Research Of Rare Earth Complexes Based On α-Keggin-type Polyxometalates

In this paper, eight unreported hybrid compounds have been synthesized by utilizing the[H₂W₁₂O₄₀]^6-(W₁₂)clusters as building blocks, and rare earth metal coordination complexesas linkers, with water solution synthesis methods. These eight compounds are structurallycharacterized by elemental analyses, IR spectra analyses, TG analyses，single crystal X-raydiffractions analyses. Magnetic properties and solid-state luminescence analysis of partialcompounds have also been tested and discussed.1. Five new compounds with2-D structure have been synthesized, based on W₁₂cluster asbuilding blocks and middle lanthanide ions and pyridine-3,5-dicarboxylic acid as linkers:（NH₄）₄[Eu2（L）₂（H₂O）9(H₂W₁₂O₄₀)]·11H₂O（1）（NH₄）₄[Gd2（L）₂（H₂O）9(H₂W₁₂O₄₀)]·11H₂O（2）（NH₄）₄[Tb2（L）₂（H₂O）9(H₂W₁₂O₄₀)]·12H₂O（3）（NH₄）₄[Dy2（L）₂（H₂O）9(H₂W₁₂O₄₀)]·11H₂O（4）（NH₄）₄[Er2（L）₂（H₂O）8(H₂W₁₂O₄₀)]·8H₂O（5）In compounds15, W₁₂cluster connects three Ln cations with three terminal oxygen atomsand Ln cations connect L1ligand, forming a W₂O₃Ln₂O₂C₅14-number ring. Each Ln2ionlinks two W₁₂clusters, as a result, a W₁₂-Ln polymeric chain is formed, and Ln1combines thepolymeric chains to form a2D sheet. Furthermore, the solid state luminescent properties ofcompounds1-4display that: five characteristic emission bands for Eu³⁺ions in the visibleregion in1，a broad band centered at479nm of ligand-center emission in2; three obviousemission peak for Tb³⁺ions in the visible region in3，two emission peak for Dy³⁺ions in thevisible region of compound4. The variable temperature magnetic research shows thatcompound5has antiferromagnetic coupling interaction.2. Three3-D structure compounds have been synthesized, by using W₁₂clusters as buildingblocks and heavy lanthanide ions, pyridine-3,5-dicarboxylic acid as linkers:（NH₄）₃[Tm3（L）₃（H₂O）15(H₂W₁₂O₄₀)]·10H₂O（6）（NH₄）₃[Yb3（L）₃（H₂O）15(H₂W₁₂O₄₀)]·11H₂O（7）（NH₄）₃[Lu3（L）₃（H₂O）15(H₂W₁₂O₄₀)]·13H₂O（8）In compounds68, there are three same crystallographily Ln³⁺ions, threepyridine-3,5-dicarboxylic acid and one [H₂W₁₂O₄₀]^6-. The W₁₂cluster as tridentate bridgingligand links three Ln³⁺ions forming [Ln3(H₂W₁₂O₄₀)]³⁺unit, from the view ofpolyoxometalate and in turn, the [Ln3(H₂W₁₂O₄₀)]³⁺unit is covalently bonded to six adjacent[Ln3(H₂W₁₂O₄₀)]³⁺cations by L with bridge-coordination mode, therefore, a3D framework isformed and can be rationalized as a（4^126^3） topology. The variable temperature susceptibilities show that compounds67have antiferromagnetic coupling interaction.