Made available in DSpace on 2014-06-12T23:15:42Z (GMT). No. of bitstreams: 2 arquivo9254_1.pdf: 4805695 bytes, checksum: 02281e49f866827939f01754c06d0680 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2007 / Desde a sua concepção em 1994, o modelo Sparkle vinha sendo utilizado apenas para o cálculo das geometrias do estado fundamental de complexos de Eu(III). Nesta tese, apresentamos os modelos Sparkle/AM1 e Sparkle/PM3 que podem ser considerados um novo paradigma para o cálculo químico quântico de complexos de lantanídeos, uma vez que as parametrizações de ambos os modelos, para todos os íons lantanídeos trivalentes, foram realizadas de uma maneira muito mais robusta, com o propósito de gerar modelos capazes de gerar resultados muito mais exatos. No processo de parametrização destes modelos, dois aspectos são de fundamental importância: (i) a escolha de um conjunto de treinamento capaz de representar bem o nosso universo de 670 estruturas de complexos de lantanídeos e (ii) a escolha de uma função resposta capaz de possibilitar a reprodução satisfatória das propriedades de interesse, que no nosso caso foram comprimentos e ângulos de ligação envolvendo o íon metálico. Durante o procedimento de parametrização do modelo Sparkle/AM1 para o íon Eu(III), o primeiro dos lantanídeos a ser parametrizado, inúmeros testes foram realizados e cada termo da função resposta foi exaustivamente analisado até que conseguíssemos encontrar um conjunto de parâmetros que tornasse o nosso método realmente robusto. Com o mesmo procedimento utilizado na obtenção dos parâmetros do íon Eu(III), nós parametrizamos os modelos Sparkle/AM1 e Sparkle/PM3 para todos os outros ions lantanídeos trivalentes. A análise dos resultados mostrou que ambos os modelos Sparkle/AM1 e Sparkle/PM3 apresentaram erros médios absolutos igual a 0,07 Å para o cálculo das distâncias lantanídeo átomo ligante, que são as distâncias utilizadas nos estudos de campo ligante e no cálculo de propriedades luminescentes de tais complexos. Também investigamos a capacidade de predição do poliedro de coordenação de complexos de lantanídeos usando metodologias ab initio/ECP. Nossos resultados indicam que, ao contrário do que seria de esperar, a metodologia RHF/STO-3G/ECP aparece como sendo a mais eficiente em reproduzir o poliedro de coordenação de estruturas cristalográficas de complexos de lantanídeos. Alem disso, o aumento do nível de correlação (RHF, B3LYP, MP2-full) e/ou o aumento da função de base geralmente piora a exatidão da geometria do poliedro de coordenação de complexos de lantanídeos. Também observamos que os modelos Sparkle/AM1 e Sparkle/PM3 apresentam exatidão no cálculo do poliedro de coordenação desses complexos igual ou superior à apresentada pela metodologia ab initio que levou aos melhores resultados. No entanto, vale ressaltar que os modelos Sparkle são centenas de vezes mais rápidos em termos computacionais

Sparkle is a visual texture which appearance basically consists of very bright spots randomly distributed over a darker background. The effect is more apparent to the observer when one of the contributors (sample, observer, illumination) is moved, meaning it is a dynamic effect. While the characterization and measurement of sparkle has been an important topic of research during the past years, the focus has been solely around the static component of it, the dynamic aspect of sparkle has been left out of the discussion. This is somewhat reasonable since the dynamic attribute bases itself on the perception and measurement of static sparkle. The dynamic aspect of sparkle, or “living sparkle” can be described as the variation of its appearance over a given angular distance. Nonetheless, both effects are without doubt related and perhaps together they provide the key to finding the absolute characterization of sparkle. In this work we aim to dive into both aspects. First, the setup of a goniometric system with a color camera was carried out, obtaining a high spatial and angular resolution. Second, measurements of commercial and self-manufactured sample sets were performed, and an analysis algorithm was developed. The algorithm provided a wide range of parameters for different thresholding methods. These methods were put to test when the results were correlated with the visual assessment of a group of 9 samples under one illumination/observation geometry, obtaining the correlation factors for all methods and parameters. The combination of thresholding method and parameter obtained an R2 > 0.9, implying a strong connection with the visual experience. The threshold applied was always fixed at the same value and the parameter (“S_Values”) represented the brightness of the pixels, indicating that the brightness of the sample is the most influential attribute for the perception of sparkle. Then, this same methodology was applied to the rest of the samples in this study (71 total), for the geometries in between 71.2 and 11.2 degrees in 5 degrees steps. The physical parameters of the self-manufactured samples were also used to test the correctness of the algorithm. The results broadly matched the expected values of intensity and particle size. In addition, the algorithm measured the angular variability of the samples though the angular visibility of the sparkle spots. The wider the visible range, the more invariant the sample, and the less apparent the sparkle effect. This work proposes an innovative way of measuring sparkle in its dynamic and static components, a methodology and measurands to do so are proposed and contrasted to visually assessed samples.

Made available in DSpace on 2014-06-12T23:01:48Z (GMT). No. of bitstreams: 2 arquivo9200_1.pdf: 2609414 bytes, checksum: f2aac836702c7d45007a2262925fdb0a (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2006 / As sínteses de novos éteres-coroa, com grupos sulfóxido, foram testadas visando suas aplicações como ligantes em compostos de coordenação com íons lantanídeos. As estruturas dos éteres-coroa e de seus complexos com o Eu3+ foram obtidas com o método SMLC/AM1. Os resultados para a complexação foram favoráveis para os seguintes compostos: 2,3,11,12-dibenzo-1,4,10,13-tetraoxa-7,16-ditia-ciclooctadeca- 2,11-dieno-7,16- dióxido (dibenzo-18-coroa-4-7,16-(SO)2) e o 1,4,10,13-tetraoxa-7,16- ditia-ciclooctadecano-7,16-dióxido (18-coroa-4-7,16-(SO)2). Para um terceiro ligante, 2,4,12,14-dibenzo-1,5,11,15-tetraoxa-8,18-ditia-cicloeico-2,12-dieno-8,18-dióxido (dibenzo- 20-coroa-4-8,18-(SO)2) , sua complexação com Eu3+ não foi favorável devido a limitações estruturais. As metodologias de sínteses destes ligantes foram adaptadas de métodos descritos na literatura para sistemas similares, sendo observado que essas condições não foram favoráveis para a formação dos macrociclos desejados contendo grupos sulfóxido. Apenas o produto 2,3-benzo-1,4-dioxa-7-tia-ciclononano-2-eno-7-óxido (benzo-9-coroa-2-7-(SO)) foi obtido em rendimento de aproximadamente 10%, sendo que a confirmação de sua estrutura ainda requer alguns experimentos. O desenvolvimento de metodologias mais específicas para a preparação desses compostos se faz necessário, uma vez que o tamanho da cavidade do éter coroa pode ser controlado pelas condições reacionais. A modelagem molecular para o éter coroa obtido sugere que este pode formar um complexo com o Eu3+ na proporção de 1:2 de Eu3+ e ligante, indicando potencial aplicação desta nova classe de ligantes. Lantanídeos, Sulfóxidos, Sparkle, Química Orgânica

Interest in the synthesis of novel luminescent lanthanide complexes stems from the wide area of application in various fields of science. Thus, the theoretical design becomes an important tool in the search for efficient luminescent complex. Within this context, emerged the Sparkle model that were developed for predicting the ground state geometries of lanthanide complexes. In this work we present a new parameterization of the ion Eu (III) for the AM1 and RM1 semiempirical methods, with the explicit inclusion of orbitals s, p and d in the basis set. With this reasoning, we have limitations in the calculation of lanthanide complexes in the solvent with MOPAC and initiate an improvement in the description of links that show the highest degree of covalency. The parameterization process of this model had a robust statistical analysis to select the set of parameterization, since our whole universe has 144 structures of lanthanide complexes. Thus, we used two methods to identify the structures that should be part of the parameter set: (i) the method of hierarchical grouping known as AGNES and (ii) the DIANA method. The models that we developed (AM1/Eu and RM1/Eu) showed an improvement compared to the versions of the Sparkle model, considering the low average absolute errors for the distances Eu L (L = O, N, C, S, P, F, Cl, Br and Eu), maintaining the commitment to the low computational cost involved in performing the calculations of the geometries of the ground state. We also investigated the accuracy of quantum-chemical methods in the reproduction of the coordination polyhedron of lanthanide ion complexes. We compared semiempirical methods (the PCC approach and Sparkle model) and also those with the ab initio methodology RHF/ECP/STO-3G. After this study, we conclude that the only semiempirical Sparkle model (hundreds of times faster) present similar accuracy to what can be obtained by present-day ab initio/ECP full geometry optimization calculations on such lanthanide complexes. In addiction it further indicates that the PCC approach is inappropriate to predict the coordination polyhedron geometries of lanthanide complexes. / O interesse na síntese de novos complexos de lantanídeos luminescentes advém da vasta área de aplicação em diversos campos da ciência. Deste modo, o design teórico torna-se uma importante ferramenta na busca de eficientes complexos luminescentes. Dentro desse contexto, surgiram as versões do modelo Sparkle que foram desenvolvidas para a predição da geometria do estado fundamental de complexos de lantanídeos. Nesta dissertação, buscaremos parametrizar o íon Eu(III) para os métodos semiempíricos AM1 e RM1, com a inclusão explícita de orbitais do tipo s, p e d no conjunto de base. Com essa fundamentação, acabamos com limitações no cálculo de complexos lantanídicos em meio solvente com o MOPAC e iniciamos uma melhoria na descrição de ligações com grau de covalência mais elevados. O processo de parametrização deste modelo contou com uma análise estatística robusta para a seleção do conjunto de parametrização, uma vez que o nosso conjunto universo apresenta 144 estruturas de complexos de európio. Desta forma, utilizamos dois métodos para identificar as estruturas que deveriam fazer parte do conjunto de parametrização: (i) o método hierárquico de agrupamento conhecido como AGNES e (ii) o método de desagrupamento DIANA. Os modelos que desenvolvemos (AM1/Eu e RM1/Eu) mostraram uma evolução em relação às versões do modelo Sparkle, tendo em vista os baixos erros médios absolutos para as distâncias Eu L, (L = O, N, C, S, P, F, Cl, Br e Eu), mantendo o compromisso com o baixo custo computacional envolvido na execução dos cálculos das geometrias do estado fundamental. Também investigamos a exatidão dos métodos químico-quânticos na reprodução do poliedro de coordenação de complexos de íons lantanídeos. Nós comparamos métodos semiempiricos (a abordagem PCC e o modelo Sparkle) e ainda esses com a metodologia ab initio RHF/ECP/STO-3G. Após este estudo, concluímos que a abordagem PCC é ineficiente para reproduzir o poliedro de coordenação cristalográfico desses complexos. Os resultados obtidos confirmaram também que os modelos Sparkle apresentam exatidão semelhante, à que pode ser obtida pela otimização completa da geometria, utilizando as atuais metodologias ab initio/ECP.

No description available.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this work we describe a theoretical study of lanthanide complexes with macrocyclic ligands. Spectroscopic properties of the cryptate [EuÌ(bipy)2py(CO2Et)2]3+.2H2O were investigated with semiempirical methodologies such as Sparkle, INDO/S-CIS, Judd- Ofelt model as well as Malta s models implemented in LUMPAC (Luminescence Package). This computational package has turned viable the purely theoretical design of highly luminescent lanthanide complexes. We initially looked for a calculation method that better reproduced the absorption spectrum of the cryptate, finding out that AM1-p was the best candidate. This method used Sparkle/AM1 together with INDO/S-CIS. In the sequence we tested LUMPAC s efficacy using a series of trisbipyridines and observed that the theoretical results were in good agreement to the experimental ones. Finally, we studied the cryptate EuÌ(bipy)2py(CO2Et)2]3+.2H2O and its derivatives. The theoretical intensity parameters (= 2, 4, 6) of the cryptates revealed that Eu3+ ion lies in a weakly polarizable environment. The transfer rates clearly indicated that the energy transfer occurs predominantly from the ligand s triplet state to 5D1 and 5D0 levels belonging to Eu3+ ion. The low quantum yield values observed for all cryptates were probably due to a poor resonance between the ligand s triplet state and the emitting level from Eu3+. The most promising substituted cryptate was found to be [EuÌ3]3+, however the calculation of a cryptate conjugated with microcystin-LR did not show better results. In summary the results as a whole evidenced that the methodology employed is promising in predicting spectroscopic properties of lanthanide complexes. / Neste trabalho, realizamos um estudo teórico envolvendo complexos de lantanídeos com ligantes macrocíclicos. Investigamos as propriedades espectroscópicas do criptato [EuÌ(bipy)2py(CO2Et)2]3+.2H2O utilizando metodologias semiempíricas, como os modelos Sparkle, INDO/S-CIS, o modelo de Judd-Ofelt e os modelos de Malta e colaboradores implementados no pacote computacional denominado LUMPAC Luminescence Package. Tal pacote tornou viável o procedimento de design puramente teórico de complexos de lantanídeos com elevada luminescência. Inicialmente buscamos a metodologia de cálculo mais adequada para o estudo, tomando como critério a reprodução do espectro de absorção do criptato, de tal forma que o método que apresentou o melhor perfil foi o AM1-p. Este método utilizou o Sparkle/AM1 em conjunto com a metodologia INDO/S-CIS. Em seguida, testamos a eficácia do pacote computacional LUMPAC usando uma série de trisbipiridinas, verificando que os resultados teóricos ficaram em acordo com os dados experimentais. Por fim, estudamos o criptato [EuÌ(bipy)2py(CO2Et)2]3+.2H2O e seus derivados. Os parâmetros teóricos de intensidades (= 2, 4, 6) do criptatos revelaram que o íon Eu3+ está em um ambiente pouco polarizável. As taxas de transferência indicaram claramente que a transferência de energia ocorre predominantemente do estado tripleto do ligante para os níveis 5D1 e 5D0 do íon Eu3+. Os baixos valores observados para os rendimentos quânticos de todos os criptatos foram devidos a uma pobre ressonância entre o estado tripleto do ligante e o nível emissor do íon Eu3+. O criptato substituído mais promissor foi o [EuÌ3]3+, contudo os cálculos do criptato conjugado com a microcistina-LR, não se mostraram melhores. Tal fato pode ser explicado considerando-se que o acréscimo no rendimento quântico do criptato é da ordem do erro do modelo. Em suma, todo o conjunto de resultados evidenciou que a metodologia empregada é promissora com relação à previsão de propriedades espectroscópicas de complexos de lantanídeos.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this work we describe a theoretical study of lanthanide complexes with macrocyclic ligands. Spectroscopic properties of the cryptate [EuÌ(bipy)2py(CO2Et)2]3+.2H2O were investigated with semiempirical methodologies such as Sparkle, INDO/S-CIS, Judd- Ofelt model as well as Malta s models implemented in LUMPAC (Luminescence Package). This computational package has turned viable the purely theoretical design of highly luminescent lanthanide complexes. We initially looked for a calculation method that better reproduced the absorption spectrum of the cryptate, finding out that AM1-p was the best candidate. This method used Sparkle/AM1 together with INDO/S-CIS. In the sequence we tested LUMPAC s efficacy using a series of trisbipyridines and observed that the theoretical results were in good agreement to the experimental ones. Finally, we studied the cryptate EuÌ(bipy)2py(CO2Et)2]3+.2H2O and its derivatives. The theoretical intensity parameters (= 2, 4, 6) of the cryptates revealed that Eu3+ ion lies in a weakly polarizable environment. The transfer rates clearly indicated that the energy transfer occurs predominantly from the ligand s triplet state to 5D1 and 5D0 levels belonging to Eu3+ ion. The low quantum yield values observed for all cryptates were probably due to a poor resonance between the ligand s triplet state and the emitting level from Eu3+. The most promising substituted cryptate was found to be [EuÌ3]3+, however the calculation of a cryptate conjugated with microcystin-LR did not show better results. In summary the results as a whole evidenced that the methodology employed is promising in predicting spectroscopic properties of lanthanide complexes. / Neste trabalho, realizamos um estudo teórico envolvendo complexos de lantanídeos com ligantes macrocíclicos. Investigamos as propriedades espectroscópicas do criptato [EuÌ(bipy)2py(CO2Et)2]3+.2H2O utilizando metodologias semiempíricas, como os modelos Sparkle, INDO/S-CIS, o modelo de Judd-Ofelt e os modelos de Malta e colaboradores implementados no pacote computacional denominado LUMPAC Luminescence Package. Tal pacote tornou viável o procedimento de design puramente teórico de complexos de lantanídeos com elevada luminescência. Inicialmente buscamos a metodologia de cálculo mais adequada para o estudo, tomando como critério a reprodução do espectro de absorção do criptato, de tal forma que o método que apresentou o melhor perfil foi o AM1-p. Este método utilizou o Sparkle/AM1 em conjunto com a metodologia INDO/S-CIS. Em seguida, testamos a eficácia do pacote computacional LUMPAC usando uma série de trisbipiridinas, verificando que os resultados teóricos ficaram em acordo com os dados experimentais. Por fim, estudamos o criptato [EuÌ(bipy)2py(CO2Et)2]3+.2H2O e seus derivados. Os parâmetros teóricos de intensidades (= 2, 4, 6) do criptatos revelaram que o íon Eu3+ está em um ambiente pouco polarizável. As taxas de transferência indicaram claramente que a transferência de energia ocorre predominantemente do estado tripleto do ligante para os níveis 5D1 e 5D0 do íon Eu3+. Os baixos valores observados para os rendimentos quânticos de todos os criptatos foram devidos a uma pobre ressonância entre o estado tripleto do ligante e o nível emissor do íon Eu3+. O criptato substituído mais promissor foi o [EuÌ3]3+, contudo os cálculos do criptato conjugado com a microcistina-LR, não se mostraram melhores. Tal fato pode ser explicado considerando-se que o acréscimo no rendimento quântico do criptato é da ordem do erro do modelo. Em suma, todo o conjunto de resultados evidenciou que a metodologia empregada é promissora com relação à previsão de propriedades espectroscópicas de complexos de lantanídeos.

No description available.

The digital reproduction of materials has developed greatly over the past decades. The improved interactive rendering technology available nowadays enables broad digital visualization applications like gaming, cinema and film production, advertising, and online shopping. These recent advances in digital technologies are also playing an important role in the improvement of some industrial processes such as computer-aided design and manufacturing, virtual prototyping, and scientific visualization and simulation. Currently, many rendering software packages provide impressive images and often even claim photorealism. However, producing realistic appearance images is very challenging taking into account the high sensitivity of the human visual system. The visual appearance of products is still an important aspect to take into account even for the digital simulation of materials, since the appearance of these simulated products on the screen is still a critical parameter in the purchase decision of customers. During the last years different efforts have been carried out by industrial manufacturers in different applications, such as textile, cosmetic, automotive, etc., to provide attractive visual effects and new visual impressions of their products using, for instance, innovative effect pigments, also called goniochromatic pigments. The digital rendering of these pigments is a very active hot topic since this type of coatings changes considerably its visual attributes such as color and texture with the illumination/viewing geometry. Achieving accurate simulation of these materials demands an extra effort due to the physical complexity of their surfaces. Special BRDFs (bidirectional reflectance distribution functions) reflectance models are needed to characterize their visual appearance. This complex appearance is produced due to the presence of special effect pigments containing metallic, interference, or pearlescent pigments, which are responsible for the strong dependence of the color of these coatings on viewing and illumination directions. These pigments also exhibit visually complex texture effects such as sparkle and graininess. Under bright direct illumination conditions, such as sunlight, the flakes create a sparkling effect, while under diffuse illumination such as a cloudy sky, effect coatings create a salt and pepper appearance or a light/dark irregular pattern, which is usually referred to as graininess or coarseness. Two main issues limit the digital reproduction of effect pigments. The first issue is related to the current display technologies. The quality of the displays is an essential component toward accurate color reproduction of materials. Previous studies have evaluated the validity of available display technologies for the visualization and digital reproduction of effect pigments, which are usually not enough for the reproduction of such a wide variety of colors due to their limited color gamut. The second limitation is more related to the current rendering software. The color accuracy of their images is often not sufficient for the reproduction of colors and effects produced by these materials. The available rendering software provides impressive images that serve the needs for applications such as the cinema and games industries, but when it comes to more critical applications such as automotive design, the color accuracy of their rendered images is not accurate enough, especially for such complex materials such as effect pigments. The first issue is addressed in this thesis by, evaluating the performance of the new Quantum dots (QDs) display technology for the reproduction of effect pigments. For further improving the display capability, a new solution is given by developing a multi-primary display model based on the QDs technology (addressed in the first research article of this thesis in chapter 1). The proposed multi-primary display model provides an expanded color gamut, which guarantees a better reproduction of effect pigments. In a first step, the emission spectral radiance curves of the three RGB channels of a commercial QD display were fitted to a four-parameter function. From this modeling, it is possible to gain new theoretical color primaries by selecting new spectral peaks (cyan, yellow, magenta, and/or additional RGB primaries) and imposing colorimetric conditions for the resulting white of this proposed theoretical multi-primary display. Proper characterization to assess the performance of the display was conducted to know if the basic “gain-offset-gamma” (GOG) model can be used for direct and inverse color reproduction (from RGB to CIE-XYZ, and vice versa). The GOG model was found to well characterize this display. The spatial uniformity of the display was also evaluated in luminance and color chromaticity terms. Finally, with the primaries modeling and color characterization based on the GOG model, a 5-primary model (RGBYC) was tested. The evaluation of this theoretical RGBYC display model confirms the gamut enlargement, which can also improve goniochromatic color reproduction. In the second place, and focusing on the second issue, a big portion of the work of this thesis was dedicated to the development of a new 3D rendering tool for improved and accurate visualization of the complete appearance of effect coatings, including metallic effects, sparkle, and iridescence (addressed in the second and third research articles of this thesis in chapters 2 and 3). This task was carried on by firstly building a specific rendering framework for this purpose, using a multi-spectral and physically based rendering approach, and secondly, by validating the performance of this rendering framework through psychophysical tests. Spectral reflectance measurements and sparkle indices from a commercially available multi-angle spectrophotometer (BYK-mac i) were used together with a physically based approach, such as flake-based reflectance models, to efficiently implement the appearance reproduction from a small number of bidirectional measurement geometries. With this rendering framework, a virtual representation of a set of effect coating samples is reproduced on an iPad display, by simulating how these samples would be viewed inside a Byko-spectra effect light booth. Therefore, for this purpose, an accurate virtual representation of the Byko light booth was built using a physically based representation of global illumination. The rendering framework also accounts for the colorimetric specifications of the rendering display (iPad5) by applying the recent device-specific MDCIM model. The appearance fidelity of the rendering was validated through psychophysical methods. For this task, observers were asked to evaluate the most important visual attributes that directly affect the appearance of effect coatings, i.e., color, the angular dependence of color (color flop), and visual texture (sparkle and graininess). Observers were asked to directly compare the rendered samples with the real samples inside the Byko-spectra effect light booth. The visual validation was performed in three different steps. In the first study, the accuracy of rendering the color of solid samples is evaluated. In a second step, the accuracy of rendering the color flop of effect coatings is validated by conducting two separate visual tests, by using flat and curved samples respectively. In the third and last step, the digital reproduction of both color and texture of metallic samples is tested, by including texture effects in the rendering by using a sparkle visualization model. The parameters of the sparkle visualization model were optimized based on sparkle measurement data from the BYK-mac i instrument using a matrix-adjustment model. Results from the visual evaluations prove the high color accuracy of the developed rendering tool. In the first test, the visual acceptability of the rendering was 80%. This percentage is much better than what was found in a previous investigation using the default sRGB color encoding space. Results of the second study show an improved accuracy when curved samples were used (acceptability of 93% vs 80%). The final visual test shows high visual acceptability of the rendering at 90%. In conclusion, this thesis provides a method for accurate digital simulation of effect coatings, by developing a multispectral and physically based rendering approach on a simple iPad tablet computer. The research developed in this thesis comes with many advances in the scientific and industrial levels, with a great contribution to the development of innovative tools for digitization of materials, as needed in today’s society. / This thesis was carried out under the financial assistance of the Spanish Ministry of Economy and Competitiveness through the pre-doctoral fellowship FPIBES-2016-077325, and the research projects DPI2015-65814-R and RTI2018-096000-B-I00.

Made available in DSpace on 2015-05-14T13:21:13Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1246890 bytes, checksum: d8de4e92a3d9c573a9ad39ccb546aa71 (MD5) Previous issue date: 2008-11-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Lanthanide macrocyclic complexes, especially containing Gd(III) ions, are largely used as contrast agents in the medical diagnostic technique named Magnetic Resonance Imaging (MRI). Theoretical investigation of these compounds by molecular modeling methods is an emerging research area today. In this work we have performed a conformational study of the following supramolecular compounds: the macrocyclic ligands 1,4,7,10- tetraazacyclododecane (DOTA) and 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid (H4DOTA) and the macrocyclic complexes [Gd(DOTA).H2O]- and Gd(PhenHDO3A).H2O, where PhenHDO3A is (rel-10- [(5R,6R)-5,6-dihydro-6-hydroxy-1,10-Phenanthroline-5-yl)-1,4,7,10- tetraazacyclododecane-1,4,7-triacetic acid). For this, we have developed and carried out a procedure that involves: (1) the sampling of the conformation space of these compounds through some short molecular dynamics at different temperatures and (2) full geometry optimization in the geometries obtained in the previous stage using semi-empirical AM1 method for the macrocyclic ligands and Sparkle/AM1 model for the macrocyclic lanthanide complexes. Our results revealed that the high flexibility of non-coordinated macrocyclic ligands DOTA and H4DOTA, helped us to test the ability of our methodology to sample different regions of conformation space of these compounds. For the [Gd(DOTA).H2O]- complex, we were capable to find the same conformational isomers which were reported in published works as well as to comprehend relevant details about the mobility of the coordinated water molecule. Furthermore, we also were capable to identify some intermediate local minima related to the dynamics of rotation of the coordinated acetate groups in the studied complexes as well as to the dynamics of ring inversion of the coordinated tetraazadodecane moiety in the Gd(PhenHDO3A).H2O. In conclusion, we possess now an interesting strategy to conduct the search for conformational isomers of these compounds. This knowledge is very important to be applied in the rational design of new molecules to act as contrast agent in MRI. / Complexos macrocíclicos de lantanídeos, em especial com o íon Gd(III), são cada vez mais utilizados como agentes de contrastes na técnica médica de diagnóstico, imagem por ressonância magnética nuclear (MRI). O estudo teórico de novos agentes de contrastes através de modelagem molecular é uma área de pesquisa em grande expansão. No nosso trabalho fizemos um estudo conformacional dos seguintes compostos supramoleculares: os ligantes macrocíclicos 1,4,7,10- tetraazaciclododecano (DOTA) e ácido 1,4,7,10-tetraazaciclododecano- 1,4,7,10-tetraacético (H4DOTA), o complexo macrocíclico [Gd(DOTA)H2O]- e o complexo macrocíclico Gd(PhenHDO3A).H2O, onde PhenHDO3A é (rel-10-[(5R,6R)-5,6-dihidro-6-hidroxi-1,10-fenantrolina-5- il)-1,4,7,10-tetraazaciclododecano-1,4,7-ácido triacético). Para isso, elaboramos e executamos um procedimento que envolve o mapeamento ou amostragem do espaço conformacional desses compostos através de dinâmicas moleculares curtas em diferentes temperaturas para em seguida, essas geometrias serem usadas como pontos de partida para otimização de geometria usando tanto o método semi-empírico AM1 quanto o modelo Sparkle/AM1. Como resultado, podemos citar que a elevada flexibilidade dos ligantes macrocíclicos não coordenados DOTA e H4DOTA, serviu para testar a capacidade da nossa metodologia de visitar regiões distintas do espaço conformacional. Para o complexo [Gd(DOTA)H2O]-, conseguimos encontrar os mesmos isômeros conformacionais que já são reportados em outros estudos, bem como revelar detalhes relativos à mobilidade da molécula de água coordenada. Além disso, conseguimos identificar mínimos locais intermediários que estão relacionados com a dinâmica de rotação dos grupos acetato em ambos os complexos e a dinâmica de inversão do anel tetraazadodecano no complexo Gd(PhenHDO3A).H2O. A relevância desse trabalho está apoiada no fato de que agora temos uma estratégia interessante para realizar a busca de isômeros conformacionais desses compostos, sendo essas informações, muito importantes quando se deseja projetar uma nova molécula para atuar como agente de contraste em MRI.