Synthesis and characterization of phosphorescent platinum and iridium complexes with cyclometalated corannulene

Abstract

Synthesis, structural and characterization data are provided for Pt(II) and Ir(III) complexes cyclometalated with 2-(corannulene)pyridine (corpy), (corpy)Pt(dpm) and (corpy)Ir(ppz)2 (dpm = dipivaloylmethanato, ppz = 1-phenylpyrazolyl). A third compound, (phenpy)Ir(ppz)₂ (phenpy = 2-(5-phenanthryl)pyridyl), was also prepared to mimic the steric bulk of (corpy)Ir(ppz)₂. X-ray analysis reveals bowl depths of 0.895 Å for (corpy)Pt(dpm) and 0.837 Å in (corpy)Ir(ppz)₂. Neither complex displayed bowl-to-bowl stacking in the crystal lattice. A fluxional process for (corpy)Ir(ppz)₂ attributed to bowl inversion of corrannulene is observed in solution with a barrier (ΔG^‡ = 13 kcal mol⁻¹) and rate (k = 2.5 × 10³ s⁻¹) as determined using variable temperature ¹H NMR spectroscopy. All of the complexes display red phosphorescence at room temperature with quantum yields of 0.05 in solution and 0.2 in polymethyl methacrylate (PMMA).