Copper(II) complex formation with a poly(amido) polymer containing optically active a-alanine residues

The complex formation between copper(II) and a polyampholyte ligand derived from α-alanine and 1,4-bis(acryloyl)piperazine was studied in aqueous solution by both thermodynamic (potentiometry, calorimetry) and spectroscopic (UV-visible, Electronic Spin Resonance, FT-infrared, Circular Dichroism) methods. It was found that a single complex species is formed in the acidic region and its thermodynamic functions (−ΔG°, −ΔH°, and ΔS°) were determined. Each monomeric unit of the polymer is involved in the coordination with the Cu(II) metal ion. Circular dichroism and infrared spectral data clearly reveal the participation of the carbonyl groups of the backbone in the copper(II) complex formation. The optically active center present in the coordinated amino acid residue shows a dissymmetric perturbation since it is involved in a five membered chelate ring fused with one of six members, whatever the pH.