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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
211

Efeitos cotton nas enzimas piridínicas e compostos relacionados / Cotton effects on pyridinium coenzymes and related compounds

Faljoni-Alario, Adelaide 15 October 1976 (has links)
O produto de redução da nicotinamida adenina dinucleotídio (NADH) foi convertido no seu derivado hidratado NADH-X (6-hidroxi-l,4,5,6-tetraidronicotinamida adenina dinucleotídio) por ação de íons polibásicos tais como: fosfato, arsenato etc, ou por ação enzimática da gliceraldeído-3-fosfato desidrogenase (GPD). A cinética da hidratação foi acompanhada pelo aumento de absorbância (ΔA285 nm) e o aparecimento de um efeito Cotton a 285 nm , notando-se que quando se parte do anômero β da coenzima, o efeito Cotton positivo só se desenvolve nos estágios finais da reação na presença de enzima. Com base nesses resultados postulou-se a formação de um intermediário que se transforma num produto final, o qual mostra um efeito Cotton positivo a 285 nm. Supõe-se que essa última transformação seja uma epimerização β→α, de maneira que a adição de água não afeta inicialmente a configuração do átomo C1, da ribose. Contudo, após a hidratação, o produto se transforma no epímero α, que é termodinamicamente mais estável. Na ausência da enzima, o efeito Cotton aparece em estágios anteriores, sugerindo que a hidratação, sendo lenta, dá oportunidade à epimerização. Consequentemente não há tanto acúmulo deste intermediário, que apresenta efeito Cotton praticamente nulo. A hidratação do anômero α-NADH, na presença de GDP, mostrou um aumento de absorbância a 285 nm mais rápido do que para a forma β. Por outro lado, o efeito Cotton positivo só começou a aparecer após desenvolvimento de 60% do ΔA285 nm. Isto indicou que também para α-NADH há formação de um intermediário, o qual apresenta um efeito Cotton nulo. Quando β-NADH foi hidratado na ausência da enzima, observou-se um comportamento semelhante, porém, menos marcante com relação ao aparecimento do efeito Cotton. O fato de GPD e íons polibásicos produzirem efeitos semelhantes sobre os anômeros α e β, sugere que a ação enzimática da GPD não é estereoespecífica, produzindo uma mistura de epímeros em C6. Explica, também, o efeito Cotton nulo quando já se tem grande parte da hidratação efetuada. Desta maneira pôde-se afirmar (i) que o intermediário é uma mistura de epímeros em C6; (ii) que com o tempo predomina o epímero termodinamicamente mais estável. Os mesmos estudos foram desenvolvidos com NADPH, desamino-NADH e NMNH, para esclarecimentos a respeito da influência de grupos fosfato, amino e açúcar na catálise da hidratação e dos centros responsáveis pelo efeito Cotton positivo a 285 nm, nos piridinos nucleotídios. Observou-se que NADPH tem comportamento semelhante ao β-NADH, indicando que o grupo fosfato não tem papel importante nas catálises química e enzimática. No caso do mononucleotídio e desamino-dinucleotídio não houve diferença significativa entre as velocidades de hidratação química e enzimática, o que siginifica ser importante a presença do amino grupo da adenina para catálise enzimática no caso de NADH. Os derivados acima, também, apresentaram efeito Cotton positivo nos estágios finais da reação. Com base no fato, que o mononucleotídio também apresentou efeito Cotton positivo, de mesma intensidade dos dinucleotídios, pôde-se afirmar que o açúcar ligado ao anel da nicotinamida é o responsável pela dissimetria do produto formado. Traçou-se o espectro de absorção circular dicróica do isômero 1,6-NADH, ainda desconhecido, para obter-se informações a respeito da sua estrutura. Através dos valores de elipticidades molares, concluiu-se que é mais rígida do que a do 1,4-NADH, presumivelmente, devido a ligação simples, que une os anéis piridínico e ribosídico, ter rotação mais impedida, como consequência da maior proximidade do par de hidrogênios da piridina, com a ribose. O estudo da adição de CN- aos piridinos nucleotídios e compostos relacionados, usando técnica de dicroismo circular, mostrou haver estereosseletividade na adição. O espectro de absorção circular dicróica do aduto β-NAD+/CN- mostrou uma banda negativa larga com máximo em torno de 330 nm. Esta banda é assimétrica, o que permite um desdobramento em outras duas, com máximos a 325 e a 345 nm, de intensidade semelhantes. Em analogia com a redução dos piridinos nucleotídios, que ocorre nas posições 2, 4 e 6, pôde-se afirmar que a adição de CN-, também, ocorre em outras posições e não exclusivamente em 4. A banda de dicroismo circular na região de 345 nm, pareceu indicar a presença do isômero 1,6. O fato deste estar em concentração baixa a ponto de não ser detectável espectrofotometricamente, indicou que a força rotacional é bem maior do que para o isômero 1,4. Tal fato deve estar relacionado com a maior proximidade do CN- ao anel carboidrático. No aduto da forma α do piridino nucleotídio, o espectro de dicroismo circular apresentou uma banda negativa, com máximo de 342 nm e uma inflexão a 325 nm. Essa assimetria mostrou, claramente, a existência dos dois isômeros e, que a adição de CN- em C6 é bastante estereosseletiva. Além da estereosseletividade, pode estar contribuindo, também a menor mobilidade rotacional do anel diidronicotinamídico, quando se tem aduto em C6. A estereosseletividade da adição de cianeto veio corroborar com a proposição de um equilíbrio rápido entre as conformações aberta e fechada para os piridino nucleotídios. A possível existência de uma transição fraca, associada ao núcleo diidronicotinamídico, foi confirmada detectando-se um efeito Cotton associado a ela. Esse efeito foi observado para α-NADH, β-NADH e seus correspondentes adutos de CN-. Realizando-se o mesmo estudo para o complexo de β-NADH.Cu++, verificou-se que o efeito Cotton é 15 vezes mais intenso, confirmando assim, a detecção pioneira dessa transição fraca, presumivelmente de natureza singlete-triplete. / The reduction product of nicotinamide adenine dinucleotide (NADH) is converted into the hydration product NADH-X (6-hydroxy-1,4,5,6-tetrahydronicotinamide adenine dinucleotide) by the action of polybasic ions such as phosphate, arsenate etc., or by enzymatic catalysis with glyceraldehyde-3-phosphate dehydrogenase (GPD). The hydration kinetics were followed by the increase in absorbance at 285 nm. Starting with the β-anomer of the coenzyme, the transition at 285 nm begins to exhibit a positive Cotton effect only in the later stages of the reaction. On the basis of the results, the formation of an interrnediate not exhibiting a Cotton effect at 285 nm is postulated. Since the hydration would not be expected to change the configuration at C1, of the ribose, the appearance of the Cotton effect is presumably due to an epimerization from the β-epimer to the thermodynamically more stabe α-epimer. In the absence of enzyme, the Cotton effect appears at somewhat lower conversions, suggesting that the slower hydration reaction provides greater opportunity for the occurrence of the epimerization. The increase in absorbance at 285 nm is more rapid for the hydration of the α-anomer of NADH than for the β-form in the presence of GPD. A positive Cotton effect is only observed for the forrner after the reaction has gone to about 60% completion. This indicates that an intermediate not exhibiting a Cotton effect is also formed in the case of α-NADH. Similar behavior was observed in the non-enzymatic hydration, however, as in the case of β-NADH, the onset of the Cotton effect occurred at lower conversions. The fact that GPD and polybasic ions produce similar effects on both the α and β anomers suggests that the enzymatic action of GPD is non-stereospecific, producing a mixture of epimers at C6. This also explain the absence of a Cotton effect even though significant hydrations has occurred. Thus we conclude (i) that the intermediate is a mixture of C6 epimers and (ii) that the more thermodynamically stable epimer predominates at long reaction times. The same studies were carried out with NADPH, deamino-NADH and NMNH to clarify the catalytic influence of the phosphate, amino, and sugar groups on the hydration and to identify the centers responsible for the positive Cotton effect at 285 nm in pyridine nucleotides. The observation that the behavior of NADPH is similar to that of β-NADH indicates that the phosphate group does not play an important role in the chemical and enzymatic catalysis. In the case of NMNH and deamino-NADH there is no significant difference between the rates of the chemical and enzymatic hydration, which implies that the presence of the amino group of adenine is important in the enzymatic catalysis of the hydration of NADH. The above derivatives also present positive Cotton effects in the later stages of the reaction. Since that mononucleotide exhibits a positive Cotton effect of intensity equal to that of the dinucleotides, it can be concluded that the sugar attached to the nicotinamide ring is responsible for the assymetry of the product. The previously unknown circular dichroic absorption spectrum of 1,6-NADH was determined in order to gain insight into its structure. From the values of the molar ellipticity it is concluded that the assymetric center of 1,6-NADH is more rigid than that of. 1,4-NADH. This is presumably due to a greater hindrance to rotation about the single bond between the pyridine and ribose rings in 1,6-NADH. A circular dichroic study of the addition of CN- to pyridine nucleotides and related compounds demonstrated the stereoselectivity of the addition. The circular dichroic absorption spectrum of the B-NAD+/CN- adduct exhibits a broad assymetric negative band with a maximum at about 330 nm. This band was interpreted in terms of two bands of similar intensity with maxima at 325 and 345 nm. By analogy with the reduction of pyridine nucleotides,which occurs at position 2,4 and 6, it is concluded that CN- addition also occurs at positions other than C4. The band at 345 nm was attributed to the 1,6-isomer. The fact that this isomer could not be detected by conventional absorption techniques indicates that it is present in low concentrations relative to the 1,4-isomer. It must have therefore has a much greater rotational strength, which is reasonable in view of the proximity of the CN- to the carbohydrate ring. The circular dichroic absorption spectrum of the α-NAD+/CN- adduct exhibited a negative band with a maximum at 342 nm and an inflection at 325 nm. This assymetry clearly demonstrated the presence of two isomers and the stereoselectivity of CN- addition at C6. Although the l,6-adduct could not be detected by conventional absorption techniques, the stereoselectivity of the addition and a large rotational strength contribute to its circular dichroic intensity. The stereoselectivity of the CN- addition corroborates the existence of a rapid conformational equilibrium between the folded and unfolded forms of pyridine nucleotides. A Cotton effect associated with the weak electronic transition attributed to the dihydronicotinamide nucleus was observed for α-NADH, β-NADH, and the corresponding CN- adducts, confirming the existence of the transition. For the β-NADH.CU++ complex, the Cotton effect was found to be 15 times more intense, thus confirming the original detection of this weak transition, which presumably has singlet-triplet character.
212

Ancoragem covalente de piridina à matriz polimérica do filme poli-(fenol-azo-benzeno). Preparação de eletrodos modificados com propriedades oxidantes de substratos orgânicos / Pyridine anchored to polymeric film poly-(phenol-azo-benzene). Preparation of modified electrodes with oxidants proprieties of organic substrates.

Steter, Juliana Ribeiro 16 May 2008 (has links)
Neste trabalho os complexos cis- [Ru(BAF)(bpy)(PPh3)(OH2)](ClO4)2 (monômero B) e cis-[Ru(dmbpy)2(PPh3)(OH2)](OPh)2 (monômero C) foram sintetizados e caracterizados através de métodos espectroscópicos e eletroquímicos, sendo utilizados na construção de novos eletrodos modificados EMs e aplicados na eletrooxidação de substratos orgânicos. A preparação destes EMs consistiu no recobrimento da superfície de eletrodos de feltro de carbono e de bastões de grafite pelos filmes poliméricos ancorados ao rutênio. Os intervalos de potencial aplicados para a polimerização dos complexos foram àqueles correspondentes, respectivamente, aos potenciais de polimerização do contra-íon difenolato e do ligante azóico contendo o grupamento fenol. A atividade catalítica destes EMs foi investigada através de um estudo cinético, através de eletrooxidações heterogêneas acompanhadas por UV/Vis de diversos compostos orgânicos como: safrol, isosafrol, álcool benzílico, fenil etil álcool, etil benzeno, tolueno, benzaldeído, ciclo hexen-2-ol, demonstrando que os EMs podem ser utilizados como catalisadores em reações de eletrooxidações com rendimentos satisfatórios. / In this work the complexes cis-[Ru(BAF)(bpy)(PPh3)(OH2)](ClO4)2 (B monomer) and cis-[Ru(dmbpy)2(PPh3)(OH2)](OPh)2 (C monomer) were synthesized and characterized by spectroscopic and electrochemical methods, and they were utilized in construction of new modified electrodes (MEs) and applied in electrooxidation of organic substrates. The preparation of these new MEs was done by coating the surfaces of carbon felt and carbon rod electrodes by polymeric films where the ruthenium complexes were anchored. The potential range applied to accomplish the polimerization of the complexes corresponds to the potencial ranges of diphenol anion and azoic ligand with the phenolic group, respectively. The catalytic activity of these MEs was studied by kinetic methodology monitoring the heterogeneous electroxidations by UV/Vis of some organic substrates like: safrol, isosafrol, benzylic alcohol, phenil ethyl alcohol, ethyl benzene, toluene, cycle-hexen-2-ol, showing that these EMs can be utilized as catalyst in electrooxidations reactions with goods yields.
213

Synthesis of β-turn and pyridine based peptidomimetics

Blomberg, David January 2007 (has links)
Despite the unfavorable pharmacokinetic properties associated with peptides, they are still of great interest in drug development due to a multitude of interesting biological functions. The development of peptidomimetics strives to maintain or improve the biological activity of a peptide concurrently with removing the unwanted properties. This thesis describes two synthetic approaches to peptidomimetics with particular emphasis on secondary structure mimetics. First the design, synthesis and evaluation of two beta-turn mimetics incorporated in the endorphin Leu-enkephalin is presented. The beta-turn mimetics were stabilized by replacement of the intramolecular hydrogen bond with an ethylene bridge, and the amide bond between Tyr and Gly was replaced with an ether linkage. Linear analogues of the two mimetics were also synthesized. The peptidomimetics and their linear analogues were evaluated in a competitive binding assay at two opiate receptors, my and delta. One of the cyclized beta-turn mimetics was found to be a delta receptor antagonist with an IC50 value of 160 nM. Second a synthetic strategy to a beta-strand mimetic using 2-fluoro-4-iodopyridine as scaffold is described. The synthesis involved a Grignard exchange reaction on the pyridine scaffold using an amino acid derivative as electrophile followed by an SNAr reaction using an amine as nucleophile. The synthesis of a tripeptidomimetic of Leu-Gly-Gly and attempts to introduce chiral building blocks at the C-terminal, as well as studies towards elongated mimetics are presented. Two additional studies deal with the synthesis of two classes of potential thrombin inhibitors based on the pyridine scaffold. The first class contain pyridine as central fragment (P2 residue) substituted with a para-amidinobenzylamine group as P1 residue and various benzoyl groups as P3 residues. Three potential thrombin inhibitors were synthesized and found to be microM inhibitors in an enzymatic assay. In the second class, the pyridine ring serves as P3 residue. This class also lacks a strongly basic group in the P1 position. A small library of eight compounds were synthesized and evaluated in the enzymatic assay. Unfortunately, these compounds lacked inhibitory activity.
214

Computational Investigation of Dye-Sensitized Solar Cells

Nilsing, Mattias January 2007 (has links)
Interfaces between semiconductors and adsorbed molecules form a central area of research in surface science, occurring in many different contexts. One such application is the so-called Dye-Sensitized Solar Cell (DSSC) where the nanostructured dye-semiconductor interface is of special interest, as this is where the most important ultrafast electron transfer process takes place. In this thesis, structural and electronic aspects of these interfaces have been studied theoretically using quantum chemical computations applied to realistic dye-semiconductor systems. Periodic boundary conditions and large cluster models have been employed together with hybrid HF-DFT functionals in the modeling of nanostructured titanium dioxide. A study of the adsorption of a pyridine molecule via phosphonic and carboxylic acid anchor groups to an anatase (101) surface showed that the choice of anchor group affects the strength of the bindings as well as the electronic interaction at the dye-TiO2 interface. The calculated interfacial electronic coupling was found to be stronger for carboxylic acid than for phosphonic acid, while phosphonic acid binds significantly stronger than carboxylic acid to the TiO2 surface. Atomistic and electronic structure of realistic dye-semiconductor interfaces were reported for RuII-bis-terpyridine dyes on a large anatase TiO2 cluster and perylene dyes on a periodic rutile (110) TiO2 surface. The results show strong influence of anchor and inserted spacer groups on adsorption and electronic properties. Also in these cases, the phosphonic acid anchor group was found to bind the dyes significantly stronger to the surface than the carboxylic acid anchor, while the interfacial electronic coupling was stronger for the carboxylic anchor. The estimated electron injection times were twice as fast for the carboxylic anchor compared to the phosphonic anchor. Moreover, the electronic coupling was affected by the choice of spacer group, where unsaturated spacer groups were found to mediate electron transfer more efficiently than saturated ones.
215

Effets fonctionnels de la stimulation électrique du cortex moteur dans un modèle primate de la maladie de Parkinson

Drouot, Xavier Palfi, Stéphane January 2007 (has links) (PDF)
Thèse de doctorat : Neurosciences : Paris 12 : 2005. / Thèse électronique uniquement consultable au sein de l'Université Paris 12 (Intranet). Titre provenant de l'écran-titre. Bibliogr. f. 189-216.
216

Étude de catalyseurs à base d'oxyde de titane et d'oxyde de vanadium sulfatés pour l'oxydation sélective du méthanol en diméthoxyméthane (DMM)

Zhao, Hongying 28 June 2010 (has links) (PDF)
Ce travail est en relation avec la thématique "Energies Propres". Le diméthoxyméthane estun composé adapté au stockage de l'hydrogène pour des applications mobiles, de par saforte teneur en hydrogène, sa très faible toxicité et son faible impact sur l'environnement.De ce fait, des catalyseurs mixtes, à base d'oxyde de vanadium et d'oxyde de titanesulfatés ont été préparés et testés dans la réaction d'oxydation sélective du méthanol enDMM, en vue de la production d'hydrogène. Les propriétés acides et redox de surface ontété corrélées aux performances catalytiques. Les mécanismes de réaction et l'identificationdes facteurs limitant l'activité et la sélectivité des catalyseurs ont été aussi étudiés.
217

Formation and inhibition of the heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in a model system

Kelly, Elizabeth A. January 1900 (has links)
Master of Science / Food Science - Animal Sciences and Industry / J. Scott Smith / Heterocyclic amines (HCAs) are a class of mutagenic and carcinogenic chemical compounds formed on the outside of meat and fish when cooked at high temperatures. 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most abundantly formed HCA. HCAs have been found to cause cancer in mice and rats; PhIP specifically has been found to cause breast, rectal, prostate, and colon cancers. Model systems are often used to replicate the HCA chemical reactions in meat products without causing the many side reactions when meat is cooked at high temperatures. Model systems are also a useful way to study the effects of different variables and compounds on the formation of HCAs without using meat. A model system using amounts of 0.2 mmol glucose, 0.4 mmol creatinine, and 0.4 mmol phenylalanine in 10:90 water/diethylene glycol (v/v) was used to study the formation of PhIP. Differing levels of black pepper oil, black pepper extract, and rosemary extract (36, 71, 142, 285, 550 μL), synthetic antioxidants BHT and TBHQ (0.05 mmol, 0.1 mmol, 0.2 mmol, 0.4 mmol), and piperine (4.02 mg, 8.04 mg, 16.14 mg, 31.14 mg) were added to the model system to study their effect on PhIP formation. PhIP formation with added BHT (0.2 and 0.4 mmol) and TBHQ (0.4 mmol) were not significantly different from the control. All other added compounds decreased PhIP formation significantly from the control at p < 0.05. Solid phase micro extraction (SPME) headspace analysis was conducted on ground black pepper, black pepper oil, and black pepper extract to determine possible components responsible for PhIP inhibition. Six volatile compounds were found in common between ground black pepper, black pepper oil, and black pepper extract: 1R-α-pinene, 3-carene, caryophyllene, α-caryophyllene, cyclohexene, and D-limonene. D-limonene and caryophyllene had the largest peak areas, suggesting those compounds may play a part in PhIP inhibition in model systems.
218

Síntese e caracterização espectroscópica de complexos tris -dicetonatos do íon európio com ligantes 2-(n-acil)-piridina

Jesus, Jacqueline Cristina Bueno Janice de 20 June 2014 (has links)
Made available in DSpace on 2015-05-14T13:21:40Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2137261 bytes, checksum: 13b9e74375fe86c1b2772dad6188a007 (MD5) Previous issue date: 2014-06-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work, we propose a new class of complexes of trivalent europium ion derived from tetrakis-diketonates, by replacing the keto group of a ligand by the 2- aminopyridyl. For the synthesis of these complexes, the amides N-acetyl-2- aminopyridine and N-trifluoroacetyl-2-aminopyridine were prepared via acylation of 2- aminopyridine and their respective anhydrides. N-benzoyl-2-aminopyridine was synthesized by basic hydrolysis of N, N-dibenzoyl-2-aminopyridine. The ligands were characterized by mass spectrometry, melting point measurement and absorption spectroscopy in the infrared region. New compounds have been obtained, having the formulas [Eu(BZAC)3(NAC2AP)] and [Eu(TTA)3(NTF2AP)2]. These complexes were characterized by complexometric titration, CHN elemental analysis and infrared absorption spectroscopy. Through the results obtained by photoluminescence spectroscopy, the analysis of the split of the transitions 5D0 → 7FJ in emission spectra, leads to the inference that the Eu3+ ion in the complex [Eu(TTA)3(NTF2AP)2] is in a chemical environment of higher symmetry as compared to its precursor complex. Both complexes [Eu(BZAC)3(NAC2AP)] and [Eu(TTA)3(NTF2AP)2] showed quantum efficiencies higher than the corresponding aqua complex and tetrakisdiketonates. This result indicates that replacing the fragment R(CO)CH- of a ligand in the tetrakis-diketonate complex by an 2-aminopyridyl group is a good strategy to generate highly luminescent complexes. This strategy can be used in the development of efficient light conversion molecular devices such as those desirable for biomarkers. / No presente trabalho, foi proposta uma nova classe de complexos de íon európio trivalente derivados dos tetrakis-dicetonatos, por substituição do grupo ceto de um dos ligantes pelo grupo 2-aminopiridil. Para síntese desses complexos foram preparadas as amidas N-acetil-2-aminopiridina e N-trifluoroacetil-2-aminopiridina via acilação da 2-aminopiridina com seus respectivos anidridos. A N-benzoil-2- aminopiridina foi sintetizada através da hidrólise básica da N,N-dibenzoil-2- aminopiridina. Os ligantes sintetizados foram caracterizados por espectrometria de massas, determinação de ponto de fusão e espectroscopia de absorção na região do infravermelho. Foram obtidos complexos inéditos, cujas fórmulas são [Eu(BZAC)3(NAC2AP)] e [Eu(TTA)3(NTF2AP)2], caracterizados por titulação complexométrica, análises elementar de carbono, hidrogênio e nitrogênio, além de espectroscopia de absorção na região do infravermelho. Por meio dos resultados obtidos por espectroscopia de fotoluminescência, analisando os desdobramentos das transições 5D0→7FJ, nos espectros de emissão, pode-se inferir que o íon Eu3+ no complexo [Eu(TTA)3(NTF2AP)2] encontra-se em um ambiente químico de maior simetria se comparado ao seu aqua-complexo precursor. Ambos os complexos [Eu(BZAC)3(NAC2AP)] e [Eu(TTA)3(NTF2AP)2] apresentaram eficiências quânticas superiores aos correspondentes tris-dicetonatos aquosos e tetrakis-dicetonatos. Este resultado indica que a substituição do fragmento R(CO)CH- pelo grupo 2-aminopiridil de um dos ligantes dos complexos tetrakis-dicetonatos de Eu3+ seja uma boa estratégia para gerar complexos altamente luminescentes. Tal estratégia poderá ser utilizada no desenvolvimento de Dispositivos Moleculares Conversores de Luz eficientes, tais como os desejáveis para biomarcadores.
219

Ancoragem covalente de piridina à matriz polimérica do filme poli-(fenol-azo-benzeno). Preparação de eletrodos modificados com propriedades oxidantes de substratos orgânicos / Pyridine anchored to polymeric film poly-(phenol-azo-benzene). Preparation of modified electrodes with oxidants proprieties of organic substrates.

Juliana Ribeiro Steter 16 May 2008 (has links)
Neste trabalho os complexos cis- [Ru(BAF)(bpy)(PPh3)(OH2)](ClO4)2 (monômero B) e cis-[Ru(dmbpy)2(PPh3)(OH2)](OPh)2 (monômero C) foram sintetizados e caracterizados através de métodos espectroscópicos e eletroquímicos, sendo utilizados na construção de novos eletrodos modificados EMs e aplicados na eletrooxidação de substratos orgânicos. A preparação destes EMs consistiu no recobrimento da superfície de eletrodos de feltro de carbono e de bastões de grafite pelos filmes poliméricos ancorados ao rutênio. Os intervalos de potencial aplicados para a polimerização dos complexos foram àqueles correspondentes, respectivamente, aos potenciais de polimerização do contra-íon difenolato e do ligante azóico contendo o grupamento fenol. A atividade catalítica destes EMs foi investigada através de um estudo cinético, através de eletrooxidações heterogêneas acompanhadas por UV/Vis de diversos compostos orgânicos como: safrol, isosafrol, álcool benzílico, fenil etil álcool, etil benzeno, tolueno, benzaldeído, ciclo hexen-2-ol, demonstrando que os EMs podem ser utilizados como catalisadores em reações de eletrooxidações com rendimentos satisfatórios. / In this work the complexes cis-[Ru(BAF)(bpy)(PPh3)(OH2)](ClO4)2 (B monomer) and cis-[Ru(dmbpy)2(PPh3)(OH2)](OPh)2 (C monomer) were synthesized and characterized by spectroscopic and electrochemical methods, and they were utilized in construction of new modified electrodes (MEs) and applied in electrooxidation of organic substrates. The preparation of these new MEs was done by coating the surfaces of carbon felt and carbon rod electrodes by polymeric films where the ruthenium complexes were anchored. The potential range applied to accomplish the polimerization of the complexes corresponds to the potencial ranges of diphenol anion and azoic ligand with the phenolic group, respectively. The catalytic activity of these MEs was studied by kinetic methodology monitoring the heterogeneous electroxidations by UV/Vis of some organic substrates like: safrol, isosafrol, benzylic alcohol, phenil ethyl alcohol, ethyl benzene, toluene, cycle-hexen-2-ol, showing that these EMs can be utilized as catalyst in electrooxidations reactions with goods yields.
220

Organic Synthesis Based on Transition-Metal-Catalyzed Addition Reactions of Boron Reagents / 遷移金属触媒によるホウ素反応剤の付加反応に基づく有機合成

Oshima, Kazuyuki 26 March 2012 (has links)
Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16808号 / 工博第3529号 / 新制||工||1534(附属図書館) / 29483 / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 杉野目 道紀, 教授 村上 正浩, 教授 吉田 潤一 / 学位規則第4条第1項該当

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