Abstract
Three highly luminescent Eu(III) complexes of the type [Eu(beta-diket.)(3)(tm-phen)] where beta-diket. = hexafluoroacetylacetone (hfaa), btfa; 4,4,4-trifluoro-1-phenyl-1,3-butanedione (btfa), 2-thenoyltrifluoroacetone (tta) and tm-phen = 3,4,7,8-tetramethyl-1,10-phenanthroline have been synthesized and characterized. The detailed photophysical properties of the complexes were analyzed both theoretically and experimentally. The theoretical photophysical properties calculated using the LUMPAC program [1] are in excellent agreement with experimental results. The Judd-Ofelt (J-O) parameters (Omega(2) and Omega(4)), radiative (A(rad)) and non-radiative (A(nrad)) decay rates were calculated and discussed. Chemical partition of the radiative decay rates (A(rad)) of electric dipole transitions revealed that beta-diketone contributes 77 to 84% while tm-phen contributes 22 to 16% towards the A(rad). The intramolecular energy transfer (W-ET) and back-energy transfer (W-BT) rate are predicted from the singlet (S-1) and triplet (T-1) levels to the emissive D-5(1) and D-5(0) states for Eu(III) and follow the path S-0 -> S-1 -> T-1 -> D-5(1) -> D-5(0) -> F-7(0,4). The complexes emit typical Eu(III) red emission with long luminescence lifetime (0.75-0.88 ms), show high intrinsic quantum yield (phi(Ln)) (66-70%) and may be used as one of the red components in light emitting devices.