Abstract

K. A. Abu-Melha^1*, A. A. El-Bindary²

DOI : http://dx.doi.org/10.13005/ojc/310418

A series of 3-phenylazo-2-thioxo-4-thiazolidinone derivatives (H₂L₁ and H₂L₂) have been prepared and characterized by elemental analysis. The optimized bond lengths, bond angles and the calculated quantum chemical parameters for the ligands (H₂L₁ and H₂L₂) were investigated. Dissociation constants of (H₂L₁ and H₂L₂) and their metal-ligand stability constants of their complexes with (Cd²⁺, Fe²⁺, Fe³⁺, UO₂²⁺ and Zr⁴⁺) metal ions have been determined potentiometrically in 0.1M KCl and 40 % (by volume) DMF-water mixture. The stability constants of the formed binary complexes were found to be Fe²⁺< Cd²⁺< Fe³⁺< UO₂²⁺< Zr⁴⁺. The effect of the substituents on the dissociation and stability constants was examined on the basis of the electron repelling property. The thermodynamic parameters (DG, DH and DS) were reported for the ligands and complexes formation reactions. The enthalpy changes for the dissociation processes and complex systems are positive. The dissociation processes are nonspontaneous and entropically unfavorable. The metal complexes have been found to be spontaneous and entropically favorable.

Azo rhodanines; Molecular Structures; potentiometry; Thermodynamics

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