Single-Molecule-Magnet Behavior and Fluorescence Properties of 8‑Hydroxyquinolinate Derivative-Based Rare-Earth Complexes

Five tetranuclear rare-earth complexes, [RE4(dbm)4L6(μ3-OH)2] [HL = 5- (4-fluorobenzylidene)-8-hydroxylquinoline; dbm = 1,3-diphenyl-1,3-propanedione; RE = Y (1), Eu (2), Tb (3), Dy (4), Lu (5)], have been synthesized and completely characterized. The X-ray structural analyses show that each [RE4] complex is of typical butterfly or rhombus topology. Each REIII center exists in an eight-coordinated square-antiprism environment. Magnetic studies reveal that complex 4 displays single-molecule-magnet behavior below 10 K under a zero direct-current field, with an effective anisotropy barrier (ΔE/kB = 56 K). The fluorescence properties of complexes 1–5 were also investigated. Complexes 2–4 showed their characteristic peaks for the corresponding REIII center, while complexes 1 and 5 showed the same emission peaks with the ligand when they were excited at the same wavelength.