Computational study of energetic nitrogen-rich derivatives of 1,1'- and 5,5'-bridged ditetrazoles.

Density functional theory method was used to study the heats of formation (HOFs), electronic structure, energetic properties, and thermal stability for a series of bridged ditetrazole derivatives with different linkages and substituent groups. The results show that the -N3 group and azo bridge (-N=N-) play a very important role in increasing the HOF values of the ditetrazole derivatives. The effects of the substituents on the HOMO-LUMO gap are combined with those of the bridge groups. The calculated detonation velocities and detonation pressures indicate that the -NO2, -NF2, -N=N-, or -N(O)=N- group is an effective structural unit for enhancing the detonation performance for the derivatives. An analysis of the bond dissociation energies for several relatively weak bonds suggests that the N-N bond in the ring or outside the ring is the weakest one and the N-N cleavage is possible to happen in thermal decomposition. Overall, the -CH2-CH2- or -NH-NH- group is an effective bridge for enhancing the thermal stability of the bridged ditetrazoles. Because of their desirable detonation performance and thermal stability, five compounds may be considered as the potential candidates of high-energy density materials (HEDMs). These results provide basic information for the molecular design of novel HEDMs.