Tipping the Balance between Concerted versus Sequential Proton-Coupled Electron Transfer
Abstract
We use quantized molecular dynamics simulations to investigate the competition between concerted and sequential proton-coupled electron-transfer (PCET) reaction mechanisms in inorganic catalysts. By analyzing reactive nonadiabatic PCET trajectories and computing both concerted and sequential rate constants, we characterize various molecular features that govern inorganic PCET reactions, including the solvent polarity, ligand-mediated electron–proton interactions, and intrinsic proton-transfer (PT) energy barrier. Using atomistic simulations with over 1200 atoms, we find that the symmetric iron biimidazoline system is extremely biased toward the concerted mechanism because of the strong ligand-mediated electron–proton interaction and the short PT distance. However, by investigating system-bath models in which electron–proton interactions are shielded, which are representative of ruthenium terpyridylbenzoates and iron (tetraphenylporphyrin)benzoates, we predict that a crossover between the concerted and sequential PCET mechanisms may be possible either by increasing the polarity of the solvent or by increasing the intrinsic PT energy barrier. In addition, we predict the possibility of a crossover in the PCET mechanism by directly varying the strength of the ligand-mediated electron–proton interactions. The results presented here reveal new strategies for altering the competition between the competing PCET mechanisms and design principles for controlling PCET in catalytic systems.
Additional Information
© 2015 American Chemical Society. Received: August 10, 2015; Publication Date (Web): October 6, 2015. This work was supported by the National Science Foundation (NSF) CAREER Award under Grant CHE-1057112 and the U.S. Department of Energy under Grant DE-SC0006598. Additionally, J.S.K. acknowledges support from an NSF Graduate Research Fellowship under Grant DGE-1144469, and T.F.M. acknowledges support from a Camille and Henry Dreyfus Foundation New Faculty Award and an Alfred P. Sloan Foundation Research Fellowship. Computing resources were provided by the National Energy Research Scientific Computing Center and the ASCR Leadership Computing Challenge Program. The authors declare no competing financial interest.Attached Files
Supplemental Material - ic5b01821_si_001.pdf
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Additional details
- Eprint ID
- 60982
- DOI
- 10.1021/acs.inorgchem.5b01821
- Resolver ID
- CaltechAUTHORS:20151012-133008507
- CHE-1057112
- NSF
- DE-SC0006598
- Department of Energy (DOE)
- DGE-1144469
- NSF Graduate Research Fellowship
- Camille and Henry Dreyfus Foundation
- Alfred P. Sloan Foundation
- Created
-
2015-10-15Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field