Energetic compounds based on a new fused triazolo[4,5-d]pyridazine ring: Nitroimino lights up energetic performance

Abstract

The difference between nitroimino and nitroamino in compound 5. • A new triazolo[4,5–d]pyridazine fused ring was synthesized. • A different method was found to synthesize the pyridazine fused ring. • The nitroimino group has a low ESP and forms strong HB and π-π interactions. • The properties of compounds 7 and 8 are comparable to those of HMX. • The synthesis of 5 is cost effective and can be extended to gram-scale (2 g). A series of highly energetic materials with good detonation performance, high density and low impact sensitivity based on a new triazolo[4,5–d]pyridazine fused ring was synthesized and characterized. 4-Nitroamino-7-nitroimino-triazolo[4,5–d]pyridazine ( 5 ) was characterized by single crystal X-ray structure analysis, which shows that the proton of one nitroamino group was transferred to the pyridazine ring forming a nitroimino moiety. The electrostatic potential (ESP) of 5 shows the nitroimino group has the lowest negative value, while the nitroamino area has a high positive value. The analysis of NCI plots indicates strong intramolecular hydrogen bonds (HB) and π-π interactions which arise from the newly formed nitroimino group. This supports that the rearrangement of the nitroamino group to form the nitroimino moiety lowers the impact sensitivity. Compound 5 ·H 2 O exhibits face-to-face packing, which gives rise to a relatively high density of 1.87 g cm −3 and a low impact sensitivity of 18 J. Its hydrazinium and hydroxylammonium salts have high detonation velocities of 9351 m s −1 and 9307 m s −1 , respectively. Their impact and friction sensitivities (7 J, 120 N and 8 J, 160 N) are similar to HMX. This proclivity for rearrangement by a nitroamino group provides new insight into the design of next generation high energy density materials.