Controlling Proton-Coupled Electron Transfer in Bioinspired Artificial Photosynthetic Relays

Emmanuel Odella, S. Jimena Mora, Brian L. Wadsworth, Mioy T. Huynh, Joshua J. Goings, Paul A. Liddell, Thomas L. Groy, Miguel Gervaldo, Leónides E. Sereno, John Devens Gust, Thomas A Moore, Gary F. Moore, Sharon Hammes-Schiffer, Ana L Moore

Research output: Contribution to journalArticle

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Abstract

Bioinspired constructs consisting of benzimidazole-phenol moieties bearing N-phenylimines as proton-accepting substituents have been designed to mimic the H-bond network associated with the TyrZ-His190 redox relay in photosystem II. These compounds provide a platform to theoretically and experimentally explore and expand proton-coupled electron transfer (PCET) processes. The models feature H-bonds between the phenol and the nitrogen at the 3-position of the benzimidazole and between the 1H-benzimidazole proton and the imine nitrogen. Protonation of the benzimidazole and the imine can be unambiguously detected by infrared spectroelectrochemistry (IRSEC) upon oxidation of the phenol. DFT calculations and IRSEC results demonstrate that with sufficiently strong electron-donating groups at the para-position of the N-phenylimine group (e.g., -OCH3 substitution), proton transfer to the imine is exergonic upon phenol oxidation, leading to a one-electron, two-proton (E2PT) product with the imidazole acting as a proton relay. When transfer of the second proton is not sufficiently exergonic (e.g., -CN substitution), a one-electron, one-proton transfer (EPT) product is dominant. Thus, the extent of proton translocation along the H-bond network, either ∼1.6 Å or ∼6.4 Å, can be controlled through imine substitution. Moreover, the H-bond strength between the benzimidazole NH and the imine nitrogen, which is a function of their relative pKa values, and the redox potential of the phenoxyl radical/phenol couple are linearly correlated with the Hammett constants of the substituents. In all cases, a high potential (∼1 V vs SCE) is observed for the phenoxyl radical/phenol couple. Designing and tuning redox-coupled proton wires is important for understanding bioenergetics and developing novel artificial photosynthetic systems.

Original languageEnglish
Pages (from-to)15450-15460
Number of pages11
JournalJournal of the American Chemical Society
Volume140
Issue number45
DOIs
Publication statusPublished - Nov 14 2018

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Protons
Phenol
Imines
Electrons
Phenols
Spectroelectrochemistry
Proton transfer
Substitution reactions
Nitrogen
Oxidation-Reduction
Bearings (structural)
Infrared radiation
Oxidation
Photosystem II Protein Complex
Protonation
Discrete Fourier transforms
Tuning
Energy Metabolism
benzimidazole
Wire

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Controlling Proton-Coupled Electron Transfer in Bioinspired Artificial Photosynthetic Relays. / Odella, Emmanuel; Mora, S. Jimena; Wadsworth, Brian L.; Huynh, Mioy T.; Goings, Joshua J.; Liddell, Paul A.; Groy, Thomas L.; Gervaldo, Miguel; Sereno, Leónides E.; Gust, John Devens; Moore, Thomas A; Moore, Gary F.; Hammes-Schiffer, Sharon; Moore, Ana L.

In: Journal of the American Chemical Society, Vol. 140, No. 45, 14.11.2018, p. 15450-15460.

Research output: Contribution to journalArticle

Odella, E, Mora, SJ, Wadsworth, BL, Huynh, MT, Goings, JJ, Liddell, PA, Groy, TL, Gervaldo, M, Sereno, LE, Gust, JD, Moore, TA, Moore, GF, Hammes-Schiffer, S & Moore, AL 2018, 'Controlling Proton-Coupled Electron Transfer in Bioinspired Artificial Photosynthetic Relays', Journal of the American Chemical Society, vol. 140, no. 45, pp. 15450-15460. https://doi.org/10.1021/jacs.8b09724
Odella, Emmanuel ; Mora, S. Jimena ; Wadsworth, Brian L. ; Huynh, Mioy T. ; Goings, Joshua J. ; Liddell, Paul A. ; Groy, Thomas L. ; Gervaldo, Miguel ; Sereno, Leónides E. ; Gust, John Devens ; Moore, Thomas A ; Moore, Gary F. ; Hammes-Schiffer, Sharon ; Moore, Ana L. / Controlling Proton-Coupled Electron Transfer in Bioinspired Artificial Photosynthetic Relays. In: Journal of the American Chemical Society. 2018 ; Vol. 140, No. 45. pp. 15450-15460.
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