A theoretical study of the ozonolysis of C60: primary ozonide formation, dissociation, and multiple ozone additions

We present an investigation of the reaction of ozone with C-60 fullerene using electronic structure methods. Motivated by recent experiments of ozone exposure to a C-60 film, we have characterized stationary points in the potential energy surface for the reactions of O-3 with C-60 that include both the formation of primary ozonide and subsequent dissociation reactions of this intermediate that lead to C-C bond cleavage. We have also investigated the addition of multiple O-3 molecules to the C-60 cage to explore potential reaction pathways under the high ozone flux conditions used in recent experiments. The lowest-energy product of the reaction of a single ozone molecule with C-60 that results in C-C bond breakage corresponds to an open-cage C60O3 structure that contains ester and ketone moieties at the seam. This open-cage product is of much lower energy than the C60O + O-2 products identified in prior work, and it is consistent with IR experimental spectra. Subsequent reaction of the open-cage C60O3 product with a second ozone molecule opens a low-energy reaction pathway that results in cage degradation via the loss of a CO2 molecule. Our calculations also reveal that, while full ozonation of all bonds between hexagons in C-60 is unlikely even under high ozone concentration, the addition of a few ozone molecules to the C-60 cage is favorable at room temperature.