Molecular Design of Long Intra-annular Nitrogen
Chains:3H-tetrazolo[1,5-d]tetrazole-Based High-Energy-Density
Materials
Abstract
Energetic compounds containing long nitrogen chain, have been a research
hotspot. Fused heterocycles are stable due to their aromatic systems.
The compound obtained by combining long nitrogen chain and fused ring
can not only retain good energetic property, but also ensure better
stability. This work designed eight fused heterocycle-based energetic
compounds, 3H-tetrazolo[1,5-d]tetrazole (1) and its derivatives
(2-8), containing a nitrogen chain with seven nitrogen atoms. The HOF,
thermal stability, and energetic properties of these compounds were
studied by using the DFT method. The results show that the introduction
of -NO2, -N3, -NF2, -ONO2, -NHNO2 groups increased the density, HOF,
detonation velocity, and detonation pressure greatly. The densities of
3, 5, 7, and 8 fall within the range designated for high-energy-density
materials. The calculated detonation velocity of the compounds 3 and 8
are up to 9.86 km s-1 and 9.78 km s-1, which are superior to that of
CL-20. The kinetic study of the thermal decomposition mechanism
indicates that the N-R bonds maybe not the weakest bonds of these
compounds. The tetrazole ring opening of the heterocycle-based energetic
compounds, followed by N2 elimination is predicted to be the primary
decomposition channel, whether or not they have substituent groups.