EPR AND POTENTIOMETRIC REINVESTIGATION OF COPPER(II) COMPLEXATION WITH SIMPLE OLIGOPEPTIDES AND RELATED-COMPOUNDS

The coordination modes of Cu(II) to Di-, Tri-, and Tetra-glycine and r elated ligands were investigated, within the entire measurable pH rang e and over a wide range of ligand excess, by means of electron paramag netic resonance, electron spectroscopy, and in some cases, pH potentio metry. The results, besides allowing the identification of the complex species involved and the attribution of distinctive spectral data set to the various structures, provide significant insight in relation to : i) the coordination ability of the zwitterionic AH form of simple ol igopeptides to yield COO-- or 2COO(-)-complexes or species with mixed [(NH2,CO)(COO-)] or [(NH2,N-, COO-)(COO-)] coordination;) the influenc e of the size of the (NH2,CO), (NH2,N-), and (N-, COO-) chelated rings on the stability and structure of the complex species; iii) the bis-c omplex formation processes taking place with Gly-beta-ala, beta-Alagly , Tri-, and Tetra-glycine.