Synthesis and photophysical properties of ternary β-diketonate europium(III) complexes incorporating bipyridine and its derivatives

Two new octa-coordinated ternary europium(III) complexes of the type [Eu(btfa)₃(Br₂-bpy)] (Eu-1) and [Eu(btfa)₃(PhE₂-bpy)] (Eu-2) (where btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione, Br₂-bpy = 5,5′-dibromo-2,2′-bipyridine, PhE₂-bpy 5,5′-bis(phenylethynyl)-2,2′-bipyridine) together with a previously reported complex [Eu(btfa)₃(bpy)] (Eu-3) have been synthesized. The complexes have been characterized by analytical and spectroscopic methods. The photophysical properties of the complexes have also been analyzed both experimentally and theoretically. The contribution of each ligand to the sensitized Eu(III) photoluminescence (PL) has been analyzed and is discussed. An energy transfer (ET) mechanism is proposed and discussed for the sensitized Eu(III) emission using experimental and theoretical data. The Eu(III) complex incorporating the parent bpy showed impressive performance as a double-emitting layer (EML) red organic light emitting diodes (R-OLEDs).