Classical isomers of fullerenes usually obey the pentagon adjacent penalty rule. However, density functional theory calculations demonstrate that an isomer of fullerene C-60 with 15 pentagon-pentagon fusions is lower in energy than any isomer of C-60 with 14 pentagon-pentagon fusions and thus violates the established pentagon adjacent penalty rule. Further examination demonstrates that this isomer follows the spherical rule; however it is anti-aromatic with positive nucleus-independent chemical shifts at the cage center and most ring centers. The calculations show that hydrogenation and cluster encapsulation are both highly exothermic and demonstrate that this isomer may be captured in the form of its derivatives. (c) 2012 Elsevier B.V. All rights reserved.