Do nitrogen-containing oxocarbons exist? Predictions of their stability and aromaticity

Density functional theory has been used to investigate the structure, stabi lity and aromaticity of a series of nitrogen-containing oxocarbons, which a re related to CnOn2- (n = 3-6). We have identified a large number of minimu m-energy species which might be synthesized and calculated their aromaticit y using the nucleus-independent chemical shift method of Schleyer. Successi ve substitution of carbon by nitrogen reduces their stability, as reflected in the calculated bond orders and dissociation energies. In general, there is no close correlation between the stability and pi -aromaticity of the s pecies studied.