A new family of five-coordinate lanthanide single-molecule magnets (Ln SMMs) [Dy(Mes*O)2 (THF)2 X] (Mes*=2,4,6-tri-tert-butylphenyl; X=Cl, 1; Br, 2; I, 3) is reported with energy barriers to magnetic reversal >1200 K. The five-coordinate DyIII ions have distorted square pyramidal geometries, with halide anions on the apex, and two Mes*O ligands mutually trans- to each other, and the two THF molecules forming the second trans- pair. These geometrical features lead to a large magnetic anisotropy in these complexes along the trans-Mes*O direction. QTM and Raman relaxation times are enhanced by varying the apex halide from Cl to Br to I, or by dilution in a diamagnetic yttrium analogue.
Keywords: aryloxides; lanthanides; magnetic anisotropy; paramagnetic relaxation; single-molecule magnets.
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