Synthesis, characterization, enhanced photoluminescence and biological activity of Eu(III) complexes with organic ligands

Abstract

Six new europium(III) ternary complexes were synthesized with β-hydroxyketone, 2-hydroxy-4,6-dimethoxyacetophenone (HDAP) and 1,10-phenanthroline (phen) or 5,6-dimethyl-1,10-phenanthroline (dmph) or bathophenanthroline (bath) or 2,2-bipyridine (bipy) or 2,2-biquinoline (biq) or neocuproin (neo) as secondary ligand. The ligand and synthesized complexes, Eu(HDAP)3.phen(1), Eu(HDAP)3.dmph(2), Eu(HDAP)3.bath(3), Eu(HDAP)3.bipy(4), Eu(HDAP)3.biq(5) and Eu(HDAP)3.neo(6) were characterized by elemental analysis, infrared spectra, 1H-NMR spectra and powder XRD measurement. The photoluminescence behaviours of these complexes were checked by the excitation and emission spectra. The life time (τ) and quantum efficiency (η) of the complexes were determined based on the emission spectra and luminescence decay curve in solid state. The introduction of secondary ligands results in longer life time (τ) and higher quantum efficiency (η) in europium ternary complexes due to extended π-conjugation. All these europium ternary complexes exhibited highest excitation intensity at 395 nm, which perfectly matched with the emission spectra of commercial 395 nm emitting InGaN chips. These complexes emitted bright red luminescence (616 nm) corresponding to electric dipole transition 5D0 → 7F2 of Eu3+ ion, on exposure to UV source at 395 nm. Thus these complexes might be promising candidates for bright red light-emitting diodes used in display devices. In addition, in vitro antimicrobial and in vitro antioxidant properties of these complexes are reported. The results revealed that all these ternary complexes are excellent antimicrobial agents while are moderate antioxidant agent, except complex (3) which showed very high antioxidant power.