Synthesis, crystal structure and thermal properties of an unsymmetrical 1,2,4,5-tetrazine energetic derivative.

A new unsymmetrical s-tetrazine derivative, namely 4-({2-[6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazin-3-yl]hydrazin-1-ylidene}methyl)phenol (DPHM), CHNO, was synthesized based on 3-(3,5-dimethylpyrazol-1-yl)-6-hydrazinyl-s-tetrazine (DPHT). The structure was characterized by elemental analysis and single-crystal X-ray diffraction. Crystal structure determination shows that DPHM crystallizes in the monoclinic P2/c space group with high coplanarity and a zigzag layered structure. In addition, its thermal behaviour was investigated by DSC and TG-DTG methods. The thermal safety of DPHM was evaluated by self-accelerating decomposition temperature (T), critical temperature of thermal explosion (T), entropy of activation (ΔS), enthalpy of activation (ΔH) and free energy of activation (ΔG). Meanwhile, the kinetic parameters and specific heat capacity of DPHM were also determined. The results show that DPHM has better stability and detonation properties than 3-(2-benzylidenehydrazin-1-yl)-6-(3,5-dimethylpyrazol-1-yl)-s-tetrazine (DAHBTz), due to the introduction of a hydroxy group, which increases the number of hydrogen-bond interactions and improves the stability and density of DPHM. This study demonstrates that the performance of an explosive can be optimized through structural modification.