Methylation of a triazole-fused framework to create novel insensitive energetic materials

Abstract

In this study, the insensitive material 3,7-diamino-6-methyl-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazole (3), and a series of its energetic salts, were synthesized. 3-nitroimino-6-methyl-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazole (4) was obtained by the direct nitration of the hydrochloride of compound 3. All the compounds were exhaustively characterized by NMR spectroscopy, IR spectroscopy, differential scanning calorimetry (DSC), and elemental analyses. The structures of 4·H2O, 5, and 8 were further verified by single-crystal X-ray diffraction. Compounds 3–10 exhibited acceptable thermal stability, with decomposition temperatures in the range of 179–289 °C, except for 4 (119 °C), 9 (133 °C), and 10 (151 °C). All the compounds synthesized herein were less sensitive than RDX. The hydrazine salt 9 possessed the highest detonation velocity (8626 m·s everywhere in the article−1), and the other compounds delivered superior detonation performances (D = 7784–8575 m s−1, p = 20.7–28.7 GPa) to that of TNT (D = 6881 m s−1, p = 19.5 GPa). Based on experimental results and theoretical analysis, this study will provide an effective approach for designing insensitive energetic materials.