In the growing field of polycyclic aromatic hydrocarbons (PAHs), the replacement of carbon with isostructural atoms is becoming a versatile functionalisation strategy to tailor the optoelectronic properties of the materials. Among the different dopants, the substitution of C-C pairs by isoelectronic B-N covalent couples leads to isostructural molecular material bearing strong local dipole moments. This imparts a series of physical-chemical properties to the molecule, such as wider HOMO-LUMO gap, the introduction of anchoring points for gas storage and peculiar self-assembly behaviour on metal surfaces. The BN/CC isosterism concept goes back to the seminal discovery of the borazine (H3B3N3H3) by Stock and Pohland in 1926. Thus, in reference to its isoelectronic and isostructural relationship withbenzene, borazine ring is commonly known as “inorganic benzene”. Hence, borazine and its derivatives are valuable molecular modules to be inserted as doping units in graphiticbased carbon materials to tailor their physical-chemical properties. This dissertation focuses on the design, synthesis and characterisation of novel organic materials doped with borazine modules, with the aim of exploring the photophysics, electronics and self-assembly properties of hybrid boron-nitrogen-carbon (BNC)frameworks. Before addressing the detailed investigations of this thesis work, in Chapter I, a brief introduction on the past and recent achievements in the organic synthesis of borazine and its derivatives are given to the reader. This chapter also includes the main synthetic methods used for their functionalisations, as well as their chemical properties and materials applications. Chapter II addresses the design and synthesis of three-branched borazine doped polyphenylenes, in which one or more aryl units are replaced by borazine rings. Owing the possibility of functionalising the borazine ring with different groups on the aryl substituents at the N and B atoms, BNC polyphenylenes were prepared through the decarbonylative [4 + 2] Diels-Alder cycloaddition reaction. To achieve this, two types of molecular modules were synthesised: core and branching units. Therefore, having the possibility of introducing the borazine in different ratios, orientations and positions, three-branched hybrid polyphenylenes featuring controlled orientation and dosages of the doping B3N3-rings were prepared (Figure A.1). At last, the photophysical properties of borazine-doped polyphenylenes have been investigated, describing the relation between the light emission properties and the orientation / dosage doping of these hybrid materials. The second project tackled in this doctoral work is described in Chapter III. Inspiring by the local polar character of the borazine ring, B3N3 scaffold can theoretically interact with polar or polarisable gas molecules, thus making BN-materials promising candidates for tailoring the gas absorptions. In this chapter, the preparation of 3D BN metal organic framework (BN-MOF), composed by three-carboxyl borazine 3-1 as organic linker and [Zn4O(CO)6] as metal cluster is described (Figure A.2). Additionally, to evaluate the effect of the BN doping units in gas storage, the isostructural 3D C-MOF reference, in which the borazine core is replaced by the benzene unit, has been prepared (Figure A.2). The last section of the chapter is dedicated to the description of the X-ray crystal structures of the MOFs as well as their morphology, surface area and thermal stability. Finally, Chapter IV is dedicated to the investigation of three-pyridyl borazine derivatives, amenable to self-assemble and form 2D metal-organic porous network upon deposition on metal surfaces. The first part of the chapter deals with the synthesis of borazine 4-6 through a Suzuki cross-coupling reaction between borazine bearing three-OTf groups and an organoboron pyridyl moiety. The second part describes, by scanning tunnelling microscopy (STM), the tailoring of the 2D self-assembly of borazine 4-6 on Ag(100) and Cu(111) via coordination and thermal treatments. Specifically, densely packed honeycomb network on Ag(100) was observed, whereas interconnected chains were found on Cu(111). Upon deposition of additional Cu atoms at 420 K, a structural transformation can be induced on Cu(111), which leads to a fully three-fold coordinated triangular network (Figure A.3).

One of the main challenges for the creation of artificial light harvesting systems is to develop high-yielding and easy-to-implement protocols for the assembly of chromophores into spatially organized architectures. The use of a template bearing pre-programmed receptor sites accommodating selectively specific chromophores appears to be a very attractive synthetic approach. In this manuscript, pre-programmed peptides will guide the spatial arrangement of different dyes, acting as energy donors and acceptors and absorbing over the whole visible spectrum. The self-assembly of the chromophores into the scaffold can be achieved through the engineering of orthogonal recognition motifs. The employed method, described in Chapter 2, relies on the development of simultaneous multireaction systems. A triorthogonal system involving three reactions of dynamic covalent chemistry, namely disulfide exchange, boronate and acyl hydrazine formations, is first optimized for the design of triorthogonal recognition motifs. The complexity of the system is then increased by incrementally adding reactions: the strain promoted azide-alkyne cycloaddition and the inverse electron demand Diels-Alder cycloaddition between s-tetrazine and trans-cyclooctene leading to tetra- and pentaorthogonal recognition motifs. Chapters 3 and 4 address the creation of a library of multichromophoric architectures with tailored yellow, red and blue chromophores through the three simultaneous reactions of dynamic covalent chemistry. In this respect, the design and synthesis of various α-helix peptides bearing disulfide, diol and hydrazide acting as receptor sites at given positions and chromophoric units with complementary sticky sides are detailed, as well as the dyes assembly leading to excitation energy transfer within the colored structure. Finally, Chapter 5 focuses on the extension of the absorption range of the colored architectures by selectively incorporating additional dyes following their energy gradient to favor the unidirectionality of the energy transfer. This will be achieved through the introduction of the tetra- and pentaorthogonal recognition motifs within the peptide and the dyes (Figure 1).

There is a major limitation preventing the use of bio-fuels as they are currently not economically viable when compared to fossil fuels. To make bio-fuels more economically attractive, new chemical processes for converting waste by-products into a valuable commodity are necessary. One of the main by-products from the production of bio-fuels is glycerol. This thesis investigates the oxidation of glycerol with the aim of selectively producing lactic acid. Glycerol oxidation is a relatively complex reaction with two potential pathways leading to a variety of products. The oxidation pathway leads to the C3 products glyceric acid and tartronic acid, with further oxidation leading to C2 and C1 products. The dehydration pathway leads to lactic acid, through a currently unknown mechanism. The reaction scheme sets out two challenges to solve; what conditions are optimal for a high yield of lactic acid and what is the mechanism. When observing the two challenges, one begets the other. By characterising what conditions are optimal for lactic acid production, it would then be plausible that an experiment could be designed to confirm the mechanism of lactic acid formation. Using a standard 1 wt% AuPt/TiO2 catalyst, an investigation into the reaction conditions was conducted and it was found that the conditions had a significant effect on the product distribution. A progressive elimination was designed so as to progressively find the optimal conditions for the formation of lactic acid. The conditions mapped were; temperature, O2 pressure, base substrate ratio, metal substrate ratio and stabilising agent used to produce the catalyst. Temperature was found to increase selectivity to lactic acid as it was increased. Increasing the O2 pressure showed an increase in lactic acid selectivity up to 3 bar, at which point there was an increase in C-C scission products. By increasing the base ratio, lactic acid selectivity increased dramatically, providing an insight that would later be used to help confirm the mechanism. Higher metal substrate ratio was found to increase the C-C scission products formed. Four types of stabilising agent were used to observe the effect of stability and activity, with PVA providing a balance between stability and selectivity. The parameter map led to a series of conditions that produced a yield of 80 % lactic acid. Using the conditions found from the parameter mapping study, an experiment was designed to attempt to confirm the mechanism of formation for lactic acid. Two current theories that lactic acid formation proceeds either via a benzylic rearrangement or a Cannizzaro reaction, provided an insight as to how this would be achieved, as the position of the carbon environments in lactic acid would change dependent on the mechanism followed. Through a 13C labelling study, NMR spectroscopy was used to show that there was no net movement of the carbon environments during the mechanism, discounting the benzylic rearrangement. Through a logical discussion, the Cannizzaro reaction was also discounted as technically this is an intermolecular hydride shift, with the mechanism being confirmed to be an intramolecular hydride shift. Supercritically prepared perovskite supports were used to see if the lactic acid yield could be increased further through the change of the B site cation. Contrary to initial belief, LaMnO3 heavily favoured the oxidation pathway at the same conditions the standard AuPt/TiO2 produced a high yield to lactic acid. This was found to correlate with the oxygen adsorption to a clean lattice structure, as perovskites with high oxygen adsorption favoured the oxidation pathway whilst low oxygen adsorption favoured the dehydration pathway. LaCrO3 was found to produce a yield of up to 86 % lactic acid under the optimal conditions outlined in the parameter mapping study. The selective control of reaction products could ultimately lead to more economically viable bio-fuel production.

Peptides derived from DNA-binding zinc finger proteins were synthesised with pairs of cysteine residues with i,i+7 and i,i+11 relative spacings introduced into their sequence. The sidechains of these cysteine residues were then alkylated with the well-known water soluble photochrome 3,3’-bis(sulfo)-4,4’-bis(chloroacetamino) azobenzene (BSBCA). The change of shape of the azobenzene dye in these peptide-dye conjugates allowed photocontrol of peptide structure and thus peptide-DNA interactions. For a single zinc finger helix, UV irradiation yielded a peptide conjugate with a dissociation constant with respect to its cognate DNA sequence of 100 nM with no binding apparent prior to irradiation. However, the relatively short half-life of BSBCA proved a stumbling block, particularly in the control of larger peptides using multiple azobenzenes to control several -helical structural elements within large peptides. In addition to the short half-life of cis-BSBCA under physiological conditions, multiple BSBCA switches attached to the same peptide were shown not to relax independently of each other. These results led to the design, synthesis and examination of novel photo switches sensitive to visible, rather than UV light, with improved light state half-lives and bidirectional optical switching. Initial studies on thioindigo-based switches proved that molecules sufficiently polar to be water soluble were inaccessible by concise synthetic routes. Attention was then turned to the synthesis of ortho-halogen substituted azobenzenes and investigation of several new conjugation strategies for linking these photosensitive molecules to peptides. Subsequent refinements to the design of the tetra-ortho-halogen substituted azobenzenes altered the position of UV/visible absorbance bands of the cis and trans isomers to create a 47 nm separation in the wavelengths of the n-π* absorbances of the isomers to allow effective bidirectional switching. These changes also improved the half-life of the cis state from 24 minutes at 20 0C to 3,256 minutes at 60 0C. One of these new azobenzenes was reacted with apoptosis-inducing Bak peptides with different cysteine spacings (i,i+7 and i,i+11). Less stringent control over the binding of these peptides to Bcl-xL was observed than with BSBCA, perhaps due to the more flexible nature of the new crosslinker, but the optical properties of this class of molecules suggest a little further development will yield much improved photoswitches.

Terpenes are one of the most structurally varied families of natural products with extraordinary chemical properties that have been exploited for numerous applications. Sesquiterpene synthases are a family of metal-dependent enzymes that catalyse the cyclisation of farnesyl diphosphate (FDP) into a myriad of complex C15-isoprenoid hydrocarbons, the sesquiterpenes. δ-Cadinene synthase (DCS) from Gossypium arboreum (cotton tree) catalyses the formation of δ-cadinene (DCN), a bicyclic intermediate in the biosynthesis of important phytoalexins such us gossypol. Two mechanistic proposals have been made for the formation of δ-cadinene: a 1,10-ring closure mechanism leading to the key intermediate germacradienyl cation, or a 1,6-ring closure leading to theaalpha-bisabolyl carbocation. Previous investigation with fluorinated FDP analogues were in partial agreement with both scenarios and hence it was not possible to distinguish unambiguously between the two possible cyclisation reactions. To investigate the catalytic mechanism of DCS, enantiopure samples of the azaanalogues of alpha-bisabolyl cation and germacradienyl cation were needed. These compounds are designed as stable structural and electrostatic mimics of the putative short-lived carbocationic intermediates generated by terpene synthases, and hence often act as potent reversible competitive inhibitors (low Ki) of these enzymes. Here, the enantioselective total synthesis of R- and S- aza-analogues of the alpha-bisabolyl cation are described as well as the partial racemic synthesis of azagermacradienyl cation. Both enantiomers of aza-bisabolyl cation were goodmimics of α-bisabolene. They were competitive inhibitors of DCS, providing evidence for a 1,6-cyclisation closure. The second part of the project involved the investigation of the role of tryptophan 279 for the desolvation of the active site of DCS and therefore for the formation of DCN. Seven mutants of W279 were created. The data obtained showed that W279 is essential to prevent water from entering the active site and form the hydroxylate terpenoid germacradien-4-ol (GD4ol). Mutagenesis studies yielded a mutant, W279A, capable of making GD4ol as the sole product.

Gunshot residue (GSR) is a complex chemical mixture that is created during the discharge of a firearm. Its detection and interpretation play a crucial role in the investigation of firearm incidents. Current GSR analysis is limited to inorganic GSR (IGSR), however, the evidential value could be strengthened by inclusion of organic GSR (OGSR). The present study aims to address this potential by proposing a categorisation system for relevant OGSR compounds and developing a methodology for the collection, extraction and analysis of both organic and inorganic GSR from a single sample. The organic composition of more than 50 propellant powders has been determined and compared against more than 200 propellant compositions reported in the literature. This work has resulted in a three-tier categorisation system for OGSR compounds, which together with the current IGSR classification will provide unequivocal identification of GSR materials with the possibility of discriminating between GSR from different ammunition types. Evaluation of MonoTrap extraction showed that this is an effective pre-concentration technique for the characterisation of propellants. Solid-phase microextraction (SPME), however, was the superior method for the extraction of OGSR compounds from various sampling media, including swabs and stubs. The optimised methodology involves GSR collection using carbon adhesive stubs followed by SPME gas chromatography – mass spectrometry (GC-MS) analysis of OGSR and subsequent scanning electron microscopy – energy-dispersive X-ray spectrometry (SEM-EDX) analysis for IGSR. This protocol has resulted in the detection of both characteristic IGSR and categorised organic compounds, demonstrating the ability to obtain a full chemical profile from a single sample. Detection of both first and second tier organic compounds provides complementary compositional information that could be used to discriminate between samples. Furthermore, this methodology requires no changes to the current sampling and IGSR analysis protocols and addresses the limited storage time of OGSR. Since GC-MS instruments are readily available in most analytical laboratories, implementation of the proposed protocol is feasible.

No description available.

Organic materials offer key advantages over their inorganic counterparts for photovoltaics due to the ability to easily tune the physical properties and develop cheaper, more flexible, photovoltaic devices. This thesis describes the synthesis and characterisation of a variety of compounds from small-molecule to supramolecular and polymeric systems with the potential to be used in organic electronics. Herein is described an optimised synthetic route for the synthesis of two flavins and the synthesis and characterisation of a novel flavin and fluorene polymer. Also described is the synthesis of two novel rotaxane structures with the potential for use in organic field effect transistors. The synthesis of a novel polymer incorporating the naphthalene diimide moiety and a P3HT functionality utilising click methodology is also described. Finally the synthesis of a thiophene based star shaped molecule as electron transporting material is also described along with a flavin based organic dye for use in dye-sensitised solar cells.

Grain orientated magnetic steels have applications in the electrical industry as components of power transformers. Power losses are observed in these devices due to the magnetostrictive effect. Aluminium phosphate coatings are applied to the steel to impart a tensile strength to the steel inhibiting the effects of magnetostriction, reducing losses. This thesis examines the development and application of aluminium metaphosphate coatings with the aim of improving the currently used aluminium orthophosphate coatings. The experiments described here show that aluminium metaphosphate can be formed using a variety of readily available aluminium precursors and that the products are stable to the effects of thermal hydration. A combination of bulk and surface analysis techniques suggest that there is need to re-examine the accepted assignments of the O(1s) region of the XPS for aluminium metaphosphates. The testing of the applications of the metaphosphates as stress coatings has yielded results indicating improved performances over the orthophosphate coatings. SEM analysis has shown that this is due to the formation of a phosphate film across the surface of the substrate imparting a greater degree of tension than orthophosphate coatings. Investigations examined the proposal that the low temperature synthesis of mullite (Al6Si2O13) is facilitated through the addition of Jahn-Teller active complexes. The findings showed that the addition of stable low-spin complexes resulted in the formation of mullite by 800 oC. Also, tested was the hypothesis that this synthesis route resulted in the formation of nano-scale mullite, but SEM image data has discounted this.

A series of new aluminium(III) and titanium(IV) complexes bearing a series of salen ligands have been prepared; the ligands have not been previously used to support Al or Ti. The complexes have been tested as initiators for polymerization reactions, including both ring-opening polymerization of cyclic esters, and the ring-opening copolymerization of cyclic anhydrides and epoxides. This thesis has been divided into six chapters: Chapter 1 provides an overview of the use of Al and Ti complexes in the ringopening polymerization of cyclic esters, and the use of Al complexes in the ringopening copolymerization of cyclic anhydrides and epoxides. An introduction to these catalytic reactions is discussed, along with some background relating to polymer characterization. Chapter 2 provides details of the ligand synthesis, and the preparation of the monometallic metal complexes used in the rest of the thesis. A relatively new class of salen-type ligands bearing a hemi-labile pyridyl donor have been prepared and fully characterized. The challenges that accompanied the preparation of some derivatives of the ligand have been discussed, and the identity of the ligands has been supplemented by solid state analysis. Complexes based upon Al and Ti, derived from these ligands, have been reported in this thesis. Their synthesis and characterization in both solution and solid state are reported. Three types of Al complex have been synthesized: alkyl, alkoxide/aryloxide, and chloride. These complexes have been characterized using NMR spectroscopy, which includes a discussion of the hemi-labile nature of the pyridyl; this was confirmed using variable temperature NMR spectroscopy and equilibrium analysis. The synthesis and characterization of Ti(IV) isopropoxide complexes is described. NMR spectroscopy, including two dimensional experiments such as COSY, HSQC and HMBC, were instrumental in determining the stuructures of these complexes. Chapter 3 describes how to exploit the complexes described in Chapter 2 as catalysts for the ring-opening polymerization of cyclic esters such as rac-lactide and ε-caprolactone. Both aluminium and titanium showed good to moderate activity in this type of polymerization. Various conditions were investigated in order to obtain the optimum conditions to afford polyester with acceptable molecular weights and polydispersity indices. Chapter 4 describes how to exploit the aluminium chloride complexes described in Chapter 2 in the ring-opening copolymerization of cyclic anhydrides and epoxides, thereby diversifying the range of available polymers (and associated properties) by incorporating various monomers. The copolymerization reaction was investigated under various conditions, including with and without cocatalyst, and the polymers were evaluated using 1H NMR spectroscopy and gel permeation chromatography. Chapter 5 describes the synthesis and characterization of bimetallic aluminium complexes using the Salpy ligand framework. Three bimetallic aluminium complexes were obtained and were characterized in both solution and in the solid state. The complexes were used as initiators in the ring-opening polymerization of ε-caprolactone. The polymerization performance was evaluated and the polymers characterised using gel permeation chromatography. Chapter 6 contains full experimental details and characterizing data for all ligands and complexes described within the thesis.