Thermodynamic, spectroscopic studies and catechol oxidase activity of copper (II) complexes with amphiphilic d-galacturonic acid derived ligands

The interactions of three amphiphilic glycoligands derived from d-galacturonic acid (L1, L2 and L3) with copper (II) ions were investigated in aqueous solution and/or in aqueous-methanol media. The combination of potentiometry, UV–Vis spectrophotometry and Electron Paramagnetic Resonance (EPR) was used to determine the formation constants of the complexes and their relative structures in solution. The complexation sites were identified using electronic absorption and EPR spectroscopies. Copper complexes were obtained as square planar or square pyramidal mononuclear or dinuclear species. Solid compounds were synthesized and tested as catalysts in the autooxidation of catechols in methanol and in aqueous micellar media. Mononuclear species were found to be catalytically active in both media, whereas dinuclear ones do not show any significant catecholase activity.