Multiple Carboxylic Acid Rare Earth Complexes To Build, Structure And Luminescent Properties

In recent years, the rational design and synthesis of novel lanthanide coordination polymers based on polycarboxylate ligand have attracted considerable attention. Polycarboxylate ligands are suitable for bridging ligands because of their versatile coordination modes. Especially, aromatic polycarboxylic acid is one of the most popular ligands in the construction of lanthanide coordination polymers with 1D, 2D and 3D structure and topological structure. Importantly, these complexes have potential applications in material field, such as in magnetism, catalysis, adsorption, and luminescent probes. Base on the previous researches, nine rare earth complexes have been synthesized by hydrothermal synthetical method. In these complexes, 1,2-phenylenediacetic acid and 2-sulfobenzoate are the first ligands and 1,10-phenanthroline is the second ligand. The general compositions of these complexes were confirmed by elemental analysis(C, H, N). The crystal structures were determined by X-ray diffraction.And the properties were characterized by IR, TG-DTA analysis and fluorescence spectra.1. Three new complexes {[Ln₂(1,2-pda)3(H₂O)2]·2H₂O}n(Ln = Tb(1), Dy(2) and Ho(3);1,2-H2pda = 1,2-phenyldendate) are synthesized by 1,2-phenylenediacetic acid and rare earth ions.In complexes, all 1,2-pda ligands coordinate metal ions in two coordination modes, bridging/chelating-bridging pentadentate mode and chelating-bridging/chelating-bridging hexadentate mode. Groups of 1,2-pda ligands link adjacent Ln3+ ions to form 1D infinite polymeric chain. These chains are further bridged together through 1,2-pda ligands to form 3D network with (6,3) topological structure.2. Six new complexes {[Ln₂(2-SB)3(phen)3(H₂O)2]·nH₂O}₂(Ln = Sm (1), n = 3; Ln = Eu (2), n = 2; Ln = Tb (3), n = 2; Ln = Dy (4), n = 2.5; Ln = Er (5), n = 2; Ln = Y (6), n = 2.5; 2-H2SB = 2-sulfobenzoate; phen = 1,10-phenanthroline) are synthesized by 2-sulfobenzoate and rare earth ions.In complexes, there are two types of Ln3+ ion coordination environments. Ln3+ ions are connected together through 2-SB ligands viaμ2-,η3- andη2- coordination modes, resulting in a tetranuclear molecule with central symmetry.The complexes with Sm(III), Eu(III), Tb(III) and Dy(III) hold good luminescence properties. Their fluorescence spectra behave characteristic transitions of lanthanide ions, respectively. The luminescence of europium and terbium complexes are stronger, whereas the luminescence of samarium and dysprosium complexes are weaker due to differernt multiplet energy of Sm(III), Eu(III), Tb(III), Dy(III) ions. The appropriate ligand for one given lanthenide ion can enhance luminescence intensity, coinstantaneously, the second ligand can both supply coordination number and enhance luminescence intensity of complex.