Inorganic–organic hybrid compounds based on octamolybdates and multidentate N-donor ligand: syntheses, structures, photoluminescence and photocatalysis

Abstract

Six inorganic–organic hybrid compounds, namely, [Cu₂(2,4′-tmbpt)₂(β-Mo₈O₂₆)(H₂O)₂]·7H₂O (1), [Cu(2,4′-tmbpt)(γ-Mo₈O₂₆)_0.5(H₂O)]·H₂O (2), [Co(2,4′-Htmbpt)₂(γ-Mo₈O₂₆)(H₂O)₂] (3), [Zn(2,4′-Htmbpt)₂(γ-Mo₈O₂₆)(H₂O)₂] (4), [Ni(2,4′-tmbpt)(α-Mo₈O₂₆)_0.5(H₂O)]·2.5H₂O (5) and [Ag(2,4′-Htmbpt)(β-Mo₈O₂₆)_0.5] (6), have been synthesized under hydrothermal conditions (2,4′-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3-(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole). The structures of compounds 1–6 have been determined by single-crystal X-ray diffraction analyses and characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD) analyses and thermogravimetric analyses (TGA). Compound 1 shows a 3D (3,4)-connected framework constructed by the 2D Cu(II)–organic fragments and [β-Mo₈O₂₆]⁴⁻ anions. Compound 2 exhibits a 2D layer structure based on Cu(II)–organic chains and [γ-Mo₈O₂₆] chains. The layers are extended into a 3D supramolecular framework by hydrogen-bonding interactions. Compounds 3 and 4 are isostructural, and display 1D chain structures. The chains are further interlinked by hydrogen-bonding interactions to form 3D supramolecular architectures. Compound 5 shows a 3D framework based on the 2D Ni(II)–organic fragments and [α-Mo₈O₂₆]⁴⁻ anions. In compound 6, the 1D chains constructed by the Ag(I) ions, 2,4′-Htmbpt ligands and [β-Mo₈O₂₆]⁴⁻ anions are extended by hydrogen-bonding interactions into a 2D supramolecular layer. Each layer threads into the adjacent layers, yielding a 2D → 3D interdigitated structure. Moreover, the photoluminescent properties of 4 and 6, the optical band gaps of 1–6, and the photocatalytic properties of 1–6 have also been investigated.