Synthesis and photosensitization study of red luminescent europium (III) complexes with heterocyclic ligands for application in OLEDs

Six complexes of europium (III) with 1-ethyl-6-fluoro-1,4-dihydroxy-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid (L) as main ligand and 1,10-phenanthroline, bathophenanthroline, neocuprine, 2,2'-bipyridyl, 5,6dimethyl-1,10-phenanthroline as ancillary ligands were synthesized by grinding technique. Through study of thermogravimetric data, it can be concluded that these complexes exhibit excellent thermal stability which favour their use in organic light emitting diode fabrication. Crystalline nature of complexes was studied by powder XRD and SEM. H-1 NMR, C-13 NMR, FT-IR spectra displayed the coordination site in complexes and confirmed that ligand is present in the zwitterionic form. On monitoring the emission at 370 nm UV excitation, intense red color was observed at 615 nm due to D-5(0) -> F-7(2) electronic transition. Urbach energy, CIE coordinates, Judd-Ofelt parameters, quantum yield, CCT and lasing parameters were calculated. Refractive index and energy band gap values depicted their uses in semiconductor devices. Further investigation of antimicrobial and antioxidant assays certified the impressive antimicrobial and antioxidant activities of these complexes.