Slow Magnetic Relaxation Observed in Dysprosium Compounds Containing Unsupported Near-Linear Hydroxo- and Fluoro-Bridges

Abstract

The encapsulating N1,N3-bis(3-methoxysalicylidene)diethylenetriamine (H 2 valdien) ligand was employed to isolate two novel Dy III compounds which contain rare bridging pathways for lanthanide systems. Compound 1, [Na 2 Dy III 2 (valdien) 2 (μ-OH)(dbm) 2 (H 2 O) 2 ][Na 2 Dy III 2 (valdien) 2 (μ-OH)(NO 3) 2 (dbm) 2 ], where dbm - is dibenzoylmethanido, and compound 2, [Na 3 Dy III 2 (valdien) 2 (μ-F)(μ 3 -F) 2 (Cl) 2 (MeOH) 2 ] n ·0.5(MeOH)·(H 2 O), both exhibit linear lone hydroxo- and fluoro-bridges, respectively, between the metal centers. The unit cell of 1 comprises two discrete dinuclear molecules, which differ slightly, forming a cation-anion pair, while 2 forms a coordination polymer. The magnetic investigations indicate that both compounds display ferromagnetic coupling between the Dy III ions. Magnetic susceptibility measurements in the temperature range 1.8-300 K reveal that the Dy III ions in 1 are weakly coupled, resulting in a mononuclear single-molecule magnet-like behavior under an applied field. In the case of 2, the stronger coupling arising from the fluoride-bridge, leads to zero-field single-molecule magnet (SMM) behavior with a non-negligible anisotropy barrier (U eff) of 42 K. (Graph Presented).