Carbonyl Modifying Bridge Strategy: Constructing High-Energy and Low-Sensitivity Energetic Materials.

The bridged-ring strategy was a common approach to enhance the stability and number of modifiable sites for energetic compounds. However, changes in the bridging method can also lead to uncertainty in the energetic performance of the compound, and bridge replacement requires resynthesizing the entire compound. In this work, the carbonyl modifying bridge strategy was confirmed to be an effective method. With the perfection of the carbonyl group, compound bis(3,5-dinitro-1H-pyrazol-4-yl)methanone 4 exhibits high density (ρ = 1.91 g/cm3), excellent thermal stability (Td = 270 °C), good detonation performance (vD = 8579 m/s), and low sensitivity (IS > 40 J), serving as a potential insensitive explosive. Besides, amino functionalized product bis(1-amino-3,5-dinitro-1H-pyrazol-4-yl)methanone 7 significantly alleviated the problem of decreased thermal stability (from 192 °C of 1 to 243 °C of 7). Moreover, the derivative (including ammonium salt and hydroxylamine salt) of compound 4 demonstrates comprehensive performance superiority over that of HL-9, which further validates the efficacy of our strategy. Theoretical and experimental results confirm that introducing conjugation effects to modify the bridge can comprehensively enhance the performance of energetic compounds.