Proton-coupled electron transfer from a luminescent excited state

Area of Science:

• Photochemistry
• Supramolecular Chemistry
• Coordination Chemistry

Background:

• Luminescent metal complexes are crucial for sensing and photoredox catalysis.
• Understanding anion-receptor interactions is key to designing functional materials.
• Proton-coupled electron transfer (PCET) is a fundamental process in chemistry and biology.

Purpose of the Study:

• To investigate the supramolecular assembly between a cationic iridium complex and benzoate anions.
• To explore the photophysical consequences of adduct formation.
• To elucidate the mechanism of photoinduced proton-coupled electron transfer (PCET).

Main Methods:

• Synthesis and characterization of a luminescent cationic iridium complex featuring a 2,2'-biimidazole ligand.
• Crystallographic analysis to determine the structure of hydrogen-bonded 1:1 adducts with benzoate anions.
• Photophysical studies (absorption, emission, time-resolved spectroscopy) under varying conditions, including the presence of 3,5-dinitrobenzoate.

Main Results:

• The iridium complex successfully formed stable 1:1 hydrogen-bonded adducts with benzoate anions.
• Photoexcitation of the complex in the presence of 3,5-dinitrobenzoate initiated a distinct proton-coupled electron transfer (PCET) process.
• Spectroscopic data provided insights into the electronic changes accompanying the PCET event.

Conclusions:

• Cationic iridium complexes can effectively engage in hydrogen bonding with anions, forming well-defined supramolecular structures.
• The observed PCET is a photoinduced process, highlighting the potential of this system in light-driven chemical transformations.
• This work contributes to the development of novel luminescent probes and photocatalysts based on iridium complexes.