Copper(II) complexes with l-lysine and l-ornithine: is the side-chain involved in the coordination?: A thermodynamic and spectroscopic study

The involvement of the ω-NH2 terminal group of l-lysine and l-ornithine in the complexation of Cu(II) was investigated by means of potentiometry, calorimetry, UV–Vis and ESR. The thermodynamic parameters (ΔG0, ΔH0 and ΔS0) obtained by combining the potentiometric and calorimetric data show that the two ligands complex copper(II) in a different manner, indicating that the ω-NH2 terminal group is involved in ornithine complexes only. UV–Vis and ESR spectra further support the involvement of ornithine ω-NH2 and provide details on the complexation geometries of the complexes of the two amino acids.