Linear furoxan assemblies incorporating nitrobifuroxan scaffold: En route to new high-performance energetic materials

Energetic materials science is undergoing a global renaissance aiming to reach an ideal combination between reliable synthetic strategies, high performance and acceptable molecular stabilities. In this work, design and synthesis of novel energetic non-hydrogen furoxan assemblies has been successfully realized. Fine tunability of molecular composition in a series of furoxan-based materials was achieved by the variation of a number of heterocyclic rings and employing N-oxide regioisomerism strategy. Using this approach, advanced energetic regioisomeric azo-bridged bifuroxan assemblies 6 and 7 as well as 3,4′-dinitro-3′,4-bifuroxan 8 with the excellent overall performance were synthesized. Calculations of Hirshfeld surfaces and molecular electrostatic potentials were conducted to better understand the relationship between the molecular structure and mechanical sensitivity in the synthesized series of energetic materials. It was found, that the supramolecular aggregation of 3,4′-dinitro-3′,4-bifuroxan 8 molecules in crystal is more anisotropic that is commonly believed to be more favorable pattern for the low sensitive substances. All target materials have high densities (1.88–1.95 g cm−3), acceptable thermal stabilities (up to 165 °C), high enthalpies of formation (1.6–2.4 kJ g−1) and positive oxygen balance to CO (up to + 25%). As a result, these compounds exhibit high detonation velocities (9.1–9.5 km s−1), excellent heats of explosion (6.6–7.2 kJ g−1) and combustion performance (Isp = 269–281 s). Therefore, these furoxan-based advanced energetic materials unveil new opportunities in search of next-generation functional organic materials for various applications.