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Activity of new nickel-complexes in coupling reactions
Plaček, Martin ; Svoboda, Jan (advisor) ; Hoškovec, Michal (referee)
In this work, we report the study of the catalytic activity of newly prepared coordination compounds of nickel(II) (complexes were prepared by prof. Kyritsis, University of Athens). The activities in model reactions of Kumada and Suzuki coupling and polymerization of 2,5- dibromo-3-hexylthiophene were tested. For Kumada coupling, the activity is comparable with known complex [Ni(dppp)Cl2]. On the other hand, selected complexes exhibit only limited activity for Suzuki coupling. GRIM polymerization of 2,5-dibromo-3-hexylthiophene was successful. Properties of prepared polymers are comparable with polymers prepared via known route with [Ni(dppp)Cl2].
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Synthesis and application of new bipyridine ligands
Bednářová, Eva ; Kotora, Martin (advisor) ; Cibulka, Radek (referee) ; Michelet, Véronique (referee)
2,2'-Bipyridines and their appropriate N,N'-dioxides form a significant class of heteroaromatic compounds, which has found application in various fields of chemistry and predominantly in asymmetric catalysis. One of the most powerful methods for their synthesis is cocyclotrimerization of alkynes with nitriles. A new variant of cyclotrimerization reaction - cocyclotrimerization of halodiynes with nitriles, which results in the formation of 2- and 3-halopyridines, has been developed. The reaction was studied on a wide range of substrates providing the pyridine products in good isolated yields. Formation of an unexpected product of halogen exchange reaction was observed during the course of the study and its origin was elucidated by experimental studies. The prepared 2-halopyridines were used as starting materials for syntheses of new chiral 2,2'-bipyridine ligands. The crucial step of their synthesis turned out to be the reductive dimerization of 2-halopyridines to the corresponding 2,2'-bipyridines. Application of the formed bipyridine ligands was then tested in various metal-catalyzed asymmetric reactions, namely Mukaiyama aldol reaction, hydroxymethylation, conjugate addition, C-H activation of indole and desymmetrization of meso-epoxides, in which one of the bipyridine ligands showed...
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Catalytic synthesis of polyanilines
Bláha, Michal ; Vohlídal, Jiří (advisor) ; Omastová, Mária (referee) ; Trchová, Miroslava (referee)
This Ph.D. thesis is dealing with catalytic polymerization of aniline (ANI) and partially also of substituted anilines with FeCl3/H2O2 catalyst system, in which according to obtained results both active species, Fe3+ and HO , participate in the overall polymerization mechanism, creating a synergic system. The Fe3+ /H2O2 catalyst system, also called Fenton's system can considerably lower contamination of forming neat polyanilines (PANIs) by side-products characteristic of stoichiometric polymerization. However, catalytically prepared PANIs exhibit reduced conductivity related most probably to side reactions involving radicals generated as integral components of the FeCl3/H2O2 system. Catalytic polymerization of ANI with FeCl3/H2O2 system was found to be the reaction of approx. 2nd order with respect to ANI and gives PANIs of a good quality only when [H2O2] in the reaction mixture was kept low, i.e., at under- stoichiometric ratios [H2O2]/[ANI]. At over-stoichiometric ratio [H2O2]/[ANI], PANIs of lowered conductivity, worse spectroscopic characteristics and increased size of PANI nanostructures were obtained; nevertheless, these PANIs were not over-oxidized to pernigraniline state. The reaction-time profiles of the open-circuit potential of reaction mixtures exhibited an inflection related to the...
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Homogeneous and heterogeneous titanium complexes and their use for selective ethylene trimerization to 1-hexene
Hodík, Tomáš ; Pinkas, Jiří (advisor) ; Merna, Jan (referee)
This diploma thesis is focused on the design and synthesis of new half-sandwich titanium complexes for anchoring to selected supports (SiO2, SBA-15) and the study of their catalytic activity and selectivity in ethylene trimerization to 1-hexene. The synthetic strategy of half-sandwich titanium complexes with a suitable leaving group for direct anchoring through Ti−O bond was carried out (Cl, Oi-Pr). In addition, the titanium complexes with pendant alkenyl group were prepared and utilised for anchoring to a SiMe2H modified support by Pt-catalysed hydrosilylation reaction. Prepared compounds were characterised by standard spectroscopic methods (IR, NMR, MS). The heterogeneous systems were characterised by MAS NMR and IR spectroscopy, powder XRD, ICP-OES, TGA and the textural parameters were determined from nitrogen adsorption/desorption isotherms. For all prepared materials was studied the catalytic activity for ethylene trimerization and the selectivity to 1-hexene.
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Catalytic function of DNA-dependent RNA polymerases
Sýkora, Michal ; Vopálenský, Václav (advisor) ; Lichá, Irena (referee)
DNA-dependent RNA polymerase is a highly organised protein complex that is responsible for gene expression and its regulation. Multisubunit RNA polymerase with its several catalytic activities is responsible for transcription of genes to RNA copies in all cellular organisms. During transcription RNA polymerase undergoes substantial conformational changes depending on the conditions in a particular cell. RNA polymerase in a state designated as an elongation complex passes through repetitive cycles of adding a nucleotide to the growing RNA chain. The active center contains two magnesium ions which coordinate the reactive groups of substrates. Furthermore, the active center contains structural elements that participate in binding of substrate, propper orientation of substrate towards the template strand and translocation of the RNA polymerase. The most important of these mobile structural elements are the bridge helix and the trigger loop whose conformational changes accompanies nucleotide addition cycle. Advances in the structural and biochemical characterization of RNA polymerase open new possibilities in the understanding of the transcription mechanism, its fidelity and control.
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Synthesis of aromatic compounds possessing the fluorene unit
Caivano, Ilaria ; Kotora, Martin (advisor) ; Starý, Ivo (referee) ; Tobrman, Tomáš (referee)
Thermal cyclotrimerization was first discovered in 1866 by Bertholet, then, in 1948, Reppe and Schweckendiek reported the first transition metal catalyzed [2+2+2] cyclotrimerization of alkynes using Ni complexes. In the following 70 years of research, transition metal catalyzed [2+2+2] cyclotrimerization have become a powerful method for the synthesis of variously decorated aromatic rings and new catalytic systems as well as reaction conditions have been successfully applied. Herein, I would like to show the use of this reaction for the synthesis of the important class of fluorene-based compounds. In particular, a regioselective cyclotrimerization of 2,4-disubstituted fluorenols was achieved by Ru-catalyzed partially intermolecular [2+2+2] cyclotrimerization of diynes with terminal alkynes. Rh-based complex proved to be a straightforward transition metal catalyst for the construction of selectively fluorinated [5] and [6]helical dispiroindenofluorenes using intramolecular [2+2+2] cycloaddition of triynediols as the key synthetic step. Moreover, Ni complexes demonstrated to be a valid choice for the selective synthesis of unsymmetrical [7]helical indenofluorenones, while other catalytic systems based on Rh, Ru, Pd and Co gave mixture of the desired cyclotrimerization compound together with the...
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Theoretical Investigation of Low-dimensional Magnetic Materials
Li, Shuo ; Grajciar, Lukáš (advisor) ; Frauenheim, Thomas (referee) ; Jelínek, Pavel (referee)
Low-dimensional (D) materials, such as graphene, transition metal dichalcogenides and chalcogenide nanowires, are attractive for spintronics and valleytronics due to their unique physical and chemical properties resulting from low dimensionality. Emerging concepts of spintronics devices will greatly benefit from using 1D and 2D materials, which opens up new ways to manipulate spin. A majority of 1D and 2D materials is non-magnetic, thus their applications in spintronics are limited. The exploration, design and synthesis of new 1D and 2D materials with intrinsic magnetism and high spin-polarization remains a challenge. In addition, the valley polarization and spin-valley coupling properties of 2D materials have attracted great attention for valleytronics, which not only manipulates the extra degree of freedom of electrons in the momentum space of crystals but also proposes a new way to store the information. The computational investigation of magnetic and electronic properties of low-dimensional materials is the subject of this thesis. We have systematically investigated geometric, electronic, magnetic and valleytronic properties of several 2D and 1D materials by using the density functional theory. These investigations not only theoretically show rich and adjustable magnetic properties of...
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Metal nanoparticles in zeolites
Zhang, Yuyan ; Čejka, Jiří (advisor) ; Zima, Vítězslav (referee) ; Kubička, David (referee)
Zeolites with encapsulated metal nanoparticles have attracted a wide attention in heterogeneous catalysis due to their high catalytic activity, selectivity, and stability. The PhD thesis was focused on design and synthesis of metal@zeolite catalysts with small and uniformly distributed metal nanoparticles. The main interests were encapsulation of metal nanoparticles into zeolites by co-crystallization strategy and 2-dimensional to 3-dimensional zeolite transformation approach. The PhD work was performed at the Department of Synthesis and Catalysis at J. Heyrovský Institute of Physical Chemistry and Department of Physical and Macromolecular Chemistry, Faculty of Science at Charles University under the supervision of Prof. Jiří Čejka. Zeolites are inorganic crystalline aluminosilicates with microporous framework structures. The micropores of zeolites provide the ideal microenvironment to accommodate metal nanoparticles. During metal nanoparticles formation in zeolite micropores, they can be limited by a rigid framework, preventing the aggregation and leaching of metal during the reaction process. Furthermore, the diameters of zeolite micropores are usually in the range of 0.3-1.5 nm, which can be used to discriminate molecules depending on their size and shape, thus endowing the metal@zeolite...
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Heterogeneous catalysis of terpenoid redox reactions
Kurucová, Svetlana ; Přech, Jan (advisor) ; Bulánek, Roman (referee)
Heterogeneous catalysts for Meerwein-Ponndorf-Verley (MPV) reduction of ketones and aldehydes are investigated due to issues connected with water sensitivity and separation problems of homogeneous catalysts. During MPV reduction, a hydrogen atom is transferred from the sacrificial alcohol onto the carbonyl group of the ketone/aldehyde forming corresponding alcohol. Tin and zirconium containing zeolites are active catalysts in this hydrogen transfer reaction. However, when using conventional 3D zeolites in the reduction of bulky molecules, e.g., terpenoid compounds, problems with active site accessibility for these bulky reactants may arise. The use of 2D pillared zeolites may represent a solution to the diffusion problem. Silica metal-oxide pillars increase the distance between individual layers of a 2D (lamellar) zeolite and thus improve the active site accessibility. 2D catalysts were prepared by pillaring a parent lamellar pure-Si MFI with a mixture of tetraethyl orthosilicate and Zr (IV) isopropoxide or Sn (IV) isopropoxide, while conventional 3D zeolites were synthesised hydrothermally. The activity of Sn and Zr containing pillared catalysts was compared with the activity of the 3D MFI and beta zeolites in MPV reduction of furfural and citronellal. The 2D zeolites, however, did not facilitate...
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Shape selectivity of ADOR zeolites in gas-phase m-xylene isomerisation
Remperová, Natália ; Mazur, Michal (advisor) ; Kubička, David (referee)
Zeolites are microporous crystalline aluminosilicates. They are used as catalysts due to their acidity, shape selectivity, high surface area, high thermal, and chemical stability. New types of zeolitic materials are of interests as catalysts for various reactions. Isomerisation of m-xylene is sensitive to shape and dimensionality of pores, thus it is excellent model reaction for zeolites characterisation. The aim of this thesis is to investigate shape selectivity effects of isoreticular zeolites on the catalytic performance in m-xylene isomerisation. Isoreticular zeolites have the same crystalline layers connected in various way resulting in different, tuneable pore systems. The catalytic behaviour of the studied zeolites was compared to commercial ZSM-5 zeolite catalysts. Isoreticular zeolites were prepared via ADOR method. This new method is a top-down approach for zeolite synthesis providing materials with preserved crystalline layers, but different channel systems. Parent Al-UTL (14- and 12-ring channels) zeolite was prepared via hydrothermal synthesis. This material was utilised for the synthesis of daughter zeolites with various channel systems: Al-IPC-7 (14- and 12-ring, as well as 12- and 10-ring channels), Al-IPC-2 (12- and 10-ring channels), Al-IPC-6 (12- and 10-ring, as well as 10- and...
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