Synthesis and characterization of dinuclear europium complexes showing pure red electroluminescence

Two dinuclear Eu-III complexes have been synthesized by employing beta-diketones and 2,2'-bipyrimidine (bpm) as sensitizing ligands for the Eu ion and a bridging ligand, respectively, and characterized by various means including single-crystal X-ray crystallography. The use of dibenzoylmethane (dbm) and trifluorothenoylacetone (tta) as beta-diketones gave [Eu-2(dbm)(6)(bpm)] (1) and [Eu-2(tta)(6)(bpm)] (2). Both show strong intermolecular pi-pi interactions that may be responsible for their high melting points. The analysis of the absorption, excitation, and emission spectra of the dinuclear complexes along with a comparison with analogous mononuclear complexes containing the same beta-diketone ligands and 1,10-phenanthroline (phen) suggests that the dinuclear complexes follow the luminescence mechanism of general Ln(III) complexes. An EL device with the structure ITO/PEDOT/PVK + PBD + 110 wt.-%/LiF/Al shows pure red emission with an efficiency similar to those of mononuclear complexes. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006.