Tuning energy properties via N-NH2 strategy: Construction of two isomeric energetic compounds based on nitro-substituted pyrazoles

The N -site functionalization strategy of nitrogen-rich heterocycles has attracted considerable research attention due to its crucial role in achieving structural diversity and outstanding performance of high-energy compounds. However, research on isomerism-guided N -functionalized heterocycles is still limited thereby impeding a thorough understanding of their structure-property relationships. In this work, two energetic compounds, 3-azido-4,5-dinitropyrazole-1-amine ( 3-ADNP ) and 4-azido-3,5-dinitropyrazole-1-amine ( 4-ADNP ), with identical chemical structures were designed and synthesized based on the N -NH 2 synthesis strategy. The isomers 3-ADNP ( D v : 9306 m·s -1 ; P : 38.3 GPa) and 4-ADNP ( D v : 9375 m·s -1 ; P : 38.9 GPa) exhibit comparable and superior detonation performance compared to RDX. In addition, they exhibit consistency in density and sensitivity, but show significant differences in thermal stability. Specifically, 3-ADNP shows no melting point, whereas 4-ADNP has a melting point of 116.4°C. The decomposition temperatures are 138.4 °C for 3-ADNP and 156.7 °C for 4-ADNP . Crystal structure analysis and theoretical calculations were performed to elucidate the reasons behind the observed performance differences. These findings provide important theoretical insights for the design and application of amino-substituted nitro-pyrazole-based energetic materials. This work reports two positional isomeric compounds (3-ADNP and 4-ADNP) constructed via N -NH 2 strategy. While exhibiting comparable densities (3-ADNP: 1.878 g·cm -3 ; 4-ADNP: 1.879 g·cm -3 ) and remarkably similar detonation performances (for 3-ADNP, D V : 9306 m·s -1 , P : 38.3 GPa; for 4-ADNP, D V : 9375 m·s -1 , P : 38.9 GPa), their thermal stabilities show clear differences. • Two novel isomeric structures are constructed by introducing N -NH 2 . • 3-ADNP and 4-ADNP have higher density ( 3-ADNP : 1.878 g·cm -3 , 4-ADNP : 1.879 g·cm -3 ) and superior detonation performance ( 3-ADNP : V D = 9306 m·s -1 , P = 38.3 GPa; 4-ADNP : V D = 9375 m·s -1 , P = 38.9 GPa). In addition, 4-ADNP has a melting point ( T m = 116.4°C), while 3-ADNP has no melting point. • The synthetic route is short and the synthetic process is simple.