Simple Preparation of Heat-Resistant Energetic Materials Based on [5,6,5] Tricyclic Fused-Ring Skeletons and Evaluation of Their Energetic Performance

In recent years, there has been great interest in the development of high-performance heat-resistant energetic materials owing to their widespread applications in civilian and national defense technologies. Herein, four heat-resistant energetic materials, i.e., 9H-imidazo[4,5-d][1,2,4]triazolo[4,3-b]pyridazin-6-amine (1), 9H-imidazo[4,5-d][1,2,4]triazolo[4,3-b]pyridazin-6-amine perchlorate (2), 9H-imidazo[4,5-d][1,2,4]triazolo[4,3-b]pyridazine-6,8-diamine (3), and 9H-imidazo[4,5-d][1,2,4]triazolo[4,3-b]pyridazine-6,8-diamine perchlorate (4), were prepared and comprehensively studied. Compounds 1-4 having unique [5,6,5] tricyclic fused-ring molecular structures were prepared via a simple one-step reaction. All of the compounds exhibited excellent thermal stabilities with decomposition temperatures exceeding 309 °C. The highest decomposition temperature (421 °C) was observed for compound 3. The excellent thermal stability of these compounds was found to be strongly related to their tricyclic fused-ring molecular skeleton structures. In addition, compounds 2 and 4 exhibited high density with the values of 1.882 and 1.93 g·cm^-3, respectively, which were comparable to the highly energetic material, octogen (HMX, 1.91 g·cm^-3). The calculated detonation velocities of those compounds were in the range of 6996-8329 m·s^-1. The highest value observed for compound 4 was 8329 m·s^-1, and it was higher than that of the heat-resistant material, 1,3,5-triamino-2,4,6-trinitrobenzene (TATB, 8176 m·s^-1). Notably, all of the compounds displayed great mechanical sensitivities, with the impact sensitivities being higher than 20 J. The simple preparation methods and comprehensive performance make these materials have great potential as heat-resistant energetic materials.