Gas-phase Photoelectron Spectroscopy and Computational Studies of Metal-thiolate Interactions: Implications to Biological Electron Transfer

Persistent Link:
http://hdl.handle.net/10150/195569
Title:
Gas-phase Photoelectron Spectroscopy and Computational Studies of Metal-thiolate Interactions: Implications to Biological Electron Transfer
Author:
Cranswick, Matthew A
Issue Date:
2008
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The research outlined in this dissertation focuses on understanding the role of metal-sulfur interactions as applied to bioinorganic and organometallic systems. This metal-sulfur interaction is analyzed using both gas-phase photoelectron spectroscopy (PES) and density functional theory (DFT). Gas-phase photoelectron spectroscopy is the most direct probe of electronic structure and is used in these studies to probe the molecular orbital energy levels of these model compounds, giving rise to an understanding of the metal and sulfur orbital interactions and characters (i.e. is an orbital primarily metal or sulfur based). Using density functional theory, orbital energies, overlap, and characters can be calculated and complement the PES experiments allowing for a detailed understanding of the electronic structure. The first part of my dissertation explains the design and implementation of a dual source gas-phase ultraviolet/X-ray photoelectron spectrometer (UPS/XPS). This gas-phase UPS/XPS can be used to quantify the bonding/antibonding character of frontier molecular orbitals, with specific applications to metal-sulfur interactions, allowing for a thorough analysis of the metal-sulfur interaction. The second part of the dissertation explores using model complexes, of the type Cp₂V(dithiolate) (where Cp is cyclopentadienyl and dithiolate is 1,2-ethenedithiolate or 1,2-benzenedithiolate), along with PES and DFT calculations to investigate the role of the pyranopterindithiolate cofactor and the d¹ electron configuration in modulating the redox potential and electron transfer in the active sites of molybdenum enzymes. This study shows that the d¹ electronic configuration offers a low energy electron transfer pathway for the reoxidation of the active site molybdenum center. The third part of the dissertation explores the use of model compounds that specifically focus on iron-thiolate interactions in biological systems, and the effect of electronic energy matching and sterics on the oxidation potential of this interaction. This study has shown that the metal-sulfur interaction is sensitive to the orientation of the thiolate ligand, and that during oxidation an “electronic-buffering effect” makes assigning a formal oxidation state to the metal center almost meaningless. All of these studies illustrate how the thiolate ligand can modulate the electron density and oxidation potential of the metal-sulfur interaction and the implication of this interaction to biological electron transfer.
Type:
text; Electronic Dissertation
Keywords:
thiolate; molybdenum; iron; photoelectron; density functional
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Enemark, John H.; Lichtenberger, Dennis L.
Committee Chair:
Enemark, John H.; Lichtenberger, Dennis L.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleGas-phase Photoelectron Spectroscopy and Computational Studies of Metal-thiolate Interactions: Implications to Biological Electron Transferen_US
dc.creatorCranswick, Matthew Aen_US
dc.contributor.authorCranswick, Matthew Aen_US
dc.date.issued2008en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe research outlined in this dissertation focuses on understanding the role of metal-sulfur interactions as applied to bioinorganic and organometallic systems. This metal-sulfur interaction is analyzed using both gas-phase photoelectron spectroscopy (PES) and density functional theory (DFT). Gas-phase photoelectron spectroscopy is the most direct probe of electronic structure and is used in these studies to probe the molecular orbital energy levels of these model compounds, giving rise to an understanding of the metal and sulfur orbital interactions and characters (i.e. is an orbital primarily metal or sulfur based). Using density functional theory, orbital energies, overlap, and characters can be calculated and complement the PES experiments allowing for a detailed understanding of the electronic structure. The first part of my dissertation explains the design and implementation of a dual source gas-phase ultraviolet/X-ray photoelectron spectrometer (UPS/XPS). This gas-phase UPS/XPS can be used to quantify the bonding/antibonding character of frontier molecular orbitals, with specific applications to metal-sulfur interactions, allowing for a thorough analysis of the metal-sulfur interaction. The second part of the dissertation explores using model complexes, of the type Cp₂V(dithiolate) (where Cp is cyclopentadienyl and dithiolate is 1,2-ethenedithiolate or 1,2-benzenedithiolate), along with PES and DFT calculations to investigate the role of the pyranopterindithiolate cofactor and the d¹ electron configuration in modulating the redox potential and electron transfer in the active sites of molybdenum enzymes. This study shows that the d¹ electronic configuration offers a low energy electron transfer pathway for the reoxidation of the active site molybdenum center. The third part of the dissertation explores the use of model compounds that specifically focus on iron-thiolate interactions in biological systems, and the effect of electronic energy matching and sterics on the oxidation potential of this interaction. This study has shown that the metal-sulfur interaction is sensitive to the orientation of the thiolate ligand, and that during oxidation an “electronic-buffering effect” makes assigning a formal oxidation state to the metal center almost meaningless. All of these studies illustrate how the thiolate ligand can modulate the electron density and oxidation potential of the metal-sulfur interaction and the implication of this interaction to biological electron transfer.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectthiolateen_US
dc.subjectmolybdenumen_US
dc.subjectironen_US
dc.subjectphotoelectronen_US
dc.subjectdensity functionalen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorEnemark, John H.en_US
dc.contributor.advisorLichtenberger, Dennis L.en_US
dc.contributor.chairEnemark, John H.en_US
dc.contributor.chairLichtenberger, Dennis L.en_US
dc.contributor.committeememberEnemark, John H.en_US
dc.contributor.committeememberLichtenberger, Dennis L.en_US
dc.contributor.committeememberWalker, F. Annen_US
dc.contributor.committeememberGlass, Richard S.en_US
dc.contributor.committeememberEvans, Dennis H.en_US
dc.identifier.proquest2647en_US
dc.identifier.oclc659749648en_US
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