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This thesis deals with the synthesis and study of new electro-active compounds in order to improve understanding of controlling supramolecular interactions between host-guest systems in solution and at the solid-liquid interface ofa conducting polymer backbone. ..... Firstly, a series of flavin functionalised electrodes has been produced by immobilisation of flavin units as an electropolymerised thin film. We have shown that thin films of the flavin polymer can be deposited onto an electrode surface and that electrochemically controllable hydrogen bonding interactions can occur between the pendant flavin units and diaminopyridine units in solution. Electrochemically tuneable flavin-functionalised C60 derivatives have been synthesised and the redox-modulator role of hydrogen bonding interactions with diamidopyridine derivatives has been studied. We have shown that the attachment of the flavin unit onto C60 does not interfere with the ability of the flavin to undergo hydrogen bonding interactions with diamidopyridine. Moreover, hydrogen bonding interactions between the flavin and diamidopyridine units influences the redox properties of the C60 derivative. We have developed an attractive model system for flavoenzymes that have the cofactor directly attached to the apoenzyme,.by producing a flavin unit that is covalently linked to a diamidopyridineunit. The model compound self-assembles into an intramolecularly hydrogen bonded complex both iIi solution and the solid-state. The addition of an external stimulus disassembles the intramolecular hydrogen bonded complex. A CBPQr+ -based rotaxane has also b~en synthesised and electropolymerised onto an electrode surface by oxidative polymerisation of the 2,5-dithienylpyrrole stopper units. We have shown that the rotaxane can be deposited onto a surface. However, electrochemical measurements show that submonolayer coverage occurs. Finally, we have synthesised a range of new flavin building blocks. We have investigated the attachment ofone ofthese systems onto a diamond surface.

In the last decade, the study of nanoparticle (NP) systems has become a large and interesting research area due to their novel properties and functionalities, which are different from those of the bulk materials, and also their potential applications in different fields. It is vital to understand the behaviour and properties of nano-materials aiming at implementing nanotechnology, controlling their behaviour and designing new material systems with superior performance. Physical characterisation of NPs falls into two main categories, property and structure analysis, where the properties of the NPs cannot be studied without the knowledge of size and structure. The direct measurement of the electrical properties of metal NPs presents a key challenge and necessitates the use of innovative experimental techniques. There have been numerous reports of two/four point resistance measurements of NPs films and also electrical conductivity of NPs films using the interdigitated microarray (IDA) electrode. However, using microwave techniques such as open ended coaxial probe (OCP) and microwave dielectric resonator (DR) for electrical characterisation of metallic NPs are much more accurate and effective compared to other traditional techniques. This is because they are inexpensive, convenient, non-destructive, contactless, hazardless (i.e. at low power) and require no special sample preparation. This research is the first attempt to determine the microwave properties of Pt and Au NP films, which were appealing materials for nano-scale electronics, using the aforementioned microwave techniques. The ease of synthesis, relatively cheap, unique catalytic activities and control over the size and the shape were the main considerations in choosing Pt and Au NPs for the present study. The initial phase of this research was to implement and validate the aperture admittance model for the OCP measurement through experiments and 3D full wave simulation using the commercially available Ansoft High Frequency Structure Simulator (HFSS), followed by the electrical characterisation of synthesised Pt NP films using the novel miniature fabricated OCP technique. The results obtained from this technique provided the inspiration to synthesise and evaluate the microwave properties of Au NPs. The findings from this technique provided the motivation to characterise both the Pt and Au NP films using the DR technique. Unlike the OCP technique, the DR method is highly sensitive but the achievable measurement accuracy is limited since this technique does not have broadband frequency capability like the OCP method. The results obtained from the DR technique show a good agreement with the theoretical prediction. In the last phase of this research, a further validation of the aperture admittance models on different types OCP (i.e. RG-405 and RG-402 cables and SMA connector) have been carried out on the developed 3D full wave models using HFSS software, followed by the development of universal models for the aforementioned OCPs based on the same 3D full wave models.

An electrochemical approach has previously been described for the selenenylation-deselenenylation of alkenes using diphenyl diselenide. The use of electrochemistry enabled diphenyl diselenide to be used in catalytic amounts to convert alkenes into allylic ethers. i 10 mol% (PhSe)2 Electrolysis OMe The electrochemical use of diselenides bearing a chiral side chain has now been investigated. The initial investigations involved the use of diphenyl diselenide, in conditions which varied considerably from those described previously in the literature. By using just 10 mol% diphenyl diselenide, the conversion of alkene A into allylic ether B was achieved in 91% yield. OMe PhAArn, 10 mol% (ArSe)2 Ar=Ph 91% yield Ph CO₂Me - Ph C02Me Ar=Chiral 55% yield Electrolysis A B Having established viable conditions using diphenyl diselenide, a range of chiral non-racemic diselenides was now used for the same conversion. Mixed results were obtained, with yields of B ranging from 19% to 55% and selectivities ranging from 0% to 69% ee. The reaction of several chiral diselenides was investigated in depth and a likely mechanism for the addition elimination sequence proposed. The investigation was widened to include more alkenes and different reaction conditions, though no alkenes proved as ideal a substrate as A. In an attempt to improve the efficiency of these electrochemical reactions, the synthesis of novel diselenides incorporating new design principles was undertaken, resulting in the synthesis of diselenide C which provided the highest selectivity in the electrochemical reaction.

This thesis describes exploratory synthetic, structural and electrochemical studies into the molecular and electronic structures of arylamine based hole transporting materials. The principle objectives in these studies were to increase understanding of the electronic structures of the materials involved and to investigate the effect of various substitution patterns on the chemical stability and electronic structure of these materials.

In the present thesis, I discuss some of the current advances in research in the field of the solid state science of fullerenes. The reaction of C60 with alkali metals using both conventional solid state and low temperature solution-based synthesis techniques has led to the production of fulleride salts with interesting structural and superconducting properties. In superconducting A3C60 systems, it has been widely reported that Tc increases monotonically with interfulleride separation. Of particular interest is the family Na2Rb1-xCsxC60 (0 ≤ x ≤ 1) as they display a much steeper rate of change of Tc with interfulleride spacing. Here we discuss the related family of quaternary fullerides, Na2-xKxCsC60 in an attempt to explore the consequences of this trend and produce fulleride salts with elevated Tc's In addition, the monotonic increase in Tc with increasing interfulleride separation has driven attempts towards the synthesis of new superconducting fullerides with very large lattice parameters. A key material among the A3C60 systems is the end member, Cs3C60, which has remained elusive in attempts to synthesise it by traditional solid state techniques due to the thermodynamic instability of this phase caused by the accommodation of the large Cs+ ion (r = 1.67 Å) in the small tetrahedral holes (r = 1.12 Å). Here we report the synthesis of “FCC rich” and "A15 rich" samples of the series, RbxCs3-xC60 (0.0 ≤ x ≤ 0.5) via low temperature synthetic techniques utilising the solvents ammonia and methylamine, respectively. This allowed us to study the effects of both chemical (by partial substitution of Cs+ by the smaller Rb+ cation) and physical pressure upon the electronic and superconducting properties of these materials. For all samples, detailed structural studies have been performed using synchrotron X-ray powder diffraction and magnetic behaviour using SQUID magnetometry techniques.

Recognition of chiral molecules in biological assemblies has been a subject of extensive research. The aim of this work was to fabricate and characterise biocompatible composite materials suitable for chiral recognition. Collagen, the most abundant chiral, extracellular protein, was chosen as a possible matrix. The chiral recognition properties were evaluated by a comparative study in collagen, collagen incorporated in tetramethyl orthosilicate (TMOS) and TMOS. In electrochemical studies, ferrocene was incorporated to facilitate electron transfer. The recognition characteristics of two chiral enzymes, L-lactate oxidase and D-glucose oxidase were tested using circular dichroism (CD), Fourier Transform Infra-Red (FTIR) spectroscopy and electrochemical methods. A surprising result revealed an inversion of chiral selectivity. The effect of various parameters such as immobilisation, temperature, chemical modification, solvent systems, on enantioselectivity is well known. Stereoinversions caused by the ‘sergeants and soldiers’ effect in gel-forming p-conjugated molecules caused by co-assembly has been reported by several groups. The inversion of stereoselectivity observed in this study is probably due to a combination of the microenvironment and electrostatic interactions of the enzyme, mediator and substrate with the chiral collagen matrix. The results may have important implications for biosensing, asymmetric syntheses and understanding the nature of chiral interactions in biological systems.

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The macroscale electrochemical theory breaks down with microstructures smaller than the dimensions of the diffusion layer, showing that such electrodes have significant quantitative effects and qualitative advantages. The great advantage of microelectrodes over macroelectrodes is the minimisation of interference, which gives rise to much lower detection limits. Microelectrodes have much reduced ohmic drops and capacitive effects and can be used in the absence of supporting electrolyte. These features have opened a growing interest in the fabrication and application of microelectrodes in various areas. There are different microelectrode geometries, but disc type is the most used. Microelectrode arrays have been proposed as a way of increasing the magnitude of the current (produced for a single microelectrode), while maintaining the advantages of the single microelectrode. Although the inlaid microdisc microelectrode can be considered as one the most popular microelectrode geometry, there is also a need to consider conical recessed, recessed and protruding microdiscs as photolithographic microfabrication techniques often result in non-ideal geometries. It has been proved using surface imaging techniques such as scanning Kelvin nanoprobe (SKN), scanning electron microscopy (SEM) and white light interferometer microscopy that conical recessed electrodes with gradient potential along the recessed walls are formed during standard photolithographic methods for producing microelectrode arrays. Microarrays are ubiquitously used for high-throughput measurements using various signal transduction techniques. Ideally each sensor in a microarray platform should perform optimally to ensure an error free response. In this thesis, a simple method for designing a microelectrode array platform (MEA) is described, allowing a ‘defective’ cluster of sensing arrays to be easily identified. It is possible to extend this concept for multiple analyses on a single chip. Molecular electronic is a promising technology which would be an alternative. The concept of molecular electronics is the use of single molecules or arrays, or layers of molecules for the fabrication of electronic components such as wires, switches, and storage elements. Indeed, functionalised thiol monolayer-based microelectrode array may provide unique possibilities, facilitating electrochemical measurements involving electron transfer via electron tunnelling. The conjugated structure of rigid, linear molecule increases greatly the rate of electron transfer across the monolayer. Charge transfer and self-assembly characteristics of novel fully conjugated molecules molecular wires (synthesised at the Department of Chemistry and Centre for Molecular and Nanoscale Electronics, Durham University) assembled on flat gold electrodes are evaluated using Marcus model of electron-transfer and tunnelling theory. The behaviour of these wires is compared with heptanethiol and dodecanethiol SAMs. A preliminary study for application of self-assembled monolayer of molecular wires in microelectrode arrays for multiple analyses on a single chip has been successfully reached.

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