Rare Earth Coordination Polymers Of Nitrogen-containing Heterocyclic Polycarboxylic Acid-based Design, Synthesis, Structure And Properties

Compared with traditional inorganic materials, the synthesis conditions of coordination polymers are more facile, and the structures are easy to control. They have great potential applications in catalysis, gas adsorption and separation of gases, conductive, optical, magnetic, nonlinear materials fields. The lanthanide complexes with carboxylates have many special structures and the optical properties such as strong emission spectra, narrow emission peaks. They can be employed as environmental science materials, medical diagnostics, lighting and functional materials, and it has already produced a wide range of social and economic effects. However, the synthesis and property studies of the rare-earth coordination polymers have lagged a lot compared with the transition metal complexes. Aiming on the target of the excellent luminescence and magnetic properties, the main work of this thesis is selecting the multi-carboxylic acid ligand containing pyridine, imidazole, and the azo groups to construct four series of thermal-stability rare-earth metal organic polymers containing Ce, Sm, Nd, Eu, Tb ions. Among which, oxalate, formate and sulfate were employed as the auxiliary ligands to synthesize more than 20 of polymers. These polymers were structurally characterized by elemental analysis, IR, UV-vis spectra, TG-DTA, X-ray diffraction, respectively. The influence of metal ions, reaction temperature, and the ratio of lanthanide ion to ligand, pH value on the polymer network structure, even on the molecular interactions have been investigated. The results show that the Dy(Ⅲ) polymer exhibits ferromagnetism feature during the certain temperature range. The same end to end mode of the bridging formate ligand gives the different magnetic nature within lanthanide complexes. Series of coordination polymers display the fluorescence emission not only from f-f electronic transitions of the metal ions, but also the ligand to the central ion charge transition. We modified the hydrothermal reaction as the solvo-thermal synthesis method, and a new quaternary complex {[Nd3(Hpimda)2(μ2-HCOO) (μ2-C2O4)2·4H2O}n has been obtained. It has been found that this coordination polymer possesses the infinite 1-D channel, which is occupied by the coordinated and the free water molecules. After removal of solvate molecules, the polymer exhibits N2 adsorption property, and the characteristic near-infrared fluorescence originated from the Nd(Ⅲ) ion. The large ligand containing azo group has been synthesized, and further reaction with lanthanide salt to obtain a 3-D polymer. We found this large ligand obviously sensitized Dy(Ⅲ) ion, and the polymer has a certain porosity, as a further basis of rare earth ion exchange. The above work can provide the new optical materials and valuable experimental facts for design molecular structure of crystal engineering and for research of luminescence and magnetic materials.