Synthesis, spectral characterization and study of thermal behavior kinetics by thermogravimetric analysis of metal complexes derived from salicylaldehyde and alkylamine

Abstract

Cobalt(III)- and copper(II)-Schiff base complexes have been prepared by reaction of the bidentate Schiff base ligand (HL: 2-(4-methoxyphenyl)-1-iminosalicylidenethane) with cobalt(II) and copper(II) chlorides. Structures of the synthesized complexes have been characterized by various physicochemical techniques, such as IR and UV–Vis spectroscopy, mass spectrometry, thermogravimetric analysis (TG/DTG), and by elemental analysis. Additionally, the redox behavior of the cobalt(III) and copper(II) complexes has been examined by cyclic voltammetry at a glassy carbon electrode in DMF solutions. Thermogravimetric analysis has been employed to evaluate the thermal stability of the prepared complexes CoIII(L)3·1/2H2O, CuII(L)2, in addition to the previously synthesized HL and NiII(L)2. Furthermore, activation energies of the thermal decomposition were calculated using Kissinger, Ozawa and Coats-Redfern methods. The calculated activation energies were also useful to evaluate kinetic and thermodynamic parameters of the ligand and the corresponding metal complexes including ΔS, ΔH and ΔG. Calculated activation energies follow the order: Ea(NiII(L)2) > Ea(CuII(L)2) > Ea(CoIII(L)3·1/2H2O).