High level ab initio study of singlet and triplet cyclopropene and diazocyclopropene carbenes stability in comparison with stability of singlet and triple cyclopropenyl cation and anion

Abstract

Complete basis set ab initio computational studies were performed with the target being to evaluate the aromatic character (stability) of cyclopropene, diazocyclopropene, and diazocyclopropane carbenes. Their stability was evaluated through the computed structural parameters, the evaluated enthalpies of hydrogenation, frontier molecular orbital energy gaps, and triplet–singlet energy differences. All of these results are compared to the same study performed on the well known aromatic cyclopropenyl cation and the antiaromatic cyclopropenyl anion. It was demonstrated that both singlets, cyclopropene and diazocyclopropene carbenes are aromatic, while the diazocyclopropene hydrogenated isomer should be aromatic both as a singlet and as a triplet.