Near-infrared luminescence and magnetism of dinuclear lanthanide complexes constructed from a schiff-base and different β-diketonate coligands

Abstract

Seven new dinuclear lanthanide complexes based on a schiff-base ligand H2L and β-diketonate coligands have been synthesized and characterized: [Eu2(acac)4(HL)2]·3C2H5OH (1), [Ln2(acac)2(HL)4]·6C2H5OH (Ln = Tb(2), Dy(3), Er(4), Yb(5)), [Dy2(bfa)4(HL)2]·2H2O (6), [Dy2(tmhd)2(HL)4] (7) (H2L = 5-methylsalicylaldehyde-2-aminobenzoylhydrazone; Hacac = acetylacetone; Hbfa = benzoyltrifluoroacetylacetone; Htmhd = 2,2,6,6-tetramethylheptane-3,5-dione). These complexes are all centrosymmetric and bridged by phenoxo-O, offered with Ln2O2 cores. Meanwhile, the near-infrared luminescence measurements show that the characteristic emission peaks of ErIII (4) and YbIII (5) ions can be observed, which means the effective sensitization of the ligands. Subsequently, the dynamic magnetization properties studies show that 3, 6 and 7 exhibit slow magnetic relaxation behavior, typical SMM behavior, resulting in an effective barrier of 48.42 K (3) and 54.82 K (6) under an applied 800 Oe dc field, and 60.59 K for 7 under 3000 Oe dc field. In particular, this work demonstrates that the magnetic properties can be modulated by regulating the electron effects of terminal substituents on the coligands.