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In this work, a fused-ring [1,2,5]oxadiazolo[3,4- b ]pyridine 1-oxide framework with multiple modifiable sites was utilized to develop novel energetic materials with multiple hydrogen bonds. The prepared materials were characterized, and their energetic properties were extensively investigated. Among those studied, compound 3 exhibited high densities of 1.925 g cm -3 at 295 K and 1.964 g cm -3 at 170 K, with high detonation performances ( D v : 8793 m s -1 and P : 32.8 GPa), low sensitivities ( IS : 20 J, FS : 288 N), and good thermal stability ( T d : 223 °C). N -Oxide compound 4 had higher-energy explosive ( D v : 8854 m s -1 and P : 34.4 GPa) and low sensitivities ( IS : 15 J and FS : 240 N). Compound 7 with a high enthalpy group (tetrazole) was determined as a high-energy explosive ( D v : 8851 m s -1 , P : 32.4 GPa). Notably, the detonation properties of compounds 3 , 4 , and 7 were similar to high-energy explosive RDX ( D v : 8801 m s -1 and P : 33.6 GPa). The results indicated that compounds 3 and 4 were potential low-sensitivity high-energy materials.

The development of hypergolic materials has aroused great interest due to their important applications in aerospace technology. In this work, six new energetic complexes were prepared and comprehensively characterized. All energetic complexes had isostructural characteristics, which made them ideal candidates for studying their structure-performance relationships. These energetic complexes had good thermal stabilities and excellent specific impulses. The vacuum-specific impulses were in the range 264.0-271.9 s, which was greater than most reported solid hypergolic materials. Moreover, the hypergolic performance of these compounds was examined by using 100% HNO 3 as the oxidizer, and their catalytic performance in the hypergolic reaction of typical energetic ionic liquids and 90% H 2 O 2 was comprehensively studied. All compounds displayed excellent hypergolic performance with the shortest ignition delay time of 4 ms. The examined copper-containing energetic complexes displayed excellent catalytic activities for the hypergolic reaction between energetic ionic liquids and 90% H 2 O 2 . The shortest ignition delay time of the examined hypergolic reactions was 31 ms. The suitable physicochemical properties, excellent energetic properties, and high catalytic activity of the hypergolic reactions have demonstrated the great potential of these energetic complexes as promoters for the development of green hypergolic bipropellants.

A series of fused-ring energetic materials, i.e., 3,6-dinitro-1,4-di(1 H -tetrazol-5-yl)-pyrazolo[4,3- c ]pyrazole ( DNTPP , compound 2 ) and its ionic derivatives (compounds 3 - 8 ), were designed and synthesized in this study. The molecular structures of compounds 2 , 3 , 6 , 7·2H 2 O , and 8 were confirmed using single-crystal X-ray diffraction. Their physicochemical and energetic properties, such as density, thermal stability, heat of formation, sensitivity, and detonation properties (e.g., detonation velocity and detonation pressure), were also evaluated. The results indicate that DNTPP and most of its ionic derivatives are extremely thermally stable and insensitive toward mechanical stimuli. In particular, the thermal decomposition temperature of compound 3 is up to 329 °C, while compounds 7 and 8 are very insensitive (impact sensitivity: >20 J; friction sensitivity: >360 N). Compounds 2 , 3 , and 6 possess good comprehensive properties, including excellent thermal stability, remarkable low sensitivities, and favorable detonation performance. These features show that DNTPP and its ionic derivatives have considerable promise as thermally stable and insensitive energetic materials.