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

Abstract 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 ( H 3 L ), and its trinuclear europium complexes, Eu 3 (DBM) 6 L ( C1 ), Eu 3 (DBM) 6 (Bipy) 3 L ( C2 ) and Eu 3 (DBM) 6 (Phen) 3 L ( C3 ) were synthesized and their spectroscopic behaviors were studied by FT-IR, 1 H NMR, UV–vis and photoluminescence spectroscopic techniques. These europium complexes exhibited the characteristic emission bands that arise from the 5 D 0  →  7 F J ( J  = 0–4) transitions of the europium ion in solid state. The Ω 2 and Ω 4 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 Ω 2 values demonstrated that the europium ion in these complexes is in a highly polarizable chemical environment.