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Proton-coupled electron transfer: a reaction chemist's view
1Department of Chemistry, University of Washington, Campus Box 351700, Seattle, Washington 98195-1700, USA. mayer@chem.washington.edu
Annual Review of Physical Chemistry
|May 1, 2004
Summary
Proton-coupled electron transfer (PCET) reactions, crucial in chemistry and biology, are often more favorable than stepwise processes. Marcus theory accurately predicts many PCET/hydrogen atom transfer rate constants, revealing insights into intrinsic barriers.
Area of Science:
- Physical Chemistry
- Biochemistry
- Chemical Kinetics
Background:
- Proton-coupled electron transfer (PCET) reactions are fundamental processes in various chemical and biological systems.
- PCET involves the simultaneous transfer of an electron and a proton, distinguishing it from sequential electron transfer (ET) and proton transfer (PT).
- Concerted PCET exhibits greater thermodynamic favorability compared to stepwise ET/PT pathways.
Purpose of the Study:
- To explore the energetics and kinetics of proton-coupled electron transfer reactions.
- To investigate the applicability of Marcus theory to PCET and hydrogen atom transfer (HAT) reactions.
- To analyze the intrinsic barriers associated with PCET in comparison to electron transfer.
Main Methods:
- Theoretical analysis of PCET reaction mechanisms.
- Application of Marcus cross-relation for predicting rate constants.
- Comparison of intrinsic barriers for PCET and ET based on self-exchange reactions.
Main Results:
- Concerted PCET is thermodynamically favored over stepwise ET/PT by at least 1 eV.
- Marcus cross-relation effectively predicts rate constants for many PCET and HAT reactions.
- Intrinsic barriers for PCET can be comparable to or exceed those for ET.
Conclusions:
- PCET reactions are a significant class of transformations with unique thermodynamic properties.
- Marcus theory provides a valuable framework for understanding PCET kinetics and barriers.
- Further theoretical investigations are needed to fully elucidate the properties of PCET reactions.