Synthesis and luminescent properties of Eu(III) complexes of 2-thienyltrifluoroacetonate, terephthalic acid and trioctylphosphine oxide

This work reports the synthesis and luminescent properties of the terephthalic acid (TPA) and europium(III) (Eu(III)) with 2-thienyltrifluoroacetonate (HTTA) and trioctylphosphine oxide (TPPO), in the solid state. The new complexes Eu(TPA)(TTA)(TPPO)2 and Eu2(TPA)(TTA)4(TPPO)4 were characterized by elemental analysis, infrared spectroscopy, scanning electronic microscopy and thermal stability analysis. The complexes Eu(TPA)(TTA)(TPPO)2 and Eu2(TPA)(TTA)4(TPPO)4 present higher thermal stability than Eu(TTA)3(TPPO)2 does. And the formation of the binuclear/polynuclear structure of the complexes appears to be responsible for the enhancement of the thermal stability. The emission spectra present narrow emission bands that arise from the 5D0–7FJ (J = 0–4) transition of the Eu3+ ion. The spectral data of the complexes Eu(TPA)(TTA)(TPPO)2 and Eu2(TPA)(TTA)4(TPPO)4 show only one sharp peak in the region of the 5D0–7F0 transition indicating that only one Eu(III) ion species is present in each sample. In addition, the luminescence decay curves of the complexes Eu(TPA)(TTA)(TPPO)2 and Eu2(TPA)(TTA)4(TPPO)4 fit a single-exponential decay law. The values of quantum efficiencies of the emitting 5D0 level for the complexes Eu(TPA)(TTA)(TPPO)2 and Eu2(TPA)(TTA)4(TPPO)4 are 26.4 and 25.6%, respectively.