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Sequential Synthesis of 3d–3d′–4f Heterometallic Heptanuclear Clusters in between Lacunary Polyoxometalates

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posted on 25.02.2016, 00:00 by Rinta Sato, Kosuke Suzuki, Takuo Minato, Kazuya Yamaguchi, Noritaka Mizuno
In this work, we have successfully created several unprecedented discrete 3d–3d′–4f heterotrimetallic clusters in between lacunary polyoxometalates (POMs). By the three-step sequential introduction of metal cations into a trivacant lacunary POM TBA4H6[A-α-SiW9O34] (TBA = tetra-n-butylammonium) in organic media, five kinds of sandwich-type POMs with double-diamond-shaped 3d–3d′–4f heptanuclear clusters (IIIFeM4Ln2, TBAnHm­[FeM4­{Ln­(L)2}2­O2­(A-α-SiW9O34)2], M = Mn3+, Cu2+; Ln = Gd3+, Dy3+, Lu3+; L = acac (acetylacetonate), hfac (hexafluoroacetylacetonate)) were successfully synthesized for the first time. By introduction of two [Ln­(L)2]+ units on the ends of pentanuclear clusters [FeMn4O18(OH)2]23– and [FeCu4O18(OH)2]27–, the magnetic interactions between Mn3+–Mn3+ and Cu2+–Cu2+ could be modulated. Among a series of the heterometallic heptanuclear compounds, IIIFeMn4Lu2 exhibited the slow magnetic relaxation characteristic for a single-molecule magnet under the zero applied magnetic fields.