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This thesis discusses the synthesis and characterisation of ansa bridged permethylindenyl phenoxy (PHENI*) complexes and their applications in the synthesis of polyolefins. Efficient homogeneous and slurry phase catalyst systems are developed for the homopolymerisation of ethylene and propylene, and a range of copolymerisations incorporating linear α olefins. A brief review of polyolefin materials, their synthesis and properties is presented, focussing on how the varied properties makes them suitable for a range of societally relevant applications. Traditional solid state catalysts are contrasted with state of the art molecular catalysts which offer exceptional control over polymer molecular weight and composition, enabling the production of novel materials while maintaining optimal catalytic efficiency. Constrained geometry and phenoxy-imine catalysts are highlighted as examples which offer outstanding performance and tunability for ethylene polymerisation and copolymerisations. The synthesis and detailed characterisation of PHENI* complexes is developed using a high yielding adaptable procedure from low cost starting materials. A variety of metal centres, ansa bridge substituents, ancillary ligands, and phenoxide substitutions are presented with the influence of steric and electronic factors on structure, bonding, and reactivity explored. Structural trends are identified which help to rationalise the excellent catalytic performance of these complexes. The heterogenisation of PHENI* complexes on a range of solid supports is also discussed. The homopolymerisation of ethylene and propylene using homogeneous and immobilised PHENI* catalysts was studied, with the effects of the ligand, support, and reaction conditions investigated extensively. Exceptional catalytic activities are reported under mild conditions for the synthesis of substantially disentangled ultra high molecular weight polyethylene, and a novel elastomeric ultra high molecular weight atactic polypropylene. Supported PHENI* catalysts were finally investigated as a polyolefin platform technology, able to copolymerise a wide range of monomers efficiently. In all cases, random copolymers were produced in a monomer agnostic fashion, with the composition determined simply by the concentration of monomers. This enables a significant degree of predictability and control, enabling the synthesis of designer copolymers through programmed synthesis.

This thesis explores the design, synthesis, optoelectronic properties, and photocatalytic testing of copper(I) complexes with a two- or three-coordinate geometry bearing N-heterocyclic carbene ligands. Our design strategies aim to avoid the failings of four-coordinate copper(I) complexes which are prone to Jahn-Teller distortion in the excited state. The first chapter provides an overview of the fundamental photophysical properties of transition metal complexes and an introduction to bimolecular energy and electron transfer processes. A mini-review of Earth-abundant photocatalysts is presented. Special attention will then be devoted to describing the design principles of copper(I) based photocatalysts (PCs). We begin by describing the photophysical and electrochemical properties of four-coordinate copper(I) complexes, followed by the design and applications of copper(I) complexes as PCs. Next, we provide a summary of the development of two- and three-coordinate copper(I) complexes, describing their photophysical properties and applications. Chapter 2 describes the synthesis, characterisation and optoelectronic properties of seven three-coordinate copper(I) N-heterocyclic carbene (NHC) complexes bearing N^N ligands, of the form of [Cu(IPr)(N^N)]PF₆ (where IPr is 1,3-Bis(2,6-diisopropylphenyl)imidazolium, and N^N is phen = 1,10-phenanthroline, bpy = 2,2'-bipyridine, dpa = 2,2'-dipyridylamine, mdpa = N-methyl-2,2'-dipyridylamine, dpym = di(pyridin-2-yl)methane, phdpym = 2,2'-(phenylmethylene)dipyridine, fludpym = 2,2'-(9H-fluorene-9,9-diyl)dipyridine). Six complexes underwent successful preliminary photocatalytic testing in two mechanistically distinct photocatalysis reactions: an Atom Transfer Radical Addition (ATRA) photoinduced electron transfer (PET) reaction between an alkyl halide and an alkene; and photoinduced energy transfer (PEnT) reaction of a vinyl azide to a vinyl nitrene, which subsequently rearranges to form a pyrrole. The complex [Cu(IPr)(phen)]PF₆ performed best in the ATRA reaction (77% NMR yield) out of six complexes tested, while complex [Cu(IPr)(phdpym)]PF₆ performed best in the PEnT reaction (59% NMR yield vs 66% obtained with [Cu(dmp)(BINAP)]BF₄). Chapter 3 reports the synthesis, characterisation and optoelectronic properties of a series of three-coordinate copper(I) NHC complexes bearing a dpa ligand, of the form [Cu(NHC)(dpa)]PF₆. Three complexes underwent preliminary photocatalytic testing, however their performance as PCs was poor. Chapter 4 reports the first example of a neutral linear two-coordinate Cu(I) complex Cu(IPrBIAN)(Cz) bearing an IPrBIAN NHC ligand, and after investigation of its optoelectronic properties, it was successfully applied as a PC in a proof-of-concept PET ATRA reaction (52% NMR yield). Cu(IPrBIAN)(Cz) also exhibited interesting dual emission properties in solution; this is seen as separate emission depending on excitation source for most solvents, and is especially strong in chloroform solution. The synthesis, characterisation, and optoelectronic properties of further derivatives of this complex bearing 3,6-substituted carbazolate ligands were also investigated. The final conclusions chapter summarises the results of each chapter and brings focus to the overarching aims and themes of the thesis. This chapter identifies key areas for future work in the field of two- and three-coordinate copper(I) complexes as photocatalysts, specifically the need to improve PC stability, investigate reaction mechanisms, and correlate structure-property relationships with photocatalytic performance. A need for standardisation of photocatalysis reaction set-ups is identified as a requirement for reproducibility of results within the field of photocatalysis.

CO₂ reduction has drawn much attention globally in the development of new processes and technology for avoiding the impact of serious climate change. On the other hand, the fossil fuel as energy resources cannot be easily replaced in order to greatly reduce CO₂ emission. CO₂ utilisation has been widely investigated in many manufacture/industries areas. This chemical conversion of CO₂ is not only adding value to the process of CO₂ reduction but also has economic and environmental benefits. Using CO₂ as a feedstock in the synthesis of high-demand chemicals in modern chemical industry would have a high economic value. However, due to the stability of CO₂, a highly effective heterogeneous catalyst is required in order to provide pathways to the synthesis of important chemicals in this way. In this work, CrOx-based catalysts supported on ZrO₂ have been developed and investigated for the dehydrogenation of propane using CO₂ with various metal oxides (Zn, Mn, Ca) as promoters. In addition, a different catalyst preparation method the "one-pot synthesis" has been used to develop a more effective catalyst than those in which the metal is added to a support in a conventional way. Another exciting part of the work is the regeneration process of deactivated catalysts for recovering their catalytic ability, thus extending their catalytic lifetime. Based on this work, we show that the one-pot catalysts provide different catalyst surface morphologies, structures, and catalytic properties as compared to the conventional impregnation catalysts. The dominated ZrO₂ species changed from monoclinic phase in the impregnation catalysts to tetragonal phase in one-pot catalysts. It also reveals a more uniform and highly dispersed catalytically CrOx active phase in which the CrOx species can be involved in the reaction more effectively than the corresponding impregnated catalysts. In addition, one-pot catalyst showed an increase amount of the active Cr(VI) species. The introduction of a CaO promoter, the catalyst shows different surface acidity and basicity. In addition, the 2Cr/Ca-ZrO₂ shows an increase in both the overall propane conversion and propylene selectivity. The CaO promoter helps the process to reach 18% of propane conversion with 20% propylene yield and keep for 4-5 hours during the process. After the process, the propane conversion reduces to 10%, 15% product yield but with still about 93% propylene selectivity. Moreover, it also reduces the level of detrimental carbon deposition on the catalyst particles leading to enhanced stability and performance. In addition, the regeneration process can recover the catalytic ability for a continuous CO₂-PDH process which shows the good potential for the long-term stable performance of the one-pot catalysts. The development of novel catalytic system for CO₂-PDH make this process more attractive and effective not only in reducing net CO₂ emission by using it to produce useful chemical products but also by helping reach the demand for these (propylene in this case). The work suggests that further development of catalysts for this and similar processes is desirable.

This thesis explores the synthesis of and subsequent use of monometallic lanthanide complexes and their reductive potential for selected biomarkers. Attempts on a bimetallic complex are also reported. Chapter 1 outlines the properties of lanthanides with a focus on their photophysical and chemical behaviour, and the kinetic requirements for complexes containing lanthanides. Medical applications and discussions on the key reductive biomarkers to this thesis are also discussed. Chapter 2 explores the use of anthracene as a functional chromophore in a DO3A-based lanthanide complex, and the synthetic protocol and characterisation of these complexes by NMR, luminescence, and UV. Interaction of these complexes with singlet oxygen and irradiative stimuli is focused on in detail. Chapter 3 discusses attempts on synthesis of a bimetallic lanthanide complex based on the anthryl-functionalised DO3A complexes discussed in Chapter 2. Chapter 4 investigates synthesis and characterisation of benzoazide-functionalised DO3A lanthanide complexes. Studies on their reduction potential are undertaken using two biomarkers, and the difference in reactivity is briefly discussed. Chapter 5 reports synthesis and characterisation of DO3A lanthanide-containing complexes functionalised with nitrobenzene. Investigations into the reduction potential of these complexes to a previously chosen reductant are undertaken and discussed. Chapter 6 discusses the conclusions reached during the course of this work, and suggests possible avenues for future research. Chapter 7 contains experimental techniques for processing data, and procedures for synthesis and characterisation of these complexes.

This thesis reports on investigations into fluoroborate compounds with a view to their application in 18F-PET tracer design. The principle aim was to understand how advances could be made to the functionalisation of fluoroborate compounds for bioconjugation, in addition to improving their hydrolytic stability and optimising synthesis via efficient fluoride uptake routes. Chapter 3 reports on investigations into the synthesis and fluoride binding capabilities of 1,8-bis(boryl)-naphthalene scaffolds featuring boronic acid and ester functional groups. These bidentate "ligands" were investigated for potential thermodynamic enhancement that may be attained by chelating fluoride in such a structure, and the opportunity this offered for hydrolytically robust fluoride complexes. The diboronic acid system is established to be incompatible for this application due to the formation of an exceptionally robust intramolecular anhydride that effectively blocks the binding pocket. An unsymmetrical framework featuring a single boronic ester group is demonstrated to be suitable for chelation, although fluoride binding was subsequently compromised by a thermodynamically driven, functional group rearrangement that positions fluoride in a more labile terminal position, with a B-O-B bridge again being generated. Chapter 4 explores how highly robust N-heterocyclic carbene boron trifluoride adducts may be diversified to facilitate a range of methods for bioconjugation. The modular design of N-heterocyclic carbenes is exploited in this endeavour. Thus, a series of adducts has been synthesised featuring systematic variation of the carbene backbone, and the impact on their hydrolytic stability assessed. The preparation of a N-alkyne appended NHC-BF3 derivatives is also described, and their bioconjugation to a folic acid derivative detailed. Chapter 5 describes the investigation of carbene stabilised boron complexes and their fluoride binding reactions. Three-coordinate carbene-stabilised catecholato-boreniums have been investigated together with related series of four-coordinate complexes featuring either an additional anionic or neutral donor group. Systematic variation of the carbene donor and the leaving group substituent have been used to tune the rate of fluoride binding by these complexes, in addition to their hydrolytic stability. Neutral and cationic boron complexes are thus explored, with the four-coordinate boronium cations being determined to offer the greatest scope for optimising reactivity and stability. Careful choice of the secondary donor (based on pKa) offers a workable compromise between the kinetics of fluoride uptake at 60 °C and the stability of the boronium precursor to hydrolysis. Thus, systematic optimisation allows rapid, promoter-free fluoride binding to be achieved with a bench-stable boronium complex.

This thesis describes the synthesis of heterobimetallic complexes which contain an unsupported bond between a group 13 and a group 11 metal (Cu, Ag, Au). While the primary focus is on bonds to aluminium, which are lesser known, the analogous gallium-coinage metal compounds are also investigated as a point of comparison. The methodology used in this work makes use of the first of a new class of nucleophilic aluminium 'aluminyl' anions, K2[(NON)Al]2 (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene), which is reacted with group 11 electrophiles of the form R3PMI (R = Ph, tBu, Cy) in a salt metathesis reaction. This approach gives access to rich structural variety, producing bimetallic complexes of the form (NON)AlMPtBu3, a 2:1 di(aluminyl)cuprate system, K[Cu{Al(NON)}2], and trimetallic iodide bridged complexes, (NON)Al(MPPh3)2I. These compounds are characterised by X-ray crystallography and multinuclear NMR, with spectroscopic comparisons to the heavier congeners (prepared using the gallyl reagent K2[(NON)Ga]2 giving insight into the properties of the aluminyl fragment as a metalloligand. The reactivity of the linear (NON)AlMPtBu3 series towards small molecules is then explored. The compounds in this bimetallic series readily insert carbon based electrophiles (CO2, carbodiimides) into the Al-M bond to give a complexes containing an M(CE2)Al bridging unit (E = O, NR), with an unusual μ-κ1(C):κ2(E,E') binding mode. While the carbodiimide insertion products are stable to further reaction, it is observed that the CO2 bridged species have the potential to react onwards, and that this ability depends on the identity of the group 11 metal. (NON)Al(O2C)AuPtBu3 is inert to further reaction, while (NON)Al(O2C)AgPtBu3 reacts slowly with a second equivalent of CO2 to give a bridging carbonate complex and CO. Copper compound (NON)AlCuPtBu3 reacts rapidly even at very low temperatures, proceeding straight to the carbonate complex. The mechanism of this CO2 to CO transformation can be investigated and is found to be consistent with rate determining extrusion of CO to form a bridging Al-O-M oxide, followed by uptake of a second molecule of CO2. The behaviour of the Al-M bond towards alkynes is then investigated. Internal alkynes insert into the Al-Cu bond of (NON)AlCuPtBu3, giving (aluminylalkenyl)copper compounds with M-C bonds of differing natures. The insertion gives access to both syn and anti dimetallated alkenes, depending on the reaction conditions. It is also regioselective, producing only one regioisomer when unsymmetrically substituted alkynes are used. The mechanism of the insertion, and a subsequent isomerisation step, are investigated through kinetics studies. The differential reactivity of the (aluminylalkenyl)copper compounds is exploited by selective functionalisation with CO, which inserts only into the Cu-C bond. This results in formation of the first structurally characterised example of a copper acyl complex, a feat made possible by cooperative action of copper and the proximal aluminium centre. In all, this thesis aims to demonstrate the utility of the potassium aluminyl reagent K2[(NON)Al]2 as a means to forming direct Al-M bonds, and investigate the reactivity of such heterobimetallic compounds towards challenging small molecules.

Chronic inflammation is prevalent in society with a wide range of inflammatory diseases, such as rheumatoid arthritis and inflammatory bowel disease, as well as association with cancer, strokes, and neurodegenerative conditions. Due to the complexity in the inflammatory pathways and a lack of understanding of those processes, there are limited therapeutic options available that aim to resolve the causes of inflammation, with most treatments instead aiming to manage symptoms. More bespoke imaging agents are required to help advance our understanding of the fundamental processes governing these disease states. To overcome current imaging limitations such as quantification, correlation, depth penetration and resolution quality, this work takes a multimodal molecular imaging approach to study one type of immune cells, macrophages, that are of particular importance in rheumatoid arthritis. Such methods aim to aid the non-invasive characterisation of disease phenotypes and therapeutic response in inflammatory diseases such as IBD and rheumatoid arthritis. The general structure of selective imaging probes is an imaging moiety, a targeting group to localise at a specific site and a linker group to attach the two. The work within this thesis focusses on designing a toolkit of imaging probes that target macrophages by using folate and tuftsin derivatives to target receptors with macrophage selective expression. A variety of imaging modalities are explored in this work such as lanthanide luminescence, magnetic resonance and photoacoustic, with the aim to permit the choice of the most appropriate modality required for a given spatial resolution, scale, and depth penetration. In addition, different bioconjugation strategies have been investigated, such as amide linkages and azide-alkyne cycloadditions, to enable access to a wider variety of macrophage imaging agents. By using a toolkit of molecular components that can be easily combined, this work demonstrates preliminary work for luminescent microscopy, magnetic resonance, and photoacoustic imaging to enable the study of macrophage populations in tissue and model systems. Chapter 1 outlines the processes governing inflammation and the current methods of imaging inflammation. It provides a general overview of the different imaging modalities, with a specific focus on lanthanide chemistry and its photophysics, magnetism and stability in relation to its in vivo imaging. Moreover, the suitability of the targeting moieties - folate and tuftsin - are discussed and the prior work in these areas. Chapter 2 outlines the synthesis, paramagnetic NMR spectroscopy and photophysical characterisation of alkyne appended DO3A derivatives. The purpose of these alkynes is for use in bioconjugation to the targeting moieties with an azide functionality for use in CuAAC and SPAAC. Chapter 3 describes the synthesis of multiple terbium-folate conjugates using solid-phase synthesis, as well as the generation of folate-azides for conjugation to the alkynes discussed in chapter 2. The NMR spectroscopy and photophysical properties of these terbium-folate conjugates are discussed. Chapter 4 details the synthesis of lanthanide-tuftsin conjugates for use in optical and magnetic resonance imaging. The relaxivity and cell diffusion NMR spectroscopy of the gadolinium complexes were studied in blood plasma and whole blood and was compared to a commercially available non-specific gadolinium complex, DOTAREM. Chapter 5 discusses the preparation of macrophage-targeted photoacoustic probes and their optical properties. The probes are investigated for their photoacoustic properties and stability. Chapter 6 provides a summary of work and conclusions that can be drawn, with opportunities for future work proposed. Finally, chapter 7 contains the experimental procedures.

Inorganic nanomaterials are defined as materials with one or more dimension within 1 - 100 nm range. These materials possess unique optical, electronic, thermo-physical, physicochemical and mechanical properties, and represent intensively explored, studied and sought-after commodities for a large variety of applications and manufacturing processes. Heterogeneous catalysts are vital for many industrial processes and often take advantage of the unique reactivity properties of nanomaterials, while battery electrode materials composed of nanomaterials are explored to solve current limitations with higher power densities via stable rapid ion and electron transport, and with high energy density via maximization of the charge storage capability. This thesis provides an insight into synthetic methods, detailed characterization and properties study, and exemplary applications of engineered 2D MoS2 nanomaterials in Li and Na ion batteries, palladium nanoparticles supported on 2D MoS2 nanosheets as heterogeneous catalysts in Suzuki and Heck C-C coupling and 1-pentyne hydrogenation reactions and sulphate functionalized titanium oxide nanoparticles as solid superacid catalysts in the esterification reaction of levulinic acid and pyruvaldehyde Cannizzaro reactions.

The agile ammonia synthesis is a collection of energy generation and storage infrastructure, which allows sustainable, local, and independent energy provision by converting renewable energy to hydrogen and ammonia, as well as in battery energy storage systems such as lithium-ion batteries. Many of these systems utilise archetypal inorganic materials, in particular due to enhanced performance from the incorporation of light-element dopants. Here, three components of the agile ammonia synthesis pathway are investigated in order to better understand the complex structure-activity relationship, in particular by using complex in-situ, in-operando, and inelastic synchrotron X-ray powder diffraction. The nitrogen doping of titania is shown to impart increased structural and electronic defects that can be exploited by photo-absorption of visible light to split water using nothing else but solar irradiance. The generation of oxygen vacancies was observed by anisotropic thermal expansion, and supported by DFT calculations and photocatalytic performance. The use of palladium nanoparticles as an electrochemical energy store by lithium intercalation has been evaluated, and in-depth phase transitions characterised. Though the intercalation process reduces the order of the host framework, the cycling capacity remains constant, indicating amorphisation does not equate to performance degradation. The location of preferential substitutional aluminium sites in zeolite ZSM-5 has been yielded by observing probe molecule adsorption, but also directly by exploiting high-contrast anomalous scattering. The results of various techniques are in broad agreement of the siting, which will have impact the understanding of zeolite synthesis and performance mechanisms.

Anions are ubiquitous in nature. In order to understand them in their natural setting, this thesis focusses on developing lanthanide complexes as hosts for the recognition of biologically relevant anions, particularly chloride and sialic acid. Chapter-I introduces lanthanide chemistry encompassing macrocyclic complexes, luminescence, and MRI. An account of anion recognition and lanthanide complexes used as hosts for biologically relevant anions are reviewed. Chapter-II focuses on developing receptors for chloride recognition. The concept of binuclear lanthanide complexes, bridged by flexible ethane/propane spacer, for chloride recognition is envisioned. The proposed complexes are synthesised, and their anion binding properties are studied by luminescence, NMR spectroscopy, and X-ray crystallography. The study demonstrates the versatility of these binuclear complexes as the strongest chloride binding receptor to function in water and buffers to date. Thus, the work described here, hits a new milestone in anion coordination chemistry, ameliorating detailed exploration. Chapter-III builds on the drawbacks from these neutral complexes towards anion binding, and proposes tryptophan-conjugated cationic binuclear complexes for halide recognition. Initial studies show promising results towards halide recognition in water from this cationic coordination complex. Chapter-IV revisits a ditopic approach of arylboronate-conjugated lanthanide chelates for sialic acid recognition, a tumour biomarker. However, the complexes suffer from protodeboronation, leading to the cleavage of boronic acid which is reported for the first time with structural evidence. The resulting boron free complex binds to L-lactate and D-gluconate. Chapter-V employs the ditopic approach, but with the incorporation of rigid anthracene and dansyl spacers between them, to improve the stability of the arylboronate during complexation. However, the anthracene-based receptor proved synthetically challenging. The success in making the dansyl-functionalised ligand extents the possibility of investigating sialic acid binding. Chapter-VI summarises the work embodied in this thesis and Chapter-VII describes the complete experimental procedures followed in accomplishing the results reported in Chapters II-V.

This work is focused on the synthesis and characterisation of n = 2 Layered Perovskite Oxides. KNdM2O7 (M = Ta, Nb) were synthesized by a two-step cation exchange reaction from RbNdM2O7 via NaNdM2O7. The K-phases adopt a polar Im2m structure. A competition between the requirement of bonding optimization of the K+ and Nd3+-cation sites is demonstrated. A'BiNb2O7 (A' = Rb, Li, Na, K) were synthesized and their structures were determined. All four compounds adopt noncentrosymmetric crystal structures. Comparison with the spherical Nd-analogues demonstrates that although the Rb and Li phases adopt polar structures described in the same space group, the presence of the asymmetric Bi3+ enhances the polarity in these structurers. In the NaBiNb2O7 phase, the noncentrosymmetry is generated from the 6s2 electronic configuration of the Bi3+. The KBiNb2O7 phase exhibits frequent "axis switch" stacking faults in which the (0, ½, z) stacking changes to (½, 0, z) stacking and vice versa. Members of the solid solution with composition Li2SrxCa1-xTa2O7 were synthesized and demonstrated that a structural transformation takes place from hybrid improper A21am structure to proper Pna21 structure with Ca-substitution. Some of the room temperature A21am phases in this series of compounds were shown to have a phase transition to the Pna21 structure at low temperature. Similar phase transition behaviour was observed for the Li2SrNb2O7 phase. The polarity in the Pna21 phase is driven by the SOJT effect of the 4d0-Nb5+ cation. Substitution of 4d-Nb by 5d-Ta in the Li2SrNb2O7 structure lowers the SOJT effect which lowers the stability region of the Pna21 phase. The lifting of inversion symmetry in the polar structures of Li2La(TaTi)O7 and Na2La(TaTi)O7 occurs via two different mechanisms: a trilinear coupled hybrid-improper mechanism for the Li-phase and a more conventional SOJT-driven mechanism for the Na-phase. The operation of these two different mechanisms in materials with a common La(TaTi)O7 core suggests they compete against each other, and further suggests this competition is also occurring in other hybrid-improper ferroelectric phases which contain SOJT active cations. MnCaTa2O7 was synthesized by a topochemical cation exchange reaction from Li2CaTa2O7. MnCaTa2O7 adopts a polar P21nm structure where Mn2+ cations are ordered in chequerboard arrangement. Mn2+ magnetic moments order antiferromagnetically below 56 K. Further cation exchange reactions were performed to synthesize MCaTa2O7 (M = Fe, Co, Zn). Successful synthesis of these phases indicates that the cation exchange chemistry could be used to incorporate divalent transition metal cations within the distorted double perovskite frameworks of n = 2 Ruddlesden-Popper phases.

Over the years, biocatalysis has evolved as an extremely useful tool for synthetic applications due to the incredible selectivity it offers under relatively mild reaction conditions. With the advent of directed evolution and enzyme engineering, new reactivities previously unknown in nature are also being discovered by scientists. One of the main factors that determines the cost and efficiency of many biocatalytic reactions is their cofactor regeneration system. Cofactors are helper molecules that aid an enzyme to sustain catalysis. Their complex structure makes them prohibitively expensive such that their stoichiometric addition for a biocatalytic reaction is not viable. Cofactor regeneration involves the recycling of a catalytic quantity of the cofactor over and over again using a catalyst. Cofactor regeneration techniques for the nicotinamide cofactors have been widely resolved in the past to an extent that some enzymes dependent on these cofactors have found application in industry. This thesis looks at ways to recycle another useful class of cofactors - the flavins. Preliminary efforts to regenerate the deazaflavin cofactors are also presented. Enzymes that rely on flavin cofactors have valuable synthetic utility, however, their application in industry is not well established perhaps due to the lack of efficient recycling methods. This project resulted in an exciting discovery that hydrogenases can reduce flavins under H2, an atom economical reductant. The robust nature and exceptional stability of the hydrogenase, Hyd1 was exploited to supply reduced flavins for ene-reductases and nitroreductases to accomplish H2-driven C=C double bond reductions and nitro reductions respectively with high selectivity. Thus a new application for the hydrogenase enzyme has been uncovered. Demonstration of this novel, single-enzyme flavin regeneration system for application with several useful enzymes, with benefits over current flavin recycling methods, could make this Hyd1/ flavin system a promising choice for use in industry.

This thesis describes the design, synthesis and testing of novel anion host architectures which exploit hydrogen, halogen, and chalcogen bonding for the purpose of selective and stimuli-responsive anion transport across lipid bilayer membranes. Chapter 1 introduces the field of anion supramolecular chemistry, with particular focus on areas of relevance to this thesis, namely transmembrane anion transport. Chapter 2 describes the design, synthesis and testing of monodentate halogen and hydrogen bonding anion transporters. Chapter 3 describes the design, synthesis and testing of bidentate halogen and chalcogen bonding anion transporters with non-protonophoric activity and carriers with higher denticity. Chapter 4 describes the design, synthesis and testing of photo-caged, stimuli-responsive anion transporters. Chapter 5 describes the experimental procedures used within this research and details the characterisation of compounds presented in Chapters 2-4. Chapter 6 summarises and concludes this thesis. The Appendix holds all the original data for the 1H NMR titration experiments and the anion transport assays.

The synthesis and reactivity of compounds containing heteroatomic double bonds are described in this thesis. An overview of multiple bonds between heavier p-block elements is presented in Chapter 1, including the general synthetic routes for the formation of homoatomic and heteroatomic main group multiple bonds. The formation of group 15-element double bonds from azides and phosphaketenes is also outlined. Chapter 2 describes the synthesis of phosphagallenes through the decarbonylation of phosphaketenes. Attempts at forming analogous iminogallenes are also described herein. Chapter 3 explores the reactivity of a phosphanyl phosphagallene towards small molecules such as H2, CO2 and E-H substrates. Two different reaction pathways were found for the activation of amines, both of which were investigated by Density Functional Theory calculations. Chapter 4 expands on the synthesis of group 15-element double bonds by demonstrating the synthesis of Ge=P and Sn=P double bonds. Additionally, the reactivity of a phosphanyl phosphagermene with CO2, amines and silanes is described. Finally, Chapter 5 discusses the aim of using compounds with multiple bonds between the heavier main group elements in order to catalyse the hydroamination of substrates. Two different catalyst designs containing transition metals are targeted: a transition metal- phosphinidene complex and a transition metal substituted phosphagallene. The attempted synthesis of these compounds is described.

Cathode materials remain one of the main limiting factors for increasing the specific energy of lithium ion batteries. The reversible storage of charge on lattice oxygen, called oxygen redox (O redox), has been identified as a promising route for addressing the problem in layered and disordered rocksalt materials. Currently, several interrelated challenges, including slow kinetics, voltage and capacity fade, as well as structural changes, remain, that are investigated in this thesis. A dedicated operando cell, capable of applying significant stack pressure, was built to investigate layered lithium-rich materials. It is used to study Li₁.₂Ni₀.₁₃Co₀.₁₃Mn₀.₅₄O₂ and Li₁.₂Ni₀.₂Mn₀.₆O₂ using high energy-resolution fluorescence-detected X-ray absorption near edge structure (HERFD-XANES), as well as X-ray emission spectroscopy (XES). The complex interplay between bulk oxygen and transition-metal redox is analysed, and it is demonstrated that Ni is fully oxidised to Ni⁴⁺ in one compound but not the other. The structure of the disordered rocksalt Li₂MnO₂F is solved using a combination of neutron pair distribution function (PDF) and neutron diffraction, simultaneously fit using a Reverse Monte Carlo (RMC) approach. The capacity fade for the same material is investigated and found to be initially based on a large charge-transfer resistance, associated with the slow O redox kinetics on discharge.

This thesis describes the synthesis of inorganic semiconductor and layered zinc hydroxide colloidal nanomaterials that could, in future, be used in printing of photoelectrochemical devices. The colloidal nanomaterials are synthesised using organometallic precursors which are reacted with stoichiometric/sub-stoichiometric equivalents of ligand to provide well-defined, monodisperse, phase-controlled copper (Cu), cuprous oxide (Cu2O) and cuprous sulfide (Cu2S) nanoparticles or monolayer exfoliated layered zinc hydroxide (LZH) nanosheets. Chapter 1 provides a general introduction to the field of colloidal nanomaterials, with a comparative overview of different synthetic approaches, recent developments and applications. This is followed by a concise literature review of organometallic synthetic routes to make cuprous oxide (Cu2O), copper sulfide (Cu2-xS) and zinc oxide (ZnO) nanoparticles. It also sets out the thesis aims and objectives. Chapter 2 describes the spectroscopic, microscopy and X-ray diffraction techniques used to characterise the inorganic nanomaterials described within this thesis. Chapter 3 describes the preparation of copper and cuprous oxide nanoparticles starting from mesitylcopper(I). The chapter focusses on changing the capping ligand so as to deliver nanoparticles that are soluble in polar solvents. It also describes the most reproducible and scalable synthesis of the cuprous oxide nanoparticles. The ligand consists of an alkyl ether carboxylate namely, 2-[2-(2-methoxyethoxy)ethoxy]acetic acid, which furnish the resulting nanoparticles with high solubility in solvents such as alcohols and water. These ligands also deliver particles with consistent morphology, small size (~3 nm) and narrow dispersity. The carboxylate ligands can be readily removed after the particles are deposited onto substrates using low temperature (< 200 °C) annealing conditions or displaced by reaction with solutions containing trimethyloxonium tetrafluoroborate. Chapter 4 describes the synthesis of cuprous sulfide nanoparticles starting from organocopper precursors and by reaction with a range of sulfidising agents. Indirect routes include subjecting copper or cuprous oxide nanoparticles to anion exchange reactions or to reaction with different sulfidising reagents (i.e. S(NH4)2, S8). The preferred direct route was established by reacting mesitylcopper with bis(trimethyl silyl)sulfide or hydrogen sulfide, in the presence of substoichiometric amounts of dithiocarboxylic acid or dithiophosphoric acid as ligands, to deliver exclusively chalcocite phase (Cu2S) nanoparticles with small sizes (3-4 nm) and solubility in polar media. The chapter also presents information regarding the colloidal stability in relation to thio- or oxo-containing ligands. Chapter 5 describes a bottom-up route to make layered zinc hydroxides nanosheets via the hydrolysis of organozinc reagents in the presence of a stoichiometric quantity of carboxylic acid ligand. The route provide access to both soluble monolayer nanosheets and functional nanosheets. A series of carboxylate ligands, with alkyl ether chains, are used to make layered zinc hydroxide nanosheets showing spontaneous exfoliation and high solubilities in alcohols or water (180 mg mL-1). Altering the carboxylate ligand allows the introduction of functional groups in the layered structures. Chapter 6 describes preliminary investigation of the suitability of cuprous oxide or sulfide nanoparticles as colloidal 'inks' for thin-film fabrication. Different deposition techniques yield films which are assessed for homogeneity, transparency and thickness. Thin-films of cuprous oxide are tested as photocathodes. Methods to improve the film deposition and device architectures are also discussed. Chapter 7 provides an overall conclusion and outlook on the thesis. Chapter 8 describes the experimental protocols employed both in nanomaterial synthesis and outlines characterisation data.

Chapter 1, Introduction: The concepts of solid-state organometallic chemistry; single-crystal to single-crystal (SC-SC) transformations; alkene isomerisation; continuous flow techniques; and para-hydrogen induced polarisation (PHIP) are introduced and given brief theoretical and practical backgrounds, each relevant to the following chapters. Chapter 2: This chapter explores the successful application of P2-type Rh-containing SMOMs in the solid- gas catalytic isomerisation of 1-butene, and describes their deployment under both batch and continuous flow conditions, achieving non-thermodynamic selectivity. In an effort to explore the chemical space, a wide variety of ligand-varied SMOMs are deployed under flow conditions: the direct tunability of solid-gas catalysis is demonstrated through ligand (R-group and tether-length) modification. Chapter 3: The SC-SC chemistry of two related systems are described: a PONOP-bound cationic Ir- containing SMOM (in collaboration with the Diamond Light Source) and a P2-type perfluorophenyl/Rh- containing SMOM. Remarkably, both of these systems undergo SC-SC transformations with shifts in periodic structure upon solid-state hydrogenation and desolvation respectively. These transformations are tracked with single-crystal X-ray diffractometry as well as solid-state NMR spectroscopy. Chapter 4: This chapter explores the NMR batch-scale solid-gas catalytic hydrogenation-polarisation of unsaturated substrates with para-hydrogen by P2-type Rh-containing SMOMs. Conducted in collaboration with the Centre for Hyperpolarisation in Magnetic Resonance, York (CHyM), the tunability of solid-gas catalysis is again demonstrated through ligand modification, yielding vastly different activities and rates of deactivation. The solid-gas hydrogenation mechanisms are elucidated with the assistance of D2 gas. Chapter 5, Experimental: The syntheses and characterisation of materials not already reported in the literature are provided, in addition to experimental methods. Chapter 6, Future Directions: The possible future directions for these projects are described in a short epilogue.

This thesis describes the development of a range of catalysts for polyester synthesis via the ring-opening copolymerisation (ROCOP) of epoxides and anhydrides. Chapter 1 provides an introduction to the ROCOP of epoxides and anhydrides, with a particular focus on catalyst development and mechanism. It also introduces the concept of switchable catalysis and describes its application to the synthesis of block polyesters. Chapter 2 details the synthesis and characterisation of a series of monometallic M(III) complexes (M = Al, Cr, Mn, Fe, Co). Their application as catalysts for the ROCOP of cyclohexene oxide (CHO) and phthalic anhydride (PA), and the ROP of decalactone (DL), is explored. The complexes featuring Al(III) and Co(III) are found to be the most active catalysts for these polymerisations. Chapter 3 details the application of the Al(III) and Co(III) complexes synthesised in Chapter 2 to the one-pot switchable catalysis reaction of CHO, PA and DL. Triblock copolymers with molar masses up to 57 kg mol-1 are synthesised. The catalytic activity of these complexes is shown to be significantly higher than previously used commercial salen catalyst systems. Chapter 4 details the synthesis and characterisation of a series of heterodinuclear Al(III)/M(I) (M(I) = Group 1 metal) complexes. All are shown to be excellent catalysts for the ROCOP of CHO and PA, with the Al(III)/K(I) and Al(III)/Rb(I) congeners being the most active. Subsequent kinetic investigations, combined with DFT calculations, result in the proposal of a mechanism where the epoxide is bound and activated by the Al(III) centre and the M(I) ion binds the carboxylate chain end. The scope of the catalysis is established for a wide range of epoxides with anhydrides and CO2. Chapter 5 details the development of an Al(III)/K(I) complex bearing organometallic coligands. It is demonstrated that use of this complex, in conjunction with bifunctional protic chain transfer agents, can yield monodisperse high molar mass polyesters via the ROCOP of vinyl-cyclohexene oxide (vCHO) and PA. The mechanical and thermal properties of the polyesters are investigated to establish the impact of increasing polymer molar mass. Chapter 6 outlines the key developments of this thesis and suggests future avenues for research that build on the work described. Chapter 7 provides experimental details for Chapters 2 - 5. An Appendix is provided that contains supplementary figures and data that support the discussion throughout Chapter 2 - 5.

This thesis examines the synthesis of novel acyclic silylenes with amido, boryl, gallyl and/or boryloxyl substituents, and their reactivities towards small molecules such as H2 , CO2 , H2O, NH3 etc. The silylene systems were also used as precursors for compounds featuring silicon-heteroatom double bonds, with a focus on the attempted synthesis of molecules featuring a Si=O moiety (silanones). Chapter 2 discusses the reactions between the gallyl anion [(DippNCH)2Ga] - and Si(II) precursors such as IDipp·SiCl2 and (NTMSDipp)(IiPrMe)SiCl. While an unexpected silyl anion formed when IDipp·SiCl2 is used, a novel NHC stabilized silylene can be synthesized by metathesis between [(DippNCH)2Ga]- and (NTMSDipp)(IiPrMe)SiCl. The gallyl-substituted silylene reacts with N2O, however, only a silyl migrated product can be isolated instead of the expected silanone. The reaction between Cy2NSiBr3 and [(DippNCH)2B] - , in attempt to install an amido substituent on a potential silylene system without a labile N-SiMe3 moiety, results instead in a C‒H activation product. Chapter 3 reports the synthesis of a novel bisboryloxysilylene, together with its heavier Ge, Sn and Pb congeners (the latter in collaboration with Dr Ying Kai Loh). Structural parameters of these tetrylenes obtained by X-ray crystallography, including the E‒O, O‒B bond distances and O-E-O, E-O-B bond angles (E = Si, Ge, Sn or Pb) show a trend consistent with expected periodic trend for group 14 elements, resulting from relativistic effects and increasingly poor s-p mixing on descending group 14. Further investigation involves studies of the reactivity of the bisboryloxysilylene fowards small molecules possessing an E‒H bond (E = H, N or O). Although no reaction is detected with H2, the silylene is able to activate the polar E‒H bonds in water, ammonia and tert- butyl amine. Such processes most likely occur through a three-molecule transition state as shown by DFT calculations. Chapter 4 explores the possibilities of synthesizing Si=E (E = C, N, O or Se) containing compounds using the bisboryloxysilylene as the precursor. The reaction between the silylene and N2O generates the first example of a silahyponitrite, which can be regarded as a masked silanone (by N2O) as the bound N 2 O can easily be substituted in reactions with CO2 and Ph3P=O. When the silylene is treated with an excess amount of selenium, a novel tetraselenosilolane can be isolated. Three out of the four selenium atoms in this compound can be removed by adding Ph3P to generate a silaselenone. Attempts have been made to synthesize a Si=N or Si=C double bond. In the former case Me3SiN3 was used as the source of Me3SiN. However, this reaction only gives a two-fold addition product, a silaazide. In the latter case Ph3P=CH2 was utilized to act as a :CH2 transferring agent. The reaction proceeds instead via a [4+1] cycloaddition process, yielding a dearomatized silaheterocyclic compound.

Advanced studies of structures and dynamics of functional materials based on metal-organic frameworks (MOFs) showing exceptional stimuli-driven properties is of strong current interest for the design of next-generation smart materials, especially for sorption-based applications such as gas storage, energy storage, controlled drug delivery, and molecular sensing, to name but a few. State-of-the-art diffraction and spectroscopy in conjunction with theoretical calculations are one of the most powerful approaches to achieve these detailed analyses at a molecular level. This thesis aims to study mechanistic aspects of stimuli-responsive behaviours responsible for a distinctive stepwise ammonia (NH3) adsorption in the defect-rich Zr-based metal-organic frameworks (MOFs), namely UiO-67 and its isostructural UiO-bpydc, both experimentally and computationally. In Chapter 3, high-resolution neutron and synchrotron diffractions along with Rietveld refinement and density functional theory (DFT) calculations have been used to characterise the binding domains and the interactions of NH3/ND3 with defect-rich UiO-67 and UiO-bpydc containing biphenyl dicarboxylate and bipyridine dicarboxylate linkers, respectively. The results establish that the dramatic alteration of stepwise adsorption processes is closely associated with hydrogen bonding network between NH3/ND3 and the frameworks at the disordered/defective trigonal and lozenge pore windows of the materials without significant change in pore volume and unit cell parameters. Specifically, UiO-bpydc is possible to make stronger and more extensive hydrogen bonding using pyridine sites of the linker than in UiO-67. These molecular controls lead to stimulus-tailoring properties such as gate-controlled porosity by dynamic linker flipping, disorder, and structural rigidity which are further confirmed by temperature-dependence of in situ structural analyses accompanied with guest-induced rotational motions of the organic linkers studied by DFT in Chapter 4. To get deeper insights into the interesting NH3-induced stepwise adsorption, the dynamic features of the MOF-NH3 systems have been further investigated by using advanced inelastic neutron scattering (INS), quasi-elastic neutron scattering (QENS) in conjunction with theoretical calculations. Guest-induced linker stiffening reflected by the suppression of lattice motions of the host frameworks upon NH3 adsorption is achieved, which exhibits greater effect in the UiO-bpydc case. More excitingly, analysis of INS difference spectra reveals heterogeneous dynamics of the trapped NH3 depending on MOF functionality and gas loading. For the UiO-67, the well-ordered NH3 molecules primarily adsorbed at μ3-OH have more feasibility to undergo progressive interactions with the incoming NH3 molecules, signifying its more accessible porous structure for NH3 inclusion due to the lack of guest-stimulated pore blocking conversely observed in the UiO-bpydc. QENS study elucidates negligible mobility of NH3 in both MOFs at the lowest dosage, indicative of the similar localised diffusion caused by strongly bound NH3 at the μ3-OH sites of the hosts. On the other hand, the NH3 diffusivities in these frameworks become distinct at higher NH3 uptake where the stepped adsorption occurs. This observation points toward the confined NH3 molecules experiencing a diversity of either pore environments or host-guest interactions.

We present an experimentally guided study of film layer structure and opto-electronic properties of transition metal oxide (TMO) films. The oxide material system studied comprised the metals silicon (Si), zinc (Zn), and indium (In). The films were deposited via radio frequency magnetron sputtering (RFMS) on room-temperature Corning Eagle XG Glass (CEXG) substrates. Distinct (bi-layer (BL) vs single-layer (SL)) layer structures manifest as a function of angular distribution or pressure distance product (Greek letter 'phi') of sputtered material flux sourcing film growth. The films are amorphous, transparent and semiconducting. Experimental determination of absolute temperature (T) dependence of resistivity (Greek letter 'rho') revealed that at temperatures close to room-temperature, ionized impurity scattering (IIS) is the dominant conduction electron scattering mechanism. Thence, application of the Brooks-Herring (BH) model of IIS permitted analysis of the electronic state of the films. Thereby, the electronic state was revealed to be highly compensated. The design of experiment (DOE) and (associated) response surface analysis (RSA) frameworks were recruited from the very first stage - namely, the stage of film fabrication - of this study. This provisioned a self-referencing set of (nine) films (the 'samples') that are the subject of this study. The two layers of the BL films are / will-be-referred-to-as the sub-plantation layer (SPL) and the thin-film layer (TFL). The SPL is situated mediate substrate and TFL, and constitutes thereby the film-substrate interface. For consistent nomenclature, the term 'TFL' will be used to refer to the sole (film) layer of SL films. The layer structures of the films were established via x-ray reflectometry (XRR). The films were interrogated optically via spectroscopic ellipsometry (SE) (at room-temperature), and electrically via AC Field Hall Effect (ACFHE) measurements (between T = 10.1 K to 300 K). An account of the understanding of the film layers - viz., SPL, and TFL - as has been achieved, is as follows: ~ The sub-plantation layer (SPL) ~ We report the controlled emergence of a bonafide nanoscale layer - the SPL - at (comprising) the film-substrate interface. The determination of presence of a SPL is direct - that is, sans any assumptions, or modeling - via Fourier analysis of XRR results. We present three independent - experimental, empirical, and theoretical - threads of analysis to rationalize emergence of the SPL, as follows: > In terms of deposition process conditions under which a SPL manifests. Our semi-quantitative analysis is in terms of angular distribution or phi of the material flux sourcing film growth. Evidently, this thread of analysis is beholden to the specific physics of the deposition process, namely, RFMS. > Via RSA of SPL physical properties (SPL thickness (dSPL), SPL density (DSPL), and SPL roughness (rSPL)). This analysis reveals the following two process factors to be relevant: RF power (PRF), and process gas pressure (p). While the analysis is on the basis of experimentally observed process factors dependence of the physical properties noted, it is not beholden to the physics of the deposition process (RFMS). > Via dimensional analysis (DA) of the physical properties noted previously, in light of RFMS process. The dimensionless group for PRF (PRF*) thus determined reveals precisely the two previously noted process factors to be relevant. This analysis is ab initio. We highlight implications of our results for the industrially important problem of sputtered-film-on-substrate adhesion. Thereby, our results bear commercial promise, particularly for research and development (R&D) of flexible electronics applications. ~ The thin-film layer (TFL) ~ We quantify the semiconducting nature of the films (TFLs) on basis of optical (via SE) and electrical (via ACFHE) measurements of their room-temperature electronic properties. We interrogate the film (material system) electronic state on basis of the experimentally determined T dependences of conduction electron concentration (n) and conduction electron mobility (Greek letter 'mu'). Presence of a T-range (in the vicinity of and including room-temperature) where IIS is the dominant conduction electron scattering mechanism is established. Application of the BH model of IIS then lead to the (quantitative) determination that the electronic state is (highly) compensated. This determination - consistent with the experimentally observed anomalous oxygen content dependence of - is consistent with trap limited conduction. Thereby, we relate the electronic state to the chemistry and physics of film microstructure and material system. ~ The ready-reckoner ~ Figure 7.1 presents another and visual walk through - a 'ready-reckoner' - of this study. ~ Epilogue ~ This study represents new lines of investigation for the Professor Peter P. Edwards FRS ML Group.

Heterogeneous catalysis plays an important role in the pharmaceutical and petrochemical industries. Due to the poor chemical selectivity in many processes, it is essential to design novel catalysts to resolve this problem. Recently, interstitially modifying transition metal NPs with light elements has become a potential strategy for adjusting surface energy and tuning catalytic activity. However, this new class of catalysts remains relatively unexplored due to a lack of adequate characterisation evidence. Herein, the work presented in this thesis continues the structural characterisation of the Pd-intB/C and Pd-intLi/C, reported from previous work, by using a novel combination of analytical techniques that span from the atomic to the macro level. Initially, these characterisations showed that after B and Li incorporation the Pd lattice maintains a face-centred cubic structure, but tolerates structural distortion. These structural distortions can further result in the local formation of the HCP structure. Additionally, the combination of STEM-EELS and ptychography was attempted to directly observe the presence of B and Li at the atomic level. Meanwhile, in order to broaden the scope of the light element modified catalyst family, attempts were made to alloy Li into the Pt host metal system. It was found that the unit cell of the Pt contracts after thermal treatment at elevated temperature, indicating the formation of the Pt-subLi nano bimetallic alloy. The combination of XPS and ssNMR confirms the presence of Li in the metal framework, in addition to the SXRD. The STEM-ADF imaging reveals the presence of the Pt7Li. Seemingly, this is the first report of Pt-Li based NPs synthesis to date. This catalyst displays premium 2,5-bis(hydroxymethyl)furan (BHMF) selectivity when catalysing HMF hydrogenation; this is due to the Li blocking specific, undesired reaction pathways. It is anticipated that such an in-depth investigation will help influence the future design and characterisation of novel, light element alloyed systems.

This thesis examines the synthesis and the reactivity of both novel and previously reported intramolecular dimethylxanthene, dimethylthioxanthene and acridan derived frustrated Lewis pairs (FLPs). Moreover, it also reports on novel acridan-based Lewis bases and acids, and the subsequent reactivity of such species within intermolecular FLPs Chapter 1 describes the background of FLPs including the history of FLPs, and the literature studies on the reactivity of FLPs in small molecules activation/captures and catalysis. Chapter 2 reports all the experimental methods used in this thesis and the preparation of dimethylthioxanthene and acridan backbone precursors. Chapter 3 introduces an improved method for the preparation of intramolecular dimethylxanthene derived FLPs featuring Lewis acid/base pairs of -B(C6F5)2/-PPh2 and -B(C6F5)2/-PiPr2. This synthesis proceeds through isolated lithium complexes and not only gives higher overall yields than the literature method, but also avoids the use of large excesses of Br2, pyrophoric sBuLi, and column chromatography techniques for purification. In addition, this chapter introduces the synthesis of novel intramolecular derived ditert-butyldimethylxanthene and dimethylthioxanthene FLPs with wider P···B separations. In chapter 4, the preparation of novel species derived from an acridan backbone are discussed. This scaffold was used for the synthesis of a range of disubstituted phosphine (PNP) Lewis bases. The large steric bulk of tert-butyl, iso-propyl and mesityl substituents was shown to prevent clean disubstitution of the phosphine moiety onto the acridan backbone. Phenyl and para-tolyl substituents, by contrast, gave the desired disubstituted acridan derivatives, and these species have been characterised spectroscopically and crystallographically. The reactivity of these Lewis bases with the Lewis acid B(C6F5)3 has been investigated. Neither donor/acceptor coordination nor frustrated Lewis pair behaviour is observed; unexpected C-H activation of the N-Me group of the acridan backbone is proposed based on spectroscopic data, and the structural authentication of a related derivative. This represents the first example of FLP-mediated sp3 C-H bond activation. Additionally, the synthesis of a novel intramolecular acridan-derived FLP featuring -PPh2/-B(C6F5)2 as the Lewis base/acid pair has been successfully achieved. This acridan FLP features a P···B separation (4.451(9) Å), which is slightly wider that the analogous dimethylxanthene FLP. Interestingly, it reacts with H2 at room temperature in a manner utilizing the proximal N-CH3 moiety as the Lewis base instead of the PPh2 group. This result led to related synthesis and reactivity studies of the bis-borane Lewis acid (BNB) featuring two pendant B(C6F5)2 groups, which also reacts with H2 at room temperature (1 atm) in similar fashion utilizing B/N cooperativity. Furthermore, this compound also shows unusual C-N bond activation behaviour accompanying the uptake of CO2 and CO in the presence of tBu3P. Chapter 5 reports on further investigations into the reactivity of previously reported dimethylxanthene-based phosphine/borane FLPs towards alkynes. The -PPh2 and -PMes2 containing systems (featuring B(C6F5)2 as Lewis acid component) were found to C-H activate the terminal alkyne PhCCH; the weaker -PPh2 donor system was found to give rise to an equilibrium mixture of the free FLP and phosphonium acetylide in CD2Cl2 solution at room temperature. This system was also found to react with the B-H bonds of HBpin and HBcat via C-B/B-H metathesis reactions that lead to the replacement of the -B(C6F5)2 moiety by -Bpin/-Bcat, with accompanying transfer of HB(C6F5)2 to the phosphine Lewis base. This transformation underpins the ability of this system to act as a pre-catalyst for the hydroboration of terminal (PhCCH) and internal alkynes (PhCCPh and PhCCMe) with HBpin. The active species is derived from the HB(C6F5)2 fragment generated in the borane metathesis reaction. Chapter 6 presents further reactivity studies of dimethylxanthene FLPs featuring - PiPr2 and -PPh2 Lewis bases (with -B(C6F5)2 as the Lewis acid) in the activation of Si-H and Sn-H bonds. It was found that the more strongly Lewis basic -PiPr2 FLP could activate the Si-H bonds in PhSiH3, Ph2SiH2 and SiH4; further reaction leads to Si/B metathesis yielding 'migrated' species in a similar fashion to that occurring with HBpin and HBcat. The more weakly Lewis basic -PPh2 FLP however, was found to be unreactive towards Ph2SiH2, Et3SiH and Ph3SiH, while the reaction with PhSiH3 leads to the formation of a similar 'migrated' species. The -PiPr2-containing FLP was also found to be reactive towards heavier group 14 hydrides, activating the Sn-H bonds of nBu3SnH and Ph3SnH to form zwitterionic phosphonium stannylium hydrides.

This thesis reports the reactivity of zirconocene hydrazides, imides and silylamides, as well as the reactivity of titanium permethylpentalene complexes. Particular focus is paid to the reactions of hydrazides and imides with boranes and silanes, and reactions of silylamides with terminal alkynes, boranes and silanes.

This thesis discusses the development of novel titanium-containing layered double hydroxides (Ti-LDHs) as semiconductor photocatalysts for the photo-oxidation of simple organic molecules. LDHs are introduced in Chapter 1 as compositionally flexible anionic clays, whose layered structure and tuneable properties make them highly interesting in a wide range of applications, including environmental purification, drug delivery and photocatalysis. In the latter case, LDHs have been used primarily in the photocatalytic degradation of organic pollutants, photo-reduction of CO2 and photocatalytic water splitting. Only limited research has been done into the controlled organic molecule photo-oxidation, where the oxidation is stopped at an intermediate stage rather than proceeding all the way to degradation products. Chapter 2 outlines the five different synthetic methods for Ti-LDH preparation and their viability in the synthesis of pure NiTi- and MgAlTi-LDHs with different Ni:Ti and Al:Ti ratios, respectively. The crystallinity, morphology, structure, composition and band gap energies of the Ti-LDHs were analysed, so as to determine the effect of the synthetic conditions and Ti content on their properties. Furthermore, the highly crystalline urea hydrothermal MgAlTi-LDH samples were characterised by high-angle annular dark-field imaging (HAADF) as well as by 1H, 27Al and 47/49Ti solid state NMR spectroscopy. In Chapter 3, the activity of the Ti-LDHs in the photo-oxidation of diphenylmethanol is studied, and compared to that of anatase TiO2 as a benchmark photocatalyst. The importance of short-wavelength radiation is discussed, especially for control experiments in the absence of a catalyst. The effects of the synthetic method, Ti content, catalyst and reactant loading, and irradiation time were examined for selected Ti-LDHs. Chapter 4 extends the study of the photocatalytic properties of Ti-LDHs beyond diphenylmethanol photo-oxidation to also include benzyl alcohol, cyclooctanol and benzylamine. This allows the determination of whether Ti-LDHs can be used to photo-oxidise a wider range of functional groups as part of either aromatic or aliphatic systems. Lastly, Chapter 5 details the synthesis and characterisation of TiO2@Ti-LDH core-shell hybrid materials, and looks at their application in the photo-oxidation of diphenylmethanol. The conversion using the core-shell photocatalysts was compared to that obtained with a mechanical mixture of TiO2 and Ti-LDHs, in order to study any synergistic heterojunction effects.

This thesis describes the synthesis and reactivity of group 13 coordination complexes of the 2-phosphaethynolate anion (PCO–). The synthesis and characterization of a stable phosphaethynolatoborane, [B]OCP ([B] = N,N′-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaboryl), is described. This compound represents the first main-group, oxygen-bound isomer of the 2-phosphaethynolate anion to be structurally authenticated. The subsequent cyclisation chemistry of this compound was explored. The reactivity of [B]OCP with a number of neutral and anionic nucleophiles was explored, the reaction outcome was found to be dependent on the properties of the nucleophile employed. Addition of catalytic amounts of tbutyl-isocyanide induced isomerisation to yield the linkage isomer, [B]PCO. The mechanism of this conversion was explored experimentally and computationally. The nucleophilicity of [B]OCP was also explored, its steric properties allow access to a series of tungsten trisphosphaalkyne carbonyl complexes. The reaction of [B]OCP with tris(pentafluorophenyl)borane demonstrated an increase in nucleophilicity with respect to the alkyl-substituted tert-butyl phosphaalkyne. In an attempt to access the cyaphide anion, CP–, the reduction chemistry of [B]OCP was explored with the aim to selectively cleave the O–C bond. The reaction outcome is dependent on the reducing agent employed, however selectivity for the desired bond was poor, giving rise to complex product mixtures. It was possible to isolate and partially characterise a magnesium cyaphide complex. Next, a series of gallium phosphaketenes were synthesised. Both photolytic and chemical decarbonylation processes were explored, allowing access to base stabilised phosphinidenes. The ligand displacement methodology was expanded on to allow access to a compound with a gallium phosphorus double bond.

This thesis explores the use of boryl, terphenyl and amido ligands in a variety of interesting areas of low-valent germanium chemistry. In Chapter 1, a general introduction to the state of the art in this field is provided. The ligands that have proven pivotal in recent decades in germanium chemistry are introduced, and the developments that they have facilitated are then described. Finally, the field of germanium cations is introduced. In Chapter 2, the general methods deployed in this thesis' work are described; modified literature procedures for the syntheses of a variety of starting materials that were used in this work are also detailed. In Chapter 3, the synthesis of novel germylium-ylidenes is examined, utilising a strategy of chloride abstraction from chlorogermylenes substituted by a combination of N-heterocyclic carbene and anionic ligand. The structural characterisation of the first isolable germylium-ylidenes featuring boryl, terphenyl, primary amido, and borylamido ligands is reported, and the influence of these ligands on the structure of these compounds is discussed in detail. For instance, concerning terphenyl-substituted cations, the effect of subtle variation in ligand steric bulk is explored, in terms of changing the degree of aggregation, and leading to secondary interactions with the ligand peripheries. In Chapter 4, the reactivity of these germylium-ylidenes is then explored. The first activation of E-H bonds by isolable germylium-ylidenes is reported, as well as novel onward reactivity of some of the products as a result of their charge. For instance, oxidative addition of certain cations with ammonia leads to a subsequent elimination. Attempts towards the synthesis of multiple bonds is described, and the novel compounds this leads to discussed; for instance, reaction of a boryl-substituted cation with trimethylsilylazide leads to the formation of the first germylium azide. In Chapter 5, the synthesis of compounds featuring boryl-substituted germanium-transition metal bonds is investigated, and the first examples of such compounds for the cases of molybdenum, cobalt and iron are reported. In Chapter 6, conclusions are drawn from the work of this thesis, and suggestions for future work are made.

The extended metal atom chains are a family of complexes with a linear, metallic chain surrounded by four equatorial polydentate ligands and capped by two axial ligands. The tricobalt extended metal atom chains studied in this work have a trimetallic core with halide axial ligands: the fluoride, chloride, bromide and iodide complexes. In this work we adopt correlated ab initio approaches (DFT and MCSCF) to the study of the metal-metal bonding between the cobalt atoms in the chain. The literature surrounding the tricobalt series is extensive, reflecting the vast array of experimentally observed phenomena. X-ray crystallography has been used to determine crystal structures at a range of temperatures, and has shown the structure of the tricobalt chain can vary continuously between two extremes: symmetric with equal Co- Co bond lengths and unsymmetric with one Co-Co bond markedly lengthened. Magnetic measurements show an increase in temperature initiates a spin crossover in all known instances of the complex, in both the solution- and crystalline-phase. The data reported in the literature is consistent with a low-spin doublet ground state at low temperatures, however resolution of the high-spin state multiplicity is complicated by a lack of saturation in the effective magnetic moments at the highest available temperatures. In Chapter 1 we present a detailed review of the entire literature regarding the tricobalt extended metal chains such that the reader can put into context the entire range of remarkable behaviours. In Chapter 2 we discuss the theoretical techniques underpinning this thesis, while Chapter 3 describes the specific computational methodologies used. In Chapter 4 we undertake a comprehensive and systematic study of the symmetric form of the bromide complex. We detail electronic configurations of potential low-lying excited states that arise from the low-energy excitations within the ground state. The properties of the ground and excited states are used to explain the experimentally observed spin crossover and structural temperature dependence. We identify a symmetric sextet state, the thermal population of which is found to be consistent with the behaviour of those crystals that remain symmetric in their observed temperature ranges. In Chapter 5 we adopt the same systematic approach to study the unsymmetric form, again focusing on the bromide complex, and identify a quartet state that fits the behaviours seen in those crystals that show a transition between the symmetric and unsymmetric limits in their observed temperature ranges. In Chapter 6 we describe the electronic mechanisms by which the tricobalt bromide system makes this transition, examining low energy distortions in the symmetric low-spin state structures and the effect of the high-spin state population on the X-ray crystal structure. In Chapter 7 we extend the analysis developed in the first three chapters to study the complexes with the other axial halide ligands. Our results agree with the experimental findings of a decreasing spin crossover temperature going down the group VII halides F > Cl > Br > I, and we present a re-evaluation of the link between the experimental structures and the spin crossover process.

There is a clear and urgent need for rechargeable batteries of higher energy density. Alkali-ion batteries based on Li-ions are the state-of-the-art, although Na-ion may offer a cheaper alternative. In both cases the cathode imposes the biggest limitation on overall energy density. Alkali-rich cathode materials can store alkali-ions and electrons densely by invoking redox chemistry of both the transition metal (TM) and oxide ions in the lattice. However, O-redox is accompanied by voltage hysteresis, irreversible O-loss and complex structural changes. In this thesis, model Na-ion materials have been investigated to isolate and examine these phenomena. Firstly, Na0.67[Mg0.28Mn0.72]O2, with Mg2+ ions occupying the TM layer rather than alkali-ions, is studied and shown to exhibit O-redox. This reveals that ionic interactions between the TM layer substituent and O are the necessary precondition for O-redox. Secondly, by comparing the O-loss behaviours of Na0.67[Mg0.28Mn0.72]O2 and Na0.75[Li0.25Mn0.75]O2, the critical role of the TM layer substituent is revealed; when removed from the structure, the co-ordination number around O can drop below three and O-loss is triggered. Unlike Li+, Mg2+ is retained within the structure preventing O-loss. Thirdly, O-redox materials Na0.75[Li0.25Mn0.75]O2 and Na0.6[Li0.2Mn0.8]O2 are studied in parallel to understand why the former exhibits voltage hysteresis and the latter not. The preservation of the TM layer ordering scheme is shown to prevent hysteresis maintaining stable electron holes on O2- in Na0.6[Li0.2Mn0.8]O2. For Na0.75[Li0.25Mn0.75]O2, severe in-plane TM migration destroys the ordering scheme, triggered by formation of molecular O2 gas which is directly evidenced for the first time in the bulk. Reduction of O2 occurs on discharge at low voltage giving rise to hysteresis. Finally, a new Li-rich oxyfluoride, Li2MnO2F, with a stable disordered rocksalt structure is presented. Li2MnO2F stores charge utilising both Mn and O-redox with negligible O-loss demonstrating the potential of disordered rocksalts to deliver high energy densities.

This thesis examines the potential of hydrides of the group 13 metals aluminium and gallium to function as homogeneous catalysts for the reduction of unsaturated substrates including CO2, aldehydes and ketones. In addition, it reports on studies designed to probe the mechanisms by which these processes occur. Chapter 3 details the preparation of a series of novel β-diketiminate (or Nacnac) ligated aluminium hydrides of the form {HC(XCNDipp)2}Al(R)H {X = Me, NMe2; (DippNacnac)Al(R)H}, which differ in the nature of the auxiliary R substituent and the Nacnac backbone itself. These systems show considerable variation in the nature of the Al-H bond and significant differences in reactivity with respect to the hydroalumination of carbon dioxide. Electron-donating R substituents give rise to weaker and more hydridic Al-H bonds, which exhibit enhanced rates of insertion of the CO2 molecule. The treatment of the resulting κ1-formate complexes with B-H containing reductants under stoichiometric and catalytic conditions reveals that no Al-O/B-H metathesis occurs, even under forcing conditions. This study did however lead to the isolation of a range of novel boryloxy complexes, (DippNacnac)Al(R)(OBXX') (X = X' = cat, 9-BBN; X = H, X' = OMe) and borohydride complexes (DippNacnac)Al(R)(H2BX2) (X2 = (9-BBN), H2). It is concluded that no catalytic turnover can be achieved in the reduction of CO2 by boranes mediated by these aluminium hydrides, presumably due to the excessive strength of the Al-O bond, and the consequent lack of viability of Al-O/B-H metathesis. Chapter 4 describes a number of synthetic routes for the preparation of unsymmetrically substituted Nacnac-ligated gallium monohydride complexes, including a rare example of a base-stabilised cationic gallium hydride. The range of novel hydrides reported offers variation in the steric and electronic properties of the auxiliary R substituent. Studies of stoichiometric reactivity reveal that, as with related alanes, gallium hydrides which bear more σ-donating R substituents are more amenable to the hydrogallation of CO2. In addition, studies were undertaken to establish the impact of both the gallium-bound R substituent and the borane on Ga-O/B-H metathesis processes leading to the regeneration of a Ga-H bond from the corresponding formate complex {HC(MeCNDipp)2}Ga(R)(OC(O)H), [Dipp1]Ga(R)(OC(O)H). With the factors influencing both the insertion and metathesis processes established, the ability of these Nacnac gallium hydrides to catalyse the borane-mediated reduction of CO2 was then investigated. The work presented in Chapter 5 demonstrates that the Nacnac-ligated gallium hydride complex, [Dipp1]Ga(Ad)H, can be employed in tandem with B(C6F5)3 to effect the catalytic hydrosilylation of CO2. Whilst forcing conditions are required to bring about catalytic turnover (and only modest TOF values can be achieved), this system represents a rare example of a main group hydride catalyst for this process. In addition, it can be shown that selectivity can be controlled through the ratio of Lewis acid co-catalyst employed. A series of mechanistic studies is described which shows that the B(C6F5)3 co-catalyst leads to the activation of the gallium complex towards both processes (insertion, metathesis) that are key to catalytic turnover. During the course of this study, the first examples of three-coordinate β-diketiminate-ligated gallium cations were synthesised. Chapter 6 describes a study of the mechanisms of the reduction of organic carbonyl substrates, mediated by aluminium and gallium hydrides. It is demonstrated that the hydrogallation of aldehydes by β-diketiminate-ligated gallium hydrides is relatively limited and only one gallium hydride of this nature, [Dipp1]GaH2, could be found to hydrogallate benzaldehyde, requiring forcing conditions to bring about such reactivity. However, the gallium alkoxide product so generated is amenable to rapid Ga-O/B-H metathesis to regenerate a Ga-H bond and release the reduced organic product. Thus, in accordance with the research reported in Chapters 4 and 5, the hydroboration of C=O bonds can be effected by gallium systems based on an inner-sphere mechanism involving insertion and Ga-O/B-H metathesis steps. By contrast, a wide range of β-diketiminate-ligated aluminium hydrides can be shown to hydroaluminate benzaldehyde under ambient conditions. However, in this case the resulting metal alkoxides are resolutely unreactive towards B-H containing reagents. This behaviour is consistent with the reactivity towards CO2 reported in Chapter 3 and can be rationalized by the underlying thermodynamics of Al-O/B-H metathesis (which are unfavourable). Nonetheless, literature reports of the catalytic hydroboration of benzaldehyde by aluminium hydrides are confirmed to be correct - and a series of mechanisms based on outer-sphere processes which avoid 'net cleavage' of the Al-O bond have therefore been investigated.

Q-dependent diffuse scattering was observed at low angles in a neutron diffraction experiment performed on the relaxor ferromagnet La3Ni2SbO9 using a spin-polarised beam. The nuclear component could be modelled using direct Monte-Carlo methods if it was assumed that short (~5.5 Å) Sb-Sb contacts were energetically disfavoured. The magnetic component of the diffuse scattering at 110 K (TC = 108 K) was analysed using both direct and reverse Monte-Carlo techniques. When antiferromagnetic nearest-neighbour coupling was assumed to be dominant in this perovskite, second neighbour coupling was found to be weak but non-zero with third-neighbour coupling being negligible. The short-range structural and magnetic orderings were found to have correlation lengths of 15 and 9 Å, respectively. The consequences of replacing d10 Sb5+ by d0 pentavalent cations were investigated; all the compounds reported are isostructural with La3Ni2SbO9. La3Ni2TaO9 was found to be a relaxor ferromagnet but La3Ni2NbO9 behaved as a spin glass below 35 K. Solid solutions La3Ni2SbxTayNb1-x-yO9 were synthesised and characterised. It was again shown that the relaxor behaviour is incompatible with the presence of Nb5+ in the system. In contrast, doping La3Ni2B'O9 (B' = Sb, Ta or Nb) with Cu2+ cations was found to increase TC and the bulk magnetisation. For example, La3Ni1.75Cu0.25NbO9 exhibits ferrimagnetic behaviour below ~90 K with the development of long-range G-type magnetic ordering. It is proposed that relaxor regions and long-range ordered regions coexist in this system. The sensitivity of cation ordering, and hence magnetic behaviour, to the charge difference between Ni2+ and the diamagnetic six-coordinate cation was studied by replacing Sb5+ by Te6+ or W6+. Electron microscopy revealed a significant level of cation disorder in a severely-twinned sample of SrLa2Ni2TeO9; spin-glass and antiferromagnetic phases coexist below 35 K. The Ni2+ cations in CaLn2Ni2WO9 (Ln = La, Pr or Nd) form a spin glass, although the behaviour of each composition reflects the magnetic properties of Ln3+.

The primary aims of the thesis were to: (i) discover catalyst systems that maintained high α-olefin polymerisation activities in the presence of hydrogen while producing polymers with low molecular weights (Mw <10 kg mol−1) and (ii) find new single-site initiators for the ring-opening polymerisation (ROP) of lactide monomers. The thesis begins by offering a brief introduction to α-olefin and lactide polymerisation, including discussions on known polymerisation catalysts. The synthesis and characterisation of a series of well-defined group 4 ansa-bridged permethylindenyl complexes based on the Me2SB(CpR,I*)ZrX(Y) ({(η5-C9Me6)Me2Si(η5-C5H3R)}ZrX(Y) where R = H, Me and nBu) motif is then discussed. The application of these complexes as α-olefin polymerisation catalysts, both in solution-phase and when immobilised on a range of inorganic solid supports (MAO modified silica, MAO modified layered double hydroxide and solid MAO) is then detailed. It was found that solid MAO supported catalytic systems exhibited some of the highest slurry-phase polymerisation activities reported in the literature. The systems produced HDPE with minimal branching, uniform polymer morphology and low polymer molecular weights (Mw <100 kg mol-1 at 80 °C). A variety of polymerisation conditions were studied, including the effects of temperature, scale, pressure, scavenger, catalyst loading and time. The slurry-phase ethylene/1-hexene copolymerisation ability of the catalysts is then demonstrated. The effects of hydrogen on ethylene polymerisation activity and polymer properties are also discussed. The overall effect of 1-hexene was found to depend on the identity of the catalyst and the amount of co-monomer in the system. All catalysts demonstrated remarkable stability in the presence of hydrogen, which was accompanied by a significant decrease in polymer molecular weights to produce commercially viable polyethylene waxes. Finally, four unsymmetrical permethylindenyl zirconocenes are presented as initiators for the ROP of L-, D- and rac-lactide. The kinetics of polymerisation, overall rate equations and the effects of temperature, initiator concentration, scale and co-initiator concentration are discussed. A variety of techniques were used to characterise the polymers in order to deduce tacticity, molecular weights and chain end groups.

There is increasing interest in the role of materials with correlated structural disorder in mimicking the exotic properties exploited in electronic condensed matter phases. Spin ices, for example, are important class of frustrated magnets in which the spin configuration obeys the `two-in two-out' ice rules that govern proton order in water-ice. Such ice rules are implicated in a wide range of functional responses in different materials, from heavy-fermion behaviour to superconductivity. Ice-rules-obeying states are characterised by an absence of long range order, leading to a manifold of degenerate ground states, extensive residual entropy and exotic excitations; in spin-ices, these excitations correspond to topological defects in the form of effective magnetic monopoles. The main barrier to experimentation and application of these topological defects is the extremely low temperatures (~ 1 K) at which the spin-ice correlations develop. This thesis explores the structural ice analogue cadmium cyanide, Cd(CN)2, a cubic negative thermal expansion (NTE) material, in which the orientation of cyanide ions maps onto the spin orientation in spin-ices. Cd(CN)2 is shown here to display spin-ice physics at room temperature. Chapter 3 outlines the extreme sensitivity of Cd(CN)2 to X-ray irradiation, including unit-cell contraction, and the selection or suppression of particular phase transitions. These results explain earlier discrepancies regarding the phase behaviour and negative thermal expansion in Cd(CN)2 and motivated the development of a synthesis of isotopically-enriched 114Cd(CN)2 suitable for neutron scattering studies. The synthesis of Cd(CN)2 directly from Cd metal forms the basis of Chapter 4. The structure of previously-unreported intermediate phase, Cd(NH3)2[Cd(CN)4], is characterised, as well as its thermomechanical response. This represents the first variable-temperature study of this type of framework (PtS), shown to display anisotropic NTE and negative linear compressibility. The main result of this thesis is to demonstrate that by replacing the magnetic dipole in spin-ice with the electric dipole of the cyanide ion, cadmium cyanide displays spin-ice behaviour at temperatures nearly sixty times higher that in its magnetic analogue. I present the results of neutron scattering measurements on 114Cd(CN)2 along with density functional theory calculations, Monte Carlo simulations, total scattering and nuclear magnetic resonance measurements. Having confirmed the importance of spin-ice physics, chapter 6 explores the pressure and temperature dependence of the ice-like correlations. At least two phase transitions are identied at low pressure, kinetic trapping is observed and the extreme compressibility shown to be a function of cyanide reorientation and ice-like coordination. It is hoped that increase in energy scale, identified here, will enable further exploration that may shed further light on the physics of the spin and water-ices themselves.

This thesis describes the preparation of acyclic, macrocyclic, mechanically interlocked host molecules and cryptand-like structures exploiting halogen bonding for the recognition of anionic guests.

Indium-based transparent conducting oxides (TCOs) are widely used in optoelectronic devices. An important goal of this project is to search for TCOs that have reduced In content or indeed no In. The cheap zinc-based TCOs are good candidates to replace expensive indium-based TCOs in applications. A co-doping protocol has been established using both Si and In to obtain films with both good optical and electrical properties. This co-doping strategy can dramatically reduce the cost of the expensive element In while maintaining better optoelectronic performances compared to singly doped ZnO thin films. The spray pyrolysis technique is used to deposit TCO thin films, which is famous for its lower cost compared with physical deposition methods such as sputtering. I have studied the detailed properties of singly doped (Si or In) ZnO together with co-doped (Si and In together) ZnO thin films. I have also related their optoelectronic performances with structures, elemental compositions, and chemical environment to understand their properties in depth. It is the first time co-doped ZnO thin films based on Si and In have been successfully synthesised with high optoelectronic performances. Therefore, it is a basis for further development in co-doping and material design. The total chemical composition of elements in the bulk of a TCO material has not been measured previously. Nevertheless, I have studied these to see the limitations or restrictions in doping, thus understanding how doping affects optoelectronic properties including metal-insulator transition. Our ultimate goal is to develop an applicable deposition method and find suitable TCO materials to meet application requirements on both the optoelectronic performance and cost.

This Thesis describes the synthesis and characterisation of new alkaline earth metal and aluminium gallyl complexes. Experimental studies were performed to investigate their structure. The reactivity of these species was also studied. Chapter 1 introduces metal-metal bonded complexes containing alkaline earth metals and aluminium and the use of gallium(I) analogues of N-heterocyclic carbenes in the synthesis of heterobimetallic complexes of gallium. Chapter 2 describes the synthesis and reactivity of alkaline earth gallyl complexes supported by beta-diketiminate ligands. Chapter 3 presents the synthesis and reactivity of alkaline earth gallyl complexes supported by the carbazolide ligand CzOx. Chapter 4 describes synthesis of aluminium-gallium bonded complexes supported by amidinate and b-diketiminate ligands and the attempted study of their reactivity. Chapter 5 presents full experimental procedures and characterising data for the new complexes reported.

Chapter One provides an introduction to the chemistry of pentalene and its derivatives encompassing ligand synthesis, organometallic chemistry, and in particular ethylene polymerisation. In the second half, cationic polymerisation is introduced encompassing both main-group and transition-metal initiated polymerisations. The limitations of cationic ethylene polymerisation are highlighted. Chapter Two describes the synthesis of a series of related complexes based on the Pn*MCpR(X) motif for application as ethylene polymerisation catalysts. The products are characterised by NMR spectroscopy, single crystal X-ray diffraction, elemental analysis and, where relevant, EPR spectroscopy. Chapter Three details the application of aforementioned Pn*MCpR(X) complexes as ethylene polymerisation catalysts, tested in solution co-catalysed by methylaluminoxane, and in the slurry phase, immobilised on a variety of inorganic supports. Very high activities are observed for the zirconium congeners of this non-classic polymerisation motif, with the Cp ligand observed to affect activity more dramatically than the "X" ligand. Chapter Four gives an account of mechanistic investigations examining the activity of the Pn*MCpR(X) catalysts. Pre-catalyst activation studies implicate the formation of cationic derivatives, which are rationally synthesised. The unexpected activity of [Pn*ZrCp]+ towards ethylene polymerisation is investigated by in-situ gas uptake measurements and small molecule activation studies, which do not readily accommodate a coordination-insertion mechanism. An alternative cationic initiation mechanism is proposed and explored. Chapter Five describes the synthesis of titanium and zirconium hydride and deuteride complexes. Using either LiAlH4/D4 or H2/D2 as the hydrogen source, trimetallic hydride clusters are synthesised. Preliminary investigations into their reactivity with small molecules is presented. Chapter Six details the synthesis of reduced permethylpentalene titanium complexes. Chlorine atom abstraction, scrambling of the Pn* ligand, and dinitrogen activation was observed depending on the nature of the reducing agent and the stoichiometry employed. Chapter Seven provides experimental details and characterising data for the complexes presented in the preceding five chapters.