Solvent-induced Keggin-based Cd(II)/Ni(II) complexes constructed from pyridyl-tetrazole: Assembly, structures and properties

Abstract

Three Keggin-based CdII/NiII transition metal complexes, namely, [Cd(3-Hptz)4(CH3O)2](H3PMo12O40)·2H2O (1), [Cd(4-Hptz)4(CH3O)2](H3PMo12O40)·2H2O (2) and {[Ni3(4-ptz)2(4-Hptz)2(μ3-O)(H2O)2](HPMo12O40)}·5H2O (3) [3-ptzH=5-(3-pyridyl)-1H-tetrazole, 4-ptzH=5-(4-pyridyl)-1H-tetrazole], have been synthesized under solvothermal conditions and characterized by IR spectroscopy and single-crystal X-ray diffraction. The mixture of methanol and water was used as the solvent, which play an important role in the formation of compounds 1–3. Compounds 1 and 2 are isostructural. In 1, four 3-Hptz ligands and two methanol molecules coordinate with one CdII ion to form a [Cd(3-Hptz)4(CH3O)2] metal–organic unit, which links the adjacent discrete PMo12O403− (PMo12) anions through hydrogen bonding interactions to construct a 2D supramolecular layer. In compound 3, the tetrazole groups from one 4-Hptz and two 4-ptz ligands coordinate with three Ni ions to form a flat trinuclear subunit, which is further covered by another 4-Hptz vertically, resulting in a {[Ni3(4-ptz)2(4-Hptz)2(μ3-O)(H2O)2]2+ cluster. Adjacent trinuclear clusters connect with each other through pyridyl group of 4-ptz ligands to form a 1D chain. The PMo12 anions hang on both sides of the 1D chain, and methanol molecules may act as structure-directing agent in 3. The effect of central metals on the structures of the title compounds was discussed. In addition, the photocatalytic activities of the title complexes for the degradation of methylene blue under UV and sunlight irradiation have been investigated in detail.