Proton-Coupled Electron Transfer Drives Long-Range Proton Translocation in Bioinspired Systems

Area of Science:

• Bioinorganic Chemistry
• Catalysis
• Photosynthesis

Background:

• Proton-coupled electron transfer (PCET) is crucial for bioenergetics and catalysis, linking electron and proton transport.
• The length scales and thermodynamic impacts of proton transport in PCET remain incompletely understood.

Purpose of the Study:

• To design and investigate bioinspired molecules capable of long-range, reversible proton transport via PCET.
• To explore the thermodynamic consequences of proton translocation over extended distances.

Main Methods:

• Design and synthesis of novel benzimidazole-based molecules with phenol and cyclohexylimine units.
• Electrochemical oxidation and reduction to drive proton translocation.
• Infrared spectroscopy to monitor proton arrival and departure.

Main Results:

• Demonstrated reversible translocation of two, three, and four protons over distances up to ~16 Å using a Grotthuss-type mechanism.
• Confirmed proton movement via electrochemical potential switching and spectroscopic observation of an IR band at 1660 cm^-1.
• Provided theoretical and experimental insights into the length scales of PCET processes.

Conclusions:

• Developed bioinspired "proton wires" that mimic key aspects of biological PCET, such as in photosystem II.
• Established the feasibility of long-range proton transport in artificial systems.
• Findings have implications for designing artificial photosynthesis, proton pumps, and catalytic systems for water oxidation and reduction.