Mono- and dinuclear Cu(II) complexes were prepared with pseudopeptidic open chain and macrocyclic ligands, respectively. They were characterized by UV-vis spectroscopy, EPR, HRMS and X-ray diffraction. The Cu(II) cation is coordinated by two amines and two deprotonated amides, in a slightly distorted square planar coordination geometry. The complexes interact with several substituted dicarboxylates, as shown by UV-vis titrations and EPR experiments. The interaction of both mono- and dinuclear complexes with very similar dicarboxylates of biological interest (malate and aspartate) resulted in strikingly different outcomes: in the first case a ternary complex [ligand⋯metal⋯dicarboxylate] was obtained almost quantitatively, while in the latter, the Cu(II) displacement to form Cu(Asp)2 was predominant.
