Synthesis and characterization of the luminescent lanthanide complexes with two similar benzoic acids

2-((4-Methoxyphenoxy) carbonyl) benzoic acid, 2-(1-methoxyvinyl) benzoic acid and their rare earth complexes LnL2(OH)·3H2O (Ln = La, Eu, Tb) were synthesized and characterized by means of elemental analysis, FTIR, 1H NMR, UV and luminescence spectroscopy. The FTIR and 1H NMR results show that the carboxylic groups in the complexes coordinated to the rare earth ions in the form of one dentate, and the ester carboxylic groups have taken part in the coordination. Among these complexes, Eu(III) complexes and Tb(III) complexes exhibit characteristic fluorescence with comparatively high brightness and good monochromaticity, which indicated that the ligands of HLI and HLII are good organic chromophore to absorb and transfer energy to metal ions.