Thermal Behaviour of Metal Complexes of 6-(2-Pyridylazo)-3-acetamidophenol

Abstract

The present work aims chiefly to study the thermal behaviour of complex compounds with general formula: [M(HL)⋅xH₂O](A)⋅yH₂O (where HL=C₁₃H₁₁N₄O₂=6-(2-pyridylazo)-3-acetamidophenol (PAAP), M=Cu(II), Zn(II), Cd(II) and Fe(III) x=1, 3; y=2, 5) while A=CH₃COO⁻ (Ac), Cl₂. The second formula is [M(H₂L)⋅xH₂O]Cl₂⋅yH₂O, (where H ₂ L=C₁₃H₁₂N₄O₂ (PAAP), M=Ni(II), Co(II) x=3; y=4, 6). The compounds were identified by elemental analysis, FT-IR spectra and TG/DTG,DTA methods. It was found that during the thermal decomposition of complex compounds water molecules of crystallization are released in the first step. In the next step the pyrolysis of organic ligand takes place. Metal oxide remained as a solid product of the thermal decomposition. Mass spectroscopy has been used for the determination of the thermal decomposition on the intermediate products. It was found that the thermal stability of the studied compounds increases as the ionic radii decreases. The activation energy E, the entropy change ΔS ^*, the enthalpy ΔH ^* change and Gibbs free energy change ΔG ^* were calculated from TG curve.