Redox and functional models of (NiFe) hydrogenases /
A redox and functional model study of [NiFe] hydrogenase has
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1997.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736580571&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | A redox and functional model study of [NiFe] hydrogenase has examined a series of bimetahics, polymetallics and macrocyclic complexes based on the metallation and alkylation, respectively, of the dithiolate complexes of [1,5-bis(mercapto-ethyl)-I,5diazacyclooctane]Ni(ED, (bme- daco)Ni, and [NN-(bis-2-methyl-2-mercaptopropane)-I,5- diazacyclooctane]Ni(H), (bme*-daco)Ni. Charge neutralization of the thiolate sulfurs by metaration can stabalize the NiI state as efficiently as methylation forming a thioether. The implication of these results for the heteromettalic active site of [NiFe]-hydrogenase as structured from Desu6rovibrio gigas (Volbeda, A., et al. Nature, 1995, 373, 580), the generality of the Ni(g-SR)2M hinge structure, and a possible explanation for the unusual redox potentials has been explored. Macrocyclic complexes derived from the template synthesis of the [(bmedaco)Ni and (bme*-daco)Ni with S to S linkers Of C2, II*Br2, C3, lll*Br2 , and C4, IV*Br2, were synthesized and fully characterized as square planar complex ions. 'Me reduced macrocycles show little tendency to react with carbon monoxide but the open chain ligand complex undergoes reversible binding of CO in CO-saturated solutions. The air sensitivity of sulfur-rich metauoenzymes such as the [NiFe] hydrogenase has provided both a challenge towards establishing a catalytic activity as well as a possible clue to the active site. 'Me reactivity of nickel sulfenates, and demonstrated redoxpromoted intermolecular oxygen transfer as a possible model of the reversible inactivation seen in the enzymatic systems is presented in chapter V of this dissertation. The (ii-oxo)diiron(IH) complexes of bme-daco and bme*-daco ligands present uncommon examples of well- characterized ii-oxo diiron(III) species in the pirsence of sulfur donors. Whereas the reaction of molecular oxygen with a solution of diiron(II) complex, [(bme*-daco)Fe]2, affords slow formation of the ii-oxo species, the presence of 02 in the reaction of fire ligand with the iron source, Fe(acac)3, gave much higher yields in shorter time. With the less sterically encumbered derivative, [(bmedaco)Fe]2, the only successful route to [(bme-daco)Fe]20 required single 0-atom sources such as 4-chloropyrdine N-oxide to be present during the preparation of the complex; attempted use of molecular 02 either during the synthesis or following isolation of the iron(H) dimer [(bme-daco)Fe]2 resulted in decomposition. |
|---|---|
| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xvii, 201 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 123-132. |