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The application of organic materials in electronic devices depends, in part, on the ability to control the electrical properties by structural modification. This thesis explores the possibility of modifyng the properties in the cofacially stacked polymeric phthalocyanine, fluoroaluminium phthalocyanine (AIPcF) by copolymerisation with the structurally related fluorogallium phthalocyanine (GaPcF). Copolymers of AIPcF and GaPcF of composition 2:1,1:1 and 1:2 were prepared for the first time. The purification, chracterisation, and evaluation of the 1:1 copolymer were carried out. It was found that the material could be purified by entrainer sublimation without major change in the composition. The polymeric nature of the material was established through spectroscopic methods, thermogravimetric analysis and X-ray powder diffraction. Evaluation of evaporated copolymer films by XPS, depth profiling by argon ion bombardment, and electron bombardment largely confirmed the expected composition but indicated that a limited amount of fractionation or selective decomposition had occurred. A detailed study of the properties of compactions and films by a.c. and d.c. show that the copolymer is intermediate between the monomers in its properties, and different from the mixture of the monomers. The a.c. measurements suggest that the films of both pure materials and copolymer have a higher imperfection concentration than the compaction. Two preliminary studies are also reported. Iodine doping of the copolymer leads to high conductivity which is limited by disorder. The photoconduction response of the copolymer is higher than that of either component, suggesting copolymerisation as a means of enhancing this property. The successful synthesis of this copolymer offers a route to the copolymerisation of electrically dissimilar materials as a means of enhancing the conductivity in linear chains.

The interactions of biological molecules are traditionally investigated using ensemble techniques. These provide information on the molecular behaviour based on averaged data resulting from collective ensemble properties. While this has enabled the resolution of structure and function of many proteins and other biomolecules, an understanding of how and why the molecules go about structural changes and modulate inter- and intra-molecular interactions is difficult to gain using these approaches. More recently, single molecule techniques have evolved. These allow us to follow the behaviour of the individual molecules over time and/or under changing conditions. From such data, subtle molecular changes can be resolved without the need to synchronise the system. Further, variations within a biological system can be detected which would be lost using the ensemble techniques, due to the concomitant averaging procedures. This is exploited to help understand the molecular procedures involved. In this thesis, the application and comparison of two of the main single molecule techniques, optical tweezers and AFM, are described. With these, a range of systems was investigated; namely drug-DNA, protein-DNA, and cell adhesive interactions. The presented results provide new and complementary information on the different biological systems, demonstrating the diversity of single molecule applications. The combination of different experimental approaches was further exploited to gain a more complete picture of the observed processes.

The gas-phase, thermal hydrogenations of propene and cyclopropane over various titania-supported metal catalysts have been investigated. Catalysts were prepared either by a photodeposition or a thermal reduction method. Absolute initial hydrogenation rates were calculated from total gas pressure vs time measurements. The activities of all catalysts were found to be very dependent upon catalyst state, as modified by reductive or oxidative pretreatments. These results are discussed in terms of reversible strong metal-support interactions, initiated via hydrogen spillover. For 0.5 %mass Pt on Ti02, the order of reaction with respect. to hydrocarbon was 0.5. An adsorption mechanism involving the alkylidene species is proposed as one possible explanation of this result. A negative order of reaction with respect to hydrogen was recorded. A Langmuir-Hinshelwood mechanism, involving competitive adsorption of hydrocarbon and hydrogen at supported metal sites, is proposed. Differences in behaviour between catalysts prepared by photodeposition and the thermally-prepared catalyst were observed during the hydrogenation studies. These include different apparent activation energies, maximum reaction rates at differing propene: hydrogen ratios and irreversible degradation of all photodeposited catalysts during cyclopropane hydrogenation. These differences are taken as being strongly indicative of differences in supported metal morphologies, arising as a consequence of the preparative routes employed. Temperature programmed desorption and scanning electron microscopy studies were undertaken in an attempt to establish and characterise these potential morphological differences. Although the results of these studies were, at best, inconclusive, the possible nature of such supported metal morphological differences is discussed on the basis of available evidence generated within this and other, similar, studies. The liquid-phase photocatalytic dehydrogenation of propan-2-ol, using the same catalysts, was also briefly investigated. Variations in measured activation energies suggest that photodeposited catalysts in the 'as prepared' state are contaminated with variable levels of impurity residues, particularly chloride ions.

The work, which is reported in this thesis, is concerned with the photochromic processes, or light induced changes of colour displayed by the hexaaryl bi-imidazolyl system. The thesis includes a study of the solid state photochromic decay reaction, in which the colour change is brougnt about by the dimerisation of triphenyl imidazolyl radicals. Equipment, used in conjunction with a U.V./visible spectrophotometer, was assembled to allow the process to be followed at various temperatures and from the data accrued a kinetic scheme, based upon a diffusion controlled reaction involving a radical-dinier complex species, has been suggested. Investigations were also carried out into. the photochromic processes of the bi-imidazolyl system in benzene solution. Based on earlier observations, the work included the study of the effect of variation of the parent dimer concentration upon the generation and decay kinetics of the triphenyl imidazolyl radicals and the related radicals fluorinated on the 2 phenyl ring. Kinetic schemes, most of which have necessarily involved a postulation of radical-dimer complexes of some sort, have been formulated for each radical system at each dimer concentration used. Rate constants for the reactions have been given. The electron spin resonance spectra for the three fluorinated derivatives of the triphenyl imidazolyl radical have been reported. Assignment of the splitting constants was attempted by use of simple Hückel molecular orbital calculations but this proved largely unsuccessful. Accurate theoretical reproduction of the experimental spectra was thus not achieved. It was decided, that Hückel was in too many ways unsatisfactory for the system, and work on an alternative, more complete molecular orbital approach (that of Pople, Pariser and Parr) was initiated. A computer program was obtained to permit such calculations to be made, and although not all problems had been overcome by the end of the time allowed for this thesis much headway had been made, and guide lines for further work have been suggested.

A complex array of intermolecular forces controls the interactions between and within biological molecules. The desire to empirically explore these fundamental forces has led to the development of several biophysical techniques. Of these, the atomic force microscope (AFM) and the optical tweezers have been employed throughout this thesis to monitor the intermolecular forces involved in biomolecular interactions. The AFM is a well-established force sensing technique capable of measuring biomolecular interactions at a single molecule level. However, its versatility has not been extrapolated to the investigation of a drug-enzyme complex. The energy landscape for the force induced dissociation of the DHFR-methotrexate complex was studied. Revealing an energy barrier to dissociation located ~0.3nm from the bound state. Unfortunately, the AFM has a limited range of accessible loading rates and in order to profile the complete energy landscape alternative force sensing instrumentation should be considered, for example the BFP and optical tweezers. Thus, this thesis outlines the development and construction of an optical trap capable of measuring intermolecular forces between biomolecules at the single molecule level. To demonstrate the force sensing abilities of the optical set up, proof of principle measurements were performed which investigate the interactions between proteins and polymer surfaces subjected to varying degrees of argon plasma treatment. Complementary data was gained from measurements performed independently by the AFM. Changes in polymer resistance to proteins as a response to changes in polymer surface chemistry were detected utilising both AFM and optical tweezers measurements. Finally, the AFM and optical tweezers were employed as ultrasensitive biosensors. Single molecule investigations of the antibody-antigen interaction between the cardiac troponin I marker and its complementary antibody, reveals the impact therapeutic concentrations of heparin have up on the association and dissociation of the complex. In the thesis the AFM and optical tweezers independently provide complementary data towards the understanding of biomolecular interactions.

This thesis describes investigations towards the self-assembly of heterocyclic amino acids to form cyclopeptides, including the natural products dendroamide A and nostacyclamide. The Introduction highlights a variety of different natural products including the lissoclinum cyclopeptides and other oxazole and thiazole based natural products. The conformation of the lissoc1inum cyclopeptides and the affect different substituents have on their conformation is explored. The ability of a variety of natural products to chelate metal ions and the evidence for metal ion chelation within the lissoclinum cyclopeptides is also discussed. The Introduction is concluded with a statement of the aims and objectives of our research. The Results and Discussion section of the thesis details the development of a novel cyc1ooligomerisation reaction of heterocyclic amino acids. This cyc1ooligomerisation is applied to the self-assembly of thiazole and oxazole amino acids to form analogues of naturally occurring cyc1opeptides. The protocol is then extended to the self-assembly of the natural products dendroamide A and nostacyclamide. Additionally the ability of metal ions to act as templates and promote the formation of particular products is illustrated throughout these studies. Detailed discussions are also presented within this section into the methods for thiazole and oxazole formation. The third part of the thesis is the Experimental section containing full details of the preparative work completed and listing spectroscopic and analytical data on all new compounds synthesised during this study.

The research described in this thesis was conducted over a total of three years during the period October 1990 to October 1994, and is the sole work of the author, unless indicated otherwise by reference. A series of mildly dealuminated Y zeolites has been prepared by hydrothermal treatment using a low partial pressure of water vapour. These materials, together with samples previously dealuminated under more severe conditions, were characterised by the temperature programmed desorption of ammonia and the catalytic activity for suitable test reactions. Advances in technique permitted simultaneous monitoring of both the deammoniation and dehydroxylation processes. Interesting features were observed in the dehydroxylation traces which were related to changes in the acid site strength and amount of extraframework aluminium. The activity for both n-hexane cracking and toluene disproportionation reaches a maximum, corresponding to a framework concentration of 25-30 structural aluminium atoms per unit cell, consistent with the maximum number of strong acid sites. Slight deviation from this behaviour was noted, with the mildly steamed catalysts having lower activities than would be expected on the basis of their framework compositions alone. An in-depth analysis of the cracking of n-hexane has revealed that the extent of reaction is also critically dependent on the density of the available acid sites, which is explained in terms of the reaction mechanism. The disproportionation of toluene has highlighted differences in the nature of the extrastructural aluminium. The catalytic activity of the materials is either decreased or enhanced on extraction depending on whether the catalysts have been prepared by mild or severe dealumination. Variations in product distribution with time on stream have been observed and accounted for by changes in the reaction. The lifetime and activity profile of the catalyst could be altered by exposure of the catalyst to small amounts of toluene prior to the main reaction. This supports the concept of active coke enhancing this reaction. Cumene dealkylation was found to proceed on weaker acid sites than the cracking of n-hexane and the disproportionation of toluene, although a maximum in activity was still observed. This indicates that the weakest sites are not capable of catalysing this reaction, and that some heterogeneity of site strength exists between strong and weak acid sites. The dehydration of propan-2-01 was confirmed as a reaction which assesses the total number of acid sites, regardless of strength. However, changes in the selectivity of the products with the strength of the acid sites were found, implying that the formation of di-isopropylether is favoured by strong sites. Deliberate coking of the catalyst surface by exposure to propan-2-01 at elevated temperatures was found to increase the measured activity, in addition to changing the selectivity almost entirely in favour of propene. Extraframework aluminium was found to play an important role in all of the reactions studied. This emphasises the view that although structural aluminium has the larger influence on the overall activity of a catalyst for a particular reaction, the nature of the extraframework aluminium cannot be overlooked.