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.