School of Chemistry - Theses

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    Synthesis of Myxobacteria Metabolites and Analogues and Development of Metal Complexes for the Mukaiyama Hydrogen Atom Transfer Reaction
    Ricca, Michael ( 2022)
    The spirangiens are a series of spiroketal containing polyketide natural products which are potently active against human and mouse cancer cell lines, and interleukin 8 expression. Oxidation at the C20 position occurs after polyketide synthesis is complete. Acyclic compounds lacking oxidation at the C20 position have been isolated, but never cyclic species; as such C20 deshydroxy spirangiens could be undiscovered natural products. This work saw the completion of the synthesis of a C20 deshydroxy derivative of spirangien M522, utilising a series of asymmetric aldol reactions to construct the polyketide backbone. A cross metathesis reaction followed by spirocyclisation forged the core, which was elaborated to by a Roush crotylation/Weix coupling sequence. Cell death, and cell growth inhibition assays in immortalised bone marrow derived macrophages (murine) and colon adenocarcinoma cells (murine), indicated that derivative retained its activity, and that C20 oxidation was not crucial for bioactivity. The Mukaiyama-Isayama hydration reaction hydrates a polar or non polar alkene to an alcohol via a C centred radical. Under Mn, Co or Fe catalysis, with phenylsilane in an alcoholic solvent, a metal hydride species forms which is able to facilitate hydrogen atom transfer (HAT) and generate the requisite radical. In the absence of oxygen alkene reduction occurs, and this also represents a major side product in the Mukaiyama hydration. In the presence of a Michael acceptor, the radical can undergo coupling, forging a new C-C bond. Three cis-beta octahedral complexes with a SALPN type ligand; Mn(SALPN)acac and Co(SALPN)acac were synthesised. These complexes were active in the Mukaiyama hydration of esters and ketones, and Fe(SALPN)acac successfully catalysed olefin coupling reactions. Compared to the control catalysts, the new complexes, showed superior reactivity (reduced side product formation, lower catalyst loading) or unusual reactivity (promotion of an acyloin rearrangement). Furthermore, the cobalt complex facilitated the synthesis of 7 acyloin natural products.
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    Synthesis and Modification of ZnSe Nanoplatelets
    Han, Jiho ( 2021)
    Nanoplatelets (NPLs) are a class of nanoparticles which have garnered significant interest in the research community. Unfortunately, much of the focus has been on the usual workhorse material: cadmium selenide. Zinc selenide is a close relative of cadmium selenide, both belonging to the II-VI family of semiconductors, but little research exists on ZnSe NPLs beyond its initial synthesis. In this thesis, ZnSe NPLs are addressed from the bottom up. In Chapter 2, the formation mechanism of ZnSe NPLs and MSCs is investigated. The evolution of nanoparticles in the reaction is monitored while exploring the reaction space. It is demonstrated that the concept of surface reversibility can be used to predict the formation of NPLs and MSCs. Additionally, it is found that MSCs and NPLs compete in the reaction, and selective formation can be induced by varying selenium precursor and the ripening behaviour of the ligand. Along the way, five unreported ZnSe magic-sized clusters (MSCs) are found. Chapter 3 of the thesis is a demonstration of Mn 2+ doping into the ZnSe and ZnS NPLs. Mn 2+dopant incorporation can be confirmed via its photoluminescence and photoluminescence excitation spectra and the photostability is measured. Additionally, the unique Mn 2+ emission is used a probe to investigate the evolution of various ZnSe species. Finally, Chapter 4 is concerned with the post-synthetic shelling of ZnSe nanoplatelets. ZnSe NPLs as synthesized from literature are colloidally and photo-unstable. A common solution to this is to coat the surface of the nanocrystal with a suitable semiconductor material. By modifying the process introduced for CdSe NPLs, the synthesized ZnSe NPLs are shelled successfully via colloidal atomic layer deposition (C-ALD). This allows us to improve its photoluminescence properties and observe unique features associated with Type-II ZnSe/CdS heterostructures.