Energetic compounds based on a new fused Bis[1,2,4]Triazolo[1,5-b;5′,1′-f]-1,2,4,5-Tetrazine

Abstract

A method for the thermal cyclization of tetrazol-5-ylamino-1,2,4,5-tetrazine has been developed, leading to the formation of a new heterocyclic system based on 1,2,4-triazole and 1,2,4,5-tetrazine, a fused tricyclic compound, from which a number of other tricyclic derivatives containing nitramine, nitro, and keto groups have been obtained. Based on experimental studies and quantum-chemical calculations enthalpies of formation of the new fused energetic materials in the solid state have been found. The enthalpy of formation of the new fused tricyclic compound bis[1,2,4]triazolo[1,5-b:5′,1′-f][1,2,4,5]tetrazine-2,7-diamine, DATC, (3505 kJ kg−1) exceeds the enthalpies of formation of diaminotetrazine (2652 kJ kg−1) and 5-aminotetrazole (2442 kJ kg−1), which makes the resulting framework one of the most energetic heterocyclic compounds. In addition, DATC and its derivatives turned out to be low-sensitive and thermally stable explosives, the stability of which is comparable to the known thermostable explosives TATB and TACOT, but with higher detonation characteristics. N,N'-(bis([1,2,4]triazolo)[1,5-b:5′,1′-f][1,2,4,5]tetrazine-2,7-diyl)dinitramide was used as a starting acid to obtain salts with organic bases. The hydroxylamine salt, H2DNATC, turned out to be the most powerful compound, comparable in detonation characteristics (D = 9020 m s−1) to HMX, but having a higher burning rate (54 mm s−1 at 10 MPa), and therefore it may be of interest as a high-energy fast-burning filler for composite propellants and gunpowder. Thermocouple-aided studies in the H2DNATC combustion wave made it possible to estimate the enthalpy of dissociation of the salt into gaseous components and to establish the combustion mechanism. The demonstrated thermal cyclization method for the preparation of fused tricyclic tetrazines provides new insights into the design of HEDMs, which may be useful for practical applications.