Use of the template effect for the synthesis of new S, N, and O containing metal complexes /
The lack of examples of five-coordinate nickel in a mixed hard/soft (NIS) donor environment and the tendency for a spontaneous conversion from square planar, four-coordinate to octahedral, six-coordinate geometry in these cases has been suggested as a possible fundamental factor for substrate bindin...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=743273121&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The lack of examples of five-coordinate nickel in a mixed hard/soft (NIS) donor environment and the tendency for a spontaneous conversion from square planar, four-coordinate to octahedral, six-coordinate geometry in these cases has been suggested as a possible fundamental factor for substrate binding in nickel-containing enzymes. The NIII complexes discussed in this work have been synthesized in order to investigate the factors contributing to geometrical conversion. The variation in electrochemical properties as a result of coordination changes has also been examined. Addition of ring forming agents containing an additional ligating site to 1,5-bis(mercaptoethyl)-1,5-diazacyclooctane nickel(II), Ni-1, has proven to be a very effective method for generating macrocycles of increased denticity. The resulting Ni-1 derivatives, 8 - 16, have further established the geometrical preferences of Ni-I in a mixed hard/soft donor set. In addition, they have demonstrated the ease of conversion from fourto six-coordination through utilization of solvent effects. Cyclic voltammetry has been applied in conjunction with UV-vis spectroscopy and X-ray crystallography (structure analysis performed by Dr. Joseph Reibenspies at the Crystal & Molecular Structure Laboratory Center for Chemical Characterization and Analysis at Texas A&M University) to verify the correlation between geometry, donor set, and redox chemistry. Nickel(II) in a square planar, N2s,2 (S' = thioether) donor set exhibits a quasi-reversible to reversible NIIIII reduction; an irreversible oxidation event at 2.0 V more positive potential than the NiII/III reduction is also observed. In an octahedral environment, a quasi-reversible NiII/III oxidation is seen, and when observed, the NiII/I reduction event occurs at a more negative potential than the four-coordinate derivatives. Furthermore, if an 0 donor is axially ligated, the oxidation potential is more positive than if a N axial donor is present. |
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| Item Description: | Vita. "Major Subject: Chemistry". In title, symbols are used. |
| Physical Description: | xv, 121 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |