Syntheses, Crystal Structures and Properties of Two New Transition-Metal-Centered Heteropolytungstates

摘要

Two one-dimensional transition-metal-centered polyoxotungstates, that is, [Cu(en)₂][Cu(en)₂(H₂O)][Cu(en)(phen)][CuW₁₂O₄₀]·3H₂O (1) (en = ethylenediamine, phen = phenanthroline) and [Cu(en)₂]₂[Cu(en)₂(H₂O)]₂[V_5.8W_7.2O₄₀(VO)₄]·3H₂O (2) have been synthesized hydrothermally and structurally characterized by elemental analyses, IR spectroscopy, electrochemical analysis, thermogravimetric analysis and X-ray single crystal diffraction. Single-crystal structural analysis reveals that both of them represent one-dimensional structures constructed from transition-metal-centered Keggin-type polyanions bridged by secondary metal coordination groups of Cu-ligand. Noticeably, compound 1 exhibits a helical chain-liked structure, and the anion is coordinated by three Cu-ligand units, representing a copper-centered and tri-supported Keggin structure. In compound 2, the polyoxoanion [V_5.8W_7.2O₄₀(VO)₄]8− represents a V-centered tetra-capped pseudo-Keggin structure, and is coordinated by four Cu-ligand units. The three-dimensional supramolecular structures of compounds 1 and 2 are constructed through intermolecular hydrogen bonding interactions. The electrochemical and thermalstable properties of 1 and 2 are also studied. The results show the redox properties of polyoxotungstates are retained in title polymers.