Ni(II) and Cu(II) complexes derived from thiophene-2,5-bis(thiosemicarbazone) as unprecedented templates for photocatalytic hydrogen production

Abstract

The reaction of thiophene-2,5-dicarboxaldehyde-bis-thiosemicarbazone (H2L) with nickel and copper salts in methanol yields the N2S2-coordinated complexes of formula ML (M=Ni,Cu). This work describes their characterization by NMR, FT-IR, Raman, UV-Vis absorption spectroscopy, thermogravimetric analysis and x-ray diffraction. The immobilization of both NiL and CuL complexes was succeed preparing TiO2-based photocatalysts by the sol-gel method, that were studied by solid-state UV-vis diffuse reflectance, energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), N2 adsorption-desorption and powder X-ray diffraction. The synthesized composites were also evaluated as photocatalysts in the hydrogen evolution reaction (HER) with the mesoporous NiL@m-TiO2 proven to be more active than CuL@m-TiO2, with a total amount of released hydrogen of ca. 6.200 mol g-1 of composite, after 6 h of irradiation with a 300 W Hg/Xe lamp.