Synthesis And Photoluminescence Of Rare-Earth Complexes

Owning to its high excitation purity and low disturbance by the environment, the materials of rare-earth complexes have dramatic potential applications, such as applications in optical amplifiers, optical waveguides, OLEDs, fluorescence probes. Nevertheless, the current application of these materials is limited by their poor luminescence, which is caused by the competition of photoluminescence and the low efficiencies in energy transition between ligands and coordination center ions. For dealing with such problem, lots of works have been done by changing the structure of ligand, adding a second ligand and employing complexes as ligand and some achievement has been gotten with some task remaining.This research illustrates the latest developments in the rare-earth materials, the metal-organic frameworks (MOFs) and the rare-earth complexes. In addition, The research will also focus on the synthesis of two ligands, 1,1'-thiene-2,5-diybis- (3-phenylpropane-1,3-dione) and 1,1'-thiene-2,5-diyldibutane-1,3-dione. The photoluminescence properties of the complexes with these ligands will be analyzed, as well as the conditions for preparing rare-earth MOFs. Moreover, the structures and optical properties of ligands will be discussed, under the simulation by the software Guassian03.The research will include the following parts:1. Preparation for ligands and their photoluminescence properties.The two ligands, 1,1'-thiene-2,5-diybis(3-phenylpropane-1,3-dione) and 1,1'-thiene-2,5-diyldibutane-1,3-dione, were synthesized by Claisen reactions between dimethyl thiophene-2,5-dicarboxylate, which was prepared as the intermediate product with thiophene-2,5-dicarboxylic acid and methanol. Exciting by 417nm light, the peak emission wavelength of 1,1'-thiene-2,5-diybis(3- phenylpropane-1,3-dione) whose maxium UV-vis absorption is at 266nm and an other strong absorption at 377nm, in DMF was 462nm while exciting by 437nm light 1,1'-thiene-2,5-diyldibutane-1,3-dione in methanol whose maxium UV-vis absorption is at 364nm was 485nm.2. Preparation for the complexes and their photoluminescence properties. The Eu3+ and Tb3+ characterization emissions have not been observed in the spectra of the complexes, 1,1'-thiene-2,5-diybis(3-phenylpropane-1,3- dione)-Eu and 1,1'- thiene-2,5-diybis(3-phenylpropane- 1,3-dione)-Tb, under the peak emissions of 492nm and 483nm respectively. The red shifts of them comparing with that of ligands and the intensities were lower.The emission wavelength of complexes, 1,1'-thiene-2,5-diyldibutane-1,3- dione-Sm, 1,1'-thiene-2,5-diyldibutane-1,3-dione-Eu, 1,1'-thiene-2,5-diyldibutane- 1,3-dione-Tb and 1,1'- thiene-2,5-diyldibutane-1,3-dione-Dy, all located 492nm and the intensities were greatly lower than those of their ligands.3. The studies on the conditions for forming MOFsIn this research, three experiments under the conditions of (1)ligand and Ln ions, (2)ligand, second ligand and Ln ions, (3) ligand, second ligand, Ln ions and transition ions, were designed to test best conditions for coordination reaction and MOFs crystals'formation. The results suggested that the attendance of second ligand and transition ions may be suitable for coordination and crystals growth.4. Analysis of ligand structure and spectraApplying HF and DFT methods and simulating by the software Guassian03, the IR spectrums and UV-vis spectrums of different formations of ligand were obtained by calculating and comparing the experiment data. The most likely form of ligand was used to discuss the photoluminescence properties and fluorescence quenching of complexes.By the computer with Guassian03 applying HF and DFT methods, the IR spectrums and UV-vis spectrums of different formation of ligand were obtained by calculation and comparing the experiment data, the most likely form of ligand was used to discuss the photoluminescence properties and fluorescence quenching of complexes.