Theoretical studies on benzo[1,2,4]triazine-based high-energy materials.

Density functional theory calculations of 13 aminonitro compounds based on the benzo[1,2,4]triazine fused-ring system were performed. The geometries of all 13 species were optimized at the B3LYP/6-31G(d) level of theory. In order to refine the energy values, single-point energy calculations of the species were made at the B3LYP/6-311++G(2df,2p) level. The gas-phase heats of formation of the species considered were calculated using the atom equivalent method. Condensed-phase heats of formation were calculated utilizing the heats of sublimation of the designed molecules, as evaluated during the present study. With the help of the WFA program, crystal densities of the designed compounds were predicted using the geometry of the molecule optimized at the B3PW91/6-31G(d,p) level. The stabilities and impact sensitivities of all of the compounds are discussed in the present paper in terms of the bond dissociation energy (BDE) of the trigger linkage (the longest C-NO₂ bond) and the available free space per molecule (∆V) in the unit cell of each compound. A nucleus-independent chemical shift (NICS) study was performed to assess the aromaticities of the designed molecules, and the NICS(1) values determined 1 Å above and below the plane of the ring were found to be -7.9 to -10.5, respectively, for the benzene ring and -10.7 to -11.4, respectively, for the triazine ring in the designed fused-ring molecules, showing that both rings retain their aromaticities when undergoing substitution by nitro groups. Detonation parameters of the species were calculated, and the results suggest that the designed compounds possess comparable values to those of the commercial explosives TNT and RDX. Furthermore, results suggest that the designed compounds may be less sensitive than many nitroaromatic and nitramine explosives. Thus, the results obtained during the present study imply that the designed compounds may be used as safe explosive materials, and could be potential alternatives to TNT and RDX.