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

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