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dc.contributorWichita State University. Department of Chemistryen_US
dc.contributor.authorD'Souza, Francisen_US
dc.contributor.authorEl-Khouly, Mohamed E.en_US
dc.contributor.authorGadde, Sureshen_US
dc.contributor.authorMcCarty, Amy L.en_US
dc.contributor.authorKarr, Paul A.en_US
dc.contributor.authorZandler, Melvin E.en_US
dc.contributor.authorAraki, Yasuyakien_US
dc.contributor.authorIto, Osamuen_US
dc.identifierGM 59038en_US
dc.identifier.citationThe journal of physical chemistry. B. 2005 May 26; 109(20): 10107-14.en_US
dc.descriptionClick on the DOI link below to access the article (may not be free).en_US
dc.description.abstractSpectroscopic, redox, and electron transfer reactions of a self-assembled donor-acceptor dyad formed by axial coordination of magnesium meso-tetraphenylporphyrin (MgTPP) and fulleropyrrolidine appended with an imidazole coordinating ligand (C(60)Im) were investigated. Spectroscopic studies revealed the formation of a 1:1 C(60)Im:MgTPP supramolecular complex, and the anticipated 1:2 complex could not be observed because of the needed large amounts of the axial coordinating ligand. The formation constant, K(1), for the 1:1 complex was found to be (1.5 +/- 0.3) x 10(4) M(-1), suggesting fairly stable complex formation. The geometric and electronic structures of the dyads were probed by ab initio B3LYP/3-21G() methods. The majority of the highest occupied frontier molecular orbital (HOMO) was found to be located on the MgTPP entity, while the lowest unoccupied molecular orbital (LUMO) was on the fullerene entity, suggesting that the charge-separated state of the supramolecular complex is C(60)Im(*-):MgTPP(*+). Redox titrations involving MgTPP and C(60)Im allowed accurate determination of the oxidation and reduction potentials of the donor and acceptor entities in the supramolecular complex. These studies revealed more difficult oxidation, by about 100 mV, for MgTPP in the pentacoordinated C(60)Im:MgTPP compared to pristine MgTPP in o-dichlorobenzene. A total of six one-electron redox processes corresponding to the oxidation and reduction of the zinc porphyrin ring and the reduction of fullerene entities was observed within the accessible potential window of the solvent. The excited state events were monitored by both steady state and time-resolved emission as well as transient absorption techniques. In o-dichlorobenzene, upon coordination of C(60)Im to MgTPP, the main quenching pathway involved electron transfer from the singlet excited MgTPP to the C(60)Im moiety. The rate of forward electron transfer, k(CS), calculated from the picosecond time-resolved emission studies was found to be 1.1 x 10(10) s(-1) with a quantum yield, Phi(CS), of 0.99, indicating fast and efficient charge separation. The rate of charge recombination, k(CR), evaluated from nanosecond transient absorption studies, was found to be 8.3 x 10(7) s(-1). A comparison between k(CS) and k(CR) suggested an excellent opportunity to utilize the charge-separated state for further electron-mediating processes.en_US
dc.description.sponsorshipNIGMS NIH HHSen_US
dc.publisherAmerican Chemical Societyen_US
dc.relation.ispartofseriesThe journal of physical chemistry. Ben_US
dc.relation.ispartofseriesJ Phys Chem Ben_US
dc.subjectResearch Support, N.I.H., Extramuralen_US
dc.subjectResearch Support, Non-U.S. Gov'ten_US
dc.titleSelf-assembled via axial coordination magnesium porphyrin-imidazole appended fullerene dyad: spectroscopic, electrochemical, computational, and photochemical studiesen_US
dc.coverage.spacialUnited Statesen_US
dc.description.versionpeer revieweden_US
dc.rights.holderCopyright © 2005 American Chemical Societyen_US

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