Edaravone-Based Mononuclear Dysprosium(III) Single-Molecule Magnets

Using an edaravone-based aryloxide ligand, we assemble four new mononuclear Dy(III) compounds, [Dy(L1)(2)(CH3OH)(2)]middotBr (1); [Dy(L1)(2)(CH3OH)(2)]middotCl (2); [Dy(L1)(2)(CH3OH)(NO3)] (3); and [Dy(L2)(3)]middot2CH(3)OHmiddotH(2)O (4) (where L1 = methyl-substituted and L2 = p-tolyl-substituted ligands with NNO-tridentate coordination environments). As revealed by the magneto-structural and ab initio calculations, the complexes exhibited a slow relaxation of the magnetization at zero applied magnetic field where their magnetic properties were subtly tuned via chemical modifications on the dominant crystal field interaction. For the complexes with L1 analogue under eight-coordination, complexes 1 and 2 (D-4d symmetry) with noncoordinated halides showed better magnetic properties as compared to complex 3 (C-2v symmetry) due to the presence of a strongly coordinated nitrate anion that leads to a change in the structural arrangement. However, complex 4 (C-4v symmetry) with nine-coordination was found structurally unfavorable comparatively due to the coordination of an additional third ligand (L2) that leads to a higher coordination number as a result of the substituent change. Therefore, the presented compounds exhibit ligand substituent- as well as counterion-dependent magnetic property variations. A relatively higher effective energy barrier (U-eff) was obtained for the compounds having halide counter anions as compared with the neutral complexes. Moreover, the ab initio calculations revealed that the transition magnetic moment probabilities for these compounds present very small or even vanishing quantum tunneling of magnetization between the ground-state Kramers doublets and indicate that the slow relaxation might proceed through higher excited states. Finally, the described new compounds are expected to advance the aryloxide single-molecule magnets.

Automated summary

Using an edaravone-based aryloxide ligand, four new mononuclear Dy(III) compounds were synthesized. The complexes exhibited a slow relaxation of the magnetization, and the magnetic properties were influenced by chemical modifications on the dominant crystal field interaction and the presence of different counterions.