Design and density functional theoretical study of three novel pyrazine-based high-energy density compounds

Three novel high-energy density compounds – 2,6-diazido-3,5-dinitropyrazine (AzNPZ), 2,6-diazido-3,5-dinitropyrazine-1-oxide (AzNPZO1) and 2,6-diazido-3,5-dinitropyrazine-1,4-dioxide (AzNPZO2) were designed. The stable geometries of the three compounds were optimized at B3LYP/6-31G∗∗ theoretical level. Their IR spectra were obtained on the basis of vibrational analysis calculations. The bond dissociation energies (BDEs) outside of the pyrazine-cycles were computed. The densities, solid-phase enthalpies of formation and detonation characters were predicted. The results show that the N-oxides mainly affect the bond lengths in the pyrazine-cycles and result in the pyrazine-cycles closed to be coplanar. The azido groups and the pyrazine-cycles are close to be in the same plane, but it is difficult for the O atoms in the −NO2 groups and the pyrazine-cycles to be in the same plane. The frequency ranges of infrared absorption are consistent on the whole, but the N-oxides still affect some characteristic absorption bands shifting. Large BDEs indicate the high thermal stabilities of these compounds, and the N-oxides in pyrazine-cycles decrease the thermal stabilities. The detonation properties will be improved when the nitrogen atoms in pyrazine-cycles are oxidated, and fully match the criterion of high-energy density compounds.