Feb, 2011
Magnetic Field-Induced Switching of the Radical-Pair Intersystem Crossing Mechanism in a Donor-Bridge-Acceptor Molecule for Artificial Photosynthesis
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
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- Volume
- 133
- Number
- 5
- First page
- 1240
- Last page
- 1243
- Language
- English
- Publishing type
- Research paper (scientific journal)
- DOI
- 10.1021/ja1094815
- Publisher
- AMER CHEMICAL SOC
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 T-0 eigenstate.
- Link information
- ID information
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- DOI : 10.1021/ja1094815
- ISSN : 0002-7863
- Web of Science ID : WOS:000287228500027