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), C14H14N8O, 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 P21/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 (TSADT), critical temperature of thermal explosion (Tb), 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.