EQUILIBRIUM STUDIES ON TRANSITION-METAL COMPLEXES OF PEPTIDES CONTAINING BISIMIDAZOLE LIGANDS

The complexes of copper(II) and zinc(II) ions with the ligands containing bis(imidazo-2-yl) group were studied by potentiometric and spectroscopic methods. The data obtained for the copper(II) and zinc(II) complexes of the ligands revealed the formation of stable mono- and bis-complexes with two or four imidazol-N in coordination. In the case of peptides containing strongly coordinating donor group (e.g. histidine) in the side chain the binding modes of ligands are slightly influenced. but the complex formation processes are not basically changed. The ionization of hydrogen of imidazole does not occur below pH approximately 11 in the parent complexes, but this process takes place in some ternary complexes around pH approximately 10.