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(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.
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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.
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Redox Properties of Fluorinated Derivativers of 1,3-Diphenylisobenzofuran-Chromophores for Singlet Fission
Šimková, Ludmila ; Ludvík, Jiří
Derivatives of 1,3-diphenylisobenzofuran attract interest because they should be efficient as the molecules for singlet fission. The understanding of singlet fission in isolated molecules might be advantageous for use as solar cell sensitizers. This study is focused on fluorinated derivatives of 1,3-diphenylisobenzofuran and the effect of the position of fluorine atoms on their redox properties. For characterization of the redox properties standard electrochemical methods, and in situ UV-vis and EPR spectroscopy techniques were used.
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Redox Properties of Quasi Dimer of 1,3-diphenylisobenzofuran for Singlet Fission
Šimková, Ludmila ; Ludvík, Jiří
Molecules on the base of 1,3-diphenylisobenzofuran attract an interest because of their\npossible efficiency for singlet fission This study is focused on electrochemical behaviour of\nthe „quasi dimer“ of 1,3-diphenylisobenzofuran. For characterization of reduction mechanism\nin situ UV-vis and EPR spectroscopy were used. The monomer 1,3-diphenylisobenzofuran\nand its CH2 dimer were added to this study for comparison. The redox properties of both\ncompared molecules are similar. The location and the nature of the covalent bridging unit in\nCH2dimer have small effect onthe redox potentials. But the pi-conjugation in the molecule of\nquasi dimer causes approximately 0.2 V easier oxidization and reduction.
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Electrochemical investigation of redox reactions of 2,2-dinitroethen-1,1-diamin (FOX-7) in aqueous media.
Šimková, Ludmila ; Volke, Jiří (referee) ; Liška, František (advisor)
Hlavním směrem ve výzkumu výbušnin je hledání nových sloučenin, které by měly vysoký výkon a nízkou iniciační citlivost. Jednou z takových látek je před deseti lety poprvé připravený 2,2-dinitroethen-l,l-diamin (FOX-7). Tyto molekuly jsou zajímavé nejen z hlediska praktického použití, ale i z hlediska základního výzkumu molekul s více redox centry. Redukce ve vodném, tedy protickém prostředí má zde ten význam, že mechanismu intramolekulárních redox reakcí (vedoucích jakémusi "zpomalenému výbuchu" v nádobce) konkuruje vnější protonizace a tedy redukce spojená s protonizací. To se projevilo tím, že zatímco polarografické experimenty odhalily v celém rozsahu pH osm redukčních dějů s celkovou spotřebou 18 elektronů na jednu molekulu FOX-7, preparativní elektrolýza vedoucí úplné konverzi vykázala (podle potenciálu a pH) spotřebu pouze šesti, resp. čtyř elektronů. Pozoruhodné jsou i další získané výsledky, jako např. závislost vzájemného poměru limitních proudů na koncentraci látky nebo otázka produktů elektrolýz.
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Structural, Redox and Spectrometric Characterization of Energetic Material FOX-7 (2,2-dinitroethene-1,1-diamine) in Solution
Šimková, Ludmila ; Ludvík, Jiří
The investigation of energetic materials, especially organic nitro-amino-derivatives, always has attracted attention of physical chemists. However, published articles demonstrate lack of systematic study of molecules based on aliphatic backbones, rather than aromatic structures. This work represents the first systematic electrochemical and spectrometric characterization of 2,2-dinitroethene-1,1-diamine (FOX-7) in aqueous and aprotic solvent. Based on the results obtained from combination of electrochemistry with spectrometric methods, the actual structure of FOX-7 in various media was revealed, its reducibility described and radical intermediates as well as products were intercepted, isolated and characterized.
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Proč a čím se namazat?
Kociánová, R. ; Šimková, Ludmila ; Boháčová, J.
Školní projekt Proč a čím se namazat?, seznamuje žáky aktivní formou s problematikou ubývání ozónové vrstvy, příčinami a důsledky této skuteč nosti. Projekt vede žáky k uvědomění si negativního vlivu činnosti lidí na životní prostředí a zodpovědnosti každého jedince za životní prostředí a své vlastní zdraví.
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FOX-7 - Study of Reduction Products of Spectroelectrochemical Methods
Šimková, Ludmila ; Dmitrieva, E. ; Klíma, Jiří ; Dunsch, L. ; Ludvík, Jiří
A new energetic material 2,2-dinitroethene-1,1-diamine (FOX-7) is recently broadly tested because of its high performance and very low sensitivity. On the other hand, its electrochemical and redox properties have not been studied yet. Our results show that FOX-7 is reduced in aprotic solvents only by two one-electron steps up to -2.9 V. The color changes during reduction of FOX-7 and reversibility of the redox process indicate the presence of radical intermediates. Therefore in situ UV-vis-NIR and ESR spectroelectrochemical investigations were performed. The products after exhaustive electrolyses were separated by HPLC and are identified by mass spectrometry. The possible formation of gaseous products was followed online EC-GC.
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Electrochemical and spectrometric study of FOX-7 in aprotic solvents
Šimková, Ludmila ; Ludvík, Jiří ; Klíma, Jiří
2,2-Dinitroethene-1,1-diamine (FOX-7) is a recently developed and broadly tested energetic material with high efficiency and low sensitivity. Generally, explosion is based on thermally initiated chain of intramolecular redox reactions. Recently it has been found that electrochemical reduction in aqueous solutions is also able to provoke the chain of follow-up processes leading to total decomposition of the parent substance yielding gaseous products analogously like during explosion. Similarly, results from reductive electrolysis of FOX-7 in aprotic solvents show analogous course of degradation. The first transferred electron activates the molecule and initiated the formation of colored radical intermediates that have been spectroscopically characterized
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