Tuning the Magnetic Anisotropy and Energy Barrier of Sulfido-Bridged Dy 2 Field-Induced Single-Molecule Magnets through Solvent Ligation

Coordinated solvent molecules are prevalent in lanthanide coordination complexes, a phenomenon attributed to the large ionic radii and high coordination demand for lanthanide ions. These solvent molecules typically exert a significant influence on the physical properties of the resulting complexes. Herein, we investigate the effect of coordinated solvent molecules on the magnetic properties of Dy(III) complexes by focusing on two single S2--bridged dinuclear Dy(III) complexes: Cp*2Dy(THF)2(μ2-S) (1) and (Cp*2Dy)2(μ2-S) (2) (Cp* = pentamethylcyclopentadienyl anion; THF = tetrahydrofuran). The coordinated THF molecules in 1 can be removed under vacuum to afford 2, while 1 can be reproduced by recrystallizing 2 from THF. Except for the presence or absence of THF molecules, the Dy(III) ions in both complexes are coordinated to two Cp* ligands and linearly bridged by a single S2- ion. Complete active space self-consistent field spin-orbit (CASSCF-SO) calculations revealed that the crystal field splitting of the spin-orbit-coupled ground states (6H15/2) of the Dy(III) ions in complex 2 is twice as large as that in complex 1, indicating that the coordinated THF molecules significantly modulate the magnetic anisotropy of Dy(III). Magnetic measurements demonstrated that complex 2 exhibits an enhanced slow magnetic relaxation behavior under an applied magnetic field of 1000 Oe with an energy barrier of 201(8) K.