The reactions between antimony(v) chloride and the monocyclopentadienyl metal trichlorides of Group 4 (CpMCl3 for M = Ti, Sr and Hf) in acetonitrile solution have afforded new hexachloroantimonate salts. These cationic metal-containing products have been isolated and characterised using IR, 1H NMR, elemental analysis, and in two cases, X-ray crystallography. The analogous pentamethylcyclopentadienyl (Cp*) systems have also been investigated, with largely similar results. Depending on the stoichiometry employed in the reaction, the relevant mono-, di- and tri-cationic complexes can be formed via halide exchange. For the Cp/Cp*TiCl3 series, a 1:1 or 2:1 ratio of Sb:Ti affords [CpTiCl2(MeCN)3][SbCl6] and [CpTiCl(MeCN)4][SbCl6]2 respectively. A ratio of 1:6 is required to yield pure [CpTi(MeCN)5][SbCl6]3. The 16-electron, pseudo-octahedral geometry of the latter complex was confirmed by X-ray analysis. A similar situation is found in the analogous Zr and Hf cases. However, the formation of the triply-charged complexes is accompanied by an expansion in coordination number about the metal centre; X-ray crystallographic studies revealed the 18-electron [CpZr(MeCN)6][SbCl6]3 to exhibit a pseudo-pentagonal bipyramidal geometry. The reactivity of the CpTi3+ salt towards a variety of both neutral and anionic species has been investigated. In acetonitrile solution, the complex rects with amines to give insoluble mixtures of partially substituted products. Adduct formation with ethers and trimethylphosphine is slow and only occurs when non-coordinating solvents are employed. The complex reacts with inorganic salts to reform neutral CpTiX3 compounds by simple anion exchange. The Ziegler-Natta catalytic activity of the cationic series has been studied. In the presence of methylaluminoxane cocatalysts, the complexes polymerise ethene but their activity is inversely proportional to the charge on the metal.

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Since the first reported use of carbon nanotubes (CNTs) as an electrode material in 1996 the use of CNTs within electrochemistry has grown rapidly. Single walled carbon nanotubes offer bio-compatibility combined with nano-scale dimensions and low background currents in the pristine state. Over the past decade the quantity of SWNTs synthesised globally has greatly increased making the material available for a variety of studies and potentially a feasible material for commercial electrodes. Despite this rise in popularity there is still an on going debate about the sites of electron transfer (ET) at a carbon nanotube. Some reports claim that the sidewall of the carbon nanotube exhibits sluggish ET rates with the majority of the ET occurring at defect sites and the end of the CNT. In contrast there is also evidence that suggests that ET at the sidewall is facile and not sluggish. The origin of ET is investigated using both theoretical and experimental data to probe the developing diffusion profiles to active ET sites. This is achieved on the timescale of a typical voltammetric experiment by significantly reducing the rate of diffusion to the electroactive sites using a NafionTM film. The reduced rate of diffusion allows the developing diffusion profiles to the individual sites to be decoupled. The use of convection and diffusion is a proven electrochemical technique to increase the sensitivity of analytical measurements and to probe reaction rates and mechanisms. The well-defined mass transport within a channel flow cell or an impinging jet electrode, combined with the continual replacement of solution, makes this geometry amenable to online studies, e.g. bedside or industrial monitoring, or a combination with chromatography. One draw back of conventional channel flow and impinging jet electrode set-ups is the need for specialist equipment or calibration steps each time the system is assembled. The use of microstereo lithography (MSL) to construct custom designed cells for use with a variety of planar electrodes is investigated. The hydrodynamics within the proposed designs are theoretically tested and verified experimentally. The devices constructed are easily assembled using a wide range of electrode materials and the computer aided manufacture provides flexibility in critical dimensions. Importantly, the devices only require a one-off determination of the height prior to assembly, removing the need for an electrochemical calibration step as the cells do not distort during assembly. Of particular interest for analytical studies is the greatly reduced background currents provided by a carbon nanotube network compared to an equivalent size carbon macroelectrode. The lower background signal allows small Faradaic currents to be observed experimentally, allowing lower concentrations to be distinguished. The enhanced sensitivity is combined with the increased mass transport of channel flow and impinging jet convective systems to determine the limit of detection for particular channel and impinging jet geometries under constant flow rates. This approach allows the successful detection of nano-molar concentrations under hydrodynamic control using standard voltammetric techniques.

Prodiginines are a large family of red-pigmented tripyrrole-based antibiotics. Their biosynthesis in Streptomyces coelicolor A3(2), by enzymes encoded in the red gene cluster, involves the condensation of 4-methoxy-2,2′-bipyrrole-5- carboxaldehyde (MBC) and 2-undecylpyrrole, catalysed by the RedH enzyme to give undecylprodiginine. This is followed by the mechanistically interesting oxidative carbocyclisation, catalysed by RedG to give streptorubin B. In this thesis prodiginine analogues have been generated by a mutasynthetic approach, in which chemically synthesised analogues of intermediates MBC and 2-undecylpyrrole were fed to mutant strains of S. coelicolor in which one of the genes required to biosynthesise MBC or 2-undecylpyrrole (redM or redL respectively) have been deleted. RedH and RedG have been shown to display relatively broad substrate tolerances and several analogues of both undecylprodiginine and streptorubin B have been generated by this approach. A variety of factors which are potentially limiting to substrate tolerances have been probed, including the steric size, alkyl chain hydrophobicity and introduction of π-electrons. The absolute stereochemistry of streptorubin B has been investigated by a mutasynthetic approach in which 2-undecylpyrrole, stereospecifically labelled with deuterium, is fed to a mutant strain of S. coelicolor unable to biosynthesise 2-undecylpyrrole. During the course of the investigation streptorubin B was analysed on a homochiral stationary phase HPLC and evidence of both ent- and dia-streptorubin B was discovered in the natural product isolated from S. coelicolor. When the position of the deuterium label from the mutasynthesis experiment was investigated by 1H-NMR and 2H-NMR the partial epimerization of the synthetic material became apparent. This made the definitive determination of the absolute stereochemistry of streptorubin B impossible. However, a tentative assignment of the absolute stereochemistry was possible. This was supported by comparison with the related natural products metacycloprodigiosin, the stereochemistry of which was established here by CD spectroscopy and chiral HPLC analyses, and roseophilin.

Two novel spectrophotometric assays have been developed for high throughput screening of microbial lignin degradation. The first assay involves fluorescently labelled lignin, which gives a time dependent increase in fluorescence with lignin degradation. The second involves nitrated lignin where an increase is seen at 430nm when lignin is broken down. These assays have allowed identification of a number of new strains of lignin degrading bacteria including R. jostii RHA1. They have also allowed the comparison of bacterial and fungal degraders and a study of lignin specificity. Bioinformatics has been used to identify two putative lignin degrading enzymes in R. jostii RHA1. Their role in lignin degradation was investigated by assaying of gene knockouts. This led to the detailed study of a new recombinant peroxidase, DypB, using lignin, lignocellulose and lignin dimer model substrates. This represents the first recombinant bacterial lignin degrading enzyme to be characterised. In addition methods for studying the products of lignin breakdown by HPLC, GC/MS and LC/MS have been developed. This has led to the identification of several low molecular weight aromatic products including ferulic acid. It has also been shown that the products released from lignin model compounds can be controlled by addition of the reductive enzyme diaphorase.

Poly(lactide)s is a biocompatible and biodegradable polymer available from renewable feed stocks and has therefore received a great deal of attention in recent years. Although significant research has been carried out examining its properties, architectural differences have received little attention. Notably, cyclic polymers are known to have strikingly different properties from their linear counterparts. This research will examine possible new routes for the synthesis of cyclic poly(lactide)s.

The four-membered cyclic hydrazine, 1,2-diazetidine, has received little attention from the scientific community. This system has useful potential applications in medicine and synthetic chemistry, but very few compounds of this class are known. This thesis describes the synthesis, structure and functionalisation chemistry of new simple 1,2- diazetidine derivatives. Synthetic studies show a Hard−Soft Acids and Bases controlled ring closure is necessary to effect acceptable to good yields in cyclisations to saturated N−carboxyalkyl and N−sulphonyl diazetidines. Functionalisation of these systems via C−H activation was unsuccessful due to protecting group participation. Synthetic studies toward the parent 1,2-diazetidine molecule (C2N2H6) using chloramine mediated N−N ring closure or deprotection strategies were also unsuccessful. Further studies show a wide range of simple 3-alkylidene-1,2-diazetidines and functionalised derivatives are accessible from commercial materials in two steps using an efficient Cu(I)-catalysed cyclisation. The scope of this cyclisation method is assessed. Pd(0)-catalysed Heck chemistry of 3-methylene-1,2-diazetidines allows a stereoselective route to arylated derivatives in moderate yields. Furthermore, diastereoselective reduction of these systems provides an efficient route to 1,2-diamines. Structural studies of a range of synthesised 1,2-diazetidines by X-ray crystallography and dynamic nuclear magnetic resonance spectroscopy are presented. Together these studies present the potential these molecules hold in synthetic chemistry.

This thesis describes our attempts towards realising new chemistry involving methyleneaziridines, for the main part, focusing on novel cycloaddition reactions involving this unique, densely functionalised heterocycle. Contrary to methyleneaziridines, the cycloaddition reactions of aziridines have been extensively studied. Thus, chapter one presents an introduction and literature review of cycloaddition reactions involving the aziridine nucleus, in order to contextualise the research described in chapter two. Chapter two describes the discovery and development of a novel Lewis acidpromoted (3+2) cycloaddition reaction of methyleneaziridines onto alkyne and alkene acceptors. Both inter- and intramolecular variants of this methodology were examined. The latter substrates being readily made by functionalisation of the parent methyleneaziridines through an efficient lithiation/alkylation sequence. These cycloadditions most likely proceed in a stepwise manner through opening of the methyleneaziridine by the nucleophilic alkene (or alkyne) and subsequent ring closure of the nitrogen atom onto the resultant carbocation. This chemistry provides a powerful new approach to a variety of heterocyclic systems including highly functionalised pyrroles and pyrrolidines. Chapter three begins with a brief introduction to multicomponent reactions, focusing on those which incorporate the methyleneaziridine nucleus. Our efforts towards realising new multicomponent reactions involving methyleneaziridines are detailed. Specifically, the attempted syntheses of 3,4-dihydro-1(2H)-isoquinolones, α-fluorinated and N-t-butylsulfinyl ketimines are described. Chapter four details the experimental procedure and characterisation data for the novel compounds produced in this thesis.

This work presents investigations into the use of the near-infrared (NIR) signals to interrogate, detect and image specific chemical compounds of interest in a security screening application, including when such compounds are hidden behind single layers of clothing fabric. In an initial set of experiments, the mechanisms governing the interaction of NIR signals with clothing fabrics and similar materials has been studied, in order to account for the influence of fabric layers when detecting hidden chemicals. Throughout the rest of the work, NIR spectroscopy has been used as a means to perform qualitative and quantitative analysis, in order to detect the presence of chemicals, and quantify the concentration in aqueous solution of liquids. It has been shown that, while the compounds can be identified on the basis of the characteristic features that appear in the relevant NIR spectra, the origin and nature of these spectra necessitate that such identification be performed with a chemometricsbased approach. Accordingly, multivariate calibration models based on neural networks and partial least squares regression (PLSR) have been developed to perform the requisite analyses. Results of calibration and testing with a range of data are reported. In order to facilitate operation in practical security screening, the development and testing of a software-based lock-in amplifier is reported, as a mean to enhance the signal-to-noise ratio (SNR) of the spectral data. It is shown that the amplifier can process up to 40 wavelength channels in parallel, to extract the spectral data buried in noise in each channel. Hence, with the SNR of the input signal set as low as -60 dB (by introducing software-generated additive white noise in the spectra), adequate noise suppression has been obtained, allowing the resulting spectral data to be used for requisite chemical detection. Finally, an integrated spectroscopic imaging application is developed to perform twodimensional cross-sectional scans of chemical samples, carry out lock-in amplification of the recorded intensity spectra, and plot the results of neural network-based chemical detection in the form of intensity images colour-coded to depict the presence of the pertinent chemicals at the scanned coordinates.

Verdazyl Radicals as Mediators in Living Radical Polymerisation: The aim of this work was to investigate verdazyl radicals as an alternative to nitroxides as mediators in stable free radical polymerisation. Verdazyl radicals and their unimolecular initiators were synthesised and utilised in the polymerisation of styrene and n-butyl acrylate. Varying degrees of success was observed in the polymerisations depending on the structure of the verdazyl radical. The polymerisation of methyl methacrylate and the copolymerisation of styrene and methyl methacrylate were also investigated. Correlations between observed molecular weight and theoretical molecular weight were poor but may be improved by optimisation of the reaction conditions. Electron paramagnetic resonance was used to elucidate the radical structure as well as to confirm the living nature of the polymerisation technique. Electron paramagnetic resonance was also utilised to provide an insight into radical stability and reactivity in the various reactions undertaken. Dopamine End-Functionalised Polymers for Application as Friction Modifiers: The aim of this work was to synthesise oil soluble dopamine end-functionalised polymers for mechanical testing to determine if the polymers can reduce friction by film formation at a surface. A dopamine based initiator was synthesised and used in Cu(I) and Cu(0) mediated polymerisations with little success and the dopamine catecholic end-group could not be identified as the polymer end-group. To enable a successful living polymerisation, the catechol groups on dopamine required protection. Complete deprotection of the catechol group can be achieved post polymerisation. The polymerisation of lauryl methacrylate was achieved using a polymerisation method designed for the long chain, non-polar molecule which utilised Cu(I)Cl. The polymerisations were scaled up to obtain a baseline, protected dopamine and deprotected dopamine polymers for mechanical testing. A reduction in friction and wear observed for the deprotected dopamine polymer, however, corrosion was also observed and may have affected the results.