[1,2,4]Triazolo[4,3-b]pyridazine as a building block towards low-sensitivity high-energy materials

• Two fused [1,2,4]triazolo[4,3-b]pyridazine energetic compounds are presented. • Both compounds possess low sensitivities, high energy and good thermostability. • The relationships between structure and properties are analyzed. In this work, bicyclic fused [1,2,4]triazolo[4,3-b]pyridazine was used to construct new low-sensitivity high-energy materials. Two exemplary compounds, 6,7-diamino-3,8-dinitro- [1,2,4]triazolo[4,3-b]pyridazine ( 1 ) and 7-amino-6-azido-3,8-dinitro-[1,2,4]triazolo[4,3-b]pyridazine ( 2 ), were synthesized and characterized. The properties of the energetic materials, including their detonation velocities ( D v : 8994 m·s −1 for 1 , 8819 m·s −1 for 2 ) and detonation pressures ( P : 34.1 GPa for 1 , 32.4 GPa for 2 ) were evaluated based on their densities ( ρ : 1.93 g·cm −3 for 1 , 1.84 g·cm −3 for 2 ) and heats of formation (Δ H f : 348 kJ·mol −1 for 1 , 684 kJ·mol −1 for 2 ). Their impact and friction sensitivities were measured to be 20 J and > 360 N for 1 and 18 J and 360 N for 2 . The onset decomposition temperatures of 1 and 2 were 234 °C and 217 °C, respectively; therefore, both compounds were highly energetic materials with low sensitivities and good thermostability.