N-Methylene-C-linked nitropyrazoles and 1,2,4-triazol-3-one: thermally stable energetic materials with reduced sensitivity

Abstract

Recently, there has been a surge in research focusing on triazolone-based energetic materials, propelled by their remarkable properties such as good detonation performance as well as acceptable thermal and physical stability. In this work, a novel combination of the triazolone framework with dinitropyrazoles has been attained using the N-methylene-C-linked approach. Different substituents (NH₂, NO₂, N₃, OH) were utilized on the dinitropyrazole moiety to obtain neutral energetic compounds 3–5 and 8. Furthermore, the hydroxy derivative (compound 8) facilitates the formation of energetic salts 9–13 to fine-tune the overall properties further. All the novel compounds 3–13 were thoroughly characterized by IR, multinuclear NMR spectroscopy, high-resolution mass spectrometry (HRMS), and elemental analysis. Compounds 3, 4, 8, and 10 were further confirmed via¹⁵N NMR spectroscopy. The structure of compounds 3 and 8 was also confirmed through single-crystal X-ray diffraction studies. The majority of synthesized compounds showed good thermal stability as well as insensitivity toward external stimuli. Computational studies, including analyses such as Hirshfeld surface, non-covalent interaction, electrostatic potential surface, and HOMO–LUMO analysis, were conducted to examine the influence of substitution at the 4th position on the overall stability of compounds 3, 4, and 8.