Enhanced optoelectronics properties of europium(III) complexes with β-diketone and nitrogen heterocyclic ligands

Preparation and photoluminescence behavior of six new europium complexes with beta-diketone 1-(2-hydroxy phenyl)-3-phenylpropane-1,3-dione (HPPP) and bathophenanthroline (batho), 2,2'-bipyridyl (bipy), 2,2'-biquinoline (biq), neocuproin (neo) and 1,10-phenanthroline (phen) are reported in solid state. The ligand (HPPP) and complexes Eu(HPPP)(3)center dot H2O (1), Eu(HPPP)(3)center dot phen (2), Eu(HPPP)(3)center dot batho (3), Eu(HPPP)(3)center dot bipy (4), Eu(HPPP)(3)center dot biq (5) and Eu(HPPP)(3)center dot neo (6) were characterized by means of elemental analysis, infrared spectroscopy, proton nuclear magnetic resonance (H-1-NMR). The optical properties, thermal stability and crystalline nature were investigated by photoluminescence spectroscopy, thermogravimetric analysis and XRD respectively. The emission spectra show narrow intense emission band of central europium (III) metal ion that arise from the high intense D-5(0) -> F-7(0) transition. The introduction of ancillary ligands like batho, bipy, biq, neo, phen enlarged the pi-conjugation system in complexes as a result higher luminescence intensity, longer life time (tau) and higher quantum efficiency (eta) observed in europium ternary complexes in comparison to Eu(HPPP)(3)center dot H2O (1). Based on the emission spectra, the luminescence decay curve was measured which indicated that the transfer of energy from HPPP ligand to the europium metal is more efficient in complexes 2-6 than complex 1.