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Issue 37, 2012
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Fluoride-bridged {Ln2Cr2} polynuclear complexes from semi-labile mer-[CrF3(py)3] and [Ln(hfac)3(H2O)2]

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Abstract

The trifluorido complex mer-[CrF3(py)3] (py = pyridine) reacts with 1 equiv. of [Ln(hfac)3(H2O)2] and depending on the solvent forms the tetranuclear clusters [Cr2Ln2(μ-F)4(μ-OH)2(py)4(hfac)6], 1Ln, and [Cr2Ln2(μ-F)4F2(py)6(hfac)6], 2Ln, in acetonitrile and 1,2-dichloroethane, respectively (Ln = Y, Gd, Tb, Dy, Ho, and Er; hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone). Reaction with [Dy(hfac)3(H2O)2] in dichloromethane produces the dinuclear cluster [CrDy(μ-F)F(OH2)(py)3(hfac)4], 3Dy. All the clusters feature fluoride bridges between the chromium(III) and lanthanide(III) centres. Fits of susceptibility data for 1Gd and 2Gd reveal the fluoride-mediated chromium(III)–lanthanide(III) exchange interactions to be 0.43(5) cm−1 and 0.57(7) cm−1, respectively (in the Image ID:c2dt31302b-t1.gif convention). Heat capacity measurements on 2Gd reveal a moderate magneto-caloric effect (MCE) reaching −ΔSm(T) = 11.4 J kg−1 K−1 for ΔB0 = 9 T → 0 T at T = 4.1 K. Out-of-phase alternating-current susceptibility (χ′′) signals are observed for 1Dy, 2Dy and 2Tb, demonstrating slow relaxation of the magnetization.

Graphical abstract: Fluoride-bridged {Ln2Cr2} polynuclear complexes from semi-labile mer-[CrF3(py)3] and [Ln(hfac)3(H2O)2]

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Publication details

The article was received on 17 Jun 2012, accepted on 26 Jul 2012 and first published on 30 Jul 2012


Article type: Paper
DOI: 10.1039/C2DT31302B
Citation: Dalton Trans., 2012,41, 11284-11292
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    Fluoride-bridged {Ln2Cr2} polynuclear complexes from semi-labile mer-[CrF3(py)3] and [Ln(hfac)3(H2O)2]

    C. Aa. Thuesen, K. S. Pedersen, M. Schau-Magnussen, M. Evangelisti, J. Vibenholt, S. Piligkos, H. Weihe and J. Bendix, Dalton Trans., 2012, 41, 11284
    DOI: 10.1039/C2DT31302B

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