DFT study of fullerene dimers

Several [2+2] dimerization products of a fullerene C-n (n = 50, 52, 54, 56, 58, 60) in its most stable form are presented and discussed. In total, 34 dimes are studied. Only symmetric C-n-C-n dimers (no mixed products)are reported, and olnly dimers of the fullerenes C-50 to C-58 with bonds-between C atoms in adjacent pentagons are considered. Geometries were optimized within the framework of density functional theory using the Becke-Perdew exchange-correlation functional (BP86) in combination wit han empirical dispersive energy correction, which contributes significantly to the binding energy. The results are discussed in the context of the reactivity of adjacent pentagon sites. The lateral interaction between fullerenes is found to be stronger for C-50 to C-58 than for C-60, which is consistent with recent experimental observations. Further, the possibility of polymer formation based on the investigated [2+2] reaction is addressed.