The impact of conformational analysis in chemistry was clearly demonstrated in 1969, during the tenure of this work, when the Nobel Prize for Chemistry was awarded to Professor D. H. R. Barton. The first part of this thesis deals with the vibrational analysis of biphenyl and its 4,4,-dihalogeuo derlvstlves with respect to the dihedral angle between the two rings. It is clearly demonstrated that change in conformation for biphenyl and 4,4'-difluorobinhenyl from D (solid state) to D2 symmetry (solution, molten and gaseous states) is accompanied by changes in position and spectral activity of certain normal modes. These shifts, together with supplementary data derived from some deuterated derivatives of biphenyl, give an estimate of the dihedral angle in the solution state. The structure of 4,4'-dichioro and 4,4,-dibromobiphenyl is irrespective of phase. The second part of the thesis presents the vibrational analysis of tetrahydropyran and its 4-chloro and 4-bromo derivatives. Variable temperature NMR measurements give a quantitative estimate of the con format loaal equilibrium. The final part of this work presents the liquid band shape analysis of tine 215 cm-1 band of hexsfluorobensene in mixed benzene-cyelohexane solvents. It is shown from the computed correlation functions that vibrational relaxation occurs during the split of the hexafluorobenzene-benzene complex.

Ce sujet de recherche ambitionne le contrôle du procédé de réalisation in situ de nano-objets en matrice diélectrique en vue du développement de nouvelles applications. Les matrices de silice comportant des nanoparticules métalliques et semi-conductrices ont suscité un intérêt considérable en recherche fondamentale et appliquée dans le cadre de l’amélioration des catalyseurs, capteurs, ou de composant optiques linéaires et non linéaires. L’utilisation d’une irradiation laser est souvent mentionnée comme méthode prometteuse de croissance localisée. L’objet de ce travail est d’explorer les différentes possibilités de photo-cristallisation de différents types de nanoparticules dans des matrices poreuses ou vitreuses, en faisant varier les conditions de dopage et d’irradiation. Dans cette thèse, des monolithes de silice poreuse produits par le procédé sol-gel ont été post-dopés et densifiés. Une méthode simple, basée sur une irradiation laser, a été développée pour localiser la croissance des nanoparticules semi-conductrices (PbS, CdS) ou métalliques (Au, Ag) à l'intérieur de la matrice de silice poreuse. Les nanoparticules sont précipitées localement sous la surface du xérogels de silice en utilisant un laser visible continu, ou encore dans son volume par une irradiation infrarouge en régime femtoseconde. Il est ainsi apparu qu’une croissance par irradiation en régime femtoseconde dans le domaine infrarouge procède de mécanismes tout à fait différents de ceux d’une synthèse par insolation continue, où le thermique a un rôle prépondérant. Par ailleurs, il est montré que la taille des nanoparticules peut être ajustée par le choix de la concentration des précurseurs dans la solution de post-dopage, par la longueur d’onde du laser, sa puissance ou par la température dans le cas de la précipitation thermique. En outre, différentes méthodes ont été utilisées pour précipiter des nanoparticles métalliques (Ag, Cu) à l’intérieur d’une matrice de silice dense. Ces techniques sont basées soit sur la combinaison d’une insolation laser et d’un traitement thermique, soit uniquement sur des traitements thermiques sous des atmosphères différentes. La structuration spatiale de ces nanoparticules est effectuée par irradiation laser à impulsions, suivie d’un recuit à 600°C. Enfin, le dopage de verre massif par des nanoparticules de Cu a permis d’envisager leur utilisation pour fabriquer des cœurs de fibres optiques micro-structurées dopés. Les premiers tirages de capillaires ont montré que les nanoparticules de Cu peuvent être préservées après avoir subi une fusion à 2000°C. / The thesis project aims to master the localization and organization of metallic and semiconducting nano-objects formed inside sol-gel silica materials for novel applications. The nanostructuration method used in this thesis is based on the laser irradiation and, if necessary, heat-treatment. The local character of the matter-light interaction leads to the formation of nano-objects only in the irradiated areas. Hence, it is possible to control the spatial distribution of the nano-crystallites as well as their size distribution by varying the irradiation parameters. In this thesis, porous silica monoliths produced via the sol-gel process were doped and densified. Different kinds of semiconductors (CdS, PbS) and metallic (Au, Ag) nanoparticles incorporated inside the porous SiO2 matrix have been precipitated with the assistance of laser irradiation at room temperature or by an annealing process. The local generation of nanoparticles could be performed directly on the surface of the silica xerogel using a visible continuous laser or inside the volume of the matrix by a femtosecond laser irradiation. Moreover, it has been shown that the nanoparticle size could be adjusted by choosing the concentration of the precursors in the post-doping solution, the laser wavelength, the irradiation power and/or the annealing temperature in the case of thermal precipitation. Furthermore, different methods were used to precipitate metallic nanoparticles (Ag or Cu) inside dense silica matrix. Those techniques are based on laser irradiations and/or heat treatments. Under pulsed laser irradiation, the space selective growth of noble metal nanoparticles was achieved in two steps: first, metallic nucleation centres were generated by the pulsed laser (nanosecond or femtosecond) in the irradiated areas; next, the metallic nanoparticles growth was obtained by annealing at 600°C. Besides, the doping of glassy matrices with copper nanoparticles allows foreseeing their use in the core of microstructured optical fibres. First capillary drawings have shown that the copper nanoparticles can be preserved after undergoing a melting at 2000°C.

Cette thèse explore deux voies alternatives d’élaboration de l’émetteur bore des cellules à base de silicium cristallin de type n, afin de simplifier leur procédé de fabrication, d’une part, et d’améliorer leur rendement de conversion, d’autre part. La première voie, orientée transfert industriel, propose l’utilisation d’une couche diélectrique dopante (SiOx:B) déposée par PECVD-LF, recuite par diffusion thermique. Des paramètres d’émetteur similaires à ceux obtenus dans le cas d’une diffusion gazeuse BCl3 sont recherchés. La seconde approche, plus amont, envisage quant à elle l’élaboration d’un hétéro-émetteur en silicium microcristallin dopé bore (µc-Si:B), obtenu par cristallisation thermique d’une couche de silicium amorphe dopée bore, déposée par PECVD-RF. La formation d’un hétéro-émetteur bore à haute température vise l’obtention de Vco plus élevées sur cellules n-PERT. L’élaboration et le suivi des propriétés des couches SiOx:B ont permis de mettre en évidence différents phénomènes ayant lieu lors de la diffusion. La qualification du dopage et de la passivation de l’émetteur bore a montré de bonnes performances. L’utilisation du SiOx:B lors d’une étape de codiffusion a permis de réaliser des cellules de type n-PERT (239 cm²) selon deux procédés simplifiés (3 étapes de moins) avec les rendements les plus hauts atteints à notre connaissance (20%) sur la structure considérée. D’autre part, les couches µc-Si:B ont été développées puis caractérisées. Le potentiel électrique des hétéro-émetteurs associés a été évalué sur structure symétrique indiquant que des iVco supérieures à 700mV peuvent être atteintes. L’évaluation de la prise de contact sur ce nouvel émetteur a été réalisée par sérigraphie. A ce jour, un phénomène de cloquage limite néanmoins l’intégration de cet émetteur en cellule complète. / This thesis focuses on two alternative boron emitter elaboration routes for n-type crystalline silicon solar cells in order to simplify fabrication processes on one hand, and to improve conversion efficiencies on the other hand. The first route, driven by industrial integration concern, proposes the use of PECVD-LF boron-doped dielectric layers (SiOx:B), annealed by thermal diffusion. Emitter parameters similar to those made by BCl3 gaseous diffusion are obtained on n-type substrates. The second approach, which is more exploratory, considers a boron-doped microcrystalline silicon layers (µc-Si:B) made by boron-doped amorphous silicon crystallization. The elaboration of this high temperature hetero-emitter targets higher open-circuit voltages than standard n-PERT cells.SiOx:B layers elaboration and structural properties study highlighted several phenomena occurring during diffusion annealing. Doping and passivation qualification of associated boron emitters showed good performances. The use of SiOx:B layers during a dopant codiffusion step led to industrial size (239 cm²) n-PERT solar cells fabrication according to two simplified processes (3 steps suppression) with, what is to our knowledge, the highest published efficiencies (20%) on the considered structure. On the other hand, µc-Si:B layers were developed and characterized. The electrical potential of associated hetero-emitters was assessed on symmetrical devices showing that iVoc higher than 700mV can be reached. Contacting on this new emitter was evaluated by metal screen-printing. However, to date, blistering issues limit emitter integration into solar cells.

Stephen Charles Hsu. / Also issued as Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1988. / Includes bibliographical references. / Supported by the AT&TFoundation through a Bell Laboratories Ph.D. scholarship.

El objetivo de este trabajo ha sido caracterizar, bioquímica y funcionalmente, una GTPasa bacteriana, la proteína MnmE de E. coli, implicada en la modificación postranscricional de algunos tRNAs.MnmE es una proteína multidominio de 50 kDa que consta de un dominio N-terminal de ~220 residuos, un dominio medio de unión a GTP (dominio G) de ~160 residuos y un dominio C-terminal de ~75 aminoácidos que contiene la única cisteína presente en la molécula. MnmE es una GTPasa cuyas propiedades bioquímicas difieren ampliamente de las mostradas por las GTPasas reguladoras pertenecientes a la familia de las pequeñas GTPasas, típicamente representadas por Ras. MnmE tiene muy baja afinidad por nucleótido y una actividad GTPasa intrínseca alta; además, es capaz de multimerizar. El ciclo GTPasa funciona in vitro sin necesidad de factores adicionales tipo GAPs o GEFs. El dominio G de MnmE aislado conserva una afinidad similar por nucleótidos y la misma capacidad de hidrólisis del GTP que la proteína entera y, sin embargo, no presenta ningún subdominio activador GAP insertado, demostrando que MnmE es un nuevo ejemplo de proteína GTPasa que presenta un mecanismo de activación diferente al dedo de arginina.En este trabajo se ha demostrado que la hidrólisis del GTP realizada por la proteína MnmE es esencial para la función modificadora de los tRNAs. En nuestro modelo proponemos que la hidrólisis del GTP provoca los reordenamientos estructurales en la molécula que le permiten ejecutar su función modificadora. Si es así, MnmE sería el primer ejemplo de una enzima modificadora de tRNAs con actividad GTPasa.Además, en este trabajo hemos establecido la relación entre la presencia de la modificación introducida por MnmE en los tRNAs y la viabilidad celular, demostrando la importancia de la modificación química post-transcripcional para el proceso de descodificación celular, pues este proceso se ve gravemente perjudicado cuando mutaciones que inactivan funcionalmente MnmE se combinan con mutaciones en otros genes implicados en este proceso y que por sí solas no producen fenotipo aparente. / The Escherichia coli MnmE protein is a high evolutionarily conserved protein with GTPase activity. MnmE has a molecular mass of 50 kDa and is organized as a multidomain protein consisting of an ~220 amino acid N-terminal domain, a middle GTPase domain of about 160 residues, and a ~75 amino acid C-terminal domain, wich contains the only cysteine residue present in the protein. MnmE exhibits a very high intrinsic GTPase activity rate and low affinity for GTP and GDP and it can form self-assemblies, these unusual biochemical properties differs extensively MnmE from regulatory GTPase proteins such Ras.In vitro, the GTPase cycle works without any additional factor such GAPs or GEFs. The isolated GTPase domain roughly conserves the guanine binding and GTPase activities of intact MnmE molecule and strinkingly doesn't present any inserted activation subdomain. MnmE is a new example of a GTPase protein that follows an alternative activation mechanism without an arginine finger.MnmE is involved in the modification of the uridine at the wobble position of certain tRNAs. In this work we examine the biochemical and functional consequences of altering amino acid residues within the GTPase and C-terminal domain of MnmE. Our results indicate that the MnmE tRNA modifying function requieres effective hydrolysis of GTP and not only GTP binding as in most of the GTPases. We propose that MnmE uses the conformational change associated with GTP hydrolysis to promote the tRNAs modification reaction, in witch the C-terminal Cys may function as a catalytic residue. We also demonstrate thet point mutations abolishing the tRNA modifying function of MnmE confer synthetic lethality wich stresses the importance of the tRNA modification function in the mRNA decoding process.

Le développement des nanotechnologies offre de nouvelles perspectives pour la conception des cellules solaire à fort rendement de conversion. Jusqu’à présent les efforts se sont portés principalement sur des structures à base de semi-conducteurs, de métaux et de polymères. Dans nos travaux, nous avons considéré des nanoparticules de Sulfure de Plomb (PbS) pour lesquelles l'énergie de bande interdite et les propriétés optiques sont fonction de la taille de la particule afin de tirer parti de l'ensemble du spectre optique couvert par l'énergie solaire. Nous avons également considéré des nanofils d'oxyde de zinc (ZnO) pour la séparation et le transport des charges photo-crées. Nous pensons que l'association des nanoparticules de PbS avec des nanofils de ZnO devrait pouvoir augmenter considérablement le rendement des cellules solaires. Dans ce but, nous avons démontré la croissance auto-ordonné des nanofils de ZnO sur substrats silicium et verre par dépôt laser pulsé (pulsed laser deposition ) utilisant le réseau de nanoparois de ZnO en forme de nid d'abeille comme couche germe. Nous avons démontré que les conditions de croissance sont essentielles pour contrôler la cristallinité, la morphologie des nanofils de ZnO , ainsi que la densité de défauts de croissance. Les analyses MEB, DRX, TEM, et HR-TEM montrent que nous avons obtenu des nanostructures très cristallines et orientées verticalement. Nous avons également démontré la croissance in-situ de nanoparticules de PbS sans ligand sur la surface des nanofils de ZnO verticaux à l'aide de la technique SILAR (Successive Ionic Layer Adsoprtion and Reaction) .Nous avons constaté que les nanoparticules de PbS sont fortement accrochées à la surface des nanofils de ZnO avec différentes dimensions et des densités variables .Ces résultats ont été obtenus sans introduire de matière organique (Ligand) qui pourrait perturber à la fois la structure électronique à l'interface ZnO/PbS et le transfert des électrons du PbS au ZnO. Les analyses MEB, TEM et HR-TEM confirment le bon accrochage des nanoparticules de PbS sur les nanofils de ZnO . Leur forme est sphérique et elles sont poly-cristallines. A la fin de ce travail de thèse nous proposons une hétérojonction p-PbS/n-ZnO constituée de nanoparticules de PbS dopées P et de nanofils de ZnO dopés n pour de futures applications en photovoltaïque. / To date, the development of nanotechnology has launched new ways to design efficient solar cells. Strategies have been employed to develop nanostructure architectures of semiconductors, metals, and polymers for solar cells. In this research we have considered the Lead sulfide (PbS) nanoparticles with their tunable band gap and optical properties to harvest the entire solar spectrum which can improve the optical absorption, and charge generation. On the other hand, Zinc oxide (ZnO) nanowires will provide the charge separation and transportation. The ZnO Nanowires sensitized with PbS nanoparticles might significantly impact power conversion efficiency of the solar cells Driven by these unique properties, we demonstrate the successful growth of self catalyzed ZnO nanowires on silicon and glass substrates, by pulsed laser deposition (PLD) using ZnO nanowall network with honeycomb structure as seed layer. We identified that the growth parameters are vital to control the crystallinity, morphology and the defect levels in the synthesized ZnO nanowires. SEM, XRD, TEM, HRTEM analysis show that the nanostructures are highly crystalline and are vertically oriented. We also report the in-situ growth of PbS nanoparticles without linker on the surface of well –oriented ZnO NWs by (SILAR) technique. The PbS Nanoparticles are packed tightly on the surface of the ZnO Nanowires with different sizes and densities, without insulating nature organic ligands, which might affect both the electronic structure at the interface and the electron - transfer rate. The SEM, TEM, HRTEM, PL and XRD analysis, confirm the attachment of the spherical shape polycrystalline PbS nanoparticles. We propose at the end of the thesis the p-PbS /n-ZnO hetero-junction with its future applications in solar cells.

Los polímeros orgánicos, tanto naturales como sintéticos, son inherentemente combustibles y en presencia de una fuente de calor y de oxígeno se queman fácil y rápidamente. Aunque en los últimos años ha habido un incremento en el número de heteroelementos utilizados en compuestos retardantes a la llama, el mercado está todavía dominado por compuestos que contienen halógenos, especialmente cloro y bromo. Estos compuestos son excepcionalmente efectivos pero presentan el inconveniente que incrementan las cantidades de humos y productos de descomposición tóxicos y corrosivos que se desprenden durante la combustión del polímero. Como alternativa a estos, han surgido una nueva clase de resinas termoestables basadas químicamente en 3,4-dihidro-2H-1,3-benzoxazinas. Su síntesis es de gran simplicidad y se lleva a cabo por condensación de formaldehido con fenoles en presencia de aminas aromáticas en una relación molar determinada. Otra de las aproximaciones utilizadas recientemente ha sido el uso de compuestos organofosforados que han demostrado buena capacidad como retardantes a la llama para resinas epoxi a la vez que generan menos gases tóxicos y humos que los compuestos halogenados. El objetivo general de este trabajo ha consistido en el desarrollo de nuevos sistemas poliméricos termoestables resistentes al fuego, sin detrimento de las propiedades del material y no agresivos medioambientalmente. Se pretende mejorar las buenas propiedades de algunos materiales estándar actualmente empleados, resinas fenólicas y resinas epoxi, pero introduciendo la condición de no inflamabilidad mediante nuevos sistemas de ignifugación, basados en fósforo y nitrógeno, alternativos a los sistemas halogenados clásicos ampliamente utilizados en la actualidad, mucho más tóxicos y peligrosos para el medioambiente que los que se proponen como alternativa en este estudio. Para ello se ha llevado la síntesis y caracterización de sistemas entrecruzados basados en resina novolaca modificados en diferentes proporciones con anillos del tipo benzoxazina, utilizando un nuevo método de síntesis basado en el uso de 1,3,5-trifenilhexahidro-1,3,5-triazina. Se ha estudiado mediante calorimetría diferencial de barrido su comportamiento térmico así como la influencia que tienen los catalizadores en la temperatura de apertura de los anillos de benzoxazina. La estabilidad térmica de estos compuestos se ha estudiado mediante análisis termogravimétrico en atmósfera de nitrógeno y de aire. Estos sistemas presentan buena estabilidad térmica, aunque el tanto por ciento de modificación no parece influir en las propiedades térmicas de estos. Mediante análisis dinamomecánico se ha descrito que la modificación de resinas novolaca con anillos de benzoxazina permite obtener materiales con una buena integridad mecánica, pudiéndose establecer relaciones cualitativas de niveles de entrecruzamiento. La retardancia a la llama de estos materiales ha sido V-O y V-1 en función del grado de modificación según el test de inflamabilidad UL-94 V.En este trabajo también se han sintetizado compuestos epoxifosforilados para modificar los sistemas novolaca y novolaca-benzoxazina y estudiar sus propiedades térmicas, mecánicas e ignífugas. Estos glicidilos no contienen enlaces hidrolíticamente inestables y poseen óxido de fosfina en su estructura. Se ha sintetizado un nuevo monoglicidilfosfinato, el 10-óxido de 10-(2,3-epoxipropil)-9,10-dihidro-9-oxa-10-fosfafenantreno (DOPOGly) y un diglicidilo alifático que contiene óxido de fosfina en su estructura, el óxido de isobutilbis(glicidilpropiléter)fosfina (IHPOGly). El entrecruzamiento de resinas novolaca y novolaca-benzoxazina con DOPOGly y IHPOGly lleva a sistemas novolaca-epoxi y novolaca-benzoxazina-epoxi con distinto contenido de fósforo y diferente densidad de entrecruzamiento que no desprenden volátiles en la reacción de polimerización. Se ha podido ver mediante análisis termogravimétrico que la incorporación de enlaces C-P en estos sistemas disminuyen la estabilidad térmica de estos, a la vez que el contenido final de fósforo en los polímeros no influye en el resto carbonado a 800ºC en atmósfera inerte y si lo aumenta en atmósfera oxidante. Los sistemas novolaca-epoxifosforada presentan menor velocidad de degradación a grados de conversión elevados de acuerdo con la propuesta de formación de un residuo intumescente mientras que los sistemas novolaca-benzoxazina-epoxi presentan un mecanismo de descomposición complejo y no pueden relacionarse con la presencia de este. Al igual que en los sistemas novolaca-benzoxazina, se han podido establecer relaciones cualitativas de niveles de entrecruzamiento para los sistemas novolaca-benzoxazina-DOPOGly. Para los sistemas novolaca-IHPOGly y novolaca-benzoxazina-IHPOGly se han podido determinar la temperatura de transición vítrea que no había sido posible determinar por DSC y también las temperaturas de las transiciones secundarias que se han relacionado con la estructura química de los materiales. Finalmente, la adición de compuestos organofosforados a los sistemas novolaca y novolaca-benzoxazina de mayor grado de modificación, mejora su retardancia a la llama alcanzándose grados V-0 según el test UL-94 V. / Natural and synthetic organic polymers are inherently combustible and in presence of heat and oxygen source burn easy and quickly. Although in the last years there has been an increment in the number of heteroatoms used in flame retardant compounds, the market is still dominated especially by compounds that contain halogens, like chlorine and bromine. These compounds are exceptionally troops but they have the shortcommings as the increase in the quantities of smoke and toxic gases and corrosive decomposition products that come off during the polymer combustion. As alternative to these a new class of thermostable resins chemically based in 3,4-dyhidro-2H-1,3-benzoxazines has arisen. Its synthesis is of great simplicity and it is carried out by formaldehyde condensation with phenols in presence of aromatic amines in a fixed molar relationship. At the same time another of the approaches used recently has been the use of organophosphorated compounds that have demonstrated good capacity like flame retardants for epoxy resins because they generate less toxic gases and smoke that the halogenated compounds. The general objective of this work has been the development of new fire retardant thermosettings systems, keeping the material properties and environmentally friendly. The goals is to improve the good properties of some standard materials, phenolic and epoxy resins, but introducing the non inflammability character by means of new ignifugation systems, based on phosphorous and nitrogen, alternative to the classic halogenated systems widely used at the present time. The synthesis and characterization of novolac resin systems modified in different proportions with benzoxazine rings, using a new synthetic method based on the use of 1,3,5-triphenilhexahydro-1,3,5-triazine has been carried out. Their thermal behavior has been studied by differential scanning calorimetry as well as the influence that catalysts have in the ring opening reaction of benzoxazine rings. The thermal stability of these compounds has been studied using thermogravimetric analysis under nitrogen and air atmosphere. These systems show good thermal stability, and the chemical modification seem not to influence the thermal properties. Materials with good mechanical integrity have been obtained from the novolac-benzoxazine resins. Dynamomechanical analysis allowed us to establish qualitative relationships of crosslinking density and modification degree. V-O and V-1 were obtained when the materials were tested to according to the UL-94 V flammability test.Moreover, in this work, two epoxyphosphorated compounds have also been synthesized to modify novolac and novolac-benzoxazine systems and to study its thermal, mechanical and fireproof properties: 10-(2,3-epoxypropyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPOGly), and an aliphatic diglycidilic compound that contains phosphine oxide moieties in its structure, isobutylbis(glycidylpropylether) phosphine oxide (IHPOGly). These glycidylic compounds do not contain hydrolytically unstable bonds and possess phosphine oxide moieties in their structure. Novolac and novolac-benzoxazine resins crosslinked with DOPOGly and IHPOGly lead to systems with different phosphorous content and different crosslinking density. By means of thermogravimetric analysis it has been shown that the incorporation of C-P bonds in these systems diminishes their thermal stability. Moreover the char yield at 800ºC increased with the phosphorous content under air atmosphere, while it do not undergo significative changes under nitrogen atmosphere. Novolac-epoxy phosphorated systems show lower degradation rate at high conversion degrees than the non-phosphorous systems according to the formation of an intumescent char. The novolac-benzoxazine-epoxy systems show a complex decomposition mechanism that cannot be related to the presence of phosphorous. Like in novolac-benzoxazine systems, for the novolac-benzoxazine-DOPOGly systems we have been able to establish qualitative relationships of crosslinking levels. For novolac-IHPOGly and novolac-benzoxazine-IHPOGly systems the glass transition temperature have been measured by DMA. Moreover secondary relaxations that have been observed and related to the chemical structure of the materials. Finally, the addition of organophosphorated compounds to novolac and novolac-benzoxazine systems improves its flame retardancy and degrees V-0 according to the UL-94 V test have been reached.

Design and Synthesis of New Polyaromatic Scaffolds for Nano-Scale ApplicationsResumen: En la última década, el diseño y la síntesis de nuevos sistemas poliaromáticos han resultado de gran interés gracias a sus propiedades únicas y sus aplicaciones potenciales para la obtención de dispositivos electrónicos, y como precursores de fullerenos. Hemos estudiado el mecanismo que procede a través de la activación del enlace C-H en la reacción intramolecular de arilación directa catalizada por paladio, para la formación de sistemas biarílicos, demostrando que la reacción procede a través de la abstracción del protón asistido por la base. Aplicando condiciones optimizadas hemos preparado la molécula C60H24 que al ser irradiada da lugar a la formación del fullereno C60, mediante la reacción de arilación directa formando seis nuevos enlaces C-C en una única etapa. Además, en una colaboración interdisciplinar con físicos teóricos y experimentales, en el proyecto PicoInside, hemos participado en el diseño y la síntesis de moléculas poliaromáticas para su posterior aplicación como dispositivos electrónicos moleculares.Abstract:In the last decade, the design and synthesis of new polyaromatic scaffolds have attracted a broad interest due to their exceptional properties and their potential applications in material science like molecular electronic devices and as precursors of fullerene.Based in the intramolecular palladium-catalyzed direct arylation reaction we developed new procedures as reliable tools for the biaryl coupling through C-H activation. Insight mechanistic studies showed a proton abstraction mechanism assisted by the base rather than activation of aromatic systems towards electrophilic attack. Applying optimized reaction conditions, formation up to six C-C bonds, and in situ dehydrogenation, allows for the synthesis of C60H24, crushed fullerene in one single step that upon laser irradiation leads to C60 fullerene. Moreover, in an interdisciplinary collaboration with theoretical and experimental physicist, PicoInside project, we have participated in the design and synthesis of Y-shaped polyaromatic molecules required for single molecule electronic devices.

Three key enhancements were made to a semiempirical molecular orbital program to develop a fast, accurate method of calculating chemical properties of large (> 1000 atom) molecular systems, through the use of quantum theory. In this thesis the key enhancements are presented which are: the implementation of a divide-and-conquer approach to a self-consistent field procedure, in an effort to improve capability; the use of the novel technology, GPU technology, to parallelize the divide-and-conquer self-consistent field procedure, in an effort to improve the speed; the implementation of a newly developed semiempirical model, the Polarized Molecular Orbital Model, in an effort to improve the accuracy. The development of a divide-and-conquer approach to the SCF (DC-SCF) procedure (enhancement 1) was carried out using saturated hydrocarbon chains whereby the saturated hydrocarbon chain is partitioned into small overlapping subsystems and the Roothaan equations solved for each subsystem. An investigation was carried out to find the optimal partitioning scheme for saturated hydrocarbon chains in order to minimize the loss of energy experienced from neglecting some of the interactions in the system whilst maintaining near linear scaling with system size. The DC-SCF procedure was shown to be accurate to 10-3 kcal mol-1 per atom whilst calculating the SCF-energy nearly 6 times faster than using the standard SCF procedure, for a 698-atom system. The development of a parallel DC-SCF procedure and Cartesian forces calculation for use on a GPU (enhancement 2), resulted in a hybrid CPU/GPU DC-SCF implementation that calculated the energy of a 1997-atom saturated hydrocarbon chain 21 times faster than the standard serial SCF implementation and a accelerated Cartesian forces calculation that performed 7 times faster for a saturated hydrocarbon chain of 1205-atoms, when accelerated using an NVidia Tesla C2050 GPU. The hybrid CPU/GPU algorithm made use of commercially accelerated linear algebra libraries, CULA and CUBLAS. A comparison was made between CULA’s accelerated eigensolver routine and the accelerated DC-eigensolver (developed in this research) and it was found that for saturated hydrocarbon chains of > 350 atoms, the accelerated DC-eigensolver performed around twice as fast as the accelerated CULA eigensolver. The implementation of the Polarized Molecular Orbital model (enhancement 3) was validated against published isomerization energies and benchmarked against the non-nitrogen containing complexes in the S66 database. The benchmark complexes were categorized according to dominant intermolecular interactions namely, hydrogen bonding, dispersion interactions and mixed interactions. After assessment it was found that the PMO model predicts interaction energies of complexes with a mixture of dispersive and electrostatic interactions to the highest accuracy (0.69 kcal mol-1 with respect to CCSD(T)/CBS). The dispersion correction within the PMO model was found to ‘overcorrect’ the dispersive contribution for most complexes tested. The outcome of this research is a semiempirical molecular orbital program that calculates the energy of a closed-shell saturated hydrocarbon chain of ~2000 atoms in under 4 minutes instead of 1.5 hours when using a PM3-Hamiltonian and can calculate interaction energies of systems exhibiting a mixture of electrostatic and dispersive interactions to an accuracy of within 1 kcal mol-1 (relative to high-level quantum methods). To demonstrate a suitable application for the enhanced SE-MO program, interaction energies of a series of PAHs with water, phenol and methanol have been investigated. The resultant program is suitable for use in calculating the energy and forces of large material and (in future) biological systems by a fast and accurate method that would be impractical or impossible to do without these enhancements.

In this thesis, non-modified POx, namely PnPrOx and PcycloPrOx, with an LCST in the physiological range between 20 and 37°C have been utilized as materials for three different biofabrication approaches. Their thermoresponsive behavior and processability were exploited to establish an easy-to-apply coating for cell sheet engineering, a novel method to create biomimetic scaffolds based on aligned fibrils via Melt Electrowriting (MEW) and the application of melt electrowritten sacrificial scaffolds for microchannel creation for hydrogels. Chapter 3 describes the establishment of a thermoresponsive coating for tissue culture plates. Here, PnPrOx was simply dissolved in water and dried in well plates and petri dishes in an oven. PnPrOx adsorbed to the surface, and the addition of warm media generated a cell culture compatible coating. It was shown that different cell types were able to attach and proliferate. After confluency, temperature reduction led to the detachment of cell sheets. Compared to standard procedures for surface coating, the thermoresponsive polymer is not bound covalently to the surface and therefore does not require specialized equipment and chemical knowledge. However, it should be noted that the detachment of the cell layer requires the dissolution of the PnPrOx-coating, leading to possible polymer contamination. Although it is only a small amount of polymer dissolved in the media, the detached cell sheets need to be washed by media exchange for further processing if required. ... / In dieser Dissertation wurden die unmodifizierten Poly(2-oxazoline) PnPrOx und PcycloProx, welche eine LCST im physiologischen Bereich zwischen 20 und 37°C aufweisen, für drei verschiedene Biofabrikationsansätze verwendet. Deren Thermoresponsivität und Prozessierbarkeit wurde genutzt, um ein simples Beschichten von Oberflächen für Cell Sheet Engineering, eine neue Methode zur Herstellung biomimetischer Gerüststrukturen basierend auf der Generierung von Fibrillenbündeln via Melt Electrowriting und die Anwendung als Opferstrukturen zur Generierung von Mikrokanälen in Hydrogelen zu etablieren.