Study on Synthesis, Structure Characterization and Fluorescence of Europium Complexes of 2-(4-Fluorobenzoyl) Benzoic Acid
The present paper reports three new europium complexes, EuL3(H2O)6,EuL3Phen(H2O)4 and EuL3(TPPO)(H2O)5,synthesized with Eu(NO3)3ยท6H2O, 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 CO 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(νas(CO-
2)-ν
s(CO-
2)) value than that of NaL, so the carboxylate groups coordinated
with the europium ion in the form of bridging bidentate. In 1HNMR, the signals of hydrogen in 2-(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 5
D
0→7
F
2 and magnetism dipole transition 5
D
0→7
F
1; their emission peaks were at 596.0617.0;596.0619.0;595.0620.0
nm, and the relative intensities were 1.18.6;15.2100.0;3.623.2, respectively. The intensity of 5
D
0→7
F
2 was stronger than that of 5
D
0→7
F
1,which indicated that europium
ions were at asymmetric center. The emission intensities of europium ions were greatly sensitized by Phen.
Keywords: 2-(4-fluorobenzoyl) benzoic acid; Complexes; Europium; Fluorescence spectra
Document Type: Research Article
Affiliations: China Dankong Industry and Trade Group Company, Taizhou 318000, China
Publication date: 01 January 2009
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