Hybrid polyoxometalates: aromatics, asymmetrics and oligomers

Macdonell, Andrew (2015) Hybrid polyoxometalates: aromatics, asymmetrics and oligomers. PhD thesis, University of Glasgow.

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Abstract

ABSTRACT This thesis looks at the synthesis of hybrid polyoxometalates (POMs), a family of polyoxometalate compounds grafted to organic moieties. Focussing particularly on the Mn-Anderson hybrid, it looks at new ways of isolating and purifying them and at how the organic component can be used to alter their crystal structure or to link multiple Mn-Anderson cores together to form short oligomer chains. In the first section, two Mn-Anderson hybrids are prepared with large aromatic organic moieties, as a continuation of earlier work looking at how aromatic organic components can influence the structure of Mn-Anderson compounds in the solid state. The two compounds, one based on an anthracene moiety (three fused aromatic rings) and another based on a tetraphenylphthalic moiety (five linked aromatic rings), were both synthesised and crystals were grown of their tetrabutylammonium (TBA) salts. These crystal structures were then analysed and their structure thoroughly described and compared to previous aromatic Mn-Anderson aromatic hybrids. In the second section, a set of methods are presented for the preparation and isolation of asymmetric Mn-Anderson hybrids, where two different organic moieties are linked to the same POM core. These methods use high pressure liquid chromatography (HPLC) and normal liquid chromatography (LC) techniques to separate the mixtures of symmetric and asymmetric products which inevitably result from the synthesis of the asymmetric compounds, formed via both pre- and post-functionalisation techniques, so long as the two organic moieties have sufficiently different hydrophobicity. In order to by-pass the hydrophobicity requirement, a "Universal" asymmetric Mn-Anderson was developed with a free amine and an FMOC-protected amine. This allows for good separation and also gives a product which can be used to form more complex asymmetric compounds via post-functionalisation reaction without further LC purification, and an asymmetric compound with two hydrophilic substituents was synthesised to prove this strategy. All compounds were then fully analysed to confirm the purity of the asymmetric products. Also included is a means to remedy unwanted protonation of TBA Mn-Anderson salts. In the final section, the easy access to asymmetric Mn-Anderson hybrids provided by the previous project is exploited to produce a series of short-chain POM oligomers. A coupling strategy using alkyne and azide Mn-Anderson hybrids was developed, and a series of symmetric and asymmetric building blocks based on these functional groups were synthesised. These were then strategically combined to form a dimer and trimer of Mn-Anderson cores, which could then be further functionalised with alkyne groups and have an additional two Mn-Anderson units added, to give a tetramer and a pentamer. Methods were then developed to successfully purify these oligomers from the excess starting materials used to make them and the compounds analysed to confirm their identity. Size-exclusion HPLC and ion-mobility mass spectrometry (IM-MS) were then performed to gain more information about the structure of these compounds and how they arrange themselves in solution and in the gas-phase.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: Q Science > QD Chemistry
Colleges/Schools: College of Science and Engineering > School of Chemistry
Funder's Name: UNSPECIFIED
Supervisor's Name: Cronin, Prof. Leroy
Date of Award: 2015
Embargo Date: 21 May 2018
Depositing User: Mr Andrew Macdonell
Unique ID: glathesis:2015-6386
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 22 May 2015 15:17
Last Modified: 25 May 2015 13:37
URI: http://theses.gla.ac.uk/id/eprint/6386

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