A series of unsymmetrical xylenyl-backboned diphosphine ligands are reported: o-C6H4(CH2ptSU2)(CH2PRR'), R = Ph, R' = 2-Py (L1) and O-C6H4(CH2ptSU2)(CH2PR2), R = 2-Py (L2), R = 2-(3-Me-Py) (L3), R = 2-(4- Me-Py) (L4), R = 2-(6-Me-Py) (Ls) and R = 2-Pyrim (Ls). The ligands have all been characterised by 31p, 1H and 13C NMR spectroscopy and high resolution mass spectrometry. Studies of [PtCI(CH3)(L)] and [PdCI(CH3)(L)] (L = L1-LS) have shown that the favoured isomers have the more strongly a-donating CH3 ligand trans to the bulkier ptSU2 donor. Studies with [PdCI2(L)], [PtCI2(L)] and [Pt(CH3h(L)] (L = L1-LS) show that the donor strength of the two phosphorus centres is not averaged in these complexes, in contrast to the related complexes of o-C6H4(CH2ptSu2)(CH2PPh2) (TP). These complexes have been characterised by a combination of NMR spectroscopy, high resolution mass spectrometry, elemental analysis and X-ray crystallography. The coordination chemistry of PR3, R = 2-(3-Me-Py), R = 2-(4-Me-Py), R = 2-(6-Me-Py), with LiCI and LiSr is also reported. Tripodal coordination to lithium by the three pyridyl nitrogen donors is detected for each ligand. These [LiX(PR3)] complexes have been characterised by 31p, 1H and 13C NMR spectroscopy and X-ray crystallography. Protonation studies with [PdCI2(L)] and [PtCh(L)] (L = L1-LS) suggest that the pendant pyridyl and pyrimidyl groups of L1-LS are protonated in methanolic solutions when treated with acids such as HSF 4, CH3S03H (MSA) and CF3C02H (TFA). The evidence for protonation came from 31p NMR spectroscopy and X-ray crystallography. Protonation studies with [Pt(CH3h(L2)] have shown that tridentate coordination of platinum by L2 (through both P donors and one pyridyl N donor) occurs. Catalysts derived from the new ligands were tested in the palladiumcatalysed methoxycarbonylation of ethene. The systems based upon L1, L2, L4 and Ls are shown to be active and selective for the production of methyl propionate (MeP) over polyketone (PK). Those derived from L2 and Ls are comparable in activity to the best reported system (which is based upon o-C6H4(CH2ptSU2h, dtbpx) when promoted by the strong acid MSA. The L2 and Ls systems are more active than dtbpx with the weaker acids TFA and PA. Complexes derived from L3 and Ls are inactive in methoxycarbonylation catalysis. Catalysts derived from L1-LS are also shown to be active in palladium-catalysed styrene methoxycarbonylation. Mechanistic studies suggest that catalysts derived from L2 produce MeP following the hydride mechanism. Competition between the coordination of palladium by the nitrogen donor of a pendant pyridyl group and acid anions was observed under catalytically relevant conditions. Complexes derived from L3 appear to be inactive in MeP catalysis due to persistent tridentate coordination of palladium (via the two P donors and one pyridyl N donor) blocking substrate coordination. Complexes derived from Ls may be inactive in MeP catalysis due to the electron deficient nature of the PPyrim2 donor. Carbonylation studies with isotopically labelled 13CO support the conclusion that MeP preference is a balance between kinetic and thermodynamic influences - the minor palladium-ethyl complex isomer may react faster to generate the more stable palladium-acyl isomer.

The synthesis of polyethylene terephthalate (PET) has been comprehensively reviewed. Various catalyst compounds based on zinc with different chelating ligands have been synthesized and structurally characterized. All were trialled in PET synthesis and compared with the standard antimony catalyst in both melt and solidstate polymerizations. Among those exhibiting some activity, zinc catechol acetate showed higher catalytic activity, optical clarity and lower colour and DEG content than standard. All zinc compounds were slower than the standard in the solid-state polymerization. Thermal characterization of the polymer samples by DSC showed comparable T g and slightly lower T m for zinc catalysts polymers compared with antimony. Thermogravimetric analysis (TGA) revealed higher thermal stability of the polymer catalyzed by zinc complexes. A part of the work was to synthesize a new nitrogen containing ligand to prevent intermolecular binding and promote solubility. Though the desired compound was not obtained, a new I-pot reaction in which four new bonds were made has been discovered. Study of the mechanism of catalyzed PET polymerization through model molecules was marred by difficulties in formation of crystalline complexes of them with zinc. PET -Clay catalysis and nanocomposite have been investigated. A naturally occurring clay sample was modified with zinc ions and/or quaternary alkyl ammonium salts and tested for catalysis and Clay-PET nanocomposite formation. The zinc-organic modified clay showed catalytic activity higher than antimony. Discoloration as normal in polymer-clay nanocomposite systems was observed. Dispersion of the clay in the PET matrix was investigated by W AXD, SEM and TEM and demonstrated as having partially exfoliated layers. Gas permeability of the nanocomposite showed only minor improvement due to incomplete exfoliation, lack of orientation of intercalated layers, and higher DEG content. Thermal properties by DSC showed a reduction in T g and significant reduction in Tm, also due to the higher DEG content (6.39%). TGA results showed a comparable thermal stability between the nanocomposite and the neat sample. Mechanical properties were investigated. The PET-Clay sample exhibited ca. 9% higher flexural modulus compared with the standard sample, and a reduction ca. 30 and 34% in the storage modulus and loss modulus respectively due to the higher content of DEG.

Chapter one contains a brief resume of the recent literature reports concerning the Dotz benzannulation reaction and a short review on the current known reactivity and use of vinylidene complexes. Chapter two describes the Dotz benzannulation reaction, regiochemically and mechanistically. The annulation reaction was applied to the synthesis of the steroid, taxodione. The annulation is also further applied to the synthesis of tricyclic systems. The tricycles formation being via a tandem annulationMitsunobu cyclisation process. The tricyclic systems potentially lead to the formation of aflotoxin Bl. Chapter two also describes the Dotz cyclisation reaction, its origin and mechanistic understanding. The cyclisation reaction was applied to the novel homochiral synthesis of (R, Z)-5-(I-decenyl)dihydro- 2(3H)-furanone and to the synthesis of (+/-)-muricatacin. Chapter three describes the experimental procedures used.

section I of this thesis contains a brief resume of the recent literature reports concerning the chemistry of Fischer Carbene Complexes. The latter part of the review discusses the mechanism of the Dotz benzannulation reaction. section II describes the author's own work, relating to the use of Fischer Carbene Complexes in organic synthesis. The main objectives of the research undertaken were to investigate the synthetic potential of the Shapiro/Dotz benzannulation sequence in natural product synthesis. Initial model studies involved the synthesis of 4-ethoxy-3-methoxy-2- (1' -methylethyl)- 5,6,7,8-tetrahydronaphth-l-ol and 3-methoxy-2-(1'- methylethyl)-5,6,7,8-tetrahydro-l,4-naphthoquinone from pentacarbonyl( ethoxycyclohex-l-enecarbene)-chromium (0) and 1- methoxy-3-methylbut-l-yne.pentacarbonyl(ethoxycyclohex-l-ene carbene)-chromium (0) was prepared by Shapiro chemistry from cyclohexanone 2,4,6-triisopropylbenzenesulphonyl hydrazone.

The phase relations in three oxide systems; ZnO–BiVO4, Pb2V2O7–BiVO4 and PbO– BiVO4, have been studied and their phase diagrams over the whole component concentration range up to 1273 K have been established. As a result of solid-state reaction between ZnO and BiVO4 mixed at a molar ratio of 2:1 or among ZnO, V2O5 and Bi2O3, mixed at a molar ratio of 4:1:1, a new double vanadate BiZn2VO6 has been obtained. Its crystallographic system was determined, its unit cell parameters were calculated and its incongruent melting temperature was established. A new compound is also formed in the Pb2V2O7–BiVO4 system. It has been shown that BiVO4 and Pb2V2O7 react with each other forming a compound of the formula Pb2BiV3O11, when their molar ratio is equal to 1:1, or between PbO, Bi2O3 and V2O5, mixed at a molar ratio of 4:1:3. This material melts congruently and it crystallises in the triclinic system. A new series of non-stoichiometric sulphides Ga1-xGexV4S8 (0 x 1) has been synthesised by standard solid-state reaction. The samples have been characterised by powder X-ray and neutron diffraction, SQUID magnetometry and electrical transportproperty measurements. Structural analysis reveals that a solid solution is formed throughout this composition range. Magnetic measurements suggest that the ferromagnetic behaviour of the end-member phase GaV4S8 is retained at x 0.7. By contrast Ga0.25Ge0.75V4S8 appears to undergo antiferromagnetic ordering at ca. 15 K. All materials with x ¹ 1 are n-type semiconductors whose resistivity falls by almost six orders of magnitude with decreasing gallium content, whilst the end-member phase GeV4S8 is a ptype semiconductor. Powder neutron diffraction studies show that the cubic unit cell is retained for non-stoichiometric materials to the lowest temperatures studied. Single crystals of five erbium-chromium sulphides have been grown by chemical vapour transport using iodine as the transporting agent. Single-crystal X-ray diffraction reveals that in Er3CrS6, octahedral sites are occupied exclusively by Cr3+ cations, leading to onedimensional CrS4 5- chains of edge-sharing octahedra, whilst in Er2CrS4, Er3+ and Cr2+ cations occupy the available octahedral sites in an ordered manner. By contrast, in Er6Cr2S11, Er4CrS7 and Er8Cr3S15, Er3+ and Cr2+ ions are disordered over the octahedral sites. In Er2CrS4, Er6Cr2S11, Er4CrS7 and Er8Cr3S15, the network of octahedra generates an anionic framework constructed from M2S5 slabs of varying thickness, linked by onedimensional octahedral chains. This suggests that these four phases belong to a series in which the anionic framework may be described by the general formula [M2n+1S4n+3]x-, with charge balancing provided by Er3+ cations located in sites of high-coordination number within one-dimensional channels defined by the framework. Er4CrS7, Er6Cr2S11, Er8Cr3S15 ii and Er2CrS4 may thus be considered as the n = 1, 2, 3 and members of this series. Whilst Er4CrS7 is paramagnetic, successive magnetic transitions associated with ordering of the chromium and erbium sub-lattices are observed on cooling Er3CrS6 (TC(Cr) = 30 K; TC(Er) = 11 K) and Er2CrS4 (TN(Cr) = 42 K, TN(Er) = 10 K) whereas Er6Cr2S11 exhibits ordering of the chromium sub-lattice only (TN = 11.4 K). These four materials have been studied using neutron diffraction which allowed magnetic ordering to be examined.

The main objective of this work was to develop predictive models for nanofiltration (NF) membrane processes. A one-parameter model (pore radius) for uncharged solute rejection has been developed. The good agreement between the proposed model and experimental data confirmed that uncharged solute rejection is well described by continuum models. A two-parameter model (pore radius and membrane charge) for electrolyte rejection has also been developed. Dielectric exclusion was included as an energy barrier to ion partitioning into the pores, the reassessment of which using NaCl rejection at the membrane isoelectric point introduced a third model parameter, the average pore solvent dielectric constant. The predicted membrane charge densities with the three-parameter model were more realistic in magnitude than those from previous models and their variation with concentration for divalent salts was in better agreement with physical models of ion adsorption. Analysis of experimental rejection data with truncated pore size distributions and a variation of viscosity with pore radius resulted in model parameters that represented the average value over all pore sizes. Further, analysis of salt mixtures showed that large experimentally observed negative rejections were very well described with fitted charge densities of similar magnitude to those from single salts. Finite Difference linearisation of pore concentration gradient greatly simplified the numerical solution of the three-parameter model. The validity of the linearised model was tested both experimentally and theoretically, showing the model to be a powerful tool for characterisation of NF membranes and subsequent prediction of separation performance. Overall, the work presented in this thesis has improved the understanding of the separation mechanisms of NF membranes, especially dielectric exclusion. The developed models are more rigorous than those proposed previously and represent a significant contribution to the field of predictive NF modelling.

The work presented in this thesis deals with the liquid chromatographic (CLC) measurement of the liquid/gas partition coefficients (KKR) and specific retention volumes (V°) of a number of solutes, of varying chemical types, with each of three binary solvent mixtures. The objective of this study was to attempt to establish further evidence in favour of the Microscopic Partition (MP) model of solution behaviour, proposed by Purnell and Laub. This model is based on the observation, of Purnell and Vargas de Andrade, that the relationship between KR and volume fraction (b), for a mixture of two solvents is strictly linear. The solvent systems studied, together with the solutes used, were as follows: (1) tri-n-butyl phosphate/ethylene glycol (at 21°C) (2) ethyl benzoate/propyleno glycol (at 30°C). For both these systems, Kp~ values were calculated for each of the following solutes: Furan, diethyl ether snd methyl formate. (3) octadecanol/octadecylamine (at 60°C, 70°C and 80°C) Vo values were calculated for the following solutes: n-pentane, n-hexane, n-heptane, furan, gthiopbene, chloroform, di-chloromethane, ethyl acetate, diisopropyl ether and propanol. Solvent systems (1) and (2) were studied, in particular, in order to provide a test for the proposed MP model of solution behaviour. As there remained a remote possibility that all the binary systems dealt with previously were ideal, the present work was also aimed at the elimination of the above objection, as well as testing the overall generality of the basic equation. The two systems presented in this section of the work involved partially miscible binary solvent mixtures, since, not only would such a liquid pair be highly non-ideal but, in addition, would fit closely to the proposed model of solutions. This is because, while over some composition range the system will be single phased, over some other range it will definitely be two phased and highly aggregated. In both oases, columns were studied spanning the whole composition range i.e. b = 0-i 1. For each of the partially miscible pairs, it was found that, within the limit of reasonable experimental error, the data obtained obeyed the basic equation of Purnell et al, and hence must be taken as strong evidence in support of the proposed MP model of solution behaviour. (2)system (3) was studied in order to compare the results obtained for a solvent pair in which a specific interaction might be expected to occur with those of the two previously mentioned solvent pairs. For this supposed interacting solvent system there was found to be some curvature, at the pure ootadeoanol end of the composition range.

No description available.

At the present, numerous kinetic theories are available to electrochemists in describing chemical reactions at the electrode. These exist in varying degree of complexity, ranging from simplistic empirical formulae to more rigorous models that account for microscopic physical phenomena pertiaining to the reactive species and their environment. However, experimental work documented in support of the validity and comparison between these theories is scarce. This is largely due to difficulty in attaining and controlling the experimental conditions where applicability of the theories break down. As such, the current work utilizes state-of-the-art · electrochemical experimental techniques in order to test some of the most prominent electrode kinetics theories via comparison to simulations. This is done with the aim of identifying their limitations and providing new insight into fundamental mechanistic processes that occur during an electrochemical reaction.

Mesoporous, nanocrystalline, metal oxide films exhibit a broad range of attributes attractive for technological applications, including high surface area, semiconducting behaviour, optical transparency in the visible region of the electromagnetic spectrum and excellent mechanical properties. They can be functionalised by the attachment of metal complexes and organic molecules to the metal oxide surface through ligating groups such as carboxylic acids. This thesis addresses the interaction of such functionalised metal oxide films with redox species and ions in solution for applications including dye-sensitised solar cells (DSSCs) and heterogeneous sensing and scavenging of pollutants. The first study reported in this thesis employs a thiourea based organic molecule to functionalise a mesoporous Ah03 film, and demonstrates that this functionalised film can be used as a heterogeneous colorimetric cyanide sensor in aqueous solution. This strategy is extended to a series of ruthenium based metal complexes which are employed to functionalise mesoporous Ti02 films. These functionalised films are shown to bind mercury ions, enabling them to function as selective mercury scavengers. This mercury binding is also shown to disrupt lateral cation percolation between adjacent dye molecules. Electrochemical studies are employed to analyse this cation percolation in detail for two different transition metal complexes, with the introduction of a secondary acceptor group shown to result in an order of magnitude increase in the kinetics of cation percolation. The cation percolation results are discussed in relation to their importance in dye-sensitized solar cells. The last two results' chapters of this thesis address the interaction of functionalised mesoporous metal oxide films and iodine in solution, and the importance of this interaction for the function of dye-sensitised solar cells. Based upon these studies, an enhancement of cell performance is expected through modification of dye structure and the electrolyte composition.