Rare Earth Carboxylic Acid Synthesis, Structure And Nature Of The Study

Rare earth elements possess the same outside electron structure, but the inner 4f electronic level structure is similar, the rare earth complexes present unique chemical and physical properties. So they are applied widely in the optical, electrical, magnetic fields ect. They are regarded as a treasury of new materials. In the course of development of the rare earth functional materials, rare earth luminescent materials strike the eyes especially. Because of the abundance of rare earth resources in China and the uniqure luminescence properties of the rare earth complexes, they are applied more and more widely in industrys, agricultures, medicines and other high-technology industrys. Luminescence of rare earth organic complex is an across subject of the inorganic luminescence, organic luminescence and bioluminescence. The research of the luminescence of rare earth organic complex is significant for the theories, and it also get the application study value.In addition, those complexes possess various coordinating polyhedrons and structural changes. The research of their spacious structures and coordination environments is useful for knowing their crystal structures, and it is also in favor of the study of the relation between the crystal structure and the luminescence property, giving a theoretic foundation to design and synthesis a new luminous material.1. By the hydrothermal method and solution method, ten complexes were synthesized with 2-iodobenzoic acid (2-HIBA), 2-bromobenzoic acid (2-HBrBA), 2-chlorobenzoic acid (2-HC1BA), 4-fluorobenzoic acid (4-HFBA) as the first ligand, 1,10-phenanthroline(phen), 2,2'-bipyridine (2,2'-bipy) as the second ligand and trivalent rare earth compounds. Their crystal structures were determined by X-ray single crystal diffraction. And the structures of the complexes were confirmed by the element analysis, IR spectroscopy, thermal analysis, UV absorption spectrum, luminescence spectroscopy. It is considered that the carboxylic groups coordinate to the metal ions in four modes: monodentate, the chelating bidentate, the bridging bidentate, and thebridging-chelating tridentate. But in the complex [Eu(2-IBA)₃·H₂O]₂, the carboxylic groups were bonded to the Eu³⁺ ion in bridging- tetradentate coordination mode to form an infinite one-dimensional chain. This doesn't happen frequently. It is interesting that in the complex{[Pr(2-IBA)₃·2,2'-bipy]₂·[Pr(2-IBA)₃·2,2'-bipy]₂·C₂H₅OH·2H₂O} , Carboxylate groups coordinate Pr³⁺ ions adopting the same coordination modes, the Pr³⁺ ions are both nine-coordinated and the coordination environment of Pr³⁺ ions is similar. But the differences are the corresponding bond lengths and bond angles. And in the complex {[Tb(2-mA)₃·2,2'-bipy]₂·[Tb(2-IBA)₃·2,2'-bipy]₂·C₂H₅OH}, The Tb³⁺ ions are eight-coordinated and nine-coordinated owing to different coordination modes of carboxylate groups. Then the coordination environments of Tb³⁺ ions are different.2. By the hydrothermal method, two complexes were synthesized with diglycolic acid and trivalent rare earth compounds. Their crystal structures were determined by X-ray single crystal diffraction. Characterizations and studies of the complexes have also been given. In the complex Tb(C₄H₄O₅)_1.5·3H₂O and La(C₄H₄O₅)_1.5·3H₂O, there are both two types of metal ions coordinated environment. Ether oxygen atoms coordinate to the metal ions to form a network by a variety of coordination modes. Coordinated water molecules and uncoordinated water molecules form hydrogen bonds, enhancing the stabilities of the coordination compound.3. In the hydrothermal reaction, maybe because of the high temperature, the reactant was unexpected decomposed in the reactive process and the remaining formed two complexes. The complex Eu₂(PA)₆(phen)₂ (PA = phenylacetate ) was a binuclear molecule with an inversion center. The carboxylic groups were bonded to the Eu³⁺ ion in three modes, the chelating bidentate, the bridging bidentate, and the bridging-chelating tridentate. In the complex [Nd₂(C₂O₄)₃·4H₂O]_n, Nd atoms bridged by the oxalate groups in bidentate-bridging/ bidentate-bridging andbidentate-bridging/tridentate-bridging modes to form supramolecular structure.