Efficient near-UV emitters based on cationic bis-pincer iridium(III) carbene complexes

Area of Science:

• Organometallic Chemistry
• Photophysics
• Materials Science

Background:

• Cationic iridium(III) complexes are investigated for their luminescent properties.
• Bis-pincer carbene ligands offer unique structural and electronic characteristics.

Purpose of the Study:

• To synthesize and characterize novel cationic near-UV emitters based on bis-pincer Ir(III) carbene complexes.
• To investigate the photophysical properties in solution and solid states.
• To elucidate the electronic structure and excited states using computational methods.

Main Methods:

• Synthesis of iridium(III) bis-pincer carbene complexes.
• Photoluminescence spectroscopy in solution and solid state.
• Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations.

Main Results:

• Two cationic complexes, [Ir(nBu)(C(NHC)(Me)CC(NHC))2]X (X = I(-), PF6(-)), show high emission quantum yields in solution (384 nm, 406 nm).
• Solid-state emission at lower energy (500 nm) is observed, with intensity ratios dependent on counterion identity.
• DFT/TD-DFT calculations provide insights into electronic features and excited states.

Conclusions:

• The synthesized iridium(III) complexes are efficient near-UV emitters.
• Counterion effects significantly influence solid-state emission, likely due to aggregation-induced trapping sites.
• Further studies are needed to fully understand the solid-state emission mechanism.