Quantum Chemical Studies on Energetic Azo-Bridged Azoles

Azo-bridged azole derivatives were designed and investigated in order to find comprehensive relationship between the structure and performance of nitrogen-rich energetic compounds. Density functional theory (DFT) was used to predict the optimized structures, heat of formation, and detonation properties. Introduction of the azido group greatly enhances the heat of formation of these derivatives due to the high energy contribution from the -N3 group. The crystal density was predicted by using the DREIDING force field. The nitroazoles show higher densities than amino and azido derivatives and hence better detonation performance. Thermal stability was analyzed using bond dissociation energies of C-NO2, C-NH2, and C-N3 bonds. Nucleus-independent chemical shifts (NICS) were calculated at the ring centers to find the stability via aromaticity. The sensitivity of the designed compounds were predicted on the basis of band gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital. The amino derivatives were found to be more stable and less sensitive than the designed compounds.