Constraining and Tuning the Coordination Geometry of a Lanthanide Ion in Metal-Organic Frameworks: Approach toward a Single-Molecule Magnet

It is available to constrain and tune the coordination geometries around lanthanide ions in metal-organic frameworks (MOFs) for the study of single-molecule-magnet (SMM) behavior. A series of Dy-III-MOFs are synthesized via a solvothermal method by using furan-2,5-dicarboxylic acid (H(2)FDA) as the ligand. {[Dy-2(FDA)(3)(DMF)2(])1.5DMF}(n) (1) and [Dy-2(FDA)(3)(DMF)(2)(CH3OH)](n) (2) show similar three-dimensional structures, but the coordination geometries around the dysprosium(III) ions in 1 and 2 exhibit different deviations from ideal square antiprism (D-4d symmetry) because of the coordinated solvent molecules. Slow relaxation of the magnetization can be observed for both complexes, indicative of SMM behavior. The effective energy barriers for 1 and 2 can be obtained from alternating-current susceptibility measurements by applying an external 2000 Oe direct-current field. MOF 2 possesses a less distorted D-4d coordination sphere and gives a higher effective energy barrier (U-eff) than that of MOF 1. Their diamagnetic Y-III-diluted samples 1aY and 2@Y exhibit similar relationships between the geometries and U-eff values, demonstrating that the magnetization relaxation is mainly from the symmetry-related single-ion behavior.