<p>LiMn₂O₄ is ideal as a high-capacity Li-ion battery cathode material by virtue of its low toxicity, low cost, and the high natural abundance of Mn. Surface related reactions and bulk kinetics have been the major focus of this work. The main techniques exploited have been: electrochemical cycling, X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectroscopy and thermal analysis.</p><p>Interface formation between the LiMn₂O₄cathode and carbonate-based electrolytes has been followed under different pre-treatment conditions. The variables have been: number of charge/discharge cycles, storage time, potential, electrolyte salt and temperature. The formation of the surface layer was found not to be governed by electrochemical cycling. The species precipitating on the surface of the cathodes at ambient temperature have been determined to comprise a mixture of organic and inorganic compounds: LiF, Li_xPF_y (or Li_xBF_y, depending on the electrolyte salt used), Li_xPO_yF_z (or Li_xBO_yF_z) and poly(oxyethylene). Additional compounds were found at elevated temperatures: phosphorous oxides (or boron oxides) and polycarbonates. A model has been presented for the formation of these surface species at elevated temperatures. </p><p>The cathode surface structure was found to change towards a lithium-rich and Mn³⁺-rich compound under self-discharge. The reduction of LiMn₂O₄, in addition to the high operating potential, induces oxidation of the electrolyte at the cathode surface.</p><p>A novel <i>in situ</i> electrochemical/structural set-up has facilitated a study of the kinetics in the LiMn₂O₄ electrode. The results eliminate solid-phase diffusion as the rate-limiting factor in electrochemical cycling. The electrode preparation method used results in good utilisation of the electrode, even at high discharge rates.</p>

<p>Crystallization of C₆₀ and C₇₀ from organic solution often leads to the formation of new solvates and other fullerene compounds. In the present thesis, a number of such solvates were obtained and their phase transitions studied using <i>in situ</i> "in solution" techniques. New fullerene materials can be also obtained using High Pressure High Temperature (HPHT) treatment. The formation of C₆₀ polymers in thin films and bulk samples has been studied in situ over a wide pressure-temperature range.</p><p>New methods for single-crystal growth of fullerenes and their compounds have been developed. It was found by <i>in situ</i> "in solution" XRD and Raman spectroscopy that solvate C₆₀ crystals with benzene, toluene and hexane are stable only in equilibrium with their solution. Their melting points coincide with the maximum in the temperature dependence of solubility. C₇₀ solvates grown from these solutions are stable out of solution, and decompose above the boiling points of the solvents. Vibrational signatures were found for the C₆₀ and C₇₀ solvates which are very similar to these for fullerene-sulfur compounds obtained as thin films and single crystals. A new C₇₀S₈ compound was obtained as relatively large single crystals. </p><p>C₆₀ polymerisation under HPHT conditions was studied on thin films and showed a thickness effect on the phase transition around 20 GPa. Superhard and superelastic films were obtained by treatment at 23 GPa and 570K. In situ Raman and XRD studies were performed on bulk samples at pressures up to 27 GPa and temperatures up to 850K. Below 13 GPa, only one- and two-dimensional polymers were found to form during the heating. The observed polymerisation pathway suggests a gradual increase in polymerisation. Above 18 GPa, the <i>in situ</i> Raman spectra obtained during heating remained almost unchanged. The XRD study showed that heating at 830K and 13 GPa leads to the formation of a rhombohedral phase with a volume per C₆₀ molecule of 560-570 ų/M, which is below the value for two-dimensional polymers. Nevertheless, no superhard, highly dense phases were observed under these conditions, in contrast to previous studies.</p>

<p>Thin films of refractory metals and carbides have been studied extensively over many years because of their wide range of application. The two major techniques used are Chemical Vapour Deposition (CVD) and Physical Vapour Deposition (PVD). These can result in the deposition of two-dimensional blanket or patterned thin films. Laser-assisted Chemical Vapour Deposition (LCVD) can provide a maskless alternative for localised deposition in two and three dimensions. This thesis describes LCVD of micrometer-sized tungsten, molybdenum and tungsten carbide rods. The kinetics, phase composition and microstructure have been studied as a function of in situ measured laser induced deposition temperature.</p><p>Tungsten and molybdenum rods were deposited by hydrogen reduction of their corresponding hexafluorides, WF6 and MoF6, respectively. Single crystal and polycrystalline tungsten rods were obtained, depending on the H2/WF6 molar ratio and deposition temperature. The molybdenum rods were either single crystals or dendritic in form depending on experimental conditions. The field emission characteristics of the tungsten single crystals were investigated. The results showed LCVD to be a potential fabrication technique for field emitting cathodes.</p><p>Nanocrystalline tungsten carbide rods were deposited from WF6, C2H4 and H2. TEM analysis showed that the carbide rods exhibited a layered structure in terms of phase composition and grain size as a result of the temperature gradient induced by the laser beam. With decreasing WF6/C2H4 molar ratio, the carbon content in the rods increased and the phase composition changed from W/W2C to WC/WC1-x and finally to WC1-x/C.</p>

<p>Five-membered rings are readily prepared by <i>5-exo-trig</i> radical cyclization. This thesis is concerned with novel methodology for pyrrolidine synthesis. We have synthesised selenium containing radical precursors from aziridines and α-phenylseleno ketones, and cyclized them to 2,4- and 3,4-disubstituted pyrrolidines. A few examples of <i>5-exo-dig</i> cyclization were also demonstrated. In another study we investigated the capacity of the nitrogen protecting group to direct diastereoselectivity in the formation of 2,4-disubstituted pyrrolidines. The diphenylphosphinoyl protecting group directed cyclization to occur in a highly <i>cis</i>-selective manner. When cyclizations were performed at 17 ^oC, <i>cis</i>/<i>trans</i>-ratios as high as 24/1 were obtained. In contrast, cyclization of the unprotected pyrrolidine precursor afforded the <i>trans</i>-diastereomer as the major product (<i>cis</i>/<i>trans </i>= 1/3.3 – 1/20). We also examined the use of a hydroxyl auxiliary for controlling diastereoselectivity in radical cyclization. The required selenium containing radical precursors were synthesised from 2-cyanoaziridines by addition of organometallic reagents, reduction of the resulting aziridine ketone, and benzeneselenol ring-opening of the aziridine. Cyclization at 17 ^oC produced 2,4-disubstituted pyrrolidines substantially enriched in the <i>trans</i>-isomer (<i>cis</i>/<i>trans</i> = 1/9 – 1/12). Novel radical cyclization approaches to thiazolines and pyrrolines were also tried.</p><p>The thesis also describes attempts to improve the Hassner aziridine synthesis by employing stannous chloride as a functional group tolerant reducing agent.</p>

<p>One important driving force in nanotechnology today is the change which can be made in the properties of a material when the dimensions of its individual building blocks are decreased below approximately 100 nm. Such small building blocks, typically nanoparticles, may induce new and unique properties compared to those of the corresponding bulk material. The challenge in nanotechnology is to make nanoparticles with a discrete particle size within the range 1-10 nm. It is also important to develop appropriate assembly methodologies in order to construct devices composed of such small building blocks.</p><p>This thesis reports iron nanoparticle synthesis using laser-assisted photolysis of ferrocene. The particles were protected against oxidation by a carbon shell formed in situ during their growth. By varying the experimental conditions such as fluence, repetition rate and laser beam area, particles could be synthesized in the size range 1 to 100 nm. Their size was measured using a differential mobility analyser (DMA), transmission electron microscopy (TEM) and X-ray diffraction (XRD). DMA was also used successfully to size-select particles to facilitate the deposition of monodisperse nanoparticle films.</p><p>A theoretical "residence time approach (RTA)" model was developed to relate particle volume to the laser parameters used. The growth of these particles was studied in situ using optical emission spectroscopy; the results were compared with those from quantum mechanical calculations. The particles were characterised ex situ by TEM, convergent beam electron diffraction, XRD, X-ray photoelectron spectroscopy and Raman spectroscopy. Results from the TEM investigations revealed that the carbon shell was graphitic close to the iron core, while the outer part of the carbon shell was amorphous, indicating different growth mechanisms. Both bcc and fcc iron particles were observed. </p>

<p>This thesis ties some electrochemical aspects of development and fabrication of an analytical system on a microchip together. These aspects develop through the fundamentals of amperometric detection in microsystems and microfabrication via the interaction of electrochemical detection and electrophoretic separation finally to the interfacing of a microsystem to the macro world.</p><p>Paper <b>I</b> deals with amperometric detection in microscale systems and describes the fabrication of the necessary on-chip microelectrodes together with fluidic channels in silicon. It was furthermore studied, if the interelectrode distance of some μm could be used to improve the sensitivity in amperometric detection by employing redox cycling. </p><p>Papers <b>II</b>, <b>III</b> and <b>IV</b> deal with the effect of a high voltage field on amperometric detection. In analytical microdevices typically an electrophoretic separation step (e.g. capillary electrophoresis, CE) precedes the detection. The interference of the CE high voltage with the amperometric detection potential is often considered one of the main hindrances for an effective combination of these techniques. In paper <b>II</b> one reason for the observed disturbing potential shift was elucidated. It was shown that positioning of working electrode and reference electrode on an equipotiental surface eliminates this problem. Paper <b>III</b> reports an application of this technique. In paper <b>IV</b> it could be shown that this approach could further be used to significantly reduce the instrumental requirements for amperometric detection in CE.</p><p>Papers <b>V</b>, <b>VI</b>, <b>VII</b>, finally discuss the interfacing of low volumetric flows that typically occur on microanalytical devices to other techniques. Both, interfacing from liquid to liquid phase (μLC to CE in paper <b>V</b>) and from liquid to gas phase (CE to MS in paper <b>VI</b> and <b>VII</b>) were discussed. Electrochemical methods are used in this context to evaluate the stability and, in paper <b>VI</b> and <b>VII</b>, to increase the understanding of underlying processes of corrosion.</p>

<p>Smaller cellular telephones and more energy-efficient windows are just two examples of technological advances which call for new materials. Materials chemists seek to develop new materials, both out of pure curiosity to see which combination of elements and structures can be obtained and in efforts to produce materials, with specific properties. The starting materials (in solid, liquid or gaseous form) can then be combined and prepared in various ways. A chemical method that is gaining more attention for thin-film growth is Atomic Layer Deposition (ALD). This is a sophisticated type of vapor deposition in which the precursor gases are introduced separately into the reaction chamber.</p><p>Silicon carbide (SiC) and cubic boron nitride (c-BN) are extremely hard diamond-like materials, both with a high potential for application within the modern microelectronics and tool industry. Hexagonal boron nitride (h-BN), with its graphite-like layered structure, is a promising ceramics material.</p><p>Deposition of thin SiC and BN films from gaseous precursors has been studied by theoretical and experimental methods. The chemical composition and atomic arrangement of a growing surface is important for vapor growth. The surface may be terminated (e.g., by hydrogen atoms) and adopt various geometrical structures. Reconstruction of unterminated SiC(0001) surfaces, as well as H abstraction from the corresponding H-terminated surfaces, were studied using quantum mechanical calculations. Elementary reactions for vapor growth of SiC and BN, and <i>in situ</i> incorporation of dopant and contaminant species into these surfaces were also investigated theoretically. Moreover, thin films of BN were deposited by means of laser-assisted ALD. The general goal has been to predict and/or explain experimental results by investigating growth mechanisms.</p>

<p>Catalysis has a profound impact on all living species on the earth. Nature’s catalysts, the enzymes, have the ability to selectively promote a specific bio-chemical transformation, given the required substrate. As well as being highly selective, enzymes enhance the speed of these reactions, helping them to run at temperatures much lower than normally required, i.e. at body temperature. In comparison, reactions used in the production of new materials such as polymers, medicines, fragrances, petrochemicals, etc. are often catalyzed by transition metals. This thesis describes how the selectivity and activity of these catalysts can be influenced via two conceptually different methods: chelation control and microwave heating. The thesis primarily focuses on regio- and stereochemical aspects of the palladium-catalyzed arylation of olefins, i.e. the Heck reaction. Reaction rate enhancement of both palladium and enzyme (polymerase chain reaction [PCR]) catalysis by microwave heating is also discussed. </p><p>Novel chelation-controlled palladium-catalyzed multi- and asymmetric arylations of vinyl ethers were performed, resulting in tetra-substituted olefins as well as chiral quaternary carbon centers with excellent optical purity. In addition, a new synthetic route to diarylated ethanals, relying on a double chelation-controlled regioselective arylation followed by hydrolysis, has been discovered. High temperature conditions, using microwave heating, substantially reduce the reaction time for ligand-controlled asymmetric Heck arylations, while retaining levels of enantioselectivity in most cases. In addition, a potentially useful fast synthetic protocol for the employment of aryl boronic acids in oxidative Heck arylation was developed. Finally, microwave-assisted PCR was described for the first time; this method allows reductions in the run time of 50%.</p>

<p>This thesis is based on ten publications (Papers I-X). The phosphodiester backbone makes DNA or RNA to behave as polyelectrolyte, the pentose sugar gives the flexibility, and the aglycones promote the self-assembly or the ligand-binding process. The hydrogen bonding, stacking, stereoelectronics and hydration are few of the important non-covalent forces dictating the self-assembly of DNA/RNA. The pH-dependent thermodynamics clearly show (Papers I and II) that a change of the electronic character of aglycone modulates the conformation of the sugar moiety by the tunable interplay of stereoelectronic anomeric and <i>gauche</i> effects, which are further transmitted to steer the sugar-phosphate backbone conformation in a cooperative manner. 3'<i>-</i>anthraniloyl<b> </b>adenosine<b> </b>(a mimic of 3'-teminal CC<u>A</u>_OH of the aminoacyl-tRNA^Phe) binds to EF-Tu*GTP in preference over 2'<i>-</i>anthraniloyl<b> </b>adenosine<b>, </b>thereby showing (Paper III) that the 2’-<i>endo</i> sugar conformation is a more suitable mimic of the transition state geometry than the 3’<i>-endo</i> conformation in discriminating between correctly and incorrectly charged aminoacyl-tRNA^Phe by EF-Tu during protein synthesis. The presence of 2'-OH in RNA distinguishesit from DNA both functionallyas well as structurally. This work (Paper IV) provides straightforward NMR evidence to show that the 2'-OH is intramolecularly hydrogen bonded with the vicinal 3'-oxygen, and the exposure of the 3'<i>-</i>phosphate of the ribonucleotides to the bulk water determines the availability of the bound water around the vicinal 2'-OH, which then can play various functional role through inter- or intramolecular interactions. The pH-dependent ¹H NMR study with nicotinamide derivatives demonstrates (Paper V) that the cascade of intramolecular cation (pyridinium)-π(phenyl)-CH(methyl) interaction in edge-to-face geometry is responsible for perturbing the p<i>K</i>_a of the pyridine-nitrogen as well as for the modulation of the aromatic character of the neighboring phenyl moiety, which is also supported by the T₁ relaxation studies and <i>ab initio</i> calculations. It has been found (Papers VI-IX) that the variable intramolecular electrostatic interaction between electronically coupled nearest neighbor nucleobases (steered by their respective microenvironments) can modulate their respective pseudoaromatic characters. The net result of this pseudoaromatic cross-modulation is the creation of a unique set of aglycones in an oligo or polynucleotide, whose physico-chemical properties are completely dependent upon the propensity and geometry of the nearest neighbor interactions (extended genetic code). The propagation of the interplay of these electrostatic interactions across the hexameric ssDNA chain is considerably less favoured (effectively up to the fourth nucleobase) compared to that of the isosequential ssRNA (up to the sixth nucleobase). The dissection of the relative strength of basepairing and stacking in a duplex shows that stability of DNA-DNA duplex weakens over the corresponding RNA-RNA duplexes with the increasing content of A-T/U base pairs, while the strength of stacking of A-T rich DNA-DNA duplex increases in comparison with A-U rich sequence in RNA-RNA duplexes (Paper X).</p>

<p>The usefulness of low concentrations (typically 10 to 100 <i>µ</i>M) of [¹¹C]carbon monoxide and aryl triflates as substrates in ¹¹C-carbonylation using different nucleophiles in the presence of lithium bromide was investigated. The reactions were performed in a micro autoclave of 200 <i>µ</i>L volume and catalysed (mediated) by palladium(0). </p><p>A peripheral type benzodiazepine receptor (PBR) ligand, 1-(2-chlorophenyl)-<i>N</i>-methyl-<i>N</i>-(1-methylpropyl)isoquinoline-3-carboxamide (PK11195) and its structural analogues including an irreversible ligand for PBR, some other amides, ketones and carboxylic acids, were all labelled with ¹¹C using this approach. The [<i>carbonyl</i>-¹¹C]PK11195, analogues and other amides were prepared from aryl triflates and amines, and the [<i>carbonyl</i>-¹¹C]ketones were prepared from aryl triflates and organoboranes. In the synthesis of [<i>carboxyl</i>-¹¹C]carboxylic acids, water was utilised as nucleophile. The decay-corrected radiochemical yields were 10 to 55% for [¹¹C]PK11195 and analogues, 2 to 63% for other [¹¹C]amides, 10 to 75% for [¹¹C]ketones and 25 to 65% for [¹¹C]carboxylic acids. The specific radioactivity of the labelled compounds was in the range of 150 to 900 GBq/<i>µ</i>mol. </p><p>Some [¹¹C]amines were prepared by a reductive amination of the corresponding [carbonyl-¹¹C]ketones. These reactions were performed using different amines in the presence of TiCl₄ and NaBH₃CN. The radiochemical yields of the [¹¹C]amines varied from 2 to 78% (determined by analytical HPLC). </p><p>In order to confirm the labelling position, synthesis of selected ¹³C-substituted compounds were performed. For each substance group/ synthesis method, a selected compound was synthesised using (¹³C)carbon monoxide and the ¹³C-substituted compound was then analysed by ¹³C NMR.</p><p>A synthetic route was developed for the preparation of 1-(2-chloro-phenyl)-isoquinolin-3-yl trifluoromethanesulfonate used as the precursor in the synthesis of [<i>carbonyl</i>-¹¹C]PK11195 and analogues.</p>