Three Types of Charged‐Ligand‐Based Blue–Green to Near‐Infrared Emitting Iridium Complexes: Synthesis, Structures, and Organic Light‐Emitting Diode Application

Abstract The development of a class of simple‐structure‐based small molecule iridium complexes with adjustable color emission from blue to near‐infrared (NIR) remains a major challenge. A novel straightforward strategy toward a series of three types of charged ligand (0, −1, −2)‐based neutral iridium(III) complexes is described, as it can be easily obtained by efficient three‐step synthesis. All the complexes contain an unusual dianionic ligand (−2) biphenyl and show a great color variation from blue–green (465–503 nm) to NIR (688–706 nm) by controlling different neutral (0) and monoanionic (−1) ligands. Notably, all the NIR‐emitting iridium(III) complexes have excellent chemical and thermal stability, which makes them easy to sublimate and purify, and are eventually applied to organic light‐emitting diode device with a good external quantum efficiency of 2.5%, and low efficiency roll‐off and turn‐on voltage (3 V). This study opens an important avenue for the construction of novel phosphorescent iridium(III) complex materials with tunable properties featuring three types of charged ligands (0, −1, −2), thus providing new opportunities for their optoelectronic applications.