Photo- and electroluminescence from deep-red- and near-infrared-phosphorescent tris-cyclometalated iridium(III) complexes bearing largely π-extended ligands

• Novel Ir(III) complexes bearing largely π-extended C^N ligands were prepared.
• Some of the present Ir(III) complexes exhibited PL from deep-red to near-IR regions.
• A PLED was fabricated, emitting from deep-red to near-IR regions with EQE of 1.41%.

Deep-red- and near-infrared-phosphorescent tris-cyclometalated iridium(III) complexes bearing largely π-extended cyclometalated (C^N) ligands were newly synthesized, and their photo- and electroluminescence properties were investigated. When 2-(benzo[b]furan-2-yl)quinoline and 2-(benzo[b]thiophen-2-yl)quinoline were employed as C^N ligands, deep-red photoluminescence was obtained (Ir-1a and Ir-1b; λPL in CH2Cl2, 647 and 652 nm, respectively). In the case of the isoquinoline analogues of Ir-1a and Ir-1b, emission maxima were further red-shifted, ranging from deep-red to near-infrared regions (Ir-2a and Ir-2b; λPL in CH2Cl2, 696 and 690 nm, respectively). Especially, Ir-2b showed an excellent photoluminescence quantum yield (ΦPL = 0.15), and a polymer light-emitting diode doped with Ir-2b exhibited deep-red–near-infrared electroluminescence with a high external quantum efficiency (λEL = 694 nm, ηext max = 1.41%).

We have developed novel tris-cyclometalated iridium(III) complexes emitting in the near-infrared (NIR) region. Especially, Ir-2b is very emissive for an NIR-phosphorescent material, the ΦPL of which is 0.15. A polymer light-emitting diode doped with Ir-2b has also exhibited NIR electroluminescence with a relatively high external quantum efficiency (ηext max = 1.41%). The graphical abstract shows the electroluminescence spectrum of the PLED, along with the structure of Ir-2b.Figure optionsDownload as PowerPoint slide