Construction of Coplanar Bicyclic Backbones for 1,2,4-Triazole-1,2,4-Oxadiazole-Derived Energetic Materials

Combining different nitrogen-rich heterocycles into a molecule can fine-tune its energetic performance and physical properties as well as its safety for use in energetic materials. Here, 1,2,4-oxadiazole was incorporated into 1,2,4-triazole to construct new energetic backbones. 3-(5-Amino-1H-1,2,4-triazol-3-yl)-1,2,4-oxadiazol-5-amine (5) was designed and synthesized. Nitramino-functionalized N-(5-(5-amino-1,2,4-oxadiazol-3-yl)-3H-1,2,4-triazol-3-yl)nitramide (6) and N-(5-(5-(nitramino)-1,2,4-oxadiazol-3-yl)-3H-1,2,4-triazol-3-yl)nitramide (7) were also obtained, and two series of corresponding nitrogen-rich salts were prepared, leading to the creation of new energetic compounds. All derivatives were fully characterized, and five of them were further confirmed by X-ray diffraction. The theoretical calculations, energetic performance, safety, and the main decomposition gaseous products of 1,2,4-triazole-1,2,4-oxadiazole-derived energetic materials were studied. Compound 7 and its dihydroxylammonium salt (7 c) exhibited prominent detonation performance comparable to that of RDX while possessing satisfying thermal stabilities and mechanical sensitivities.

Dimethoxycarbonyl Groups Surrounding a Symmetric Diaminobistetrazole Ring: Exploring New Green Energetic Materials

A novel oxygen-containing dimethoxycarbonyl diaminobistetrazole (1) was synthesized via a facile strategy. The sodium salt (2) based on this ligand was prepared and these two compounds were fully characterized by using elemental analysis, IR and mass spectrometry and single-crystal X-ray diffraction. Their density, heats of formation, thermal stability and sensitivity, as well as the energetic properties from EXPLO5 code were investigated. These newly synthesized compounds possess high positive heats of formation and detonation heats. Compound 1 exhibits good detonation performance and acceptable stability, and might be a potential eco-friendly alternative of lead azide. The present study contributes to the development of tetrazole derivatives as new energetic materials.

Syntheses and Promising Properties of Dense Energetic 5,5'-Dinitramino-3,3'-azo-1,2,4-oxadiazole and Its Salts

A planar energetic molecule with high density, 5,5'-dinitramino-3,3'-azo-1,2,4-oxadiazole (4), was obtained by the nitration of 5,5'-diamino-3,3'-azo-1,2,4-oxadiazole using 100 % nitric acid. In addition, selected nitrogen-rich salts were prepared. Of them, the neutral compound 4 and its hydroxylammonium salt, 6, were further confirmed by single-crystal X-ray diffraction. Physicochemical and energetic properties including density, thermal stability, and sensitivity were investigated. The energetic performance from the calculated heats of formation and experimental densities indicates that many of them have potential applications as energetic materials.

Progress in Polyarsolyl Chemistry

The synthesis of heteroatom analogues of the cyclopentadienyl anion Cp^- is a fascinating and challenging field of research. The replacement of methine moieties by phosphorus is well investigated for the synthesis of mono-, tri- and pentaphospholyl ligands. On the other hand, arsenic derivatives are rare and 1,2,4-triarsolyl and tetraarsolyl salts are unknown. Herein, we report on the synthesis of Cs[E₃ C₂ (trip)₂ ] (1 a: E=P; 1 b: E=As; trip=2,4,6-triisopropylphenyl) and Cs[E₄ C(trip)] (2 a: E=P; 2 b: E=As). Compound 1 b represents the first 1,2,4-triarsolyl and 2 b the first tetraarsolyl anion. All salts are obtained in one-pot syntheses using E(SiMe₃ )₃ , 2,4,6-triisopropylbenzoyl chloride and CsF. The products 1 a⋅2 C₄ H₈ O₂ , 2 a⋅Et₂ O and 2 b⋅3 C₄ H₈ O₂ were characterized by X-ray structural analysis, which revealed planar heterocycles. Nucleus-independent chemical shifts (NICS) confirmed the aromaticity of these anions. Notably, compound 2 a⋅Et₂ O is only the second tetraphospholyl ligand which is structurally characterized.