Depuis quelques années, la recherche et le développement dans le domaine des matériaux électroluminescents suscite de plus en plus d’intérêt. La crise énergétique que nous connaissons actuellement motive un changement de mentalité de la société, de plus en plus soucieuse d’économiser l’énergie. Peu à peu, la commercialisation de diodes électroluminescentes telles que les LEDs (Light-Emitting Diodes) ou les OLEDs (Organic Light-Emitting Diodes) s’est implantée et elle connait aujourd’hui un essor considérable. Néanmoins, de nombreuses améliorations doivent encore être apportées afin d’en optimiser les propriétés. C’est dans cette thématique des matériaux électroluminescents que s’est focalisé notre travail. La préparation de nouveaux composés et l’étude de leurs propriétés photophysiques représentent en effet des étapes déterminantes et indispensables à la fabrication de ces dispositifs. <p><p>Notre travail s’est concentré plus particulièrement sur des complexes de Rh(III), Ir(III) et Ru(II) incorporant un ou plusieurs dérivés du dipyrrométhène. Le premier volet de cette thèse est consacré à la synthèse de quatre complexes mononucléaires [Rh(dipy)3], [Rh(ppy)2dipy], [Ir(ppy)2dipy], [Ru(phen)2dipy]+ dont nous avons ensuite étudié les propriétés photophysiques et électrochimiques. Des calculs théoriques TD-DFT ont également permis de conforter l’attribution de la nature des différents états excités responsables de la luminescence de ces composés. <p>Le second volet de cette thèse est consacré à la mise au point de complexes dinucléaires à l’aide d’un dérivé pontant du dipyrrométhène, avec lequel deux composés ont été obtenus :[Ir2(ppy)4µdipy] et [Rh2(ppy)4µdipy]. Une étude complète du composé d’iridium nous a permis de déterminer ses propriétés. Les nombreux problèmes de solubilité que nous avons rencontrés avec le composé de rhodium ne nous ont pas permis de mener des études approfondies de ce composé.<p>Lors d’un essai de synthèse du composé dinucléaire d’iridium, nous avons isolé le complexe mononucléaire pontant [Ir(ppy)2µdipyH]. Afin de l’engager dans la préparation d’un complexe hétérodinucléaire de type Bodipy, nous avons préalablement mis au point la synthèse d’un bodipy mononucléaire et nous avons examiné ses propriétés optiques. Nous nous sommes dès lors basé sur les conditions de synthèse de ce bodipy mononucléaire pour tenter de réaliser, sans succès, la synthèse du complexe hétéronucléaire [Ir(ppy)2µdipyBF2].<p>L’ensemble des résultats obtenus au cours de ce travail, nous ont permis de comprendre l’effet du métal de transition et celui de la dérivatisation du dipyrrométhène sur les propriétés photophysiques des complexes formés. Il serait dès lors intéressant de tirer parti de l’ensemble de ces résultats pour mettre au point un nouveau dérivé pontant du dipyrrométhène afin d’optimiser les propriétés des complexes formés, et à terme permettre la préparation de réseaux organométalliques performants et exploitables dans des dispositifs électroluminescents. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Call number: LD2668 .T4 1978 J34 / Master of Science

In an industrial application a GFAAS method for monitoring the Rh concentration in process streams is being used. Matrix effects are known to exist with the application of this technique; in fact, it was observed that different solvents lead to different results. Therefore, standard additions have to be employed for quantitative determinations, resulting in high costs and long analysis times. In an attempt to understand these interfering effects, fractional factorial designs were proposed to determine whether any GFAAS parameter was responsible for, or related to, the matrix effects. Seven GFAAS parameters were investigated: final temperature, ramp time and hold time of the transitions step (from the dry step); final temperature, ramp time and hold time of the ashing/pyrolysis step; ramp time of the atomisation step. The results showed that the matrix effects were not related to any specific parameter. A complete factorial design was implemented to demonstrate the fundamental role of the atomisation temperature. SEM analysis showed that the surface of the graphite tubes might be affected in different ways by different solvents. A Principal Component Analysis demonstrated that the matrix effects may be related to the viscosity and melting point of the solvents and may be independent of their molar mass. To identify the origins of these effects, an investigation on the link between the tube surface-sample matrix interactions and the physical properties of the matrices is recommended. Since GFAAS parameters cannot compensate for the matrix effects, standard additions remain the preferred mode of operation as it accounts for the effects in-situ. / Chemistry / M.Sc. (Chemistry)

The hydroformylation of 1-octene with supported ionic liquid phase catalyst was demonstrated when using a system involving the substrate, reacting gases and products in CO₂ and N₂ flow over a fixed bed supported ionic liquid phase catalyst (silica gel and carbon aerogels as solid support respectively) at different system pressures. Yields, reaction rates, selectivities and rhodium leaching were all monitored. A pressure of CO₂ flow just below the critical point of the flowing mixture (106 bar at 100 °C if no 1-octene has been converted) was the best condition for the hydroformylation. It gave the highest acitivity (conversion to aldehyde up to 70 %), fastest reaction (TOF up to 575.3 h⁻¹) and best stable selectivity ( l:b ratio reaching 3.37 ). The utilization of scCO₂ as reaction media leads to remarkable stability of the catalyst. The supercritical or near critical (expanded liquid) system completely overcame the progressive decrease in activity of catalyst at 50, 75 bar with liquid phase transport and also showed much better results than when using other gas flows such as N₂ flow at 100 bar. In the high pressure scCO₂ phase, the concentration of 1-octene at the catalyst bed was reduced so that the conversion to aldehyde was reduced. The pore size and surface groups of the solid support should be suitable for the SILP catalyst consisting of metal complex, excess ligand and ionic liquid. Using microporous carbon aerogels as the supports, whether activated or not, gave disappointing results.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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Submitted in fulfillment of the requirements for the award of the Degree of Master of Applied Science in Chemistry, Durban University of Technology, Durban, South Africa, 2016. / The 𝛼-aminophosphonates (APs) and dihydropyrimidinones (DHPMs) exhibit a wide range of important biological activities. The great potential of these compounds in biological applications prompted an increased interest in the development of efficient synthetic methods for their preparation. A novel rhodium supported boron nitride (RhBNT) material was synthesized by simply mixing boron nitride in a solution of rhodium acetate, under inert atmosphere for 7 days followed by filtration; the yield was 95 %. It exhibited excellent catalytic properties for the synthesis of 13 novel APs and 5 DHPMs. Characterization of RhBNT was performed by several techniques: the crystalline nature of RhBNT and nano size was confirmed by SEM spectroscopy, EDX pattern for RhBNT showed signals for rhodium metal, the Brumnauer-Emmett-Teller (BET) analysis showed the specific surface area of RhBNT to be 28.12 m2/g, pore volume 0.23cm3/g and pore size of 199.8Aº thereby suggesting RhBNT as a potentially effective catalyst for organic reactions; the mesoporous nature of the material was established by a type- IV adsorption isotherm; the DSC-TGA Profile indicates that RhBNT has good thermal stability and can be used adequately for catalysis. The DSC curve showed evidence of a broad exothermic peak. The RhBNT was subsequently used in the Kabachnik-Fields and Biginelli reaction in order to assess its catalytic potential. Herein Vilsmeier-Haack reagent was used to synthesize 4-oxo-chromene-3-carbaldehyde and 4-oxo-4H-benzo[h]chromene-3- carbaldehyde from 2-hydroxyacetophenone and 1-hydroxy-2-acetonaphthone, respectively. These two carbaldehydes were subsequently used to synthesize thirteen novels APs and five DHMPs using RhBNT as the catalyst The antimicrobial activities of the synthesized compounds were assessed against Escherichia coli, Bacillus cereus, Micrococcus luteus, Staphylococcus aureus and Candida albicans using the disc diffusion method. It was found that none of the compounds inhibited growth of bacteria or fungus. The assessment of toxicity was evaluated by using the brine shrimp lethal test. It was found that six of the novel compounds exhibited more than 50% brine shrimp death and were considered toxic against Artemia sp. and hence unsuitable as a potential drug whilst four compounds were found to be less toxic, exhibiting a brine shrimp death of less than 50%. Molecular docking studies were carried out for 13 APs to estimate their binding interactions with HIV-1 reverse transcriptase. Four APs showed good potential for the inhibition of HIV-1 reverse transcriptase. / M