Structural, thermal kinetics and thermodynamics study of new mixed ligand zinc complexes

Abstract

Two new zinc(II)-2-chlorophenylacetate complexes, {[Zn(2-Cl-C6H4CH2COO)2(Phen)](2-Cl-C6H4CH2COOH)2, 1 and [Zn(2-Cl-C6H4CH2COO)2(bipy)](2-Cl-C6H4CH2COOH)2, 2} with nitrogen donor ligands, 1,10-phenanthroline (phen) and 2,2′-bipyridine (bipy), were synthesized and characterized by IR spectroscopy and single crystal diffraction. Distorted octahedral geometry was confirmed in both complexes. The compounds were studied for the thermal stabilities using TG and DTA methods at different heating rates (283, 288 and 293 K min−1). It was found that both the complexes show the same trend in stabilities and thermally degrade in two stages. The apparent activation energies for each step of specific conversions were determined using the Doyle–Ozawa calculation method according to ICTAC recommendations. The calculated average activation energies for 1 were found to be 17.52/10.19 J mol−1 for the first and second stages of degradation, respectively. Similarly, for 2 corresponding values for the two-stage degradation were found to be 12.45 and 3.485 J mol−1. Determining the enthalpy value of the activation revealed an exergonic nature of the thermal degradation.