Syntheses and cofluorescence of complexes of Eu(III)/Y(III) with terephthalic acid, 2-thenoyltrifluoroacetone and trioctylphosphine oxide

A series of Eu(III)/Y(III) complexes of terephthalic acid(TPA) with 2-thenoyltrifluoroacetone(HTTA) and trioctylphosphine oxide(TPPO) were synthesized. Compositions of these complexes are revealed to be Eu2(1-x)Y2x(TPA)(TTA)4-(TPPO)4 or Eu1-xYx(TPA)(TTA)(TPPO)2. Their IR spectra, fluorescent spectra and the thermal and optical stability were studied. The fluorescent excitation spectra of these complexes show more broad excitation bands than those of Eu2(TPA)3(TPPO)2 and Eu(TTA)3(TPPO)2 corresponding to their formations. In addition, both the binuclear complex EuY(TPA)(TTA)4(TPPO)4 and the chain complex Eu0.4Y0.6(TPA)(TTA)(TPPO)2 present higher thermal stability and better optical stability than the mononuclear complex Eu(TTA)3(TPPO)2 does. And their thermal and optical stabilities are preferably interpreted from the binuclear structure together with the chain polynuclear structure of the complexes. The fluorescence enhancement of cofluorescence Y3+ ions to the Eu(III) complexes is clear. The optimum content of Y3+ is 0.6 (molar fraction) for the chain complexes Eu1-xYx(TPA)(TTA)- (TPPO)2 and 0.5 for the binuclear complexes Eu2(1-x)Y2x(TPA)(TTA)4(TPPO)4. The formation of polynuclear structure of the complex Eu1-xYx(TPA)(TTA)(TPPO)2 appears to be responsible for the good cofluorescence effect of Y3+ ions.