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11:55
In Vitro Reconstitution of Light-harvesting Complexes of Plants and Green Algae
Published on: October 10, 2014
Probing coherence in synthetic cyclic light-harvesting pigments
Jessica E Donehue1, Oleg P Varnavski, Robert Cemborski
1Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
Journal of the American Chemical Society
|March 10, 2011
Summary
Coherent states in cyclic thiophene oligomers decay rapidly, transitioning to incoherent hopping. Larger ring sizes enhance initial delocalization, mimicking natural light-harvesting systems.
Area of Science:
- Organic electronics
- Photophysics
- Spectroscopy
Background:
- π-extended cyclic thiophene oligomers are promising organic materials.
- Understanding exciton dynamics and coherence is crucial for material design.
Purpose of the Study:
- Investigate structure-function relationships in cyclic thiophenes.
- Examine coherence dynamics between chromophores in organic macrocycles.
Main Methods:
- Ultrafast time-resolved absorption spectroscopy
- Fluorescence upconversion
- Three-pulse photon echo experiments
- Phenomenological modeling
Main Results:
- Excitation reveals an initial delocalized state in cyclic thiophenes.
- Anisotropy decay indicates ultrafast delocalized state decay followed by incoherent hopping.
- Coherence, not Förster resonance energy transfer, dominates exciton transfer.
- Ring size influences initial peak shift, suggesting weaker bath coupling and stronger intramolecular interactions in larger rings.
Conclusions:
- Coherence plays a significant role in exciton dynamics within these systems.
- Increased ring size enhances initial delocalization, approaching natural light-harvesting system complexity.
- These findings inform the design of organic materials for efficient energy transfer.
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