Magnetic field-induced switching of the radical-pair intersystem crossing mechanism in a donor-bridge-acceptor molecule for artificial photosynthesis

Michael T. Colvin, Annie Butler Ricks, Amy M. Scott, Amanda L. Smeigh, Raanan Carmieli, Tomoaki Miura, Michael R Wasielewski

Research output: Contribution to journalArticle

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Abstract

A covalent, fixed-distance donor-bridge-acceptor (D-B-A) molecule was synthesized that upon photoexcitation undergoes ultrafast charge separation to yield a radical ion pair (RP) in which the spin-spin exchange interaction (2J) between the two radicals is sufficiently large to result in preferential RP intersystem crossing to the highest-energy RP eigenstate (T+1) at the 350 mT magnetic field characteristic of X-band (9.5 GHz) EPR spectroscopy. This behavior is unprecedented in covalent D-B-A molecules, and is evidenced by the time-resolved EPR (TREPR) spectrum at X-band of 3*D-B-A derived from RP recombination, which shows all six canonical EPR transitions polarized in emission (e,e,e,e,e,e). In contrast, when the RP is photogenerated in a 3400 mT magnetic field, the TREPR triplet spectrum at W-band (94 GHz) of 3*D-B-A displays the (a,e,e,a,a,e) polarization pattern characteristic of a weakly coupled RP precursor, similar to that observed in photosynthetic reaction center proteins, and indicates a switch to selective population of the lower-energy T0 eigenstate.

Original languageEnglish
Pages (from-to)1240-1243
Number of pages4
JournalJournal of the American Chemical Society
Volume133
Issue number5
DOIs
Publication statusPublished - Feb 9 2011

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Photosynthesis
Magnetic Fields
Ions
Magnetic fields
Molecules
Paramagnetic resonance
Photosynthetic Reaction Center Complex Proteins
Photoexcitation
Exchange interactions
Genetic Recombination
Spectrum Analysis
Switches
Spectroscopy
Polarization
Proteins
Population

ASJC Scopus subject areas

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

Cite this

Magnetic field-induced switching of the radical-pair intersystem crossing mechanism in a donor-bridge-acceptor molecule for artificial photosynthesis. / Colvin, Michael T.; Ricks, Annie Butler; Scott, Amy M.; Smeigh, Amanda L.; Carmieli, Raanan; Miura, Tomoaki; Wasielewski, Michael R.

In: Journal of the American Chemical Society, Vol. 133, No. 5, 09.02.2011, p. 1240-1243.

Research output: Contribution to journalArticle

Colvin, Michael T. ; Ricks, Annie Butler ; Scott, Amy M. ; Smeigh, Amanda L. ; Carmieli, Raanan ; Miura, Tomoaki ; Wasielewski, Michael R. / Magnetic field-induced switching of the radical-pair intersystem crossing mechanism in a donor-bridge-acceptor molecule for artificial photosynthesis. In: Journal of the American Chemical Society. 2011 ; Vol. 133, No. 5. pp. 1240-1243.
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abstract = "A covalent, fixed-distance donor-bridge-acceptor (D-B-A) molecule was synthesized that upon photoexcitation undergoes ultrafast charge separation to yield a radical ion pair (RP) in which the spin-spin exchange interaction (2J) between the two radicals is sufficiently large to result in preferential RP intersystem crossing to the highest-energy RP eigenstate (T+1) at the 350 mT magnetic field characteristic of X-band (9.5 GHz) EPR spectroscopy. This behavior is unprecedented in covalent D-B-A molecules, and is evidenced by the time-resolved EPR (TREPR) spectrum at X-band of 3*D-B-A derived from RP recombination, which shows all six canonical EPR transitions polarized in emission (e,e,e,e,e,e). In contrast, when the RP is photogenerated in a 3400 mT magnetic field, the TREPR triplet spectrum at W-band (94 GHz) of 3*D-B-A displays the (a,e,e,a,a,e) polarization pattern characteristic of a weakly coupled RP precursor, similar to that observed in photosynthetic reaction center proteins, and indicates a switch to selective population of the lower-energy T0 eigenstate.",
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