Structures and kinetic stability of five N-7 isomers with low spin, including three isomers previously studied, were investigated by the second-order Mphiller-Plesset (MP2) theory and density functional theory (DFT) methods. Two open-chain structures with C-S and C-2 (or C-2v) symmetry were predicted to be local minima on the N-7 potential energy surfaces, respectively. The previously reported C-S-symmetric minimum consisting of a five-membered ring and a N-2 side chain was not found to be stable. The isomerization and decomposition pathways of the isomers were also investigated. (C) 2002 Elsevier Science B.V. All rights reserved.