The Quantitative Effect Of4-substituents On The Luminescence Properties Of The Rare Earth Complexes With Benzoic Acid

The absorptive capacity for UV and the triplet state energies of eight4-substitutedbenzoic acid （L） such as4-tert-butylbenzoic acid （L¹）,4-methylbenzoic acid （L²）,4-ethylbenzoic acid （L³）, benzoic acid （L⁴）,4-chlorobenzoic acid （L⁵）,4-bromobenzoicacid （L⁶）,4-cyanobenzoic acid （L⁷） and4-nitrobenzoic acid （L⁸） were obtained by UVspectroscopy, low temperature phosphorescence spectrum and the Gaussian calculations.The substituent effect on the absorptive capacity of the compounds was studied. Besides,the fluorescence properties of the binary europium and terbium complexes with thesecompounds were assessed through the triplet state energies. And the substituent effect onthe triplet state energies was also studied.Binary Eu（Ⅲ） and Tb（Ⅲ） complexes with compounds L¹-L⁸were synthesized andcharacterized by IR, UV, thermo-gravimetric analysis, elementary analysis andfluorescence spectrum. The results showed that the complexes could emit characteristicspectra of the rare earth ions. The strongest fluorescence emission peak of the europiumcomplex was about615nm and the terbium complex about544nm. However, thefluorescence intensity and quantum efficiency of the complexes had large differences.But it was consistent with the predicted results. Finally, the substituent effect of theligand on the fluorescence performance of the complexes was studied and explained.We synthesized the ternary Eu（Ⅲ） and Tb（Ⅲ） complexes with compounds L¹-L⁸asthe first ligands and1,10-phenanthroline as the second ligand. The complexes werecharacterized by elementary analysis, IR, UV, thermo-gravimetric analysis, andfluorescence spectrum. The results showed that the complexes could emit characteristicspectra of the rare earth ions. The strongest fluorescence emission peak of the europiumcomplex was about615nm and the terbium complex about544nm. However, thefluorescence intensity and quantum efficiency of the complexes had large differences.And the fluorescence intensities of the ternary complexes are much stronger than those ofthe binary complexes. These phenomenon were well explained by crystallized water, thesecond ligand and energy-matching mechanism. Furthermore, the quantitative ligand’s substituent effect on the luminescence properties of the ternary complexes was obtained.Finally, the quantitative relationship between the triplet state energies of the first ligandand the quantum efficiency of the complexes was obtained.We also synthesized terbium complexes with compounds L¹-L⁸which doped withLa（Ⅲ） or Gd（Ⅲ）. Meanwhile, we studied their fluorescence properties. Expect it, theinteraction of rare earth ions Eu³⁺ and Tb³⁺, and the effect of pH on the fluorescenceproperties of rare earth complexes were researched.