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Slow magnetic relaxation in condensed versus dispersed dysprosium(III) mononuclear complexes.

Abstract : Reaction of the ligands 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)benzimidazole (L(1)) and 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)-3-(2-pyridinylmethyl)benzimidazole (L(2)) with Dy(hfac)3⋅2 H2O (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) gave mononuclear complexes [Dy(hfac)3(L(1))] (1) and [Dy(hfac)3(L(2))] (2). In both compounds the Dy(III) ion is surrounded by six oxygen and two nitrogen atoms. Complex 1 displays single-ion magnet (SIM) behaviour only in solution (Δ=12(1) K and τ0 =1.9(4)×10(-6) s), while complex 2 is a SIM in both solution (Δ=15(2) K and τ0 =1.5(3)×10(-6) s) and solid state (Δ=17(2) K and τ0 =9.5(2)×10(-6) s). The SIM behaviour is obtained if the hydrogen bond is broken by dissolution (1 in solution) or by alkylation (2). Multiple relaxation processes were identified for 2 with two competing processes: a fast one in zero field and a slow one for fields higher than 500 Oe. The two processes coexist for intermediate applied magnetic field. Magnetic-dilution and frozen-solution measurements led to the conclusion that the origin of these multiple relaxation processes is not due to the property of a single molecule.
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Contributor : Béatrice Mahi <>
Submitted on : Thursday, August 29, 2013 - 4:00:51 PM
Last modification on : Thursday, March 5, 2020 - 2:03:20 PM

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Goulven Cosquer, Fabrice Pointillart, Stéphane Golhen, Olivier Cador, Lahcène Ouahab. Slow magnetic relaxation in condensed versus dispersed dysprosium(III) mononuclear complexes.. Chemistry - A European Journal, Wiley-VCH Verlag, 2013, 19 (24), pp.7895-903. ⟨10.1002/chem.201300397⟩. ⟨hal-00855584⟩



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