The properties of 21 molecules related to azapentalenes and their conjugated acids have been calculated: energies, dipole moments, natural bond orders, bond lengths, bond critical points, HOMA, and NICS. The ring-opening processes of dioxopyrazolo[1,2-a] pyrazolium and pyrazolo[1,2-a][1,2,4]triazol-4-ium into ketenes and isocyanates have been studied. The calculations were carried out at the B3LYP/6-311++G(d,p) level. © 2009 Elsevier Ltd. All rights reserved.Peer Reviewe