Potentiometric and Thermodynamic Studies of Some Azosulfoxine Derivatives and Their Metal Complexes

El-Bindary El-Bindary

doi:10.6000/1929-5030.2013.02.03.4

Abstract

The proton-ligand dissociation constants of some azosulfoxine derivatives and metal-ligand stability constants of their complexes with the metal ions (Mn2+, Co2+, Ni2+ and Cu2+) have been determined potentiometrically in 0.1 M KCl and 50 % (by volume) DMFâ€“water mixture at (298, 308 and 318) K. The stability constants of the formed complexes increases in the order Mn2+, Co2+, Ni2+ and Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavourable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favourable.

Highlights

There has been a growing interest in studying azo compounds especially heterocyclic compounds and their transition metal complexes, because of their wide importance in both academic and industrial fields [1,2,3,4,5,6]. These compounds and their metal complexes are interesting for various reasons
The azo compounds are used in dying processes; some of them are used in analytical separation of many metal ions in a mixture [4], redox active, pH-sensitive and their complexes act as a molecular switch [5]
In continuation of our earlier work [9,10,11,12,13], we report here the dissociation constant of 4Methoxyphenylazo-5-sulfo-8-hydroxyquinoline (L1), 4phenylazo-5-sulfo-8-hydroxyquinoline (L2) and 4nitrophenylazo-5-sulfo-8-hydroxyquinoline (L3) and the stability constants of their complexes with Mn2+, Co2+, Ni2+ and Cu2+ at different temperatures

Summary

Introduction

There has been a growing interest in studying azo compounds especially heterocyclic compounds and their transition metal complexes, because of their wide importance in both academic and industrial fields [1,2,3,4,5,6]. The average number of the protons associated with ligands (L1, L2 and L3) at different pH values, n A, was calculated from the titration curves of the acid in the absence and presence of ligands (L1, L2 and L3).

Results

Conclusion