Cyclometalated iridium(III) complex containing indolinyl-based phenanthroline ligand: Synthesis, structure and photophysical properties

A heteroleptic cationic Ir(III) complex [(X)₂Ir(L)]⁺PF₆⁻ was designed and synthesized, where L = 2-(1,3,3-trimethylindolin-2-yl)oxazolo[4,5-f] [1,10]phenanthroline, X = 2-phenylpyridine (ppy). Its structural and photophysical properties have been systematically investigated via a series of spectroscopic methods. This complex exhibits ligand-localized ¹π,π* transitions below 350 nm, broad and structureless metal-to-ligand/ligand-to-ligand charge transfer (¹MLCT/¹LLCT) transitions between 350 and 450 nm, and spin-forbidden ³MLCT/³LLCT/³π,π* transitions above 450 nm. Upon excitation at its absorption maximum, the complex exhibits orange phosphorescence in solution. In addition, this complex exhibits strong excited-state absorption in the visible spectral region, good anti-photobleaching and electrochemical stability. Reverse saturable absorption (RSA) of this complex was demonstrated at 532 nm using 4.1 ns laser pulses, which would be useful for a rational design of nonlinear optical materials.