How Far can the Anisotropy Deviate from Uniaxiality in a Dy-Based Single-Molecule Magnet? Dinuclear Dy(III) Complex Study

The DyIII ions in the dimer [Dy2(H2tea)2(O2CPh)4]·2H2O (1) (H3tea = triethanolamine) have the 9-coordinate monocapped square-antiprismatic ligand field environment. Compound 1 shows slow relaxation of magnetization which is observable only with applied magnetic fields. This is consistent with the idea that low-symmetry ligand fields allow for the quantum tunneling of magnetization. This is reflected by the fact that there are no observable maxima in the out-of-phase ac susceptibility above 1.8 K. The {g}-tensor of the DyIII ions {gx = 11, gy = 8.2, gz = 1} further underlying the reduced uniaxiality in this system was determined in electron paramagnetic resonance (X- and Q-band) studies of 1 at temperatures down to 4 K.