Slow magnetic relaxation in condensed versus dispersed dysprosium(III) mononuclear complexes.
Chemistry
; 19(24): 7895-903, 2013 Jun 10.
Article
em En
| MEDLINE
| ID: mdl-23589325
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)3â
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)â
K and τ0 =1.9(4)×10(-6) â
s), while complex 2 is a SIM in both solution (Δ=15(2)â
K and τ0 =1.5(3)×10(-6) â
s) and solid state (Δ=17(2)â
K and τ0 =9.5(2)×10(-6) â
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 500â
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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MEDLINE
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En
Ano de publicação:
2013
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Article