Computational modeling of the elemental catalysis in the Stone-Wales fullerene rearrangements

Catalytic effects on the kinetics of the Stone-Wales fullerene transformation are studied computationally. The catalytic agents are represented by free elements, neutral or charged. The computations are performed at semiempirical (PM3) and DFT (B3LYP/6-31G*//PM3) levels on a model bowl-shaped fragment C34H12. The semiempirical and DFT activation energies agree reasonably well. In all computed cases, the activation barrier is lowered compared with that of the uncatalyzed reaction. The kinetic barriers for the catalyzed rearrangements increase in the following order: N, H, O, P, S, B, Cl, C, F, Li, Se, Fe, Hg, Zn, Si, Sn, Ge, Mg, and pi. Nitrogen atoms are pointed out as especially potent catalytic agents. At the PM3 computational level, the isomerization kinetic barrier is reduced to 193, 110, and 342 kJ mol(-1) for the N+, N, and N- species, respectively. If the activation barriers are re-computed at the B3LYP/6-31G*//PM3 level, they are changed to 76, 105, and 323 kJ mol(-1) for the N+, N, and N- species, respectively. As small amounts of nitrogen (as well as other elements) are available in virtually any kind of fullerene synthesis, the study offers a computational support for kinetic feasibility of the Stone-Wales fullerene transformation. (C) 2000 Elsevier Science S.A. All rights reserved.