"Self-assembled monolayers (SAMs) are organized molecular assemblies that are formed by spontaneous adsorption of a compound in solution to a surface (e.g. alkanethiols on gold). The design, preparation, and characterization of several self-assembled monolayers and multilayers on surfaces (gold, indium tin oxide and quartz) are described. The systems were chosen based on their ability to form ordered films and to perform a given device function. SAMs were fabricated with selected functional groups at the air-monolayer interface, capable of complexing metal ions (e.g. dicarboxypyridine, dicarboxybenzene, imidazole, 4-hydroxypyridine) with the purpose of using these SAMs to construct multilayered films. Deposition of a second layer consisting of metal ions (e.g. Cu(II), Co(II) and Fe(III)), occurs by non-covalent metal ligand binding interactions between the metal ion layer and the different organic ligands on the surface. Deposition of subsequent layers was achieved by the incorporation of the appropriate organic ligands and metal ions. These monolayers and multilayered films were characterized by contact angle measurements, ellipsometry, grazing angle FT-IR, cyclic voltammetry and impedance spectroscopy following deposition of each layer on the film. Electrochemical analysis of the multilayered films shows alternating insulating/conducting behavior (cyclic voltammetry) and alternating changes in films capacitance (impedance spectroscopy) depending on the outermost layer of the film. Films capped with an organic layer show low conductivity, while films capped with a metal layer show conducting behavior. The electrochemical behavior of the films is related to the degree of “leakiness” or electrolyte solution permeation through the film, which is high for films with metal layers as the top layer and decreases once the film is capped with an organic layer. The alternating conducting/insulating behavior of the films allows for fabrication of multilayered thin films of variable thickness and tunable conducting properties. Ordered films were fabricated with up to seven layers of dicarboxypyridine and Cu(II), and 4-hydroxypyridine and Fe(III) metal-ligand units. The construction of these films provides an example of molecular films that could function as molecular wires or junctions due to their controllable electrochemical properties. Photocurrent generating films were fabricated by incorporation of chromophore groups (e.g. pyrene, porphyrins) into the multilayered structures. These films generate cathodic or anodic current upon photoexcitation of the chromophores. The monolayers functionalized with different organic ligands were also used to study lanthanide complexation on the surfaces. Successful deposition of different lanthanide ions was achieved from DMSO solutions. Monolayers of a bicyclic structure, 4, 7, 13, 16-tetraoxa-1,10,21-triaza-bicycle[8.8.5] tricosane-19,23-dione, attached to a hexadecanethiol molecule were used to study the ability of metal ion detection on the surface using electrochemical (cyclic voltammetry and impedance spectroscopy) techniques. The SAMs show higher complexation affinity for Li+ than for Na+ or K+. Preliminary studies were also carried out to investigate the ability of different SAMs to cell adhesion interactions. Future experiments will help elucidate a systematic relation of cell adherence and the bulk and molecular-level properties of the functionalized surfaces. The different multilayered films described in this dissertation served as preliminary models for different molecular scale device applications. Current work is focused in the design and preparation of more efficient photocurrent generating films, highly selective sensors for different types of ions, surfaces for cell adhesion and microbial interactions, and the study of other potential applications such as the design of micro and nanofluidic devices. "

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Dans le cadre de la recherche de vecteurs d'énergie “propres”, le borazane et ses dérivés amine-boranes sont devenus des candidats intéressants en tant que matériaux de stockage de l'hydrogène en raison de leur pourcentage massique relativement élevé en hydrogène (19,6% pour borazane) et de la réversibilité potentielle de la réaction de déshydrogénation. Pour des applications réelles, le contrôle des réactions se produisant à la température ambiante est fondamental. Dans ce contexte, la compréhension du processus de la déshydrogénation/déshydrocouplage catalytique de l'amine-borane apparaît comme un élément important. Dans cette thèse, les catalyseurs de types métallocènes du Groupe IV (Cp2M, M = Ti, Zr et Hf) sont étudiés en détail. Le déshydrocouplage de HMe2N·BH3 catalysé par le titanocène a été étudié à la fois expérimentalement et théoriquement mais aucun accord n'avait été atteint auparavant. Dans ce travail, les caractérisations systématiques des interactions 3-centre 2-électron M···H-B impliquées dans les intermédiaires réactionnels ont été réalisées avec des approches topologiques QTAIM et ELF. Par la suite, des mécanismes réactionnels détaillés ont été étudiés. Les résultats théoriques ont démontré que la méthode DFT corrigée avec la dispersion (DFT-D) étaient nécessaire et suffisantes pour une description énergétique correcte des chemins réactionnels. Mon travail a également permis l'identification d'un complexe de van der Waals jouant un rôle clé dans le mécanisme réactionnel en accord avec les observations expérimentales. / With the increasing demand of clean energy carriers, ammonia borane and its related amine-borane compounds have emerged as attractive candidates for hydrogen storage materials due to their relatively high weight percentage of available hydrogen (19.6% for ammonia borane) as well as the potential reversibility for the hydrogen release reactions. Actual applications would benefit from controlled reactions occurring close to room-temperature. In this context, catalytic dehydrogenation/dehydrocoupling of amine-borane appears as a promising solution. In this thesis the Group IV metallocene (Cp2M, M = Ti, Zr and Hf) are mainly discussed. The dehydrocoupling of HMe2N·BH3 catalyzed by titanocene was investigated both experimentally and theoretically but no agreement were reached. In this work, systematic characterization of M···H-B 3-center 2-electron interactions involved in reaction intermediates were carried out with QTAIM and ELF topological approaches. Afterwards, detailed mechanisms were further studied. Computational results have demonstrated that the dispersion corrected DFT (DFT-D) method was indispensable for a correct enegetic prediction for reaction pathways. The identification of a van der Waals complexe also plays a central role for a reaction mechanism with good agreement with experimental observations.