Synthesis, crystal structure, thermal decomposition, and explosive properties of [Bi(tza)₃]_n (tza = tetrazole acetic acid)

A coordination compound based on tetrazole acetic acid (Htza) and bismuth(III), [Bi(tza)₃]_n, was synthesized and characterized by single crystal X-ray diffraction analysis, elemental analysis, FT-IR, and ¹H NMR spectroscopy. The crystallographic data show that the crystal belongs to monoclinic, P2_1/n space group, a = 0.91968(19) nm, b = 0.94869(19) nm, c = 1.7824(4) nm, β= 101.488(3)°, and Z = 4. The central bismuth(III) is nine-coordinate by three nitrogens from three tetrazole rings and six oxygens of the carboxylate of another three tza ^- ions, with each tza^- tridentate, chelating, bridging coordination. The coordination bonds and the intramolecular hydrogen bonds make the complex pack into a layered structure in polymer form. The thermal decomposition mechanism of the title complex was investigated by DSC and TG-DTG techniques. Under nitrogen at a heating rate of 10°C min^-1, thermal decomposition of the complex contains two intense exothermic processes between 217.4°C and 530.3°C in the DSC curve; the final decomposed residue at 570°C was Bi₂O₃. Sensitivity tests showed that [Bi(tza)₃]_n was sensitive to impact and flame stimulus.