Bis(2-pyridyl)ditellane as a precursor to CoII, CuI and CuII complex formation: structural characterization and photocatalytic studies

Abstract

The reactions of bis(2-pyridyl)ditellane (2-PyTe)₂ with cobalt salts (CoCl₂·6H₂O and CoBr₂) and CuBr₂ resulted in the formation of three new coordination compounds [Co(2-Py₂Te₂-κN,N′)Cl₂] (1), [Co(2-Py₂Te₂-κN,N′)Br₂] (2) and [Cu(2-Py₂Te₂-κN¹,Te²,N^2′)Br]₂ (3), respectively. In compounds 1 and 2, the ligand is coordinated to cobalt(II) through the nitrogen atoms of the pyridyl groups. On the other hand, in compound 3, the coordination of the soft tellurium donor atom to the soft copper(I) metal center was also observed. Compound [Cu(2-Py₂TeClO-κO,N,N′)Cl]₂ (4) was formed using bis(2-pyridyl)ditellane as a precursor. After the generation of bis(2-pyridyl)tellane (2-PyTePy-2) in situ, CuCl₂·2H₂O was added in DMSO. During the reaction, the tellurium atom was oxidized from +2 to +4, with the formation of the anionic ligand [2-Py₂Te(Cl)(O)]⁻. All compounds 1–4 were characterized using spectroscopic techniques and single-crystal X-ray diffraction. Diffuse reflectance spectroscopy data were used to estimate the band gap energies of the compounds. The photocatalysts TiO₂-1 and TiO₂-2 were prepared and tested for hydrogen evolution from water splitting, using a 300 W Hg/Xe lamp as the irradiation source. Both photocatalysts have produced higher amounts of hydrogen when compared with pure TiO₂, suggesting that compounds 1 and 2 perform as effective photosensitizers.