THE FULLERENES - POWERFUL CARBON-BASED ELECTRON-ACCEPTORS

The gaseous, solution and solid state experimental evidence for electron addition to the fullerenes is reviewed and it is shown that this class of molecules function as powerful electron acceptors. The topological character of C60 as described by Huckel molecular orbital theory suggests that the molecule will undergo facile reduction, but comparisons with planar conjugated hydrocarbons show that this feature alone cannot account for the very low half-wave reduction potential of C60. Because of the curvature of the surface, fullerene hybridization falls between graphite (sp2) and diamond (sp3) and these new carbon allotropes are therefore of intermediate, and perhaps variable hybridization. According to POAV1 theory the carbon atoms in C60 are of sp2.28 hybridization. It is concluded that rehybridization plays an important role in determining the electronic structure of the fullerenes and it is the combination of topology and rehybridization that together account for the extraordinary ability of C60 to accept electrons.