Molecular design of 1,2,4,5-tetrazine-based high-energy density materials.

The heats of formation (HOFs) for a series of 1,2,4,5-tetrazine derivatives were calculated by using density functional theory (DFT), Hartree Fork (HF), and Møller-Plesset (MP2) as well as semiempirical methods. The effects of different basis bets on HOFs were also considered. Our results show that the -CN or -N3 group plays a very important role in increasing the HOF values of the 1,2,4,5-tetrazine derivatives. An analysis of the bond dissociation energies for the weakest bonds indicates that substitutions of the -N3, -NH2, -CN, -OH, or -Cl group are favorable for enhancing the thermal stability of 1,2,4,5-tetrazine, but the -NHNH2, -NHNO2, -NO2, -NF2, or -COOH group produces opposite effects. The calculated detonation velocities and pressures indicate that the -NF2 or -NO2 group is very helpful for enhancing the detonation performance for the derivatives, but the case is quite the contrary for the -CN, -NH2, or -OH group. Considered the detonation performance and thermal stability, three derivatives may be regarded as potential candidates of high-energy density materials (HEDMs).