L’ouverture sélective de cycles aromatiques sur catalyseurs bifonctionnels peut en principe aboutir à une augmentation de l’indice de cétane des gazoles. Dans ce travail, nous nous sommes concentrés sur l’iridium supporté sur silice-alumine amorphe (ASA) comme catalyseur d’hydroconversion de la tétraline en présence de H2S à 250-350 °C dans un microréacteur continu sous pression (4 MPa). Une étude détaillée par analyse thermique et diffraction X in situ du processus de décomposition du précurseur acétylacétonate d’iridium a permis d’optimiser l’étape d’activation. Unesimple réduction sous H2 à 350 °C aboutit à des nanoparticules Ir finement dispersées (taille 1.4 ± 0.2nm). Le catalyseur Ir/ASA est stable et résiste à l’empoisonnement par le soufre, contrairement à Ir/SiO2 et Ir/Al2O3. Les principaux produits d’hydroconversion de la tétraline sont les produits d’hydrogénation (décalines) et les produits d’ouverture et de contraction de cycle (POCC). L’analyse par chromatographie en phase gazeuse bidimensionnelle (GC��GC-MS) montre que les POCC se répartissent en produits d’ouverture saturés et aromatiques, minoritaires, et en produits de contraction saturés et aromatiques, majoritaires. Les performances catalytiques de Ir/ASA ont pu être modifiéesvia des effets de support, d’alliage et de taille. Pour une composition Si:Al d’environ 0,5, l’acidité de Brönsted du support est maximale, ce qui conduit à une activité totale et une sélectivité en POCC maximales. D’autre part, l’activité augmente par ajout de palladium, et la sélectivité en POCC est maximale pour la composition Ir-Pd intermédiaire. Les analyses par TEM-EDX montrent que la teneur en Pd des nanoparticules augmente avec leur taille. Enfin, la sélectivité en POCC croîtconsidérablement avec la taille des particules, qui a été ajustée entre 2 et 8 nm par frittage thermiqueen atmosphère humide. Cela s’explique par une diminution du rapport entre les quantités de sitesmétalliques et de sites acides de Brönsted dans le cadre d’un mécanisme bifonctionnel. / Selective ring opening of aromatics over bifunctional catalysts is expected to increase gas oil cetane number. In this work, we have focused on iridium supported on amorphous silicaalumina (ASA) for catalytic hydroconversion of tetralin in the presence of H2S at 250-350 °C, using a continuous high-pressure (4 MPa) microreactor. A detailed study of the decomposition of the Ir acetylacetonate precursor by thermal analysis and in situ X-ray diffraction has allowed us to optimize the activation treatment. A simple reduction in H2 at 350 °C leads to well-dispersed nanoparticles (size 1.4 ± 0.2 nm). Unlike Ir/SiO2 and Ir/Al2O3 catalysts, Ir/ASA is stable and resists to poisoning by sulphur. The main tetralin hydroconversion products are hydrogenation products (decalins) and ringopening/contraction products (ROCP). Advanced analysis by tow-dimensional gas chromatography(GC��GC-MS) shows that ROCP are composed mostly of saturated and aromatic ring-contractionproducts, and to a lower extent of saturated and aromatic ring-opening products. The catalyticperformances of Ir/ASA could be modified through support, alloy and size effects. For a Si:Alcomposition of ca. 0.5, the Brönsted acidity of the support is maximal, which leads to the highest totalactivity and ROCP selectivity. Besides, the activity increases with palladium addition, and the ROCPselectivity is maximum at intermediate Ir-Pd composition. TEM-EDX analyses show that the Pdcontent of nanoparticles increases with their size. Finally, the ROCP selectivity increases dramaticallywith particle size, which was tuned in the 2-8 nm range by thermal sintering in a wet atmosphere. Thisis explained by a decrease of the amount of metallic sites with respect to Brönsted acid sites within abifunctional mechanism.

This thesis explores the design, synthesis and characterisation of iridium(III) complexes for optoelectronic applications; in particular, cationic [Ir(CˆN)₂(NˆN)]⁺-type emitters (where CˆN is an anionic bidentate cyclometalating ligand such as 2-phenylpyridinato, ppy, and NˆN is a neutral bidentate ligand such as 2,2'-bipyridine, bpy) for use in light-emitting electrochemical cells (LEECs). Design strategies aim to achieve high photoluminescence quantum yields (Φ[sub](PL)) for these complexes. Chapter 1 provides an overview of the fundamental photophysics of luminescent transition metal complexes, before reviewing state of the art iridium complexes employed in LEEC devices. Chapter 2 employs a combination of the electron-deficient 2,4-difluorophenylpyridine (dFppy) CˆN ligand and various functionalised biimidazole (biim) NˆN ligands. Within the family of different biim ligands the emission energy does not vary significantly, but the excited state kinetics di.er depending on the rigidity of the biim ligand. Combining the lead biim ligand with a sterically bulkier CˆN ligand gives an iridium complex that emits deep blue light with 90% Φ[sub](PL) in MeCN. Chapter 3 describes an approach to replacing the electrochemically unstable aryl carbon-fluorine bonds in dFppy, while maintaining the deep blue emission colour observed for the complexes in Chapter 2. Chapter 4 expands on the concept of rigid biim ligands to bibenzimidazoles (bibenz). Combining conjugated bibenz NˆN ligands with more conjugated CˆN ligands allows for the emission colour of these complexes to be tuned to the orange/red. The Φ[sub](PL) necessarily falls due to the energy gap law, but is nevertheless higher than values measured for reference complexes. Chapter 5 explores the use of an arylazoimidazole ligand with donor-acceptor intraligand charge transfer characteristics in order to red-shift the emission further. The resultant complex is poorly emissive, but shows a panchromic absorption profile and high molar absorptivity, which is unusual for iridium(III) complexes. The absorption profile can be tuned as a function of the protonation state of the imidazole.

Conducting metallopolymers have been investigated for a variety of applications due to their ability to take advantage of both the mechanical processability of the polymer material, as well as the optical and electronic properties of the metal. Our project goal is to design, synthesize and characterize novel iridium(III)-containing conducting metallopolymers for use as the active layer in polymer light-emitting diodes. We have utilized thiophene functionalized ligands that can be readily electropolymerized into conducting polymer thin films and can be easily incorporated into a device structure. Iridium(III) was chosen as the metal center due to its promising photophysical properties, as similar complexes have demonstrated high luminescent quantum yields and short phosphorescent lifetimes. The coordination environment around the metal can be altered synthetically to tune the emission wavelength across the visible spectrum. The synthetic control over the polymer backbone, as well as the iridium(III) ligand environment, allowed us to independently vary each component, which has provided a variety of materials. The materials are characterized through 1H and 13C NMR, mass spectrometry, elemental analysis, electrochemistry, X-Ray diffraction and X-Ray Photoelectron Spectroscopy. The photophysical properties of the materials are studied through UVvii Visible absorption spectroscopy, UV-Vis-NIR spectroelectrochemistry and steadystate/ time-resolved emission spectroscopy. / text

Face à la nécessité d’une réduction drastique des émissions de gaz à effet de serre, le déploiement des piles à combustibles est présenté comme une solution d’avenir. La production d’hydrogène décarbonée est un des enjeux futurs pour permettre une transition énergétique efficace. Dans cette optique, l’électrolyseur à membrane échangeuse de proton (PEMWE), combiné aux sources énergétiques renouvelables, est une technologie intéressante. De nombreux défis sont encore à relever pour permettre une commercialisation de cette technologie, en particulier côté anodique. L’oxyde d’iridium, matériau coûteux et très rare, est utilisé à l’anode pour sa capacité à catalyser le dégagement d’oxygène tout en résistant aux conditions acide et oxydante. Il subit néanmoins des dégradations au cours de son utilisation.Dans ce travail, différentes surfaces modèles d’iridium pour le dégagement d’oxygène ont été étudiées pour comprendre les mécanismes mis en jeu lors des premières étapes d’oxydation de la surface et du dégagement d’oxygène. Après caractérisations par spectroscopie d’impédance électrochimique dynamique (DEIS), technique innovante permettant d’analyser les systèmes dynamiques, les relations structure-activité-stabilité lors du dégagement d’oxygène ont été étudiées en comparant des surfaces modèles d’iridium ((111), (210) et (210) nanostructurée). Les résultats obtenus mettent en évidence qu’après quelques heures à haut potentiel (> 1,6 V vs. Electrode Réversible à Hydrogène), ces surfaces, de structures et compositions chimiques initiales différentes, tendent vers le même état. Enfin, l’étude de films minces d’iridium et de nickel@iridium, modélisant des particules cœur@coquille, a montré qu’après dissolution du nickel initialement présent, une couche poreuse active pour le dégagement d’oxygène est formée. Ces résultats sont prometteurs pour la synthèse de catalyseurs à base d’iridium pour le dégagement de dioxygène. / With the need for a drastic reduction of greenhouse gases, the deployment of fuel cells is one of the considered solutions. Decarbonated hydrogen production is subsequently a major challenge to enable an efficient energetic transition. From this perspective, Proton Exchange Membrane Water Electrolyser (PEMWE) is a technology of interest, especially if coupled with renewable energy sources. Key challenges are still to be addressed before commercializing this technology, in particular at the anode. Iridium oxide, a costly and rare material, is implemented in anodic catalytic layers to catalyse the Oxygen Evolution Reaction (OER) while being resistant to harsh acidic and oxidative conditions. It nonetheless undergoes some degradations.In this work, different iridium model surfaces for the OER where studied to understand mechanisms involved during the first oxidations step and oxygen evolution. After characterisations by Dynamic Electrochemical Impedance Spectroscopy (DEIS), an innovative technique used to study dynamic systems, structure-activity-stability relationships towards the OER were studied by comparing iridium model surfaces ((111), (210) and nanostructured (210)). Results showed that after few hours at high potential (> 1.6 V vs. Reversible Hydrogen Electrode)), these surfaces, with different initial chemical compositions and structures, tend to the same state. Finally, iridium and nickel@iridium thin films were studied, to model core@shell particles. Results indicate that the nickel dissolution lead to the formation of a porous layer more active towards the OER. These findings could help to design active iridium catalysts for the OER.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / Reliable System Services Corporation (RSS Corp.) presents the feasibility of a low cost, low power, high capacity, robust RF Communications Network using SATCOM and UAV relays. The developed architecture will be suitable for OTH Large Area Test and Training exercises as well as applications for OTH Digital Battlefield scenarios. A specific application is shown for the planned Littoral Combat Ship (LCS) missions, although the developed architecture will have broader applications for any surface combatant requiring an Over-the-Horizon (OTH) data link to distributed players and sensors. A conceptual design for the IP network radio system will implement RSS Corp. developed secure IRIDIUM global full duplex data links and Harris Corp. developed long range high bandwidth 802.11 full duplex data links. The results will be significant, and the developed system could be a cornerstone of the future digital battlefield combat communications architecture. The developed technology will also have significant use in any application for Test, Evaluation and Training Ranges requiring net centric, command/control and wide bandwidth TLM data collection from distributed remote players and sensors.

Les ligands bis(hémicages) représentent un motif structurel non exploité qui ont attiré notre attention. Ces ligands peuvent complexer jusqu'à deux analytes en même temps. Ceci permet d'obtenir une lecture luminescente en trois volets : une première étant le ligand sans analyte, puis deux signaux distincts pour le ligand + 1 analyte et le ligand + 2 analytes. Dans notre étude, nous avons inclus un [3.3.3](1,3,5)cyclophane comme architecture de base pour les bis(hémicages). Des calculs ont démontré que dans ces bis(hémicages)-cyclophane, le noyau cyclophane est directement impliqué dans le système électronique du ligand. La synthèse du noyau [3.3.3](1,3,5)cyclophane pose un grand défi de synthèse puisque peu d'exemples sont rapportés. Afin de moduler les défis, une étude modèle comportant la préparation d'une seule hémicage sera développée. Ces hémicages modèles seront utilisés afin d'optimiser la synthèse et seront des composés de référence importants pour les études électroniques et photophysiques.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper investigates the feasibility of using commercial satellite constellations to relay telemetry data from flight test vehicles as part of a Global Test Range. The use of a commercial satellite constellation would provide an augmented capability to the test range, providing near real-time data to the data reduction site and test range control at reasonable cost. This includes an analysis of current and proposed commercial communication satellite constellations to determine if any of them would fulfill the needs of a telemetry test range. Preliminary assessment of the communication link between a flight vehicle and the satellite constellations is performed.

No description available.

Paraffin activation has practical implications in the replacement of current petrochemical feedstocks (olefins), by utilizing economical and easily accessible alkanes, which may result in more efficient strategies for fine chemical synthesis and the proficient use of energy. However, the chemical inertness of paraffins limits their conversion to more valuable products. Several pincer chelate complexes are utilized in stoichiometric and catalytic C–H activation. These pincer ligands have attained much interest in that they are part of a system, which displays high stability, activity and variability. In this study four aminodiphosphine (PNP) pincer ligands were successfully synthesized and characterized by NMR, IR and HRMS. To investigate the steric effects on the metal center, four different functional groups on the nitrogen atom were used, a cyclic ring (cyclohexyl (3.1)) branched chain (iso-propyl (3.2)); straight chain (pentyl (3.3)); and aromatic ring (benzyl (3.4)). The ligands were successfully complexed to the transition metals iridium and cobalt and characterized by elemental analyses, IR, HRMS and thermogravimetric measurements. The thermal behaviour of the ligands showed that ligands 3.1-3.3 displayed similar decomposition patterns. Similar fragmentation patterns were observed for the iridium and cobalt complexes containing ligands 3.1 and 3.3. The complexes were tested in the oxidation of n-octane in two solvent systems, DCM and MeCN with H2O2 and t-BuOOH as the oxidants. The optimum substrate to oxidant ratio was found to be 1:5. No conversion was observed with H2O2. The conversion in DCM for the iridium catalysts was much higher than that of the cobalt catalyst. However, higher conversion was obtained in MeCN for the cobalt catalysts. No conversion was observed for the iridium catalyst in MeCN. The selectivity to ketones was much higher than to the alcohols, with only the C(1) position being most selective to the alcohols. The in situ, single pot testing of n-octane using a ruthenium precursor and ligand 3.1- 3.4 undertaken in DCM showed no conversion, whilst in MeCN a conversion of 17% was observed. The selectivity was similar to that obtained by the cobalt catalysts in MeCN. All testing showed that the catalyst containing ligand 3.1 was the most active giving the highest conversions in different solvent systems, which is attributed to the bite angle effect. / Thesis (M. Sc.)-University of KwaZulu-Natal, Durban, 2011.

The aim of this thesis was to investigate the physical and electrochemical properties of sub monolayer and monolayer of copper deposition on the polycrystalline iridium, ruthenium and its conductive oxide. The electrochemical methods cyclic voltammetry (CV) and chronocoulometry were used to study the under potential deposition. The electrochemical methods to oxidize the ruthenium metal are presented, and the electrochemical properties of the oxide ruthenium are studied. The full range of CV is presented in this thesis, and the distances between the stripping bulk peak and stripping UPD peak in various concentration of CuSO4 on iridium, ruthenium and its conductive oxide are shown, which yields thermodynamic data on relative difference of bonding strength between Cu-Ru/Ir atoms and Cu-Cu atoms. The monolayer of UPD on ruthenium is about 0.5mL, and on oxidized ruthenium is around 0.9mL to 1.0mL. The conductive oxide ruthenium presents the similar properties of ruthenium metal. The pH effect of stripping bulk peak and stripping UPD peak of copper deposition on ruthenium and oxide ruthenium was investigated. The stripping UPD peak and stripping bulk peak disappeared after the pH ≥ 3 on oxidized ruthenium electrode, and a new peak appeared, which means the condition of pH is very important. The results show that the Cl- , SO42- , Br- will affect the position of stripping bulk peak and stripping UPD peak: the stripping bulk peak will shift and decrease if the concentration of halide ions is increasing, and the monolayer of UPD will increase at the same time.