Preparation, crystal structure, thermal decomposition and explosive properties of K₂(tza)₂(H₂O) (tza = tetrazole-1-acetic acid

A new energetic compound based on the tetrazole-1-acetic acid (tza) and potassium(I) salt, K₂(tza)₂(H₂O), was synthesized and characterized by elemental analysis and FT-IR spectrum. Its crystal structure was determined by single-crystal X-ray diffraction analysis. The results show that the crystal belongs to the orthorhombic system, space group Pna21 with a = 1.11972(17) nm, b = 0.46647(7) nm, c = 2.5158(4) nm, V = 1.3140(3) nm³, K₂C₆H₈N ₈O₅, Mr = 350.40 g.mol-1, Dc = 1.771 g.cm-3, μ(MoKa) = 0.759 mm-1, F(000) = 712, Z = 4, R = 0.023 and wR = 0.0527 for 2961 observed reflections (I > 2σ(I)). The K(I) cation is six-coordinated with four O atoms from three carboxylate groups, one O atom from one H₂O molecule and one N atom from tetrazolyl ring, in which each tza is coordinated in a tridentate chelating bridging coordination mode. The thermal decomposition mechanism of the title complex was studied by DSC and TG-DTG techniques. Under nitrogen atmosphere at a heating rate of 10 K.min^-1, the thermal decomposition of the complex contains one main exothermic process between 191.7 and 243.8 °C in the DSC curve. Its combustion heat was mensurated by oxygen bomb calorimetry. The non-isothermal kinetics parameters were calculated by the Kissinger;s method and Ozawa-Doyle;s method, respectively. The sensitivity properties of K₂(tza)₂(H₂O) were also determined with standard methods, which was very sensitive to flame.