Synthesis And Luminescent Properties Of Europium Complexes Based On Imidazole Phenanthroline Carboxylic Acids And Schiff Base Containing Synergistic Ligands

In this thesis, the works can be mainly divided into two parts. The first part is about the synthesis and characterization of new europium complexes based on phenanthroline carboxylate derivatives containing imidazole moiety. The structural diagrams of the ligands were shown as follows:L（o-Br） L（m-Br） L（p-Br）L（o-NO₂） L（m-NO₂） L（p-NO₂）L（o-OCH₃） L（m-OCH₃） L（p-OCH₃）L（o-OH） L（m-OH） L（p-OH） L （o-COOH） L （m-COOH） L （m-COOH） L （p-CF₃）The ligands and the corresponding Eu（Ⅲ） complexes have been characterized by 1NMR, elemental analysis, TGA and IR spectra. The luminescent properties of the europium complexes were also systematically investigated.The results show that:these ligands have strong absorptions in the UV region with large absorption coefficient of about 1.0x10-4M cm^-1, which is important for antenna effects. This series of complexes have long luminescent lifetimes at about 1.5ms, indicating that the central ions were closely surrounded by the multi-dentate ligands, and there are no apparent vibration quenching of the excited state of Eu（Ⅲ） from solvent molecules. We analyzed the influence of different substituents on the luminescence properties of the complexes. Electron-withdrawing effects of-COOH,-NO₂ and-OH, reduce the triple state energy levels of the ligands, thus reduce the luminescent efficiencies of the complexes. Heavy atom effect of bromine atom increase the probability of the complex intersystem crossing, meanwhile, the suitable energy gap between the triplet state of the ligand and excited state of Eu（III） ion make the energy transfer between the ligand and the central ion very efficient, and as a result, the luminescent efficiency of m-Br complex is very high （43%）.In the second part, we mainly concern about the influence of different synergistic ligands on the structural and luminescent properties of the complexes composed of aromatic o-vanillin diamine Schiff base ligand （Ls） and europium （Ⅲ） ion.Five new europium complexes were obtained by the reaction of synergistic ligands 2-hydroxy-4-methoxy benzophenone （BP）, dibenzoylmethane （DBM）, a-thenoyl trifluoroacetone （TTA）,2-hydroxy-4-methoxy benzophenone （AP） with ligand （Ls） and Eu（NO3）3, respectively. Their composition were determined by elemental analysis and X-ray single crystal structure analysis. The triplet levels of the ligands, luminescent quantum efficiencies and lifetimes of the complexes were also measured in order to study the optical properties of the complexes systematically. The structure analysis results show that:most of the complexes contain both Eu3+ and Na+ in their crystal structures. The local geometries of eight-coordinated （or nine-coordinated） Eu3+ ions can be described as distorted bicapped triangular prisms （or tricapped triangular prisms）. The central ions were tightly wapped by the synergistic ligands and the multi-dentate Schiff base ligand.The luminescent analysis results find that:although the absence of the antenna-type sensitization was reported with the mono nuclear complexes of europium with this compartmental Schiff-base ligand, the synergistic ligands coordinated with Eu3+ ion can improve the luminescent efficiencies of the central ion apparently. Among the above synergistic ligands,2-hydroxy-4-methoxy benzophenone （BP） shows the best efficient synergistic sensitization effect, the luminescent quantum efficiency of the complex with BP ligand is about 5.33%. We speculated that the LMCT bands and the relative triplet levels may play important roles in shaping the emission processes of Eu3+ ions. In addition, the coordination of sodium ions and the ether oxygen and phenol oxygen atoms of the Schiff base ligands may also decrease the LMCT transition. The dominant of 5Do→7F2 emissions of the complexes show that the central ions do not locate at the inversion centers, which is consistent with the structure analysis results.