Synthesis and spectroscopic behavior of highly luminescent trinuclear europium complexes with tris-β-diketone ligand

• Synthesis of the tris-β-diketone ligand and its trinuclear europium complexes.
• Photoluminescence behavior of trinuclear europium complexes.
• Analysis of the Judd–Ofelt intensity parameters (Ωt), lifetime (τ) and quantum yield (η).

A new tris-β-diketone ligand, 2-[4,6-bis-(1-benzoyl-2-oxo-2-phenyl-ethyl)-[1,3,5]triazin-2-yl]-1,3-diphenyl-propane-1,3-dione (H3L), and its trinuclear europium complexes, Eu3(DBM)6L (C1), Eu3(DBM)6(Bipy)3L (C2) and Eu3(DBM)6(Phen)3L (C3) were synthesized and their spectroscopic behaviors were studied by FT-IR, 1H NMR, UV–vis and photoluminescence spectroscopic techniques. 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. The Ω2 and Ω4 intensity parameters, lifetime (τ) and luminescence quantum yield (η) were calculated according to the emission spectra and luminescence decay curves in solid state. The results indicated that these trinuclear europium complexes displayed a longer lifetime (τ) and higher luminescence quantum efficiency (η), especially complexes C2 (τ = 0.820 ms, η = 46.5%) and C3 (τ = 0.804 ms, η = 47.4%), which due to the effect of two additional europium ion lumophors and the introduction of the third ligands, Bipy or Phen in trinuclear complexes. Their Ω2 values demonstrated that the europium ion in these complexes is in a highly polarizable chemical environment.

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