Synthesis, photoluminescence features with intramolecular energy transfer and Judd-Ofelt analysis of highly efficient europium(III) complexes

The luminescent binary and ternary europium(III) complexes were prepared by employing ethyl-(3-fluorobenzoyl) acetate (m-EFBA) as primary ligand and neocuproine (neo), bathophenanthroline (batho), 1,10-phenanthroline (phen) and 2,2-bipyridyl (bipy) as secondary ligands. The synthesized complexes Eu(m-EFBA)(3)center dot(H2O)(2) (C1), Eu(m-EFBA)(3)center dot neo (C2), Eu(m-EFBA)(3)center dot batho (C3), Eu(m-EFBA)(3)center dot phen (C4), Eu(m-EFBA)(3)center dot bipy (C5) were characterized by the means of elemental analysis (C, H and N), nuclear magnetic resonance spectroscopy (H-1-NMR), infrared spectroscopy (IR), thermogravimetric analysis (TG/DTG), UV-visible and photoluminescence (PL) spectroscopy. The photoluminescence spectra of complexes exhibit the characteristic emission band at 613 nm assigned to hypersensitive D-5(0) -> F-7(2) transition, responsible for the red color emission of complexes. The higher photoluminescence intensity of ternary europium(III) complexes C2-C5 as compared to binary complex C1, suggest that ancillary ligands neo, batho, phen and bipy enhance the process of sensitization from ligand (m-EFBA) to europium(III) ion. The luminescence decay time and quantum efficiencies of the complexes were determined to estimate the efficiency of energy transfer from ligand to metal ion. In addition, the Judd-Ofelt intensity parameters (Omega(2), Omega(4)) were calculated from the emission intensities of D-5(0) -> F-7(2) and D-5(0) -> F-7(4) transitions of europium(III) ion respectively. The intramolecular energy transfer mechanism of the complexes were also investigated and results indicate that the ligand (m-EFBA) and ancillary ligands effectively transfer the energy to that of Eu(III) ion.