The study of cyclometalated organometallic compounds as organic light-emitting diodes (OLEDs) is receiving much attention now.1 Cyclometalated iridium(III) complexes are often considered as the most promising family of triplet emitters for organic light-emitting diodes (OLEDs), due to their excellent phosphorescent quantum yield and the possibility to easily tune the color of emission from deep blue to red.2,3 The most commonly used cyclometalated ligands are based on 2-phenyl-pyridine (ppy). Simple variation of the substitution pattern with donor and acceptor groups allows the tuning of the photophysical properties of cyclometalated iridium complexes. Another approach is to directly modify the skeleton of the main ligand by using various heterocyclic rings instead of pyridine.4 Very recently, we reported an iridium complex without a fused benzene ring, acetylacetonato bis(1-methyl-2-phenylimidazole) iridium(III), hereafter labeled N9665, exhibits unique photophysical behavior as the lowest unoccupied molecular orbitals (LUMOs) of the main ligand and of the ancillary ligand are almost degenerate, which leads to broad photo- and electro-phosphorescence, which makes this dopant suitable for white organic light-emitting diode (WOLED) based on a single emitting center. To gain insight into this class of compounds, we prepared complexes related to N966, with various substitution patterns. More recently, increasing interest has been focused on cyclometalated organometallic compounds, which show excellent application in OLEDs and WOLEDs.  In this work a series of cationic cyclometalated iridium(III) complexes of the type [Ir(C^N)2(N-N)]PF6 (C^N = phenyl imidazoles; N-N = 2,2'-bipyridine and its derivatives) has been isolated and the structures of some complexeshave been determined by X-ray crystallography. Their properties have been further characterized spectroscopically (UV-vis and emission) and electrochemically in dichloromethane solutions.  All complexes display strong absorption bands in the UV region with a molar extinction coefficient between 50 000 and 60 000 L mol-1 cm-1. The results of our systematic investigations will be presented and discussed.

Phosphorescent cyclometalated iridium(III) complexes based on phenyl-imidazole and 2,2'-bipyridine ligands: Application to OLEDs

247th National Meeting (2014)

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