A series of heterometallic 3d-4f polyoxometalates as single-molecule magnets

Three sandwich-like[Ln2Fe2(B-α-FeW9O34)2]10-clusters(Ln2Fe4,Ln=Dy(1),Ho(2),and Y(3))were ob-tained by reacting Na9[B-α-SbW9O33],Ln2O3,FeCl3·6H2O and KH2PO4.The[B-α-FeW9O34]11-units were formed via the in situ conversion of lacunary polyoxometalates(POM)[B-α-SbW9O33]9-and the Ln3+ions were generated from the slow dissolution of Ln2O3,both of which play important roles in the syn-thesis of Ln2Fe4.Ln2Fe4 is the first 3d-4f cluster assembled from d-metal heteroatom-containing POM.The Dy2Fe4 cluster exhibits single-molecule magnet properties with an 80 K energy barrier in an opti-mal DC field.Cyclic voltammetry tests and controlled-potential coulometry experiments show that the polyoxometalate Fe heteroatom in clusters 1-3 is also electrochemically active.