A Study of 5-(1,2,4-Triazol-C-yl)tetrazol-1-ols: Combining the Benefits of Different Heterocycles for the Design of Energetic Materials

N-oxide 1,2,4,5-tetrazine-based high-performance energetic materials

One route to high density and high performance energetic materials based on 1,2,4,5-tetrazine is the introduction of 2,4-di-N-oxide functionalities. Based on several examples and through theoretical analysis, the strategy of regioselective introduction of these moieties into 1,2,4,5-tetrazines has been developed. Using this methodology, various new tetrazine structures containing the N-oxide functionality were synthesized and fully characterized using IR, NMR, and mass spectroscopy, elemental analysis, and single-crystal X-ray analysis. Hydrogen peroxide (50 %) was used very effectively in lieu of the usual 90 % peroxide in this system to generate N-oxide tetrazine compounds successfully. Comparison of the experimental densities of N-oxide 1,2,4,5-tetrazine compounds with their 1,2,4,5-tetrazine precursors shows that introducing the N-oxide functionality is a highly effective and feasible method to enhance the density of these materials. The heats of formation for all compounds were calculated with Gaussian 03 (revision D.01) and these values were combined with measured densities to calculate detonation pressures (P) and velocities (νD ) of these energetic materials (Explo 5.0 v. 6.01). The new oxygen-containing tetrazines exhibit high density, good thermal stability, acceptable oxygen balance, positive heat of formation, and excellent detonation properties, which, in some cases, are superior to those of 1,3,5-tritnitrotoluene (TNT), 1,3,5-trinitrotriazacyclohexane (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX).

Theoretical studies on the structures and detonation properties of nitro derivatives of symmetric benzo-dicycloureas

The nitro derivatives of symmetric benzo-dicycloureas were designed and optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/6-31G** level. The theoretical molecular density, heat of formation, detonation velocity, and detonation pressure, estimated using Kamlet–Jacobs equations, showed that the detonation properties of compound 7 were excellent, while compounds 8 and 9 were unstable, and the molecular symmetry, steric hindrance, and hydrogen bonds were considered to be the three main factors contributing to molecular stability. These results provide basic information for the molecular design and synthesis of novel high energy density compounds.