New luminescent Eu(III) and Er(III) Schiff base complexes: synthesis, characterization and luminescence properties

Two new complexes of europium (III) and erbium (III) were synthesized from diaminodiphenylether bridged spacer in 1:1 molar ratio of ligand and metal salt, whereas the ligand was synthesized in 1:2 molar ratio of diaminodiphenylether and aldehyde. The synthesized complexes were structurally analyzed through nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), energy-dispersive X-ray diffraction (EDX), UV–visible and photoluminescence spectroscopy. In both synthesized complexes, the metals were found in coordination to nitrogen and oxygen atoms of the azomethine (HC = N) and hydroxyl (–OH) groups as evident by FTIR and NMR spectral results in both synthesized complexes. Molar conductivity data for Eu(III) and Er(III) observed in the range of 129–135.5 Ω⁻¹cm² mol⁻¹ determined that both complexes were 1:2 electrolytes. The presence of characteristic peaks for Eu, C, O and N was clearly identified in energy-dispersive X-ray diffraction, which confirmed its successful synthesis. Furthermore, the luminescence behavior of the complexes was investigated in the solution state with dichloromethane (DCM). Upon excitation at 274 nm, both complexes exhibited two emission bands centered at 379 nm to 399 nm and 519 nm for Eu(III) and Er(III). Consequently, the good emission properties illustrated that the synthesized complexes featured their potential as promising cost-effective luminescent materials.