Compostos de coordenação de níquel(II) contendo ligante dioxo-halogenosselenito e de cobre(II) contendo ligante hidrogenosselenito: síntese, caracterização e aplicações

Abstract

This work describes the synthesis and structural characterization of five new coordination compounds containing inorganic ligands the dioxo-halogenselenate and hydrogenselenite anions. The compounds [NiCl(SeO2Cl)(bipy)2] (1), [NiCl(SeO2Cl)(phen)2] (2), [NiBr(SeO2Br)(bipy)2] (3), [NiBr(SeO2Br)(phen)2], (4) and [Cu2(μ-HSeO3)2(HSeO3)2(bipy)2] (5) were obtained from solvothermal syntheses and characterized by several techniques. The single-crystal X-ray diffraction analysis (XRD) allowed the elucidation of the structures of the compounds, provided data on angles and distances of bonds and allowed to verify the formation of anions with the incorporation of halides, which are to come from the starting materials. The powder X-ray diffraction (DRXP) and elemental analysis (AE) confirmed the structure and purity of the compounds. Raman spectroscopy and vibrational spectroscopy in the infrared (IV) region corroborated to confirm the main stretches and deformations present in the structures, while spectroscopy in the visible and ultraviolet region (UV-Vis) allowed to determine band gap values of compounds and composites, and also the electronic transitions present in the compounds, such as d-d transitions for Cu and Ni atoms and also π-π* transitions for coordinated aromatic ligands. The estimated band gap energies ranged from 2.48 to 3.40 eV. The energy dispersive X-ray analysis (EDS) and elementary mapping enabled an analysis of the surface of these compounds and their respective composites. Scanning electron microscopy (SEM) also allowed visualization of the morphology and average size of the analyzed samples. The compounds were used to prepare composites with TiO2 to act as photosensitizers for TiO2 for the production of H2(g) from water splitting. The results were promising, with an average production of 800 μmol of H2(g) per gram of photocatalyst after 7 hours of photocatalysis. Thus, this work presents the first nickel(II) coordination compounds organically templated containing dioxo-halogenselenate anions in their structures, as well as their characterizations and applications.