Methane is an abundant resource existing in the form of natural and shale gas, and molybdenum-based catalysts, including molybdenum oxides and carbides, are the commonly used components in catalysts for converting methane to value-added chemicals. Therefore, understanding the catalytic mechanism underlying the methane conversion over molybdenum-based catalysts is key to designing highly efficient catalysts and optimizing the operating conditions. In this dissertation, I focus on the structural evolution from oxide to carbides and catalytic reactivity of the molybdenum-based catalysts for methane conversion based on the result from density functional theory (DFT) computational studies.First, the surface chemistry and reactivity of α-MoO3 toward C-H bond activation of methane by breaking the first C-H bond on the MoO3 (010) surface were used to evaluate various functionals of the DFT method. Our results indicate that surface reduction of α-MoO3 (010) occurs preferably through releasing the terminal oxygen atoms, generating oxygen vacancies while exposing the reduced Mo centers. These oxygen vacancies tend to be separated from each other at a higher density due to the repulsive interactions. Furthermore, the reduced α-MoO3 (010) surface promotes methane activation kinetically and thermodynamically by reducing the activation barrier for the first C-H bond breaking and stabilizing the product state as compared with those on the stoichiometric surface. There is a synergy between the reduced Mo active site and surface lattice oxygen for C-H bond cleavage. In addition, the performance of different functionals, including the pure-GGA PBE functional with the semi-empirical vdW correction and the meta-GGA SCAN functional, has been investigated. With the meta-GGA functional, we can predict the bulk structure of α-MoO3 more accurately while reproducing the thermal chemistry of MoO3. On the other hand, the reactivity based on the PBE functional is qualitatively consistent with that from the SCAN functional.We then conducted a systematic study of methane activation and conversion over the Mo-terminated surfaces derived from different phases of Mo2C carbides, i.e. the (001) surface of α-Mo2C and the (100) surface of β-Mo2C. The results show that Mo-terminated Mo2C with lower carburization in its subsurface (β-Mo2C) possesses a superior reactivity toward methane activation, resulting in a complete dissociation of methane to carbon adatom on the surface. This carbon adatom causes further carburization of the surface, lowering the reactivity toward methane activation. Moreover, the carburization occurs more easily in the near surface layers of Mo2C than in the bulk. Although carburization lowers the activities for methane activation, it promotes C-C coupling for dimerization of the (CH)ad species, resulting in (C2H2)ad on the Mo-terminated surfaces. On the deep carburized molybdenum carbide (MoC) surfaces, we mapped out the elementary steps of CH4 dissociation and possible mechanisms for forming the C2 species. The results indicate that the Mo-terminated MoC surfaces derived from different bulk phases (α- and δ-) of MoC possess a similar mechanism to that on the noble-metal surfaces for methane dissociation, i.e., CH4 dissociates sequentially to (CH)ad with both kinetic and thermodynamic feasibilities while breaking the last C-H bond in (CH)ad is highly activated. As such, C-C coupling through dimerization of the (CH)ad species occurs more readily, resulting in (C2H2)ad on the Mo-terminated surfaces. Such (C2H2)ad species can dehydrogenate easily to other C2 adsorbates such as (C2H)ad and (C2)ad. Consequently, these C2 species from CH4 dissociation will likely be the precursors for producing long chain hydrocarbons and/or aromatics on molybdenum carbide based catalysts.

The application of N-heterocyclic carbenes (NHCs) in organic and organometallic chemistry has been well-established. The utilization of Zr(NMe2)4 for transmetallation has facilitated the synthesis of CCC-NHC pincer transition metal complexes since 2005 by our group, including Fe, Co, Rh, Ir, Ni, and Pt. However, there have been no reports on the synthesis, characterization, and application of CCC-NHC pincer complexes involving Re and Mn to date. This dissertation aims to address this gap by discussing the synthesis and catalytic activities of CCC-NHC pincer Re and Mn complexes in crossed-coupling reactions. Chapter II will focus on the synthesis of the CCC-NHC pincer Re complex. The synthesis involved transmetallation with CCC-NHC pincer Zr complex using Re(CO)5Cl. The Re complex was characterized by 1H and 13C NMR spectroscopy, mass spectroscopy and its structure was determined by X-ray crystallographic methods. Catalytic activities of Re complex were demonstrated through borrowing hydrogen reactions for the crossed-coupling between ketones and primary alcohols, yielding α-alkylated ketones with water as the only by-product. The borrowing hydrogen reaction improved the economic efficiency when it did not require the good leaving group that conversed from primary alcohols. A wide range of substrates yielded yields ranging from 53% to 92%. Chapter III willdiscuss the expanded application of the Re complex, including borrowing hydrogen reactions for coupling between primary and secondary alcohols, as well as one-pot synthesis of quinolines via dehydrogenative/oxidative cyclization reactions. Control experiments support the proposed catalytic cycle of borrowing hydrogen reactions by the Re complex. In Chapter IV, the synthesis and catalytic activities of CCC-NHC pincer Mn complex are examined. The proposed structure of the Mn complex was supported by NMR spectroscopy, mass spectroscopy, and single X-ray diffraction. The Mn complex demonstrates catalytic activities through borrowing hydrogen and dehydrogenative cyclization, yielding α-alkylated ketones, 2-oxindole derivatives, and quinolines. The control experiments were set up and the proposed mechanism of Mn complex for borrowing hydrogen reaction were consistent with Re complex.

No description available.

Abstract The dihydropyridine receptor (DHPR) in the skeletal muscle plasma membrane functions as a voltage sensor for excitation-contraction coupling. In the present work the expression and special features of DHPR were studied under various conditions. In order to localize and visualize the DHPRs, a method using fluorophore-conjugated dihydropyridine molecules as a probe was developed. In addition, different laboratory assays and electrophysiological measurements were used to study the expression of the myofibrillar proteins, force production of the muscle and conduction velocity of the plasma membrane. During the postnatal development of mouse skeletal muscle the density of DHPR increased. By the time of DHPR appearance, the expression of sodium channels had started and the typical assembly of basic structural components and membrane compartments was clearly detectable. According to the histochemical analysis, the DHPR was selectively expressed in type IIA muscle fibres of mouse. In addition to the fibre type specificity, the uneven distribution of DHPRs was also seen at the muscle level. The attenuation of the contraction force after addition of DHPR blocker was largest in muscles with a high percentage of type IIA fibres. In fish muscles, the distribution of DHPR was homogenous and the density between different fibre types was quite similar. In gastrocnemius muscle of mouse, the density and mRNA expression of DHPR increased significantly by 21.5 and 66.8%, respectively, after a 15-week aerobic exercise programme. The increase correlated significantly with the raise in % myosin heavy chain IIa isoform. In thigh and heart muscles, no significant changes were observed. In fish, the environmental change following hatchery release and downstream migration of 46.5 km induced an increase in the DHPR density in swimming muscles. Furthermore, a transition of phenotypic profile from fast-to-slow fibres was observed. Taken together, the present data provide evidence for the fact that the expression of DHPR increases during postnatal development. Moreover, the expression correlates with a specific fibre-type metabolism, thus having an impact on the overall contractile properties of the muscle. This is further manifested as an increase in the DHPR density after endurance training in mammalian as well as in fish muscle. In addition, a strong correlation exists between the level of muscle activity and the density of DHPR. / Tiivistelmä Poikkijuovaisen lihaksen solukalvolla esiintyvä dihydropyridiini (DHP) reseptori toimii jännitesensorina lihaksen ärsytys-supistus kytkennässä. Tässä työssä tutkittiin DHP reseptorin erityispiirteitä sekä erilaisten fysiologisten tekijöiden vaikutusta reseptorin ilmenemiseen. DHP reseptorien visualisointiin kehitettiin histologinen värjäysmenetelmä, jossa merkkiaineena toimi fluorofori-konjugoitu DHP molekyyli. Lisäksi työssä tutkittiin lihaksen proteiinien ekspressiota, lihaksen voimantuottoa sekä solukalvon johtonopeutta erilaisten määritysmenetelmien ja elektrofysiologisten mittausmenetelmien avulla. Tulokset osoittivat, että yksilönkehityksen aikana DHP reseptorien tiheys kasvoi hiiren poikkijuovaisessa lihaksessa. DHP reseptorien ekspression alkaessa natriumkanavat olivat jo ilmaantuneet solukalvolle ja lihassolun rakenne oli pitkälle erilaistunut. Histokemiallisten määritysten perusteella DHP reseptorin ekspressio oli selektiivistä. Reseptoreita esiintyi runsaimmin tyypin IIA soluissa. Reseptoriproteiinin solutyyppispesifisyys oli huomattavissa myös lihastasolla. Tulosten mukaan proteiinin salpaaja alensi lihaksen supistumisvoimaa erityisesti niissä hiiren lihaksissa, joiden solutyyppikoostumuksessa tyypillä IIA on suuri prosentuaalinen osuus. Kalan lihaksissa DHP reseptorit olivat homogeenisesti jakautuneet. Lisäksi reseptoritiheys oli samankaltainen eri solutyyppien välillä. 15 viikon aerobinen harjoittelu lisäsi sekä DHP reseptorin proteiini- että mRNA- ekspressiota tilastollisesti merkitsevästi (21,5 ja 66,8 %) hiiren kantalihaksessa. Ekspression kasvu korreloi merkitsevästi samanaikaisesti tapahtuneen myosiini isomuoto IIa määrän kasvun kanssa. Reisi- ja sydänlihaksessa merkittäviä muutoksia ei havaittu. Kalan uintilihaksissa DHP reseptorien tiheys kasvoi vapauttamisen jälkeisen ympäristön muutoksen ja 46,5 km pituisen vaelluksen jälkeen. Lisäksi lihasten solutyyppikoostumuksessa tapahtui muutos kohti hitaasti supistuvia solutyyppejä. Yhteenvetona voidaan todeta, että saatujen tulosten perusteella DHP reseptorien ekspressio kasvaa syntymän jälkeen hiiren poikkijuovaisessa lihaksessa. Solujen erilaistuessa ekspressio korreloi solutyyppimetabolian kanssa vaikuttaen edelleen lihaksen supistumisominaisuuksiin. Tästä johtuen myös kestävyysharjoittelun seurauksena DHP reseptorien määrä kasvaa sekä nisäkkään että kalan lihaksissa. Erityisesti lihaksen aktiivisuudella on merkitystä DHP reseptorin ekspressioon.

Title: Palladium catalysts deposited over novel siliceous supports Author: Pavlína Křečková Department: Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague Supervisor: prof. RNDr. Petr Štěpnička, Ph.D. Supervisor's e-mail address: stepnic@natur.cuni.cz Advisor: prof. Ing. Jiří Čejka, DrSc. Advisor's e-mail address: jiri.cejka@jh-inst.cas.cz Abstract Keywords: palladium; deposited catalysts; siliceous supports; C-C coupling reaction. The aim of this work was to prepare a deposited palladium catalyst from Pd2+ and twodimensional zeolite ITQ-2 bearing ≡SiCH2CH2CH2NHCH2CH2NEt2 groups at the surface. This catalys has been evaluated in the Heck reaction between n-butyl-acrylate and brombenzene to give n-butyl-cinnamate. Influence of the reaction temperature, the solvent, base and hydrate water on the progress of the Heck reaction was investigated. This work also deals with the possibility of recycling the catalyst and, due to its nature, with the quantity of leached palladium into the reaction mixture. Furthermore, the work describes differences in morphology between the fresh and a recycled catalyst.

Les catalyseurs supportés sur des dendrimères et nanoparticules magnétiques acquièrent actuellement une importance accrue dans le contexte de la chimie verte et du développement durable car ils sont séparés facilement des produits de réaction par filtration ou à l’aide d’un aimant et recyclables. Dans cet esprit, la thèse a été dédiée à la synthèse, à la caractérisation et aux applications catalytiques de catalyseurs moléculaires, nano-et dendritiques immobilisés impliquant le ruthénium, le cuivre et le palladium. Les catalyseurs magnétiquement recyclables de ruthenium (II), de cuivre (I) et des nanoparticules de palladium ont produit d’excellentes performances en terme d’activité, de stabilité et de recyclabilité pour les réactions de cycloaddition entre les alcynes et les azotures et les réactions de couplage croisé carbone-carbone. Enfin, la synthèse de complexes mono-et polymétalliques du palladium contenant les ligands 2-pyridyl-1,2,3-triazole a également été réalisée et leurs proprietiés catalytiques ont été étudiées. / Catalysts based on dendrimers and magnetic nanoparticles are becoming increasing utilized in the context of green and sustainable chemistry, because they are easily separated by precipitation or by using asimple magnet respectively, and they are recyclable. In this spirit, the thesis has been devoted to the synthesis, characterization and catalytic applications of iron oxide magnetic nanoparticles-immobilized molecular, nano-and dendritic catalysts involving Ru, Cu and Pd. Magnetically recyclable ruthenium(II) and Cu(I) complexes and Pd nanoparticles have provided excellent catalytic performances in terms of activity, stability and recyclability, using alkyne-azide cycloaddition and carbon-carbon cross coupling reactions. The synthesis of mono-and polymetallic palladium complexes containing the 2-pyridyl-1,2,3-triazole ligand or nonabranch-derived ligands has also been carried out, and their catalytic properties in coupling reactions has been studied

Abstract Cytosolic Ca2+, [Ca2+]I , has a key role in intracellular signalling during excitation-contraction coupling (E-C coupling) in cardiac myocytes. The sarcoplasmic reticulum (SR) is a main intracellular Ca2+ store and the Na+-Ca2+ exchanger (NaCaX) is a major mechanism to extrude Ca2+ for balancing the Ca2+ influx via L-type Ca2+ channels during excitation. Furthermore, [Ca2+]I also affects the configuration of the action potential (AP). The present study, by combination of animal experiments and computer simulations, investigated the roles of [Ca2+]I, SR and NaCaX in cardiac myocytes, in Ca2+-induced Ca2+ release (CICR) and in modulation of APs. The following were studied: (I) the stretch-induced effects on rat atrium and the role of [Ca2+]I in modulation of AP; (II) the role of the SR in modulation in rat atrium by stretch; (III) the role of NaCaX; (IV) the role of [Ca2+]I in modulation of action potential duration (APD) in myocytes with short and long action potential duration. In isolated rat atrial preparations, the physiological or moderate stretch stimulus caused two- phasic rise of developed contraction, rapid and slow phases, accompanied with slow increments of [Ca2+]I and prolongations of action potentials durations in continuous recordings. In sustained stretch, the APD and [Ca2+]I were all increased significantly when intra-atrial pressure increased from 1 to 3 mmHg. In computer simulations, employing a rat atrial model (RA model), it was found that stretch-activated channels and increased Tn C affinity for Ca2+ alone could not produce the changes in the experiments. Only after both mechanisms applied to model cells, the main experimental findings could be mimicked (I). The prolongation of APD induced by stretch in rat atrial preparations was reversed after depleting the Ca2+ content of the SR by application of the SR functional inhibitors, ryanodine, thapsigargin and caffeine (II). In the computer simulation using modified guinea pig ventricular model, the Ca2+ entry via the reversal of NaCaX was found to be accounting 25% of the total activator Ca2+ for triggering Ca2+ release from the SR during normal excitation. This contribution increases with elevated [Na+]i (III). In a guinea pig ventricular model (GPV model) and a RA model were employed for investigating the regulation of APD by [Ca2+]I-dependent membrane currents. Increased SR Ca2+ content produced an elevated [Ca2+]I in both model cells, leading to prolongation of APD in the RA model but shortening in the GPV model. Increased [Ca2+]I enhances the NaCaX current in the same scale in both models, but inhibits L-type Ca current much more in the GPV model than the RA model (IV). In conclusion, (I) Stretch-induced [Ca2+]I increase prolongs the rat atrial AP by enhancing the NaCaX inward current. Stretch-activated channels (SACs) and increased affinity of TnC for Ca2+ are main general factors responsible for the variety of changes of cardiac muscles induced by stretch. (II) The SR plays a crucial role in the modulation of myocytes by accumulating the additional Ca2+ influx via sarcolemma during stretch. (III) The NaCaX contributes a small part for activator Ca2+ for calcium release from the SR during normal cardiac E-C coupling. However, this contribution is [Na]i-dependent, and in some pathological conditions, it may be a potential factor for cardiac arrhythmogenesis. (IV) Different effects on the NaCaX and L-type channels induced by increased [Ca2+]I leads to the dispersion of the change of APD in myocytes with long and short AP during inotropic interventions that increase the [Ca2+]I.

La première partie de ce manuscrit traite de la synthèse de phosphine-boranes P-stéréogènes énantioenrichis à partir d’un précurseur développé par notre laboratoire : le H-phénylphosphinate d’adamantyle. Grâce au développement d’une séquence monotope, une variété d’oxydes de phosphine P-stéréogènes de haute pureté optique a pu être synthétisée. Ces composés comportant une attache hydroxyle ont ensuite été réduits de façon stéréospécifique en présence de borane pour générer les précurseurs phosphine-boranes correspondants. Lors de cette étape de réduction, l’importance de la fonction hydroxyle a été mise en évidence, et un mécanisme basé sur la formation d’une espèce phosphaboracyclique intermédiaire a été proposé, sur la base de l’isolement d’intermédiaires réactionnels O-borés. Les trois rôles du borane (activation, réduction, protection de la phosphine) ont été clairement identifiés dans ce processus. Dans un second temps, nous avons pu mettre à profit la rétroaddition du groupement hydroxyalkyle en milieu basique lors de l’alkylation stéréospécifique chimiodivergente de phosphure-boranes masqués. Cette rétroaddition a permis de contourner l’instabilité chimique et configurationnelle des phosphures générés in situ, permettant l’accès à des phosphine-boranes fonctionnalisés de manière énantiospécifique. Ces ligands P,N ont été ensuite complexés au palladium et les complexes ont pu être testés comme catalyseurs de couplages C-C énantiosélectifs. Lors de ces couplages, l’angle de morsure du ligand s’est révélé crucial pour la réactivité du système catalytique. / The first part of this manuscript deals with the synthesis of enantioenriched P-stereogenic phosphine-boranes from a chiral precursor developed in our laboratory: H-adamantyl phenylphosphinate. Through the design of a one-pot procedure, the synthesis of a wide array of highly enantioenriched phosphine oxides has been achieved. These hydroxy-functionalised compounds were reduced stereospecifically under borane conditions to yield the corresponding hydroxyalkylphosphine-boranes. During the study of this reaction, the importance of hydroxy group has been highlighted, and a mechanism relying on the formation of transient phosphaboracyclic intermediate could be proposed, on the basis of kinetic observation and isolation of O-borylated intermediates. In this transformation, borane seems to display three roles: activating, reducing and protecting agent. Next, we were able to take advantage of the retroaddition of hydroxyalkyl moiety under basic conditions to develop a new approach for the stereospecific and chemodivergent alkylation of masked secondary phosphine-boranes. This unusual reactivity allowed us to circumvent the relative chemical and configurational instability of such in situ generated phosphido-boranes intermediate, thus enabling the stereospecific synthesis of functionalised tertiary phosphine-boranes. These P-N ligands have been complexed to palladium, and the catalytic activity of these complexes in enantioselective C-C couplings has been studied. During the catalytic process, it appears that the ligand bite angle plays an important role in the catalyst activity.

No description available.

No description available.