Three new compounds based on 4,4′-azo-1,2,4-triazol-5-one: Synthesis, crystal structure and thermal properties

A series of guanidine salts of 4,4′-azo-1,2,4-triazol-5-one with guanidine( 1 ), aminoguanidine( 2 ), diaminoguanidine( 3 ) and triaminoguanidine( 4 ) was prepared. Compounds 2―4 were characterized by infrared(IR) spectroscopy, elemental analysis and single-crystal X-ray diffraction. Thermal decomposition processes of compounds 1 ― 4 were investigated by differential scanning calorimetry(DSC), and all the compounds showed good thermal stability up to 190 °C. Moreover, these four guanidine salts are more unstable with the increasing number of amino groups. Thermal stability parameters( T e, 0 and T b ) and thermodynamic functions(Δ S ≠ , Δ H ≠ and Δ G ≠ ) for compounds 1 ― 4 were calculated. The constant-volume combustion heats(Δ c U ) for compounds 2 ― 4 were determined and tended to increase with the increase of the number of amino groups. The calculated standard molar enthalpy of formation(Δ f H m 0 ) of compounds 2 ― 4 are–541.04,–178.67 and–83.08 kJ/mol, respectively. The impact sensitivities results indicate these four energetic salts are less sensitive than 1,3,5-trinitrotriazacyccohexane(RDX) and 1,3,5,7-tetranitrotetraqza-cyclo-octane(HMX).