Author(s)

Xuehui Zhao^1*, Zhongliang Hu¹, Haiyun Jiang¹, Feipeng Jiao², Zhengxiang Wang¹

¹Key Laboratory of Green Packaging and Application Biological Nanotechnology of Hunan Province, Hunan University of Technology, Zhuzhou, China.
²College of Chemistry and Chemical Engineering, Central South University, Changsha, China.

A series of complexes of europium (III)/gadolinium (III) with 2-thienyltrifluoroacetonate (HTTA), terephthalic acid (TPA) and phenanthroline (Phen) were synthesized by coprecipitation. The resulting complexes including Eu₂(TPA)(TTA)₄Phen₂, Eu_1.4Gd_0.6(TPA)(TTA)₄Phen₂, Eu_1.0Gd_1.0(TPA)(TTA)₄Phen₂ and Eu_0.8Gd_1.2(TPA)(TTA)₄Phen₂ were characterized by elemental analysis, IR spectroscopy and thermal stability analysis. The results of analysis indicate that the complexes obtained have similar binuclear structure with each other. The thermal stability analysis indicates that the complexes Eu₂(TPA)(TTA)₄Phen₂and Eu_1.0Gd_1.0(TPA)(TTA)₄Phen₂ possess good thermal stability, which melt at ~241°C and decompose at ~370°C - 430°C corresponding to the formation of the complexes. The fluorescence spectra of Eu_2(1-x)Gd_2x(TPA)(TTA)₄Phen₂ (x = 0 - 1) complex powders and their doped silica gels were studied. The co-fluorescence effect of Gd³⁺ ions in complex powders is different from that of their doped silica gels. The optimum concentration of Gd³⁺ for complex powders and their doped silica gels is 0.5 and 0.3 (molar fraction), respectively. The co-fluorescence distinction of Gd³⁺ ions for complex powders and their doped silica gels is preferably interpreted from the proposed binuclear structure together with monomolecular compositions of the complexes for the first time. Both intermolecular energy transfer and intra molecular energy transfer in cross binuclear monomolecular EuGd(TPA)(TTA)₄Phen₂ are thought to be responsible for the co-fluorescence effect of the complex powders; yet only the latter is thought to be responsible for the co-fluorescence effect in silica gels, for the complex molecules in this case are isolated from each other.

Co-Fluorescence, Europium, Terephthalic Acid, 2-Thienyltrifluoroacetonate, Silica Gel

Zhao, X. , Hu, Z. , Jiang, H. , Jiao, F. and Wang, Z. (2014) Syntheses and Co-Fluorescence of Complexes of Eu (III)/Gd (III) with Thienyltrifluoroacetonate, Terephthalic Acid and Phenanthroline. American Journal of Analytical Chemistry, 5, 1313-1321. doi: 10.4236/ajac.2014.517137.