Potentiometric study of metal complexes of some imidazole contained ligands : part I : the determination of dissociation constant of 2-(2-hydroxyphenyl)‎-4,5-diphenylimidazole and the stability of its complexes with some transition metal ions

Abstract EN

The study aims to determine the dissociation constant of 2-(2-hydroxyphenyl)-4, 5-diphenylimidazole (HPI) ligand, and also to study the complexes formation, in mixed (30 % H2O / 70 % dioxane), between the ligand and Cu (II), Ni (II), Co (II) and Zn (II).

Complex formation was traced and followed through measuring the stability constants of the formed complexes.

Potentiometric technique was used, to follow the change in concentration of one constituent in the reaction (titration) vessel during the coordination in solution.

The titration vessel contains : ligand, diluted strong acid and electrolyte salt to maintain constant ionic strength of 0.1 mol.dm-3 KCl ; a solution of divalent metal added in case of the determination of complex stability constants.

In this investigation a hydrogen concentration was followed through measuring the pH of the solution at various stages where basicity of the solution alters via adding alkali. Coordination and measurements were taken place at 35 °C, and the dissociation constant of the ligand with the stability constant of all the species formed in the solution were calculated by means of the HYPERAUADE 2008 computer program.