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

Three sandwich-like [Ln 2 Fe 2 (B- α -FeW 9 O 34 ) 2 ] 10− clusters (Ln 2 Fe 4 , Ln = Dy( 1 ), Ho( 2 ), and Y( 3 )) were obtained by reacting Na 9 [B- α -SbW 9 O 33 ], Ln 2 O 3 , FeCl 3 •6H 2 O and KH 2 PO 4 . The [B- α -FeW 9 O 34 ] 11− units were formed via the in situ conversion of lacunary polyoxometalates (POM) [B- α -SbW 9 O 33 ] 9− and the Ln 3+ ions were generated from the slow dissolution of Ln 2 O 3 , both of which play important roles in the synthesis of Ln 2 Fe 4 . Ln 2 Fe 4 is the first 3d-4f cluster assembled from d-metal heteroatom-containing POM. The Dy 2 Fe 4 cluster exhibits single-molecule magnet properties with an 80 K energy barrier in an optimal DC field. Cyclic voltammetry tests and controlled-potential coulometry experiments show that the polyoxometalate Fe heteroatom in clusters 1–3 is also electrochemically active. Three polyoxometalate-based 3d-4f clusters featuring single-molecule magnet characteristics were obtained based on the synthetic strategies of conversion of lacunary polyoxometalates and lanthanide ion slow release.