Photochemical reduction of Cr(vi) compounds by amino acid Schiff base copper complexes with a hydroxyl group and titanium oxide composites in aqueous solutions

Synthesis of Cu(ii) complexes with condensation products of 2,4-dihydroxybenzaldehyde and four amino acids (l-alanine,l-valine,l-phenylalanine, and glycine) is reported. Their physicochemical properties are compared to each other and a previously studied Schiff base Cu(ii) complex, the product of condensation of salicylaldehyde andl-aspartic acid. The complexes were characterized by means of electrochemical, spectroscopic, and X-ray diffraction techniques. (TD-) DFT calculations were used for the assignment of transitions in UV-Vis spectra. Photocatalytic activity for reduction from Cr(vi) to Cr(iii) was studied under UV to visible light irradiation in methanol or water as sole complexes or hybrid systems with TiO2. For the first time among the analogous systems,in aqueous solutions, the complexes with TiO(2)reduced Cr(vi) to Cr(iii) efficiently. The Cr(vi) reduction ratio with theCuVDB-TiO(2)system reached 91%.