Building model systems to understand Proton-Coupled Electron Transfer in heme : spectroscopic investigation of charge transfer to axially bound diimide acceptors
Name
846635240-MIT.pdf
Description
Full printable version
Size
11.05 MB
Format
Adobe PDF
Checksum (MD5)
32be9796b833f3f7cdd8943e27afe2f0
Author(s)
Hanson, Christina J
Advisor(s)
Daniel G. Nocera.
Alternative Title
Spectroscopic investigation of charge transfer to axially bound diimide acceptors
Date Issued
2013
Publisher
Massachusetts Institute of Technology
Abstract
Proton-Coupled Electron Transfer (PCET) is an important mechanistic motif in chemistry, which allows for efficient charge transport in many biological systems. We seek to understand how the proton and electron motions are coupled in a bidirectional system allowing for individual turning of the kinetics and thermodynamics. The target of interest is a biomimedic heme system allowing for a detailed mechanistic study of the formation of the oxidation states of heme, of particular interest the highly reactive Fe(IV)=O species. The bidirectional model is prepared using a hangman porphyrin with an axially coordinated to the metal center, and the electron transfer event is triggered by excitation of the porphyrin. The synthesis of this motif is discussed as well as initial studies into the binding of a coordinated electron acceptor to the metal center. In the future, the excited state of the acceptor will be used to trigger the electron transfer portion of the PCET event. To understand the signatures of different electron acceptors and binding to the metal center, a redox inactive zinc porphyrin is used as a model to allow for longer excited state lifetimes and well known transient signatures. Three diimide acceptors have been coordinated through a pyridine ring to the metal center of the porphyrin, and electron transfer was triggered both by excitation of the porphyrin and the acceptor. Lifetimes of the charge separated state were determined using picoseconds and nanosecond transient absorption. The acceptors are then coordinated to a symmetrical iron porphyrin in an attempt to understand the behavior of charge separation in the more complicated open d shell system. Spectroscopic data of both systems is shown.
Description
Thesis (S.M. in Inorganic Chemistry)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.
"February 2013." Vita. Cataloged from PDF version of thesis.
Includes bibliographical references.
Subjects
Chemistry.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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