Synthesis and Characterization of Dinuclear Europium Complexes Showing Pure Red Electroluminescence

Two dinuclear EuIII complexes have been synthesized by employing β-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 β-diketones gave [Eu2(dbm)6(bpm)] (1) and [Eu2(tta)6(bpm)] (2). Both show strong intermolecular π–π 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 β-diketone ligands and 1,10-phenanthroline (phen) suggests that the dinuclear complexes follow the luminescence mechanism of general LnIII complexes. An EL device with the structure ITO/PEDOT/PVK + PBD + 1 10 wt.-%/LiF/Al shows pure red emission with an efficiency similar to those of mononuclear complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)