Ligand Modulation of the Structures and Magnetic Relaxation in Triangular Dy 3 Complexes Based on a Tricompartmental Scaffold.

Using a novel tricompartmental hydrazone ligand, a set of trinuclear Dy 3 complexes has been isolated and structurally characterized. Complexes Dy 3  ⋅ Cl, Dy 3  ⋅ Br, and Dy 3  ⋅ ClO 4 feature a similar overall topology but different anions (Cl - , Br - , or ClO 4 - ) in combination with exogenous OH - and solvent co-ligands, which is found to translate into very different magnetic properties. Complex Dy 3  ⋅ Cl shows a double relaxation process with fast quantum tunneling of the magnetization, probably related to the structural disorder of μ 2 -OH - and μ 2 -Cl - co-ligands. Relaxation of the magnetization is slowed down for Dy 3  ⋅ Br and Dy 3  ⋅ ClO 4 , which do not show any structural disorder. In particular, fast quantum tunneling is suppressed in case of Dy 3  ⋅ ClO 4 , resulting in an energy barrier of 341 K and magnetic hysteresis up to 3.5 K; this makes Dy 3  ⋅ ClO 4 one of the most robust air-stable trinuclear SMMs. Magneto-structural relationships of the three complexes are analyzed and rationalized with the help of CASSCF/RASSI-SO calculations.