In an effort of developing iridium(II) complexes with novel diimine ligands as nonlinear absorbers, a series of 2-aryl substituted oxazolo[4,5-f][1,10]phenanthrolines and their cationic iridium(III) complexes 1-11 were synthesized and characterized by 1H-NMR, HRMS, elemental analysis and X-ray crystallography. The photophysics of these complexes was systematically investigated via spectroscopic methods and time-dependent density functional theory (TDDFT). All complexes possessed strong ligand-localized 1π,π* absorption bands below 300 nm, and moderately intense 1π,π* / 1CT (charge transfer) absorption bands between 300 – 400 nm, as well as the very weak 1,3LLCT (ligand-to-ligand charge transfer) / 1,3MLCT (metal-to-ligand charge transfer) transitions at wavelengths beyond 400 nm. Most of these complexes showed intense room temperature phosphorescence both in solution and in solid state. Among them, the complex with a naphthyl substituent at the diimine ligand not only showed strong emission, but also exhibited a piezochromic effect. The nanosecond transient absorption study for these complexes in degassed CH3CN revealed that except for the two complexes that contains NO2 or NPh2 substituents the other complexes all exhibited moderate to strong excited-state absorption in the visible spectral region. Thus, all complexes exhibited moderate to strong reverse saturable absorption (RSA) at 532 nm for nanosecond laser pulses. The strength of RSA varied with the variation of the substituent at the diimine ligand. These results clearly demonstrate that it is feasible to tune the ground-state and excited-state properties of the Ir(III) complexes via the substituent at the diimine ligand.

Cationic iridium(III) complexes bearing 2-aryl substituted oxazolo[4,5-f][1,10]phenanthroline (N^N) ligands: Synthesis, crystal structure, photophysics and application for reverse saturable absorption

253rd National Meeting (2017)

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