Highly Luminescent Mono‐ and Dinuclear Cationic Iridium(III) Complexes Containing Phenanthroline‐Based Ancillary Ligand

Abstract

A new family of mononuclear (1–2) and dinuclear (3–5) cationic iridium(III) complexes have been synthesized and fully characterized. These complexes contain 2‐(4‐(trifluoromethyl)phenyl)pyridine (cf3ppy, L1) and 1‐(4‐(trifluoromethyl)phenyl)isoquinoline (cf3piq, L2) as cyclometalating ligands, 1,10‐phenanthroline (LX‐1) as the ancillary ligand and 1,4‐bis(1‐phenyl‐1H‐imidazo[4,5‐f][1,10]phenanthrolin‐2‐yl)benzene (biphen, LX‐2) as the bridging ligand. The crystal structure of LX‐2 has been determined by X‐ray analysis. All of the complexes are green‐red emissive with quantum yields of 16.6–93.5 % and lifetimes of 1.66–2.89 µs in solution at room temperature. Density functional theory (DFT) calculations have been carried out to gain insight into the nature of the low‐lying transitions and also to rationalize the electrochemical and photophysical properties. These research results reveal that the π‐conjugation system of C^N ligands and the diiridium system with conjugated bridging ligand are both benefical for the red‐shift of the absorption and emission spectra.