Synthesis and fluorescence properties of lanthanide(III) complexes of a novel bis(pyrazolyl-carboxyl)pyridine-based ligand.

A novel bis-pyrazolyl-carboxyl ligand, 2,6-bis(5-methyl-3-carboxypyrazol-1-ylmethyl)pyridine (L), was designed and synthesized and its several lanthanide(III) complexes Eu(III), Tb(III), Sm(III) and Gd(III) were successfully prepared and characterized in detail based on elemental analysis, infrared, mass, proton nuclear magnetic resonance spectroscopy and TG-DTA studies. Analysis of the IR spectra suggested that each of the lanthanide metal ions coordinated to the ligand via the carbonyl oxygen atoms and the nitrogen atom of the pyridine ring and pyrazole rings. The fluorescence spectra exhibits that the Tb(III) complex and the Eu(III) complex display characteristic metal-centered fluorescence in solid state while ligand fluorescence is completely quenched. However, the Tb(III) complex displays more effective fluorescence than the other complexes, which is attributed to especial effectivity in transferring energy from the lowest triplet energy level of the ligand (L) onto the excited state ((5)D(4)) of Tb(III).

Synthesis of Eu(III) and Tb(III) complexes with novel pyridine dicarboxamide derivatives and their luminescence properties.

A novel ligand, N2,N6-bis[2-(3-methylpyridyl)]pyridine-2,6-dicarboxamide (L2) and the corresponding Eu(III) and Tb(III) hydrochlorate complexes have been synthesized and characterized in detail based on elemental analysis, IR and NMR. The crystal and molecular structure of the complexes was determined by X-ray crystallography. The Eu(III) and Tb(III) ions were found to coordinate to the amido nitrogen atoms and pyridine nitrogen atoms. The luminescence properties of lanthanide complexes in solid state, in different solutions and in different pH value were investigated. The result shows that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes, and the ligand (L2) is an excellent sensitizer to Tb(III) ion.

Synthesis, characterization and fluorescence properties of novel pyridine dicarboxylic acid derivatives and corresponding Tb(III) complexes.

Two novel ligands containing two pyridine-2,6-dicarboxylic acid conjugative units, 4-(2-(2,6-dicarbox-ypyridin-4-yl)vinyl)pyridine-2,6-dicarboxylic acid (L1) and 4-(4-(2-(2,6-dicarboxypyridin-4-yl)vinyl)styryl)pyridine-2,6-dicarboxylic acid (L2) and their complexes with Tb(III) have been synthesized and characterized by elemental analysis, IR spectra and NMR. The ligand synthetic route was optimized and the yield of ligands reached over 78% as a result of the Wittig-Horner reaction used. The fluorescent intensities of these complexes with corresponding complexes with single pyridine-2,6-dicarboxylic acid unit was compared. The result has shown that the ligands with two pyridine-2,6-dicarboxylic acid units are the excellent sensitizers to lanthanide fluorescence. Also, we investigated the fluorescence properties of these complexes in different solution and in different pH value. Due to their excellent green-emmiter, they would be a potential candidate material for applications in organic light-emitting devices and medical diagnosis.