Synthesis,Characterization And Properties Of 1,2,4,5-tetrazine-one Compounds

Energetic materials use elements like C,N,H,and O as the framework.During the reaction,they release heat and gas violently so as to do work to the external environment.Nowadays,the development of energetic materials is gradually diversified,considering both energy characteristic,safety and stability.In this paper,we take 1,2,4,5-tetrazine energetic compounds as the main research subjects to synthesize a new type of insensitive high-energy materials with better thermal stability.The study compares the thermal stability and energy characteristics of tetrazine with symmetric and asymmetric structures,and provides a foundation for future research directions.3,6-bis?3,5-dimethylpyrazol-1-yl?-S-terazine?BT?was synthesized by using synthesis route of tetrazine ring-forming reaction.Using BT as the intermediate,6-nitroguanidino-1,2,4,5-tetrazin-3-one Na salt?Na HNGTz O?was synthesized,thereafter,Na HNGTz O reacts with Mn?NO₃?₂,Zn?NO₃?₂·6H₂O,Sr?NO₃?₂·6H₂O,Ba Cl₂·6H₂O to obtain[Mn?HNGTz O?₂?H₂O?₄]·H₂O,[Zn?HNGTz O?₂?H₂O?₄]·H₂O,[Sr?NGTz O??H₂O?₇]and[Ba?NGTz O??H₂O?₅]·1/2H₂O.Acidification of Na HNGTz O yields 6-nitroguanidino-1,2,4,5-tetrazin-3-one?H₂NGTz O?,meanwhile,using Na HNGTz O and N₂H₄·H₂O as raw materials,6-aminoguanidino-1,2,4,5-tetrazin-3-one?AGTz O?was prepared.By slow evaporation method,the single crystals of[Mn?HNGTz O?₂?H₂O?₄]·H₂O,[Zn?HNGTz O?₂?H₂O?₄]·H₂O,[Sr?NGTz O??H₂O?₇],[Ba?NGTz O??H₂O?₅]·1/2H₂O and?AGTz O?were cultivated.The crystal structure of the salt of NGTz O and AGTz O were determined and analyzed by X-ray single crystal diffractometer:[Mn?HNGTz O?₂?H₂O?₄]·H₂O:C₆H₁₆N₁₆O₁₁Mn,monoclinic,P_21/C;[Zn?HNGTz O?₂?H₂O?₄]·H₂O:C₆H₁₆N₁₆O₁₁Zn,monoclinic,P_21/C;[Sr?NGTz O??H₂O?₇]:C₃H₁₆N₈O₁₀Sr,triclinic,P_-1;[Ba?NGTz O??H₂O?₅]·1/2H₂O:C₃H₁₃N₈O_17/2Ba,triclinic,P_-1;AGTz O:C₃H₆N₈O·H₂O,orthorhombic,Pb_ca.The thermal decomposition behavior of these as-prepared unsymmetrical tetrazin-one compounds were studied by the differential scanning calorimetry?DSC?and thermogravimetry?TG?under non-isothermal conditions.Using Kissinger,Ozawa and integral method studied the kinetic parameters of the salt of NGTz O and AGTz O,including the apparent activation energy,the pre-exponential and the thermal decomposition mechanism.The main thermal decomposition process were evaluated by the entropy of activation??S^??,enthalpy of activation??H^??and free energy of activation??G^??.The explosion velocity and pressure of AGTz O were estimated by the nitrogen equivalent formula.H₂NGTz O is purely crystallized in methanol,and no solvent molecules are found by DSC and elemental analysis.Due to the high nitrogen and oxygen content,heat is released quickly.[Mn?HNGTz O?₂?H₂O?₄]·H₂O and[Zn?HNGTz O?₂?H₂O?₄]·H₂O as a transition metal salt of the same period,so their crystal structures are similar,their initial decomposition temperature is lower than that of H₂NGTz O,and the heat release rate is slow relatively.[Sr?NGTz O??H₂O?₇]and[Ba?NGTz O??H₂O?₅]·1/2H₂O are alkaline earth metal salts of the same main group,so their crystal structures are similar,these initial decomposition temperature is lower than[Mn?HNGTz O?₂?H₂O?₄]·H₂O and[Zn?HNGTz O?₂?H₂O?₄]·H₂O,and the heat release rate is slow relatively with no obvious exothermic peak.The above conclusions indicate that the thermal decomposition rate of metal salts is slower than that of organic ligands.Experiments show that the coordination of metals can reduce the initial decomposition temperature of compounds and prolong the exothermic process.The oxygen balance value of AGTz O is lower than H₂NGTz O,the initial decomposition temperature is higher than H₂NGTz O,both of which release heat rapidly.