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Molecular recognition in the gas phase: Chiral recognition
Vinklová, Nicole ; Roithová, Jana (advisor) ; Bednář, Petr (referee)
This thesis deals with molecular recognition of chiral compounds in the gas phase. Tandem mass spectrometry was used as a detection method in this case. Compounds, which have been studied, were MacMillan organocatalysts and proline with different chirality. Three experiments were carried out. Determination of activation energy for fragmentation of proline complexes with amines, where we have studied complexes with 2-aminobutane and 2-aminohexane of different chirality. Fragmentation studies of diastereoisomeric complexes of Cu2+ and three chiral ligands were carried out at two different collision energies. There the largest chiral effect was observed. The last topic was a measurement of the rate constants. It was aimed at dissociation and exchange reactions of complexes. Keywords: mass spectrometry, kinetic method, chiral compounds, chiral recognition, proline, organocatalysis
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Investigation of copper complexes using mass spectrometry
Yassaghi, Ghazaleh ; Roithová, Jana (advisor) ; Jaklová Dytrtová, Jana (referee) ; Polášek, Miroslav (referee)
This dissertation thesis reports the study of several copper complexes and their reactivity in the gas phase. The complexes were analyzed using different methods, namely, electrospray ionization-mass spectrometry (ESI-MS), infrared multiphoton dissociation (IRMPD) spectroscopy and theoretical calculations. In the first part, the complexes of redox-active ligands (catechol, maltol, and phenanthraquinone) with copper were studied under electrospray ionization conditions. [Cu(PQ)2]+ (PQ = 9,10-phenanthraquinone), [Cu(maltol)(maltol-H)]+ and [Cu(maltol)(maltol-H2)]+ were produced by electrospray ionization. The copper complexes were compared with complexes of other metals (Zn, Ag, and Na), and the structures were studied by collision induced dissociation (CID) and IRMPD spectroscopy. The redox process of copper complexes was studied using the C-O stretching mode as a redox marker and using fragmentation experiments. Both the phenanthraquinone and maltol ligands showed redox activity of the studied copper complexes in the gas phase. In the second part, negatively charged complexes of copper with pincer ligand L (L = N,N'-bis[2,6-diisopropylphenyl]-2,6-pyridinedicarboxamide) were investigated to show the effects of different counter-ions. The results showed that electrospray ionization of copper chlorate...
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Mechanisms of metal-catalyzed reactions: an electrospray ionization mass spectrometry approach
Anania, Mariarosa ; Roithová, Jana (advisor) ; Hanusek, Jiří (referee) ; Slanina, Tomáš (referee)
Mass spectrometry, ion spectroscopy, NMR and quantum-chemical calculations are commonly combined to study the structures, properties and reactivity of intermediates in metal- catalyzed reactions. However, our ability to identify the main species present in solution by electrospray ionization mass spectrometry (ESI-MS) and to confirm whether these species are indeed reactive intermediates involved in the study reactions remains limited. Thus, we developed a new method combining isotope labeling with kinetic data extraction for the identification and analysis of intermediates in reaction mixtures termed delayed reactant labeling (DRL). Accordingly, this thesis is divided into 5 Chapters. Chapter 1 gives an overview of ESI-MS as a tool for studying the mechanisms of metal-catalyzed reactions, focusing on gold chemistry. Chapter 2 describes the experimental (ESI-MS, ion spectroscopy and gas chromatography) and theoretical (DFT) methods used in this thesis and the corresponding instrumentation. Chapter 3 details the development of the delayed reactant labeling (DRL) as a technique for studying reaction kinetics by mass spectrometry and examples how it was used to investigate problems in the following chapter. Chapter 4, shows that a Au(I) complex can act as a strong base in a solution containing water...
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Photodissociation studies of xanthene dyes, iron(III) azido complexes and hemithioindigo molecular switches in the gas phase
Navrátil, Rafael ; Roithová, Jana (advisor) ; Žabka, Ján (referee) ; Volný, Michael (referee)
Electronic excitation triggered by the absorption of light enables numerous chemical, physical and biological processes and transformations. Accordingly, full control over the processes involving excited molecules requires an in-depth knowledge of electronic UV/vis spectra and potential energy surfaces. Unsurprisingly, most electronic spectra are acquired in the condensed phase in which molecules are dissolved and most transformations occur. However, our knowledge of excitation, transformations and processes at the level of isolated molecules is still limited, partly because such studies require unconventional experimental approaches and equipment. This Thesis describes experimental methods for recording electronic spectra of isolated molecules in the gas phase by ion spectroscopy, which combines mass spectrometry with optical spectroscopy. Using these methods, experimental factors which affect the electronic excitation and therefore the electronic spectra of ions were determined and evaluated for various fluorescent xanthene dyes, iron-containing complexes and molecular pho- toswitches. Furthermore, factors which govern photochemical processes, such as photo- oxidation, photoreduction and photoisomerization, were also analyzed in detail, with surprisingly different outcomes from previous studies...
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Investigation of Non-Heme Iron-Oxo Intermediates in the Gas Phase
Andris, Erik ; Roithová, Jana (advisor) ; Nachtigall, Petr (referee) ; Klán, Petr (referee)
I used helium-tagging infrared photodissociation spectroscopy of ions in the IR (IRPD) and vis (visPD) range in conjunction with gas-phase reactivity studies to study biomimetic terminal iron-oxo complexes. In first part of the work, I measured IRPD spectra of iron(IV)- oxo complexes of TMC, N4Py and PyTACN amine ligands in different charge states. Results show that the gas-phase Fe=O stretching frequencies are, on average, blue-shifted by 9 cm-1 with respect to the condensed phase. I prepared stereoisomers of [(PyTACN)FeIV (O)(X)]+ complexes (X = CF3COO, NO3) that were in quintet and triplet state using nitrate cleavage method and showed that the Fe=O frequency of these iron(IV)-oxo complexes is not affected by the spin state. Gas-phase reactivity shows that dicationic complexes react with 1,4- cyclohexadiene by hydride transfer and monocationic complexes engage in hydrogen atom transfer (HAT) from the methylene group and oxygen atom transfer to the C=C bond. Variation of the ligand trans to the Fe=O unit has the greatest influence on reactivity, whereas the spin state has a modest effect. In the second part of the work, I prepared and studied gas- phase iron(III)-oxo complexes with N4Py, TPA, TQA and TMC ligands. IRPD and visPD spectra in conjunction with DFT calculations allowed me to assign the...
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Investigation of copper complexes using mass spectrometry
Yassaghi, Ghazaleh ; Roithová, Jana (advisor) ; Jaklová Dytrtová, Jana (referee) ; Polášek, Miroslav (referee)
This dissertation thesis reports the study of several copper complexes and their reactivity in the gas phase. The complexes were analyzed using different methods, namely, electrospray ionization-mass spectrometry (ESI-MS), infrared multiphoton dissociation (IRMPD) spectroscopy and theoretical calculations. In the first part, the complexes of redox-active ligands (catechol, maltol, and phenanthraquinone) with copper were studied under electrospray ionization conditions. [Cu(PQ)2]+ (PQ = 9,10-phenanthraquinone), [Cu(maltol)(maltol-H)]+ and [Cu(maltol)(maltol-H2)]+ were produced by electrospray ionization. The copper complexes were compared with complexes of other metals (Zn, Ag, and Na), and the structures were studied by collision induced dissociation (CID) and IRMPD spectroscopy. The redox process of copper complexes was studied using the C-O stretching mode as a redox marker and using fragmentation experiments. Both the phenanthraquinone and maltol ligands showed redox activity of the studied copper complexes in the gas phase. In the second part, negatively charged complexes of copper with pincer ligand L (L = N,N'-bis[2,6-diisopropylphenyl]-2,6-pyridinedicarboxamide) were investigated to show the effects of different counter-ions. The results showed that electrospray ionization of copper chlorate...
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Direct monitoring of metal-catalyzed reactions using electrospray ionization mass spectrometry
Tsybizova, Alexandra ; Roithová, Jana (advisor) ; Jahn, Ullrich (referee) ; Kvíčala, Jaroslav (referee)
The current dissertation thesis is focused on the investigation of metal-catalyzed reactions using electrospray ionization mass spectrometry as the primary research technique. However, other gas- phase methods such as tandem mass spectrometry, infrared multiphoton dissociation spectroscopy and quantum chemical calculations have also been involved to unravel and support the findings and proposals. As organometallic chemistry is a very broad and complicated topic, this thesis is only focused on a few projects. The fist of them is dedicated to copper acetate speciation in organic solvents, the second - to the mechanistic investigation of copper catalyzed aerobic cross coupling of thiol esters and arylboronic acids, the third studied coordination and bond activation of nickel(II) - phenylpyridine complexes and the last investigated carboxylate assisted C-H activation reactions.
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Ion spectroscopy of reaction intermediates
Škríba, Anton ; Roithová, Jana (advisor) ; Stará, Irena (referee) ; Martinů, Tomáš (referee)
The combination of mass spectrometry, infrared action spectroscopy and quantum-chemical calculations provides a great tool for the study of the structures, properties and reactivities of molecules in the gas phase. This thesis is divided into two main parts. The first part reviews some of the experimental (ESI-MS, ion spectroscopy) and theoretical (DFT) methods used in this thesis and gives a brief description on instrumentation. Second part is presenting four practical applications of gas phase studies in organic and organometallic chemistry: (1) Describing the influence of two functional groups of para-aminophenol on the protonation site. (2) Presenting how the structure and conformation of diethylmalonate is affected by the coordination with silver and gold. (3) Showing the possibility to distinguish between the isobaric complexes and identifying the key intermediates of ruthenium catalyzed C-C coupling. (4) Discussing the possible use of He-tagging infrared spectra not only for structure determination but also for the benchmarking of DFT methods.
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Research of gold catalyzed reactions
Jašíková, Lucie ; Roithová, Jana (advisor) ; Polášek, Miroslav (referee) ; Starý, Ivo (referee)
The main focus of the current dissertation thesis is research of gold catalyzed reactions. I was using mass spectrometry as the primary research technique. I complemented the results with infrared multiphoton dissociation spectroscopy, nuclear magnetic resonance spectroscopy and quantum chemical calculations. I have investigated the interaction of the gold(I) cation with unsaturated hydrocarbons in the first part of my thesis. Secondly, I have studied gold(I) or silver(I) affinity to gold acetylides. In the last part, I have investigated the reaction mechanism of a gold mediated addition of methanol to alkynes. I found out that the gold(I) cation interacts stronger with gold acetylides than with nonactivated triple CC bonds. I showed that the complexes containing two gold atoms represent the key intermediates in the mechanism of addition of methanol to alkynes and that the ligand on the gold catalyst plays a fundamental role in the determination of the mechanism. Powered by TCPDF (www.tcpdf.org)
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Reaction intermediates in homogeneous gold catalysis
Shcherbachenko, Elena ; Roithová, Jana (advisor) ; Matoušová, Eliška (referee)
The presented master thesis is devoted to the investigation of reaction intermediates in homogeneous gold catalysis. Electrospray ionization mass spectrometry (ESI-MS) was used as the primary research technique in this study. Delayed reactant labeling was used as the main method. I have focused mainly on the hydration of 1-phenyl-1-propyne catalyzed by the gold complex [Au(IPr)(MeCN)]BF4 (IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2- ylidene). I have detected two main intermediates containing one or two gold atoms, respectively (monoaurated and diaurated intermediate). I have obtained rate constants for the degradation of the reaction intermediates and their half-lives. I have derived kinetic isotope effects for the formation and the decomposition of the detected intermediates. I have shown that the kinetics of the degradation of both intermediates is identical, therefore I conclude that hydration of alkynes catalyzed by gold complex [Au(IPr)(MeCN)]BF4 proceeds most probably via neutral monoaurated intermediates. These neutral intermediates are detected by ESI-MS as protonated (monoaurated intermediate) or tagged by a second gold cation (diaurated intermediate). Key words: gold catalysis, reaction intermediates, electrospray ionization, mass spectrometry.
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