Diabolus in Chemistry?

This article explores the possible presence of a pentacle valence bond structure in C$_5$ cyclic molecules. At this end, we have used quantum chemistry tools to elucidate the possible arrangement and the nature of chemical bonds within linear, cyclic, and three-dimensional structures only formed by five carbon atoms. While the linear structure is clearly the most stable one, local minima were obtained for both bi- and three-dimensional structures. Beyond the historical satanic symbol, the pentacle arrangement corresponds to an unusual formal structure with five crossing between C-C bonds. Our calculations show that this diabolic cyclic C$_5$ scheme is a relevant resonant structure and, furthermore, it is also present in the more known cyclo-pentadienyl molecule.