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Electrochemistry of Nitrocalixarenes
Liška, Alan ; Vojtíšek, Pavel (advisor) ; Cibulka, Radek (referee)
In this diploma thesis a detailed investigation of the step-by-step reduction mechanism of cone-mono-, di-, tri and tetranitrocalix[4]arenes (in non-aqueous DMF) is presented. The intramolecular interaction of reducible (and reduced) centers and its consequences for the geometry of the starting molecule was discussed including the character of radicalic intermediates and their spin state. It was found, that the electrochemically generated radical anions of nitrogroups (unlike their starting electroneutral state) can act as ligands. Therefore, a study of complex formation equilibria of cone-tetranitrocalix[4]arenes with alkali metal cations followed. The possible use of a "stereoelectrochemical" approach (the relationship between geometry or conformation of the molecule and its electrochemical data) was demonstrated in describing and explaining conformational and electrochemical differences between two isomeric dinitrocalix[4]arenes. Finally, a new series of 1,3-alt-tetranitrothiacalix[4]arenes was electrochemically characterized and compared with the "classic" calixarene derivatives. Key words: electrochemistry, calixarenes, stereochemistry
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Electrochemistry of Calixarenes
Liška, Alan ; Ludvík, Jiří (advisor) ; Zima, Jiří (referee) ; Cibulka, Radek (referee)
In the present thesis, both the published and the "ready-to-be-submitted" results concerning electrochemistry of calixarenes are summarized. The main focus is given to the detailed interpretation of experimental data, acquired during a systematic study of electroactive calixarene derivatives. The experiments were conducted under aprotic conditions (DMF) on mercury electrodes (mainly cyclic voltammetry and DC-polarography). It is demonstrated that electrochemistry should not serve only for redox characterization of studied compounds, but it offers a great number of other valuable information. The subject matter of the study are the calix[4]arenes (prevalently in the cone-conformation) which bear one to four reducible or oxidizable substituents ("redox probes") at various positions in order to be electrochemically investigable. Nitro- and nitroso compounds together with aldehydes, ketones, nitriles, aldoximes, carboxylic acids and corresponding esters, sulphones and esters of sulphonic acids are the most discussed compound series. Their relationship between structure and electrochemical response is presented in new connections ("stereoelectrochemistry"), in other words, how the redox probe position on the benzene ring (para-/meta-), bridging groups, or adjacent vs. opposite aromatic units...
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Exectrochemical methods as tools for study complex macrocyclic moleculs
Liška, Alan ; Vojtíšek, Pavel (advisor) ; Liška, František (referee)
By means of electrochemical techniques, the electroreduction of polynitrocalix[4]arenes - molecules with multiple redox centers - was investigated and described. Based on interpretation of experimental data and on their correlation with quantum chemical calculations the relationship between structure and redox properties of the title molecules was revealed and discussed. It was shown that the tetranitrocalix[4]arenes involve two different couples of equivalent nitrogroups, what confirms experimentally the pinched shape of the molecule even in solution. The sequence of reduction steps was determined and the corresponding mechanism described. In the first part of the thesis different reduction mechanisms of p-substituted nitroaromates were found in dependence on substitution. It points to an important influence of lower ring substitution on the redox properties of the whole tetranitrocalix[4]arene.
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Electrochemistry of Calixarenes
Liška, Alan
In the present thesis, both the published and the "ready-to-be-submitted" results concerning electrochemistry of calixarenes are summarized. The main focus is given to the detailed interpretation of experimental data, acquired during a systematic study of electroactive calixarene derivatives. The experiments were conducted under aprotic conditions (DMF) on mercury electrodes (mainly cyclic voltammetry and DC-polarography). It is demonstrated that electrochemistry should not serve only for redox characterization of studied compounds, but it offers a great number of other valuable information. The subject matter of the study are the calix[4]arenes (prevalently in the cone-conformation) which bear one to four reducible or oxidizable substituents ("redox probes") at various positions in order to be electrochemically investigable. Nitro- and nitroso compounds together with aldehydes, ketones, nitriles, aldoximes, carboxylic acids and corresponding esters, sulphones and esters of sulphonic acids are the most discussed compound series. Their relationship between structure and electrochemical response is presented in new connections ("stereoelectrochemistry"), in other words, how the redox probe position on the benzene ring (para-/meta-), bridging groups, or adjacent vs. opposite aromatic units...
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Electrochemistry of Calixarenes
Liška, Alan
In the present thesis, both the published and the "ready-to-be-submitted" results concerning electrochemistry of calixarenes are summarized. The main focus is given to the detailed interpretation of experimental data, acquired during a systematic study of electroactive calixarene derivatives. The experiments were conducted under aprotic conditions (DMF) on mercury electrodes (mainly cyclic voltammetry and DC-polarography). It is demonstrated that electrochemistry should not serve only for redox characterization of studied compounds, but it offers a great number of other valuable information. The subject matter of the study are the calix[4]arenes (prevalently in the cone-conformation) which bear one to four reducible or oxidizable substituents ("redox probes") at various positions in order to be electrochemically investigable. Nitro- and nitroso compounds together with aldehydes, ketones, nitriles, aldoximes, carboxylic acids and corresponding esters, sulphones and esters of sulphonic acids are the most discussed compound series. Their relationship between structure and electrochemical response is presented in new connections ("stereoelectrochemistry"), in other words, how the redox probe position on the benzene ring (para-/meta-), bridging groups, or adjacent vs. opposite aromatic units...
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Electrochemistry of Calixarenes
Liška, Alan ; Ludvík, Jiří (advisor) ; Zima, Jiří (referee) ; Cibulka, Radek (referee)
In the present thesis, both the published and the "ready-to-be-submitted" results concerning electrochemistry of calixarenes are summarized. The main focus is given to the detailed interpretation of experimental data, acquired during a systematic study of electroactive calixarene derivatives. The experiments were conducted under aprotic conditions (DMF) on mercury electrodes (mainly cyclic voltammetry and DC-polarography). It is demonstrated that electrochemistry should not serve only for redox characterization of studied compounds, but it offers a great number of other valuable information. The subject matter of the study are the calix[4]arenes (prevalently in the cone-conformation) which bear one to four reducible or oxidizable substituents ("redox probes") at various positions in order to be electrochemically investigable. Nitro- and nitroso compounds together with aldehydes, ketones, nitriles, aldoximes, carboxylic acids and corresponding esters, sulphones and esters of sulphonic acids are the most discussed compound series. Their relationship between structure and electrochemical response is presented in new connections ("stereoelectrochemistry"), in other words, how the redox probe position on the benzene ring (para-/meta-), bridging groups, or adjacent vs. opposite aromatic units...
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Electrochemistry of Nitrocalixarenes
Liška, Alan ; Vojtíšek, Pavel (advisor) ; Cibulka, Radek (referee)
In this diploma thesis a detailed investigation of the step-by-step reduction mechanism of cone-mono-, di-, tri and tetranitrocalix[4]arenes (in non-aqueous DMF) is presented. The intramolecular interaction of reducible (and reduced) centers and its consequences for the geometry of the starting molecule was discussed including the character of radicalic intermediates and their spin state. It was found, that the electrochemically generated radical anions of nitrogroups (unlike their starting electroneutral state) can act as ligands. Therefore, a study of complex formation equilibria of cone-tetranitrocalix[4]arenes with alkali metal cations followed. The possible use of a "stereoelectrochemical" approach (the relationship between geometry or conformation of the molecule and its electrochemical data) was demonstrated in describing and explaining conformational and electrochemical differences between two isomeric dinitrocalix[4]arenes. Finally, a new series of 1,3-alt-tetranitrothiacalix[4]arenes was electrochemically characterized and compared with the "classic" calixarene derivatives. Key words: electrochemistry, calixarenes, stereochemistry
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Exectrochemical methods as tools for study complex macrocyclic moleculs
Liška, Alan ; Vojtíšek, Pavel (advisor) ; Liška, František (referee)
By means of electrochemical techniques, the electroreduction of polynitrocalix[4]arenes - molecules with multiple redox centers - was investigated and described. Based on interpretation of experimental data and on their correlation with quantum chemical calculations the relationship between structure and redox properties of the title molecules was revealed and discussed. It was shown that the tetranitrocalix[4]arenes involve two different couples of equivalent nitrogroups, what confirms experimentally the pinched shape of the molecule even in solution. The sequence of reduction steps was determined and the corresponding mechanism described. In the first part of the thesis different reduction mechanisms of p-substituted nitroaromates were found in dependence on substitution. It points to an important influence of lower ring substitution on the redox properties of the whole tetranitrocalix[4]arene.
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