This theoretical work looks at excited state photochemistry - the study of the molecular processes triggered by the absorption/e mission of light to/from electronically excited states. The approach taken here is that of using approximate vibronic coupling models, as well as extending the methods and algorithms to construct them. These are then used in quantum dynamic calculations to obtain time-dependent properties, compute spectra and calculate dissociation cross-sections. A genetic algorithm which aids to the fitting of diabatic model parameters is described in detail and tested in two systems. The neutral and cationic surfaces of cyclo-butadiene is one of the systems for which this fitting algorithm was used and the photo-electron spectrum was then calculated to compare with the experimental one. We show how one can generate polynomial functions which are invariant with respect to the non-Abelian point groups. These invariant polynomials are then used for the construction of an acetylene model, where photo-dissociation cross sections are calculated for all possible angles. A bigger system Tolan, the monomial of a family of a photo-active dendritic antenna, was modelled. Comparison between the experimental and calculated absorption spectra validates the model and is subsequently used to model the first few picoseconds of population transfer.

The work presented in this thesis focuses on two different structures, the Ruddlesden Popper and perovskite, which have shown promise as catalysts in fuel cell devices. The Ruddlesden Popper materials have interesting structural properties allowing the possible incorporation of anions within the interstitial sites. The possible incorporation of water and fluorine into these interstitial sites was investigated for the systems La\(_2\)N\(_i\)\(_O\)\(_4\)\(_+\)\(_δ\), Nd\(_2\)NiO\(_4\)\(+\)\(_δ\), La\(_2\)CuO\(_4\)\(_+\)\(_δ\) and Sr\(_3\)Fe\(_2\)O\(_7\)\(_-\)\(_y\). In the case of water incorporation, the most interesting results were observed in La\(_2\)NiO\(_4\)\(_+\)\(_δ\). For this system, large amounts of water were shown to be incorporated using an indirect method which involved fluorination of the materials followed by ion exchange. This is the first time such a method has been demonstrated. The work on the perovskite materials (SrCoO\(_3\), SrMnO\(_3\), SrFeO\(_3\) and CaMnO\(_3\)) focused on doping with various oxyanions (phosphate, silicate and sulphate). It was discovered that small amounts of oxyanion doping could be achieved, which caused a large increase in the conductivity. This increase was correlated either to a phase change on doping or in the case of the CaMnO\(_3\) material due to the resultant electron doping. Electrochemical tests were performed to determine if the materials would be of use as cathode materials in fuel cells.

Transhydrogenase couples hydride transfer between NADH and NADP+ to proton translocation across a membrane in animal mitochondria and bacteria. The product/reactant ratio can be driven to values greater than 400 by the energy of the proton gradient, demonstrating the importance of this gradient, and hence why transhydrogenase can be considered a molecular machine. We isolated a number of possible transition states for the hydride transfer reaction in R. rubrum transhydrogenase, the lowest energy of which is symmetrical. The nicotinamide ring orientation observed in the enzyme crystal structure most closely resembles an isolated asymmetrical transition state, not a symmetrical one. This observation is the basis for the asymmetric hypothesis. The asymmetric transition state hypothesis postulates that the asymmetry of the hydride transfer transition state for the reaction is responsible for the raised equilibrium constant. We set out to probe the thermodynamics of the hydride transfer reaction using hybrid QM/MM (ONIOM) calculations on simple dIdIII model systems of R. rubrum transhydrogenase. Our results with these simple model systems allow us to infer that the whilst the asymmetry of the transition state is influential in altering the equilibrium constant of the hydride transfer reaction, the binding interactions of the surrounding protein environment also play a significant role.

X- and Q-band EPR/ENDOR spectroscopy was used to study the structure of a series of heteroleptic and homoleptic copper(II)-bis(oxazoline) complexes, based on the (−)-2,2′-isopropylidenebis[(4S)-4-phenyl-2-oxazoline] (1) ligand and bearing different counterions (chloride versus triflate); labelled [Cu(II)(1a-c)]. The geometry of the two heteroleptic complexes, [Cu(II)(1a)] and [Cu(II)(1c)], was found to depend on the choice of counterion. Formation of the homoleptic complex was only evident when the Cu(II)(OTf)2 salt was used whereas Cu(II)Cl2 inhibited the transformation from heteroleptic to homoleptic complex. The hyperfine and quadrupole parameters for the surrounding ligand nuclei were determined by ENDOR. Well resolved 19F and 1H couplings confirmed the presence of both coordinated water and TfO- counterions in the [Cu(II)(1a)] complex. The structure of other copper(II)-bis(oxazoline) derivatives, based on 2,2’- methylenebis[(4S)-4-phenyl-2-oxazoline] (2), and 2,2’-isopropylidenebis[(4S)-4-tertbutyl- 2-oxazoline (3) were then investigated using X- and Q-band EPR/ENDOR spectroscopy. Variations in the structures of the complexes as a function of different counterions were also investigated; for ligand 2, X = TfO-, Cl- and for ligand 3, X = TfO-, Cl-, SbF6 - (where X = counterion). Formation of the homoleptic complex was evident when the Cu(II)(OTf)2 and Cu(II)Cl2 salts were used with ligand 2, but only when using the Cu(II)(OTf)2 salt with ligand 3. The substituents on the chiral carbons of the oxazoline rings and on the bridging carbon backbone were found to affect the electron spin density of the structures. An X-band EPR investigation of the interaction of substrates (pyridine, iodobenzene, (diacetoxyiodo)benzene, styrene and PhI=NTs) with [Cu(II)(1a)] was also performed, before probing the [Cu(II)(1a)] catalysed asymmetric aziridination of styrene, with PhI=NTs as the nitrene source. Using EPR to monitor the course of the reaction after the addition of styrene + PhI=NTs revealed the formation of an additional paramagnetic species, for which the g/CuA parameters indicated a change to the equatorial environment of the Cu(II) centre. This was discussed within the context of the proposed reaction mechanism which suggests the involvement of a copper-nitrene intermediate.

Human African Trypanosomiasis (HAT), commonly known as Sleeping Sickness, is endemic in over 36 countries in sub-Saharan Africa. It is caused by the parasitic subspecies Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense, which is transmitted to humans by the tsetse fly. The World Health Organisation estimates that 0.5 million people are currently infected with the disease, with a further 60 million at risk. HAT is lethal if left untreated and there is no vaccine available. There are only four accessible drugs, which are all inadequate and highly toxic. Thus there is a vital need for novel anti-parasitic agents. Compounds interfering with polyamine biosynthesis or function have shown potential use as anti-cancer, anti-HIV, anti-fungal and antiparasitic agents. The overall aim of this work was to synthesise novel macrocyclic polyamines containing different substituents to increase the toxicity against T. brucei. Twenty racemic substituted tetraazamacrocycles B have been synthesised using an iron template method in good yields (54-100%) from triethylenetetraamine and aromatic glyoxal derivatives A. The R-groups were aromatic or heteroaromatic and were selected to give compounds with varying electronic demand and a broad range of log P values. Two derivatives contain parasite-specific recognition motifs were also prepared. The compounds were tested against T. brucei and several of the analogues displayed high activity. Some of these azamacrocycles were also tested for activity against the malarial parasite Plasmodium falciparum, and for oligopeptidase B (OPB) inhibition, with a number of compounds exhibiting promising results.

Polymers composed of alternating p-silphenylene and siloxane units with either dimethyl or methylphenyl substituted silicon atoms have been prepared in a dilute solution condensation of the appropriately substituted phenylenedisilanol, catalysed by tetramethylguanidine di-2-ethylhexoate, TMG. A range of copolymers has been synthesised with extended siloxane segments where the substituents on the silicon atoms are both methyl groups. Two methods of polymerization have been employed with comparable success. These are the condensation between p-phenylenebis(dimethylsilanol) and tetramethyldisiloxanediol catalysed by TMG and the KOH catalysed polymerization of p-phenylenebis(dimethylsilanol) and octamethylcyclotetrasiloxane. Characterisation of the polymers employed the techniques of infrared and n.m.r. spectroscopy and membrane osmometry. Attempts to prepare poly(tetraphenyl-p-silphenylene-siloxane), TPPS, with a high molecular weight have met with little success, only low molecular weight polymer being obtained. The first feature observed in the thermal degradation of poly(tetramethyl-p-silphenylene-siloxane), TMPS, is the development of insolubility in the residue when the polymer is heated isothermally at 350-400°. Weight loss is slight at this stage and is due to the formation of the cyclic dimethylsiloxane trimer and tetramer and a small quantity of "cold ring" fraction. It is suggested that the mechanism at this stage involves structural rearrangements leading either to chain branching or some production of volatile material. Prolonged heating of TMPS at 450-500° results in up to 80% weight~loss, most of which is collected as "cold ring" fraction. Subsequent separation and analysis using GC, GCMS and infrared spectroscopy identified a series of short chain oligomers terminated by either the Si-H or the Si-Ph group. A mechanism involving direct scission of the silphenylene bond has been proposed to account for their formation. The products of degradation of the silphenylene-siloxane polymers with extended siloxane segments are dependent on the copolymer composition. A complex mixture of cyclic oligomers has been separated and identified from the"cold ring" fraction of those polymers with low silphenylene content. The presence of these compounds at the lower temperatures of degradation has led to the assumption that their formation involves a structural rearrangement not unlike that involved in the degradation of poly(dimethylsiloxane), DMS. Results from infrared analysis demonstrates that Si-H groups are formed at higher temperatures, indicating the occurrence of silphenylene bond scission. As the silphenylene content increases, the characteristics of degradation become increasingly more like those observed for TMPS. Thus both the range and the amount of cyclic oligomers, formed in structural rearrangements, decreases in favour of the formation of linear oligomers via rupture of the silphenylene bond. One feature common throughout the copolymer series is the chain branching reaction occurring between 350 and 400·0 A comparison of the rates of branching, calculated from sol-gel analysis, has shown that the rate is directly proportional to the silphenylene content. Thermal analysis demonstrates that poly(metbylphenyl-p-silphenylene-siloxane), MPPS, is thermally more stable to weight loss than !MPS. Benzene and a mixture of linear oligomers, similar in structure to the original polymer but with Si-H and Si-Ph end-groups, have been analysed and identified as the volatile products of degradation with the aid of GC, GeMS and infrared spectroscopy. No evidence of cyclic compounds has been detected. A comparison of results calculated from sol-gel analysis reveals that chain branching occurs more rapidly in MPPS than !MPS. Two distinct stages again appear to be present in the degradation of MPPS. At the lower temperatures of degradation structural rearrangements are responsible for chain branching and the initial production of benzene •. Increasing the temperature causes the mechanism to undergo a change to one involving scission of either the silphenylene or Si-Ph bond as the first stage. Further production of benzene and the formation of the short chain oligomers occur in the higher temperature range. Results from TG demonstrate that the low molecular weight TPPS is thermally less stable to weight loss than DMS. Apart from benzene all the products of degradation are contained in the "cold ring" fraction. Infrared analysis demonstrates that these products are similar in structure to the original polymer. However in view of the inability to obtain higb molecular weight polymer, further investigations of the thermal degradation properties of TPPS have not been pursued. To conclude this work two dimethyl substituted aryloxysilane polymers have been synthesised in a melt polymerization of dimethyldianilinosilane with either hydroquinone or bisphenol A. The thermal stabilities of these polymers have been investigated briefll to gain some indication of the potential value of a more detailed study in this field. Although their thermal stability to weight loss is less than the silphenylene-siloxane polymers, it is comparable with that of DMS. Thus a more thorough investigation of the thermal degradation behaviour of the aryloxysilane polymers has been recommended.

The work presented in this thesis describes routes to the controlled growth of small polyoxometalate clusters achieved by utilising a range of organic counterions in conjunction with electrophilic Ag(I) ions. The subsequent isolation of a new building block; {Ag(β-Mo8O26)Ag} has demonstrated how subtle control can be achieved through the use of bulky and flexible counterions and by solvent. Within most structures the electrophilic ions form {Ag2} dimer groups that link together β-octamolydbdate anions to produce a family of structurally related architectures ranging from isolated units, one- and two-dimensional architectures. Each of the architectures contain {Ag(β-Mo8O26)Ag} based building blocks that can be controlled in their self-assembly by cation and solvent interaction in the solid state. This set of architectures differ in the coordination modes of the linker {Ag2} groups and in the nature of the Ag.Ag interactions that are present in most structures. Furthermore, the isolation of polymeric structures exclusively through solvent ligation has yielded one- and two-dimensional architectures where acetonitrile molecules in particular have formed pseudo cations around the {Ag(β-Mo8O26)Ag} based building blocks. The above synthetic strategy was also extended to other metals to yield some additional structures. Several of the silver polyoxomolybdate compounds have been further investigated on silicon substrates using Scanning Electron Microscope (SEM), and in some instance with Energy Dispersive X-ray (EDX), Transmission Electron Microscopy (TEM) and Selective Area Electron Diffraction (SAED). These techniques have revealed the growth of nanostructure on multiple length scales. Knowledge of the molecular architecture has given a unique understanding of the assembly of these nanostructures including various one-dimensional assemblies (nanorods and nanowires), that have been obtained through different, efficient and inexpensive synthetic methods. The structures have been identified and a hypothetical mechanism for the growth of Ag(0) based nanowires has been correlated to the partial oxidation of methanol and the reduction of Ag(I).

This thesis describes preparative methods for a number of titanium (IV) trischloromonocarboxylates, TiCl3(RC02)(R = C6H5, (C6H5)2(CH3)C, (CH3)2CH, (CH3)3C, C9H6N, o - CH3C6H4, p - CH3C6H4, C6H2(CH3)3, C6H5CH=CH and CH3CH=CH). The reactions of some of these carboxylates with oxygen and nitrogen donor ligands are also described. An X-ray crystallographic study of TiCl3[(CH3)3CO2] showed that the complex exists as trimeric molecules in the solid state. Cryoscopic molecular weight and 1H NMR experiments indicated that the complex dissociates into dimers in solution. The structure of Ti2Cl7(CH3CH=CHC02)(CH3CH=CHC02H) is reported. The complex has a triply bridged structure with two bridging chlorine atoms and a carboxylate bridge linking the titanium centres. Hydrolysis reactions of TiCl3(RC02) species are described and an unusual 170 exchange effect in esters was observed. A mechanism based upon the AAC2 ester hydrolysis mechanism is proposed for this effect. Cyclic Voltarnmetry experiments on [TiCl2(C6H5CO2)EtOAc]20 indicate that both Ti (IV) centres are reduced to Ti(III) and that the reduction product reacts with a component of the solution to regenerate the starting material. Some titanium-magnesium bimetallic complexes were prepared and characterised.

The work presented in this thesis involves the application of mass spectrometry to the analysis of a number of both commercial products and model organic compounds. Use of soft ionisation techniques for thermally labile and ionic compounds (mainly fast atom bombardment, field desorption and thermospray) has been extensively explored for the provision of both qualitative and quantitative information. More established ionisation techniques (electron impact and chemical ionisation) have also been utilized in order to obtain qualitative data. In many cases comparisons have been made between different ionisation modes, and some discussion of the processes occuring is given. Ion structures and decomposition pathways have been elucidated by both tandem mass spectrometry and high mass resolution measurements. Analysis of both complex mixtures and pure compounds has been performed. The systems studied were: surfactants (anionic - sodium alcohol ether sulphates, nonionic - alcohol ethoxylates, cationics - mainly quaternary ammonium salts), organotin PVC heat stabilisers and organic heterocyclic compounds (some chromans, chromenes and corresponding oximes).

The work contained in this thesis describes the crystal structures of a number of tin(IV) and tellurium(IV) carboxylates and dithiocarbamates. The results show the regularity at which these types of compounds form secondary bonds (weak interactions), and the effect of the lone pair of tellurium(IV) on the geometries formed. The area has been studied through the determination of the following crystal structures: i) monocarboxylates: Ph3SnOCOCH2Cl, Ph3SnOCOCHCh, Ph3SnOCOCCh.MeOH. Ph3SnOCOCCh and Ph3TeOCOCCh. ii) dicarboxulates : Ph2Sn(OCOCH3)2, Ph2Sn(OCOCH2CI)2 and Ph2Te(OCOCCI3)2 iii) dithiocarbamates : Ph2Te(S2CNEt2)2, Ph2Te(S2CN(Et)(Ph))2 and Ph2Te(S2CNPh2)2 In addition to these, six hydrolysis products of Ph3SnOCOCCh are reponed. These com- pounds show the varied results that are obtained from the facile dearylation of the organotin com- pound by a strong organic acid in the presence of water. The following structures are reported: Ph2 Sn(OH)(OCOCCh), {[Pb2Sn(OCOCCh)hOh (two isomers), [(PbSn))(Oh(OCOCCh)sh, [PhSn(O)(OCOCCh)]6 and [(Ph 2 Sn)2(OH)(OCOCCh)3h.