Geometrical structure and potentiometric studies of 5-chloro-2,3-dihydroxy pyridine azo derivatives and their metal complexes

•Preparation of 5-chloro-2,3-dihydroxy pyridine azo derivatives•The molecular structure of the ligands is optimized theoretically.•Potentiometric studies of the ligands and their metal stability constants•The corresponding thermodynamic functions are evaluated and discussed.

5-Chloro-3-hydroxy-4-(phenylediazenyl)pyridine-2(1H)-one and its derivatives (HLn) were synthesized and characterized using different spectroscopic techniques. The geometrical structures of the ligands are carried out by HF method with 3-21G basis set. The proton-ligand dissociation constant of the ligands (HLn) and their metal-ligand stability constants with (Mn2 +, Co2 +, Ni2 + and Cd2 +) have been determined potentiometrically. The potentiometric studies were carried out in 0.1 M (KCl) and 10% (by volume) DMF-water mixture. The effect of temperature was studied at (298, 308 and 318 K) and the corresponding thermodynamic parameters (ΔG, ΔH and ΔS) 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.