SINGLE-CRYSTAL STRUCTURE OF C-60 AT 300-K - EVIDENCE FOR THE PRESENCEOF OXYGEN IN A STATICALLY DISORDERED MODEL

The structure of solvent-free single crystals of sublimed C-60 has bee n analysed at 300 K by X-ray diffraction. A unique solution of atom co ordinates gave a satisfactory agreement with the intensity data. This indicates that the C-60 balls exhibit a time-averaged preferred positi on in the crystals which are, however, heavily affected by rotational disorder. The structure reveals the truncated icosahedral molecular sh ape with two sets of carbon-carbon bond distances. Contour plots indic ate the anisotropic distribution of electron density within the almost perfectly spherical shell of the molecule. The analytically pure crys tals contained an impurity of molecular oxygen located statistically o ver some hexagons of each 'buckyball' resulting in a limiting stoichio metry of C-60 O-2.