Probing the magnetic relaxation and magnetic moment arrangement in a series of Dy 4 squares.

Three μ4 -O bridged Dy4 squares, {[Dy4 (μ4 -O)(HL1 )4 (H2 O)4 ]2 (NO3 )3 (OH)}·2H2 O·2CH3 OH (1), [Dy4 (μ4 -O)(HL2 )4 (SCN)2 ]·2H2 O·4CH3 OH (2) and [Dy4 (μ4 -O)(H2 L3 )2 (SCN)2 ]·6H2 O (3) were assembled by using a Schiff base ligand and its dimerized and reduced congener, respectively. These complexes share a similar μ4 -O bridged Dy4 core, while, both the coordination geometry and metal-ligand interactions are slightly changed upon the modulation of the ligands, resulting in distinct single-molecular magnetic (SMM) and single-molecular toroic (SMT) properties. In complex 1, the Schiff base ligands are in an antiparallel fashion and all DyIII ions are in a similar coordination geometry, realizing the toroidal arrangement of magnetic moments. For complex 2, the reduced ligand H3 L2 in a parallel fashion results in double relaxation processes and a 9-fold increase of the Ueff . Interestingly, with the use of the dimerized ligand H6 L3 , we obtained complex 3, which is similar to complex 2, while due to the slight changes of the coordination environment both the single molecular magnetic property and toroidal magnetic moments almost disappeared.