Narrowband Near-Infrared Circularly Polarized Phosphorescence from Cyclometalated Iridium(III) Complexes via Chiral β-Diketone Perturbation

Developing near-infrared (NIR) emitters that simultaneously exhibit narrowband emission, high efficiency, and circularly polarized luminescence (CPL) remains a challenge for organic light-emitting diodes (OLEDs). Herein, we report two chiral cyclometalated iridium(III) complexes (R-Ir and S-Ir) by employing 1-(benzo[b]thiophen-2-yl)isoquinoline as the rigid cyclometalating ligand and chiral β-diketone derivatives as ancillary ligands. This “chiral perturbation” strategy preserves the narrow emission profile of the rigid framework while introducing chiroptical activity. Both complexes show NIR phosphorescence at ~702 nm with an exceptionally narrow full width at half-maximum of 40 nm, high photoluminescence quantum yields of ~30%, and short excited-state lifetimes of ~0.35 µs. Mirror-image circularly polarized luminescence signals are observed with a dissymmetry factor (|glum|) of ~2.2 × 10⁻3. Solution-processed NIR OLEDs incorporating these emitters achieve a maximum external quantum efficiency of 4.4%, together with circularly polarized electroluminescence (dissymmetry factor, |gEL| ~1.9 × 10⁻3). These results demonstrate that chiral β-diketone perturbation is a promising strategy to overcome the trade-off between narrowband NIR emission, high quantum yield, and chiroptical activity, opening new avenues for chiral NIR optoelectronic materials. Graphical Abstract