Decomposition mechanism of the polynitrogen N5 and N6 clusters and their ions

The decomposition mechanism of the pentanitrogen (N5, N5−, N5+) and hexanitrogen (N6, N6+, N6−) clusters and their ions was studied using ab initio MO calculations up to the CCSD(T) level with 6-311+G(3dp) and aug-cc-pVTZ basis sets and also DFT/B3LYP method. While the cyclic anion N5− and open-chain cation N5+ are relatively stable with respect to elimination of N2, the neutral N5 radical does not exist as a discrete species. The elimination of two N2 molecules in the neutral N6 is found to be a concerted process, whereas that in the ionized N6+ cluster is stepwise due to the existence of a N4+ ion. The fragmentation of a N6 cluster into two azide (N3) fragments is, irrespective of its charge state, also a facile process, making them, at most, metastable molecules. Different thermochemical parameters of these Nn species have also been evaluated.