Iridium(III) cyclometalated complexes have attracted considerable attention due to their unique photophysical properties and their potential applications in organic light emitting diode (OLED) devices, photoelectrochemical solar cells, and phosphorescent probes in biological systems. Several classes of cyclometalated iridium complexes have been designed recently. Among all, heteroleptic Ir(C^N)<sub>2</sub>(LX) complexes, where (C^N) is a monoanionic cyclometalating ligand and (LX) is a monoanionic ancillary ligand, have been researched extensively in the past two decades.  However, the luminescence quantum yields in the yellow and red regions of the visible spectrum tend to be intrinsically low for common structure types in this class. In this work, ten new bis-cyclometalated iridium complexes have been synthesized in good yields and characterized by single-crystal X-ray diffraction, cyclic voltammetry, UV-vis absorption, and photoluminescence studies. We demonstrate that replacing the acetylacetone (acac) ancillary ligand with isoelectronic β-ketoiminate (acNac) and β-diketiminate (NacNac) ancillary ligands can perturb the excited-state kinetics, in many cases leading to an enhancement in the phosphorescence quantum yield relative to the corresponding acac analogues or the homoleptic tris-cyclometalated complexes.

Highly efficient yellow and red bis-cyclometalated iridium phosphors via ancillary ligand modification

255th National Meeting (2018)

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