pH-Dependent Formation of Two Dihydrazinyltetrazine–Azobistetrazolate Salts with Different Thermal Stabilities and Energetic Performance

Two new energetic salts were prepared through the combination of 3,6-dihydrazinyl-1,2,4,5-tetrazine dichloride ([H₂DHT]­Cl₂) and disodium 5,5′-azobis­(tetrazolate) pentahydrate (Na₂AZT·5H₂O) in different pH conditions. Under acidic conditions, the 1:1 salt [H₂DHT]­[AZT]·2H₂O (2·2H₂O) was isolated, while neutral pH gave access to the formation of the 2:1 salt ([HDHT]₂[AZT]·4H₂O; 3·4H₂O). Both compounds were characterized by IR and NMR spectroscopy, thermal analysis (thermogravimetric analysis and differential scanning calorimetry), as well as single crystal and powder X-ray diffraction. Based on experimental data, compound 2·2H₂O was found to be more thermally stable, with a decomposition temperature of T_dec = 107 °C, compared to compound 3·4H₂O (T_dec = 99 °C). Non-covalent interactions (hydrogen bonds and π–π interactions) were evaluated to better understand the structure–property relationships, revealing the effect of crystal packing on the overall energetic properties.