Pyrazine-bridged polynitro triazoles for high energy and practical stability

Abstract

The design, synthesis and characterization of a symmetric, pyrazine-bridged, C–C bonded hexanitro molecule, 2,5-bis(3-(trinitromethyl)-1H-1,2,4-triazol-5-yl)pyrazine (5), together with its nitrogen-rich energetic salts (7–9), prepared from inexpensive, commercially available precursors is described. Structures were characterised by multinuclear NMR (¹H, ¹³C, ¹⁴N), IR, elemental analysis and DSC; compound 8 was further supported by ¹⁵N NMR and the structure of 5 was unambiguously established by single-crystal X-ray diffraction. Systematic evaluation of physicochemical and energetic properties reveals high densities (1.73–1.89 g cm⁻³), good thermal stability (150–215 °C), competitive detonation performance (VOD = 8093–8967 m s⁻¹; DP = 27.0–32.4 GPa) and low mechanical sensitivities (IS = 25–40 J; FS = 360 N). The neutral hexanitro compound 5 displays balanced properties (density 1.73 g cm⁻³, onset thermal decomposition 150 °C, VOD 8093 m s⁻¹ and oxygen balance OB_co ≈ 0%), while the corresponding salts (7–9) exhibit higher densities (>1.87 g cm⁻³), enhanced thermal robustness (>205 °C), superior detonation velocities (>8558 m s⁻¹) and increased resistance to mechanical stimuli (IS = 40 J). The pyrazine-bridged, C–C bonded architecture therefore gives a favorable balance of energy, thermal stability and insensitivity, suggesting a viable structural strategy for the development of next-generation, insensitive secondary energetic materials.