Tuning the Magnetic Interactions in Dy(III)₄ Single-Molecule Magnets

The study of mononuclear lanthanide-based systems, where the observed single-molecule magnets (SMMs) properties originate from the local description of the magnetic properties of the lanthanide ion, has been widely investigated through the literature. The case of polynuclear SMMs becomes more challenging both experimentally and theoretically due to the complexity of such architectures involving interactions between the magnetic centers. Many efforts have been focused on the understanding of the nature of these interactions and their effects on the SMM properties. In this work, a series of three structurally related tetranuclear dysprosium(III) SMMs, namely, [Dy₄(L)₄(OH)₂(DMF)₄(NO₃)₂]·2(DMF)·(H₂O) (1), [Dy₄(L)₄(OH)₂(DMF)₂(tfaa)₂]·2(CH₃CN) (2), and [Dy₄(L)₄(OH)₂(DMF)₂(acac)₂]·2(DMF) (3) (H₂L = 2-(2-hydroxy-3-methoxybenzylideneamino)phenol, Htfaa = trifluoroacetylactone, Hacac = acetylacetonate), has been synthesized and investigated. By a fine-tuning of the ligands on the changeable coordination sites in these Dy(III)₄ SMMs, the intramolecular magnetic interactions can be modified, switching from antiferromagnetic (for 1 and 2) to ferromagnetic (for 3). Ab initio calculations support these statements. In addition, the formation of 1 has been analyzed by ESI-MS analysis of the reaction mixture, indicating rather quick and high-yield formation of the [Dy₄] framework in solution. The combination of experimental work and ab initio calculations offers further insight into the relationship between structures and magnetic properties and sheds light on how to tune magnetic interactions in future polynuclear dysprosium complexes.