Photoinduced electron transfer in alpha-cyclodextrin-based supramolecular dyads: a free-energy-dependence study |
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Authors: | Balan Bijitha Gopidas Karical R |
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Affiliation: | Photosciences and Photonics Section, Chemical Sciences and Technology Division, Regional Research Laboratory (CSIR), Trivandrum--695019, India. |
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Abstract: | Photoinduced electron transfer (PET) between alpha-cyclodextrin-appended pyrene (PYCD) and a few acceptor molecules was studied in aqueous solutions. The pyrene moiety in PYCD is located above the narrower rim of the alpha-CD and is fully exposed to water. The acceptors are monocyclic organic molecules and, upon dissolution in water in the presence of PYCD, a fraction of the donor-acceptor systems is present as supramolecular dyads and the remaining fraction as free molecules. Free-energy-dependence studies showed that electron transfer in the supramolecular dyads follows the Marcus equation. The donor-acceptor coupling and the reorganization energy were determined from fits of the data to the Marcus equation. The electronic coupling was found to be similar to those reported for hydrogen-bonded systems. It appears that the actual lambdaout values are somewhat lower than values calculated with the continuum model. The experimental design has also allowed, for the first time, a visual demonstration of the inverted region on the basis of the raw fluorescence lifetime data. |
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Keywords: | cyclodextrins donor–acceptor systems electron transfer fluorescence quenching supramolecular dyads |
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