A Novel Light-Emitting Mixed-Ligand Iridium(III) Complex With a Polymeric Terpyridine-PEG Macroligand: Synthesis And Cha
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DD11.7.1
A Novel Light-Emitting Mixed-Ligand Iridium(III) Complex With a Polymeric Terpyridine-PEG Macroligand: Synthesis And Characterization Elisabeth Holder, Veronica Marin, Michael A. R. Meier, Dmitry Kozodaev and Ulrich S. Schubert* Laboratory of Macromolecular Chemistry and Nanoscience, Eindhoven University of Technology and Dutch Polymer Institute (DPI), P.O. Box 513, 5600 MB Eindhoven, The Netherlands
ABSTRACT The synthesis of mixed ligand orthometalated iridium(III) complexes as well as the characterization of their electro-optical properties is briefly illustrated. The cyclic voltammetry results exemplify an enhanced stability of the complex with a poly(ethylene glycol (PEG) side chain compared to the corresponding organometallic model material. Less degradation of the electrically active centers was found to occur on the electrode surface. Furthermore the morphology of thin films of the described polymeric material was investigated with respect to potential applications in thin film devices.
INTRODUCTION Recently iridium(III) complexes have become increasingly interesting due to their valuable electroluminescent properties as a result of their high-potential application in light-emitting devices. The importance of such light-emitting materials is based on their ability to change their emission color depending on the introduced ligand set and their relatively short phosphorescence lifetime. A further application possibility arises due to their phosphorescence-based emission. In light-emitting devices (LEDs), the compatibility of host materials with iridium(III) phosphors is of importance for the collection of all emissive (host and triplet emitter) excitones at the phosphors.[1] These properties make them ideal candidates for technological relevant developments where very high electron-to-light efficiencies are envisioned, e.g. in portable electronics. The charged iridium(III) complexes with applications in light-emitting electrochemical cells (LECs) are those based on chelating ligands, such as 2,2’-bipyridine and terpyridine. These materials can reveal color changes based on the introduced cyclometalating ligand set, as their neutral counterparts used in LEDs. Due to the relatively small bias window where these complexes do not decompose, the charged complexes are placed in polymer matrices in order to avoid the irreversible oxidation on the electrode surface.[2] In the present study we briefly show the synthesis and the optical and electrical characterization of a yellow light-emitting iridium(III) complex with a polymeric terpyridine-PEG macroligand. The detailed synthesis and characterization of the structures of the presented material can be found elsewhere.[3]
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EXPERIMENTAL DETAILS UV and emission spectra were recorded on a Perkin Elmer Lamda-45 and a Perkin Elmer LS50B Luminescence spectrometer, respectively (1 cm cuvettes, CH2Cl2). Electrochemical experiments were performed using an Autolab PGSTAT30 model potentiostat. A standard three-electrode configuration was used, with platinum-
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