Aromaticity and kinetic stability of fullerene C₃₆ isomers and their molecular ions.

The aromatic character of fullerene C(36) isomers was examined by the Hess-Schaad resonance energy (HSRE), topological resonance energy (TRE) and the percentage topological resonance energy (%TRE) models. According to the nucleus-independent chemical shift (NICS) at the cage center, C(36) fullerene isomers must be highly aromatic with negative values. However, they are predicted to be antiaromatic with negative HSREs and negative TREs. The TRE method revealed that they all are aromatized by acquiring two or more electrons. NICSs at the cage center and the 2(N + 1)(2) rule cannot be used as an indicator of the aromatic stabilization for C(36) isomers and their molecular ions. We utilized the bond resonance energy (BRE) model to estimate the kinetic stability of C(36) isomers and their molecular ions. C(36) isomers are only stabilized kinetically in penta- and hexavalent molecular anions. All the results indicate that aromaticity and kinetic stability are closely related to the cyclic motion of π electrons.