Proton-Coupled Electron Transfer in Artificial Photosynthetic Systems

Area of Science:

• Artificial Photosynthesis
• Bioinorganic Chemistry
• Photocatalysis

Background:

• Natural photosynthesis efficiently converts solar energy but is constrained by biological needs.
• Artificial photosynthetic constructs offer rational design for optimized solar energy conversion.
• Proton-coupled electron transfer (PCET) is crucial for energy conversion in biological and artificial systems.

Purpose of the Study:

• To investigate proton-coupled electron transfer (PCET) mechanisms in synthetic benzimidazole phenol (BIP) systems.
• To explore the design of artificial photosynthetic constructs for efficient solar energy conversion.
• To understand the relationship between proton transfer and redox potential in artificial systems.

Main Methods:

• Utilized covalently linked synthetic chromophores, electron donors/acceptors, and proton donors/acceptors.
• Employed electrochemical methods to study the oxidation of phenol in BIP systems.
• Conducted theoretical and experimental analyses of electron-proton transfer (EPT) and one-electron-two-proton transfer (E2PT) processes.

Main Results:

• Demonstrated that BIP systems can undergo PCET, including electron-proton transfer (EPT) and one-electron-two-proton transfer (E2PT).
• Observed E2PT involving proton translocation over ~7 Å via a Grotthuss-type mechanism in substituted BIP analogues.
• Found that E2PT in BIP analogues leads to a significant decrease in redox potential (~300 mV), limiting oxidizing power.

Conclusions:

• Artificial photosynthetic constructs, like BIP, enable the study of fundamental PCET processes.
• Maintaining high redox potential during multiple proton transfers is a key challenge for artificial photosynthesis.
• Controlling proton transfer dynamics is essential for developing efficient catalysts for electrolysis and fuel cells.