Fluoride Bridges as Structure-Directing Motifs in 3d-4f Cluster Chemistry

Publication: Research - peer-reviewJournal article – Annual report year: 2012

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  • Author: Birk, Torben

    University of Copenhagen2, Denmark

  • Author: Pedersen, Kasper

    University of Copenhagen2, Denmark

  • Author: Thuesen, Christian Aa.

    University of Copenhagen2, Denmark

  • Author: Weyhermüller, Thomas

    Max Planck Institute for Bioinorganic Chemistry, Germany

  • Author: Schau-Magnussen, Magnus

    University of Copenhagen2, Denmark

  • Author: Piligkos, Stergios

    University of Copenhagen2, Denmark

  • Author: Weihe, Högni

    University of Copenhagen2, Denmark

  • Author: Mossin, Susanne

    Centre for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark, Kemitorvet, 2800, Kgs. Lyngby, Denmark

  • Author: Evangelisti, Marco

    Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, Spain

  • Author: Bendix, Jesper

    University of Copenhagen2, Denmark

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The use of kinetically robust chromium(III) fluorido complexes as synthons for mixed 3d-4f clusters is reported. The tendency toward linear {CrIII–F–LnIII} units dictates the cluster topology. Specifically, we show that reaction of cis-[CrIIIF2(NN)2]NO3 (NN = 1,10-phenanthroline (“phen”) or 2,2′-bipyridine (“bpy”)) with Ln(NO3)3·xH2O produces isostructural series of molecular {Ln2Cr2} squares (1–9) with linear fluoride bridges. In a parallel fashion, fac-[CrIIIF3L], where L = N,N′,N″-trimethyl-1,4,7-triazacyclononane (“Me3tacn”), reacts with Nd(NO3)3·6H2O to form a fluoride-centered penta-nuclear complex and fac-[CrIIIF3L′], with L′ = 1,1,1-tris-((methylamino)methylethane) (“Me3tame”), reacts with [Ln(hfac)3(H2O)2] (hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone) to yield an isostructural series of {Ln3Cr2} (10–14) trigonal bipyramids with no central ligand. The formation of the latter is accompanied by a partial solvolysis of the Cr(III) precursor but without formation of insoluble LnF3. The magnetic properties of the gadolinium containing clusters allow quantification of fluoride-mediated, antiferromagnetic Gd–Cr exchange interactions of magnitude between 0.14 cm–1 and 0.71 cm–1 (Ĥ = J121·Ŝ2 formalism) and vanishingly small JGd–Gd of 0.06(0) cm–1. The large spin and small anisotropy together with weak exchange interactions in the {Gd3Cr2} (11) cluster give rise to a very large magneto-caloric effect of −ΔSm = 28.7 J kg–1 K–10H = 90 to 0 kOe).

Original languageEnglish
JournalInorganic Chemistry
Publication date2012
Volume51
Issue9
Pages5435-5443
ISSN0020-1669
DOIs
StatePublished
CitationsWeb of Science® Times Cited: 34
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