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As a full nitrogen energetic anion, pentazolate (cyclo-N5ˉ) holds great promise in the fields of propellants and explosives. Nowadays, nonmetallic pentazolate salts have received extensive attention as excellent nitrogen-rich energetic materials for their high enthalpies of formation, good oxygen balance, and eco-friendly decomposition products. In this study, a 1,4,5-triaminotetrazolium-based pentazolate salt (TATe+N5ˉ, 8) with a nitrogen content of up to 90.30% was designed and synthesized. Its crystal structure indicates that a large number of hydrogen bonds form a hydrogen-bonded network, and the crystal has a mixed stacking pattern. TATe+N5ˉ, which has a relatively high density (1.64 ​g·cm−3), high heat of formation (861.9 ​kJ·mol−1), and excellent detonation performances (detonation velocity: 9487 ​m·s−1, detonation pressure: 32.5 ​GPa), provides new insights into the stability of ultrahigh-nitrogen compounds.

The exploration of energetic derivatives of 1,1-diamino-2,2-dinitroethylene (FOX-7) is a feasible strategy for attaining high-performance energetic materials. Of all the extant types of energetic derivatives, hydrazino-substituted FOX-7 derivatives have received the most extensive attention because of their excellent detonation performance. However, the applications of these derivatives are restricted by their relatively high mechanical sensitivities. In this study, the exploration of the reaction between 1,1-diamino-2-nitro-2-(1H-triazol-5-yl)ethene (Tri-FOX) and hydrazine monohydrate resulted in the development of an unexpected dihydrotetrazine bridged energetic compound: 3,6-bis((E)-hydrazono(1H-1,2,4-triazol-5-yl)methyl)-1,4-dihydro-1,2,4,5-tetrazine (BHDT). BHDT exhibits high onset decomposition temperature (Td ​= ​240 ​°C), low impact sensitivity (IS ​= ​30 ​J), and low friction sensitivity (FS ​= ​270 ​N). These features are more advantageous than those of H-FOX (Td ​= ​125 ​°C, IS ​= ​6 ​J) and HTz-FOX (Td ​= ​237 ​°C, IS ​= ​10 ​J, FS ​= ​240 ​N).

The synthesis of energetic compounds with high detonation performance and low sensitivity has always been the goal of the energetic material field. However, the synthetic chemistry of energetic compounds also plays a crucial role since it can provide new insights for designing new molecules and understanding reaction pathways. In this study, two unexpected compounds 2 and 3 were prepared from the reactions of 7-amino-8-nitrotetrazolo [1,5-c]pyrimidine (1) with acetone under an acidic condition and with different nitration reagents, respectively. Their structures were determined using 1H and 13C NMR spectroscopy, elemental analysis, and the single-crystal X-ray diffraction technology. Furthermore, the possible mechanisms for the transformation from 1 to 2 and 3 were studied.