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Graphene is reported to possess a range of unique and highly desired properties and consequently has potential to revolutionise the field of electrochemistry if diligently employed as a new-generation electrode material. Graphene potentially represents the world’s thinnest electrode material, but there are experimental parameters to be overcome: the first problem is how to electrically wire/connect to the graphene sample(s) as to obtain the reported benefits; the second issue is how to reduce aggregation of graphene sheets back to their lowest energy conformation, that is, graphite, due to the strong π–π interactions between the graphene sheets; the third and final limitation is that various fabrication routes produce graphene to differing qualities, a factor that must be considered when exploring its fundamental electrochemical properties and electroanalytical implementation. This thesis reports on the fundamental electrochemical characterisation and resultant electroanalytical applicability of utilising graphene as a novel electrode material. The thesis consists of four key contributions, each developing on the knowledge gained from the previous. Chapters 1 through to 3 give an overview of the relevant fundamental electrochemical concepts with which this thesis is concerned. Chapter 4 provides a ‘snap-shot’ of the state of the graphene literature from 2010 (upon the commencement of this work), from which successive chapters follow the chronological development and investigation of graphene as produced through a variety of synthesis methods, gradually building a complete picture and understanding of the electrochemistry of graphene and the implications of its properties towards the fabrication and implementation of graphene as an electroanalytical sensor substrate. IV | P a g e Chapter 5 details the relevant experimental information and the full physicochemical characterisation of the various graphene materials utilised within this work. Chapters 6 and 7 utilise graphenes that are fabricated via a ‘top-down’ approach, which is most commonly employed in the literature, where in order to ‘connect to’ the graphene a liquid suspension is immobilised onto a suitable electrode surface. Chapter 6 uses surfactant-modified graphene and investigates, for the first time, the influence that such surfactants have on the observed electrochemistry. Chapter 7 uses pristine graphene in solution and considers; the aspects of various ‘coverages’ of graphene, the supporting electrode substrate, and how the formation of few and multiple layered graphene structures can influence the observed response. These parameters are overlooked within the current literature. Chapter 8 utilises graphene that is fabricated via a ‘bottom-up’ Chemical Vapour Deposition approach, which gives rise to high quality single layer graphene domains that, once efficiently ‘housed’ in order to connect to the graphene, allow the electrochemical exploration of monolayer graphene to be realised and be compared to quasi-graphene and defect abundant graphene structures for the first time. This approach allows the structure of graphene to be correlated with that of the electrochemical response for the first time. Critically, this work unambiguously demonstrates that the electrochemical response is edge plane like defect dependent. The final part of this thesis (Chapter 9) utilises a range of modified graphenes including novel three-dimensional (3D) structures (a graphene foam and graphene paste) and functionalised graphene (graphene/graphitic oxide), with the effects of said modifications explored towards the fundamental electrochemical and electroanalytical properties obtained. The first part of this chapter reports the electrochemistry of a novel freestanding 3D graphene V | P a g e foam and, for the first time, critically compares this to a freestanding 3D carbon foam alternative. It is demonstrated that the graphene foam gives rise to beneficial voltammetric responses in non-aqueous media, namely ionic liquids. This chapter also explores the use of a graphene paste electrode and demonstrates that the voltammetric response is no better than that of a graphite based paste electrode. Last, the use of graphene/graphitic oxide as an electrode material is explored and shown to give rise to unique voltammetric signatures, which are coverage dependant and can be utilised as a means of characterising the successful production of graphene through the reduction of graphene/graphitic oxide (as commonly utilised within the current electrochemical literature). Furthermore, it is shown that the unique voltammetry observed at graphene/graphitic oxide modified electrodes can be used beneficially for electrocatalytic processes. This thesis demonstrates that, within the graphene electrochemical literature, control experiments are often an overlooked comparison, which are needed for the electrochemical response of graphene to be understood and before the benefits of graphene can be claimed in such instances where superiority is ‘demonstrated’.

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This thesis is concerned with the investigation of transition metal (TM) ion complexation with hydrophilic membranes composed of copolymers of 4-vinyl pyridine & 4-methyl-4'vinyl- 2,2'-bipyridine with 2-hydroxyethyl methacrylate. The Cu(II), CoCII) & Fe(II) complexes with these coordinating membranes were characterised by a variety of techniques, in order to assess the effect of the polymer on the properties of the complex, and vice versa. A detailed programme of work was instigated into the kinetics of formation for the polymer-bound tris(bipyridyl) iron(II) complex; the rate and extent of complex formation was found to be anion-dependent. This is explained in terms of the influence of the anion on the transport properties and water content of the membrane, the controlling factor in the development of the tris-complex being the equilibrium concentration of Fe(II) in the gel matrix. A series of transport studies were performed with a view to the potential application of complexing hydrogel membranes for aqueous TM ion separations. A number of salts were studied individually and shown to possess a range of permeabilities; the degree of interaction between particular metal-ion:ligand combinations is given by the lag-time observed before steady-state permeation is achieved. However, when two TM salts that individually display different transport properties were studied in combination, they showed similar lag-times & permeabilities, characteristic of the more strongly coordinating metal ion. This 'anti-selective' nature thus renders the membrane systems unsuitable for TM ion separations. Finally, attempts were made to synthesise and immobilise a series of N ,0-donor macrocyclic ligands into hydrogel membranes. Although the functionalisation reactions failed, limited transport data was obtained from membranes in which the ligands were physically entrapped within the polymer matrix.

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Tetraazamacrocycles occupy a unique position in coordination chemistry, owing to their ability to form very stable complexes with a large range of metal ions. The inclusion of additional pendent coordinating groups is of particular interest, due to the effect on the properties of these compounds as ligands. The regioselective synthesis of N,N’-dialkylated-1,4,8,11-tetraazacyclotetradecane in positions 1,5-, 1,8- and 1,11- has been accomplished using different substituents, including the potentially coordinating 2-pyridylmethyl group. A number of synthetic strategies have been investigated. The functionalisation of the related, cyclic dioxotetramines, 1,4,8,11-tetraazacyclotetradecane-a,b-diones (a,b = 2,3, 5,7 and 5,12) at the amino nitrogens has also been carried out. The nickel, copper and chromium complexes of some of these ligands have been prepared and characterised. In several cases, solid state structures have been elucidated by X-ray crystallography, and have revealed a number of distinct and intriguing structural types and macro cyclecon formations. UV-Visible absorption spectroscopy, cyclic voltammetry and (forchromium) luminescence spectroscopy have been used to investigate the properties insolution. New octadentate ligands based on the 1,4,7,10-tetraazacyclododecane ring, tris-N-functionalised with acetate groups, have been synthesised, for preparation of water soluble lanthanide complexes of high thermodynamic and kinetic stability. In one class of ligand, the eighth donor atom is the carbonyl oxygen of a covalently-linked para-substituted acetophenone {-CH2C(0)C6H4-X, where X = H, OMe, NMe 2 }. Efficient sensitisation of europium(III) luminescence is observed following excitation of the acetophenone, with the para-substituent exerting a significant effect on the photophysical properties. In the second class, the macrocycle is connected through a three- or four-atom linker, containing a coordinating amide group, to a benzophenone moiety, found to act asan efficient sensitiser of both europium(ffl) and terbium(M) bound to the macrocycle. In both classes, lifetime measurements in H 20 and D20 reveal the presence of a water molecule occupying the ninth coordination site of the metal ion. In the third class, 8-benzyloxyquinoline has been linked to the macrocycle, through a single 2-methylene unit. In this system, the nitrogen of the aromatic group is appropriately positioned to bind to the coordinated metal ion. No additional water molecule is observed in this case, and it is proposed that this is due to the benzyloxy group successfully occupying the site normally taken by the water molecule.

The formation of transition metal nitrides is reviewed critically with special reference to newer production mechods and fabrication techniques. Crystal structures and types of bonding arc dircussed in relation to those of other nitrides and refractory hard metals generally, of borides, carbides and silicides. Information so far available on the sintering of materials is summarised for nitrides (as with borides and carbides), the sintering is influenced by additives and impurities such as oxides formed by partial hydrolysis and oxidation. Resistance to oxidation is increased by sintering and hot-pressing the refractories. is formed to give stable oxide layers. The sintering of the oxides is controlled by surface diffusion promoting grain-boundary penetration at lower temperatures (above about 1/3 mp oxide in k) and crystal lattice diffusion at higher temperatures (above Tammann Temperature, about 1/2 mp oxide in K). Comparison of the oxidation of nitrided and free metals indicates that oxide sintering i s inhibited sometimes by removal of nitrogen but accelerated occasionally by the remaining metal.

This thesis describes work on three families of low-dimensional chalcogenides. The Jamesonite-Benavidesite series has been investigated to observe the effects of chemical substitution as iron is replaced by manganese. A series of materials with the general formula Fe1‑xMnxPb4Sb6S14 (0 ≤ x ≤ 1) has been synthesised for analysis. Structural investigations of the highly anisotropic structure using powder neutron diffraction have been performed at temperatures from 2 K up to room temperature. The magnetism has been studied with low temperature powder neutron diffraction and SQUID magnetometry. Benavidesite (x = 1) has been shown to have antiferromagnetic order at 2 K with moments of 2.58(9) μB. The electrical transport properties indicate materials are p-type semiconductors with activation energies in the range 177.2 meV to 626 meV. Work on a cobalt Shandite series, Co3Sn2-xInxS2 (0 ≤ x ≤ 2), enables tuning of the Fermi level within narrow Co d-states. This results in a compositionally induced double metalto- semiconductor-to-metal transition and manipulation of the electronic and thermal transport properties. A narrow semiconducting region exists between compositions of 1 ≤ x ≤ 1.05. There are two main group sites in the structure: one in an intra-layer trigonal antiprismatic site and one in a kagome layer. Powder neutron diffraction has been used to investigate ordering of indium and tin across the two main-group sites. X-ray Photoelectron Spectroscopy and 119Sn Mössbauer spectroscopy have been used to determine the oxidation states of the elements in the material. Results suggest that cobalt, tin, indium and sulphur are all in the 0 oxidation state. The thermoelectric properties have been measured and the figure of merit for Co3Sn1.2In0.8S2 and Co3Sn1.15In0.85S2 (ZT = 0.28) are the highest reported for a sulphide at 425 K. The sulphide In2Sn3S7 has been prepared as a bulk polycrystalline phase for the first time. Powder neutron diffraction has been undertaken to study partial ordering of tin and indium over the MS6 (M = Sn, In) octahedral sites within the structure. Sites were observed to contain approximately two-thirds indium and one-third tin. The structural analogue Cr2Sn3Se7 has also been synthesised. The electrical resistivity, Seebeck coefficient and thermal conductivity have been measured for both samples. The previously unreported Cr2Sn3S7 phase (Space Group: P21/m, a = 11.2945(6) Å, b = 3.6456(2) Å, c = 12.2473(7) Å, β = 105.352(2) °) has been synthesised as well as a new ternary chromium tin selenide with the approximate stoichiometry Cr2Sn5Se11.

Iron-catalysed cross-coupling chemistry is undergoing a renaissance due advantages in cost, toxicity and abundance compared to traditional cross-coupling catalysts. In Chapter 2 it is shown that expensive, synthetically challenging bis-phosphines used in the iron-catalysed cross-coupling of alkyl halides and arylboronic acid pinacol esters can be replaced in many cases with simple iron salts in phosphine-free procedures. More challenging substrates require the use of cheap, widely available bis-phosphines such as dppe (l,2-bis(diphenylphosphino)ethane) or dppp (1,3- bis(diphenylphosphino)propane). An EPR spectrum of the reaction mixture shows the presence of previously reported iron(l) complex [FeBr(dppehL which is the likely resting state in the catalytic cycle. Kinetic studies indicate oxidative addition of the alkyl halide via single-electron transfer to a three-coordinate iron species to be the rate-determining step. Having demonstrated that the key feature for facilitating iron-catalysed Suzuki coupling is the activation of a boronic acid pinacol ester with an organometallic nucleophile, in Chapter 3 it was shown that this form of activation could be applied to bis(pinacolato)diboron, allowing the iron catalysed borylation of alkyl, allyl, benzyl and, to a lesser extent, aryl halides. A unique, low-valent, phosphine-supported iron-boryl complex, [Fe(Bpin)(dpbzhL (pin = pinacolato) was isolated from the reaction of [FeCI₂(dpbz)₂] (l,2-bis(diphenylphosphino)benzene) and Li[B₂pin₂(¹Bu)], however this complex failed to react in stoichiometric reactions with 1- bromobutane, reflecting the finding that excess phosphine greatly retards the rate of ironcatalysed borylation. The uniqueness of these low-valent iron-boryl intermediates provided an opportunity to investigate new forms of catalysis based on these complexes. Chapter 4 describes attempts to catalyse the boryl/electrophile difunctionalisation of styrene using Li[B₂pin₂(¹Bu)) and iron precatalysts. It was found that stoichiometric iron is capable of mediating the boryl protonation of styrene; however attempts to trap the organometallic intermediate proved fruitless, and deuterium labelling studies were unable to determine the origin of the a-hydrogen in the resultant product. In order to expand the utility of iron-catalysed cross-coupling, in Chapter 5 attempts to couple electrophiles ·derived from enantiomerically pure l,2-amino alcohols are described. A range of electrophiles including l,2-amino halides, cyclic sulfamidates, oxazolidinones, and oxazolinethiones were screened for activity in iron- and nickel-catalysed cross-coupling; however none of these furnished the desired products.