No description available.

Betalaínas são alcalóides coloridos que atuam como mediadores químicos e sensores em processos de interesse tecnológico. Esta Tese de Doutorado investiga o comportamento de betalaínas naturais, betanina e indicaxantina, em três sistemas químicos diferentes. O primeiro capítulo discute a estabilidade de emulsões água-óleo-água contendo betanina. As emulsões foram preparadas em um sistema de microcanais empregando-se óleo de soja e tensoativos grau alimentício. Betanina pura tende a estabilizar a emulsão em relação ao controle sem o pigmento, enquanto suco de beterraba liofilizado e betanina comercial diluída com maltodextrina não mostram a mesma atividade. No capítulo seguinte, a interação entre indicaxantina e cloreto de 7-metil-4-metóxiflavílio revela a ocorrência de transferência de energia e dados de espectroscopia de 1H-RMN indicam a formação de um complexo no estado fundamental. Finalmente, a interação entre betanina e paraquat na presença e ausência de luz e oxigênio é investigada. Dados de espectroscopia de 1H-RMN sugerem a formação de um complexo entre as espécies e o estudo cinético sugere que betanina interfere na regeneração da forma oxidada do paraquat por oxigênio. / Betalains are colored alkaloids that act as chemical mediators and sensors in processes of technological interest. This doctoral thesis investigates the behavior of natural betalains, betanin and indicaxanthin, in three different chemical systems. The first chapter discusses the stability of water-oil-water emulsions containing betanin. The emulsions were prepared in a microchannel system using soybean oil and food grade surfactants. Pure betanin tends to stabilize the emulsion relative to the control without the pigment, while freeze-dried beet juice and commercial betanin diluted with dextrin do not show the same activity. In the following chapter, the interaction between indicaxanthin and 7-methyl-4-methoxyflavylium chloride reveals the occurrence of energy transfer and 1H-NMR spectroscopy data suggests the formation of a complex in the ground state. Finally, the interaction between betanin and paraquat in the presence and absence of light and oxygen is investigated. 1H-NMR spectroscopy data suggest the formation of a complex between species and the kinetic study suggests that betanin interferes in the regeneration of the oxidized form of paraquat by oxygen

Betalaínas são alcalóides coloridos que atuam como mediadores químicos e sensores em processos de interesse tecnológico. Esta Tese de Doutorado investiga o comportamento de betalaínas naturais, betanina e indicaxantina, em três sistemas químicos diferentes. O primeiro capítulo discute a estabilidade de emulsões água-óleo-água contendo betanina. As emulsões foram preparadas em um sistema de microcanais empregando-se óleo de soja e tensoativos grau alimentício. Betanina pura tende a estabilizar a emulsão em relação ao controle sem o pigmento, enquanto suco de beterraba liofilizado e betanina comercial diluída com maltodextrina não mostram a mesma atividade. No capítulo seguinte, a interação entre indicaxantina e cloreto de 7-metil-4-metóxiflavílio revela a ocorrência de transferência de energia e dados de espectroscopia de 1H-RMN indicam a formação de um complexo no estado fundamental. Finalmente, a interação entre betanina e paraquat na presença e ausência de luz e oxigênio é investigada. Dados de espectroscopia de 1H-RMN sugerem a formação de um complexo entre as espécies e o estudo cinético sugere que betanina interfere na regeneração da forma oxidada do paraquat por oxigênio. / Betalains are colored alkaloids that act as chemical mediators and sensors in processes of technological interest. This doctoral thesis investigates the behavior of natural betalains, betanin and indicaxanthin, in three different chemical systems. The first chapter discusses the stability of water-oil-water emulsions containing betanin. The emulsions were prepared in a microchannel system using soybean oil and food grade surfactants. Pure betanin tends to stabilize the emulsion relative to the control without the pigment, while freeze-dried beet juice and commercial betanin diluted with dextrin do not show the same activity. In the following chapter, the interaction between indicaxanthin and 7-methyl-4-methoxyflavylium chloride reveals the occurrence of energy transfer and 1H-NMR spectroscopy data suggests the formation of a complex in the ground state. Finally, the interaction between betanin and paraquat in the presence and absence of light and oxygen is investigated. 1H-NMR spectroscopy data suggest the formation of a complex between species and the kinetic study suggests that betanin interferes in the regeneration of the oxidized form of paraquat by oxygen

Abstract Methyl Viologen is a kind of organic molecular magnet of current interest which comprises with organic radicals (unpaired electrons). The molecular formula of the sample is (C12H14N2)2+X2-, where ¡§X2-¡¨ denotes a non-magnetic anion (CdI42-, I3-I- etc.). We perform the magnetization (using SQUID magnetometer) and electron paramagnetic resonance (EPR) measurements. Two absorption peaks are observed in EPR spectrum indicating that there are two radical forms in our samples. One of the radicals exists in every sample having the g1-factor value 2.004. The other radical which has the g2-factor 2.001 exists only in certain samples. Interestingly, we find that these samples exhibit ferromagnetism at room temperature. We use Lorentzian profile to quantitatively analyze the EPR spectrum of the samples and derive the ratio (A2/A1) of two different absorption peaks, which represents the amount of g2 radical. The remanent magnetization and saturation magnetization are found to increase as the ratio value increases, indicating that the strength of ferromagnetism is strongly correlated with g2 radical.

This thesis describes the host-guest chemistry between Cucurbit[7]uril (CB[7]) and CB[8] and a series of guests including bispyridinium cations, phenols and  napthalenes. These guests are bound to ruthenium polypyridine complexes or ruthenium based water oxidation catalysts (WOCs). The investigations are based upon utilizing the covalently linked photosensitizer and the electronic effects and chemical processes are investigated. / QC 20100927

No description available.

L’objectif de la thèse vise au développement d’architectures moléculaires et supramoléculaires commutables par contrôle rédox. La stratégie proposée repose sur l’exploitation du processus de π-dimérisation subi par les radicaux cations de dérivés du viologène comme force motrice pour la génération électro-induite de mouvements intramoléculaires. Nous décrivons la conception de nouvelles charnières organiques à squelette calixarène permettant d’accéder à des pinces moléculaires. Convenablement fonctionnalisée par des mâchoires de type pyridine-pyridinium, le mouvement de la pince est déclenché par la combinaison d’une activation chimique et électrochimique. Dans un deuxième exemple, nous montrons comment il est possible de verrouiller et déverrouiller les mouvements de la charnière calixarène en utilisant un réseau de liaisons hydrogène intramoléculaires. Nous décrivons également la conception d’une charnière inorganique originale fondée sur un complexe de palladium qui joue le rôle du pivot d’un carrousel moléculaire dont les bras à base de viologène sont mis en rotation sous l’effet d’une réduction électrochimique centrée sur les motifs viologènes. Le contrôle rédox des phénomènes d’auto-association au sein de polymères de coordination dynamiques est également abordé au travers de deux exemples de pinces moléculaires aux mâchoires fonctionnalisées soit par des briques auto-complémentaires, soit par des ligands bidentés. Dans un dernier exemple, un centre métallique palladium est utilisé à la fois comme vecteur de polymérisation et comme charnière pour la π-dimérisation intramoléculaire de ligands ditopiques à base de viologènes. / The aim of the thesis is to develop new concepts in the design of redox-switchable molecular and supramolecular architectures. The strategies which have been implemented rely on the π-dimerization of viologen radical cations as a driving force for the generation of electron-triggered intramolecular movements. Upon studying a series of viologen-appended calixarenes, we have established that bipyridinium radicals can be reversibly -dimerized under the joined effects of chemical (proton transfer) and electrochemical (electron transfer) stimulus. Our investigations also led to the discovery that a bis-pyridinyl appended calixarene intermediate is involved in a fully reversible redox-triggered sigma-dimerization process. We have also established that the ability of a phenol-containing calixarene to dimerize in its two electron reduced state depends on a subtle balance of weak interactions associated with hydrogen bond formation on the lower rim and orbital overlap between -radicals on the upper rim.We also demonstrate that inorganic hinges based on palladium complexes can be used as pivots in viologen-containing π-dimerizable architectures. The redox-controlled self-assemby of dynamic coordination polymers is also addressed through two examples of molecular tweezers, whose arms are functionalized by self-complementary complexing units or by bidentate ligands. In a last example, a palladium metal center is used both as a carrier of polymerization and as a hinge enabling the intramolecular π-dimerization of ditopic viologen-based ligands.

In dieser Arbeit wird ein neuer Ansatz beschrieben, elektroaktive Verbindungen auf mesoporösen Elektroden zu fixieren. Dies wurde durch die Bildung eines sich selbst organisierenden Monolayers auf der Innenseite eines mesoporösen Trägers (ITO, FTO, ATO, TiO2) erreicht. Dieser Layer wurde dann vernetzt und in Richtung des Porenzentrums weiter aufgebaut durch Substitutions- Kondensations- oder Elektropolymerisations- Reaktionen. Es wurde ein Vernetzungsverfahren entwickelt, welches die Herstellung stabiler elektrochromer Bilder mit verbessertem Kontrast und einer Haltbarkeit von mehr als 18 Monaten erlaubt. Es beinhaltet die Synthesen von molekularen Einheiten mit latent vorhandenen oder voll entwickelten elektrochromen Eigenschaften. Diese Einheiten waren 4,4´- Bipyridine, die entweder mit optionalen N-Alkyl, N-Benzyl oder N-Phenyl Gruppen mit nukleophilem oder elektrophilen Eigenschaften oder mit TiO2 Ankergruppen versehen waren. Die Kaskadenreaktion ergab Elektroden mit unterschiedlichen Oberflächenkonzentrationen und unterschiedlichen Pimerisationsgraden. Darüber hinaus gelang es, die Haltbarkeit und den Kontrast so weit zu steigern, dass sie kommerziellen Ansprüchen genügen. Die Optimierung der Gegenelektroden wurde durch ein ähnliches Verfahren unter Verwendung von Ferrocen- Derivaten erreicht. Die Ladungskapazitäten, die durch Multilayer Vernetzung auf ATO-Ferrocen Elektroden erhalten wurden, waren hervorragend mit Ausnahme der Tatsache dass ein schwach grüner Farbton, verursacht durch oxidiertes Ferrocen, vorhanden war. Schließlich wurde die Kaskadenreaktion auf B12 Derivate zur Herstellung von katalytisch aktiven TiO2 Elektroden angewandt. Die mit B12 modifizierten Elektroden zeigten verbesserte Stabilität, höhere turn over - Zahlen und größere turn over -Raten im Vergleich zu unvernetzten B12 modifizierten Elektroden.

The main subject of this thesis is the synthesis and investigation of the properties and potential applications of a new class of hybrid compounds consisting of a rigid, electroactive 4,4’-bipyridinium core capped by nucleobase terminal groups with hydrogen bonding abilities. A new series of small molecules consisting in a 4,4’-bipyridinium unit carrying thymine or/and adenine as capping groups was synthetized. The synthesis strategy implied the regioselective alkylation of thymine and adenine bases respectively, followed by coupling of the alkylated precursors to 4,4’-bipyridine unit via Menschutkin reaction. Electrochemical, spectroelectrochemical and optical investigations revealed an intramolecular charge transfer (CT) relationship between nucleobases as donors and 4,4’-bipyridinium unit as acceptor which is accompanied by a change in color and a shift of the reduction potentials (approx. 60 mV). The viologen-nucleobase derivatives, particularly viologens capped by thymine, were used as building blocks to create self-assembled functional nanostructures in the presence of complementary templates such as oligonucleotides or ssPNA analogues via thymine-adenine interactions. The viologen-thymine derivatives were found to partially precipitate oligonucleotides or plasmid DNA by mean of coulombic interactions and form stable polyplexes that could be used as potential gene delivery vectors. It was found that the number of positive charges, as well as the number of thymine units per viologen-thymine derivative determines whether the interaction with DNA is dominated by electrostatic or by hydrogen bonding interactions. New electroactive ionic liquid crystals were prepared by ion pairing of viologen-nucleobase dicationic species with amphiphilic 3,4,5-tris(dodecyloxy)benzene sulfonate anion. The nucleobases with ability to self-associate by hydrogen bonding were found to influence not just the thermotropic behavior, by decreasing transition temperature from crystalline to mesophase state, but also the supramolecular arrangement in solution. A versatile approach to functionalize mesoporous TiO2 film with viologen-nucleobase derivatives was developed consisting of hydrogen bonding layer-by-layer deposition of viologen-nucleobase derivatives on TiO2 surface using the thymine-adenine molecular recognition as driving force for immobilization. This method is promising and represents an easy way to construct optoelectronic device components as was demonstrated with the construction of a switchable electrochromic device.

In der vorliegenden Arbeit wird erstmals ein transparentes elektrochromes Display (ECD) höchster Auflösung (720 dpi) beschrieben. Die Entwicklung erforderte grundlegende Arbeiten an den einzelnen Komponenten, insbesondere (i) an der Arbeitselektrode und (ii) an der Gegenelektrode.Die Arbeitselektrode des ECD enthält ein digital festgelegtes elektrochromes Bild, welches mit Hilfe der Ink-Jet-Technik nach verschiedenen Methoden übertragen wurde. Der Druck eines Bildpositivs mit elektrochromer Tinte (Viologen) auf eine mit mesoporösem TiO2 beschichtete Glaselektrode lieferte dabei die besten Ergebnisse. Mit verschiedenen Elektrochromophoren konnten Mehrfarbendrucke erzeugt werden. Als Problem trat dabei auf, daß das Bild in einem ECD nach vier Monaten Lagerung unscharf wird. Die Lösung bestand darin, einen Viologenvorläufer zu drucken, der in einer anschließenden kaskadenartigen Synthese quervernetzt wurde. Zur weiteren Optimierung der Parameter (i) berflächenkonzentration der Viologenzentren, (ii) Stabilität gegenüber polaren Lösemitteln und (iii) Pimerisierungsgrad, wurden erstmals auch kombinatorische Experimente mit einem Ink-Jet Drucker durchgeführt. Ein weiteres Thema dieser Arbeit ist die Entwicklung transparenter Gegenelektroden, welche auf dem Prinzip der Lithiumioneninterkalation in CeO2 basieren. Dazu wurde ein bereits bekannter Typ von CeO2-TiO2-Mischoxidelektroden weiterentwickelt. Ein in dieser Arbeit neu entwickelter Typ einer Gegenelektrode mit verbesserter Kinetik besteht aus einem Zweiphasenoxidgemisch, mit CeO2 auf der inneren Oberfläche einer mesoporösen, antimondotierten SnO2-Schicht (ATO). Aus den Einzelkomponenten wurden verschiedene ECDs zusammengesetzt.