Low-Coordinate Dinuclear Dysprosium(III) Single Molecule Magnets Utilizing LiCl as Bridging Moieties and Tris(amido)amine as Blocking Ligands

A low-coordinate dinuclear dysprosium complex {[Dy(N3N)(THF)][LiCl(THF)]}(2) (Dy-2) with a double bridging 'LiCl' moiety and tris(amido)amine (N3N)(3-) anions as a blocking ligand is synthesized and characterized structurally and magnetically. Thanks to the use of the chelating blocking ligand (N3N)(3-) equipped with large steric -SiMe3 groups, the coordination sphere of both Dy-III ions is restricted to only six donor atoms. The three amido nitrogen atoms determine the orientation of the easy magnetization axes of both Dy-III centers. Consequently, Dy-2 shows slow magnetic relaxation typical for single molecule magnets (SMMs). However, the effective energy barrier for magnetization reversal determined from the AC magnetic susceptibility measurements is much lower than the separation between the ground and the first excited Kramers doublet based on the CASSCF ab initio calculations. In order to better understand the possible influence of the anticipated intramolecular magnetic interactions in this dinuclear molecule, its Gd-III-analog {[Gd(N3N)(THF)][LiCl(THF)]}(2) (Gd-2) is also synthesized and studied magnetically. Detailed magnetic measurements reveal very weak antiferromagnetic interactions in Gd-2. This in turn suggests similar antiferromagnetic interactions in Dy-2, which might be responsible for its peculiar SMM behavior and the absence of the magnetic hysteresis loop.