The near-infrared luminescence and magnetism of dinuclear complexes with different local symmetries constructed from a β-diketonate co-ligand and bis-Schiff base ligand

Abstract

Five new phenoxo-O bridged rare-earth (RE) dinuclear complexes, obtained by adopting the auxiliary ligand Hdbm (dibenzoylmethane) and a bis-Schiff base ligand H₂L (N,N′-bis(2-hydroxy-3-methoxybenzylidene)-propane-1,2-diamine), [RE₂(dbm)₄L·CH₃OH] (RE = Y (1), Dy (2), Ho (3), Er (4), and Yb (5)), were prepared and studied in terms of their structures, magnetic properties and NIR luminescence. Complexes 1–5 crystallize isomorphically in the space group P. More significantly, the two central ions of the complexes adopt different coordination modes and configurations. The symmetries of the two central rare-earth ions are D_2d and D_4d, respectively. The results of magnetic studies demonstrate that complex 2 shows frequency-dependent signals, with U_eff = 28 K. This is a typical feature of single-molecule magnets (SMMs). For complexes 3, 4 and 5, characteristic peaks were found during near-infrared (NIR) fluorescent measurements, resulting from the antenna effect. The photoluminescence lifetime (τ_av = 4.99 μs) and quantum yield (Φ_Ln = 0.25%) for complex 5 were obtained utilizing the luminescence decay curve.