Nitro-based and nitro-free tri-cationic azole salts: a unique class of energetic green tri-ionic salts obtained from the reaction with nitrogen-rich bases

Abstract

Nitrogen-rich heterocycles are essential for designing novel energetic green materials with the combination of high explosive performance and acceptable mechanical sensitivities. In this work, two sets of high nitrogen-azoles, derived from tetrazoles and triazole assemblies with N-trinitromethane, 5,5′-(2-(trinitromethyl)-2H-1,2,3-triazole-4,5-diyl)bis(1H-tetrazole) (TBTN) and N-methylene tetrazole, 5,5′-(2-((1H-tetrazol-5-yl)methyl)-2H-1,2,3-triazole-4,5-diyl)bis(1H-tetrazole) (TBTT) are described. Their molecular structures were confirmed using multinuclear (¹H, ¹³C, and ¹⁵N) NMR spectra and single-crystal X-ray diffraction analysis. These molecules are attention attracting results emanating from methodologies utilized to access a unique class of tri-ionic salts in reaction with nitrogen-rich bases. The thermostabilities, mechanical sensitivities, and detonation properties of all new compounds were determined. Surprisingly, the nitro-based tri-cationic salts, 5b (Dv = 9376 m s⁻¹) and 5c (Dv = 9418 m s⁻¹), have excellent detonation velocities relative to HMX (Dv = 9144 m s⁻¹), while those of the nitro-free tri-cationic salts, 8b·H₂O (Dv = 8998 m s⁻¹) and 8c·0.5H₂O (Dv = 9058 m s⁻¹), are superior to that of RDX (Dv = 8795 m s⁻¹) and approach HMX values. Additionally, nearly all new compounds are insensitive to mechanical stimuli because of the high percentage of hydrogen bond interactions (HBs) between the anions and cations, which are evaluated using two-dimensional (2D) fingerprint and Hirshfeld surface analyses. It is believed that the work presented here is the first example of high-performing and insensitive tri-cationic energetic salts, which may establish a discovery platform for the “green” synthesis of future energetic materials.