Experimental detection of theoretically predicted N2CO

Since “metastability” drew special attention as an energy storage medium, much theoretical and experimental effort has been devoted to the study of the isoelectronic N4, N2CO and C2O2 molecules. The largest amounts of energy released per mass unit by dissociation of tetraazatetrahedrane N4 (Td) (200 kcal mol-1), diazirinone N2CO (100 kcal mol-1), ethylenedione C2O2 (70 kcal mol-1), and other theoretically predicted isomers, prompted intense scrutiny of these 28-electron molecules as leading candidates for highly energetic materials. After the recent experimental discovery of the open-chain N4 and the ultimate answer to the long standing challenge of C2O2, the question remains whether bound, high-energy N2CO species can be experimentally observed. Ab initio calculations at different levels of theory predict that three N2CO species are potentially observable: the singlet C2v diazirinone, that is the most stable N2CO isomer, the triplet open-chain NNCO, and a strained tetrahedrane-like structure, whose “accumulated” energy (about 220 kcal mol-1) would be higher than that of N4 (Td). Despite the promising predictions, N2CO has so far eluded experimental detection, defying all attempts at its characterization as a bound species. We here report on the preparation, positive detection and characterization of N2CO, by the one-electron reduction of the N2CO+ cation, a result achieved utilizing the neutralization-reionization mass spectrometry (NRMS), the technique of choice for detection of transient and elusive neutrals.