Photo-induced reduction of Cr6+ by the hybrid systems “CuII complex with Schiff base and TiO2”: dependence on irradiation wavelength

Abstract

The synthesis of novel CuII complexes with a Schiff base obtained by condensation of salicylaldehyde and an l-aspartic acid ester are described. The physicochemical properties of the complexes were compared with those of related CuII complexes obtained earlier. All the complexes studied were characterized by elemental analysis as well as by IR, UV-Vis, and EPR spectroscopies. The activity of the complexes and their hybrid systems (HS) with TiO2 in visible-light-driven photocatalysis in organic solvents was investigated. After irradiation with visible light, the complexes and corresponding HS reduce Cr6+ to Cr3+ more efficiently than bare TiO2. To determine the molecular orbital compositions and energies and to explain the electronic spectra and redox properties of the systems studied, density functional calculations of the optimized structures of representative model complexes were performed.