Thermal stabilization of energetic materials by the aromatic nitrogen-rich 4,4′,5,5′-tetraamino-3,3′-bi-1,2,4-triazolium cation

Abstract

4,4′,5,5′-Tetraamino-3,3′-bi-1,2,4-triazole (1) was prepared from readily available starting materials by a one-step procedure. Compound 1 consists of two combined aromatic triazole molecules with four amino moieties, resulting in a compound which has (i) high temperature stability, (ii) a high heat of formation, (iii) a high density and (iv) no sensitivity towards physical stimuli (friction, impact and electrostatic discharge). This compound has never previously been considered as a building block in the development of new energetic materials. We investigated compound 1 in detail as a potential nitrogen-rich, temperature-stable cation for the synthesis of energetic ionic derivatives (2–13) for use as environmentally benign explosives. The cation was combined with oxygen-rich counter-anions such as dinitramide (2), 5-nitrotetrazole-2-oxide (3), 5-nitrotetrazolate (4), nitrate (5), tetranitrobisimidazole (6), 5,5′-bitetrazole-1,1′-dioxide (7), 1,1′-dinitramino-5,5′-bitetrazolate (8), 5-nitriminotetrazolate (9), 1-methyl-5-nitriminotetrazolate (10), perchlorate (11), picrate (12) and nitroformate (13). Compounds 2–10 and 13 were characterized by low-temperature single-crystal X-ray diffraction. All the compounds were investigated by NMR and vibrational (IR, Raman) spectroscopy, mass spectrometry and elemental analysis. The excellent thermal properties of these compounds were determined by differential thermal analysis. The sensitivities towards impact, friction and electrical discharge were investigated using the BAM standards and a small-scale electrostatic discharge tester. The detonation parameters of the compounds without the inclusion of crystal water (1–3, 5–8, 11 and 13) were calculated using the EXPLO5 (V6.02) code and the calculated (CBS-4M) values for the enthalpy of formation.