Highly Quantum Efficient Phosphorescent Sky Blue Emitters Based on Diastereomeric Iridium(III) Complexes of Atropisomeric 5‑Aryl‑4H‑1,2,4-triazole Ligands

Homoleptic fac-IrIIIL3 complexes of 5-aryl-4H-1,2,4-triazole ligands are sky blue emitters. When unsymmetrically substituted, the triazole ligands exhibit atropisomerism, and upon cyclometalation to Ir­(III) a mixture of diastereomers is formed. We have isolated and structurally characterized all four possible diastereomers of the fac-IrIIIL3 complex formed upon cyclometalation of an atropisomeric 5-aryl-4H-1,2,4-triazole ligand onto Ir­(III). The phosphorescent blue emitting materials reported herein are among the most efficient to date, with quantum efficiencies above 95%.