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An attractive strategy to improve the energy transfer properties of synthetic dye networks is to optimize the excitonic coupling between the dyes to increase energy transfer rates. To explore this possibility, we investigate the use of J-like cyanine dye dimers (Cy3 and Cy5 dimers) on DNA duplexes as energy transfer relays in molecular photonic wires. This approach is based on using the collective emission dipole of a J-dimer to enhance the FRET rate between the dimer relay and a remote acceptor dye. Experimentally, we find that in room temperature aqueous buffer conditions the dimer relay provided no benefit in energy transfer quantum yield relative to a simple monomer relay. Further investigation led us to determine that enhanced non-radiative relaxation, non-ideal dye orientation within the dimer, and unfavorable dye orientation between the dimer and the acceptor dye limit energy transfer through the dimer relay. We hypothesized that non-radiative relaxation was the largest factor, and demonstrated this by placing the sample in a viscous solvent or cooling the sample, which dramatically improved energy transfer through the J-like dimer relay. Similar to how the formation of DNA-templated J-like dimers has improved, the practical use of J-like dimers to optimize energy transfer quantum efficiency will require improvements in the ability to control orientation between dyes to reach its full potential.
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Geometry‐Independent Ultrafast Energy Transfer in Bioinspired Arrays Containing Electronically Coupled BODIPY Dimers as Energy Donors
Abstract In photosynthetic light‐harvesting complexes, strong interaction between chromophores enables efficient absorption of solar radiation and has been suggested to enable ultrafast energy funneling to the reaction center. To examine whether similar effects can be realized in synthetic systems, and to determine the mechanisms of energy transfer, we synthesized and characterized a series of bioinspired arrays containing strongly‐coupled BODIPY dimers as energy donors and chlorin derivatives as energy acceptors. The BODIPY dimers feature broad absorption in the range of 500–600 nm, complementing the chlorin absorption to provide absorption across the entire visible spectrum. Ultrafast (~10 ps) energy transfer was observed from photoexcited BODIPY dyads to chlorin subunits. Surprisingly, the energy‐transfer rate is nearly independent of the position where the BODIPY dimer is attached to the chlorin and of the type of connecting linker. In addition, the energy‐transfer rate from BODIPY dimers to chlorin is slower than the corresponding rate in arrays containing BODIPY monomers. The lower rate, corresponding to less efficient through‐bond transfer, is most likely due to weaker electronic coupling between the ground state of the chlorin acceptor and the delocalized electronic state of the BODIPY dimer, compared to the localized state of a BODIPY monomer.
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- Award ID(s):
- 1955318
- PAR ID:
- 10468091
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 29
- Issue:
- 58
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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