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Engineering opposite electronic polarization of singlet and triplet states increases the yield of high-energy photoproducts.

Publication ,  Journal Article
Polizzi, NF; Jiang, T; Beratan, DN; Therien, MJ
Published in: Proceedings of the National Academy of Sciences of the United States of America
July 2019

Efficient photosynthetic energy conversion requires quantitative, light-driven formation of high-energy, charge-separated states. However, energies of high-lying excited states are rarely extracted, in part because the congested density of states in the excited-state manifold leads to rapid deactivation. Conventional photosystem designs promote electron transfer (ET) by polarizing excited donor electron density toward the acceptor ("one-way" ET), a form of positive design. Curiously, negative design strategies that explicitly avoid unwanted side reactions have been underexplored. We report here that electronic polarization of a molecular chromophore can be used as both a positive and negative design element in a light-driven reaction. Intriguingly, prudent engineering of polarized excited states can steer a "U-turn" ET-where the excited electron density of the donor is initially pushed away from the acceptor-to outcompete a conventional one-way ET scheme. We directly compare one-way vs. U-turn ET strategies via a linked donor-acceptor (DA) assembly in which selective optical excitation produces donor excited states polarized either toward or away from the acceptor. Ultrafast spectroscopy of DA pinpoints the importance of realizing donor singlet and triplet excited states that have opposite electronic polarizations to shut down intersystem crossing. These results demonstrate that oppositely polarized electronically excited states can be employed to steer photoexcited states toward useful, high-energy products by routing these excited states away from states that are photosynthetic dead ends.

Duke Scholars

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Published In

Proceedings of the National Academy of Sciences of the United States of America

DOI

EISSN

1091-6490

ISSN

0027-8424

Publication Date

July 2019

Volume

116

Issue

29

Start / End Page

14465 / 14470

Related Subject Headings

  • Spectrum Analysis
  • Solar Energy
  • Rhodobacter sphaeroides
  • Photosynthesis
  • Models, Molecular
  • Energy Transfer
  • Electron Transport
  • Bioengineering
 

Citation

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Polizzi, N. F., Jiang, T., Beratan, D. N., & Therien, M. J. (2019). Engineering opposite electronic polarization of singlet and triplet states increases the yield of high-energy photoproducts. Proceedings of the National Academy of Sciences of the United States of America, 116(29), 14465–14470. https://doi.org/10.1073/pnas.1901752116
Polizzi, Nicholas F., Ting Jiang, David N. Beratan, and Michael J. Therien. “Engineering opposite electronic polarization of singlet and triplet states increases the yield of high-energy photoproducts.Proceedings of the National Academy of Sciences of the United States of America 116, no. 29 (July 2019): 14465–70. https://doi.org/10.1073/pnas.1901752116.
Polizzi NF, Jiang T, Beratan DN, Therien MJ. Engineering opposite electronic polarization of singlet and triplet states increases the yield of high-energy photoproducts. Proceedings of the National Academy of Sciences of the United States of America. 2019 Jul;116(29):14465–70.
Polizzi, Nicholas F., et al. “Engineering opposite electronic polarization of singlet and triplet states increases the yield of high-energy photoproducts.Proceedings of the National Academy of Sciences of the United States of America, vol. 116, no. 29, July 2019, pp. 14465–70. Epmc, doi:10.1073/pnas.1901752116.
Polizzi NF, Jiang T, Beratan DN, Therien MJ. Engineering opposite electronic polarization of singlet and triplet states increases the yield of high-energy photoproducts. Proceedings of the National Academy of Sciences of the United States of America. 2019 Jul;116(29):14465–14470.
Journal cover image

Published In

Proceedings of the National Academy of Sciences of the United States of America

DOI

EISSN

1091-6490

ISSN

0027-8424

Publication Date

July 2019

Volume

116

Issue

29

Start / End Page

14465 / 14470

Related Subject Headings

  • Spectrum Analysis
  • Solar Energy
  • Rhodobacter sphaeroides
  • Photosynthesis
  • Models, Molecular
  • Energy Transfer
  • Electron Transport
  • Bioengineering