Self‐Assembly of [B‐SbW9O33]9− Subunit with Transition Metal Ions (Mn2+, Cu2+, Co2+) in Aqueous Solution: Syntheses,Structures and Magnetic Properties of Sandwich Type Polyoxometalates with Subvalent SbIII Heteroatom |
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| Authors: | Jing‐Ping Wang Prof Peng‐Tao Ma Jie Li Hong‐Yu Niu Jing‐Yang Niu Prof |
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| Institution: | Institute of Molecular and Crystal Engineering, School of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan, 475004, P.R. China, Fax: (+86)?378‐388‐6876 |
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| Abstract: | Rational self‐assembly of Sb2O3 and Na2WO4, or (NH4)18NaSb9W21O86] with transition‐metal ions (Mn2+, Cu2+, Co2+), in aqueous solution under controlled conditions yield a series of sandwich type complexes, namely, Na2H2Mn2.5W1.5(H2O)8(B‐β‐SbW9O33)2]?32 H2O (1) , Na4H7Na3(H2O)6Mn3(μ‐OAc)2(B‐α‐SbW9O33)2]?20 H2O (OAc=acetate anion) (2) , NaH8Na2Cu4Cl(B‐α‐SbW9O33)2]?21 H2O (3) , Na8KNa2K(H2O)2{Co(H2O)}3(B‐α‐SbW9O33)2]? 10 H2O (4) , and Na5H{Co(H2O)2}3W(H2O)2(B‐β‐SbW9O33)2]?11.5 H2O (5) . These structures are determined by using the X‐ray diffraction technique and further characterized by obtaining IR spectra and performing elemental analysis. Structure analysis reveals that polyoxoanions in 1 and 5 comprise of two B‐β‐SbW9O33]9? building units, whereas 2 , 3 , and 4 consist of two isomerous B‐α‐SbW9O33]9? building blocks, which are all linked by different transition‐metal ions (Mn2+, Cu2+, or Co2+) with different quantitative nuclearity. It should be noted that compound 2 represents the first one‐dimensional sinusoidal chain based on sandwich like tungstoantimonate building blocks through the carboxylate‐bridging ligands. Additionally, 3 is constructed from sandwiched anions Na2Cu4Cl(B‐α‐SbW9O33)2]9? linked to each other to form an infinitely extended 2D network, whereas 5 shows an interesting 3D framework built up from offset sandwich type polyoxoanion {Co(H2O)2}3W(H2O)2(B‐β‐SbW9O33)2]6? linked by Co2+ and Na+ ions. EPR studies performed at 110 K and room temperature reveal that the metal cations (Mn2+, Cu2+, Co2+) reside in a square‐pyramidal geometry in 2 , 3 , and 4 . The magnetic behavior of 1 – 4 suggests the presence of weak antiferromagnetic coupling interactions between magnetic metal centers with the exchange integral J=?0.552 cm?1 in 2 . |
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| Keywords: | antimony polyoxometalates sandwich complexes self‐assembly tungsten |
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