Anion-complexation-induced stabilization of charge separation

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dc.contributor Wichita State University. Department of Chemistry en_US
dc.contributor.author D'Souza, Francis en_US
dc.contributor.author Subbaiyan, Navaneetha K. en_US
dc.contributor.author Xie, Yongshu en_US
dc.contributor.author Hill, Jonathan P. en_US
dc.contributor.author Ariga, Katsuhiko en_US
dc.contributor.author Ohkubo, Kei en_US
dc.contributor.author Fukuzumi, Shunichi en_US
dc.date.accessioned 2012-02-06T17:15:41Z
dc.date.available 2012-02-06T17:15:41Z
dc.date.issued 2009-11-11 en_US
dc.identifier 19886697 en_US
dc.identifier 7503056 en_US
dc.identifier.citation Journal of the American Chemical Society. 2009 Nov 11; 131(44): 16138-46. en_US
dc.identifier.issn 1520-5126 en_US
dc.identifier.issn 0002-7863 en_US
dc.identifier.uri http://dx.doi.org/10.1021/ja9048306 en_US
dc.identifier.uri http://hdl.handle.net/10057/4249
dc.description Click on the DOI link below to access the article (may not be free). en_US
dc.description.abstract A supramolecular oligochromophoric system possessing exclusive binding sites for both a guest electron acceptor and an anionic cofactor species is developed, and anion-binding-induced stabilization of the charge-separated (CS) state is demonstrated. Toward this, intramolecular and intermolecular photochemical processes of a supramolecular complex of a bis-porphyrinyl-substituted oxoporphyrinogen with a bis(4-pyridyl)-substituted fullerene were investigated by using femtosecond and nanosecond laser flash photolysis measurements. Transient absorption spectra of the supramolecular complex obtained by femtosecond laser flash photolysis indicate that efficient electron transfer occurs from the porphyrin moiety to the fullerene moiety, followed by faster back electron transfer to the ground state. Binding of several different anionic species at the pyrrole amine groups of an oxoporphyrinogen unit within the supramolecular complex was found to improve the rate of the photoinduced electron transfer due to the favorable structural change. The anion binding also improves persistence of the photoinduced CS state between the anion-bound oxoporphyrinogen and fullerene moieties, which is produced by intermolecular electron transfer from the triplet excited state of free porphyrin molecules to free fullerene molecules, as indicated by the nanosecond laser flash photolysis measurements. In the case of fluoride anion binding, anion-complexation-induced stabilization of charge separation gave a 90-fold elongation of the CS state lifetime from 163 ns to 14 micros. Complexation with other anions (acetate or dihydrogen phosphate) also resulted in stabilization of the CS state, whereas weakly bound perchlorate anions gave no improvement. Complexation of anions to the oxoporphyrinogen center lowers its oxidation potential by nearly 600 mV, creating an intermediate energy state for charge migration from the ZnP(*+) to the oxoporphyrinogen:anion complex. An increase in reorganizational energy of electron transfer combined with the decrease in charge recombination driving force caused by anion binding results in an increase in the lifetime of the CS state. en_US
dc.format.extent 16138-46 en_US
dc.language.iso eng en_US
dc.publisher American Chemical Society en_US
dc.relation.ispartofseries Journal of the American Chemical Society en_US
dc.relation.ispartofseries J. Am. Chem. Soc. en_US
dc.source NLM en_US
dc.title Anion-complexation-induced stabilization of charge separation en_US
dc.type Article en_US
dc.coverage.spacial United States en_US
dc.description.version peer reviewed en_US
dc.rights.holder Copyright © 2009 American Chemical Society en_US

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