Azidopentazole is probably the lowest-energy N-8 species - A theoretical study

Ab initio molecular orbital calculations at the quadratic configuration interaction [QCISD(T)/G-31G(d)] and coupled-cluster theory [CCSD(T)/DZP] levels based on MP2/6-31G(d) optimized geometries show that azidopentazole is Likely to be the global minimum of the N-8 isomers lying 13 and 18 kcal/mol below the acyclic diazidyldiimide and the cyclic pentalene analogue, respectively. Azidopentazole is characterized by a significant energy barrier to ring closure and is expected to be stable with respect to cycloreversion and thus constitutes the most realistic N-8 target for a synthetic preparation.