National Repository of Grey Literature 57 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Electrochemically Investigated pH-dependent Redox Properties of Copper Complexes of Azamacrocyclic Ligands
Koláčná, Lucie ; Maďar, M. ; Kubíček, V. ; Ludvík, Jiří
Investigated Cu(II) complexes are based on plain or cross-bridged cyclam. The\nelectrochemically inactive cyclam was modified by carboxylate, phosphonate, or phenolate\npendant arms. Cu(II) represents the main redox center of the complexes. Modification of the\nligand causes a changed pattern of complex redox response in buffered aqueous solution.\nIrreversible Cu(II) reduction results in complex decomposition to amalgamated copper and\nligand in excess. After Cu(0) electrochemical in situ re-oxidation, copper and ligand are recomplexed.\nComplexes undergo isomerization, accelerated by increasing the temperature. The\ninfluence of pH on complex isomerization and the reversibility of its reduction was described.
(Spectro) Electrochemical Study of Cibalackrot Derivatives – Potential Chromophores for Singlet Fission\n
Šimková, Ludmila ; Lušpai, Karol ; Klíma, Jiří ; Ludvík, Jiří
Recently, substantial attention has been paid to the search for suitable chromophores for singlet fission. This photophysical effect promises to increase the maximum of theoretical efficiency of solar cells. One type of candidates are derivatives of cibalackrot. Redox properties are critical for their use. Our electrochemical work is focused on the study of oxidation and reduction of a series of substituted cibalackrot derivatives using classic voltammetric techniques and their combination with in situ UV-vis and EPR spectroscopy. The results show the reversible formation of the radical anion (cation) in the first reduction (oxidation) step enabling determination of ´´electrochemical´´ HOMO-LUMO gap.
Redox Properties of Conjugated Phosphole Derivatives – Electrochemical Study
Koláčná, Lucie ; Polák, P. ; Tobrman, T. ; Ludvík, Jiří
The study describes pentasubstituted phospholes with a π-conjugated arms in positions 2 and 5 of the phosphole ring. According to the expectations, substituents with electron-donating groups led to lower oxidation potentials, the presence of electron-withdrawing groups shifts the reduction potential to less negative values. Because all studied phospholes have multiple substituents of both types, their resulting potentials represent the sum of their influences. Moreover, since many of the studied compounds have two redox centers (phosphole moiety itself and the pi-conjugated arm), their locations were determined and intramolecular interactions were followed, because substituents which can be conjugated with the π-system of phosphole are able to extend the delocalized π-system resulting in stabilization of primary redox intermediates. Chemical modification of phospholes using various combinations of substituents can set the desired electrochemical properties of studied molecules.
Oxidation Processes of N-methylguanines
Trnková, L. ; Třísková, I. ; Liška, Alan ; Ludvík, Jiří
The oxidation processes of N-methylguanines were investigated in both experimental and\ntheoretical way. Voltammetric oxidation potentials of guanine and its methyl analogues,\nacquired on polymer pencil graphite electrode (pPeGE), were compared with the HOMO\n(SOMO) energies calculated by density functional (DFT) methods. Our study contributes to\nunderstanding not only the oxidation processes of methylated guanines but also their role in\nepigenetics.
Differences in Electrochemical Reduction of Mono- and Polynuclear Acylgermanes
Šimková, Ludmila ; Dunlop, David ; Liška, Alan ; Ludvík, Jiří
Recently, titanocene derivatives have been investigated in term of their potential use as\ncytostatics in the treatment of oncological diseases. The potentials for reduction or oxidation of\nindividual substances are one of the key properties which fundamentally affect the cytostatic\nefficiency. Our previous results led us to investigate the redox properties of series of titanocene\ndifluoride and dichloride derivatives. This study is mainly focused on the effect of the\nsubstitution of cyclopentadienyl ring and the halide anion on the redox properties of the\nderivative.
Differences in Electrochemical Reduction of Mono- and Polynuclear Acylgermanes
Liška, Alan ; Frühwirt, P. ; Haas, M. ; Ludvík, Jiří ; Gescheidt-Demmer, G.
Ail the studied compounds accept first electron under formation a stable anion radical. The\ncorresponding reduction potentials in aprotic media depend on electronic (inductive,\nmesomeric) properties of the substituents, their number, and position. Here, aromatic acyl group\n(benzoyl group with various substitution on aromatic ring) is the principal substituent. The\nredox properties of presented organoelement compounds with central heteroatom Ge (Si, Sn)\nare controlled by peripheral carbonyl groups (in role of redox centers), their number, and\naromatic ring substitution. The measured first reduction potentials E1 values are found in wide\nrange (> 900 mV) due to the fact that the redox centers are carbony 1 groups connected through\nheteroatom in case of acylgermanes, while for di- and trinuclear derivatives (which are\nmolecules with multiple redox centers) the easiest reducible center is the bridging aromatic unit\ninfluenced by the closest carbonyl groups. Thus, it is possible to distinguish both groups ofnonequivalent\ncarbonyl substituents.
EPR-Electrochemical Study of Reduction Mechanism of Pyrene-Cyclobutene Conjugates
Koláčná, Lucie ; Polák, P. ; Klíma, Jiří ; Tobrman, T. ; Ludvík, Jiří
Reduction mechanism of pyrene-cyclobutene conjugates were studied electrochemically and\nspectro-electrochemically. Analysis and interpretation of spectro-electrochemical data of\nconjugates revealed intramolecular communication of electrons and enabled determination of\nredox mechanism of conjugates. This knowledge is fundamental for tuning the required redox\nproperties of molecules just by chemical modification. Studied molecules represent promising\nmaterial for organic semiconductor materials.
Electrochemistry of Phospholes
Koláčná, Lucie ; Liška, Alan ; Ludvík, Jiří
Seventeen pentasubstituted phospholes with expected application in organic electronics were\nsynthesized and characterized electrochemically and by UV-vis spectra. Quantum chemical\ncalculations ofredox potentials and HOMO-LUMO energies were performed and experimental\nand theoretical data were successfully correlated. Tuning of redox properties can be achieved\nby combination of induction and resonance effects of substituents, extension / diminution of\nthe pi- delocalized system and by steric changes which affect intramolecular electron\ncommunication.
Mercury Electrodes as Tools for Voltammetric Determination of Biologically Active Organic Compounds and for Detection of Their Interaction with DNA
Horáková, Eva ; Vyskočil, Vlastimil (advisor) ; Ludvík, Jiří (referee) ; Vytřas, Karel (referee)
The main aim of this work was to use traditional mercury electrodes for the development of voltammetric methods of determination of organic xenobiotics and for the electrochemical study of the interaction between double-stranded deoxyribonucleic acid (DNA) and these compounds. In relation to my previous research work (conducted in the framework of my diploma thesis), firstly, 4-nitrobiphenyl (4-NBP), the suspected carcinogen, was studied. Interaction of DNA with 4-NBP was studied using differential pulse voltammetry (DPV), cyclic voltammetry (CV), and chronocoulometry at a hanging mercury drop electrode (HMDE), and using CV and alternating current voltammetry at a DNA modified HMDE. Using CV, the reduction mechanism was investigated. The interaction of DNA with 4-aminobiphenyl (4-ABP), a metabolite of 4-NBP, and 4-NBP reduction intermediates was studied. It was found that the interaction of DNA with 4-NBP or 4-ABP results in a formation of a DNA aggregate with these analytes. The second studied analyte was methyl violet 2B (MV). For determination of MV in a buffered solution were used: direct current tast polarography and differential pulse polarography at a dropping mercury electrode, and direct current voltammetry, DPV, and differential pulse adsorptive stripping voltammetry (DPAdSV) at HMDE. The...
Porphyrazine film for use in electrochemical sensor
Merhoutová, Jana ; Nesměrák, Karel (advisor) ; Ludvík, Jiří (referee)
Porphyrazine film for use in electrochemical sensor Abstract: A water soluble N,N',N'',N'''-tetramethyltetra-3,4-pyridinoporphyrazine complex containing cobalt cation (II) as a central atom was used like a mediator for preparation of electrochemical sensor. Such effects on a sensor function like an electrode carrier material, the manner of porphyrazine deposition, pH and thickness of the layer, were studied by cyclic voltammetry method. The sensor was tested for hydrogen detection in water buffer solution consequently.

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3 Ludvík, Jakub
9 Ludvík, Jan
2 Ludvík, Jaroslav
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