The aim of this project was to synthesise via low temperature routes novel mixed metal oxide materials which are stable at high temperatures and chemically resistant. Low temperature routes include synthesis techniques such as sol-gel and coprecipitation. Zircon is used extensively as a crystal host system for chromophores in the pigment industry. Sol-gel and co-precipitation techniques for the production of zircon were investigated with a view to optimising the process to achive shorter firing times and lower firing temperatures (Chapter 4). Zircon was made by several gel methods and the structure of the gels investigated using a small angle x-ray scattering technique (Chapter 3), this method highlights the internal properties of the gel. The sol-gel and co-precipitation products were fired with, and without a mineraliser and analysed using x-ray diffraction. It was found that co-precipitation techniques proved more successful and this approach was transferred to other crystal systems related to zircon. A scheelite phase is formed when zircon is under high pressure and temperature with the silicon in a tetrahedral site and the zirconium in a dodecahedral site as in zircon. GeZrO4 and CaWO4 (Chapter 5 and Chapter 6) both minerals have a scheelite crystal structure at room temperature and pressure. Germanium and silica have the same oxidation state and are both in the tetrahedral site, but CaWO4 has Ca 2* and a We" in the dodecahedral and the tetrahedral site respectively. Both scheelite synthesis routes were optimised using a factorial experimental design experiment. Pr-GeZrO4 and Cr-CaWO4 were optimised and the resulting methodology transferred

Phthalocyanines and other closely related compounds are an important class of macrocycles with many commercial applications. They display interesting optoelectronic and coordination properties, which has resulted in their utilisation in a wide range of fields including optical data storage, electrochromic and optical limiting devices, photosensitizers and medicinal therapeutic agents, and multistage-redox-dependent fluorophores. The synthesis, optoelectronic and surface-assembly properties of several new axially disubstituted silicon phthalocyanines are detailed in this work. Axial ligands include phenyl, terphenyl, thienyl and pyrenyl derivatives. Their absorption and emission spectra are reported and fluorescence lifetimes and quantum yields are correlated with the ligand structures. The optoelectronic properties of a novel free-base phthalocyanine bearing peripherally attached fluorene substituents are also described. Several of these silicon-phthalocyanines were used to assemble thin films on electrode surfaces, and techniques such as scanning Kelvin nanoprobe microscopy and atomic force microscopy, as well as chronoamperometric measurements were used to probe these surfaces. A number of free-base porphyrins bearing a variety of aryl substituents at the meso-positions are also described. The conversion of some of these free-base porphyrins to metalloporphynns is detailed, and a thorough examination of the fluorescence properties of all synthesised porphyrins is also presented. Pyrazinoporphyrazines are a closely-related analogue of phthalocyanines, and several new examples of these systems have been synthesised. As with both the phthalocyanines and porphyrins, their fluorescence properties have been investigated in detail.

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No description available.

The preparation of new functionalised phthalocyanine compounds has been the subject of intense research over the last three decades in order to develop new commercial applications. Interestingly, their electrical and physical properties can be tuned by suitable derivatization of their rigid inner core. A brief summary of the syntheses, properties and applications of these compounds is described in Chapter 1. The aim of this project was to synthesise new phthalocyanines for use in field effect transistors (FETs). Chapter 2 describes the investigation of the preparation of novel polysiloxane phthalocyanine polymers having hexyl substituents in non-peripheral positions. It has been shown that polysiloxanes comprising non-peripherally substituted phthalocyanines of this type cannot be isolated. Further investigation indicates that this is likely to be due to steric hindrance. A series of mixed oligomeric compounds were successfully synthesised by condensation of the corresponding substituted and unsubstituted silicon phthalocyanine monomers. These co-oligomeric materials were functionalised, isolated and characterised and found to exhibit interesting optical properties. Moreover, the solid-state structure of a mixed phthalocyanine dimer was determined by X-ray diffraction analysis. Interestingly, red fluorescence emission was also exhibited by derivatives of these compounds. During the preparation of a phthalocyanine intermediate, an unexpected coloured sideproduct was also observed. The structure of this product proved to be closely related to the phthalocyanine and was characterised as a tetrabenzotriazaporphyrin. The origin of this by-product was explored. A series of metal-free and metallated derivatives of this compound was subsequently prepared and their optical and physical properties compared to their corresponding phthalocyanines. The results of these investigations are reported in Chapter 3.

The phthalocyanines are a family of intensely coloured compounds (usually blue or green) which are structurally similar to the porphyrins. A brief summary of different phthalocyanines reported in the literature so far, their preparations and applications are detailed in the introductory chapter. A number of substituted phthalocyanines are already known as effective photosensitisers for photodynamic therapy (PDT). Therefore the design and synthesis of a series of new unsymmetrically substituted phthalocyanine derivatives has been described. Also the preparation of a series of phthalocyanines bearing one or more 4- tert-butylphenyl substituents was investigated. Reports in the literature suggested such derivatives should be able to bind to cyclodextrins to afford water soluble formulations. The synthesis of highly soluble axially substituted phthalocyanine derivatives containing indium within the macrocycle cavity is described. These materials have been found to have useful optical and electrical properties. One compound of this series is chiral and its solid state structure has been determined by X-ray diffraction analysis. The synthesis of metallated and non-metallated porphyrazines has been explored. The metal-free derivative generates conventional "face-to-face" assemblies in solution, whereas the zinc analogue forms alternative "edge-to-face" complexes via axial ligation. Finally, the research described in the fourth chapter involves the synthesis of new alkylsulfanyl and arylsulfanyl phthalocyanine derivatives. The complexation of such materials with silver(I) ion has been investigated and monitored by UV/vis spectroscopy.

Materials with potential for high temperature inorganic pigment applications (e.g. ceramics) have been synthesised using solid state methods and characterised using powder X-ray and neutron diffraction, magic angle spinning NMR, Mossbauer spectroscopy, UVNis spectroscopy and colour measurement techniques. A number of compounds containing tin (H) and niobium (V) have been modified and doped with various constituents to tailor and widen the colour properties of the bright yellow parent phases. The dark yellow (L*(91.28), a*(13.74), b*(54.76)) tin niobium oxide pyrochlores have been re-characterised using neutron diffraction techniques. These materials exhibit both cation and anion disorder caused by a stereoactive lone pair on the tin (H) metal centres. Solid state NMR and Mossbauer studies have shown the presence of tin (IV) on a symmetric site within the primary phase of the pure oxide pyrochlore and methods have been investigated to minimise the tin (H) disproportion method from where the tin (IV) is derived.

Department of Chemistry / MSc (Chemistry) / See the attached abstract below