Very thermostable energetic materials based on a fused-triazole: 3,6-diamino-1H-[1,2,4]triazolo[4,3-b][1,2,4]triazole

3,6-Diamino-1H-[1,2,4]triazolo[4,3-b][1,2,4]triazole (1) and its energetic salts (2-9) were designed and synthesized based on a fused-triazole backbone with two C-amino groups as substituents. Their physicochemical and energetic properties were measured or calculated. Among them, compound 1 exhibits superior thermostability (T-d (onset): 261 degrees C), surpassing its analogues 3,7-diamino-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazole (DATT, 219 degrees C) and 3,6,7-triamino-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazole (TATOT, 245 degrees C). The differences in thermal stabilities were further investigated by determining the lowest bond dissociation energies (BDE) where a positive correlation between the stability of the molecules and the lowest BDE values is observed. The results show that 1 with the highest value for the lowest BDE has a superior thermostability in comparison to DATT and TATOT. The energetic salts (2-9) also exhibit remarkable thermal stabilities as well as low impact and friction sensitivities. The fused-triazole backbone 1H-[1,2,4]triazolo[4,3-b][1,2,4]triazole with two C-amino groups as substituents is shown to be a promising building block for construction of very thermally stable energetic materials.