Potassium ion controlled switching of intra- to intermolecular electron transfer in crown ether appended free-base porphyrin-fullerene donor-acceptor systems

dc.contributorWichita State University. Department of Chemistryen_US
dc.contributor.authorD'Souza, Francisen_US
dc.contributor.authorChitta, Raghuen_US
dc.contributor.authorGadde, Sureshen_US
dc.contributor.authorZandler, Melvin E.en_US
dc.contributor.authorMcCarty, Amy L.en_US
dc.contributor.authorSandanayaka, Atula S. D.en_US
dc.contributor.authorAraki, Yasuyakien_US
dc.contributor.authorIto, Osamuen_US
dc.coverage.spacialUnited Statesen_US
dc.descriptionClick on the DOI link below to access the article (may not be free).en_US
dc.description.abstractPhotoinduced electron transfer in intramolecularly interacting free-base porphyrin bearing one or four 18-crown-6 ether units at different positions of the porphyrin macrocycle periphery and pristine fullerene was investigated in polar benzonitrile and nonpolar o-dichlorobenzene and toluene solvents. Owing to the presence of two modes of binding, stable dyads were obtained in which the binding constants, K, were found to range between 4.2 x 10(3) and 10.4 x 10(3) M(-1) from fluorescence quenching data depending upon the location and number of crown ether entities on the porphyrin macrocycle and the solvent. Computational studies using the B3LYP/3-21G() method were employed to arrive at the geometry and electronic structure of the intramolecular dyads. The energetics of the redox states of the dyads were established from cyclic voltammetric studies. Under the intramolecular conditions, both the steady-state and time-resolved emission studies revealed efficient quenching of the singlet excited free-base porphyrin in these dyads, and the measured rates of charge separation, k(CS), were found to be in the 10(8)-10(9) s(-1) range. Nanosecond transient absorption studies were performed to characterize the electron-transfer products and to evaluate the charge-recombination rates. Shifting of the electron-transfer pathway from the intra- to intermolecular route was achieved by complexing potassium ions to the crown ether cavity(ies) in benzonitrile. This cation complexation weakened the intramolecular interactions between fullerene and the crown ether appended free-base porphyrin supramolecules, and under these conditions, intermolecular type interactions were mainly observed. Reversible inter- to intramolecular electron transfer was also accomplished by extracting the potassium ions of the complex with the addition of 18-crown-6. The present study nicely demonstrates the application of supramolecular methodology to control the excited-state electron-transfer path in donor-acceptor dyads.en_US
dc.description.versionpeer revieweden_US
dc.identifier.citationThe journal of physical chemistry. A. 2006 Apr 6; 110(13): 4338-47.en_US
dc.publisherAmerican Chemical Societyen_US
dc.relation.ispartofseriesThe journal of physical chemistry. Aen_US
dc.relation.ispartofseriesJ Phys Chem Aen_US
dc.rights.holderCopyright © 2006 American Chemical Societyen_US
dc.subjectResearch Support, Non-U.S. Gov'ten_US
dc.subjectResearch Support, U.S. Gov't, Non-P.H.S.en_US
dc.subject.meshComputer Simulationen_US
dc.subject.meshCrown Ethers/chemistryen_US
dc.subject.meshModels, Molecularen_US
dc.subject.meshMolecular Structureen_US
dc.subject.meshSpectrometry, Fluorescenceen_US
dc.subject.meshStatic Electricityen_US
dc.titlePotassium ion controlled switching of intra- to intermolecular electron transfer in crown ether appended free-base porphyrin-fullerene donor-acceptor systemsen_US