Five new multinuclear rare earth complexes: Magnetism and near-infrared luminescence

Five new tri- and tetra-nuclear rare earth complexes utilizing a Schiff base ligand and co-ligand Hdbm were obtained: [Nd3(dbm)6(H2L)3]·3CH3OH (1), [RE4(dbm)6(L)2(CH3OH)3]·2CH3OH (RE = Dy (2), Ho (3), Er (4), Yb (5)), (H3L = N'-(2-carboxide-imidazole)-[(2-hydroxy-3-methoxyphenyl)methylene]hydrazide, Hdbm = 1,3-diphenyl-1,3-propanedione). Complexes 2–5 are centrosymmetric tetranuclear complexes with eight-coordinated REIII ions, while complex 1 is a non-centrosymmetric trinuclear complex with nine-coordinated NdIII ions, which could be caused by lanthanide contraction. The magnetic properties studies show that 2 exhibits representative single-molecule magnets behavior, leading to an energy barrier of 25.3 K as well as pre-exponential factor of 7.21 × 10−7 s. Research on near-infrared luminescence reveals that complexes 1, 3, 4 and 5 emit the characteristic emission peaks of the NdIII ions, HoIII ions, ErIII ions and YbIII ions, respectively. The luminescence lifetime and quantum yield of 5 are 1.39 μs and 0.0695 %, respectively.