New Pyridine Derivatives And Their Eu (iii) And Tb (iii) Complexes, Synthesis And Fluorescence Properties,

Rare earth organic complexes have attracted considerable attention because of their excellent emission properties such as long emission lifetime, large Stoke's shift and narrow emission half-bandwidths. They have taken on great significance in applications as diverse as: liquid crystalline materials, sensors, luminescence probes for medical diagnosis, catalyst and so forth. Pyridine-2,6-dicarboxylic acid and its derivatives are excellent fluorescent sensitizer, they can form nine-coordinating luminescent complexes with lanthanide ions, the Eu(III) and Tb(III) complexes with such type of ligand are thermal stability, the luminescence intensities are strong, and the lifetime is long. They can be used to tag proteins and time-resolved fluoroimmunoassay (TR-FIA) field; Carbazole group has largeπ-conjugated system, special photo-electronic property and good hole transporting ability, therefore the carbazole fiinctionalized lgands have been used widely for luminescent devices.In this dissertation, starting from pyridine-2,6-dicarboxylic acid (DPA) and carbazole, we designed and synthesized a series of novelβ-diketone, bis-pyrazole and bis-pyrazolone ligands with largeπ-conjugated system. These largeπ-conjugated system ligands which were not reported in literature have rigid planar structure, and it is favourable to the transition of electron and transfer of energy.Firstly, two novelβ-diketone ligands, 1,1'-(2,6-bispyridyl) bis-3-(9-ethylcarbazole-3-yl)-l,3-propanedione (L₁) and methyl 6-(9-ethylcarbazole-3-yl)-oxoacetyl-2-pyridinecarboxylate (L₂), were successfully synthesized through esterification reaction, N-alkylation, Friedel-Crafts acetylation and Claisen condensation from the two starting materials. The reaction conditions of Friedel-Crafts acetylation and Claisen condensation were investigated. Furthermore, the bis-pyrazole ligand compound, 2,6-bis(5-(9-ethylcarbazole-3-yl)-pyrazole-3-yl) pyridine (L₃) was prepared by the condensation reaction of ligand L₁ and hydrazine hydrate. In addition, with a purpose of exploiting novel efficient organic luminescent sensitizer, another kind of bis-pyrazolone ligand, 2,6-bis(1 -phenyl-4-ethoxycarbonyl-5-pyrazolone-3-yl)pyridine (L₄) was synthesized. The structures of all ligands were characterized by the Fourier transform infrared (FT-IR) spectra, elemental analysis (EA), and proton nuclear magnetic resonance (¹H NMR) in detail.The rare earth binary complexes which were chelated by the four ligands and Eu(III) and Tb(III) ions were prepared. Meanwhile, with introduction of 1,10-phenanthroline as a secondary ligand, the two ternary complexes of ligand L₂ and lanthanide ions were prepared. The structures of all the complexes were characterized by the FT-IR, EA and thermogravimetric and differential thermal analysis (TG-DTA).The fluorescence properties of solid complexes were measured, the results show that a effective energy transfer process occurred form the ligands L₁,L₂ and L₃ to lanthanide ions, and subsequently the central ions can be sensitized efficiently. In particular, the Tb(III) complex exhibit a more excellent luminescence property than the Eu(III) complex for the same ligand. Meanwhile, comparing to the binary complexes, the introduction of secondary ligand Phen significantly enhanced the luminescent intensity of ternary complexes. The fluorescence emission of complexes is extremely narrow half-bandwidth and good monochromaticity, it could be used as candidate efficient luminescent materials and is significant for the developing of rare earth complexes luminescent materials.