DOI: 10.1002/chem.201000600 Dumbbell-Shaped Dinuclear Iridium Complexes and Their Application to Light-Emitting Electrochemical Cells RubØn D. Costa, [a] Gustavo Fernµndez, [b] Luis Sµnchez, [b] Nazario Martín,* [b] Enrique Ortí,* [a] and Henk J. Bolink* [a] Dedicated to Professor JosØ Barluenga on the occasion of his 70th birthday Introduction Multifunctional materials are designed to accomplish multi- ple performance objectives in a single system. [1] These objec- tives are usually related with optical, electrochemical, charge transport, and magnetic properties of the materials and with their integration into devices, such as organic pho- tovoltaics (PVs) or organic light-emitting diodes (OLEDs). [2–9] A special type of building block for multifunc- tional materials is organometallic complexes and, more spe- cifically, those complexes based on an iridiumACHTUNGTRENNUNG(III) metal core. Iridium complexes have been widely utilized in optoe- lectronics, owing to their relevant luminescent properties, such as high emission quantum yields, stability, long excited- state lifetimes, and easy tunability of the emission color. [10–14] One of the most outstanding applications of ionic transi- tion-metal complexes (iTMCs) is their use in the fabrication of a new type of solid-state electroluminescent devices, the so-called light-emitting electrochemical cells (LECs). LECs mainly consist of one active layer of a Ru II - or Ir III -based iTMC, [15, 16] in which the charge of the iTMC is compensated with small mobile anions, such as hexafluorophosphate (PF 6  ). The presence of mobile ions leads to the formation of ionic junctions when an external electric field is applied, which lower the barriers for hole and electron injection and make LECs independent of the work function of the elec- trode material. [9, 17–19] Therefore, air-stable electrodes, such as gold, silver, or aluminum, can be used in LECs, which makes its fabrication process cheaper and simpler compared to OLEDs. Abstract: A novel family of dumbbell- shaped dinuclear complexes in which an oligophenyleneethynylene spacer is linked to two heteroleptic iridiumACHTUNGTRENNUNG(III) complexes is presented. The synthesis, as well as the electrochemical and pho- tophysical characterization of the new complexes, is reported. The experimen- tal results are interpreted with the help of density functional theory calcula- tions. From these studies we conclude that the lowest triplet excited state cor- responds to a 3 p–p* state located on the conjugated spacer. The presence of this state below the 3 MLCT/ 3 LLCT emitting states of the end-capping Ir III complexes explains the low quantum yields observed for the dinuclear com- plexes (one order-of-magnitude less) with respect to the mononuclear com- plexes. The potential application of the novel dinuclear complexes in optoelec- tronic devices has been tested by using them as the primary active component in double-layer light-emitting electro- chemical cells (LECs). Although the luminance levels are low, the external quantum efficiency suggests that a near-quantitative internal electron-to- photon conversion occurs in the device. This indicates that the emission inside the device is highly optimized and that the self-quenching associated with the high concentration of the complex in the active layer is minimized. Keywords: electroluminescence · iridium · light-emitting electro- chemical cells · quenching pathways [a] R. D. Costa, Prof. Dr. E. Ortí, Dr. H. J. Bolink Instituto de Ciencia Molecular (ICMol) Universidad de Valencia P.O. Box 22085, 46071 Valencia (Spain) Fax: (+ 34) 963543273 E-mail: enrique.orti@uv.es henk.bolink@uv.es [b] Dr. G. Fernµndez, Dr. L. Sµnchez, Prof.Dr. N. Martín Departamento de Química Orgµnica Facultad de Ciencias Químicas Universidad Complutense, 28040 Madrid (Spain) Fax: (+ 34) 913944103 E-mail : nazmar@quim.ucm.es Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201000600. Chem. Eur. J. 2010, 16, 9855 – 9863  2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 9855 FULL PAPER