Metal complexation by α-mercapto- β-aryl acrylic acids

Abstract

Protonation constants of several α-mercapto-β-aryl acrylic acids and constants for formation of complexes between these ligands and bivalent metal cations were determined by computer-assisted analysis of pH-titration data. Ligand–metal ion mixtures in 50% (v/v) dioxane–water and in water, I = 0.1 M (NaClO4) were titrated at 25 °C with sodium hydroxide. Initial estimates of complex formation constants were refined with the SCOGS program. The ligands were shown to complex zinc(II) and nickel(II) metal ions avidly. These ligands potently inhibited the metal-dependent enzymes alkaline phosphatase, carboxypeptidase A, coeruloplasmin, and thermolysin. Partition of zinc(II) between aqueous and n-butanol or n-octanol phases was enhanced in favor of the organic phase by several of these complexants.