Synthesis of 5/6/5-fused tricyclic-cation-based cyclo-N₅⁻ salt with high density and heat of formation

Pentazolate anion (cyclo-N₅⁻) containing compounds have attracted wide interest in recent years. In this paper, to explore the fantastic chemistry of cyclo-N₅⁻, a novel polyamino 5/6/5-fused tricyclic-cation-based cyclo-N₅⁻ salt, 2,3,5,6-tetraamino-9-imino-5,9-dihydro-3H-bis([1,2,4]triazolo)[1,5-a:5′,1′-d][1,3,5]triazin-8-ium pentazol-1-ide (TABTT ⁺N₅⁻) was designed and synthesized. The chemical structures were determined by FTIR spectroscopy and single-crystal X-ray diffraction. TABTT ⁺N₅⁻ exhibited a planar layer structure and a regular face-to-face layer stacking due to the strong hydrogen-bonding networks formed between polyamino 5/6/5-fused tricyclic and cyclo-N₅⁻. TABTT ⁺N₅⁻ exhibited acceptable thermal stability (T_d: 106 ​°C), high density (1.638 ​g ​cm⁻³), high heat of formation (1078.122 ​kJ ​mol⁻¹), and a good balance between energy and safety with high detonation performances (v_D ​= ​8756 ​m ​s⁻¹, p ​= ​26.03 ​GPa) and a low sensitivity (IS ​= ​25 ​J, FS ​= ​360 ​N), demonstrating the potential of nitrogen-rich cyclo-N₅⁻ salts as high energy materials.