Benzoate Substituent Fluorescence Properties Of Rare Earth Complexes

A series of Tb³⁺ and Eu³⁺ complexes were synthesized and characterized. The effect of different ligands and substituts on the fluorescence intensity was analyzed in terms of ligand strcture, energy transfer and energy match, fluorescence enhancement effects of doping ions were also studied. The main work was divided into three parts.1. The binary and ternary complexes of Tb³⁺ and Eu³⁺ with benzoic acid and its derivatives with different substituts were synthesized and characterized by elemental analysis, IR spectra, UV spectra and fluorescence spectra. Fluorescence intensity of the complexes was different from each other greatly. In Tb³⁺ complexes, the sequence of fluorescence intensity was p-sulfobenzoic acid> p-methoxybenzoic acid> p-aminobenzoic acid> p-hydroxybenzoic acid> p-biphenylcarboxylic acid> p-methylbenzoic acid> benzoic acid> p-nitrobenzoic acid. In Eu³⁺ complexes, the sequence was p-sulfobenzoic acid> p-biphenylcarboxylic acid> p-methylbenzoic acid> p-methoxybenzoic acid> benzoic acid> p-hydroxybenzoic acid> p-aminobenzoic acid> p-nitrobenzoic acid. 1, 10-phenanthroline(phen) can enhance the fluorescence intensity of the complexes efficiently with p-methylbenzoic acid, p-methoxybenzoic acid and benzoic acid as the first ligand, in addition, fluorescence intensity of other complexes were not enhanced by adding phen.2. A series of Tb³⁺ and Eu³⁺ complexes were synthesized with benzenesulfoinc acid and its derivatives. Fluorescence intensity of the complexes formed by Tb³⁺ and benzenesulfonic acid or p-toluenesulfonic acid was weak, which could be enhanced efficiently by adding phen; fluorescence intensity of the complexes formed by Tb³⁺ and p-aminobenzenesulfonic acid was strong, which could be increased a little phen; fluorescence intensity of the complexes formed by Tb³⁺ and m-nitrobenzene sulfonic acid or 1, 5-naphthalene-1, 5-disulfonic acid was the weakest. Fluorescence intensity of Eu³⁺ complexes were generally low except formed by benzenesulfonic acid and phen.3. Synthesized a series of dinuclear complexes of Tb³⁺ and Gd³⁺ with the ligands of 4-biphenylcarboxylic acid and phen in different Tb³⁺ : Gd³⁺ ratio. The complexes are characterized by element analysis, IR spectra and fluorescence spectra. The results showed that the characteristic emission intensity of Tb³⁺ ion was greatly increased and possibly sensitized by Gd³⁺. At molar radio Tb³⁺: Gd³⁺=8.5: 1.5, fluorescence intensity of the complexes is the strongest, 14.4 times of pure Tb³⁺ complex.Synthesized a series of dinuclear complexes of Eu³⁺ and Gd³⁺ with the ligand 4-sulfobenzoic acid in differert Eu³⁺: Gd³⁺ ratio. The complexes are characterized by element analysis, IR spectra and fluorescence spectra. The results showed that the characteristic emission intensity of Eu³⁺ ion was greatly increased and possibly sensitized by Gd³⁺. At molar radio Eu³⁺: Gd³⁺=1: 9, fluorescence intensity of the complex is the strongest, 11.7 times of pure Eu³⁺ complex.