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Study of LaCuAl3 structure by means of nuclear magnetic and quadrupole resonance
Sgallová, Ráchel ; Chlan, Vojtěch (advisor) ; Englich, Jiří (referee)
In the presented bachelor thesis the structure of LaCuAl3 was studied on a series of metallic powder samples LaCuxAl4−x, x = 0,75; 0,9; 1 and 1,1 especially with respect to the local symetry of La atoms. 63 Cu, 65 Cu, 27 Al and 139 La nuclear magnetic resonance spectra were measured at room tempera- ture in external magnetic eld of 9,4 T. Some of the measured spectra were compared with simulated ones in order to access the number of nonequiva- lent atoms in the structure. Furthermore, the effect of Al/Cu stoichiometry on nuclear magnetic resonance spectra was observed and diccussed. 1
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Alternative synthesis of of 1-(diphenylphosphino)-1'-(N,N-dimethylaminomethyl)ferrocene
Zábranský, Martin ; Štěpnička, Petr (advisor) ; Vojtíšek, Pavel (referee)
An alternative, more straightforward and effective method for the preparation of 1- (diphenylphosphino)-1'-(N,N-dimethylaminomethyl)ferrocene was developed using 1-bromo- 1'-(diphenylphosphino)ferrocene as the starting material and Eschenmoser's salt as an aminomethylation agent. Purity of thus prepared phosphinoamine was verified by 1 H and 31 P NMR spectroscopy and by comparison of the data with those reported in the literature (M. E. Wright, Organometallics, 1990, 9, 853). The coordination chemistry of this compound was investigated in gold(I) complexes. Thus, chlorido[1-(diphenylphosphino)-1'-(N,N-dimethyl- aminomethyl)ferrocene]gold(I) complex was synthesized and converted to ill-defined [1- (diphenylphosphino)-1'-(N,N-dimethylaminomethyl)ferrocene]gold(I) perchlorate by halogen abstraction with AgClO4. Protonization of the nitrogen atom in both compounds with hydrogen chloride yielded the corresponding hydrochlorides. It was shown that 1- (diphenylphosphino)-1'-(N,N-dimethylaminomethyl)ferrocene is coordinated as a simple phosphine in the resulting complexes while its amine nitrogen is protonated. All these complexes were characterized by means of 1 H, 31 P and 13 C NMR spectroscopy, mass spectroscopy with electrospray ionisation, elemental analysis and by single-crystal X-ray diffraction analysis.
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Hyperfine Interactions in Ferrites with Spinel Structure
Chlan, Vojtěch
Title: Hyperfine Interactions in Ferrites with Spinel Structure Author: Vojtěch Chlan Faculty of Mathematics and Physics, Charles University in Prague Supervisor: Prof. RNDr. Helena Štěpánková, CSc. Abstract: Ferrite systems with spinel structure, manganese ferrite, lithium ferrite and magnetite, are studied experimentally by nuclear magnetic resonance (NMR) spectroscopy and from the first principles by electron structure calculations based on density functional theory (DFT). Manganese ferrites with various degrees of manganese-iron inversion and with different manganese contents are investigated, with respect to magnetic structure and cationic arrangement. An approach for NMR spectra interpretation is elaborated on ordered lithium ferrite, consisting in matching the calculated hyperfine field anisotropy with experimental results. This method is then applied to low temperature structure of magnetite, showing a promising path towards solving its complicated structure, orbital and charge ordering. The switching of magnetic easy axis induced by external magnetic field is observed in magnetite and the accompanying structural changes are studied by means of magnetic and NMR measurements. Magnetite with cationic vacancies is investigated by analyzing satellite structure induced by the vacancies; it is shown that...
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NMR Study of Oligonucleotide Structures
Římal, Václav ; Štěpánková, Helena (advisor) ; Spěváček, Jiří (referee) ; Sychrovský, Vladimír (referee)
Title: NMR Study of Oligonucleotide Structures Author: Václav Římal Department: Department of Low-Temperature Physics Supervisor: Prof. RNDr. Helena Štěpánková, CSc., Department of Low- Temperature Physics Abstract: The dynamics of nucleic acids plays a fundamental role in the interactions with proteins. Some processes are governed by changes in DNA stability and flexibility caused by sequence alterations or chemical modifications without substantial structural impact. We employed line-shape analysis of variable-temperature 1H NMR spectra to deeply investigate the melting transition of DNA structures. We observed a significant influence of the sequence beyond the nearest neighbours on chemical shifts and thermodynamics of the double helix. The CpG motif is especially sensitive to its distant surroundings and for a particular oligonucleotide it was even found to undergo an unexpected local conformational transition. A strong cooperativity in the duplex dis- ruption was witnessed by both the equilibrium and kinetic aspects as well as by distant effects of cytosine methylation. We propose a two-state melt- ing scheme also for a fragment of a transcription element proved here to fold as a hairpin with a six-membered loop. In addition, we describe the properties of self-assemblies of riboguanosine and...
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Fluorine nuclear relaxation times in chelates with lanthanides
Bobrova, Yulia ; Římal, Václav (advisor) ; Wagnerová, Dita (referee)
Contrast agents containing fluorine have great prospects for magnetic resonance imaging in medicine. Low representation of fluorine in human body and the suitable magnetic properties of its nucleus 19 F, provide great sensitivity. The slow relaxation of 19 F, can be shortened by using paramagnetic complexes.In this thesis, transversal and longitudinal 19 F relaxation times of chelates with different paramagnetic lanthanides (Ce, Yb,Tm, Dy, Ho) were measured in two different magnetic fields: 4,7 and 11,7 T. Their values meet the expected assumptions. Furthermore, the values are compared with Bloch-Redfield- Wangsness theory.While Ho, Tm, and Dy reduce fluorine nuclear relaxation times to milliseconds, which is too short for MRI, relaxation rates of Ce a Yb reach approximately 100ms. Such relaxation rates can be considered as optimal for imaging methods. On the basis of our results it is possible to find suitable candidates for fluorine contrast media and optimize the measurement sequence settings in further research or in clinical use.
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Study of LaCuAl3 structure by means of nuclear magnetic and quadrupole resonance
Sgallová, Ráchel ; Chlan, Vojtěch (advisor) ; Englich, Jiří (referee)
In the presented bachelor thesis the structure of LaCuAl3 was studied on a series of metallic powder samples LaCuxAl4−x, x = 0,75; 0,9; 1 and 1,1 especially with respect to the local symetry of La atoms. 63 Cu, 65 Cu, 27 Al and 139 La nuclear magnetic resonance spectra were measured at room tempera- ture in external magnetic eld of 9,4 T. Some of the measured spectra were compared with simulated ones in order to access the number of nonequiva- lent atoms in the structure. Furthermore, the effect of Al/Cu stoichiometry on nuclear magnetic resonance spectra was observed and diccussed. 1
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Preparation of titanium and zirconium metallocene complexes with pendant nitrile groups
Večeřa, Miloš ; Štěpnička, Petr (advisor) ; Vojtíšek, Pavel (referee)
Preparation of metallocene complexes of titanium and zirconium with pendant nitrile groups Miloš Večeřa bachelor thesis Abstract: Two cyclopentadienide salts with pendant nitrile groups were prepared in the form of their corresponding lithium salts and these salts were utilized for the preparation of titanium and zirconium metallocene complexes. One of the ligands was already described in the literature, while the other as well as all the prepared group 4 metallocene complexes are new compounds. Starting materials for these syntheses were 6,6-dimethylfulvene and spiro[2.4]hepta-4,6-diene which, upon a nucleophilic attack by 2-lithio-2-methylpropanenitrile, afforded the corresponding substituted lithium cyclopentadienides, which were characterized by 1 H and 13 C NMR spectroscopy and infrared spectroscopy. Then lithium salts were reacted with Cp*TiCl3 and Cp*ZrCl3 to give the corresponding metallocene dichlorides. Solid-state structures of the prepared titanocene dichlorides were elucidated by means of single crystal X-ray diffraction analysis. The obtained structures allowed a comparison with the known structures of the previously prepared homologous derivative. Unfortunately the corresponding zirconocene dichlorides did not crystallize. Moreover, all the newly prepared metallocenes were characterized by 1...
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Hyperfine Interactions in Ferrites with Spinel Structure
Chlan, Vojtěch
Title: Hyperfine Interactions in Ferrites with Spinel Structure Author: Vojtěch Chlan Faculty of Mathematics and Physics, Charles University in Prague Supervisor: Prof. RNDr. Helena Štěpánková, CSc. Abstract: Ferrite systems with spinel structure, manganese ferrite, lithium ferrite and magnetite, are studied experimentally by nuclear magnetic resonance (NMR) spectroscopy and from the first principles by electron structure calculations based on density functional theory (DFT). Manganese ferrites with various degrees of manganese-iron inversion and with different manganese contents are investigated, with respect to magnetic structure and cationic arrangement. An approach for NMR spectra interpretation is elaborated on ordered lithium ferrite, consisting in matching the calculated hyperfine field anisotropy with experimental results. This method is then applied to low temperature structure of magnetite, showing a promising path towards solving its complicated structure, orbital and charge ordering. The switching of magnetic easy axis induced by external magnetic field is observed in magnetite and the accompanying structural changes are studied by means of magnetic and NMR measurements. Magnetite with cationic vacancies is investigated by analyzing satellite structure induced by the vacancies; it is shown that...
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Alternative synthesis of of 1-(diphenylphosphino)-1'-(N,N-dimethylaminomethyl)ferrocene
Zábranský, Martin ; Štěpnička, Petr (advisor) ; Vojtíšek, Pavel (referee)
An alternative, more straightforward and effective method for the preparation of 1- (diphenylphosphino)-1'-(N,N-dimethylaminomethyl)ferrocene was developed using 1-bromo- 1'-(diphenylphosphino)ferrocene as the starting material and Eschenmoser's salt as an aminomethylation agent. Purity of thus prepared phosphinoamine was verified by 1 H and 31 P NMR spectroscopy and by comparison of the data with those reported in the literature (M. E. Wright, Organometallics, 1990, 9, 853). The coordination chemistry of this compound was investigated in gold(I) complexes. Thus, chlorido[1-(diphenylphosphino)-1'-(N,N-dimethyl- aminomethyl)ferrocene]gold(I) complex was synthesized and converted to ill-defined [1- (diphenylphosphino)-1'-(N,N-dimethylaminomethyl)ferrocene]gold(I) perchlorate by halogen abstraction with AgClO4. Protonization of the nitrogen atom in both compounds with hydrogen chloride yielded the corresponding hydrochlorides. It was shown that 1- (diphenylphosphino)-1'-(N,N-dimethylaminomethyl)ferrocene is coordinated as a simple phosphine in the resulting complexes while its amine nitrogen is protonated. All these complexes were characterized by means of 1 H, 31 P and 13 C NMR spectroscopy, mass spectroscopy with electrospray ionisation, elemental analysis and by single-crystal X-ray diffraction analysis.
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