Excited-State Engineering in Heteroleptic Ionic Iridium(III) Complexes

Area of Science:

• Coordination Chemistry
• Photophysics
• Materials Science

Background:

• Iridium(III) complexes exhibit unique photophysical properties due to the metal's characteristics and versatile ligand coordination.
• Compared to Fe(II) and Ru(II), Ir(III) complexes show greater stability and emissive potential, driven by a strong heavy-atom effect promoting intersystem crossing.
• The ability to incorporate diverse ligands, including cyclometalating (C^N) and ancillary types (N^N, C^N, C^C), allows for precise tuning of electronic and excited-state properties.

Purpose of the Study:

• To explore novel synthesis routes for cyclometalating and ancillary ligands for iridium(III) complexes.
• To investigate the impact of ligand modification and charge distribution on the stability and photophysical properties of iridium complexes.
• To develop new iridium(III) complexes with optimized electrochemical and excited-state characteristics for optoelectronic devices and photoredox catalysis.

Main Methods:

• Synthesis of novel cyclometalating ligands (carbene, mesoionic triazolylidene, tetrazolic systems) and ancillary ligands (isocyanides, carbenes, mesoionic triazolylidenes, bis-tetrazolic ligands).
• Preparation of cationic, neutral, and anionic iridium(III) complexes.
• Characterization through computational chemistry, synthetic chemistry, electrochemistry, and photochemistry.

Main Results:

• Development of new strategies for ligand modification, including charge relocation, to fine-tune complex properties.
• Identification of factors influencing complex stability and demonstration of how subtle structural changes impact photophysical behavior.
• Creation of blue-greenish emitters for optoelectronic applications and optimization of properties for promising photoredox catalysts.

Conclusions:

• Ligand design is a powerful strategy for 'excited-state engineering' in iridium(III) complexes.
• The study advances the preparation of custom iridium-based materials with tailored photophysical and electrochemical properties.
• These findings pave the way for new iridium(III) complexes with enhanced performance in catalysis and optoelectronics.