Heterocyclic chelating agents. Part II. Metal complexes of 2-(2-pyridyl)imidazole

Abstract

A study has been made of the metal complexes of 2-(2-pyridyl)imidazole (A) in aqueous solution at 25·0° and ionic background 0·1 M in nitrate ions. The acid dissociation constants of the protonated ligand species H₂A²⁺ and HA⁺ have been measured and are compared to those of similarly constituted ligands. Formation curves have been obtained and accurate formation constants for the complexes MA²⁺, MA₂²⁺, and MA₃²⁺(where M = Fe, Co, Ni, Cu, Zn, and Cd) have been calculated by a least-squares method. A mercury-electrode was used to determine the lower part of the Cu^II formation curve and the formation constants for the species HgA²⁺ and HgA₂²⁺ are quoted. The results are compared with those previously reported by us for the metal complexes of 4-(2-pyridyl)imidazole.