Quantum chemistry modeling of the unimolecular decomposition mechanism and substituent effects of pyrazolo-tetrazine: A case study of BITE-101

Abstract

4-amino-7,8-dinitropyrazolo-[5,1-d][1,2,3,5]-tetrazine 2-oxide (BITE-101) outperforms the benchmark explosive HMX in all aspects, showing application prospects as a new generation of high energy density material. To obtain the thermal decomposition mechanism and key intermediates of BITE-101, the initial decay pathways were studied by using the M062X method for optimization and DLPNO-CCSD(T)/cc-pVTZ methods for energies. The energy barrier results showed that the nitro-nitrite isomerization was the lowest, indicating that this path was the most advantageous in the reaction of BITE-101. In addition, the H transfer reaction has a promoting effect on the ring-opening reaction. Additionally, the influence of functional group position on the initial decomposition mechanism of energetic materials is also discussed. The results show that the most likely first decay paths are all caused by the functional groups on the tetrazine ring, and the position of the amino group had a great influence on the ring-opening reaction. These reactions can be clearly seen from the changes in ELF and Mayer bond order. These results will certainly deepen our understanding of the decay mechanism of pyrazolo-tetrazine.