A theoretical study of highly nitrated azacubanes

The geometries of highly nitrated azacubanes have been fully optimized at the B3LYP/6-31++G** theory level, and the gas phase enthalpies of formation have been obtained by designing the isodesmic reaction in which the azacubane cage skeleton is not destroyed. An efficient procedure for judging the driving force of detonation products of energetic compounds has been developed from the conservation of energy condition. The MP2/6-31++G**//B3LYP/6-31++G** atom-atom overlap-weighted NAO bond order shows that after the full nitration of 1,4-diazacubane and 1,3,5,7-tetraazacubane the weakest C-N bond on the 1,3,5,7-tetraazacubane cage skeleton strengthens slightly, but on the 1,4-diazacubane cage skeleton it weakens. For highly nitrated azacubanes, the introduction of -NH2 group results in the destabilization of the neighboring C-N bond on the cage skeleton. The shock stability of 2,4,6,8-tetranitro-1,3,5,7-tetraazacubane (TNTAzC) is superior to that of 2,3,5,6,7,8-hexanitro-1,4-diazacubane (HNDAzC). The detonation velocity and pressure for TNTAzC are predicted to reach 11.10 km/s and 101.7 GPa, respectively. The driving force of detonation products of HNDAzC is close to that of octanitrocubane, and the driving force of TNTAzC is about 4.0 times as large as that of the widely used high explosive HMX, showing that TNTAzC is a potential candidate of super high-energy compound.