When plants are exposed to multiple environmental stress factors, one form of stress can affect the response to another stress. This study used seedlings of a new cultivar of wheat(Triticum aestivum L. cv. 1862), grown under factorial combinations of two levels of ultraviolet-B (UV-B)radiation, two salinity regimes and two levels of iron treatment in chelator-buffered nutrient solutions in a growth chamber. A number of morphological and physiological measurements were made. The accumulation of chlorophyll, UVabsorbing compounds and proline in shoots, as well as phytosiderophores (PSs) in root exudates were measured. Feed value measurements included crude protein, water-soluble carbohydrates, acid detergent fibre and Fe in shoots and roots. After 21 days of stress exposure, results showed that Fe deficiency and NaCl stress generally decreased plant growth and function as well as nutritive value, but increased plant biochemical protection traits such as proline accumulation (16.3 fold under salinity stress) and release of PSs (2.4 fold under Fe deficiency). Interestingly, UV-B radiation affected belowground parameters, inducing a 47% reduction in PS release, together with decreasing root DM by 9% and Fe concentration in roots by 7%. When Fe deficiency and NaCl stress were combined, the results showed a decrease in PS release by 3.5 fold compared to unstressed plants. UV-B radiation synergistically increased UV-absorbing compound levels in combination with Fe deficiency, compared to plants grown under optimal Fe levels. This stress combination also resulted in a cumulative effect by decreasing Fe concentration in shoots and roots. However, salt stress did not interact with UV-B radiation for any of the traits measured. In addition, some three-way interactions were noted, with the Fe x NaCl x UV-B stress combination slightly decreasing PS release and resulting in a cumulative effect by decreasing Fe concentration in roots. In conclusion, this study found that aboveground stress factors such as UV-B can affect important aspects of belowground plant function, and that Fe deficiency can interact with UV-B and salinity stress in modifying plant responses to either stress alone.

The objectives of this project were to investigate the critical factors impacting the physicochemical and antibacterial properties of β-chitosan based films derived from jumbo squid (Dosidicus gigas) pens, and to evaluate the feasibility of improving water solubility of β-chitosan through Maillard reaction. The studies examined the effect of molecular weight (1,815 and 366 kDa), acid (formic, acetic, propionic, and lactic acid), and plasticizer (glycerol and sorbitol) on the film properties, as well as reducing sugar (fructose and glucosamine) and heat treatment (high temperature short time (HTST), low temperature long time (LTLT)) on water solubility of chitosan. Results on β-chitosan were compared with α-chitosan in both studies. Tensile strength (TS) and elongation (EL) of β-chitosan films were influenced by molecular weight (Mw), acid and plasticizer types (P < 0.05). High molecular weight (Hw) β-chitosan films had an overall TS of 44 MPa, 53% higher than that of low molecular weight (Lw) β-chitosan films (29 MPa) across all acid types used. The mean TS of β-chitosan acetate and propionate films (43 and 39 MPa) were higher (P < 0.05) than that of β-chitosan formate and lactate films (34 and 29 MPa). Films incorporated with plasticizer (32 MPa) had lower TS than those without plasticizer (48 MPa). Mean EL of Hw β-chitosan films was 10% versus approximately 4% in Lw β-chitosan films. Formate and acetate films had higher EL than that of propionate film. Glycerol and sorbitol increased (P < 0.001) EL 151% and 106% compared with the films without plasticizer, respectively. Water vapor permeability (WVP) of the films was affected by acid and plasticizer. Formate films (34 g mm/m² d KPa) had higher WVP than other acid films. Adding plasticizer increased (11% to 31%) WVP of propionate films except the Lw β-chitosan propionate film with sorbitol. The antibacterial activity of Lw β-chitosan and α-chitosan films delayed (P < 0.05) the proliferation of E. coli, where lactate films showed the strongest effect. The growth of L. innocua at 24 h was completely (P < 0.05) inhibited by chitosan films except Hw β-chitosan acetate film. A soft and cotton-like water soluble chitosan with mesopores was acquired after freeze-drying the Maillard reacted chitosan-sugar solution. The yield of β-chitosan-derivatives (8.48%) was 1.21 times higher than that of α-chitosan products (7.00%) (P < 0.01). Heat treatment only affected the yield of chitosan-glucosamine derivatives. Sugar type did not indicate any impact on the yield of the chitosan-derivative products in general (P > 0.05). The solubility was affected by sugar type (P < 0.01) only occurred in the β-chitosan products prepared with LTLT (P<0.05), where β-chitosan-fructose derivatives (9.56 g/L) had higher solubility than the glucosamine (5.19 g/L).LTLT treatment had given all chitosan-derivatives a higher solubility (8.44 g/L) than HTST (3.83 g/L) did (P<0.001). The results from this study demonstrated the feasibility of creating β-chitosan based film from jumbo squid pens with similar mechanical, water barrier and antibacterial properties compare to α-chitosan films as a food wrap and controlled the properties with several important factors, and developing water soluble chitosan through Maillard reaction that possess the potential as functional substance in a wider range of applications. / Graduation date: 2012

La apigenina (4', 5, 7 trihidroxiflavona), flavonoide presente en distintos vegetales, tiene numerosas características saludables por las cuales elegimos un derivado hidrosoluble, la apigenina potásica, para el presente estudio.Hemos estudiado su actividad frente a la inflamación aguda, al cáncer de próstata y a los daños causados por las radiaciones, tanto ionizantes como no ionizantes (radiación UV), utilizando diversas técnicas, tanto in vitro como en modelos in vivo. Este flavonoide demostró actividad antiinflamatoria, reduciendo la inflamación hasta un 78%. Asimismo, la apigenina potásica mostró actividad quimiopreventiva frente al cáncer de próstata, al reducir la viabilidad y la migración e inducir apoptosis in vitro, y aumentar la supervivencia de animales con tumores. Además, la apigenina potásica presentó efecto geno- y citoprotector frente a la radiación ionizante (radiación &#947; y X), con un factor de protección de un 27-35 % en linfocitos humanos, y de un 50-86 % en dos líneas celulares de próstata. Por último, el flavonoide ha demostrado proteger frente al fotoenvejecimiento causado por la radiación UV, reduciendo la displasia epitelial y la elastosis dérmica, dos marcadores de cáncer cutáneo; además, ha sido posible detectar la apigenina en diversos tejidos, entre ellos el cerebro. / Apigenin (4', 5, 7 trihidroxyflavone), a flavonoid present in different plants, shows some healthy characteristics for which a water soluble derivated, potassium apigenin, was chosen for this study.It has been studied the activity of potassium apigenin against acute inflammation, prostate cancer and the effect of ionising and non-ionising (UV) radiations, using different techniques, both in vitro and in vivo models.This flavonoid showed anti-inflammatory effects, inhibiting the inflammation by up to 78%. It also demonstrated chemopreventive activity against prostate cancer, by reducing the cell viability and migration, inducing apoptosis and increasing the animal survival. Moreover, potassium apigenin showed genoprotector and citoprotector effects against ionising radiation (radiation &#947; and X), with a protection factor of 27-35% in human lymphocytes and of 50-86% in two prostate cell lines. Finally, the flavonoid protected from the photoaging induced by UV radiation, diminishing epithelial dysplasia and dermal elastosis, two markers of skin cancer; furthermore, potassium apigenin was detected in some tissues, brain among them.

No description available.

A number of novel isoindoline nitroxides have been synthesised using a variety of synthetic techniques. Several carbon-carbon bond forming methodologies, including the first examples of Heck and Sonogashira coupling applied to the isoindoline nitroxide class, were utilised to give novel robust aromatic frameworks. Palladium-catalysed Heck coupling of brominated nitroxides and ester-substituted olefins generates novel nitroxides possessing extended conjugation. Hydrolysis of the nitroxide esters gave the corresponding carboxylic acids, which showed enhanced water solubility. Sonogashira coupling of an iodo-isoindoline nitroxide gave several novel alkynesubstituted nitroxides in high yield. Subsequent coupling of a deprotected ethynyl nitroxide with aromatic iodides gave acetylene-linked nitroxides and an acetylene linked nitroxide dimer. A butadiyne linked dinitroxide was successfully synthesised via Eglinton oxidative coupling of two ethynyl nitroxides. The synthesis of a novel water-soluble dicarboxy nitroxide was achieved by base hydrolysis of a dinitrile. Functional group interconversion furnished anhydride and imide substituted nitroxides from the diacid. Subjecting the imide to the Hofmann rearrangement gave an unexpected brominated amino-carboxy nitroxide. The dicarboxy nitroxide and the brominated amino-carboxy nitroxide were both shown to have a protective effect on Ataxia-Telangiectasia cells, indicating a possible role as antioxidants in the treatment of this disease. A fluorescein nitroxide was successfully synthesised through the condensation of the anhydride substituted nitroxide and resorcinol. After limited success using a variety of other techniques, Buchwald-Hartwig amination was able to furnish a rhodamine nitroxide, via a triflate-fluorescein nitroxide. The extended aromatic nitroxides possess suppressed fluorescence and we have described these systems as profluorescent. The profluorescent nitroxides were found to have significantly lower quantum yields than the non-radical analogues and displayed a substantial increase in fluorescence intensity upon radical trapping, making them useful probes for free radical reactions.

Obtaining enantio pure drug molecules is a long standing challenge in asymmetric synthesis implying that the identification of enantiomers and the determination of enantiomeric purity from a racemic mixture are of profound importance. In achieving this target NMR spectroscopy has proven to be an excellent analytical tool. It is well known that normal achiral NMR solvents do not distinguish the spectra of enantiomers. On the other hand, the conversion of substrates to diastereomers using one of the enantiopure chiral auxiliaries, such as, chiral solvating agent, chiral derivatizing agent and chiral lanthanide shift reagent, circumvents this problem. The imposition of diasteomeric interactions circumvents this problem. There is a pool of chiral auxiliaries available in the literature, each of which is specific to molecules of certain functionalities and has its own advantages and limitations. These classical methods have two limitations as they demand the presence of a targeted functional group in the chiral molecule and utilize only chemical shifts to visualize enantiomers. On the other hand in chiral anisotropic medium, due to differential ordering effect, the order-sensitive NMR observables, viz. chemical shift anisotropies (∆σi), dipolar couplings (Dij) and for nuclei with spin >1/2 the quadrupolar couplings (Qi) have enormous power of exhibiting different spectrum for each enantiomer permitting their discrimination. Numerous weakly ordered chiral aligning media have been reported in the literature. Nevertheless there is a scarcity of water compatible medium. Research work presented in this thesis is focused on various aspects, such as, the discovery of new chiral aligning medium for the enantiodiscrimination of water soluble chiral molecules, potential utility of DNA liquid crystal for discrimination of amino acids, on-the-fly monitoring of enzyme kinetics and the preparation of novel composite liquid crystals, hydrogels and thin films. The derived results are discussed in different chapters. Chapter 1 provides a brief introduction to NMR spectroscopy with special emphasis on the conceptual understanding of the tensorial interaction parameters, such as chemical shifts, scalar and dipolar couplings, quadrupolar couplings, effect of r.f pulses, basic introduction to 2D NMR experiments. Subsequently, a broad overview of the enantiomers, specification of their configurations, chirality without stereogenic carbon, chirality in molecules containing different atoms, are discussed. Following this a brief introduction to liquid crystals and their properties, their classification, their orientation in the magnetic field, order parameter are also discussed. The description on the chiral liquid crystals, the differential ordering effect, employment of the orientation dependent NMR interactions, utility of 2H NMR experiments for the visualization of enantiomers and the measurement of enantiomeric composition has been set out in brief. Chapter 2: As far as the organo soluble chiral molecules is concerned (in solvents such as, chloroform, dioxane, tetrahydrofuran and dimethylformamide), it has been well established that an ideal choice of chiral liquid crystal for enantiodiscrimination is poly-�-benzyl-L-glutamate (PBLG). Nevertheless, there is a scarcity of weak aligning medium for water soluble chiral molecules. This chapter introduces the chiral liquid crystal derived from the polysaccharide xanthan, which has numerous applications. The detailed discussion on the preparation of polysaccharide xanthan mesophase is given. The appearance of the mesophse is established by detecting the quadrupole split doublet of dissolved water. Subsequently enantiodiscrimination power of this new medium has been investigated on deuterated D/L-Alanine and (R/S)-β-butyrolactone. For such a purpose the selective 2D-SERF (SElective ReFocussing) experiment has been employed. It has been convincingly demonstrated that the medium has wide applicability for the discrimination of enantiomers, enantiotopic directions in prochiral molecules, measurement of enantiomeric excess and the RDCs in medium sized molecules. The new medium is sustainable over a wide range of temperature and concentration of ingredients, the mesophase is reversible, reproducible, easy to prepare besides being cost effective. It is possible to have the controlled tuning of the degree of order for specific application. Chapter 3: In this chapter the real discriminatory potential of DNA liquid crystalline phase has been explored. It is unambiguously established that; i) the fragmented DNA liquid crystal is able to differentiate between enantiomers of structurally different chiral amino acids; ii) the T1 (2H) values for L/D (alanine) is nearly equal indicating the similar dynamics for both the enantiomers, thus permitting the measurement of ee from the integral areas of the peaks of the contours of 2D spectrum; iii) the enantiotopic discrimination in prochiral compounds has also been successfully explored. Furthermore the analyses of NMR results yielded fruitful information on the analytical potential of DNA chiral liquid crystal, such as, (a) the chiral discrimination is effective on a large range of amino acids with spectral differences ΔΔʋQ‘s and ΔʋQ‘s varying from 80 to 338 Hz, and 50 to 900 Hz respectively; (b) the discrimination phenomenon remain active irrespective of the structure and the electronic nature (polarity) of the fourth substituent around the stereogenic center; (c) compared to an alkyl moiety, the presence of a terminal –OH or –SH group seems to slightly increase both the degree of alignment of the solute and the enantiodiscrimination efficiency compared to alanine; (d) The enantiodiscrimination can be detected easily not only on CD3 and CD groups, but also on CD2 sites exhibiting inequivalent diastereotopic directions; (e) discriminations with rather large differential ordering effect were obtained even for the sites that are situated far away from the asymmetric center; (f) The relative position of quadrupolar doublets from one 2H site to another can be reversed with regard to the absolute configuration (L/D). Chapter 4: Racemases recognize a chiral substrate such as (L-Alanine) and convert it into its enantiomer, i.e., (D-Alanine) and vice versa. Alanine racemase plays a vital role for certain bacteria, providing D-Alanine for peptidoglycan cell-wall biosynthesis. Elucidating the mechanism of enzymatic racemization is crucial for designing new inhibitors that may be useful as a novel class of antibiotics. This requires techniques to discriminate L-and D-Alanine and follow their concentrations as a function of time, so that one can determine the kinetic parameters and study the effect of inhibitors. In this chapter the utility of DNA liquid crystal media for in situ and real-time monitoring of the interconversion of L-and D-alanine-d3 by alanine racemase from Bacillus stearothermophilus has been demonstrated. The enantiomeric excess has been measured at different time intervals to monitor the enzymatic racemization at different time intervals in pseudo 2D NMR. The study unambiguously ascertains the reliability and robustness of utility of NMR in chiral anisotropic phase for monitoring the enzymatic racemization. The method thus provides new mechanistic insight and a better understanding of enzymatic reactions, in particular for alanine racemase. Chapter 5: In continuation with the development of weakly ordered liquid crystals, this chapter reports the spontaneous formation of composite graphene oxide (GO)/double stranded DNA (dsDNA) liquid crystals at higher concentrations of ingredients, and hydrogels at lower concentrations of ingredients, the process of which involves simple mixing in an aqueous phase has been demonstrated. The liquid crystalline phases and hydrogels have been characterized using optical polarized microscopy (OPM), scanning electron microscopy (SEM), Raman spectroscopy and 2H NMR spectroscopy. The observation of strong birefringence in the optical polarized microscope gives evidence for the formation of GO/dsDNA liquid crystals. The strong interaction between the dsDNA and GO was confirmed using Raman spectroscopic analysis. Furthermore, GO/dsDNA thin films have also been prepared and characterized using SEM and OPM. The GO/dsDNA thin film was prepared and its liquid crystal nature was established using OPM and 2H NMR. Importantly, the GO/dsDNA hydrogels were formed without any heat treatment to unwind dsDNA molecules and the porosity of hydrogels can be controlled by changing concentration of the dsDNA. This novel multifunctional composite liquid crystals and hydrogels of GO/dsDNA thus opens up new avenues for many applications like security papers, optical devices such as circular polarizers, reflective displays and drug delivery as well as tissue engineering using GO composite hydrogels.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-04T10:15:18Z No. of bitstreams: 2 Dissertação - André Luiz Borges Machado - 2017.pdf: 4018960 bytes, checksum: 0f752eee89eafe0cb8606742dc6901b7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-04T10:15:52Z (GMT) No. of bitstreams: 2 Dissertação - André Luiz Borges Machado - 2017.pdf: 4018960 bytes, checksum: 0f752eee89eafe0cb8606742dc6901b7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-04-04T10:15:52Z (GMT). No. of bitstreams: 2 Dissertação - André Luiz Borges Machado - 2017.pdf: 4018960 bytes, checksum: 0f752eee89eafe0cb8606742dc6901b7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Brazil nut (Bertholletia excelsa) and Macadamia (Macadamia integrifolia) are rich feeds with excellent nutrients with higher quality. The main form of consumption of these nuts and almonds are in natura, but there are products which can be elaborated using these raw materials with high nutritional value and pleasant flavor. Water-soluble extracts are an alternative to consume them, which consist of fluid food of plant origin, that can be produced by nuts, oleaginous and even some grasses and they have great commercial appeal since they are free of animal’s fats, “lac free” (free of lactose) and have high rate of minerals. Thus, this research aimed to determine the best formulation, to accompany physical and microbiological stability, proximal composition, to estimate the shelf life and to determine the rheological behavior of a water-soluble extract made of Brazil nut and Macadamia. For the construction of mathematical models, with the purpose of knowing the effect of the variation of water, Brazil nut and Macadamia concentrations, basic components in the elaboration of the product on the proximal composition and physical aspects such as pH, titratable acidity and colorimetry, a simplex centroid design for mixtures was used and provided quadratic and cubic models showing excellent adjustment of experimental data. The Global Acceptance and Purchase Intention tests were performed for each experiment proposed by simplex centroid design and the Tukey test was used in order to determine the best proportion among the components of the ternary mixture. The formulation of water-soluble extract composed of 70% (w/w) water, 15% (w / w) Brazilian nut and 15% (w/w) Macadamia was considered to be the most preferred by tasters submitted to the sensory evaluations. In order to improve the product’s flavor, 10% (w/v) of sugar, expressed as sucrose, was added and the concentration of preservatives citric acid, potassium sorbate and sodium benzoate was reduced. The product was processed technologically under hygienic conditions and filled in 220 ml transparent glass bottles, hermetically sealed with metal crown cork, pasteurized at 80 °C/25 min, stored under refrigeration at 4 ° C and had its stability evaluated during 28 days. Growth of Thermotolerant Coliforms, Positive Coagulase Staphylococci, Salmonella sp, Molds and Yeasts during the evaluation period was not detected. There was a significant variation (p < 0.05) in pH in the first two weeks of storage, and remained without significant variation (p > 0.05) for the other weeks analyzed. The acidity remained constant throughout the lifetime. The product showed a yellowish-white color throughout the study, determined by the coordinates of the colorimetry. Sensory analysis scores for odor, color, taste and global impression averaged around 6, thus, concluding that the product has a 28 days of shelf life. The rheological profile of the beverage was evaluated at three different temperatures, at 25 °C (room temperature), at 45 °C (temperature of the disintegration stage of Brazil nut and Macadamia with water in blender), and at 80 °C, (pasteurization temperature). The Ostwald-de-Waele model was considered the best to describe the beverage flow and since the calculated flow rate of the model, was less than 1 at the temperatures studied, it had concluded that the beverage behaved as a fluid Non-Newtonian pseudoplastic. The apparent viscosity curves of the mixed drink were plotted and showed that the apparent viscosity decreased significantly (p < 0.05) with the increasing of temperature. / A Castanha-do-Brasil (Bertholletia excelsa) e a Macadâmia (Macadamia integrifolia) são alimentos ricos em nutrientes de excelente qualidade. A principal forma de consumo de nozes e amêndoas é in natura, porém existem produtos que podem ser elaborados a partir destas matérias-primas com alto valor nutricional e também de sabor agradável. Uma alternativa ao consumo desses alimentos são os extratos hidrossolúveis, que consistem em alimentos fluidos de origem vegetal que podem ser produzidos a partir de castanhas, oleaginosas e até mesmo algumas gramíneas e possuem grande apelo comercial, uma vez que são isentos de gorduras animais, não possuem lactose e apresentam alto teor de minerais. Sendo assim, esta pesquisa objetivou determinar a melhor formulação, acompanhar a estabilidade física e microbiológica, composição proximal, estimar a vida útil e determinar o comportamento reológico de um extrato hidrossolúvel a base de Castanha-do-Brasil e Macadâmia. Para a construção de modelos matemáticos, com a finalidade de se conhecer o efeito da variação das concentrações de água, Castanha-do-Brasil e Macadâmia, dos componentes básicos na elaboração do produto sobre a composição proximal e aspectos físicos como pH, acidez titulável e colorimetria, utilizou-se o planejamento experimental para misturas tipo simplex centroide que forneceu modelos quadráticos e cúbicos com excelente ajuste frente aos dados experimentais. Os Testes de Aceitação Global e Intenção de Compra foram realizados para cada experimento proposto pelo planejamento simplex centroide e o teste de Tukey foi utilizado a fim de determinar a melhor proporção entre os componentes da mistura ternária. A formulação de extrato hidrossolúvel composta por 70% (p/p) de água, 15% (p/p) de Castanha-do-Brasil e 15% (p/p) de Macadâmia, foi considerada como a mais preferida pelos provadores submetidos as avaliações sensoriais. Com a finalidade de melhorar o sabor do produto, adicionou-se 10% (p/v) de açúcar, expressos em sacarose, e reduziu-se a concentração dos conservantes ácido cítrico, sorbato de potássio e benzoato de sódio. O produto foi processado tecnologicamente sob condições higiênicas, sendo envasado em garrafas de vidro transparente de 220 mL, fechado hermeticamente com tampas metálicas do tipo coroa, pasteurizado a 80 °C/25 min, armazenado sob refrigeração a 4 °C e teve sua estabilidade avaliada por 28 dias. Não foi detectado o crescimento de Coliformes Termotolerantes, Estafilococos Coagulase Positiva, Salmonella sp, Bolores e Leveduras durante o período de avaliação. Houve variação significativa (p < 0,05) do pH nas duas primeiras semanas de estocagem, estabilizando-se para as demais semanas analisadas. A acidez se manteve constante durante todo o período de vida útil. O produto apresentou coloração branco-amarelada durante todo o estudo, determinada pelas coordenadas da colorimetria. As notas das análises sensoriais para Odor, Cor, Sabor e Impressão Global tiveram média em torno de 6, concluindo assim que o produto tem vida útil de, pelo menos, 28 dias. Foi avaliado o perfil reológico da bebida em três temperaturas distintas, a 25 ºC (temperatura ambiente), a 45 ºC, (temperatura da etapa de desintegração da Castanha-do-Brasil e Macadâmia com a água em liquidificador), e a 80 ºC, (temperatura de pasteurização). O modelo de Ostwald-de-Waele foi considerado o melhor para descrever o escoamento da bebida e uma vez que o índice de escoamento calculado do modelo foi menor que 1, nas temperaturas estudadas, conclui-se que a bebida comportou-se como um fluido não newtoniano pseudoplástico. As curvas de viscosidade aparente da bebida mista foram plotadas e mostram que a viscosidade aparente diminuiu significativamente (p < 0,05) com o aumento da temperatura.

Biological systems construct varieties of self-assembled architectures with incredible elegance and precession utilizing proteins as subunits to accomplish widespread functions. Inspired by natural systems, construction of artificial model systems with such sophistication and delicacy has become an intriguing field of research over the last two decades using so-called self-assembly process. Judiciously selected complementary building units encoded with specific chemical and structural information can be self-assembled into pre-programmed abiological architectures in a manner similar to biological self-assembly. In this regard, kinetically labile metal-ligand coordination has become an efficient and powerful protocol for the construction of highly intricate structures with specific topology and functionality due to its simple design principle, high bond enthalpy, and predictable directionality. Two-component self-assembly is very widely used methodology and easy to monitor. Recently, multi-component self-assembly has come up as an alternative and effective pathway to achieve complex architectures connecting more than two components in a single step. However, formation of selective single product from multicomponents is entropically unfavorable. Only a very few 3D architectures have been known, that are obtained from a mixture of ditopic and tri- or tetratopic donors with metal acceptors with or without employing templates. Development of template-free multicomponent architectures is still in its infancy. Strong tendency of Pd(II)/Pt(II) to attain square-planar geometry around the metal center and kinetically labile nature of Pd(II)/Pd(II)-N(pyridine) bonds made them chemists’ favourite to engineer desired supramolecular coordination architectures with structural resemblance to Platonic or Archimedean solids by employing symmetrical pyridyl donors due to their predictable directionality. In case of poly-imidazole donors, free rotation of C-N bond connecting imidazole and phenyl ring allows various dispositions of the donating nitrogen with respect to the aromatic backbone, and therefore, the structural topology of the architectures, made of poly-imidazole ligands becomes much more interesting as compared to symmetrical Platonic or Archimedean solids. The physico-chemical properties of self-assembled coordination cages depend on the structures of the complexes. Presence of large internal cavity surrounded by aromatic core, provides an excellent environment for the encapsulation of varieties of guest molecule or as nano-reactors for different organic transformations. Structural investigation in terms of packing interactions, solvent molecules, intermolecular channels can sometimes determine the property of such self-assembled materials as well. Presence of acidic water as well as H-bonded 3D-networks of water molecules in molecular pockets make them potential material for proton conduction. In addition, metal-ligand coordination offers opportunity to introduce new functionality through pre-synthetic modification of the building constituents to influence the property of the supramolecular systems. Incorporation of unsaturated ethynyl functionality attached to the heavy transition metal is expected to exhibit efficient luminescence due to the facile metal to ligand charge transfer (MLCT). Hence, the final assemblies can be employed as chemosensors for electron-deficient nitroaromatics, which are the chemical signature of many of the commercially available explosives. The present investigation is focused on design and construction of discrete, nanoscopic coordination cages with unusual structural topology employing mainly imidazole-based donors with Pd(II)/Pt(II) acceptors and their applications in catalysis, chemosensing, and proton conduction. CHAPTER 1 of the thesis provides a general introduction to self-assembly focusing on the importance and advantages of metal-ligand directional bonding approach towards the construction of supramolecular architectures with various structural topologies. This chapter also includes a brief review on the applications of such coordination cages in various fields especially as ‘molecular flask’ for the observation of unique chemical phenomena and unusual reactions. Part A of CHAPTER 2 describes the synthesis of a new hollow Pd6 water soluble cage [{(tmen)Pd}6(timb)4](NO3)12 (1) via two-component self-assembly of a triimidazole donor and 90° Pd(II) acceptor [tmen = N,N,N’,N’-tetramethylethylenediamine, timb = 1,3,5-tris(1-imidazolyl)benzene]. The assembly was successfully crystallized with a hydrophilic dianionic benzoquinone derivative (formed in situ by the decomposition of DDQ) as [{(tmen)Pd}6(timb)4](NO3)10()2(H2O)18 (3), and a hydrophobic sterically demanding aromatic aldehyde as [{(tmen)Pd}6(timb)4](NO3)12{()4a}2(H2O)27 (5a) [where 2H2 = 2,3-dichloro-5,6-dihydroxycyclohexa-2,5diene-1,4-dione, 4a = 1-pyrenecarboxaldehyde,  = exohedral and  = endohedral] to confirm the hydrophobic nature of the cavity. Experiments were carried out to show that the hydrophobic confined nanospace of the cage (1) catalyses the Knoevenagel condensation of a series of different aromatic monoaldehydes with active methylene compounds in ‘green’ aqueous medium. The Knoevenagel condensation reaction is basically a dehydration reaction because water is a by-product. So the presence of water should, in principle, promote the backward reaction as per Le Chatelier’s principle. In general, these reactions with organic substrates are not performed in water. However, difficulty has been overcome using hydrophobic cavity of the cage. It has also been established that the cavity of the cage also enhances the rate of Diels-Alder reaction of 9-hydroxymethylanthracene with N-phenylmaleimide/N-cyclohexylmaleimide. Figure 1. Catalytic Knoevenagel condensation and Diels-Alder reaction using hydrophobic cavity of the cage (1) in aqueous medium. Part B of CHAPTER 2 reports unique three-component self-assembly incorporating both tri- and tetra-topic donors. Until now, a very few 3D-architectures have been known that are obtained from self-assembly of ditopic and tri- or tetratopic donors with metal acceptors. Scheme 1. Three-component self-assembly of a Pd7 cage (1) from cis-blocked Pd(II) 90° acceptor (M), tri-imidazole (timb) and tetra-imidazole (tim) donors. Self-assembled multicomponent discrete architecture composed of both tri- and tetra-topic donors is yet to be reported due to difficulty in prediction of the final structure from the mixture of ligands having multiple donor sites. The first example of self-sorted Pd7 molecular boat [{(tmen)Pd}7(timb)2(tim)2](NO3)14(H2O)20 (1) [tmen = N,N,N’,N’-tetramethylethylenediamine, timb = 1,3,5-tris(1-imidazolyl)-benzene, tim = 1,2,4,5-tetrakis(1-imidazolyl)benzene] was synthesized via three-component self-assembly of cis-(tmen)Pd(NO3)2, tetra- (tim) and tri-topic donors (timb) in a 7:2:2 ratio. The cavity of this cage was also utilized as a nanoreactor for catalytic Knoevenagel condensations of a series of aromatic aldehydes with 1,3-dimethylbarbituric acid (e) and Meldrum’s acid (f) in aqueous media. CHAPTER 3 presents the results of an investigation on how simple variation of length and coordination mode of linear donors can self-discriminate into markedly different complex architectures, from Pd8 molecular swing [{(tmen)Pd}8(tim)2(bpy)4](NO3)16 (1) or [{(tmen)Pd}8(tim)2(stt)5](NO3)6 (2) to Pd6 molecular boat [{(tmen)Pd}6(tim)2(bpe/dpe/pin/dpb)2](NO3)12, (3/4/5/6). Also by enhancing denticity [bidentate to tridentate (ptp)] as well as introducing asymmetry, they self-sort into Pd7 molecular tent [{(tmen)Pd}7(tim)2(ptp)2](NO3)14 (7) by employing it in a self-assembly of cis-(tmen)Pd(NO3)2 and tetraimidazole (tim) donor [where tmen = N,N,N’,N’-tetramethylethylenediamine, bpy = 4,4’-bipyridyl, stt = sodium terephthalate, bpe = trans-1,2-bis(4-pyridyl)ethylene, dpe = 1,2-di(pyridin-4-yl)ethane, pin = N-(pyridin-4-yl)isonicotinamide, dpb = 1,4-di(pyridin-4-yl)benzene, ptp = 6'-(pyridin-4-yl)-3,4':2',4''-terpyridine, and tim = 1,2,4,5-tetrakis(1- imidazolyl)benzene]. In these cases, control of the geometrical principles and stereo-electronic preferences of the building units allowed the formation of such intricate architectures. Some of these assemblies represent first examples of such types of structures, and their formation would not be anticipated by taking into account only the geometry of the donor and acceptor building units. In addition to their direct structural confirmation using single crystal X-ray diffraction analysis, propensity of the assemblies (1 and 3) to form inclusion complexes with large guest like C60 in solution was also demonstrated by fluorescence quenching experiment. The high KSV values for both the assemblies 1 (1.0 × 10-5 M-1) and 2 (1.6 × 10-6 M-1) with C60 indicated the propensity of these assemblies to form complexes with C60 in solution. Furthermore, inspection of crystal packing of other five complexes (2 and 4 - 7) revealed the presence of water molecules H-bonded with NO3– (O-H···O=N) and 3D H-bonded networks of water in the intermolecular pockets. Interestingly, the present complexes (2 and 4 - 7) show high conductivity across low-humidity range at ambient temperature and achieve a conductivity of ~10-3 Scm-1 at 75% relative humidity and 296 K. These supra-molecular architectures represent a new generation of discrete materials that display high proton conductivity under ambient conditions with activation energy comparable to that of Nafion. Scheme 2. Exclusive formation of Pd8 molecular swings (1 and 2), Pd6 molecular boats (3-6), and Pd7 molecular tent (7) via self-sorting. CHAPTER 4 presents self-selection by synergistic effect of morphological information and coordination ability of the ligands through specific coordination interactional algorithms within dynamic supramolecular systems involving a tetratopic Pd(II) acceptor and three different pyridine- and imidazole-based donors (La - Lc) [La = 1,3-bis((E)-2-(pyridin-3-yl)vinyl)benzene, Lb = 1,3-di(1H-imidazol-1-yl)benzene, and Lc = tris(4-(1H-imidazol-1-yl)phenyl)amine]. Three different cages, ‘paddle wheel’ cluster Pd2(La)4(NO3)4 (2a), molecular barrel Pd3(Lb)6(NO3)6 (2b) and molecular sphere Pd6(Lc)8(NO3)12 (2c) were first synthesized via two-component self-assembly of a tetratopic Pd(II) acceptor (1) and individual pyridine- and imidazole-based donors (La - Lc). When all the four components were allowed to interact in a complex reaction mixture, only one out of three cages was isolated. The inherent dynamic nature of the kinetically labile coordination bond allows constitutional adaptation through component exchange in the competition experiment involving multiple constituents to self-organize into specific combination and thereby, achieve the thermodynamically most stable assembly. The preferential binding affinity towards a particular partner was also established by transforming a non-preferred cage to a preferred cage by the interaction with the appropriate ligand and thus, this represents the first examples of two-step cage-to-cage transformation through constitutional evolution of Figure 2. Cage-to-cage transformation from non-preferred cage to preferred cage upon treatment with appropriate ligand; and Nyquist plots of the complexes (2b and 2c) under 98% RH condition and ambient temparature. dynamic systems induced by both coordination ability and geometry of the ligand. Moreover, computational study further supported the fact that coordination interaction of imidazole moiety to Pd(II) is enthalpically more preferred compared to pyridine which drives the selection process. In addition, analysis of crystal packing of both the complexes (2b and 2c) indicated the presence of strong H-bonds between NO3- and water molecules; as well as H-bonded 3D-networks of water. Interestingly, both the complexes exhibit promising proton conductivity (10-5 to ca. 10-3 S cm-1) at ambient temperature under relative humidity of ~98% with low activation energy. CHAPTER 5 covers design and synthesis of new organometallic building block 1,3,5-tris(4-trans-Pt(PEt3)2I(ethynyl)phenyl)benzene (1) incorporating Pt-ethynyl functionality and [2 + 3] self-assembly of its nitrate analogue 1,3,5-tris(4-trans-Pt(PEt3)2(ONO2)(ethynyl)phenyl)benzene (2) with “clip” type bidentate donors (L1 – L3) separately afforded three trigonal prismatic architectures (3a – 3c), respectively (Scheme 3), Scheme 3. Schematic presentation of three different donors (L1 – L3) and a new planar tritopic acceptor (2) and their [3 + 2] self-assembly into trigonal prismatic architectures (3a - 3c). [L1 = N1,N3-di(pyridin-3-yl)isophthalamide; L2 = 1,3-bis((E)-2-(pyridin-3-yl)vinyl)benzene; L3 = 1,3-bis(pyridin-3-ylethynyl)benzene]. All these prisms were characterized and their shapes/sizes are predicted through geometry optimization employing molecular mechanics universal force field (MMUFF) simulation. The extended -conjugation including the presence of Pt-ethynyl functionality make them electron rich as well as luminescent in nature. As expected, cages 3b and 3c exhibit fluorescent quenching in solution upon addition of picric acid [PA], which is a common constituent of many explosives. Interestingly, the non-responsive nature of fluorescent intensity towards other electron-deficient nitro-aromatic explosives (NAEs) makes them promising selective sensors for PA with a detection limit deep down to ppb. Complexes 3b – c represent the first examples of molecular metallocages as selective sensors for picric acid. Furthermore, solid-state quenching of fluorescent intensity of the thin film of 3b upon exposure to saturated vapor of picric acid draws special attention for infield application.

La chimie des foldamères est un domaine de recherche en pleine expansion où les chimistes explorent la construction d’architectures artificielles variées mimant les structures repliées des biopolymères naturels. Les foldamères d’oligoamides quinoline, constituent une branche importante des foldamères montrant de nombreuses caractéristiques attractives, incluant la stabilité et la prédictibilité de leurs conformations repliées, qui en font de bons candidats pour des applications biologiques. Jusqu’à présent, la plupart des études sur les foldamères d’oligoamides quinolines ont été menées dans des solvants organiques. Cette thèse a pour objectif d’étendre leur portée au milieu aqueux et présente plusieurs méthodologies pour parvenir à leur solubilité, leur repliement, la variation de leurs chaines latérales, leur agrégation et leur capacité à former des cristaux dans l’eau.Tout d’abord, une méthode de synthèse en phase solide a été développée permettant l’accès rapide aux foldamères hybrides α-amino acide/quinoline (X/Q). Leur étude dans l’eau montre que contrairement aux foldamères hybrides de type (XQ)n, ceux de type (XQ2)n sont capables d’adopter une conformation hélicoïdale présentant un alignement des chaines α-amino acides dans l’espace. Ensuite, plusieurs chaines latérales courtes ont été identifiées pour doter les foldamères aromatiques d’une solubilité et d’une capacité à cristalliser dans l’eau. Six oligoamides quinoline ont ainsi été synthétisés pour une étude modèle. Des cristaux ont été obtenus pour toutes les séquences sauf une, présentant une excessive solubilité dans l’eau. Enfin, des efforts ont été faits pour construire des faisceaux d’hélices auto-assemblés dans l’eau à base d’effets hydrophobes et d’interactions électrostatiques. Les études RMN et cristallographiques ont indiqué que les effets hydrophobes étaient plus faibles qu’attendu et ne provoquaient pas d’agrégation forte. / Foldamer chemistry is a rapidly expanding research field where chemists explore the construction of various artificial architectures that mimic the folded structures of biopolymers found in nature. Quinoline oligoamide foldamers, as an important branch of foldamers, have been shown to possess many desirable features, including stability and predictability of their folded conformations, and are promising candidates to achieve biological applications. Up to now, most investigations of quinoline oligoamide foldamers have been carried out in organic solvents. This thesis is aimed to expand their scope in aqueous medium and presents several methodologies to achieve solubility, folding, side-chain variation, aggregation and crystal growth ability in water.First, a solid phase synthesis method was developed to enable the fast access to α-amino acid/quinoline (X/Q) hybrid oligoamide foldamers. The study of these hybrid foldamers in water showed that contrary to (XQ)n-type foldamers the (XQ2)n-type foldamers could adopt aromatic helical conformations with α-amino acid side chains aligned in space. Then, several short side chains were identified to endow aromatic foldamers with both solubility in, and crystal growth ability from water. Six quinoline oligoamides displaying these side chains were synthesized as a case study. Crystals were obtained from aqueous medium in all cases but one, exceedingly soluble in water. At last, efforts were made to construct self-assembled aromatic helix bundles in water based on hydrophobic effects and electrostatic interactions. NMR and crystallographic studies indicated that hydrophobic effects are weaker than expected and not strongly conducive of aggregation.

>Magister Scientiae - MSc / In this study PbSe quantum dots (QDs) were successfully synthesized via the organometallic and aqueous routes. Optical characterization was carried out using photoluminescence (PL) spectroscopy, structural and morphological characterization were carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy (EDS) was used to determine the composition of the QDs. All the synthesized QDs were found to have emissions within the near-infrared region of the spectrum (≥1000 nm) with most of them being less than 5 nm in size. The aqueous synthesized QDs had a perfect Gaussian emission spectrum with a FWHM of ~23 nm indicating pure band gap emission and narrow size distribution respectively. The QDs were determined to have a cubic rock-salt crystal structure consistent with bulk PbSe. The aqueous synthesized QDs were however not stable in solution with the QDs precipitating after approximately 48 h. The organometallic synthesized QDs were transferred into the aqueous phase by exchanging the surface oleic acid ligands with 11-mercaptoundecanoic acid ligands. The ligand exchanged QDs were however stable in solution for over two weeks. The effects of reaction parameters on the optical and structural properties of the organometallic synthesized QDs were investigated by varying the reaction time, temperature, ligand purity, lead and selenium sources. It was observed that larger QDs were formed with longer reaction times, with reactions proceeding faster at higher reaction temperatures than at lower temperatures. Varying the ligand purity was found to have minimal effects on the properties of the synthesized QDs. The lead and selenium sources contributed largely to the properties of the QDs with lead oxide producing spherical QDs which were smaller compared to the cubic QDs produced from lead acetate. TBPSe was seen to produce smaller QDs as compared to TOPSe. The cytotoxity of the synthesized QDs was determined following the WST-1 cell viability assay with the QDs being found to be non-toxic at all the tested concentrations