Spectroscopic studies of electron donor-acceptor interaction of 8-hydroxyquinoline with citric acid in different solvent.

Abstract

Charge transfer complex formation between 8-hydroxyquinoline as the electron donor with citric acid as the electron acceptor has been studied spectrophotometrically in ethanol and methanol solvents at room temperature. A new absorption band due to charge transfer complex formation was observed near 320 and 325nm in ethanol and methanol respectively. The stoichiometric ratio of the complex has been identified by Job’s and conductometric titration methods to be 3:1. Benesi–Hildebrand equation has been applied to estimate the formation constant and molecular extinction coefficient. It was found that the value of formation constant was larger in ethanol than in methanol. The physical parameters, ionization potential and standard free energy change of the formed complex were determined and evaluated in the ethanol and methanol solvents. The solid complex between 8-hydroxyquinoline and citric acid has been synthesized and characterized by using infrared and proton nuclear magnetic resonance spectrophotometry