Isolated pentagon rule in buckybowls: a computational study on thermodynamic stabilities and bowl-to-bowl inversion barriers

Computations on a series of sumanene and pinakene isomers reveal that the isolated pentagon species are found to be more stable than non-isolated pentagon structures. However, the present study indicates that there is no correlation between the bowl-to-bowl inversion barrier and the relative stability. Unexpectedly, the least stable isomer has the lowest bowl-to-bowl inversion barrier in pinakene isomers. Thus, curvature cannot be taken as a measure to evaluate the stability of buckybowls. The relative energy ordering and HOMO–LUMO gap correlate well in the series of pinakene isomers considered.