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dc.contributor.advisorDaniel G. Nocera.en_US
dc.contributor.authorHodgkiss, Justin M. (Justin Mark), 1978-en_US
dc.contributor.otherMassachusetts Institute of Technology. Dept. of Chemistry.en_US
dc.date.accessioned2007-08-29T19:07:27Z
dc.date.available2007-08-29T19:07:27Z
dc.date.copyright2006en_US
dc.date.issued2007en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/38539
dc.descriptionThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, February 2007.en_US
dc.descriptionThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.en_US
dc.descriptionVita.en_US
dc.descriptionIncludes bibliographical references.en_US
dc.description.abstractTime-resolved optical spectroscopy has been employed for mechanistic studies in model systems designed to undergo photo-induced proton-coupled electron transfer (PCET) and oxygen atom transfer (OAT) reactions, both of which are important to energy conversion chemistry (Chapter I). The effect of coupling proton transfer (PT) to electron transfer (ET) depends on their spatial configuration, thus model PCET systems must control both. Noncovalent amidinium-carboxylate PT interfaces are used assemble an electron D/A pairs (D = donor, A = acceptor), establishing uni-directional ET and PT coordinates. A highly conjugated porphyrin-amidinium derivative bears optical signatures that report on the structure of PT interfaces formed upon association with carboxylate acceptors (Chapter II). PT is supported within the interface and the mediating proton's position is sensitive to the peripheral electronic structure. Transient absorption (TA) spectroscopy is applied to a related porphyrin D---[H+]---A assembly, where ---[H+]--- = amidinecarboxylic acid (Chapter III). Specific probe wavelengths are targeted in order to amplify the optical signatures of PCET over those of competing quenching mechanisms.en_US
dc.description.abstract(cont.) The observed PCET rates are strongly attenuated compared with comparable covalentlybridged analogues, indicating that the PT interface reduces electronic coupling. Temperature-isotope dependence of the PCET rates reveals an unusual inverse isotope effect at low temperature, which is interpreted in a model of vibrationally-assisted PCET (chapter IV). Hangman porphyrin dyads have been developed to study bi-directional PCET in relation to oxygen activation. ET and PT coordinates are orthogonalized at fixed distances about a FeIII-OH center (Chapters V and VI). TA spectroscopy and electronic structure calculations reveal that the structural reorganization attendant to metal-centered PCET imposes a severe kinetic cost and alternative quenching pathways prevail. Finally, TA spectroscopy has been used to elucidate the mechanism of photocatalytic OAT for bridged diiron [mu]-oxo bisporphyrins (Chapter VII). The [mu]-oxo bond is photo-cleaved to generate a terminal iron(IV) oxo, which undergoes OAT to nucleophilic substrates. OAT rates are maximized when the bridge actively splays the porphyrin subunits apart to present the oxo before reclamping can occur.en_US
dc.description.statementofresponsibilityby Justin M. Hodgkiss.en_US
dc.format.extent266 p.en_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.relation.requiresCDROM contains entire thesis in .PDF format.en_US
dc.rightsM.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582
dc.subjectChemistry.en_US
dc.titleMechanistic studies of photo-induced proton-coupled electron transfer and oxygen atom transfer reactions in model systemsen_US
dc.title.alternativeMechanistic studies of PCET and OAT reactions in model systemsen_US
dc.typeThesisen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Dept. of Chemistry.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Chemistry
dc.identifier.oclc165119116en_US


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