Computations of the catalytic effects in the Stone-Wales fullerene isomerizations: N and CN agents

The Stone-Wales rearrangement has long been considered as a plausible, albeit hypothetical, mechanism for fullerene annealing and isomerizations. In the view of a recently applied new catalyst, KCN, for incorporation of noble gases in fullerenes, the CN radical is studied here computationally as a possible catalytic species acting in kinetics of the Stone-Wales fullerene transformation, and a possible role of K ⁺ is also investigated. The computations are performed on the PM3-optimized bowl-shaped model C ₃₄H ₁₂ to which the CN radical is attached by its C or N atom. The activation energies are evaluated at the UPM3, UHF/6-31G*, UB3LYP / 6-31G*, ROB3LYP/6-31G*, ROHF/6-31G**, and ROB3LYP/6-31G** levels. However, the reduction of the kinetic barrier owing to the catalyst action is modest so that a free N atom, neutral or charged, still remains a more efficient option. Effects of negatively charged CN species and of K ⁺ are also found insufficient. Small amounts of nitrogen are indeed always present during fullerene synthesis, especially from He gas.