Photoluminescence performance of green light emitting terbium (III) complexes with β-hydroxy ketone and nitrogen donor ancillary ligands.

Abstract

An efficient and cost-effective technique, solution precipitation approach is adopted to synthesize five bright green luminescent terbium (III) complexes by employing the main β-hydroxy ketone ligand, 2-hydroxy-4-ethoxyacetophenone, and ancillary ligands like bathophenanthroline, 5,6-dimethyl-1,10-phenanthroline, 1,10-phenanthroline, and 2,2-bipyridyl. The elemental compositions and binding mode of ligand to terbium (III) ion can be validated by using energy dispersive X-ray analysis, elemental analysis, Fourier transform infrared, and proton nuclear magnetic resonance spectroscopy. The complexes are thermally stable up to 158°C and possess the cubic shaped particles as confirmed by thermogravimetric analysis and scanning electron microscopic study, respectively. The band-gap energy (3.02-2.92 eV) of complexes is reckoned through diffuse reflectance spectra, which tailors them as potential candidates in the field of military radars. The photoluminescence studies unveil that the complexes exhibit the bright green luminescence corresponding to 5 D4 → 7 F5 transition of Tb3+ ion (548 nm) under the excitation wavelength of 395 or 397 nm. The Commission International de I'Eclairage chromaticity coordinates (x, y) and color purity substantiates the green emission of complexes. The energy transfer mechanism elucidates that the main ligand and ancillary ligands sensitize Tb3+ ion, which in turn enhances the luminescence efficiency of the emissive layer of white organic light emitting diodes. The results reveal that the complexes are considered as good contenders in the field of display devices and laser technology. Lastly, in vitro antimicrobial and antioxidant activity proclaim the potent antimicrobial and antioxidant actions of complexes via tube dilution and 2, 2-diphenyl-1-picrylhydrazyl assays, respectively.