Synthesis and photoluminescent behavior of Eu(III) complexes with 4,4,4-trifluoro-1-(6-methoxy-naphthalen-2-yl)-butane-1,3-dione

• Four ternary europium complexes with the fluorinated β-diketone and nitrogen heterocyclic ligands were synthesized as potential photoluminescent materials.
• UV–vis absorption and photoluminescence spectra of europium complexes were investigated.
• The Judd–Ofelt intensity parameters (Ωt), lifetime (τ) and quantum efficiency (η) of europium complexes were calculated and analyzed.
• The complex EuL3·Phen displayed the longer lifetime τ (0.704 ms) and the higher luminescence quantum efficiency η (47.9%).

The fluorinated β-diketone ligand, 4,4,4-trifluoro-1-(6-methoxy- naphthalen-2-yl)-butane-1,3-dione (HL), and its ternary europium (III) complexes using water (H2O), 2,2-dipyridine (Bipy), 1,10-phenanthroline (Phen) and 4′-phenyl-terpyridine (Phterpy) as the secondary ligand were synthesized and characterized by elemental analysis, FT-IR, 1H NMR, UV–vis absorption, ESI–MS and fluorescence spectroscopic techniques. All these europium complexes exhibited the characteristic emission bands that arise from the 5D0 → 7FJ (J = 0–4) transitions of the europium ion in solid state. Based on their emission spectra and lifetimes, the Judd–Ofelt intensity parameters (Ω2 and Ω4), the radiative decay rate Arad, the nonradiative rates Anrad, and the quantum efficiency (η) were determined and compared. The ternary complexes, EuL3·Bipy, EuL3·Phen and EuL3·Phterpy, exhibited much higher quantum efficiencies and lifetime values, which can be attributed to the displacement of water molecules from the coordination sphere by the heterocyclic nitrogen donors. Especially, the complex EuL3·Phen exhibited the longest lifetime τ (0.704 ms) and the highest luminescence quantum efficiency η (47.9%) among these complexes. Meanwhile, complexes EuL3·Bipy, EuL3·Phen and EuL3·Phterpy also displayed higher Ω2 values than the complex EuL3·2H2O, indicating their hypersensitive character of the 5D0 → 7F2 transition and a highly polarizable chemical environment around the europium(III) ion.

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