[5,6,5]-Tricyclic Energetic Compounds with Piperazine, Triazole, and 1,2,5-Oxadiazole Rings in Framework

In this work, a series of [5,6,5]-tricyclic fused ring energetic compounds 1–9 were synthesized utilizing triazole, furazan, and piperazine as basic units. A thorough analysis of the newly synthesized compounds was carried out, and the structures of compounds 2, 6, and 7 were further validated using single-crystal X-ray diffraction. The physicochemical properties and energetic characteristics of newly synthesized compounds 1–9 were determined by experimental and theoretical methods. Compared with the previously reported tricyclic fused ring compounds, the newly synthesized fused energetic compounds exhibit better comprehensive characteristics including moderate detonation performance and good stability. The hydrazine salt 4 (T_d = 211 °C, D_v = 8702 m s^–1) is comparable to 1,3,5-trinitroperhydro-1,3,5-triazine (RDX: T_d = 204 °C, D_v = 8975 m s^–1) in terms of the calculated detonation velocity and thermostability. Besides, hydrazine salt 4 (IS = 30 J, FS = 288 N) is more stable than RDX (IS = 7.4 J, FS = 120 N) in mechanical sensitivity. Moreover, the carbonyl compound [1,2,5]oxadiazolo[3,4-e][1,2,4]triazolo[4,3-a]pyrazine-5,8(4H,7H)-dione (6, T_d = 304 °C) exhibits similar thermal stability to that of 2-bis(2,4,6-trinitrophenyl) ethene (HNS: T_d = 318 °C) and has a higher calculated detonation velocity (6: D_v = 7984 m s^–1, HNS: D_v = 7647 m s^–1). Based on the properties mentioned above, carbonyl compound 6 is a promising candidate for a new heat-resistant explosive.