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

Abstract

We present an investigation of the reaction of ozone with C₆₀ fullerene using electronic structure methods. Motivated by recent experiments of ozone exposure to a C₆₀ film, we have characterized stationary points in the potential energy surface for the reactions of O₃ with C₆₀ 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 O₃ molecules to the C₆₀ 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 C₆₀ 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 + O₂ 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 C₆₀ is unlikely even under high ozone concentration, the addition of a few ozone molecules to the C₆₀ cage is favorable at room temperature.