Characterization and Energetic Property Evaluation of Novel Energetic Salts and Co-Crystals Formed with Nitropyrazoles and Pyridines

Nitropyrazoles are promising candidates to replace conventional explosives as they generally have positive heats of formation, good thermal stabilities, low friction and impact sensitivities and high energetic performance. In this study, 3,5-dinitropyrazole (DNP) and 3,4,5-trinitropyrazole (TNP) were combined with a series of pyridine derivatives to create nine new multicomponent crystals. Single-crystal X-ray diffraction shows that the herringbone-type packing observed in both DNP and TNP can be significantly altered to form puckered, wave-like and layered packing motifs. Differential scanning calorimetry and thermogravimetric analysis measurements show significant alteration in the thermal properties of the new materials, suggesting that the processing and energetic properties of DNP and TNP can be efficiently tuned through multicomponent crystallization. Preliminary impact sensitivity measurements performed on some of the materials also suggest that the mechanochemical responses of DNP and TNP can be altered through changing the crystal packing motifs. Overall, this study highlights the important role that multicomponent crystallization can play in tuning the structure/materials property relationships in energetic materials research.