Novel Anderson-type [TeMo6O24]6−-based metal–organic complexes tuned by different species and their coordination modes: assembly, various architectures and properties

Abstract

Four novel Anderson-type polyoxometalates (POMs) [TeMo₆O₂₄]⁶⁻ (TeMo₆)-based metal–organic complexes (MOCs), namely, H₂[Zn₄(3-Hdpyp)₂(TeMo₆O₂₄)₂(H₂O)₁₆]·6H₂O (1), [Zn₃(3-dpyb)₂(TeMo₆O₂₄)(H₂O)₁₂]·8H₂O (2), [Cu₂(4-Hdpyp)₂(TeMo₆O₂₄)(H₂O)₆]·4H₂O (3), and [Cu₃(3-dpyp)₂(TeMo₆O₂₄)(H₂O)₈]·4H₂O (4) (3-dpyp = N,N′-bis(3-pyridinecarboxamide)-1,3-propane, 3-dpyb = N,N′-bis(3-pyridinecarboxamide)-1,4-butane, 4-dpyp = N,N′-bis(4-pyridinecarboxamide)-1,3-propane), were hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). In complex 1, two TeMo₆ polyoxoanions bridge Zn^II ions to generate a discrete tetranuclear zinc complex H₂[Zn₄(3-Hdpyp)₂(TeMo₆O₂₄)₂(H₂O)₁₆]. In 2, the TeMo₆ anions connect the metal–organic units [Zn₃(3-dpyb)₂]⁶⁺ to form an Anderson-type TeMo₆-based wave-like metal–organic chain. Both the discrete tetranuclear subunits in 1 and 1D wavy chains in 2 were further extended to 2D supramolecular networks through the hydrogen bonding interactions. In complex 3, the TeMo₆ anions link the metal–organic units [Cu₂(4-Hdpyp)₂]⁶⁺ to construct a 2D layer, which is further extended to a 3D supramolecular framework by the hydrogen bonding interactions. In complex 4, the TeMo₆ polyoxoanions bridge the Cu^II ions to generate a 2D Cu-TeMo₆ inorganic layer, which is further linked by the μ₂-bridging 3-dpyp ligands to form a 3D metal–organic framework. The effects of various coordination modes of TeMo₆ polyanions and the bis-pyridyl-bis-amide ligands, as well as the central metals on the structures of the title complexes have been discussed. Besides, the fluorescence, electrochemical properties and photocatalytic activities of the title complexes have been investigated in detail.