Direct C–C linkage coupled with salt formation: a dual strategy for high-performance tetrazole-based energetic materials

Nitrogen-rich energetic materials have attracted significant attention due to their remarkable enthalpy of formation and superior detonation performance. However, the inherent high mechanical sensitivity continues to pose significant applications limitations. In this work, a novel structural design featuring direct C-C linkages between central tetrazole rings was developed, replacing conventional indirect connections through NN bridges, thereby significantly enhancing thermal and mechanical stability. Besides, the salt formation strategy has also been demonstrated as an effective approach for sensitivity regulation. Through the combined implementation of direct C-C linkage and salt formation strategies, a series of tetrazole-based energetic materials, including neutral compounds H2TT and H2QT, as well as their energetic salts (K2TT, KHTT, NaKQT and 1-6) were successfully synthesized. Notably, the neutral compound H2QT exhibits an exceptionally high enthalpy of formation (ΔfHm = 1560.93 kJ mol-1/5.69 kJ g-1). Among the target compounds, hydrazine salt 4 has the most balanced properties with nitrogen content reaching 82.82%, enthalpy of formation of 1589.97 kJ mol-1/4.70 kJ g-1, detonation velocity of 9146 m s-1, decomposition temperature of 242 °C, impact sensitivity of 15 J and friction sensitivity of 240 N. This work successfully establishes the synthetic methodology for expanding from tritetrazole to tetratetrazole systems, thereby providing a fundamental strategy for the future development of extended-chain tetrazole-based compounds.