Unlocking the effect of monocyclic and fused backbones on energy and stability of fully nitrated compounds

Despite their attractive energetic performances, fully nitrated monocyclic and fused compounds exhibit varying densities and stabilities. In this context, to reveal the effect of monocyclic and fused backbones on density and stability, two fully nitrated compounds, 1-trinitromethyl-3,5-dinitro-1,2,4-triazole (4) and 3,6-dinitro-7-(trinitromethyl)-[1,2,4]triazolo[4,3-b][1,2,4]trizole (8, BITE-203), with the same groups but different backbones were designed and synthesized via a simple three-step procedure. Experimental results, X-ray diffraction analysis, and quantum calculations indicated that fused BITE-203 exhibits a higher density (1.968 g cm⁻³ at 296 K) than monocyclic 4 (1.958 g cm⁻³ at 296 K), which is caused by the stronger intermolecular p-π interactions and closer molecular stacking of BITE-203. In addition, BITE-203 also shows higher stability (168 °C) than 4 (143 °C) owing to its weaker intramolecular repulsion and stronger aromaticity, thus revealing the positive effect of the fused backbone on density and stability enhancement. In addition, BITE-203 is the only trinitromethyl compound that simultaneously achieves a density greater than 1.950 g cm⁻³ and a thermal decomposition temperature exceeding 165 °C, in addition to a considerable detonation velocity of 9199 m s⁻¹ and high oxygen balance of + 27.6%, demonstrating its excellent potential as a promising high-energy–density material.