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  1. Abstract

    Nitrogen‐rich energetic materials based on five‐membered azoles, such as tetrazoles, triazoles, oxadiazoles, pyrazoles, and imidazoles, have garnered significant attention in recent years due to their environmental compatibility while maintaining high performance. These materials, including explosives, propellants, and pyrotechnics, are designed to release energy rapidly and efficiently while minimizing the release of toxic or hazardous byproducts and have attracted potential applications in the defense and space industries. The presence of extensive NC, NN, and NN high energy bonds in azoles provides high enthalpies of formation and facilitates intermolecular interactions through π‐stacking which may help with reducing sensitivity to external stimuli. Now, we report on the synthesis and energetic properties ofN‐(5‐(1H‐tetrazol‐5‐yl)‐1,3,4‐oxadiazol‐2‐yl)nitramide (5) and its energetic salts. These new high nitrogen–oxygen‐containing materials have attractive feature applications of insensitivity and increased performance.

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  2. Nitrogen-rich heterocycles are essential for designing novel energetic green materials with the combination of high explosive performance and acceptable mechanical sensitivities. In this work, two sets of high nitrogen-azoles, derived from tetrazoles and triazole assemblies with N -trinitromethane, 5,5′-(2-(trinitromethyl)-2 H -1,2,3-triazole-4,5-diyl)bis(1 H -tetrazole) (TBTN) and N -methylene tetrazole, 5,5′-(2-((1 H -tetrazol-5-yl)methyl)-2 H -1,2,3-triazole-4,5-diyl)bis(1 H -tetrazole) (TBTT) are described. Their molecular structures were confirmed using multinuclear ( 1 H, 13 C, and 15 N) NMR spectra and single-crystal X-ray diffraction analysis. These molecules are attention attracting results emanating from methodologies utilized to access a unique class of tri-ionic salts in reaction with nitrogen-rich bases. The thermostabilities, mechanical sensitivities, and detonation properties of all new compounds were determined. Surprisingly, the nitro-based tri-cationic salts, 5b (Dv = 9376 m s −1 ) and 5c (Dv = 9418 m s −1 ), have excellent detonation velocities relative to HMX (Dv = 9144 m s −1 ), while those of the nitro-free tri-cationic salts, 8b·H2O (Dv = 8998 m s −1 ) and 8c·0.5H2O (Dv = 9058 m s −1 ), are superior to that of RDX (Dv = 8795 m s −1 ) and approach HMX values. Additionally, nearly all new compounds are insensitive to mechanical stimuli because of the high percentage of hydrogen bond interactions (HBs) between the anions and cations, which are evaluated using two-dimensional (2D) fingerprint and Hirshfeld surface analyses. It is believed that the work presented here is the first example of high-performing and insensitive tri-cationic energetic salts, which may establish a discovery platform for the “green” synthesis of future energetic materials. 
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  3. 1-Amino-1-hydrazino-2,2-dinitroethylene (HFOX) is a potential reactive intermediate for a new class of energetic materials. Now we describe its condensation with various carbonyl compounds in the presence of acidic and basic catalysts. Condensation of HFOX with α-diones and β-diones gives products of much interest. α-Diones undergo cyclization in the presence of base to form six-membered ring products, while β-diones cyclize to five-membered ring products in the presence of acid. One of the exciting reactions is the formation of ammonium (5,6-dimethyl-1,2,4-triazin-3-yl)dinitromethanide salt, 5c, which was isolated by using aqueous ammonia as a nucleophilic base. All new compounds were fully characterized by advanced spectroscopic techniques. The structures of 5, 5c, 5e, 9, 11, and 12a are supported by single crystal X-ray diffraction analysis. Most of the new six membered ring compounds have good thermostabilities (>200 °C), while the fluorinated five membered ring compound, 12b, has the highest density of 2.04 g cm −3 at 25 °C. Heats of formation and detonation properties were calculated by using Gaussian 03 and EXPLO5 software programs. Nearly all new compounds have very good detonation properties, especially, triazine salts, 5e ( D v = 7513 m s −1 ; P = 24.45 G P a), and 5f ( D v = 7948 m s −1 ; P = 26.27 G P a) as well as azide derivative 11 ( D v = 8166 m s −1 ; P = 25.48 G P a), which are superior to TNT ( D v = 6824 m s −1 ; P = 19.40 G P a). These findings provide a new perspective for the synthesis of novel high performing energetic materials. 
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  4. Trinitromethane moieties are very important for the design and development of high performing dense green oxidizers. The novel oxidizer 1,2-bis(5-(trinitromethyl)-1,2,4-oxadiazol-3-yl)diazene, 14 is stable in water in contrast to 1,2,4-oxadiazoles with other electron withdrawing substituents at the C5-position. Compound 14 is a CNO-based oxidizer with positive oxygen balance (+6.9%), moderate thermostability, and mechanical insensitivity that may find useful applications in the field of green rocket propallant. 
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