Crystal Structure and Magnetic Properties of Peacock-Weakley Type Polyoxometalates Na 9 [Ln(W 5 O 18 ) 2 ] (Ln = Tm, Yb): Rare Example of Tm(III) SMM
Résumé
We report Peacock-Weakley complexes, Na 9 [Ln(W 5 O 18) 2 ]·35H 2 O, formed with Tm(III), 1, and Yb(III), 2. Their syntheses, physico-chemical characterizations, crystal structures, and magnetic properties are described. Ab initio calculations are also reported. These polyoxometalate (POM) complexes were obtained using original synthetic conditions where acidification was performed with a stoichiometric amount of nitric acid to an acidity of Z = ν(H +)/ν(WO 4 2-) = 8/10 = 0.80. Both the Tm(III) and Yb(III) derivatives were found to exhibit field-induced slow relaxation of their magnetization likely controlled by Raman and Orbach relaxation processes. 1 is a rare example of a Tm(III)-based single-molecule magnet (SMM) and is a consequence of the oblate tetragonal anti-prismatic symmetry of the coordination sphere.
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