Syntheses and Co-Fluorescence of Complexes of Eu (III)/Gd (III) with Thienyltrifluoroacetonate, Terephthalic Acid and Phenanthroline

Abstract

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 Eu 2 (TPA)(TTA) 4 Phen 2 , Eu 1.4 Gd 0.6 (TPA)(TTA) 4 Phen 2 , Eu 1.0 Gd 1.0 (TPA)(TTA) 4 Phen 2 and Eu 0.8 Gd 1.2 (TPA)(TTA) 4 Phen 2 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 Eu 2 (TPA)(TTA) 4 Phen 2 and Eu 1.0 Gd 1.0 (TPA)(TTA) 4 Phen 2 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) 4 Phen 2 (x = 0 - 1) complex powders and their doped silica gels were studied. The co-fluorescence effect of Gd 3+ ions in complex powders is different from that of their doped silica gels. The optimum concentration of Gd 3+ for complex powders and their doped silica gels is 0.5 and 0.3 (molar fraction), respectively. The co-fluorescence distinction of Gd 3+ 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) 4 Phen 2 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.