η1 -Arene Complexes as Intermediates in the Preparation of Molecular Phosphorescent Iridium(III) Complexes

Abstract

Molecular phosphorescent heteroleptic bis-tridentate iridium(III) emitters have been prepared via η¹ -arene intermediates. In the presence of 4.0 mol of AgOTf, the complex [(IrCl{κ³ -N,C,N-(pyC₆ HMe₂ py)})(μ-Cl)]₂ (1; pyC₆ H₂ Me₂ py=1,3-di(2-pyridyl)-4,6-dimethylbenzene) reacted with 9-(6-phenylpyridin-2-yl)-9H-carbazole (PhpyCzH) and 2-phenoxy-6-phenylpyridine (PhpyOPh) to give [Ir{κ³ -N,C,N-(pyC₆ HMe₂ py)}{κ³ -C,N,C'-(C₆ H₄ pyCzH)}]OTf (2) and [Ir{κ³ -N,C,N-(pyC₆ HMe₂ py)}{κ³ -C,N,C'-(C₆ H₄ pyOPh)}]OTf (3). The X-ray diffraction structures of 2 and 3 reveal that the carbazolyl and phenoxy substituents of the C,N,C' ligand coordinate to the metal center to form an η¹ -arene π bond. Treatment of 2 and 3 with KOtBu led to the deprotonation of the coordinated carbon atom of the η¹ -arene group to afford the molecular phosphorescent [5t+4t'] heteroleptic iridium(III) complexes [Ir{κ³ -N,C,N-(pyC₆ HMe₂ py)}{κ³ -C,N,C'-(C₆ H₄ pyCz)}] (4) and [Ir{κ³ -N,C,N-(pyC₆ HMe₂ py)}{κ³ -C,N,C'-(C₆ H₄ pyOC₆ H₄ )}] (5). These complexes are green emitters that display short lifetimes and high quantum yields of 0.73 (4) and 0.87 (5) in the solid state.

Keywords: C−H activation; arene ligands; heteroleptic complexes; iridium; luminescence; tridentate ligands.