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Title: Studies of transition metal thioether macrocyclic complexes
Author: Taylor, Anne
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1991
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Chapter 1: A general discussion of macrocyclic co-ordination chemistry is given, with particular emphasis on the biological and catalytic relevance of macrocyclic systems. Chapter 2: Reproducible high yield synthesis of [Au ([9]aneS3)2](PF6) and [Au([9]aneS3)2](BF4)2 have been established. [Au([9]aneS3)2]2+ undergoes a one-electron oxidation to Au(III) and an irreversible reduction to Au(I). The solution e.p.r. spectrum of [Au([9]aneS3)2]2+ shows an isotropic signal with hyperfine coupling to 197Au. The frozen glass e.p.r. spectrum depicts a complicated anisotropic signal. Attempted e.p.r. spectrum simulation suggested that the quadrupole and nuclear Zeeman interactions are significant in [Au([9]aneS3)2]2&43 , consistent with the 197Au Mossbauer data recorded for Au(II) complex. The stable Au(I) complex, [Au(PPh3)([9]aneS3)](PF6) was also prepared. Chapter 3: [Au([18]aneS6)[(PF6) was isolated and structurally characterised; [18]aneS6 binds the Au(I) centre in a [2+ 2] distorted tetrahedral co-ordination. This complex exhibits two quasi-reversible oxidations, which were assigned as being largely metal-based processes by e.p.r. spectroscopy. Electrogenerations of the Au(II) and Au(III) species were monitored by electronic absorption spectroscopy, which demonstrated the absence of any transient intermediates. The electron-transfer rate constant determined for the [Au([18]aneS6)]+ /2&43 couple indicates that a large stereochemical change accompanies the oxidation of Au(I) and Au(II). Direct synthesis of [Au([18]aneS6)](PF6)2 was carried out. The solution e.p.r. spectrum of [Au([18]aneS6)](PF6)2 in MeNO2, at 293K shows an isotropic signal; a complicated isotropic signal is observed at 77K. On the basis of e.p.r. and electronic absorption spectra the geometry of [Au([18]aneS6)]2+ was proposed to be distorted octahedral. Chapter 4: The Au(I) complex of [15]aneS5 was isolated. [Au([15]aneS5)](B(C6F5)4) and [Au(15]aneS5)](PF6) are both dimeric in the solid-state, with the Au(I) centres in [2+ 2] distorted tetrahedral stereochemistries and bound in an exocyclic manner between the two facial macrocycles. [Au([15]aneS5]2+ exhibits two solvent dependent quasi-reversible oxidations, which were assigned as largely metal-based processes. The electron-transfer rate constant, ks, for the first oxidation was determined. Electrogenerations of the Au(II) and Au(III) species were monitored using the O.T.E. technique. [Au([15]aneS5)](PF6)2 was synthesised and was found to be monomeric in solution. An isotropic e.p.r. spectrum was observed for [Au([15]aneS5)]2+ in MeNO2 solution. A solvent independent rhombic signal was recorded at 77K, the d9 centre is therefore in an unsymmetrical environment. The dimeric [Au([15]aneS5)]+ solid must either immediately dissociate on solvation or prior to or on oxidation to [Au([15]aneS5)]2+ .
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available