Kinetics teach that electronic coupling lowers the free-energy change that accompanies electron transfer
Abstract
Electron-transfer theories predict that an increase in the quantum-mechanical mixing (HDA) of electron donor and acceptor wavefunctions at the instant of electron transfer drives equilibrium constants toward unity. Kinetic and equilibrium studies of four acceptor–bridge–donor (A-B-D) compounds reported herein provide experimental validation of this prediction. Here, the compounds have two redox-active groups that differ only by the orientation of the aromatic bridge: a phenyl–thiophene bridge (p) that supports strong electronic coupling of HDA> 1,000 cm–1; and a xylyl–thiophene bridge (x) that prevents planarization and decreases HDA< 100 cm–1without a significant change in distance. Pulsed-light excitation allowed kinetic determination of the equilibrium constant, Keq. In agreement with theory, Keq(p) were closer to unity compared to Keq(x). A van’t Hoff analysis provided clear evidence of an adiabatic electron-transfer pathway for p-series and a nonadiabatic pathway for x-series. Collectively, the data show that the absolute magnitude of the thermodynamic driving force for electron transfers are decreased when adiabatic pathways are operative, a finding that should be taken into account in the design of hybrid materials for solar energy conversion.
- Authors:
-
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290,
- Department of Chemistry, Fudan University, 200433 Shanghai, People’s Republic of China,
- Department of Chemistry, The University of British Columbia, Vancouver, BC V6T 1Z1, Canada,, Department of Chemical &, Biological Engineering, The University of British Columbia, Vancouver, BC V6T 1Z1, Canada,, The Stewart Blusson Quantum Matter Institute, The University of British Columbia, Vancouver, BC V6T 1Z1, Canada
- Publication Date:
- Research Org.:
- Univ. of North Carolina, Chapel Hill, NC (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- OSTI Identifier:
- 1457096
- Alternate Identifier(s):
- OSTI ID: 1540281
- Grant/Contract Number:
- SC0013461
- Resource Type:
- Published Article
- Journal Name:
- Proceedings of the National Academy of Sciences of the United States of America
- Additional Journal Information:
- Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 115 Journal Issue: 28; Journal ID: ISSN 0027-8424
- Publisher:
- Proceedings of the National Academy of Sciences
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Science & Technology; Other Topics; electron transfer; electronic coupling; Gibbs free energy; equilibrium; solar energy
Citation Formats
Sampaio, Renato N., Piechota, Eric J., Troian-Gautier, Ludovic, Maurer, Andrew B., Hu, Ke, Schauer, Phil A., Blair, Amber D., Berlinguette, Curtis P., and Meyer, Gerald J. Kinetics teach that electronic coupling lowers the free-energy change that accompanies electron transfer. United States: N. p., 2018.
Web. doi:10.1073/pnas.1722401115.
Sampaio, Renato N., Piechota, Eric J., Troian-Gautier, Ludovic, Maurer, Andrew B., Hu, Ke, Schauer, Phil A., Blair, Amber D., Berlinguette, Curtis P., & Meyer, Gerald J. Kinetics teach that electronic coupling lowers the free-energy change that accompanies electron transfer. United States. https://doi.org/10.1073/pnas.1722401115
Sampaio, Renato N., Piechota, Eric J., Troian-Gautier, Ludovic, Maurer, Andrew B., Hu, Ke, Schauer, Phil A., Blair, Amber D., Berlinguette, Curtis P., and Meyer, Gerald J. Mon .
"Kinetics teach that electronic coupling lowers the free-energy change that accompanies electron transfer". United States. https://doi.org/10.1073/pnas.1722401115.
@article{osti_1457096,
title = {Kinetics teach that electronic coupling lowers the free-energy change that accompanies electron transfer},
author = {Sampaio, Renato N. and Piechota, Eric J. and Troian-Gautier, Ludovic and Maurer, Andrew B. and Hu, Ke and Schauer, Phil A. and Blair, Amber D. and Berlinguette, Curtis P. and Meyer, Gerald J.},
abstractNote = {Electron-transfer theories predict that an increase in the quantum-mechanical mixing (HDA) of electron donor and acceptor wavefunctions at the instant of electron transfer drives equilibrium constants toward unity. Kinetic and equilibrium studies of four acceptor–bridge–donor (A-B-D) compounds reported herein provide experimental validation of this prediction. Here, the compounds have two redox-active groups that differ only by the orientation of the aromatic bridge: a phenyl–thiophene bridge (p) that supports strong electronic coupling of HDA> 1,000 cm–1; and a xylyl–thiophene bridge (x) that prevents planarization and decreases HDA< 100 cm–1without a significant change in distance. Pulsed-light excitation allowed kinetic determination of the equilibrium constant, Keq. In agreement with theory, Keq(p) were closer to unity compared to Keq(x). A van’t Hoff analysis provided clear evidence of an adiabatic electron-transfer pathway for p-series and a nonadiabatic pathway for x-series. Collectively, the data show that the absolute magnitude of the thermodynamic driving force for electron transfers are decreased when adiabatic pathways are operative, a finding that should be taken into account in the design of hybrid materials for solar energy conversion.},
doi = {10.1073/pnas.1722401115},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 28,
volume = 115,
place = {United States},
year = {2018},
month = {6}
}
https://doi.org/10.1073/pnas.1722401115
Web of Science
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