Bond Lengths in Free Molecules of Buckminsterfullerene, C 60 , from Gas-Phase Electron Diffraction

Abstract

Electron diffraction patterns of the fullerene C₆₀ in the gaseous state have been obtained by volatilizing it from a newly designed oven-nozzle at 730°C. The many peaks of the experimental radial distribution curve calculated from the scattered intensity are completely consistent with icosahedral symmetry for the free molecule. On the basis of this symmetry assumption, least-squares refinement of a model incorporating all possible interatomic distances led to the values r_g(C₁-C₂) = 1.458(6) angstroms (Å) for the thermal average bond length within the five-member ring (that is, for the bond fusing five- and six-member rings) and r_g(C₁-C₆) = 1.401(10) Å for that connecting five-member rings (the bond fusing six-member rings). The weighted average of the two bond lengths and the difference between them are the values 1.439(2) Å and 0.057(6) Å, respectively. The diameter of the icosahedral sphere is 7.113(10) Å. The uncertainties in parentheses are estimated 2σ values.