Abstract

Before the discovery of C₆₀ (Kroto et al. 1985), the existence of truncated icosahedron composed of carbon and hydrogen atoms C₆₀H₆₀ was pointed out (Yoshida and Osawa 1971). Yoshida and Osawa proposed that this molecule might exist if all carbon atoms in C₆₀H₆₀ have sp² hybridized orbitals. They also pointed out that the molecule might have aromaticity (super-aromaticity). Actually, the discovered truncated icosahedron was not C₆₀H₆₀ but C₆₀; however, what is noteworthy is that fullerene structure had been proposed more than 15 years before its actual discovery. Although the existence of a curious-shaped molecule had been revealed, the investigation of C₆₀ did not gain momentum until 1990 when Krätschmer and his coworkers invented a C₆₀ mass production method (Krätschmer et al. 1990). Before the advent of the mass production method, the quantity of fullerenes (C₆₀ or C₇₀) was so microscopic that investigation on the solid state nature of fullerenes was virtually impossible.