Lee Ho-Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 71-72). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iii / Table of Contents --- p.iv / List of Tables --- p.vi / List of Figures --- p.vii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- The Gaussian´ؤ3 Method --- p.1 / Chapter 1.2 --- "The G2++, a Modified Gaussian-2 Method" --- p.2 / Chapter 1.3 --- Density Functional Theory (DFT) --- p.2 / Chapter 1.4 --- Calculation of Thermodynamical Data --- p.3 / Chapter 1.5 --- Remark on the Location of Equilibrium and Transition Structures --- p.3 / Chapter 1.6 --- Natural Bond Orbital (NBO) Analysis --- p.3 / Chapter 1.7 --- Scope of the Thesis --- p.4 / Chapter 1.8 --- References --- p.4 / Chapter Chapter 2 --- Structures and Energetics of C3H6S+´Ø Isomers: A Gaussian-3 ab initio Study --- p.6 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Methods of Calculation --- p.8 / Chapter 2.3 --- Results and Discussion --- p.8 / Chapter 2.4 --- Conclusion --- p.21 / Chapter 2.5 --- Publication Note --- p.21 / Chapter 2.6 --- References --- p.22 / Chapter Chapter 3 --- A Gaussian-3 Study of the C3H6S Isomers and the Dissociation Channels of Diradical ´ØCH2CH2SCH2´Ø and Its Radical Cation ´ØCH2CH2SCH2+ --- p.24 / Chapter 3.1 --- Introduction --- p.24 / Chapter 3.2 --- Methods of Calculation --- p.25 / Chapter 3.3 --- Results and Discussion --- p.26 / Chapter 3.3.1 --- Structures and Energetics of C3H6S Isomers --- p.26 / Chapter 3.3.2 --- Dissociation Channels of ´ØCH2CH2SCH2´Ø and ´ØCH2CH2SCH2+ --- p.34 / Chapter 3.4 --- Conclusion --- p.40 / Chapter 3.5 --- Publication Note --- p.41 / Chapter 3.6 --- References --- p.41 / Chapter Chapter 4 --- Computational Study on the Electrocyclic Reactions of [16]Annulene --- p.43 / Chapter 4.1 --- Introduction --- p.43 / Chapter 4.2 --- Methods of Calculation --- p.45 / Chapter 4.3 --- Results and Discussion --- p.45 / Chapter 4.3.1 --- Reaction (1) --- p.49 / Chapter 4.3.2 --- Reaction (2) --- p.50 / Chapter 4.3.3 --- Reaction (3) --- p.52 / Chapter 4.3.4 --- Overall Reaction --- p.53 / Chapter 4.4 --- Conclusion --- p.54 / Chapter 4.5 --- Publication Note --- p.55 / Chapter 4.6 --- References --- p.55 / Chapter Chapter 5 --- Computational Study on the Structures and Stabilities of Some Hypothetical Silicon Nanotubes --- p.57 / Chapter 5.1 --- Introduction --- p.57 / Chapter 5.2 --- Model Design and Methods of Calculation --- p.59 / Chapter 5.3 --- Results and Discussion --- p.59 / Chapter 5.3.1 --- "Armchair (n,n) SiNTs" --- p.60 / Chapter 5.3.2 --- "Zigzag (n,0) SiNTs" --- p.61 / Chapter 5.3.3 --- "Chiral (n,m) SiNTs" --- p.65 / Chapter 5.3.4 --- Stabilities of SiNTs at Elevated Temperature --- p.69 / Chapter 5.4 --- Conclusion --- p.70 / Chapter 5.5 --- References --- p.71 / Chapter Chapter 6 --- Conclusion --- p.73 / Appendix A --- p.74 / Appendix B --- p.76 / Appendix C --- p.77

The interest in metal-organic materials namely, coordination polymers and metal-organic frameworks has risen dramatically over the past few years. To a certain extent this interest is a consequence of the realization chemists have discovered how to play a form of molecular Lego® in which metal cations or metal clusters represent the bricks (or nodes) and organic ligands such as 4,4-bipyridine (bipy) or benzene-dicarboxylate represents the glue (or spacers). The "node-and-spacer" approach to self-assembly can be invoked in such a manner that a plethora of infinite architectures and discrete polyhedra can be generated from geometric principles, some of which are unprecedented in either natural or synthetic materials. The research presented within this dissertation primarily involves the use of coordination chemistry and supramolecular chemistry in the context of synthesizing metal-organic materials and deals with how subtle variations in reactants and procedures can have dramatic effects upon the materials formed. The effect of aromatic guest molecules on the crystal packing of 1D and 2D "metal-4,4`-bipyridine" coordination polymers has been addressed in terms of structural analysis and fluorescence spectroscopy. The phenomena of supramolecular isomerism resulting from the use of metal-carboxylate clusters as building blocks for a variety of metal-organic materials will be discussed. Finally, an analysis of the Host:Guest and suprasupermolecular properties of discrete nanostructures will be provided.

Les diradicaux sont des espèces réputées extrêmement instables. A titre d'exemple, le<br />cyclobutanediyle qui est l'archétype de ce genre d'espèce en série carbonée n'a en effet pu<br />être isolé que dans des matrices à basse température.<br />La première partie de cet exposé sera consacrée aux diradicaux formés des éléments<br />lourds des groupes principaux.<br />Nous montrerons dans une introduction bibliographique comment l'utilisation de ces<br />hétéroéléments a permis l'isolation du premier diradical localisé singulet stable basé sur un<br />squelette formé uniquement des hétéroéléments bore et phosphore.<br />Dans un deuxième chapitre, nous nous intéresserons aux isomères de ce diradical, en<br />particulier ses isomères de valence. Après un bref retour sur le concept, nous étudierons les<br />facteurs qui permettent de stabiliser les différents isomères déjà connus. Nous montrerons<br />ensuite comment il a été possible d'isoler de nouveaux isomères.<br />Dans un troisième chapitre, nous nous arrêterons sur deux isomères de valence<br />particuliers et étudierons l'isomérie d'élongation (bond-stretch isomerism). Dans notre cas,<br />deux isomères qui ne diffèrent que par la longueur d'une liaison sont en équilibre. Grâce à<br />des études de RMN à température variable, nous mettrons en évidence l'influence des<br />facteurs électroniques dans cet équilibre.<br />Ce travail nous a amenés à nous interroger sur la possibilité de préparer un diradical<br />purement organique formé uniquement d'éléments de la seconde ligne : carbone et azote.<br />Cette réflexion nous a conduits à mettre au point une nouvelle méthode de synthèse de sels<br />d'iminium et d'imidazolinium que nous présenterons dans une deuxième partie.

Network structures based upon metal-organic backbones represent a new class of functional materials that can be rationally constructed by employing the concepts of supramolecular chemistry and crystal engineering. The modularity of design strategies, the diversity of prototypal structures, and the dynamic features of networks have afforded great advantages over traditional materials syntheses. The research presented in this thesis is primarily concerned with developing an in-depth understanding of the basic principles that govern the supramolecular behaviors of metal-organic networks and gaining an experimental control over the structure and function of these new classes of hybrid materials.The use of rigid and angular organic ligands along with transition metal clusters gives rise to a wide variety of novel metal-organic architectures ranging from zero-dimensional nanostructures to three-dimensional frameworks. Conformational analysis of these structural models suggests the geometric foundations for the existence of superstructural diversity. Controlled crystallization experiments further reveal the synthetic factors that might determine the formation of supramolecular isomers.Careful selection of more labile organic components, on the other hand, leads to flexible metal-organic networks exhibiting dynamic characteristics that have not been observed in their rigid counterparts. The guest-dependent closing/opening of cavities and the ease of fine-tuning their chemical environments demonstrate the effectiveness of such a strategy in the context of generating tailored functional materials.

Esta dissertação de Mestrado tem por objetivo principal investigar as possibilidades de uso dos programas de simulação computacional no campo de isomeria geométrica no contexto da escola pública. Para contemplar esse objetivo, a referida pesquisa foi constituída a partir de uma pesquisa bibliográfica e de um estudo de caso numa escola pública. O referencial teórico foi construído para investigar os efeitos do uso de programas computacionais no ensino de isomeria geométrica; realizamos entrevistas semiestruturadas com três professores de uma escola, situada na cidade de Caxias do Sul, no estado do Rio Grande do Sul, a fim de contrastar os interlocutores teóricos e empíricos. A partir do conjunto de informações oriundas do contexto escolar, associadas à fundamentação teórica, foi possível apontar um conjunto de resultados: i) a escola apresenta baixo nível de utilização da tecnologia no ensino; ii) o acesso ao laboratório de química e de informática é prejudicado pela burocracia; iii) o professor atua com sobrecarga de trabalho; iv) as capacitações ou formações continuadas para os professores são insuficientes; v) a carga horária para o ensino de Química foi drásticamente reduzida em comparação a anos anteriores; vi) há falta de empenho dos estudantes. Dentro desse contexto, classifica-se essa pesquisa por meio de uma abordagem exploratória, onde usou-se a técnica qualitativa de Análise Textual Discursiva (ATD) para compreender o corpus de pesquisa. Além disso, no que tange ao uso de programas de simulação, os resultados da consulta à bibliografia atestam que os programas computacionais são importantes ferramentas de apoio ao ensino de isomeria geométrica, pois melhoram a visualização entre os três níveis de representação da Química (macroscópico, microscópico e simbólico) meio da criação de moléculas em duas dimensões e a conversão destas para a forma tridimensional. Observamos que os estudantes, nativos digitais, são hábeis no manuseio de aplicativos computacionais. Complementarmente os professores entrevistados declararam não fazer uso de programas computacionais por uma série de razões: horários de aula reduzidos, desconhecimento dos programas e seu uso, poucas oportunidades de formação continuada. Portanto, nosso estudo sugere que se deva romper a visão tradicional do ensino da química (segundo a qual bastaria dotar as escolas de recursos de informática) para mudar as práticas pedagógicas. É necessário transgredir esse modelo e pensar em metodologias que se voltem aos fundamentos das disciplinas, que atendam ao processo de construção do conhecimento, promovendo assim a ascensão de um ensino de Química voltado à formação de estudantes críticos. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-05-30T12:37:25Z No. of bitstreams: 1 Dissertacao Fabiana Pauletti.pdf: 1562679 bytes, checksum: bdea2a7a9acc698d3d29181b92c47ab7 (MD5) / Made available in DSpace on 2014-05-30T12:37:25Z (GMT). No. of bitstreams: 1 Dissertacao Fabiana Pauletti.pdf: 1562679 bytes, checksum: bdea2a7a9acc698d3d29181b92c47ab7 (MD5) / This dissertation main to investigate possibilities in apply computer simulation programs based on geometrical isomerism in the context of public school. A literature review and case study in public school was carried out to attend that target. Literature review had been focused on computer programs effects in teaching geometrical isomerism; we also made individual semi-structured interviews with three teachers at High school in Caxias do Sul city, Rio Grande do Sul state, to contrast the theoretical and empirical interlocutors. Based on these set of answer and on literature review we find a group of results: i) the school applies a low level of teaching technology; ii) there is a lot of bureaucracy to access chemistry and technology information labs; iii) teacher has workload; iv) teachers continuous learning is less than expected; v) time for chemistry class has been reduced over years; vi) there are students with low interest. Looking for this context, we classify this research as exploratory approach, where a qualitative technique called Textual Discoursive Analysis (DTA) was applied to understand the contests of interviews. Moreover, regarding computer programs literature results show these programs such as important tools to teach geometrical isomerism, because they improve an overview between Chemistry three levels (macroscopic, microscopic and symbolic) representation and it creates dual dimension molecules and convert them for tri-dimension molecules. We observe that digital native students are more skilled in computer simulation than others. Teachers interviewed declare do not use computer simulation because: they do not have time at class, knowledge limited about computer programs and how to apply it, few opportunities to continuous learning. Therefore, our study proposes a break on traditional chemistry teaching (where information technology is implemented) to changes in the pedagogical practices. It is necessary to overpass that model and to think in methodologies focused on course fundaments, which meet to knowledge build process, and allow a Chemistry teaching applied to educate critical students.

Abstract The first part of this work consisted of a study of the coordination chemistry of aromatic (P,S) and (P,O) heterodonor phosphanes with Cr(CO) 6 , Mo(CO) 6 and W(CO) 6 . The (P,S) donor ligands having one or two o -thiomethoxyphenyl groups, preferred bidentate coordination mode, while the (P,O) donor ligands, having one, two or three o -methoxyphenyls, formed monodentate phosphorus bound complexes. Steric and electronic parameters affecting the coordination chemistry of the phosphanes are discussed for the monodentate complexes. In the second part, triphenylphosphane and 2- and 4-pyridyldiphenylphosphane substituted tungsten tetracarbonyl derivatives was prepared, and attractive intramolecular interactions between the phosphane ligands were studied for both the neutral and the protonated complexes. Hydrogen bonding, π -stacking and cation-π bonding interactions were established, and observed to influence the cis/trans isomerism of the complexes. Cis/trans isomerism could be tuned by protonation, and deprotonation of the pyridyldiphenylphosphane derivatives. All the complexes were characterised by 1 H, 13 C-{ 1 H} and 31 P-{ 1 H} NMR spectroscopy, X-ray crystallography, IR spectroscopy, and either elemental analysis or mass spectroscopy.

Esta dissertação de Mestrado tem por objetivo principal investigar as possibilidades de uso dos programas de simulação computacional no campo de isomeria geométrica no contexto da escola pública. Para contemplar esse objetivo, a referida pesquisa foi constituída a partir de uma pesquisa bibliográfica e de um estudo de caso numa escola pública. O referencial teórico foi construído para investigar os efeitos do uso de programas computacionais no ensino de isomeria geométrica; realizamos entrevistas semiestruturadas com três professores de uma escola, situada na cidade de Caxias do Sul, no estado do Rio Grande do Sul, a fim de contrastar os interlocutores teóricos e empíricos. A partir do conjunto de informações oriundas do contexto escolar, associadas à fundamentação teórica, foi possível apontar um conjunto de resultados: i) a escola apresenta baixo nível de utilização da tecnologia no ensino; ii) o acesso ao laboratório de química e de informática é prejudicado pela burocracia; iii) o professor atua com sobrecarga de trabalho; iv) as capacitações ou formações continuadas para os professores são insuficientes; v) a carga horária para o ensino de Química foi drásticamente reduzida em comparação a anos anteriores; vi) há falta de empenho dos estudantes. Dentro desse contexto, classifica-se essa pesquisa por meio de uma abordagem exploratória, onde usou-se a técnica qualitativa de Análise Textual Discursiva (ATD) para compreender o corpus de pesquisa. Além disso, no que tange ao uso de programas de simulação, os resultados da consulta à bibliografia atestam que os programas computacionais são importantes ferramentas de apoio ao ensino de isomeria geométrica, pois melhoram a visualização entre os três níveis de representação da Química (macroscópico, microscópico e simbólico) meio da criação de moléculas em duas dimensões e a conversão destas para a forma tridimensional. Observamos que os estudantes, nativos digitais, são hábeis no manuseio de aplicativos computacionais. Complementarmente os professores entrevistados declararam não fazer uso de programas computacionais por uma série de razões: horários de aula reduzidos, desconhecimento dos programas e seu uso, poucas oportunidades de formação continuada. Portanto, nosso estudo sugere que se deva romper a visão tradicional do ensino da química (segundo a qual bastaria dotar as escolas de recursos de informática) para mudar as práticas pedagógicas. É necessário transgredir esse modelo e pensar em metodologias que se voltem aos fundamentos das disciplinas, que atendam ao processo de construção do conhecimento, promovendo assim a ascensão de um ensino de Química voltado à formação de estudantes críticos. / This dissertation main to investigate possibilities in apply computer simulation programs based on geometrical isomerism in the context of public school. A literature review and case study in public school was carried out to attend that target. Literature review had been focused on computer programs effects in teaching geometrical isomerism; we also made individual semi-structured interviews with three teachers at High school in Caxias do Sul city, Rio Grande do Sul state, to contrast the theoretical and empirical interlocutors. Based on these set of answer and on literature review we find a group of results: i) the school applies a low level of teaching technology; ii) there is a lot of bureaucracy to access chemistry and technology information labs; iii) teacher has workload; iv) teachers continuous learning is less than expected; v) time for chemistry class has been reduced over years; vi) there are students with low interest. Looking for this context, we classify this research as exploratory approach, where a qualitative technique called Textual Discoursive Analysis (DTA) was applied to understand the contests of interviews. Moreover, regarding computer programs literature results show these programs such as important tools to teach geometrical isomerism, because they improve an overview between Chemistry three levels (macroscopic, microscopic and symbolic) representation and it creates dual dimension molecules and convert them for tri-dimension molecules. We observe that digital native students are more skilled in computer simulation than others. Teachers interviewed declare do not use computer simulation because: they do not have time at class, knowledge limited about computer programs and how to apply it, few opportunities to continuous learning. Therefore, our study proposes a break on traditional chemistry teaching (where information technology is implemented) to changes in the pedagogical practices. It is necessary to overpass that model and to think in methodologies focused on course fundaments, which meet to knowledge build process, and allow a Chemistry teaching applied to educate critical students.

The purpose of this investigation is to examine reactions of anions of oximes, oxime ethers and imines with acylating agents and other electrophiles. It is also an attempt to utilize the phenomenon of geometrical enantiomeric isomerism, in which absolute configuration is determined by double bond geometry, and the concept of regiospecific anion formation, also determined by double bond geometry, for stereospecific synthesis of tropinone derivatives.

<p> The possibility of isomeric nuclear spin states existing among the ammonium ions at low temperatures has been investigated for some twenty ammonium salts. Measurements have been made of the proton absorption signals at 4.2°K, and the temperature dependences, where previously unavailable, of the spin-lattice relaxation time.</p> <p> Some of the salts exhibit the normal rigid lattice spectra and second moments characteristic of distinguishable protons, but most exhibit some degree of line narrowing at 4.2°K. The data shows that thermally activated reorientations are effectively frozen out at this temperature and cannot be responsible for such narrowing.</p> <p> It is concluded that the narrow spectra, although indicative of indistinguishability among the protons, are not attributable solely to spin isomerism, but are being modified by a further mechanism, probably tunneling of the ammonium ion through the crystal field barrier.</p> / Thesis / Doctor of Philosophy (PhD)

The sulfonation of toluene at -12.5° C. with sulfur trioxide in liquid sulfur dioxide was found to give 10.03 ± 0.20 % ortho, 0.73 ± 0.20 % meta and 89.24 ± 0.20 % para isomers. This isomer distribution was determined by isotope dilution analysis using sulfur-35 enriched sulfur trioxide. After dilution of aliquots of the neutralized sulfonation mixture with pure sodium salts of each of the isomers prepared from the corresponding toluidines, the isomers were converted to the p-toluidine salts, purified by recrystallization, and counted by liquid scintillation counting. The relative rate of sulfonation of toluene compared to benzene was studied under the same conditions. The analysis in this case was accomplished by ultraviolet spectrophotometry. The only assumption made was that the isomer distribution of toluene does not change when benzene is added during the sulfonation. The results show that the relative rate (kt/kb) is 10.9 ± 1,5 at low benzene to toluene ratios but increases considerably at high ratios. The hydrochlorination of cyclohexerte, cis-2-butene and trans-2-butene with stannic chloride catalyst was studied in n-heptane solvent. The kinetics were found to be considerably influenced by trace impurities, especially moisture. The kinetics were found to be first order in olefin and stannic chloride and from zero to three and one-half order in hydrogen chloride depending on the amount of moisture present. When moisture is absent, unexplained abnormal kinetics occurred. Polymerization, cyclization, alkylation, and dehydrochlorination were insignificant under the conditions of the kinetic experiments.