[Studies on the infrared and fluorescence spectra of europium lanthanum-benzoate complexes].
A series of mixed rare earth complexes of benzoic acid with europium and lanthanum were synthesized by the reaction of trivalent rare earth chlorides with ammonium benzoate in aqueous solution. Their composition is expressed with the general formula (Eu(1-chi)La(chi)) L3, where L = C6H5COO(-1), chi = 0.0-1.0. Their infrared and fluorescence spectra were investigated. The characteristic asymmetric (v(as)) and symmetric (v(s)) stretching vibrations of carboxyl group for rare earth complexes shift to lower frequency in comparison with sodium benzoate, and both the absorption bands show splitting. In addition, the difference between v(as) and v(s), deltav (120-125) cm(-1), is lees than that of sodium benzoate (deltav =137 cm(-1)). These situations show that the coordinating pattern of the carboxyl groups in the complexes is the form of chelation-bridging, therefore, it may be suggested that the rare earth (Eu, La) benzoates are a heteronuclear polymers. The dependence of the relative fluorescence intensity of the mixed rare earth complexes upon the content for La3+ ions was discussed. The results show that the emission intensity for Eu3+ ions can be greatly enhanced if a part of Eu3+ ions in europium benzoate were substituted by La3+ inos. When chi = 0.4, 0.5 or 0.7, the fluorescence intensity of the rare earth complexes can rise above 40%.
Lian
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Department of Chemistry, Inner Mongolia University, 010021 Hohhot.
Sheng
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H
Liu
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