Bis-oxazoline derivatives as ancillary ligands for bis-cyclometalated iridium complexes.

• Organometallic iridium complexes, (C^N) 2 Ir(BOX), are reported with chiral bis-oxazoline (BOX) ancillary ligands. • (C^N) 2 Ir(BOX) complexes display highly efficient phosphorescence across the visible spectrum. • Δ and Λ diastereomers with cyclometallated phenyl-pyridine ligands, (ppy) 2 Ir(BOX), complex were isolated and characterized. • Diastereomers have identical properties, except for circular dichroism (CD) and circularly polarized emission (CPL) spectra. • An unprecedented match/mismatch effect between ligand chirality and the CPL magnitude is observed in these diastereomers. Organometallic iridium complexes with two cyclometalated ligands (C^N) and one bis-oxazoline derived ancillary ligand (L^X), i.e. (C^N) 2 Ir(L^X), are reported. The C^N ligands are 1-phenylpyrazoline (ppz), 2-(4,6-difluorophenyl)pyridine (F 2 ppy), 2-phenylpyridine (ppy), 1-phenylisoquinoline (piq). The box ligand is (4S-+)-phenyl-α-[(4S)- phenyloxazolidin -2- ylidene ]-2-oxazoline-2-acetonitrile. The emission of these complexes span across the visible and into the near-ultraviolet region of the electromagnetic spectrum with moderate to high photoluminescence quantum yields (Φ PL = 0.45–1.0). These complexes were found to emit from a metal-ligand to ligand charge transfer (ML'LCT) state and have lifetimes (1.3–2.1 μs), radiative rates (105 s−1), and nonradiative rates (104–105 s−1) comparable to state-of-the-art iridium emitters. The (ppy) 2 Ir(BOX-CN) complexes were resolved into the Δ- and Λ- diastereomers using differences in their solubility and additionally characterized by x-ray crystallography, stability, and chiroptic studies. The high Φ PL of these isomers results in the best to date brightness for circularly polarized luminescence (CPL) from iridium complexes (7.0 M−1 cm−1), with dissymmetry factors of −0.57 × 10−3 and +1.9 × 10−3 for 3Δ and 3Λ , respectively. The significant difference in CPL magnitude between 3Δ and 3Λ likely arises from interligand interactions (edge-to-face arrangement versus strong π-π interaction) for the pendant phenyl ring of the BOX-CN ligand which differ for the two isomers. [ABSTRACT FROM AUTHOR]