Syntheses, crystal structures, and energetic properties of four cyclo-pentazolate salts [NHn(CH3)4-n]+N5− (n = 0∼3)

The formation of non-metallic pentazolate salts from the combination of simple nitrogen-rich cations with cyclo -N 5 − is expected to be applied in propellants and explosives. In this work, a series of structurally similar cations ([NH 3 CH 3 ] + , [NH 2 (CH 3 ) 2 ] + , [NH(CH 3 ) 3 ] + , and [N(CH 3 ) 4 ] + ) were used to synthesize four cyclo -N 5 − containing energetic salts, and the contribution of crystal stacking mode, hydrogen bonding, C–H··· π and π -stacking interactions in the stabilization of cyclo -N 5 − salts has been investigated by geometrical and Hirshfeld surface analyses as well as theoretical calculations. All salts have been thoroughly characterized by single-crystal X-ray diffraction, infrared (IR), multinuclear NMR ( 1 H and 13 C) spectroscopy, and elemental analysis. The decomposition temperatures of all salts are higher than 75 °C, as measured by thermogravimetric (TG). These compounds all show low sensitivities (IS ≥ 35 J, FS > 360 N) measured by standard BAM methods. Their heats of formation and detonation performances were calculated using the Born–Haber energy cycle and K-J method (“Pilem” program), respectively. This study has great significance for future design and synthesis of cyclo -N 5 − containing energetic materials.