler, Peter Landenberger, Fabian Wahl, Jürgen Wörth, Lawrence T. Scott, Marc Gelmont, Daniela Olevano & Bernd V. Issendorff, Nature, Vol. 407, pp. 60 - 63, September 7, 2000, Macmillan Publishers Ltd.

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