Trigonal Pyramidal {AsO2(OH)} Bridging Tetranuclear Rare-Earth Encapsulated Polyoxotungstate Aggregates

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• 作者：Hailou Li ; Yajie Liu ; Rui Zheng ; Lijuan Chen ; Jun-Wei Zhao ; Guo-Yu Yang
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：April 18, 2016
• 年：2016
• 卷：55
• 期：8
• 页码：3881-3893
• 全文大小：847K
• 年卷期：0
• ISSN：1520-510X

文摘

The one-pot assembly reaction of Na₂WO₄·2H₂O, RE(NO₃)₃·6H₂O, and NaAsO₂ in the participation of dimethylamine hydrochloride as an organic solubilizing agent in the acidic aqueous solution led to a class of trigonal pyramidal {AsO₂(OH)} bridging rare-earth substituted arsenotungstate (AT) aggregates [H₂N(CH₃)₂]₈Na₈{[W₃RE₂(H₂O)₈AsO₈(OH)][B-α-AsW₉O₃₃]₂}₂·65H₂O [RE = Eu^III (1), Gd^III (2), Tb^III (3), Dy^III (4), Ho^III (5), Y^III (6)], which were structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, and thermogravimetric (TG) analyses. The common structural feature of 1–6 is that their polyoxoanions consist of a novel tetrameric unit [(W₃RE₂(H₂O)₈AsO₈(OH))(B-α-AsW₉O₃₃)₂]₂^16– constituted by four trivacant Keggin [α-AsW₉O₃₃]^9– fragments linked through an unseen elliptical [W₆RE₄(H₂O)₁₆As₂O₁₆(OH)₂]²⁰⁺ moiety. Their polyoxoanionic infrastructures can also be described as a fusion of two equivalent dimeric subunits [(W₃RE₂(H₂O)₈O₇)(B-α-AsW₉O₃₃)₂]^8– bridged via two μ₂-{AsO₂(OH)} linkers. To the best of our knowledge, such a linking mode with trigonal pyramidal {AsO₂(OH)} groups as linkers connecting adjacent RE containing polyoxometalate moieties together is very rare. The thermal stability of 1–6 was also investigated on the crystalline samples, and the thermal decomposition processes of 1, 4, and 6 were comparatively deeply studied. The fluorescent properties and decay times of 1, 3, and 4 were measured, and they exhibit the characteristic emissions of RE centers. The lifetimes of 1 and 3 mainly originate from the contribution of RE ions whereas the overall lifetime of 4 is contributed by the synergistic interactions of AT fragments and Dy³⁺ ions.