Ligand Field Affected Single-Molecule Magnet Behavior of Lanthanide(III) Dinuclear Complexes with an 8‑Hydroxyquinoline Schiff Base Derivative as Bridging Ligand

New
dinuclear lanthanide­(III) complexes based on an 8-hydroxyquinoline
Schiff base derivative and β-diketonate ligands, [Ln2(hfac)4(L)2] (Ln­(III) = Gd (1),
Tb (2), Dy (3), Ho (4), Er
(5)), [Ln2(tfac)4(L)2] (Ln­(III) = Gd (6), Tb (7), Dy (8), Ho (9)), and [Dy­(bfac)4(L)2·C7H16] (10) (L =
2-[[(4-fluorophenyl)­imino] methyl]-8-hydroxyquinoline, hfac = hexafluoroacetylacetonate,
tfac = trifluoroacetylacetonate, and bfac = benzoyltrifluoroacetone),
have been synthesized. The single-crystal X-ray diffraction data show
that complexes 1–10 are phenoxo-O-bridged dinuclear complexes; each eight-coordinated center
Ln­(III) ion is in a slightly distorted dodecahedral geometry with
two bidentate β-diketonate coligands and two μ2-O bridging 8-hydroxyquinoline Schiff base derivative ligands. The
magnetic study reveals that 1 and 6 display
cryogenic magnetic refrigeration properties, whereas complexes 3, 8, and 10 show different SMM
behaviors with energy barriers of 6.77 K for 3, 19.83
K for 8, and 25.65 K for 10. Meanwhile,
slow magnetic relaxation was observed in 7, while no
out-of-phase alternating-current signals were found for 2. The different dynamic magnetic behaviors of two Tb2 complexes
and the three Dy2 complexes mainly derive from the tiny
crystal structure changes around the Ln­(III) ions. It is also proved
that the β-diketonate coligands can play an important role in
modulating magnetic dynamics of the lanthanide 8-hydroxyquinoline
Schiff base derivative system.