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

Catalytic effects on the kinetics of the Stone-Wales fullerene transformati on are studied computationally. The catalytic agents are represented by fre e elements, neutral or charged. The computations are performed at semiempir ical (PM3) and DFT (B3LYP/6-31G*//PM3) levels on a model bowl-shaped fragme nt C34H12. The semiempirical and DFT activation energies agree reasonably w ell. In all computed cases, the activation barrier is lowered compared with that of the uncatalyzed reaction. The kinetic barriers for the catalyzed r earrangements 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) fo r the N+, N, and N- species, respectively. If the activation barriers are r e-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 amoun ts of nitrogen (as well as other elements) are available in virtually any k ind of fullerene synthesis, the study offers a computational support for ki netic feasibility of the Stone-Wales fullerene transformation. (C) 2000 Els evier Science S.A. All rights reserved.