Designing of europium(III) complexes with β-keto carboxylic acid and nitrogen-containing secondary ligand possessing optoelectrical, Urbach energy and lasing properties

Six bright red europium(III) complexes [Eu(L) 3 .H 2 O].11H 2 O-(C1), [Eu(L) 3 . dmph].11H 2 O-(C2), [Eu(L) 3 .bipy].11H 2 O-(C3), [Eu(L) 3 .neo].11H 2 O-(C4), [Eu(L) 3 .batho].11H 2 O-(C5) and [Eu(L) 3 .phen].11H 2 O-(C6) with L (9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid) as main ligand and N-donor heterocyclic aromatic system as secondary ligands were synthesized by solvent assisted grinding method. The synthesized complexes were characterized by elemental analysis and various spectral analyses like IR, 1 H-NMR, 13 C-NMR, and UV-vis. The thermal stability of these complexes was investigated by TG/DTG, and complexes were found thermally stable up to 244 °C. In order to investigate photophysical properties, excitation, emission spectra, and decay time curves were observed by PL spectrophotometer. On excitation at 397 nm in the UV-vis region, synthesized complexes emit crimson red color mainly due to the most intense 5 D 0 → 7 F 2 transition. In the chromaticity diagram, the CIE color coordinates (x, y) of complexes fall in the crimson-red region. CCT and color purity values were calculated using CIE color coordinates, indicating that the complexes emit warm red light with high color purity. Energy bandgap value and Urbach energy were computed from diffuse reflectance data of free ligands and synthesized complexes. The resulting output of these parameters suggests that the synthesized complexes were utilized in optoelectrical devices and semiconductors. Antimicrobial and anti-oxidant characteristics of synthesized complexes were examined by tube dilution and DPPH, respectively. The results showed that complexes have good anti-oxidant, antibacterial and antifungal behaviour. Graphical abstract Synopsis: Metal complexes containing ligand β-keto carboxylic acid and europium metal were synthesized. The synthesized complexes were characterised through NMR, IR spectroscopy. The high thermal stability of complexes was determined through TGA data. Photoluminescent properties were studied through emission, excitation and decay time. The synthesized complexes lie in red region of the CIE graph.