This thesis deals with the effects of host-guest complexation, based on cucurbit[n]uril (CB[n], n = 6, 7 and 8) host molecule, on the chemical, electrochemical and spectroscopic properties of the included guests. Both CB[6] and CB[7] form 1:1 complexes with [CH3bpy(CH2)6bpyCH]4+3, encapsulating the central hexamethylene chain. With its relatively larger cavity, a second CB[7] host will include one of the viologen units, forcing, through steric and electronic repulsions, the first CB[7] to abandon the inclusion of the central chain and move to the other viologen unit, thus forming a [3]pseudorotaxane. The inclusion of the two enantiomers of protonated N-benzyl-1-(1-naphthyl)ethylamine in the achiral CB[7] results in a five-fold increase in the molar optical rotation of {BNEAH•CB[7]}+ and significant changes in the longer wavelength band in the circular dichroism spectra, attributed to a restricted rotation of the naphthyl group about the chiral center upon inclusion of the benzyl portion of the guest in the CB[7] cavity. The effects of host-guest complexation of the (trimethylammonio)- methylferrocene(+/2+) couple (FcTMA+/2+) by CB[7] on the kinetics of its electron self-exchange and electron transfer reactions were investigated. The slow exchange of the ferrocene guest, allows for the simultaneous monitoring of the 1H NMR line-broadening for both the FcTMA++ and {FcTMA•CB[7]} species in the presence of the paramagnetic FcTMA2+; The electron self-exchange rate constant increases moderately upon inclusion of both reduced and oxidized species, while the rate constants for the oxidation of ferrocenes by the bis(2,6-pyridinedicarboxylato)cobaltate(III) ion (which does not bind to CB[7]), were significantly reduced a result of reduced thermodynamic driving forces and steric hindrance to close approach of the oxidant to the encapsulated ferrocenes. This work was extended to investigations of the inclusion of bis(ferrocene) guests, demonstrating that a sufficiently long linker is required to accommodate a CB[7] host on each ferrocene unit. The formation of stable host-guest complexes of the bent titanocene, TiCp2+(H22O)2, with both CB[7] and CB[8] were characterized in aqueous solution. The CB[8] formed a more stable complex than CB[7], contrary to the order observed with ferrocene guests, attributable to the larger radius of the bent titanocene guest. / Thesis (Ph.D, Chemistry) -- Queen's University, 2008-01-26 01:58:19.958

The movement away from metals towards polymers for automobile bearing coatings opens a new area for the possible modification of these coatings. This project, done in collaboration with Castrol, was to understand adsorption of small molecules at the surface of these polymers and work towards engineering host-guest interactions at the surface to provide binding of specific molecules. Initially, the commercial polyamide-imide was characterised via Nuclear Magnetic Resonance (NMR), Infrared (IR) and Ultra-Violet/Visible (UV-Vis) spectroscopy to understand the nature of the functional groups and structures present. This revealed that the imidisation reaction was incomplete so the functionality within the polymer could change and thus alter how molecules interact with it. This reaction was then investigated via IR and NMR spectroscopy and it was shown that the degree of imidisation varied with temperature. Then the characterised polyamide-imide was used to study the adsorption of alkylphenols, a class of molecules that have structures and functionality like common additives used in engine oils. Additionally, the adsorption of water was studied as it is a common contaminant. These two systems were studied via solution depletion isotherms and neutron reflectivity measurements. The isotherms confirmed the adsorption of the molecules whilst neutron reflection was used to characterise the layers. For alkylphenol, a rather sparsely packed layer of the molecules and solvent existed at the surface with their alkyl tails extending into the solvent. For water; the molecules diffuse into the polyamide-imide. It can be partially removed by washing the surface with dry dodecane; however, some water remains in the polymer layer. A viologen-cucurbit[8]uril binding site was chosen as the supramolecular surface interaction. The binding unit was incorporated into the polyamide-imide. The synthesis of the binding site polymer was achieved in two stages; the reproduction of the commercial polymer and the synthesis of a polymer containing 100% viologen with and without threaded cucurbit[8]uril. Whilst the synthesis appeared successful, neutron reflectivity measurements showed that, when in contact with a solution containing a second guest, no adsorption was seen on the polymer containing cucurbit[8]uril. In order to study the supramolecular interaction in non-polar solvent, a series of rotaxanes were synthesised with viologen-cucurbit[8]uril cores and bulky stopper groups to prevent unthreading of the cucurbituril as well as enhancing the solubility of the system. The two components were linked via an amidisation reaction between an acid chloride and an amine. Due to the low solubility of the products confirmation of synthesis was only possible in one case. As well as using a viologen-cucurbit[8]uril binding site, binding in cucurbiturils via halogen bonding was investigated as common halogen bonding species show good solubility in non-polar solvents. Initially co-crystals of 2,5-diiodo-1,3,4,6-tetrafluorobenzene with tertiary amides were studied. With N,N-dimethylformamide, a 1:2 co-crystal was seen but the structure with N-methyl-2-pyrrolidone had a stoichiometry of 1:1. In both structures the oxygen of the amide is involved in a halogen bonding; however, for N-methyl-2-pyrrolidone it is bifurcated leading to the formation of chains. A 50-50 mixture of pyridine and formic acid was found to solubilize both halogen bond donors and cucurbit[n]uril. Over the course of these experiments the structure of the co-crystals of two halogen bond donors, 2,5-diiodo-1,3,4,6-tetrafluorobenzene and 2,4,6-triiodo-1,3,5-trifluorobenzene, with pyridine were determined. Crystals of the cucurbituril-adducts weren’t of sufficient quality to determine the structure. The presence of binding solution was confirmed by 1H and 19F NMR experiments on the methyliodide-cucurbit[6]uril and Trans-diiodooctrafluoroazobenzene-cucurbit[8]uril systems.

No description available.

Compósitos de xerogel de pentóxido de vanádio (VXG) com cucurbit[6]urila (CB[6]), hemicucurbit[6]urila (HCB[6]) e oxovanadio(IV)cucurbit[6]urila (CB[6]VO) em diferentes concentrações foram preparados por mistura mecânica dos macrociclos com o gel de V2O5. Misturas homogêneas foram obtidas para quantidades até 10% em mol de CB[6] e HCB[6], e 1% de CB[6]VO. Estes macrociclos foram intercalados nos espaços interlamelares do VXG como mostram os dados de difração de raios-X (DRX), aumentando o espaço interlamelar e criando dois domínios cristalográficos distintos. As propriedades estruturais e composição destes intercalados foram estudadas por espectroscopia no infravermelho, análise termogravimétrica, microscopia eletrônica de varredura e microscopia de força atômica. Ensaios eletroquímicos mostraram que a capacidade específica de carga inicial do VXG (158 mA.h.g-1) melhora com a presença de CB[6] (168 mA.h.g-1), da HCB[6] (200 mA.h.g-1), e principalmente com CB[6]VO (230 mA.h.g-1), em filmes finos com baixa concentração dos macrociclos. Isto supera a capacidade de eletrodos de bateria comerciais. Nos intercalados com CB[6] a complexação dos íons Li+ com seus opérculos prejudica a reversibilidade na inserção/desinserção deste íon, diminuindo drasticamente a ciclabilidade de carga/descarga; a presença da HCB[6], que não complexa com o íon Li+, não sustenta a estrutura do VXG ao longo de vários ciclos, por não ser um macrociclo rígido. A presença de CB[6]VO parece estabilizar a estrutura do VXG oferencendo caminhos alternativos na difusão do íon Li+, que não complexa com os opérculos da CB obstruído pelo ion VO2+, aumentando a ciclabilidade, mantendo sua carga específica em aproximadamente 88% após 40 ciclos cronopotenciométricos. / Cucurbit[n]uril (CB[n]), hemi-cucurbit[6]uril (HCB[6]), and oxovanadium(IV)cucurbit[6]uril (CB[6]VO) vanadium pentoxide composites were prepared in several mole ratios by mechanically mixing the macrocycles and the V2O5 gel. Homogeneous mixtures were obtained for amounts as high as 10% in mol of CB[6] and HCB[6] and 1% of CB[6]VO. These macrocycles were intercalated in VXG interlamellar space as we could demonstrate with X-ray powder diffraction experiments (XRPD),which clearly show basal distance expansions and the formation of two crystallographic domains. The structural properties of such intercalates as well as their composition were studied with infrared spectroscopy, thermogravimmetric analysis, sweeping electron microscopy, and atomic force microscopy. Electrochemical experiments have shown that the initial specific charge capacity of VXG (158 mA.h.g1) was enhanced with the addition of CB[6] (168 mA.h.g1) and HCB[6] (200 mA.h.g1) and even more with (230 mA.h.g1) in thin films with low macrocycle amounts. These capacities exceed commercial batteries electrodes. Complexation of CB[6] with Li+ ions in CB[6]/VXG intercalates reduces considerably the reversibility of insertion/expulsion of this ion, reducing drastically its charge/discharge cyclability. The presence of HCB[6], who does not bind Li+ ions, is not rigid enough to sustain the oxide structure during many cycles. The presence of CB[6]VO seems to stabilize the VXG structure and offers alternative pathways for Li+ diffusion. It does not bind these ions since the occulli are occupied by VO2+ ions, enhancing cyclability. Its specific charge remains as high as 88% of the maximum charge capacity after 40 chronopotentiometric cycles.

Compósitos de xerogel de pentóxido de vanádio (VXG) com cucurbit[6]urila (CB[6]), hemicucurbit[6]urila (HCB[6]) e oxovanadio(IV)cucurbit[6]urila (CB[6]VO) em diferentes concentrações foram preparados por mistura mecânica dos macrociclos com o gel de V2O5. Misturas homogêneas foram obtidas para quantidades até 10% em mol de CB[6] e HCB[6], e 1% de CB[6]VO. Estes macrociclos foram intercalados nos espaços interlamelares do VXG como mostram os dados de difração de raios-X (DRX), aumentando o espaço interlamelar e criando dois domínios cristalográficos distintos. As propriedades estruturais e composição destes intercalados foram estudadas por espectroscopia no infravermelho, análise termogravimétrica, microscopia eletrônica de varredura e microscopia de força atômica. Ensaios eletroquímicos mostraram que a capacidade específica de carga inicial do VXG (158 mA.h.g-1) melhora com a presença de CB[6] (168 mA.h.g-1), da HCB[6] (200 mA.h.g-1), e principalmente com CB[6]VO (230 mA.h.g-1), em filmes finos com baixa concentração dos macrociclos. Isto supera a capacidade de eletrodos de bateria comerciais. Nos intercalados com CB[6] a complexação dos íons Li+ com seus opérculos prejudica a reversibilidade na inserção/desinserção deste íon, diminuindo drasticamente a ciclabilidade de carga/descarga; a presença da HCB[6], que não complexa com o íon Li+, não sustenta a estrutura do VXG ao longo de vários ciclos, por não ser um macrociclo rígido. A presença de CB[6]VO parece estabilizar a estrutura do VXG oferencendo caminhos alternativos na difusão do íon Li+, que não complexa com os opérculos da CB obstruído pelo ion VO2+, aumentando a ciclabilidade, mantendo sua carga específica em aproximadamente 88% após 40 ciclos cronopotenciométricos. / Cucurbit[n]uril (CB[n]), hemi-cucurbit[6]uril (HCB[6]), and oxovanadium(IV)cucurbit[6]uril (CB[6]VO) vanadium pentoxide composites were prepared in several mole ratios by mechanically mixing the macrocycles and the V2O5 gel. Homogeneous mixtures were obtained for amounts as high as 10% in mol of CB[6] and HCB[6] and 1% of CB[6]VO. These macrocycles were intercalated in VXG interlamellar space as we could demonstrate with X-ray powder diffraction experiments (XRPD),which clearly show basal distance expansions and the formation of two crystallographic domains. The structural properties of such intercalates as well as their composition were studied with infrared spectroscopy, thermogravimmetric analysis, sweeping electron microscopy, and atomic force microscopy. Electrochemical experiments have shown that the initial specific charge capacity of VXG (158 mA.h.g1) was enhanced with the addition of CB[6] (168 mA.h.g1) and HCB[6] (200 mA.h.g1) and even more with (230 mA.h.g1) in thin films with low macrocycle amounts. These capacities exceed commercial batteries electrodes. Complexation of CB[6] with Li+ ions in CB[6]/VXG intercalates reduces considerably the reversibility of insertion/expulsion of this ion, reducing drastically its charge/discharge cyclability. The presence of HCB[6], who does not bind Li+ ions, is not rigid enough to sustain the oxide structure during many cycles. The presence of CB[6]VO seems to stabilize the VXG structure and offers alternative pathways for Li+ diffusion. It does not bind these ions since the occulli are occupied by VO2+ ions, enhancing cyclability. Its specific charge remains as high as 88% of the maximum charge capacity after 40 chronopotentiometric cycles.

For more than 150 years, since the synthesis of urea by Friedrich Wöhler in 1828, molecular chemistry has developed a vast array of highly sophisticated and powerful methods for the construction of more complex molecular structures. Beyond the molecular chemistry based on the covalent bond, there lies the field of supramolecular chemistry, aims to gain control over the intermolecular bond. Supramolecular species are characterized both by the spatial arrangement of their components and by the nature of the intermolecular bonds that hold these components together. They possess well-defined structural, conformational, thermodynamic and kinetic properties. Research has been focused on utilization of such confined spaces to manipulate reaction dynamics, properties of the encapsulated guest molecules. This research presented in this thesis is a consolidated account of photophysical and photochemical reactions carried in water-soluble macrocycles, cavitands and dynamic host systems such as dendrimers and micelles. With the aid of NMR (1D and 2D) spectroscopic techniques, the host-guest complex characterization is executed.

Les cucurbiturils (CBn) sont des molécules-cages synthétiques constituées d’un nombre n d’unités glycoluril et dont les applications en chimie, en biologie et en physique ont commencé à être exploitées au début des années 2000. Ces composés trouvent leur importance dans un grand nombre de domaines incluant la chimie en phase solide, le piégeage des contaminants en solution, la catalyse ou encore l’encapsulation de principes actifs pour des applications pharmaceutiques futures. Ces récentes molécules-cages rejoignent le large groupe des récepteurs synthétiques comprenant les cyclodextrines, les calixarènes, les cryptophanes, les carcérands et hémicarcérands. L’encapsulation des gaz dans ce type de structures est encore mal connue à l’heure actuelle et, dans ces travaux de thèse, notre intérêt s’est porté sur la complexation de gaz, notamment de xénon, dans les cucurbiturils. Ces travaux ont débuté par la synthèse de nouveaux cucurbiturils hydrosolubles dans le but d’étudier leur capacité d’encapsulation des gaz rares et de petits alcanes comme le méthane et l’éthane, notre objectif final étant de définir de nouvelles règles régissant l’encapsulation des gaz par les cucurbiturils. Les gaz rares allant de l’hélium au krypton ont été étudiés. Parmi ces gaz, le xénon hyperpolarisé a particulièrement retenu notre attention du fait de son intérêt dans la conception de biosondes pour le développement de nouvelles méthodes de diagnostic en IRM. Dans ce mémoire, la synthèse de nouveaux cyclohexylcucurbiturils mixtes hydrosolubles et leurs études en présence de xénon sont rapportées. Un nouveau cucurbituril mixte constitué de cinq unités glycoluril et d’une unité glycoluril à six chaînons a également été synthétisé. Les deux premiers chapitres constituent une introduction au phénomène d’encapsulation des gaz ainsi que des généralités sur la famille des cucurbiturils. Le troisième chapitre est consacré aux résultats obtenus au laboratoire sur la synthèse de nouveaux composés. Dans un quatrième chapitre, nous avons développé une méthode permettant la préparation de précurseurs d’analogues acycliques de cucurbiturils. Pour cela, la réaction de métathèse par ouverture de cycle associée à la métathèse croisée (ROM-CM) a été utilisée pour mener à bien cette synthèse. Enfin, un cinquième chapitre est consacré aux résultats concernant l’étude de l’encapsulation de gaz dans les nouveaux cucurbiturils synthétisés, étude effectuée en collaboration avec le Laboratoire de Structure et Dynamique par Résonance Magnétique du CEA de Saclay. / The cucurbituril family (CBn) constitutes a group of recent synthetic host-molecules. These compounds are formed by n glycoluril units and, since the beginning of the 2000’s, they have found their interest in multiple domains such as biology, chemistry and physics. They have joined the large group of synthetic receptors comprising cyclodextrins, calixarens, cryptophanes, carcerands and hemicarcerands. Gaz encapsulation in this family of compounds is misunderstood. In these PhD works, our interest concerned gaz complexation, especially xenon, into cucurbiturils. First, the synthesis of new hydrosoluble cucurbiturils to study their ability to encapsulate noble gaz and small alcans such as methan and ethan is described. Our final goal will be to define new rules concerning gaz encapsulation by cucurbiturils. Noble gaz from helium to krypton have been studied. Among these noble gaz, xenon is particularly interesting in the domain of biosensing, for the design of new diagnostic methods by MRI. In this manuscript, the synthesis of a family of hydrosoluble cyclohexylcucurbiturils and their ability to encapsulate xenon is described. Another new cucurbituril constituted by five glycoluril units and one glycoluril unit forming a six-membered ring, has also been prepared. The first two parts of the manuscript present the gaz encapsulation and the cucurbituril family. The third part describes our results concerning the new synthetized cucurbiturils. In the fourth part, we have developped a method based on metathesis reactions (ROM-CM) for preparing some precursors of acyclic congeneers of cucurbiturils. Lastly, the fifth part concerns results about gaz encapsulation. All of this study has been driven in collaboration with Laboratoire de Structure et Dynamique par Résonance Magnétique (CEA Saclay).

As antocianinas compreendem o maior conjunto de pigmentos naturais do Reino Vegetal. São caracterizadas pelas colorações vermelha, roxa e azul de uma variedade de flores, frutas e folhas. A sua estabilidade é influenciada por diversos fatores como o pH local do meio, temperatura, luz ou copigmentos. A inclusão das antocianinas e análogos sintéticos, os sais de flavílio, dentro da cavidade da cucurbit[7]uril (CB[7]), sistema hóspede-hospedeiro, foi estudada a partir da espectroscopia de fluorescência. As antocianinas sintéticas utilizadas foram o cloreto de 7-hidroxi-4-metilflavílio (HMF) e o cloreto de 7-metoxi-4-metilflavílio (MMF) e as antocianinas naturais foram a cianindina-3-glicosídeo, cianidina-3,5-di-O-glicosídeo e antocianinas presentes no extrato do jambolão (Syzygium cumini). Os complexos de inclusão das antocianinas e os análogos sintéticos dentro da cavidade do CB[7] apresentaram uma estequiometria de inclusão do tipo 1:2, uma molécula hóspede e duas moléculas hospedeiras. A estequiometria de inclusão e as constantes de incorporação foram determinadas a partir de isotermas da inclusão pelo método de regressão não-linear. Para os íons flavílios, a determinação da estequiometria também foi comprovada pelo Método da Variação Contínua (MVC) ou método Job. A primeira constante de incorporação K11 obtida para as antocianinas e os íons flavílios foi da ordem de 105 - 106 M-1. Essa elevada constante de incorporação é devida à interação eletrostática entre as carbonilas do CB[7] e a carga positiva do anel pírilio das antocianinas. Entretanto, a segunda constante de incorporação, K12, apresenta um valor menor por causa da repulsão entre a primeira e a segunda molécula de CB[7]. A segunda constante de inclusão das antocianinas naturais apresentou um valor muito baixo em relação à segunda constante de incorporação do HMF e MMF. Essa diferença ocorreu pelo impedimento estérico provocado pelas unidades glicosídicas presentes nas antocianinas naturais. A hidratação das antocianinas do jambolão é uma reação muito rápida, ocorrendo em pH acima de 3,0. Quando o CB[7] foi adicionado às antocianinas em pH 4,62, a hidratação foi um pouco menor, mas mesmo assim a hidratação ocorreu. Após 24 horas, quando o equilíbrio das antocianinas do jambolão fosse deslocado na direção de formação das chalconas, o CB[7] foi adicionado ao meio, em elevadas concentrações. O equilíbrio de hidratação foi deslocado em direção ao cátion flavílio, indicando um aumento na estabilização desses compostos. / The anthocyanins, the largest group of natural plant pigments, are responsible for the red, purple and blue colors of a variety of flowers, fruit and leaves. Their stability is influenced by several factors, including the local pH of the medium, temperature, light and copigments. The inclusion of natural anthocyanins and their synthetic analogs, flavylium cations, in the cavity of cucurbit[7]uril, CB[7], to form host-guest complexes, was studied by fluorescence spectroscopy. The synthetic anthocyanin model compounds utilized were 7-hydroxy-4-methylalavylium (HMF) chloride and 7-methoxy-4-methylflavylium (MMF) chloride and the naturally-occurring anthocyanins were cyaniding-3-O-glucoside, cyaniding-3,5-di-O-glucoside and the anthocyanins extracted from jambolão (Syzygium cumini) fruit. The inclusion complexes of the anthocyanins and synthetic anthocyanin analogs with CB[7] presented a stoichiometry of 1:2, with one molecule of guest and two molecules of host. The stoichiometry of the inclusion and the incorporation equilibrium constants were determined from the binding isotherms by non-linear regression. For the synthetic flavylium ions, the stoichiometry was also verified using the method of continuous variations or Job plots. The first binding constant, K11, between the anthocyanins or flavylium ions and CB[7] was of the order of 105-106 M-1. This large equilibrium constant for incorporation reflects the electrostatic interaction between the carbonyl groups of CB[7] and the positive charge of the pyrilium ring of the anthocyanins. The binding constant for the second CB[7], K12, has a smaller value due to the repulsion between the first and second molecules of CB[7]. The second binding constant for the inclusion of the natural anthocyanins was much smaller than that of the synthetic anthocyanin analogs HMF and MMF. This difference was due to the steric hindrance afforded by the sugar residues present in the natural anthocyanins. The hydration of the anthocyanins of jambolão is very rapid above pH 3. When CB[7] was added to a mixture of jambolão anthocyanins at pH 4.62, the extent of hydration was diminished, but partial hydration did still occur. After equilibration at pH 4.62 for 24 hrs to form the chalcones, addition of high concentrations of CB[7] shifted the equilibrium back in the direction of the flavylium cation form of the anthocyanins, demonstrating the increase in the stabilization of this form upon host-guest complexation.

As antocianinas compreendem o maior conjunto de pigmentos naturais do Reino Vegetal. São caracterizadas pelas colorações vermelha, roxa e azul de uma variedade de flores, frutas e folhas. A sua estabilidade é influenciada por diversos fatores como o pH local do meio, temperatura, luz ou copigmentos. A inclusão das antocianinas e análogos sintéticos, os sais de flavílio, dentro da cavidade da cucurbit[7]uril (CB[7]), sistema hóspede-hospedeiro, foi estudada a partir da espectroscopia de fluorescência. As antocianinas sintéticas utilizadas foram o cloreto de 7-hidroxi-4-metilflavílio (HMF) e o cloreto de 7-metoxi-4-metilflavílio (MMF) e as antocianinas naturais foram a cianindina-3-glicosídeo, cianidina-3,5-di-O-glicosídeo e antocianinas presentes no extrato do jambolão (Syzygium cumini). Os complexos de inclusão das antocianinas e os análogos sintéticos dentro da cavidade do CB[7] apresentaram uma estequiometria de inclusão do tipo 1:2, uma molécula hóspede e duas moléculas hospedeiras. A estequiometria de inclusão e as constantes de incorporação foram determinadas a partir de isotermas da inclusão pelo método de regressão não-linear. Para os íons flavílios, a determinação da estequiometria também foi comprovada pelo Método da Variação Contínua (MVC) ou método Job. A primeira constante de incorporação K11 obtida para as antocianinas e os íons flavílios foi da ordem de 105 - 106 M-1. Essa elevada constante de incorporação é devida à interação eletrostática entre as carbonilas do CB[7] e a carga positiva do anel pírilio das antocianinas. Entretanto, a segunda constante de incorporação, K12, apresenta um valor menor por causa da repulsão entre a primeira e a segunda molécula de CB[7]. A segunda constante de inclusão das antocianinas naturais apresentou um valor muito baixo em relação à segunda constante de incorporação do HMF e MMF. Essa diferença ocorreu pelo impedimento estérico provocado pelas unidades glicosídicas presentes nas antocianinas naturais. A hidratação das antocianinas do jambolão é uma reação muito rápida, ocorrendo em pH acima de 3,0. Quando o CB[7] foi adicionado às antocianinas em pH 4,62, a hidratação foi um pouco menor, mas mesmo assim a hidratação ocorreu. Após 24 horas, quando o equilíbrio das antocianinas do jambolão fosse deslocado na direção de formação das chalconas, o CB[7] foi adicionado ao meio, em elevadas concentrações. O equilíbrio de hidratação foi deslocado em direção ao cátion flavílio, indicando um aumento na estabilização desses compostos. / The anthocyanins, the largest group of natural plant pigments, are responsible for the red, purple and blue colors of a variety of flowers, fruit and leaves. Their stability is influenced by several factors, including the local pH of the medium, temperature, light and copigments. The inclusion of natural anthocyanins and their synthetic analogs, flavylium cations, in the cavity of cucurbit[7]uril, CB[7], to form host-guest complexes, was studied by fluorescence spectroscopy. The synthetic anthocyanin model compounds utilized were 7-hydroxy-4-methylalavylium (HMF) chloride and 7-methoxy-4-methylflavylium (MMF) chloride and the naturally-occurring anthocyanins were cyaniding-3-O-glucoside, cyaniding-3,5-di-O-glucoside and the anthocyanins extracted from jambolão (Syzygium cumini) fruit. The inclusion complexes of the anthocyanins and synthetic anthocyanin analogs with CB[7] presented a stoichiometry of 1:2, with one molecule of guest and two molecules of host. The stoichiometry of the inclusion and the incorporation equilibrium constants were determined from the binding isotherms by non-linear regression. For the synthetic flavylium ions, the stoichiometry was also verified using the method of continuous variations or Job plots. The first binding constant, K11, between the anthocyanins or flavylium ions and CB[7] was of the order of 105-106 M-1. This large equilibrium constant for incorporation reflects the electrostatic interaction between the carbonyl groups of CB[7] and the positive charge of the pyrilium ring of the anthocyanins. The binding constant for the second CB[7], K12, has a smaller value due to the repulsion between the first and second molecules of CB[7]. The second binding constant for the inclusion of the natural anthocyanins was much smaller than that of the synthetic anthocyanin analogs HMF and MMF. This difference was due to the steric hindrance afforded by the sugar residues present in the natural anthocyanins. The hydration of the anthocyanins of jambolão is very rapid above pH 3. When CB[7] was added to a mixture of jambolão anthocyanins at pH 4.62, the extent of hydration was diminished, but partial hydration did still occur. After equilibration at pH 4.62 for 24 hrs to form the chalcones, addition of high concentrations of CB[7] shifted the equilibrium back in the direction of the flavylium cation form of the anthocyanins, demonstrating the increase in the stabilization of this form upon host-guest complexation.

This thesis describes the host-guest chemistry between cucurbit[7]uril (CB[7]) and various series of guests, including neutral polar organic solvents, bis(pyridinium)alkane dications, local anaesthetics, acetylcholine analogues, as well as succinylcholine and decamethonium analogues, in aqueous solution. A focus of this thesis is the effects of varying the chemical structures within different series of guests upon the nature of the host-guest chemistry, such as the relative position and orientation of the guest relative to the CB[7] cavity, and the strengths of the binding affinities. The binding affinities of polar organic solvents with CB[7] depend upon the hydrophobic effect and dipole-quadrupole interactions. The polar guests align themselves so that their dipole moment is perpendicular to the quadrupole moment of CB[7]. The binding strengths of acetone and acetophenone to CB[7] decrease in the presence of alkali metals. Discrete 1:1 and 2:1 host-guest complexes are formed between CB[7] and a series of bis(pyridinium)alkane guests. In most cases the CB[7] initially occupies the aliphatic linker when the 1:1 complex is formed and migrates to the terminal regions as the second CB[7] is added. When bulky, hydrophobic tert-butyl substituents are present, however, the CB[7] occupies the terminal pyridinium region and not the central linker. Supramolecular complexes between CB[7] and a series of local anaesthetics have binding affinities 2-3 orders of magnitude greater than reported values with beta-cyclodextrin. The first pKa values of the guests increase by 0.5-1.9 units upon complexation. The binding positions of the guests within CB[7] differ in neutral and acidic media, with the systems thus behaving as pH-activated switches. With supramolecular complexes between CB[7] and various cationic cholines and their phosphonium analogues, the CB[7] cavity is occupied by the charge-diffuse cationic region. The binding affinities and positions vary depending on the nature of the onium group as well as the substituents within the guest molecule. Host-guest complexes between CB[7] and dicationic acetylcholinesterase inhibitors have very strong 1:1 binding affinities, with 2:1 binding being significantly weaker. These binding affinities are related to the nature of the cationic onium groups, and the length and hydrophobicity of the connecting linkers. / Thesis (Ph.D, Chemistry) -- Queen's University, 2010-01-28 12:27:37.833