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Spectroscopic and electronic structure studies of bis-metallodithiolenes


Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/12884

Spectroscopic and electronic structure studies of bis-metallodithiolenes

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dc.contributor.author Mtei, Regina
dc.date.accessioned 2011-07-02T18:16:05Z
dc.date.available 2011-07-02T18:16:05Z
dc.date.issued 2011-07-02
dc.date.submitted May 2011
dc.identifier.uri http://hdl.handle.net/1928/12884
dc.description.abstract Dimethylsulfoxide reductase (DMSOR) enzyme family members catalyze oxygen atom transfer to or from organic or inorganic substrate and play important roles in the global cycles of sulfur and nitrogen, as well as the detoxification of arsenite. This enzyme has recently been subject of investigation due to its catalytic nature of oxygen atom transfer. This work reports on the electronic structure and reactivity properties of dimethylsulfoxide reductase enzyme studied using spectroscopic and computational methods. The spectroscopic methods included electronic absorption (EA), electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD) and resonance Raman rRaman). Here, we report full characterization of the DMSOR and DMSOR model compounds, MoO/S/Se(LCOOMe)2, MoO(LH/LO)2, MoS/Se(LPh)2, MoO(L2ipro/meth), MoO(SPh)2(Lipro), MoO(bdt)2 and WO/S(LPh)2- and the nature of their charge transfer transitions. The model compounds were studied in the (IV), (V) oxidation states. The electron withdrawing nature of LCOOMe, L2ipro/meth, LPh ligands have indicated the presence of a low energy intraligand charge transfer transition. Ligand field, metal to ligand charge transfer, ligand to metal charge transfer and intraligand charge transfer bands for these model compounds have been successfully assigned using both electronic absorption and rRaman spectroscopies for Mo(IV) compounds. EA and MCD spectroscopic methods enabled the assignment of Mo(V) compounds. The density functional theory calculations have supported our assignments. EPR spectroscopy revealed a rhombic g-tensor and axial A-tensors for Mo(V) compounds indicative of low symmetry coordination and a dxy redox orbital. Spin density calculations revealed that electron transfer is through unbent side of ene-dithiolene ligands for regeneration of Mo(VI) resting state in the catalytic cycle. In particular, for DMSO reductase enzyme, the electronic structure of a desoxo Mo(V) intermediate has been probed by EPR, electronic absorption and MCD spectroscopies. The EPR spectra revealed a rhombic g-tensor that indicated a low symmetry coordination for this intermediate. For the first time a rhombic 95,97Mo A-tensor has been determined, that indicated a dz2 redox orbital admixed with dxy/dx2-y2 type orbitals. In general, these methods have indicated that the geometry of Mo(V) intermediate is distorted trigonal prismatic. en_US
dc.language.iso en_US en_US
dc.subject DMSOR, AO Models, Raman, EPR, MCD, DFT en_US
dc.subject.lcsh Dimethyl sulfoxide--Structure-activity relationships.
dc.subject.lcsh Molybdenum enzymes--Structure-activity relationships.
dc.subject.lcsh Ligands--Analysis.
dc.subject.lcsh Charge transfer in biology.
dc.title Spectroscopic and electronic structure studies of bis-metallodithiolenes en_US
dc.type Dissertation en_US
dc.description.degree Chemistry en_US
dc.description.level Doctoral en_US
dc.description.department University of New Mexico. Dept. of Chemistry en_US
dc.description.advisor Kirk, Martin
dc.description.committee-member Keller, David
dc.description.committee-member Guo, Hua
dc.description.committee-member Feng, Changjian

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