Various cyclic N-8 isomers are considered at the levels of B3LYP/6-311 ++G(d,p) and B3LYP/cPVTZ. Some energies and molecular orbital properties are obtained. The structures are found to be stable in the singlet state but mostly unstable in the triplet. The heats of formation values calculated by means of T1 recipe reveals that they are highly endothermic. NICS(0) values have been calculated and aromaticity/antiaromaticity of the rings are discussed. Additionally, theoretical IR, UV-VIS spectra and the calculated impulse values have been obtained. (C) 2018 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.