Judd-Ofelt treatment on luminescence of europium complexes with β-diketone and bis(β-diketone)

Eu(DBM)32H2O and Eu2(DDBM)3H2O were synthesized by reactions between EuCl3 and chelating regents of β-diketone (dibenzoylmethane, HDBM) and bis(β-diketone) (1,3-bis(3-phenyl-3-oxopropanoyl)benzene, H2DDBM), respectively, and their luminescence properties were investigated by the fluorescence spectra and metastable state decay spectra. It was found that the relative intensity ratio of 5D0→7F2 to 5D0→7F1transition and the radiative lifetime shows a little change attributing to the different symmetry of europium ions, which Ω2 of Eu complexes with β-diketone and bis(β-diketone) are 13.08 and 12.24, respectively. Moreover, it was also found that the metastable state lifetime of Eu2(DDBM)3H2O is much longer than that of Eu(DBM)32H2O, due to smaller water quenching and lower triplet level of ligands. The Commission Internacionale d'Éclairage (CIE) chromaticity coordinates calculated from emission spectrum are x=0.637 and y=0.343 for Eu2(DDBM)3H2O, which presents high red color purity near 100%.