The bite angle of a diphosphine ligand plays an important role in determining the reactivity of a transition metal complex. The coordinated dihydrogen on a transition metal center can be activated toward homolysis or heterolysis depending upon the nature of the metal center and the ancillary ligand environment. The present work deals with our investigations on the effect of the bite angle of the chelating diphosphine ligands in the chemistry of certain ruthenium hydride and dihydrogen complexes. Protonation of the ds-[Ru(H)2(dppm)(PPh3)2] (dppm = Ph2PCH2PPh2) using HBF4-Et2O resulted in the dihydrogen/hydride complex trans-(Formula). This species shows dynamic exchange of the H-atom between the dihydrogen and the hydride ligands. The H-atom site exchange was studied by NMR spectroscopy. Attempts to prepare the ruthenium dihydride complexes, cis-[Ru(H)2(dppe)(PPh3)2] (dppe = Ph2PCH2CH2PPh2) and cw-[Ru(H)2(dppp)(PPh3)2] (dppp = Ph2PCH2CH2CH2PPh2) with larger bite-angled diphosphines dppe and dppp were unsuccessful. Earlier work in our group on the effect of trans nitrile ligands in a series of complexes of the type (Formula)howed that the properties of the bound H2 are almost invariant with a change in the R group of the nitrile. hi an effort to compare those results with analogous ruthenium complexes bearing smaller bite-angled diphosphine, dppm, we synthesized and characterized a series of complexes of the type (Formula). We found that the properties of the bound H2 were once again invariant with a change in the R group of the nitrile. In an effort to compare the effect of having two diphosphine ligands of different bite angles with systems containing symmetrical diphosphine ligands reported by our group,3 we synthesized a series of complexes of the type (Formula). These complexes exhibit hybrid properties in comparison to systems with symmetrical diphosphine ligands in terms of spectroscopic features and chemical reactivity. Thus, the bite angle of the diphosphine ligand has a definite influence on the properties of the bound H2 ligand.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work reports the study of the molecular structure influence of ionic liquid (IL) derived from 1,8-bis(3-methylimidazolium-1-yl)octane in the aggregates formation in a solution ethanol in water (4,75%) and in ethanol (95%). Was varied the anions (Br-, NO3-, BF4-, SCN- e NTf2-) of IL and the aggregation behavior was investigated by various methods, such as differential scanning calorimetry (DSC), conductivity, surface tension, fluorescence and dynamic light scattering (DLS). In the ethanol in water solution (4,75%), the critical aggregation concentration values (cac) (114 to 205 mM), free energy of aggregation (ΔG°a) ( 15 to 18 kJ/mol) and ionization degree (α) (0,37 a 0,44) for the IL with Br-, NO3-, BF4-, SCN- significantly decreased with the increase of anion hydrophobicity. In ethanol, the cac values (165 to 500 mM) and ΔG°a ( 9 to 11 kJ/mol) also decreased with the increase of anion size and hydrophobicity. The free energy adsorption data (ΔG°ads) (-35 to -39 kJ/mol) demonstrated that the ILs, in general, have a good surfactant activity and this property improve with the decrease in the hydrophobic characteristics of anions. In general, in the solvents used in this study, the hydrodynamic radius (Rh) of aggregates ranged between 200 and 500 nm for all the ILs. The critical packing parameter was determined using data from the X-Ray (of IL 4) and surface tension, and showed that aggregates are micelar. The cac data was obtained by the techniques of conductivity, fluorescence and surface tension. Where, was observed that increasing the anion hydrophobicity of dicationic ILs structure favored the formation of aggregates, while less hydrophobic anions improved the surfactant properties of the IL structures. / Este trabalho relata o estudo da influência da estrutura molecular de líquidos iônicos (LI) dicatiônicos, derivados do cátion 1,8-bis(3-metilimidazolil-1-íneo)-octano, na formação de agregados em uma solução etanol em água (4,75%) e em etanol (95%). Variaram-se os ânions (Br-, NO3-, BF4-, SCN- e NTf2-) dos LI e o comportamento de agregação foi investigado através das técnicas de calorimetria exploratória diferencial (DSC), condutividade, tensão superficial, fluorescência e espalhamento de luz dinâmico (DLS). Na solução etanol em água (4,75%), os valores de concentração de agregação crítica (cac) (114 a 205 mM), energia livre de agregação (ΔG°a) ( 15 a 18 kJ/mol) e grau de ionização do contra-íon (α) (0,37 a 0,44) para os LI contendo os ânions Br-, NO3-, BF4-, SCN- diminuíram significativamente com o aumento da hidrofobicidade do ânion. Em etanol, os dados de cac (165 a 500 mM), ΔG°a ( 9 a 11 kJ/mol) para os LI com os ânions Br-, SCN- e NTf2- também diminuíram com o aumento do volume e hidrofobicidade dos ânions. Dados de energia livre de adsorção (ΔG°ads) (-35 a -39 kJ/mol) demonstraram que os LI dicatiônicos, de forma geral, possuem boa atividade tensoativa e esta propriedade aumenta com a diminuição das características hidrofóbicas dos ânions. Em geral, nos solventes utilizados no estudo, o raio hidrodinâmico (Rh) dos agregados variou entre 200 e 500 nm para todos os LI. Valores de parâmetro de empacotamento crítico (Pc) determinados a partir de dados de raios-X e tensão superficial indicaram que os agregados formados são micelares. Os dados de cac obtidos por condutividade, fluorescência e tensão superficial apresentaram-se de forma concordante. Observou-se que o aumento da hidrofobicidade da estrutura do ânion do LI dicatiônico favoreceu a formação dos agregados, enquanto que ânions menos hidrofóbicos melhoraram as propriedades tensoativas das estruturas dos LI.

Coordination chemistry usually applies to transition metals, but has recently been extended to the p-block elements. For the pnictogen atoms (group 15), this type of coordination chemistry has already been applied to antimony and bismuth, where they behave as Lewis acceptor centres. However, complexes with nitrogen and phosphorus as Lewis acidic centres are rare, due to their relatively small atomic radii and inherent basic nature. Instead, these elements (Pn(III)) are typically observed as donor centres because they are better at donating their electron pair, than they are at accepting them. To enhance the Lewis acidity at the phosphorus and nitrogen centres, a cationic charge can be introduced by heterolytically abstracting a halide and replacing it with a weakly coordinating anion, providing more opportunities for new reactivity. The presence of a stereochemically active lone pair at the acceptor site also introduces new reactivity patterns to be explored. The formation of these main group coordination complexes opens doors to potential applications in catalysis, small molecule activation, or as material precursors. 2,2’-bipyridine (bipy) has been a prototypical ligand used in transition metal coordination chemistry due to its high basicity and oxidative resistance. This property has been exploited to enable a comprehensive study of a series of Pn(III) tricationic and dicationic complexes using 2,2’-bipyridine (bipy); 4,4’-di-tert-butyl-2,2’-bipyridine (tBu2bipy); 4-dimethylaminopyridine (DMAP); and other main group containing ligands. / Graduate

The convergence of supramolecular and polymer sciences has led to the construction of analogs of traditional covalently-constructed polymeric structures and architectures by supramolecular methods. Host-guest complexations of polymers are also possible through well-defined synthesis of polymeric building blocks, for novel supramolecular polymers. Monotopic polymeric building blocks were synthesized by controlled radical polymerizations with a crown or paraquat initiator. The combinations of terminal and central functionalities of host and guest polymeric building blocks provided chain-extended and tri-armed homopolymers, and diblock and tri-armed copolymers. A supramolecular graft copolymer was formed from a main-chain poly(ester crown ether) and a paraquat terminated polystyrene. This comb-like copolymer was characterized by a large viscosity increase. A four-armed polystyrene-b-poly(n-butyl methacrylate) was synthesized from a pseudorotaxane macroinitiator derived from a complex of a crown-centered polystyrene and a dufunctional paraquat compound. A single peak with higher molecular weight from size exclusion chromatography proved the copolymer formation. Supramolecular interactions enhance the ionic conductivity of semi-crystalline ionic polymers; the ionic conductivity of a C₆-polyviologen and dibenzo-30-crown-10 mixture was 100 times higher than the polyviologen itself. However, ionic conductivities of amorphous polyviologens with polyethers were influenced only by glass transition temperature changes. New imidazolium ionic liquid monomers and imidazolium based polymers were synthesized for potential applications in electroactive devices, such as actuators. Structure-property relationships for pendant imidazolium polyacrylates and main-chain imidazolium polyesters were investigated. Terminal ethyleneoxy moeties enhanced ionic conduction 2~3 times; however, the alkyl chain length effect was negligible. For the imidazoium polyesters, higher ion conductivities result from 1) mono-imidazolium over bis-imidazolium, and 2) bis(trifluoromethanesulfonyl)imide polymers over hexafluorophosphate analogs. A semi-crystalline hexafluorophosphate polyester with C₁₀-sebacate-C₁₀, displayed 400-fold higher ionic conductivity than the amorphous C₆-sebacate-C₆ analogue, suggesting the formation of a biphasic morphology in the former polyester. New dicationic imidazolium salts have interesting features. 1,2-Bis[N-(N'-alkylimidazoilum)]ethane salts stack well in the solid state and possess multiple solid-solid phase transitions. They complex with dibenzo-24-crown-8 and a dibenzo-24-crown-8 based pyridyl cryptand with <i>K_a</i> = ~30 and 360 M¹, respectively. Some of these dicationic imidazolium salts have low entropies of fusion, typical of plastic crystals. These newly discovered imidazolium homopolymers have ionic conductivities up to 10⁴ (S cm⁻¹); however, better properties are still required. Well-designed block copolymers should provide both good electrical and mechanical properties from bicontinuous morphologies, such ion channels. / Ph. D.

Electrospray ionization mass spectrometry (ESI-MS) with induced collision energy was used to carry out a comprehensive study on the interaction energies between cations and anions of dicationic ionic liquids. The influence of the anion ([Br]-, [NO3]-, [BF4]-, [SCN]- and [Cl]-) and the size of alkyl chain (n = 4,6,8 and 10) in the interaction energy of ionic liquids derived from the 1, n-bis (3-methylimidazolyl-1-yl) alkane with n = 4,6,8 and 10, in the gas phase was investigated. Three experiments were carried out to determine the cation-anion interaction energy: (i) ESI-MS of binary (1:1) mixtures of ionic liquids with different anions or cations; (Ii) ESI-MS of ionic liquid individually with variation of the applied collision energy and determination of the center of mass energy (Ecm) using the relation between the intensity of the precursor ion and the sum of the ions; (iii) the rate of variation of the intensity of the precursor ion as a function of collision energy at different concentrations of all ionic liquids was obtained. From this correlation, the cation-anion dissociation constant of the dicationic ionic liquids was obtained. The results showed the appearance of mixed species (example: [Bis-C8(MIM)22XY]- and [C8(MIM)XY]-) in the binary mixtures. The application of the induced collision energy in the mixtures allowed estimating which anion interacts more effectively with the cation. Also for this experiments, the dicationic ionic liquids with the anions [Cl]-, [Br]- and [NO3]- presented higher cation-anion interaction energy. The increasing order of interaction energy was [BF4]- <[SCN]- <[NO3]- <[Br]- <[Cl]-. The Ecm values for ionic liquids with different anions did not indicate trends in the interaction energy in relation to structural factors such as ionic radius and molecular volume. Thus, for the anions, it was found that the interaction increases in the following order: [SCN]- <[Cl]- <[NO3]- <[Br]- <[BF4]-. On the other hand, increasing the size of the spacer alkyl chain caused an increase in cation-anion interaction energy. As the concentration of the ionic liquid increased, an increase in the precursor ion intensity was observed. / A espectrometria de massa com ionização por electrospray (ESI-MS) com energia de colisão induzida foi utilizada para realizar um estudo compreensivo sobre as energias de interação entre cátions e ânions de líquidos iônicos dicatiônicos. Foi avaliada a influência do ânion ([Br]-, [NO3]-, [BF4]-, [SCN]- e [Cl]-) e o tamanho da cadeia alquílica espaçadora (n=4,6,8 e 10) na energia de interação dos líquidos iônicos dicatiônicos, derivados do 1,n-bis(3-metilimidazolil-1-íneo)alcano em fase gasosa. Três experimentos foram realizados para a determinação da energia de interação cátion-ânion: (i) ESI-MS de misturas binárias (1:1) de líquidos iônicos com diferentes ânions ou cátions; (ii) ESI-MS de cada líquido iônico individualmente com variação da energia de colisão aplicada e determinação da energia de centro de massa (Ecm) usando a relação entre intensidade do íon precursor e somatório dos íons. (iii) Por fim, foi obtida a taxa de variação da intensidade do íon precursor em função energia de colisão de todos os líquidos iônicos. A partir desta correlação, foi obtida a constante de dissociação cátion-ânion dos líquidos iônicos dicatiônicos. Os resultados mostraram o aparecimento de espécies mistas (exemplo: [Bis-C8(MIM)22XY]- e [C8(MIM)XY]-) nos experimentos das misturas. A aplicação da energia de colisão induzida nas misturas também permitiu estimar qual ânion interage mais efetivamente com o cátion. Ainda para este experimentos, os líquidos iônicos dicatiônicos com os ânions [Cl]-, [Br]- e [NO3]- apresentaram maior energia de interação cátion-ânion. A escala em ordem crescente de energia de interação foi [BF4]-< [SCN]- < [NO3]- < [Br]- < [Cl]-. Os valores de Ecm para os líquidos iônicos com diferentes ânions não indicou tendências na energia de interação em relação fatores estruturais tais como raio iônico e volume molecular. Dessa forma, para os ânions, foi encontrado que a interação aumenta na seguinte ordem: [SCN]-<[Cl]-<[NO3]-<[Br]-<[BF4]-. Por outro lado, o aumento do tamanho da cadeia alquílica espaçadora causou um aumento na energia de interação cátion-ânion. Com o aumento da concentração do líquido iônico, foi observado um aumento na intensidade do íon precursor.

Les liquides ioniques à base de sels d’imidazolium sont une classe très importante de composés, compatibles avec de nombreuses réactions organiques et largement employés dans la synthèse organique en tant que solvants, catalyseurs ou ligands. En particulier, les liquides ioniques peuvent être récupérés à la fin de la réaction. Les sels d’imidazolium présentent également des propriétés d’organisation intéressantes, aussi bien en phase solide, liquide et en solution. Cependant, les liquides ioniques traditionnels présentent certains désavantages lorsqu’utilisés comme solvant dans des réactions intramoléculaires, surtout dans le cas où le réactif est apolaire. La faible solubilité de ce dernier dans le milieu ionique conduit à la formation des produits intermoléculaires. Les travaux présentés dans cette thèse portent sur l’utilisation des propriétés d’organisation des sels d’imidazolium, tout d’abord pour le développement des nouveaux cristaux liquides ioniques, comme le milieu réactionnel pour la réaction de Diels-Alder intramoléculaire, et ensuite pour la préparation des nanparticules d’or anisotropes. Dans un premier temps, le développement des sels d’imidazolium dicationiques portant des chaînes alkyles flexibles et un cœur rigide, avec des unités imidazolium attachées directement à un noyau naphthalène est rapporté. Par la suite, leurs propriétés thermiques et mésomorphes ont été étudiées. Ces sels sont stables thermiquement et forment une phase cristal liquide de type Smectique T, sur une plage de températures appropriées pour des réactions organiques. En utilisant le milieu cristal liquide comme milieu réactionnel dans la réaction de Diels-Alder, le réactif a été piégé dans la structure organisée de cette phase, ce qui a empêché l’interaction entre deux molecules de réactifs, limitant la formation du produit intermoléculaire. D’ailleurs, le milieu cristal liquide ionique a pu être récupéré et reutilisé à la fin de la réaction. Dans un deuxième temps, l’influence de la structure de la mésophase sur la réaction de Diels-Alder intramoléculaire a été étudiée. Des sels d’imidazolium tricationiques ayant une symétrie C3 ont ete développés dans le but d’obtenir des phases colonnaires. Ces sels possèdent un cœur rigide formé par trois cations imidazolium liés à un noyau benzène et des chaînes alkyles flexibles. Des études thermiques et mésomorphes sur ces composés ont été ensuite réalisées. Ces composés possèdent une haute stabilité thermique et forment une phase colonnaire rectangulaire, stable sur une large gamme de températures. L’influence de cette phase sur la réaction de Diels-Alder a ete étudiée. L’utilisation de la phase colonnaire favorise également la réaction intramoléculaire. En particulier, elle s’est avèree plus efficace que la phase Smectique T, probablement dû à sa structure plus organisée, indiquée par une enthalpie de tranisition cristal liquide – liquide isotrope plus élevée. Dans un dernier temps, nous nous sommes intéressés à l’utilisation des propriétés d’organisation des sels d’imidazolium dans la préparation des nanoparticules d’or anisotropes. Dans cette optique, différents mélanges binaires, composés d’un sel d’imidazolium et le diméthylformamide (DMF), ont été préparés et utilisés comme solvants et stabilisants, dans la synthèse des nanoparticules d’or à température ambiante. L’utilisation de ces milieux nous a permis d’obtenir des particules d’or avec différentes géométries. La forme des nanoparticules d’or obtenus dépend de la structure des sels d’imidazolium utilisés et de la concentration du mélange binaire, à la fois. / Ionic liquids based on imidazolium salts are an important class of compounds, possessing a very good compatibility with various organic reactions, and are widely used as solvents, catalysts and ligands in organic synthesis. Moreover, imidazolium salts possess interesting supramolecular organization in the solid, liquid and solution state. However, ionic liquids present some disadvantages when used as solvents for intramolecular reactions, especially in the case of apolar reactants. The low solubility of ionic compounds in ionic media promote the formation of intermolecular products. The main goal of the research presented in this thesis is to explore the supramolecular organization of imidazolium salts, first in the development of ionic liquid crystals as reaction media for intramolecular Diels-Alder reactions and secondly for the preparation of anisotropic gold nanoparticles. First, the development of dicationic imidazolium salts having a rigid core and flexible alkyl chains is reported. The rigid core is forned by direct attachment of two imidazoliums on a naphthalene moiety. Their thermal and mesomorphic analyses were then carried out. These dicationic salts show a high thermal stability and form a very ordered smectic T phase, over a wide range of temperatures. This mesophase was subsequently used as reaction medium for intramolecular Diels-Alder reactions. In this phase, reactants are trapped in the highly organized structure of the liquid crystal medium, limiting the formation of intermolecular products. Moreover, the ionic liquid crystal, was recoved at the end of reaction by simple extraction. Secondly, the influence of the mesophase’s structure on the Diels-Alder reaction was explored. Tricationic imidazolium satls having a C3 symmetry were developed in order to obtain columnar phases. The rigid core of these salts is composed of three imidazolium units directly attached to the benzene ring. Their thermal stabilities and mesomorphic properties were investigated. The columnar phase formed by these salts was then used as reaction media for Diels-Alder reactions, and it proved to be more efficient than the previously used smectic T phase, due to their more organized structure, as indicated by the higher enthalpy value of the liquid crystal - isotropic liquid transition. iv Finally, the supramolecular organization in solution of two imidazolium salts was explored with the aim to prepare anisotropic gold nanoparticles. Different binary mixtures composed of an imidazolium salt and dimethylformamide (DMF) were prepared and used both as solvent and capping agent in the synthesis of gold nanoparticles, at room temperature. The use of these binary mixture allowed us to synthesize nanoparticles with various geometries. The form of the gold nanoparticles prepared in these binary mixtures was influenced by both, the structre and the concentration of the imidazolium salt used.