Syntheses And Luminescence Properties Of Rare-erath Complexes With 2-substituted Succinicacid

In this paper, eleven series of binary or ternary complexes of Eu(Ⅲ) and Tb(Ⅲ) were synthesized using succinic acid (L¹), methyl-succinic acid (L²), methylene-succinic acid (L³), mercapto-succinic acid (L⁴), bromo-succinic acid (L⁵), hydroxy-succinic acid (L⁶), laevo-hydroxy-succinic acid (L⁷) and dextro-hydroxy-succinic acid (L⁸) as the first ligand, 1,10-phenanthroline (phen) and 2,2′-bipyridine (bipy) as the second one, respectively. The compositions of the binary complexes and the ternary complexes were determined to be Ln₂(L)₃·4H₂O and Ln₂(L)₃M·2H₂O (Ln = Tb, Eu; L = succinic acid and its derivatives; M = phen, bipy), respectively, by elementary analysis, TG-DTA and compleximetry. The properties of all of complexes were characterized by means of IR spectra and fluorescence spectra at room temperature. The followings can be drawn out from the studies on the fluorescence spectra of the complexes:(1) There is a best proportion between the first ligand and the second ligand. In just this proportion, fluorescence intensity of the complex is the strongest. But the best proportion is different for different central metal ions or different systems.(2) The fluorescence intensities of the Tb(Ⅲ) and Eu(Ⅲ) complexes were greatly increased by the introduction of the second ligand.(3) The variations of substituents of the ligands have small influences on the position changes of complexes'excitation peaks and emission peaks, but large on the fluorescence intensities. In different systems, the influences of changes in substituents on fluorescence properties of the complexes are not exactly the same. However, the results show that, on the whole, the fluorescence intensities of the complexes increase with the increase of the abilities of electron-releasing of the ligands'substituents.(4) The chiralities of ligands have great influences on the fluorescence properties of the complexes. From the experimental results, we found that the fluorescence intensities of two complexes with chiral ligands were roughly equal, but were much stronger than those of the racemic complexes.Terbium complexes doped with yttrium and gadolinium (Tb:Gd/Y = 10:0～0:10) were synthesized and their fluorescence spectra were measured. It was found that the fluorescence intensity of the complex was the strongest when the molar ratio of terbium ion to the doping ion was 7:3. Based on the previous research,an optimum ratio was presented. A quaternary complex of terbium was synthesized by introducing yttrium as the doping ion and 1,10- phenanthroline as the second ligand, and the properties of the complex were characterized. By comparison, we found that the fluorescence intensity of the quaternary complex was little larger than the ternary complex, but much larger than the binary complex.