Synthetic, structural, spectroscopic and computational studies of metal-dithiolates as models for pyranopterindithiolate molybdenum and tungsten enzymes: Dithiolate folding effect

Persistent Link:
http://hdl.handle.net/10150/280480
Title:
Synthetic, structural, spectroscopic and computational studies of metal-dithiolates as models for pyranopterindithiolate molybdenum and tungsten enzymes: Dithiolate folding effect
Author:
Joshi, Hemant K.
Issue Date:
2003
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:
Coordination by an axial oxo and an equatorial ene-dithiolate group is a salient feature of the active sites of the mononuclear pyranopterin Mo/W enzymes. Discrete mononuclear model complexes encompassing these features are important in understanding the metal-ligand interactions in these active sites. The compounds (Tp*)ME(S-S) (M = Mo, W; E = O, NO) and Cp₂M(S-S) (M = Ti, Mo, W) (where Tp* is hydrotris(3,5-dimethyl-1-pyrazolyl)borate, Cp is η⁵-cyclopentadienyl, S-S represents a generic ene-1,2-dithiolate ligand for example 1,2-benzenedithiolate and 3,6-dichloro-1,2-benzenedithiolate) provide access to three different electronic configurations of the metal, formally d¹, d² and d⁰, respectively. These compounds also allow the study of two metal, two axial ligand and two equatorial ene-dithiolate perturbations. X-ray crystallography, density functional theory and photoelectron spectroscopy are utilized to understand the metal-sulfur interaction in the above complexes. Subtle differences in the geometry of these compounds are observed, including the metal-dithiolate fold angle which is sensitive to the electronic occupation of the metal in-plane orbital. This orbital is presumably the "host" orbital to the electrons during catalysis. The work in this area has resulted in the development of a dithiolate-folding-effect. This effect relates to the experimental verification of the Lauher and Hoffmann bonding model for the metal-dithiolate interaction in these complexes. This "dithiolate-folding-effect" is proposed to account for the electronic buffering at the metal center. This effect may provide a regulatory mechanism for the metal-sulfur interactions and could be a factor in the electron transfer reactions that regenerate the active sites of molybdenum and tungsten enzymes. The structure and properties of these compounds are correlated with those of the enzyme active sites.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Chemistry, Biochemistry.; Chemistry, Inorganic.; Chemistry, Organic.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemistry
Degree Grantor:
University of Arizona
Advisor:
Enemark, John H.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleSynthetic, structural, spectroscopic and computational studies of metal-dithiolates as models for pyranopterindithiolate molybdenum and tungsten enzymes: Dithiolate folding effecten_US
dc.creatorJoshi, Hemant K.en_US
dc.contributor.authorJoshi, Hemant K.en_US
dc.date.issued2003en_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.abstractCoordination by an axial oxo and an equatorial ene-dithiolate group is a salient feature of the active sites of the mononuclear pyranopterin Mo/W enzymes. Discrete mononuclear model complexes encompassing these features are important in understanding the metal-ligand interactions in these active sites. The compounds (Tp*)ME(S-S) (M = Mo, W; E = O, NO) and Cp₂M(S-S) (M = Ti, Mo, W) (where Tp* is hydrotris(3,5-dimethyl-1-pyrazolyl)borate, Cp is η⁵-cyclopentadienyl, S-S represents a generic ene-1,2-dithiolate ligand for example 1,2-benzenedithiolate and 3,6-dichloro-1,2-benzenedithiolate) provide access to three different electronic configurations of the metal, formally d¹, d² and d⁰, respectively. These compounds also allow the study of two metal, two axial ligand and two equatorial ene-dithiolate perturbations. X-ray crystallography, density functional theory and photoelectron spectroscopy are utilized to understand the metal-sulfur interaction in the above complexes. Subtle differences in the geometry of these compounds are observed, including the metal-dithiolate fold angle which is sensitive to the electronic occupation of the metal in-plane orbital. This orbital is presumably the "host" orbital to the electrons during catalysis. The work in this area has resulted in the development of a dithiolate-folding-effect. This effect relates to the experimental verification of the Lauher and Hoffmann bonding model for the metal-dithiolate interaction in these complexes. This "dithiolate-folding-effect" is proposed to account for the electronic buffering at the metal center. This effect may provide a regulatory mechanism for the metal-sulfur interactions and could be a factor in the electron transfer reactions that regenerate the active sites of molybdenum and tungsten enzymes. The structure and properties of these compounds are correlated with those of the enzyme active sites.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectChemistry, Biochemistry.en_US
dc.subjectChemistry, Inorganic.en_US
dc.subjectChemistry, Organic.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorEnemark, John H.en_US
dc.identifier.proquest3119957en_US
dc.identifier.bibrecord.b45632091en_US
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