Syntheses, Crystal Structure And Magnetism Of The Polyoxomolybdate/Vanadate

Polyoxomolybdates, an important branch in polyoxometalates chemistry, attractconsiderable attention for their interesting physicochemical properties and complicatedsolution chemistry. Six new compounds have been synthesized in aqueous solution andcharacterized by IR, UV-vis, single-crystal X-ray diffraction, thermal gravimetric, elementalanalysis, the surface photovoltage spectroscopy and magnetic analysis.1. Three new compounds based on [VMo₆O₂₂]^3-,[V2Mo6O26]^6-and [Mo₈O₂₆]^4-buildingblocks have been synthesized and structurally characterized:（H₃NCH₂CH₂NH₃）₃[Mo₆V₂22（CH₃COO）₃]·5H₂O （1）（H₃NCH₂CH₂NH₃）₂{（Mo₆V₂O26）[Cu（NH₂CH₂CH₂NH₂）（H₂O）2]}·4H₂O （2）NaH₃{Mo₈O₂₆[Cu（NH₂CH₂CH₂NH₂）2]}₂·H₂O （3）The compound1is a crown-shaped ring consisted of six edge-sharing {MoO6} octahedralinked to a central {VO₄} unit. The {MoO₆} octahedra are in pairs connected with thecarboxylato ligands from three acetic acid molecules. The structural feature of compound2isthe formation of1D zigzag chain in which [Mo₆V₂O26]^6-clusters are covalently bonded tocopper coordination groups through the terminal oxygen of the {VO4} tetrahedron. Themagnetic investigation on compound2demonstrates the possible occurrence ofantiferromagnetic interactions by intermolecular linkage. Compound3is a2D layer consistedof [Mo₈O₂₆]^4-and {Cu （NH₂CH₂CH₂NH₂）2} unit, which is further extended into3D networksby counter cations.2. Starting with NaAsO₂and Na₂MoO₄·2H₂O, a novel compound was obtained:[NH₂（CH₂CH₂）₂O]₂[H₃AsVMoVI₁₀Mo₂VO₉40)]·5H₂O （4）The compound4is Keggin structures of [AsMo12O40]n-with two molybdenum atomsare reduced. Bond valence sum calculations indicate that the arsenic atoms is in+V oxidationstate, ten molybdenum atoms are in+VI oxidation states, and two molybdenum atoms are in+V oxidation states.3. Two vanadomolybdenum heteropolyblue have been synthesized in aqueous solution, andstructurally characterized:[NH₃CH₂CH₂NH₃][SO₃MoVI₁₅V₃IVO₅₂]·6H₂O （5）[（VVO₄） MoVI₁₂O₃₆（VIVO）₆][（OH）₉]（6）The compound5is a mixed-vanadomolybdenum heteropolyblue with Dawson like structure.The surface photovoltage spectroscopy （SPS） measurements reveal that the compound5is thep-type-like conduction characteristic. Compound6is a mixed Mo/V six-capped Kegginstructural derivative, represents the transition metal polyoxocation.