Photocatalytic ability of two hetero-tetranuclear complexes with CuO2Cd cores to degrade methylene blue: Influence of their structures on activity

Two centrosymmetric hetero-tetranuclear copper(II)/cadmium(II) complexes, (µ1,1-N3)2[(H2O)Cu(LR)Cd(N3)]2∙2CH3OH (1) and (µ1,1-NCS)2[CuLRCd(SCN)]2∙2CH3OH (2), have been prepared with a compartmental reduced Schiff base ligand, H2LR = 2,2′-[(2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)]bis[6-methoxy-phenol]. Both complexes have been characterized elemental and spectral analyses. Structures of both complexes have been confirmed by single crystal X-ray diffraction technique. Both complexes contain CuO2Cd cores. Here the bridging mode of azide and thiocyanate is quite different. Complex 1 contains µ-1,1-azide bridges between two cadmium(II) centres whereas in complex 2, µ-1,1-thiocyanate bridges occur between copper(II) and cadmium(II) centres. The ability of both complexes to be used as photo-catalyst in degrading methylene blue (MB) has been explored. The difference in photocatalytic performance may be correlated with their structures. Complex 1 shows better catalytic activity compared to complex 2, and can degrade almost 62% MB in 18 min. Comparative IR studies (before and after the photocatalytic degradation process) confirmed the stability of both catalysts.