Cumarinas são metabólitos secundários de plantas encontrados majoritariamente nas espécies das famílias Asteraceae, Rutaceae e Umbeliferae. Quimicamente, são compostos fenólicos, formados pela fusão de um benzeno e de um anel α-pirona, chamados de benzopironas. Elas apresentam diversas propriedades farmacológicas, associadas com baixa toxicidade. Nosso grupo de pesquisa sintetiza cumarinas pela reação de Pechmann, que ocorre através da condensação de um fenol com um β-cetoéster, na presença de um ácido de Bronsted ou Lewis. Um dos trabalhos mais recentes foi a síntese de 6-metil-4-clorometilcumarinas com um IC50 menor do que 1,6 μM para atividade antitripanocida. Em outro trabalho, um grupo de compostos de híbridos cumarina-triazol foi sintetizado e apresentou potencial atividade como agente antitumoral. Baseado nesses trabalhos, foi planejado a síntese de análogos da 6-metil-4-clorometilcumarina via condensação de Pechmann, com diferentes substituintes na posição 6, obtidos através das reações de click chemistry, no intuito de aumentar a atividade antioxidante desses compostos. Assim, para obter esses compostos, foi realizada uma condensação de Pechmann com hidroquinona e 4-cloroacetoacetato de etila. Após, uma eterificação de Williamson com brometo de propargila foi feita. Finalmente, a reação de click chemistry foi realizada sob irradiação de micro-ondas com diversas azidas previamente sintetizadas no laboratório, conduzindo à obtenção de diversos análogos da 6-metil-clorometilcumarina que foram avaliados quanto a viabilidade celular através ensaio do MTT (brometo de 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazólio). Também foi testada a sua capacidade antioxidante pelo método do DCFH-DA (diacetato de 2’,7’ –diidroclorofluoresceína). Dessa maneira, sob as condições reacionais utilizadas neste trabalho, foi possível sintetizar 12 compostos inéditos com rendimentos entre 9 e 61%. Os ensaios biológicos preliminares indicaram que os compostos sintetizados apresentam potencial atividade antioxidante e algumas moléculas tiveram potencialidade como agente citotóxico. / Coumarins are secondary plant metabolites typically found in species of the Asteraceae, Rutaceae and Umbeliferae families that demonstrate diverse pharmacological properties associated with low toxicity to humans. Chemically, they are phenolic compounds characterized by the fusion of benzene with an α-pyrone ring, yielding the benzopyrone nucleus. Our research group usually synthesizes coumarins by the Pechmann reaction, through the condensation of phenols with β-ketoesters catalyzed by Bronsted or Lewis acids. One of the most recent works performed at our laboratory describes the synthesis of 6-methyl-4-chloromethylcoumarins with an IC50 of 1.6 μM concerning the anti-trypanocidal activity. Another work described the syntheses of coumarin-triazole hybrids with potential activity as anticancer agents. Based on the previous works, it was designed the synthesis of 4-chloromethylcoumarins via Pechmann condensation with several substituents at the position 6 of the coumarin ring through click chemistry reactions to improve their antioxidant activities. The synthesis of the coumarins started with Pechmann condensation using hydroquinone and ethyl 4-chloroaceacetate followed by functionalization of the phenolic hydroxyl with propargyl bromide via Williamsom ether synthesis. Subsequently, the click chemistry reactions were performed under microwave irradiation using different organic azides previously synthesized at our laboratory, yielding several 6-substituted-4-chloromethylcoumarin analogues which were evaluated for cell viability through MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Their antioxidant capacity was also tested by the DCFH-DA (2’,7’–diihydrochlorofluorescin diacetate) method. Therefore, under the reaction conditions used in this study, it was possible to synthesize 12 novel compounds with yields between 9 and 61%. Preliminary biological assays indicated that the compounds synthesized have potential antioxidant activity and some molecules had potential as an antitumor agent.

Cumarinas são metabólitos secundários de plantas encontrados majoritariamente nas espécies das famílias Asteraceae, Rutaceae e Umbeliferae. Quimicamente, são compostos fenólicos, formados pela fusão de um benzeno e de um anel α-pirona, chamados de benzopironas. Elas apresentam diversas propriedades farmacológicas, associadas com baixa toxicidade. Nosso grupo de pesquisa sintetiza cumarinas pela reação de Pechmann, que ocorre através da condensação de um fenol com um β-cetoéster, na presença de um ácido de Bronsted ou Lewis. Um dos trabalhos mais recentes foi a síntese de 6-metil-4-clorometilcumarinas com um IC50 menor do que 1,6 μM para atividade antitripanocida. Em outro trabalho, um grupo de compostos de híbridos cumarina-triazol foi sintetizado e apresentou potencial atividade como agente antitumoral. Baseado nesses trabalhos, foi planejado a síntese de análogos da 6-metil-4-clorometilcumarina via condensação de Pechmann, com diferentes substituintes na posição 6, obtidos através das reações de click chemistry, no intuito de aumentar a atividade antioxidante desses compostos. Assim, para obter esses compostos, foi realizada uma condensação de Pechmann com hidroquinona e 4-cloroacetoacetato de etila. Após, uma eterificação de Williamson com brometo de propargila foi feita. Finalmente, a reação de click chemistry foi realizada sob irradiação de micro-ondas com diversas azidas previamente sintetizadas no laboratório, conduzindo à obtenção de diversos análogos da 6-metil-clorometilcumarina que foram avaliados quanto a viabilidade celular através ensaio do MTT (brometo de 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazólio). Também foi testada a sua capacidade antioxidante pelo método do DCFH-DA (diacetato de 2’,7’ –diidroclorofluoresceína). Dessa maneira, sob as condições reacionais utilizadas neste trabalho, foi possível sintetizar 12 compostos inéditos com rendimentos entre 9 e 61%. Os ensaios biológicos preliminares indicaram que os compostos sintetizados apresentam potencial atividade antioxidante e algumas moléculas tiveram potencialidade como agente citotóxico. / Coumarins are secondary plant metabolites typically found in species of the Asteraceae, Rutaceae and Umbeliferae families that demonstrate diverse pharmacological properties associated with low toxicity to humans. Chemically, they are phenolic compounds characterized by the fusion of benzene with an α-pyrone ring, yielding the benzopyrone nucleus. Our research group usually synthesizes coumarins by the Pechmann reaction, through the condensation of phenols with β-ketoesters catalyzed by Bronsted or Lewis acids. One of the most recent works performed at our laboratory describes the synthesis of 6-methyl-4-chloromethylcoumarins with an IC50 of 1.6 μM concerning the anti-trypanocidal activity. Another work described the syntheses of coumarin-triazole hybrids with potential activity as anticancer agents. Based on the previous works, it was designed the synthesis of 4-chloromethylcoumarins via Pechmann condensation with several substituents at the position 6 of the coumarin ring through click chemistry reactions to improve their antioxidant activities. The synthesis of the coumarins started with Pechmann condensation using hydroquinone and ethyl 4-chloroaceacetate followed by functionalization of the phenolic hydroxyl with propargyl bromide via Williamsom ether synthesis. Subsequently, the click chemistry reactions were performed under microwave irradiation using different organic azides previously synthesized at our laboratory, yielding several 6-substituted-4-chloromethylcoumarin analogues which were evaluated for cell viability through MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Their antioxidant capacity was also tested by the DCFH-DA (2’,7’–diihydrochlorofluorescin diacetate) method. Therefore, under the reaction conditions used in this study, it was possible to synthesize 12 novel compounds with yields between 9 and 61%. Preliminary biological assays indicated that the compounds synthesized have potential antioxidant activity and some molecules had potential as an antitumor agent.

Cumarinas são metabólitos secundários de plantas encontrados majoritariamente nas espécies das famílias Asteraceae, Rutaceae e Umbeliferae. Quimicamente, são compostos fenólicos, formados pela fusão de um benzeno e de um anel α-pirona, chamados de benzopironas. Elas apresentam diversas propriedades farmacológicas, associadas com baixa toxicidade. Nosso grupo de pesquisa sintetiza cumarinas pela reação de Pechmann, que ocorre através da condensação de um fenol com um β-cetoéster, na presença de um ácido de Bronsted ou Lewis. Um dos trabalhos mais recentes foi a síntese de 6-metil-4-clorometilcumarinas com um IC50 menor do que 1,6 μM para atividade antitripanocida. Em outro trabalho, um grupo de compostos de híbridos cumarina-triazol foi sintetizado e apresentou potencial atividade como agente antitumoral. Baseado nesses trabalhos, foi planejado a síntese de análogos da 6-metil-4-clorometilcumarina via condensação de Pechmann, com diferentes substituintes na posição 6, obtidos através das reações de click chemistry, no intuito de aumentar a atividade antioxidante desses compostos. Assim, para obter esses compostos, foi realizada uma condensação de Pechmann com hidroquinona e 4-cloroacetoacetato de etila. Após, uma eterificação de Williamson com brometo de propargila foi feita. Finalmente, a reação de click chemistry foi realizada sob irradiação de micro-ondas com diversas azidas previamente sintetizadas no laboratório, conduzindo à obtenção de diversos análogos da 6-metil-clorometilcumarina que foram avaliados quanto a viabilidade celular através ensaio do MTT (brometo de 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazólio). Também foi testada a sua capacidade antioxidante pelo método do DCFH-DA (diacetato de 2’,7’ –diidroclorofluoresceína). Dessa maneira, sob as condições reacionais utilizadas neste trabalho, foi possível sintetizar 12 compostos inéditos com rendimentos entre 9 e 61%. Os ensaios biológicos preliminares indicaram que os compostos sintetizados apresentam potencial atividade antioxidante e algumas moléculas tiveram potencialidade como agente citotóxico. / Coumarins are secondary plant metabolites typically found in species of the Asteraceae, Rutaceae and Umbeliferae families that demonstrate diverse pharmacological properties associated with low toxicity to humans. Chemically, they are phenolic compounds characterized by the fusion of benzene with an α-pyrone ring, yielding the benzopyrone nucleus. Our research group usually synthesizes coumarins by the Pechmann reaction, through the condensation of phenols with β-ketoesters catalyzed by Bronsted or Lewis acids. One of the most recent works performed at our laboratory describes the synthesis of 6-methyl-4-chloromethylcoumarins with an IC50 of 1.6 μM concerning the anti-trypanocidal activity. Another work described the syntheses of coumarin-triazole hybrids with potential activity as anticancer agents. Based on the previous works, it was designed the synthesis of 4-chloromethylcoumarins via Pechmann condensation with several substituents at the position 6 of the coumarin ring through click chemistry reactions to improve their antioxidant activities. The synthesis of the coumarins started with Pechmann condensation using hydroquinone and ethyl 4-chloroaceacetate followed by functionalization of the phenolic hydroxyl with propargyl bromide via Williamsom ether synthesis. Subsequently, the click chemistry reactions were performed under microwave irradiation using different organic azides previously synthesized at our laboratory, yielding several 6-substituted-4-chloromethylcoumarin analogues which were evaluated for cell viability through MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Their antioxidant capacity was also tested by the DCFH-DA (2’,7’–diihydrochlorofluorescin diacetate) method. Therefore, under the reaction conditions used in this study, it was possible to synthesize 12 novel compounds with yields between 9 and 61%. Preliminary biological assays indicated that the compounds synthesized have potential antioxidant activity and some molecules had potential as an antitumor agent.

No description available.

The recycling of materials from waste electrical and electronic equipment (WEEE) is of great concern today, as increasing public awareness and the implementation of recent legislations have created a situation where industries need to 1) comply with the environmental regulations and 2) fulfil producers’ responsibility initiatives. In this context, the work described in this thesis investigates the applications of new leaching solvents, the ionic liquids (ILs), to recycle two materials, copper and decabromodiphenylether (DBDE), which are common in WEEE. A total of 18 ILs, methylimidazolium (MIM) and methylpyridinium (MPy) based, were prepared using a microwave-assisted method. These ILs were selected to allow characterisation of performance with respect to three parameters: hydrophobicity of the cation, polarity of a terminal functional group in the cation side chain, and the type of aromatic ring, in order to identify their effects on the solubility and extraction processes. All ILs were successfully characterised by IR spectroscopy, mass spectrometry and NMR. Hydrophobicity was measured by HPLC, and the retention factors compared to logP values predicted from Molinspiration. High correlation (>88%) was observed, which indicated that the predicted logP values were representative of the real hydrophobicity of the cation. Copper metal was not significantly dissolved in any of the ILs, and performance was therefore assessed with the dissolution of CuO. The dissolution tests were conducted at 70°C for ten minutes and the resultant solutions analysed for Cu by using atomic absorption spectroscopy. A short side chain and the presence of a strongly polarised functional group at the terminal position were required to achieve maximum dissolution. Furthermore, the short chain methylimidazolium system was better than methylpyridinium for dissolving CuO. Consequently, 1-(2-cyanoethyl)-1-methylimidazloium bromide was found to be the best solvent and dissolved 75.5 mg of Cu in one g of IL. High impact polystyrene (HIPS), containing 4.4% of DBDE, was prepared in order to test the extraction abilities of various non-substituted ILs. The extraction of DBDE from the polymer was conducted at 90°C for 2 h 45 min. The results indicated that high hydrophobicity was required to achieve the maximum extraction of DBDE, however, the percentage extraction remained very low (<10%). The low extraction was attributed to the fact that only the DBDE present on the outer surface of the polymer was extracted during the process. In spite of being more hydrophobic, MPy-based systems did not dissolve as much as MIM-based systems because they were more viscous. The high viscosity value actually hindered the diffusion process and ultimately reduced the extraction of DBDE. The effects of different factors on the extraction process were evaluated and the maximum extraction was achieved by using 1-octyl-3-methylimidazolium bromide at 110 °C. The results described in this thesis have identified and quantified the link between the structures of the ILs and extraction efficiencies in relation to their potential use for recovery of CuO and DBDE from WEEE. The recommendations for future work have also been identified. The results obtained in this work, however, have contributed to increase the knowledge about the properties of ILs and can be used in future research to design a large scale recycling process.

Les synthèses de polymérisation assistées par micro-ondes sont reconnues pour réduire les temps de chauffe et améliorer des rendements en comparaison à celles effectuées sous chauffage conventionnel. Cette technique étant limitée par la profondeur de pénétration des micro-ondes, un dispositif millifluidique en continu couplé à l’irradiation micro-onde a été développé et étudié. Dans ce travail, une étude des réactions de polymérisation et de copolymérisation d’un couple de monomères (acide acrylique et styrène sulfonate de sodium) a été réalisée. Ces polymères ont été synthétisés par polymérisation radicalaire en réacteur discontinu ouvert sous chauffage conventionnel et sous irradiation micro-ondes dans un premier temps. Dans une seconde partie, ces polymères ont été synthétisés dans un dispositif millifluidique sous chauffage conventionnel et sous irradiation micro-onde. Enfin une dernière partie concerne l’étude de ces synthèses en millifluidique micro-ondes, pour cela un nouveau dispositif, associant micro-ondes et procédé fluidique, a été développé. Un nouvel outil de lecture de la température a été mis en place et l’utilisation d’une sonde chimique interne a été validée. Des synthèses de (co)polymères ont été réalisées et les résultats en termes de cinétiques comparés aux systèmes précédents. / Assisted microwave polymerization syntheses are known to reduce heating time and to improve yields as compared to the syntheses conducted under conventional heating methods. Nevertheless, this technique is limited by the penetration depth of microwaves. Within this work, a millifluidic device coupled to the microwaves irradiation has been developed and studied.Polymerization and copolymerization reactions of both monomers, acid acrylic and sulfonated styrene, were carried out. First, these polymers were synthesized by radical polymerization in a batch reactor under conventional heating and under microwaves irradiation. Secondly, these polymers have been synthesized and compared in a millifluidic device under conventional heating and under microwave irradiation. At last, a specific device has been developed to do the polymerization in millifluidic condition and under microwaves irradiation. A new tool for reading the temperature inside this system was implemented and the use of a chemical probe was validated. (Co)polymers have been obtained and the results, especially in terms of kinetics, have been compared to the above systems.

Carbon supported PtNi nanoparticles were prepared by hydrazine reduction of Pt and Ni precursor salts under different conditions, namely by conventional heating (PtNi-1), by prolonged reaction at room temperature (PtNi-2) and by microwave assisted reduction (PtNi-3). The nanocomposites were characterized by XRD, EDX, XPS and TEM and used as electrocatalysts in direct methanol fuel cell (DMFC) reactions. Investigations into the mechanism of PtNi nanoparticle formation revealed that platinum nanoparticle seeding was essential for the formation of the bimetallic nanoparticles. The average particle size of PtNi prepared by microwave irradiation was the lowest, in the range of 2.9 – 5.8 nm. The relative rates of electrooxidation of methanol at room temperature as measured by cyclic voltammetry showed an inverse relationship between catalytic activity and particle size in the following order PtNi-1 < PtNi-2 < PtNi-3. / Singapore-MIT Alliance (SMA)

Lithium-ion batteries are being intensely pursued as energy storage devices because they provide higher energy and power densities compared to other battery systems such as lead-acid and nickel-metal hydride batteries. This dissertation (i) explores the use of a low-temperature microwave-assisted synthesis process to obtain aliovalently-doped lithium transition-metal phosphates and lower-valent vanadium oxide spinels, some of which are difficult to obtain by conventional high-temperature processes, and (ii) presents an investigation of the electrochemical properties of the aliovantly-doped phosphate cathodes and doped lithium manganese oxide and oxyfluoride spinel cathodes in lithium-ion batteries. Following the introduction and general experimental procedures, respectively, in Chapters 1 and 2, Chapter 3 first focuses on understanding of how the inductive effect and structural features in lithium transition-metal borate, silicate, and phosphate cathodes affect the M²⁺ʹ³⁺redox energies. It is found that the magnitude of the voltages delivered by the polyanion cathodes can be predicted based simply on the coordination of the transition-metal ion. Furthermore, the differences in the voltages delivered by the phosphates and pyrophosphates are explained by considering the resonance structures and their contribution to the covalency of the polyanion. Chapter 4 presents a low-temperature microwave-assisted solvothermal process to substitute 20 atom % V³⁺ for Mn²⁺ in LiMnPO₄. It is shown that the solubility of vanadium in LiMnPO₄ decreases upon heating the doped samples to ≥ 575 °C, demonstrating the importance of employing a low-temperature process to achieve aliovalent doping in LiMnPO₄. It is further demonstrated that by increasing the vanadium content in the material, the discharge capacity in the first cycle could be increased without any additional carbon coating. Subsequent X-ray absorption spectroscopy data reveal that the better performance is facilitated by enhanced Mn-O hybridization upon incorporating vanadium into the lattice. Chapter 5 explores the influence of various factors, such as the oxidation state of Mn, electronegativity of the dopant cation Mn+, and the dissociation energy of M-O bond, on the electrochemical properties of cation-doped oxide and oxyfluoride spinel cathodes. As an extension, Chapter 6 presents the effect of processing conditions on the surface concentration of the dopant cation Mn+. Chapter 7 presents an extension of the low-temperature microwave-assisted synthesis process to obtain AV₂O₄ (Mg, Fe, Mn, and Co) spinel oxides. The method is remarkably effective in reducing the synthesis time and energy use due to the efficiency of dielectric heating compared to conventional heating. The ability to access V³⁺ is facilitated by the relative positions of the energy levels of the cations in solution, which is lower than that in the solid, and the use of a strong reducing solvent like TEG. Finally, Chapter 8 provides a summary of the salient findings in this dissertation. / text

Abstract The synthesis of α-hydroxy aldehydes and hydroxymethyl ketones as well as their interconversion to each other are discussed in this thesis. The literature survey of the monograph reviews the synthetic methods for the preparation of 1,2-bifunctionalized hydroxy aldehydes and ketones. The keto-aldehyde isomerisation reaction catalyzed by Triosephosphate isomerase enzyme (TIM) and organic compounds that interact with the TIM are also introduced. In addition, the microwave heating techniques in organic syntheses are reviewed. The practical work consists of two entities: The synthesis of new substrate candidates and transition state analogues for a mutated monomeric TIM. These compounds are model compounds for the catalytic activity and the structural studies of the mutated monomeric TIM. The synthesis of the sulphonyl α-hydroxy ketone-based substrate candidates consists of four successive syntheses. The microwave-activation was utilized in the preparation of a carbon-sulphur bond and the synthesis of hydroxymethyl ketones. The improved synthesis of the terminal α-hydroxy ketone functionality with microwave activation is presented. The formation of charged compounds was utilized to improve the absorption of microwave energy of reaction mixtures. The design and the synthetic work were carried out in accordance to principles of green chemistry. The second part of the practical work is the development of an organocatalytic α-oxybenzoylation reaction of aldehydes with high enantiomeric selectivity. This novel method generated enantiomerically pure α-hydroxy aldehydes in the stable benzoate-protected form from achiral starting materials under mild conditions at the presence of air and moisture.

Interest in rare-earth-doped crystalline materials, e.g., M(RE)F4 (M – alkali metal, RE – rare-earth metal), featuring unique optical properties such as light upconversion and downshifting is experiencing a surge due to the broad spectrum of applications that these photonic systems are facilitating. The development of reliable synthetic methods that grant rapid access to these materials is therefore of great importance. Microwave-assisted synthesis is appealing in this regard, because microwave radiation enables rapid and uniform heating of the reaction mixture and allows for rigid control of the reaction conditions, factors that facilitate the production of high-quality materials within minutes. Surprisingly, the investigation around microwave-assisted synthesis of M(RE)F4 materials featuring upconversion and downshifting luminescence is limited. Methods that have already been developed predominately target Na-based systems, despite the evidence that the Li-based analogues also display excellent optical properties. In fact, only a single microwave-assisted approach toward a nanoscale Li-based system has been reported to date, while to my knowledge, no report of a microwave-assisted synthesis of a microscale Li-based system existed prior to the commencement of the work presented in this thesis. The challenge lies in the fact that access to Li(RE)F4 is not easily achieved through a simple substitution of the alkali metal source in the established protocols that yield Na(RE)F4; rather, a complete re-optimization of the synthesis method is required. This particular challenge was successfully addressed in this work. Presented and discussed in Chapter 3 of this thesis is a rapid microwave-assisted solvothermal synthesis approach toward both upconverting and downshifting LiYF4:RE3+ microparticle systems. More specifically, it is detailed how the rigorous optimization of the reaction temperature/duration profile, initial reaction mixture pH, and ratio of the metal precursors was necessary in gaining control over the crystalline phase, morphology, and size of the microparticles under microwave-induced solvothermal conditions. Importantly, a materials growth mechanism involving the depletion of a Li-free crystal phase, followed by a particle ripening process is also proposed. Moreover, the versatility of the developed method is highlighted by showcasing how it can be extended toward the synthesis of other relevant Li- and Na-based M(RE)F4 nano- and microscale materials (i.e., LiYbF4, NaYF4, and NaGdF4) featuring upconversion luminescence. Lastly, potential challenges associated with microwave-assisted synthesis are discussed, and appropriate solutions are proposed. The upconversion and downshifting luminescence of the M(RE)F4 materials attained via the developed synthesis approach is investigated in Chapter 4. The first part of the chapter provides a general assessment of the characteristic luminescence generated by the M(RE)F4 materials featuring various RE3+ dopant systems. The second part of the chapter is devoted to a much more thorough single-particle investigation of the anisotropic luminescence behaviour exhibited by the LiYF4:RE3+ microparticles via hyperspectral imaging, polarized emission spectroscopy, and optical trapping. It is my hope that you, the reader, will find the work presented in this thesis stimulating from two vantage points – from the development of the most rapid microwave-assisted solvothermal synthesis of upconverting and downshifting M(RE)F4 nano/microscale materials reported to date, as well as from the utilization of specialized luminescence characterization techniques to provide fundamental insight into a seldom-considered luminescence property of crystalline materials such as LiYF4.