Energetic Nitrated Azole Assemblies: Linear Alliance of Isomeric Furazan-1,2,4-triazole-pyrazole Combinations

Abstract

While the effect of isomerism on the properties of energetic molecules has long been recognized, the use of this phenomenon to deliberately improve the performance of energetic materials has now been approached. Here, we report the development of effective protocols for the preparation of isomeric energetic compounds with a furazan-triazole-pyrazole framework, which differ in the binding points of these subunits and in the position of the nitro group. The two synthesized isomers readily form X-ray quality crystals of solvates with DMSO and water, but only one isomer was able to give unsolvated crystals. Significant differences in molecular geometry and noncovalent interactions due to the effect of the solvent incorporated into the crystal lattice are highlighted. The ambiguity of evaluating structure–property relationships for a single compound from the X-ray data of its solvate is demonstrated. The isomer synthesized for the first time, 3-(5-(5-(3,4-dinitro-1H-pyrazol-5-yl)-1H-1,2,4-triazol-3-yl)-4-nitrofurazan (6), is of greater interest because, unlike the other isomer, it is not hygroscopic and has a higher density. Isomer 6 has a shock sensitivity and detonation velocity similar to those of RDX, but it is more thermally stable and insensitive to friction.