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Photoinduced Electron Transfer in α‐Cyclodextrin‐Based Supramolecular Dyads: A Free‐Energy‐Dependence Study
Author(s) -
Balan Bijitha,
Gopidas Karical R.
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501548
Subject(s) - supramolecular chemistry , pyrene , chemistry , cyclodextrin , moiety , electron transfer , acceptor , marcus theory , molecule , photochemistry , photoinduced electron transfer , aqueous solution , electron acceptor , computational chemistry , stereochemistry , kinetics , organic chemistry , reaction rate constant , physics , quantum mechanics , condensed matter physics
Photoinduced electron transfer (PET) between α‐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 α‐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 λ out 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.