pubs.acs.org/Organometallics Published on Web 08/25/2009 r 2009 American Chemical Society 5478 Organometallics 2009, 28, 5478–5488 DOI: 10.1021/om9003785 Phenyl-1H-[1,2,3]triazoles as New Cyclometalating Ligands for Iridium(III) Complexes Beatrice Beyer, † Christoph Ulbricht, ‡ Daniel Escudero, § Christian Friebe, † Andreas Winter, ‡ Leticia Gonz alez,* ,§ and Ulrich S. Schubert* ,†,‡ † Laboratory of Organic and Macromolecular Chemistry, Friedrich-Schiller-Universit € at Jena, Humboldtstrasse 10, 07743 Jena, Germany, ‡ Laboratory of Macromolecular Chemistry and Nanoscience, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands, and § Laboratory of Theoretical Chemistry, Friedrich-Schiller-Universit € at Jena, Helmholtzweg 4, 07743 Jena, Germany Received May 11, 2009 We report on the synthesis and characterization of bis-cyclometalated iridium(III) complexes with 4-phenyl-1H-[1,2,3]triazole, synthesized via a “click”-chemistry approach, as a new type of cyclo- metalating ligand. The photophysical and electrochemical properties of these complexes are investigated experimentally as well as theoretically by using density functional theory. The properties of these new complexes are compared to their known 2-phenylpyridinato analogues. The emission of the herein described complexes is clearly influenced by the applied ancillary ligand and can be adjusted over a broad range of frequencies. The results indicate that the phenyl-1H-[1,2,3]triazole ligands in general cause a spectral blue shift. Introduction Organic light-emitting diodes (OLEDs) have received con- siderable attention during recent years in the acade- mic world and in industry for display and lighting applica- tions. 1-6 For the fabrication of high-efficiency OLEDs, the development of high-performance materials plays an impor- tant role. Iridium(III) complexes show, in contrast to com- plexes based on other heavy-metal atoms (e.g., Ru II , Rh I , Os II ), an intense phosphorescence at room temperature. 7 This emission originates from a triplet metal-to-ligand charge transfer (MLCT) or in some cases from a triplet ligand- centered (LC) state. Due to the strong spin-orbit coupling, the phosphorescent lifetimes are in the microsecond regime. Besides the advantage of obtaining an internal quantum efficiency of theoretically up to 100% in electroluminescent devices, 8 the emission color of iridium(III) complexes can easily be varied from blue to red by adapting the coordinated ligand system. Several strategies have been reported in order to tune the photophysical properties of these complexes and to achieve blue emission, e.g., employing electron-withdrawing substituents in the cyclometalating ligand 9 and using cat- ionic 10 as well as anionic Ir III complexes. 11 In recent years many different ligand systems were investigated in order to obtain phosphors with high quantum yields and color purity. In particular bis- and tris-cyclometalated iridium(III) com- plexes exhibit a high potential for applications in OLEDs. To form bis-cyclometalated species chloro-bridged dimeric iridium(III) precursors can be reacted with a broad variety of coordination motifs, e.g. bipyridine, picolinate, acetylace- tonate, and their derivatives. 12-17 Besides the straightforward synthesis, the utilization of ancillary ligands provides further options to introduce functionalities and to tune the optical and electrical properties. 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