Molecular design of long intra‐annular nitrogen chains: 3H‐tetrazolo[1,5‐d]tetrazole‐based high‐energy‐density materials

Abstract

AbstractEnergetic compounds containing long nitrogen chain, have been a research hotspot. Fused heterocycles are stable due to their aromatic systems. Compounds obtained by combining long nitrogen chain and fused ring can not only retain good energetic property, but also ensure better stability. In this work, eight fused heterocycle‐based energetic compounds, 3H‐tetrazolo[1,5‐d]tetrazole (1) and its derivatives (2–8), were designed, containing a nitrogen chain with seven nitrogen atoms. The HOF, thermal stability, and energetic properties of these compounds were studied using the DFT method. The results show that the introduction of –NO2, –N3, –NF2, –ONO2, and –NHNO2 groups greatly increased the density, HOF, detonation velocity, and detonation pressure. The densities of 3, 5, 7, and 8 fall within the range designated for high‐energy‐density materials. The calculated detonation velocities of the compounds 3 and 8 are as high as 9.86 and 9.78 km s−1, which are superior to that of CL‐20. Kinetic study of the thermal decomposition mechanism indicates that the N–R bonds may not be the weakest bonds in these compounds. The tetrazole ring opening of the heterocycle‐based energetic compounds, followed by N2 elimination, is predicted to be the primary decomposition channel, regardless of whether substituent groups are present.