Determination of Formation Constants and Association and Dissociation Rate Constants of Complex Ions by Means of Ion-Transfer Voltammetry

Abstract

Ion-transfer voltammetry of the facilitated transfer of Pb²⁺ ion by 1, 4, 7, 10, 13, 16-hexathiacyclooctadecane across the polarizable nitrobenzene/water interface has been applied to the study of complexes of Pb²⁺ ion with hydrophilic ligands, acetate^-, tartarate^2-, and citrate^3- ions in aqueous media. The formal formation constants of 1:1, 1:2, and 1:3 Pb²⁺-acetate^- complexes were determined to be 10^2.3M^-1, 10^3.0M^-2, and 10^4.0M^-3. The dissociation and association rate constants were determined to be 2.1×10³s^-1and 2.2×10⁷ M^-1 s^-1 for 1:1 Pb²⁺ -tartarate^2- complex and 4.5×10⁴s^-1 and 8.O×10¹⁰M^-1 s^-1 for 1:1 Pb²⁺ -citrate^3- complex, respectively.