Resilience of the fullerene cage: analysis of distortions in computed structures of fullerene derivatives

Abstract

The extent of cage distortion in a number of structures of fullerene derivatives, C₆₀H_60-6n (n = 0-8), optimized using the MNDO procedure is evaluated. Isomers containing isolated benzenoid rings distributed over the fullerene framework with the highest possible symmetry have been considered. For C₆₀H₂₄, C₆₀H₃₆ and C₆₀H₄₈, T_h symmetry structures with localized double bonds also have been analyzed. The fullerene cage is indicated to withstand severe distortions following derivatization, with all calculated structures being true minima with a Hessian of zero. Particularly large deviation of the carbon framework from the spheroidal shape is found in C₆₀H₃₀, C₆₀H₃₆ and C₆₀H₄₂, which are nonetheless computed to be relatively stable. Cage distortions have been quantified in terms of moments of inertia values. For a given hydride, the isomer with the lower average moment of inertia is more stable. Further, along the series C₆₀ to C₆₀H₆₀, successive hydrogenation is energetically favorable when the increase in cage moment of inertia is smaller.