A simple and efficient strategy for constructing nitrogen-rich isomeric salts and cocrystal through pKa calculation

Nitrogen-rich energetic salts and cocrystal have attracted considerable attention in recent years. To assess the formation of cocrystal or salt, acid dissociation constant (pKa) values of the isomeric co-formers were calculated in this work and significant differences were observed. Two salts and one cocrystal based on H2BT (1H, 1′H-5,5′-bitetrazole), DATr (4,5-diamino-4H-1,2,4-triazole), 1MAT (1-methyl-5-aminotetrazole) and 2MAT (2-methyl-5-aminotetrazole) were synthesized, which corresponding to the different pKa values of three isomeric coformers. Single crystal structure analysis reveals that all compounds are formed by layered stacking structure with π-π stacking and rich hydrogen bonds, resulting in the insensitivity towards impact and friction (impact sensitivity > 40 J, friction sensitivity > 360 N). To the best of our knowledge, it is the first time to report the cocrystal of H2BT. The study results provide a utility method to seek for suitable coformers and design energetic cocrystal through the calculation of pKa.