Auswahl der wissenschaftlichen Literatur zum Thema „Cbpqt4+“

Two dumbbell-shaped components with tetraarylmethane-type stoppers - one hydrophobic and one hydrophilic - and a rod-like section containing a tetrathiafulvalene (TTF) unit and a 1,5-dioxynaphthalene (DNP) moiety as electron-donating units, and their [2]rotaxanes, incorporating the cyclobis(paraquat-p-phenylene) (CBPQT4+) cyclophane as their electron-accepting ring component, have been synthesized, the latter using template-directed protocols. The two amphiphilic [2]rotaxanes, which differ from each other only in the lengths of the polyether chains associated with their hydrophilic stoppers, were designed in order (i) to have them exhibit enhanced amphiphilicities and, by altering the lengths of polyether chains, (ii) to improve the qualities of their Langmuir-Blodgett films, and by removing the phenolic residues, (iii) to increase the oxidative stabilities of these switchable molecules, and so extend the lifetimes of electronic devices fabricated from amphiphilic hysteretic molecular switches of this type. UV-VIS absorption and 1H NMR spectra, as well as electrochemical measurements, show that both [2]rotaxanes exist to all intents and purposes in solution as the translational isomer in which the CBPQT4+ cyclophane surrounds the TTF unit. Evidence has also been obtained for the presence in solution of folded conformations of these [2]rotaxanes. While ox/red stimulation of the TTF unit causes shuttling of the CBPQT4+ cyclophane between the TTF and DNP stations, reduction of CBPQT4+ causes unfolding of the [2]rotaxane molecules.

AbstractMacroscopic electric motors continue to have a large impact on almost every aspect of modern society. Consequently, the effort towards developing molecular motors1–3 that can be driven by electricity could not be more timely. Here we describe an electric molecular motor based on a [3]catenane4,5, in which two cyclobis(paraquat-p-phenylene)6 (CBPQT4+) rings are powered by electricity in solution to circumrotate unidirectionally around a 50-membered loop. The constitution of the loop ensures that both rings undergo highly (85%) unidirectional movement under the guidance of a flashing energy ratchet7,8, whereas the interactions between the two rings give rise to a two-dimensional potential energy surface (PES) similar to that shown by FOF1 ATP synthase9. The unidirectionality is powered by an oscillating10 voltage11,12 or external modulation of the redox potential13. Initially, we focused our attention on the homologous [2]catenane, only to find that the kinetic asymmetry was insufficient to support unidirectional movement of the sole ring. Accordingly, we incorporated a second CBPQT4+ ring to provide further symmetry breaking by interactions between the two mobile rings. This demonstration of electrically driven continual circumrotatory motion of two rings around a loop in a [3]catenane is free from the production of waste products and represents an important step towards surface-bound14 electric molecular motors.

Silver nanoparticles (Ag-NP) were obtained in MeCN/0.05 M Bu4NPF6 medium by сyclobis(paraquat-p-phenylene) (CBPQT4+) – mediated reduction of the silver ions generated by anodic oxidation of metallic silver during the electrolysis in an undivided cell. Due to multipoint donor-acceptor interaction CBPQT4+ binds the resulting electron-donor Ag-NP to each other, which leads to their enlargement, aggregation and adsorption. This property of the macrocycle allows to call it a “molecular glue” for NP-Ag. In the absence of stabilizers, aggregated polydisperse Ag-NP of indefinite shape are formed with sizes ranging from 20 to 500 nm. Electrosynthesis in the presence of a stabilizer, polyvinylpyrrolidone (PVP), also leads to the formation of aggregated smaller metal particles of 55 ± 26 nm, which have, in addition to the quasi-spherical shape, the shape of a flat triangle and hexagon. Ag-NP stabilized by PVP are partially bound on the surface of nanocellulose (NC). In the presence of NC, larger Ag-NP with an average size of 97 ± 29 nm are formed, the main shape of which is quasi-spherical; cubic, tetrahedral, and rod-shaped Ag-NP are also formed; the formation of Ag-NP with a flat structure is excluded. The catalytic activity of the obtained particles in the reduction of p-nitrophenol with sodium borohydride is extremely low due to the large size, aggregation, and coating of the NP-Ag surface with the stabilizer PVP and marcocycle.

Understanding molecular interactions in mechanically interlocked molecules (MIMs) is challenging because they can be either donor–acceptor interactions or radical pairing interactions, depending on the charge states and multiplicities in the different components of the MIMs. In this work, for the first time, the interactions between cyclobis(paraquat-p-phenylene) (abbreviated as CBPQTn+ (n = 0–4)) and a series of recognition units (RUs) were investigated using the energy decomposition analysis approach (EDA). These RUs include bipyridinium radical cation (BIPY•+), naphthalene-1,8:4,5-bis(dicarboximide) radical anion (NDI•−), their oxidized states (BIPY2+ and NDI), neutral electron-rich tetrathiafulvalene (TTF) and neutral bis-dithiazolyl radical (BTA•). The results of generalized Kohn–Sham energy decomposition analysis (GKS-EDA) reveal that for the CBPQTn+···RU interactions, correlation/dispersion terms always have large contributions, while electrostatic and desolvation terms are sensitive to the variation in charge states in CBPQTn+ and RU. For all the CBPQTn+···RU interactions, desolvation terms always tend to overcome the repulsive electrostatic interactions between the CBPQT cation and RU cation. Electrostatic interaction is important when RU has the negative charge. Moreover, the different physical origins of donor–acceptor interactions and radical pairing interactions are compared and discussed. Compared to donor–acceptor interactions, in radical pairing interactions, the polarization term is always small, while the correlation/dispersion term is important. With regard to donor–acceptor interactions, in some cases, polarization terms could be quite large due to the electron transfer between the CBPQT ring and RU, which responds to the large geometrical relaxation of the whole systems.

L’association de la science des polymères et de la chimie supramoléculaire a conduit au développement de matériaux polymères supramoléculaires dotés de propriétés structurelles, mécaniques et fonctionnelles atypiques. Ces matériaux sont d’ores et déjà exploités dans divers domaines d’applications, tels que les matériaux auto réparants,l’ingénieur tissulaire ou encore la libération contrôlée de principes actifs. Ainsi, la chimie supramoléculaire s’est avérée être un outil puissant pour moduler les propriétés des matériaux en contrôlant le caractère dynamique des interactions supramoléculaires via l’application de stimuli adaptés. Les travaux réalisés dans le cadre de cette thèse s’inscrivent dans ce contexte et avaient pour principal objectif de développer de nouveaux assemblages (macro)moléculaires à base de complexes intra- et inter-moléculaires de CBPQT4+. Pour ce faire, un nouveau dérivé CBPQT4+-Fu intégrant une unité furane connectée de manière covalente à la partie hôte CBPQT4+ a été développé.Ce dérivé se présente en milieu aqueux sous une conformation auto-incluse dans laquelle l’unité furane au sein de la cavité témoigne d’une extrêmement faible réactivité(Diels-Alder) vis-à-vis de diènophiles. Néanmoins, celle-ci peut être libérée en ajoutant une molécule invitée (Naphtalène) présentant une forte affinité pour le macrocycle.Cette synergie, mise en évidence à l’échelle moléculaire, permettant de déclencher la réaction de Diels-Alder par la formation d’un complexe intramoléculaire a ensuite été exploitée pour concevoir divers hydrogels physiques ou réticulés physiquement et chimiquement
The combination of polymer science and supramolecular chemistry has led to thedevelopment of supramolecular polymer materials with unusual structural, mechanical,and functional properties. These materials have already been exploited in manyapplications, including self-repairing materials, tissue engineering, and the controlledrelease of active ingredients. Supramolecular chemistry has proved to be a powerful toolfor modulating the properties of materials by controlling the dynamic nature ofsupramolecular interactions using appropriate stimuli. The work carried out within theframework of this thesis falls within this context, and its main objective was to developnew (macro)molecular assemblies based on intra- and inter-molecular CBPQT4+complexes. To this end, a new CBPQT4+-Fu derivative was developed, integrating a furanunit covalently connected to the CBPQT4+ host moiety. This derivative presents itself inaqueous media a self-included conformation in which the furan unit within the cavityexhibits extremely low reactivity (Diels-Alder) towards dienophiles. However, this can bereleased by adding a guest molecule (naphthalene) with a strong affinity for themacrocycle. This synergy, demonstrated at the molecular scale, enabling the Diels-Alderreaction to be triggered by forming an intramolecular complex, was then exploited to design various physical and chemically cross-linked hydrogels

Les matériaux polymères multi stimulables sont d’ores et déjà utilisés dans différents domaines d’applications, tels que le relargage de principes actifs sur commande, l’ingénierie tissulaire, les matériaux auto réparants ou les senseurs. Depuis une vingtaine d’années, la chimie supramoléculaire s’est révélée être un outil de choix pour créer ce type de matériaux dits « intelligents ». Elle permet en effet de moduler voir de programmer les propriétés des matériaux en contrôlant le caractère dynamique des interactions supramoléculaires via l’application de stimuli adaptés. Les travaux réalisés dans le cadre de cette thèse financée par l’ANR (projet STRAPA) avaient pour principal objectif d’exploiter des complexes à base de cyclobis paraquat paraphénylène (CBPQT4+) et d’entités riches en électrons (tétrathiafulvalène, naphtalène) pour concevoir des hydrogels supramoléculaires multi-stimulables. Deux types d’hydrogels ont été développés : des hydrogels physiques (réticulés de manière supramoléculaire) capables de présenter une transition sol-gel sous stimuli (température, ajout de molécules compétitrices) et des hydrogels chimiques (réticulés de manière permanente) dotés de motifs de reconnaissance moléculaire riches en électrons dont les propriétés de gonflement peuvent être finement contrôlées. En particulier, nous avons montré que celles-ci pouvaient être manipulées très facilement via le nombre d’unités riches en électrons présents au sein des hydrogels, en contrôlant le pourcentage de complexes formés, ainsi qu’en appliquant divers stimuli (température, red/ox, macromolécules compétitrices, tensioactifs)
Multistimuli-responsive polymer materials play an important role in various fields of applications, (drug delivery system, tissue engineering, and self-healing materials. In the last past decades, supramolecular chemistry has emerged as a powerful tool to build such smart materials. Indeed, thanks to the inherent and/or induced dynamic behavior of supramolecular interactions, materials properties can be potentially tuned or even programmed. The main objective of this thesis, that have been carried out in the framework of the STRAPA ANR project, was to exploit host-guest interactions formed from the cyclobis paraquat paraphenylene (CBPQT4+) host molecule and electron-rich entities (tetrathiafulvalene, naphthalene) to conceive multi-stimuli responsive hydrogels. Two kind of smart hydrogels have been developed : physical hydrogels in which the sol-gel transition can be controlled upon heating or by adding competitive molecules, and chemical hydrogels with programmable swelling properties. In the last case, we have notably shown that the actuating behavior of hydrogels could be finely triggered by applying various environmental stimuli (T, red/ox, competitive macromolecules and surfactants)

Orientadora : Profª Drª Nadia Krieger
Tese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Química. Defesa: Curitiba, 31/10/2014
Inclui referências : f. 123-140
Resumo: A produção do biodiesel em escala industrial é realizada pela transesterificação alcalina em meio homogêneo utilizando alcóxidos metálicos como catalisadores e variando-se o tipo de óleo vegetal de acordo com a região. Neste processo é necessário utilizar óleo com baixo teor de ácidos graxos livres e baixo teor de umidade, o que limita o uso de matérias-primas de baixo custo. Por isto, novos processos têm sido estudados para possibilitar o uso de matérias-primas residuais, como a síntese enzimática de biodiesel tem sido exaustivamente investigada. No entanto, o desenvolvimento e a implantação do processo em escala industrial ainda são dificultados pelo elevado custo da enzima e baixa produtividade do processo enzimático. No presente trabalho, a fermentação em estado sólido (FES) foi utilizada para reduzir o custo das enzimas para a produção de biodiesel. Foram realizados cultivos de Rhizopus microsporus CBPQA 312-07 DRM usando bagaço de cana impregnado de solução nutriente enriquecida com ureia, oligoelementos e óleo de soja. Este sólido fermentado foi seco, caracterizado e utilizado diretamente para catalisar a síntese de biodiesel. Nos estudos de esterificação etílica em presença de n-heptano, conversões em éster de 98% foram obtidas em 4 h e a conversão se manteve após a reutilização do sólido por 23 vezes. Em sistema livre de solventes, o ácido oleico foi inicialmente utilizado como substrato para o estudo de esterificação etílica, onde foram obtidos 98% de conversão em 48 h, com adição de 20% (m/m) de peneira molecular ao meio de reação. Em seguida, foi realizado um delineamento fatorial 22 onde se investigou o efeito da temperatura e da razão molar dos substratos (ácido oleico e mistura de ácidos graxos da borra de soja - AGBS) na esterificação etílica. A reação otimizada, realizada nas condições de razão molar 10:1 (etanol: ácido graxo), a 40 ºC, atingiu conversões de 98% e de 86% em 48 h, para o ácido oleico e AGBS, respectivamente. Os resultados obtidos neste trabalho mostram que foi possível produzir ésteres do biodiesel por esterificação num sistema livre de solventes, utilizando um catalisador produzido por FES a partir de bagaço de cana impregnado com solução nutriente. Essa estratégia minimiza os custos de produção das lipases para aplicação na produção de biodiesel. Palavras-chave: lipases, biodiesel, Rhizopus microsporus, fermentação em estado sólido, esterificação, sistema livre de solventes, síntese enzimática.
Abstract: Industrially, biodiesel is produced by homogeneous alkaline transesterification of vegetable oils with methanol. An important disadvantage of the chemical route is the need to use refined feedstocks, which are costly. These disadvantages have prompted researchers to study the enzymatic route, which allows the use of less costly residual oils. However, the enzymatic route is currently not competitive, due to the high cost of the lipases. In the present work, solid-state fermentation was used to reduce the cost of the enzyme. Rhizopus microsporus CBPQA 312-07 DRM was cultivated on sugarcane bagasse that had been impregnated with a nutrient solution containing urea, mineral salts and soybean oil. The fermented solid produced in this process was dried, characterized and added directly to the reaction medium to catalyze the esterification of oleic acid with ethanol. In the presence of n-heptane, conversions of 98% were obtained at 4 h and the fermented solid maintained this conversion in 23 consecutive batches. In solvent-free system with the addition of 20% (w/w) of molecular sieve, a conversion of 98% was obtained in 48 h. Two 22 factorial experiments were then carried out in solvent-free medium, one using oleic and one using soybean soapstock fatty acids (SSFA) as the fatty acid source. The variables studied were the reaction temperature and the molar ratio of ethanol to fatty acid. The optimum conditions were 40 ºC and a molar ratio of ethanol to fatty acid of 10:1, giving conversions at 48 h of 98% with oleic acid and 86% with SSFA. This work has shown that it is possible to obtain high yields of ethyl esters in a solventfree medium, using a lower cost fatty acid feedstock and a biological catalyst produced by solid-state fermentation of a nutrient-impregnated sugarcane bagasse. This strategy has the potential to reduce the cost of the enzymatic route for biodiesel production. Keywords: lipases, biodiesel, Rhizopus microsporus, solid-state fermentation, esterification, solvent free system, enzymatic synthesis.