Abstract
A series of 5-(4'-alkylphenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL) have been prepared and characterized by elemental analysis, H-1 NMR and IR spectra. X-ray diffraction pattern of ligand (HL2) was studied. The geometrical structures of these ligands are carried out by HF method with 3-21G basis set. Proton-ligand dissociation constant of ligands (HL) and their metal-ligand stability constants of Mn2+, Co2+, Ni2+ and Cu2+ have been determined potentiometrically in 0.1 M KCl and 30% (v/v) DMSO-water mixture at 298, 308 and 318 K. The stability constants of the formed complexes increase with the order: Mn2+ < Co2+ < Ni2+ < Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (Delta G, Delta H and Delta S) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favorable. Proton-ligand dissociation constant (pin of the ligands increases according to the following order p-(OCH3 > H > NO2) as expected from Hammett's constant (sigma(R)). (C) 2016 Elsevier B.V. All rights reserved.