New Pyridine Derivatives And Its Rare Earth Complexes Synthesis, Characterization And Fluorescence Properties

Pyridine-2,6-dicarboxylic is the best sensitizer of the lanthanide (Tb³⁺, Eu³⁺ ions) than salicylic , phenanthroline. And the lanthanide complexes with-β-diketone-kind ligands are of high ability of UV-vis exicitation fluorescence, and the ligands make rare earth ions emit strong characteristic fluorescence by organic ligands'strong UV-vis absorbance and efficienct energy-transfer between the ligands and ions. Therefore,designing and synthesizing novel pyridine-2,6-dicarboxylic derivatives, especially di-β-diketone-kind compounds and their derivatives, is of great importance for searching and developing novel sensitizers for rare earth ions with pyridine-2,6-dicarboxylic as a starting material,and designing the structures of ligands is also a key point to discover new rare-earth ions fluorescent sensitizersIn this paper , a list of di-β-diketone organic ligands and their di-pyrazole derivatives which were not reported by references so far, and have big n-conjugated system were designed,and a novel di-β-diketone organic intermediate 2,6-bisbenzoylactyl pyridine (L₇) was synthesized by esterification and Claisen Condensation reaction using pyridine -2,6-dicarboxylic dacid which is a better fluorescent sensitizer as starting material and its two derivatives 2,6-di[(3-pyrazolyl)-5-phenyl] pyridine (L₈) and 2,6-di[(3-pyrazolyl)-3,5-diphenyls] pyridine (L₉) were successfully obtained by Condensation reaction with hydrazine hydrate and phenylhydrazine respectively, the above three novel ligands were confirmed by IR, ¹HNMR, GC-MS and EA. The Tb³⁺,Eu³⁺,Gd³⁺and Sm³⁺ complexes of ligand L7 were prepared. The possible structures of the above complexes were deduced by EA and IR roughly. The fluorescence properties of the solid complexes were investigated in detail,and the ligand L7 was proved to be a better sensitizer for Tb³⁺ and Eu³⁺. The Tb³⁺ complexes with ligand L₈ and ligand L9 were also preparedand charactered ,and ligand L₈ was found to be a better sensitizer for Tb³⁺ ions.Furthermore, in order to find and develop new organic fluorescence sensitizers, another list of novel pyridine-2,6-dimethylhydrazine and its derivatives pyridine-2,6-dimethylhydrazones organic ligands: furfurol-pyridine-2,6-dimethylhydrazine (L₄),benzaldehyde-pyridine-2,6-dimethylhydrazine (L₅) and salicylaldehyde - pyridine -2,6- dimethyl hydrazine (L₆) were synthesized successfully according to the design of molecule and the characteristic of organic fluorescence sensitizers, the above four novel ligands were confirmed by IR, ¹HNMR, GC-MS and EA. The Tb³⁺,and Eu³⁺ complexes of the four ligands were prepared.The contradistinctive experimental results show that the above four ligands can sensitize Eu³⁺ and Tb³⁺ ions to some extent; The ligand which has larger conjugate system is a better fluorescence sensitizer than the smaller conjugate system ligands, the fluorescence of the complexes with electron-donating groups is more intense than that of the complexes with electron-withdrawing groups; When the pH value is about at 7,fluorescence intensities of the complexes are strongest; while the less the dipole moment of solvent molecule is, the stronger the fluorescence intensity is;...