Synthesis, Structure And Properties Of Germanium-Containing Polyoxometalates Based On Keggin And Derivatives

On the basis of molecular design and assembly, a series of organic-inorganicgermanium-containing polyoxometalates based on the monolacunary polyanion[α-GeW₁₁O₃₉]^8- and rare earth/transition/alkaline-earth metals have been synthesizedand characterized by X-ray crystallography, spectroscopic, thermal and magneticproperties.(1) Three types of germanotungstates based on the rare earth cations andmonovacant Keggin anions [α-GeW₁₁O₃₉]^8- have been synthesized and characterizedby elemental analysis, IR and UV spectroscopy, thermal analysis, and single-crystalX-ray diffraction. In these compounds, three kinds of clusters with theLn³⁺/[GeW₁₁O₃₉]^8- ratio of 1:1, 1:2 and 2:3 were observed. The 1:2 type moiety showsthe typical demric structure while the 1:1 type compound displays the interesting onedimensional chainlike arrangement. Especially, the 2:3 type displays the novel clusterbased on the rare earth and monolacunary Keggin polyoxometalate. The thermal andluminescent properties of several compounds were also studied.(2) We have successfully synthesized a novel alkaline-earth metal substitutedgermanotungstate derivative based on the lacunary Keggin-type polyanion andalkaline-earth metal cations displaying a three dimensional arrangement which is thefirst crystal structure that introduced the alkaline-earth metal cation Ca^â…¡into the[GeW₁₁O₃₉]^8- polyanion system.(3) A novel one dimensional chainlike organic-inorganic polymer has beensynthesized by hydrothermal reaction, and characterized by elemental analysis, IR,TG-DTA, EPR, magnetic properties, and single-crystal X-ray diffraction. It representsthe first high dimensional organic-inorganic hybrid based on the sandwich-typepolyoxometalates linked by transition metal coordination cations. (4) A novel polyoxometalate, which represents the first example of 1 Dorganic-inorganic hybrid based on a Keggin-type germanododecamolybdateheteropolyanion [GeMo₁₂O₄₀]^4- and an unprecedented isopolyanion [Mo₆O₂₂]^8-.(5) A one-dimensional coordination polymer, which represents the first exampleof 1 D organic-inorganic hybrid based on the bimolecular Keggin POMs has beenhydrothermally synthesized and displays a relatively strong antiferromagneticinteractions between the Cu^â…¡ions according to the magnetic study.