A strategy based on reticulating metal ions and organic ligands into atomically precise gold and silver nanoclusters (NCs) with high monodispersity has been advanced to a point that allows the design of NCs with strict stoichiometries, functionalities and valence. Of the Ag NCs discovered, Ag44 is the most studied, not only due to its high absorption that transcends the visible spectrum suitable for photovoltaics but also because of its long excited state lifetime, as revealed by nanosecond transient absorption spectroscopy. A major principle discovered in this dissertation is the ability to produce Ag44 in scalable amounts and with high stability in addition to modulation of the functional groups of the organic ligands via a fast and complete ligand exchange process. This new discovery has led to the development of synthetic designs in which new sizes were obtained by varying the reaction parameters (e.g., ligands functionality, reaction temperature and time), namely, Ag29 using dithiols and phosphines. The synthesized NCs possess tetravalent functionalities that facilitate their crystallization and characterization. Furthermore, Ag29 glows red and is therefore a possible candidate for sensing and imaging applications.

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Ca2RuO4 is a structurally-driven Mott insulator with a metal-insulator (MI) transition at TMI = 357K, followed by a well-separated antiferromagnetic order at TN = 110 K. Slightly substituting Ru with a 3d transition metal ion M effectively shifts TMI and induces exotic magnetic behavior below TN. Moreover, M doping for Ru produces negative thermal expansion in Ca2Ru1-xMxO4 (M = Cr, Mn, Fe or Cu); the lattice volume expands on cooling with a total volume expansion ratio reaching as high as 1%. The onset of the negative thermal expansion closely tracks TMI and TN, sharply contrasting classic negative thermal expansion that shows no relevance to electronic properties. In addition, the observed negative thermal expansion occurs near room temperature and extends over a wide temperature interval. These findings underscores new physics driven by a complex interplay between orbital, spin and lattice degrees of freedom. These materials constitute a new class of Negative Thermal Expansion (NTE) materials with novel electronic and magnetic functions.

Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2017-02-16T16:22:40Z No. of bitstreams: 1 DissBCDO.pdf: 4309058 bytes, checksum: 4f5cf3d0dbedd0e22b67ee37cbc653e9 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-03-13T18:12:23Z (GMT) No. of bitstreams: 1 DissBCDO.pdf: 4309058 bytes, checksum: 4f5cf3d0dbedd0e22b67ee37cbc653e9 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-03-13T18:12:35Z (GMT) No. of bitstreams: 1 DissBCDO.pdf: 4309058 bytes, checksum: 4f5cf3d0dbedd0e22b67ee37cbc653e9 (MD5) / Made available in DSpace on 2017-03-13T18:20:51Z (GMT). No. of bitstreams: 1 DissBCDO.pdf: 4309058 bytes, checksum: 4f5cf3d0dbedd0e22b67ee37cbc653e9 (MD5) Previous issue date: 2015-09-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Pharmaceutical cocrystals are multicomponent crystalline solids comprised of an active pharmaceutical ingredient (API) and one or more co-formers interacting through hydrogen bonding or other weak interactions like the π-stack and van der Waals interactions. Fluconazole (FLZ) is a triazole antifungal drug used in the treatment and prevention of superficial and systemic fungal infections. It is also used to prevent and treat meningitis. Cocrystallization is an alternative approach for enhancement of drug. It can be performed using neat grinding, solvent assisted grinding, solvent evaporation, cooling evaporation and slurry cocrystallization. In this work, a new cocrystal Fluconazol-Fumaric acid monohydrate was synthesized via 1:1 stoichiometric amount of FLZ and FUM at different conditions. The characterization of the synthesized cocrystals was achieved using Raman spectroscopy, differential scanning calorimetry, powder X-ray diffraction and single crystal X-ray diffraction. The results obtained for the characterization of the samples showed some obvious differences among the spectra, diffractograms and thermograms. The single crystal X-ray diffraction analysis of the new structure shows a cocrystal where the fluconazole molecules are attached to the fumaric acid and water molecules respectively through hydrogen bonds, gave unique cell dimensions for an assumed structure C17H18F2N6O6 with a space group of P21/n, a = 17.053(3) Å, b = 5.5995(10), c=21.154(3), α = 90°, β=105.418(4)°, γ= 90°, V = 1947.3(6) Å3. This work is the first to report a monohydrate cocrystal structure of fluconazole and fumaric acid. / Cocristais farmacêuticos são sólidos cristalinos multi-componentes compostos de um ingrediente ativo farmacêutico (API) e um ou mais co-formadores interagindo através de ligações de hidrogênio ou outras interações fracas como as π-stack e Van der Waals. Fluconazol (FLZ), é um fármaco anti-fúngico triazol utilizado no tratamento e prevenção de infecções fúngicas superficiais e sistémicas. É também utilizado para prevenir e tratar a meningite. Cocristalização é uma abordagem alternativa para melhorar as propriedades de fármacos. Pode ser realizada através de moagem a seco, moagem assistida por solvente, evaporação de solvente e cristalização em suspensão. Neste trabalho, um novo co-cristal Fluconazol-Ácido Fumarico monohidrato foi sintetizado utilizando uma estequimetria 1:1 em diferentes condições. A caracterização dos co-cristais sintetizados foi realizada utilizando espectroscopia Raman, calorimetria exploratória diferencial, difração de raios-X em pó é por monocristal. Os resultados obtidos para a caracterização das amostras mostrou algumas diferenças obvias entre os espectros, difratogramas e termogramas. A difração de raios-X de monocristal mostrou uma nova estrutura onde as moléculas de fluconazol estão ligadas ao ácido fumárico e a uma molécula de água através de ligações de hidrogênio, originando uma estrutura única C17H18F2N6O6 de grupo espacial P21/n e dimensões da célula unitária a = 17.053(3) Å, b = 5.5995(10), c=21.154(3), α = 90°, β=105.418(4)°, γ= 90°, V = 1947.3(6) Å3. Este trabalho é o primeiro a relatar uma estrutura de co-cristal mono-hidrato de fluconazol e acido fumárico.