Characterization of metal sites. I. In molybdoenzymes and their model systems, and, II. On silver electrode surfaces
Sabel, Dawn M.
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https://hdl.handle.net/2142/20114
Description
Title
Characterization of metal sites. I. In molybdoenzymes and their model systems, and, II. On silver electrode surfaces
Author(s)
Sabel, Dawn M.
Issue Date
1993
Doctoral Committee Chair(s)
Gewirth, Andrew A.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Inorganic
Language
eng
Abstract
In part 1 of this thesis, the characterization of molybdenum complexes and some molybdoenzymes was made through the use of optical and magnetic circular dichroism (MCD) spectroscopy. MCD spectra were obtained for (MOCl$\sb4$) $\sp-$ (M = Cr, and Mo) and (WOCl$\sb4$(H$\sb2$O)) $\sp-$ compounds. All of the spectra display temperature and field dependence consistent with a paramagnetic ground state. The two lowest energy bands are assigned to the $d\sb{xy} \to d\sb{xz},d\sb{yz}$ and $d\sb{xy} \to d\sb{x\sp2-y\sp2}$ ligand field transitions. All of the compounds display vibronic structure on the $d\sb{xy} \to d\sb{xz},d\sb{yz}$ band arising from coupling with the totally symmetric M-O stretch. The third band is assigned to a b$\sb1$(Cl) to b$\sb2(d\sb{xy})$ charge transfer transition and at slightly higher energies are charge transfer transitions from orbitals with e symmetry to the half occupied $d\sb{xy}$ orbital.
MCD spectra were also obtained for (MoOBr$\sb4$(H$\sb2$O)) $\sp-,$ (MoO(SPh)$\sb4\rbrack\sp-$ and Rhodobacter sphaeroides dimethyl sulfoxide (DMSO) reductase. The latter two display charge transfer transitions at significantly lower energies than observed in the (MOCl$\sb4\rbrack\sp-$ complexes which is consistent with thiol coordination. The rich charge transfer region of the DMSO reductase spectrum appears consist with dithiolene linkage.
Part 2 of this thesis, metal surfaces have been characterized through the use of atomic force microscopy (AFM). The AFM was used to examine the interaction of anions with the Ag(111) electrode. It was found that perchlorate and chloride anions are not inert to the Ag(111) surface while sulfate ions do not perturb the system noticeably. In situ AFM images of underpotential deposition of Cd adlayers on Ag(111) were also collected. After the first deposition peak, the Cd forms a $(\surd3$ x $\surd3)$R30$\sp\circ$ adlattice. Deposition of a full monolayer of Cd followed by short polarization times induces the formation of a Cd/Ag alloy. Dissolution of Cd from this alloy is characterized by surface roughening and the formation of pits which diffuse across the surface.
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