Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The
development of novel, environmentally friendly, and high-energy
oxidizers remains interesting and challenging for replacing halogen-containing
ammonium perchloride (AP). The trinitromethyl moiety
is one of the most promising substituents for designing high-energy
density oxidizers. In this study, a backbone isomerization strategy
was utilized to manipulate the properties of 10 nitro group-substituted
bipyrazoles containing the largest number of nitro groups among the
bis-azole backbones so far. Another advanced high-energy density oxidizer,
3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it
possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J
and FS = 215 N), thereby demonstrating a promising
perspective for practical applications.