The present paper reports three new europium complexes,EuL₃(H₂O) 6,EuL₃Phen(H₂O)₄ and EuL₃(TPPO)(H₂O)₅,synthesized with Eu(NO₃) 3·6H₂O,2-(4-fluorobenzoyl) benzoic acid,Phen and TPPO(L=2-(4-fluorobenzoyl) benzoic acid,Phen=1,10-phenanthroline,TPPO=triphenyl phosphine oxide).Their composition and chemical structures were characterized by elemental analysis,IR and 1H NMR spectroscopy.The IR spectra indicated that all complexes exhibited the characteristic peaks of carboxylate,asymmetric stretching vibration (ν as (CO-₂)) and symmetric stretching vibration (ν s(CO-₂)) peaks;the C=O stretching band at 1 692 cm^-1 of COOH and the O—H stretching band around 2 500-3 200 cm^-1 disappeared.All these complexes had a smaller Δν(ν as (CO-₂)-ν s(CO-₂)) value than that of NaL,so the carboxylat groups coordinated with the europium ion in the form of bridging bidentate.In 1HNMR,the signals of hydrogen iN₂-(4-fluorobenzoyl) benzoic acid became wide and shifted upfield,and those in Phen,TPPO shifted downfield.The excitation and emission spectra were recorded at room temperature.The excitation spectra showed that the optimum excitation peaks of these three complexes,EuL₃(H₂O)₆,EuL₃Phen(H₂O)₅ and EuL₃(TPPO)(H₂O)₅,were at 353.0,355.0 and 357.0 nm,respectively.All these three complexes showed Eu³⁺ ion characteristic emission bands,the electron-dipole transition 5D0→ 7F2 and magnetism dipole transition 5D0→ 7F1;their emission peaks were at 596.0,617.0;596.0,619.0;595.0,620.0 nm,and the relative intensities were 1.1,8.6;15.2,100.0;3.6,23.2,respectively.The intensity of 5D0→ 7F2 was stronger than that of 5D0→ 7F1,which indicated that europium ions were at asymmetric center.The emission intensities of europium ions were greatly sensitized by Phen.