| Fluoride Bridges as Structure-Directing Motifs in 3d-4f Cluster Chemistry. | |
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MedLine Citation:
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PMID: 22497590 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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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 {Cr(III)-F-Ln(III)} units dictates the cluster topology. Specifically, we show that reaction of cis-[Cr(III)F(2)(NN)(2)]NO(3) (NN = 1,10-phenanthroline ("phen") or 2,2'-bipyridine ("bpy")) with Ln(NO(3))(3)·xH(2)O produces isostructural series of molecular {Ln(2)Cr(2)} squares (1-9) with linear fluoride bridges. In a parallel fashion, fac-[Cr(III)F(3)L], where L = N,N',N″-trimethyl-1,4,7-triazacyclononane ("Me(3)tacn"), reacts with Nd(NO(3))(3)·6H(2)O to form a fluoride-centered penta-nuclear complex and fac-[Cr(III)F(3)L'], with L' = 1,1,1-tris-((methylamino)methylethane) ("Me(3)tame"), reacts with [Ln(hfac)(3)(H(2)O)(2)] (hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone) to yield an isostructural series of {Ln(3)Cr(2)} (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 LnF(3). 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 = J(12)Ŝ(1)·Ŝ(2) formalism) and vanishingly small J(Gd-Gd) of 0.06(0) cm(-1). The large spin and small anisotropy together with weak exchange interactions in the {Gd(3)Cr(2)} (11) cluster give rise to a very large magneto-caloric effect of -ΔS(m) = 28.7 J kg(-1) K(-1) (μ(0)H = 90 to 0 kOe). |
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Authors:
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Torben Birk; Kasper S Pedersen; Christian Aa Thuesen; Thomas Weyhermüller; Magnus Schau-Magnussen; Stergios Piligkos; Högni Weihe; Susanne Mossin; Marco Evangelisti; Jesper Bendix |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-4-12 |
Journal Detail:
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Title: Inorganic chemistry Volume: - ISSN: 1520-510X ISO Abbreviation: - Publication Date: 2012 Apr |
Date Detail:
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Created Date: 2012-4-13 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0366543 Medline TA: Inorg Chem Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Department of Chemistry, University of Copenhagen , Universitetsparken 5, DK-2100 Copenhagen, Denmark. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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