Highly Efficient Red-Emitting Bis-Cyclometalated Iridium Complexes.

Bis-cyclometalated iridium complexes with enhanced phosphorescence quantum yields in the red region of the visible spectrum are described. Here, we demonstrate that incorporating strongly π-donating, nitrogen-containing β-ketoiminate (acNac), β-diketiminate (NacNac), and N, N'-diisopropylbenzamidinate (dipba) ancillary ligands can demonstrably perturb the excited-state kinetics, leading to enhanced photoluminescence quantum yields (Φ) for red-emitting compounds. A comprehensive study of the quantum yields and lifetimes for these complexes reveals that for the compounds with the highest quantum yields, the radiative rate constant ( k) is significantly higher than that of related complexes, and contributes substantially to the increase in Φ.