SYNTHESIS AND CHARACTERIZATION OF SUBSTITUTED PORPHYRINES WITH POLYPHYRIDINE COMPOUNDS OF Ru (II). DESIGN OF MODIFIED ELECTRODES FOR THE ELECTROCATALYSIS OF CO2 AND NO2-, AND FOR THE ELECTRO ANALYSIS OF SULFUR OXOANIONS (IV)
Electrocatalytic methods have been developed to perform CO2 and NO2- reduction, either in a separate or simultaneous way. These methods are a novel alternative to deplete CO2 and NO2- concentration. On the other hand, electroanalytical techniques can develop methods able to determine sulfite in wine...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2011 |
| País: | Chile |
| OAI Identifier: | oai:repositorio.anid.cl:10533/220344 |
| Acceso en línea: | https://hdl.handle.net/10533/220344 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias Naturales Ciencias Químicas Electroquímica |
| Sumario: | Electrocatalytic methods have been developed to perform CO2 and NO2- reduction, either in a separate or simultaneous way. These methods are a novel alternative to deplete CO2 and NO2- concentration. On the other hand, electroanalytical techniques can develop methods able to determine sulfite in wines, which is of vital importance in the production of this beverage. Electrocatalytic and electroanalytical processes can be preformed with different catalysts, being macrocycles containing transitional metal interesting models because they are able to promote multiple electronic transfers. Consequently, is possible to develop the electrochemical reduction of contaminating agents and also to determinate different compounds like sulfite, with the use of metallic catalysts. In this Doctoral Thesis, new macrocycles were synthesized. These compounds consist of a tetrapyridylporphyrin coordinated to four Ru (II) complexes. The ligands of the Ru (II) complexes are 5-NO2-phenanthroline and the metals coordinated in the central cavity of the porphyrins are Ni (II) and Zn (II). A protocol for the electrochemical preparation of a conducting polymer from this macrocycle was also developed. The polymeric growth was characterized by cyclic voltammetry, IR spectroelectrochemistry, atomic force microscopy and Raman spectroscopy. Experimental results showed that the electropolymerization process takes place when nitro substituents are reduced. These polymeric films were evaluated in aqueous solution, and were very stable; therefore, these modified electrodes were used in the study of CO2 and NO2- electroreduction, and also for sulfite determinations. The electrochemical reduction of CO2 was studied with the polymeric catalysts and it was observed that the three coatings present catalytic activity for CO2 reduction. Controlled potential electrolysis experiments verify the production of formic acid and formaldehyde when polymeric metal free tetraruthenated porphyrin was used, and only formaldehyde when Ni (II) and Zn (II) macrocycles were used. Also, the nitrite electroreduction was studied, the results also evidenced that the three conductive polymers are active for nitrite reduction. Controlled potential electrolysis experiments verified the production of hydrazine, hydroxylamine and ammonia. All modified electrodes were more selective toward hidroxylamine production. The study of the simultaneous electrocatalytic reduction of CO2 and nitrite, showed that these conductive polymers films promote the formation of urea at -1,0 V. Finally, the conductive polymers of tetraruthenated porphyrins were evaluated in the electroanalysis of S (IV) oxoanions. The Ni (II) film was the most effective coating for sulfite determination. Two potential analytical methods were proposed one at pH 1,0 for sulfite reduction and other at pH 3,5 for sulfite oxidation, both methodologies present limits of detection comparable with current analytical methods. |
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