Two Dy(III) Single-Molecule Magnets with Their Performance Tuned by Schiff Base Ligands

To develop new lanthanide single-molecule magnets (SMMs), two new complexes of [Dy₂(MeOH)₂(HL¹)₂(NO₃)₂]·2MeOH (1) and [Dy₆(μ₃-OH)₂(L²)₂(HL²)₂(H₂L²)₂Cl₂(EtOH)₂]Cl₂·3EtOH·CH₃CN (2) were obtained by reacting Dy(NO)₃·6H₂O with 3-amino-1,2-propanediol in the presence of 2-hydroxynaphthaldehyde for 1 and by reacting DyCl₃·6H₂O with 1,1-di(hydroxymethyl)ethylamine in the presence of 2-hydroxynaphthaldehyde for 2, respectively, in which the Schiff base ligands of 3-(((2-hydroxynaphthaen-1-yl)methylene)amino)-propane-1,2-diol (H₃L¹) and 2-(β-naphthalideneamino)-2-(hydroxylmethyl)-1-propanol (H₃L²) were in situ formed. The two Dy(III) ions in 1 are linked by two O_alkoxy atoms of two (HL¹)^2- ligands to build a dinuclear skeleton. Complex 2 presents a nearly planar hexanuclear skeleton constructed from four edge-shared triangular Dy₃ units with the two peripheral Dy₃ units consolidated by two μ₃-O bridges and the two central Dy₃ units consolidated by one μ₃-O bridge. Obviously, they exhibit a different topological arrangement resulting from the linkage of the Schiff base ligands. Both of them are typical SMMs under zero dc fields, with a U_eff/ k_B value of 34 K for 1 and 40 K for 2, respectively. Multiple processes are involved in the relaxation processes of 1 and 2. The different SMM performances of the two titled complexes reveal a tuning effect of Schiff base ligands through tuning the coordination environments and topological arrangements of dysprosium(III) ions, which is supported by the theoretical calculations.