A computer-aided quantum chemical study of the N₁₅^- cluster

Ab initio (RHF, MP2) and Density Functional Theory (DFT) methods have been used to examine six isomers of the N₁₅^- cluster with the 6-31+G* basis set. Different from the known odd-numbered anionic N₇^-, N₉^-, and N₁₁^- clusters, in which the open-chain structures are the most stable species, the most stable N₁₅^- isomer is structure 1 (C₁), which may be considered as a complex between the fragments cyclic N₅ (D_5h) and staggered N₁₀ (D_2d). The decomposition pathways of structure 2 (C_S), containing two aromatic N₅ rings connected by a N₅ chain, and the open-chain structure 3 (C_2v were studied at the B3LYP/6-31+G* level of theory. Relative energies were refined at the level of B3LYP/6-311+G(3df,2p)// B3LYP/6-31+G*+ZPE (B3LYP/6-31+G*). The barriers for N₂ and N₅^- (D_5h) fission reactions for structure 2 are predicted to be 18.2 and 14.2 kcal mol^-1, respectively. The corresponding N₂+N₃^- fission barrier for structure 3 is predicted to be 11.2 kcal mol^-1. Supplementary material is available for this article if you access the article at http://dx.doi.org/10.1007/s00894-003-0118-0. A link in the frame on the left on that page takes you directly to the supplementary material.