Brightly Luminescent Red-Emitting Europium (III) Complexes Prepared with Fluro Quinoline and Ancillary Ligands

The liquid-assisted grinding method synthesizes six novel europium complexes with "6-fluoro-7-piperazinyl-4-quinoline" (L) and heterocyclic ancillary ligands. This synthesis method is eco-friendly and less time-consuming. The prepared complexes were characterised by various spectroscopic techniques CHN analysis IR, UV-Vis, XRD, EDAX and SEM. IR and NMR spectroscopic techniques indicate the mode of coordination of the ligand and ancillary ligand with metal ions. UV-vis absorption and reflectance spectra of the all complexes give information about the optical properties and Urbach energy of the complexes. Photoluminescent properties in powder and solution state suggest that the complexes show ruby red emission under UV radiation. The ⁵D₀ →⁷F₂ transition is responsible for emitting ruby red color. The intensity of europium transitions increases with the introduction of an ancillary ligand along with L. Judd Ofelt parameter is also vital to define the symmetry of lanthanide coordination environment and lanthanide-ligand bond's nature in the complexes. The LUMPAC software also validates the JO parameters. Color purity and the CCT (correlated colour temperature) values indicate that the complexes with high color purity, warm red-light sources, are used in the illuminating OLEDs. The thermal stability of complexes is investigated by thermogravimetric analysis and temperature-dependent photoluminescence. The branching ratio and lasing aspect were also precisely derived. As a result of all characterisation, these complexes are used in photoluminescent and optoelectronic devices. Complexes are a strong contender for the antimicrobial and antioxidant agent because they have good biological properties.