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1
Feixas, Geronès Ferran. „Analysis of chemical bonding and aromaticity from electronic delocalization descriptors“. Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/37471.
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Interactions between electrons determine the structure and properties of matter from molecules to solids. Therefore, the understanding of the electronic structure of molecules will enable us to extract relevant chemical information. In the first part of this thesis, we focus our attention on the analysis of chemical bonding by means of the Electron Localization Function (ELF) and the Domain-Averaged Fermi Hole analysis (DAFH). In the second part, we assess the performance of some indicators of aromaticity by analyzing their advantages and drawbacks. We propose a series of tests based on well-known aromaticity trends that can be applied to evaluate the aromaticity of current and future indicators of aromaticity in both organic and inorganic species. Moreover, we investigate the nature of electron delocalization in both aromatic and antiaromatic systems in the light of Hückel’s (4n + 2) rule. Finally, we analyze the phenomenon of multiple aromaticity in all-metal clusters.Les interaccions entre electrons determinen l’estructura i propietats de la matèria. Per tant, la comprensió de l’estructura electrònica de les molècules ens permetrà extreure informació química rellevant. En la primera part d’aquesta tesi, centrem la nostra atenció en l’anàlisi de l’enllaç químic per mitjà de la funció de localització electrònica (ELF) i l’anàlisi dels anomenats domain averaged Fermi holes (DAFH). En la segona part, s’avalua el comportament d’alguns indicadors d’aromaticitat analitzant els seus avantatges i inconvenients. Al llarg d’aquesta part, es proposen una sèrie de tests basats en tendències d’aromaticitat conegudes que es poden aplicar per avaluar el comportament dels indicadors actuals en espècies tan orgàniques com inorgàniques. A més a més, s’investiga la naturalesa de la deslocalització d’electrons en sistemes aromàtics i antiaromàtics que segueixen la regla 4n+2 que proposà Hückel. Finalment, analitzem el fenomen de l’aromaticitat múltiple en sistemes metàl•lics
2
Yang, Yuheng. „Study on novel photochromic systems based on chromophores with six-membered ring as central ethene bridge“. Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2012. http://tel.archives-ouvertes.fr/tel-00846636.
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A series of photochromic bisthienylethenes (BTE) chromophores with different central ethene bridges were synthesized. Up to date, the rational design of BTE have been mainly carried out on the side aryl groups. In our work, the influence of the aromaticity of the central ethene bridge on the photochromic properties was studied. Moreover, unlike in the literature where most of BTE have a five-membered ring bridge, six-membered ring bridges were used. In Chapter 1, examples of photochromes are given, along with the main definitions. Chapter 2 deals with BTTE, a BTE with a benzobisthiadiazole bridge and with excellent photochromic properties. c-BTTE, the closed isomer, exhibits excellent thermal stability in various solvents and in the solid state. Its fluorescence can be modulated by solvato- and photochromism. It eliminates the usual bias of thermal back reaction, typical of BTE with a six-membered ring ethene bridge. Chapter 3 is devoted to compounds with bridges having different aromaticities (BTE-NA, BTA and BTTA). Their fluorescence can be modulated by solvato- and photochromism. The relation between aromaticity and thermal stability was established: the low aromaticity of the central ethene bridge with benzobisthiadiazole unit leads to a thermal irreversibility for BTTA, and the small energy barrier between the parallel and anti-parallel conformers and the great difference in absorption between BTTA and c-BTTA allow the full conversion from BTTA to c-BTTA. Molecules with a benzothiadiazole bridge, designed for complexation and for switchable nonlinear optical properties were prepared (Chapters 4 and 5). However, the targeted properties were not evidenced up to now.
3
Krist, Tomáš. „Sekvenční frakcionace organické hmoty huminové kyseliny izolované z Leonarditu“. Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-445142.
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The aim of the diploma thesis was to optimize the sequential fractionation method of organic matter to be used for physico-chemical characterization of extracted fractions. Humic acid isolated from oxidized brown coal of Leonardite was used as a source matrix of organic matter. An eluotropic series was assembled and sequential fractionation was performed by extraction on a Soxhlet apparatus. The original humic acid and fractions were characterized by elemental analysis (EA) and thermogravimetric analysis (TGA), followed by Fourier transform infrared spectrometry (FTIR), molecular absorption spectrometry (UV/VIS), fluorescence spectrometry and potentiometric titration. Atomic ratios were determined from the results of the elemental analysis. From the measured UV/Vis and fluorescence excitation and emission spectra, the absorption coefficients, resp. fluorescence coefficients. Used fractionation method proved to be a suitable method for studying HA structure. A total of 62 wt. % of initial materiál was extracted, indiivdual fraction amounted from 0.36–30.92 wt. %. From the results of the structural analysis, it is clear that with increasing polarity of the organic solvent, fractions with long aliphatic chains were first isolated and their aromaticity graddualy increased. Non-polar organic solvents were suitable for the extraction of lipid-like coumpounds, while the most polar organic fractions were rich in polar groups and their structual parameters were close to the original humic acid. The fraction extracted with acetonitrile was the most unique fraction. This fraction was rich on nitrogen and amine groups and was similar to protein-like structures. In the last two fractions, extracted with alcohols, a significant bathochromic shift typical of fluorophore type V was observed. Among other things, they were also characterized by a higher content of plant carbohydrate residues.
4
Benchouaïa, Rajaa. „Vers de nouveaux métallo-récepteurs : synthèse et études de ligands hybrides hexaphyrine-cyclodextrine“. Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S116.
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Les hexaphyrines sont constituées de six unités pyrroliques et présentent différents types d'aromaticité, à l'origine de leurs remarquables propriétés de coordination. Cependant, les complexes sont décrits majoritairement sur des hexaphyrines « nues ». De plus, l'induction de chiralité sur un anneau de Möbius n'en est qu'à ses prémices. Dans ce contexte, nous explorons les propriétés de coordination des hexaphyrines « chapeautées ». Plus particulièrement, notre objectif consiste à élaborer des ligands hybrides, dont les unités hexaphyrine et cyclodextrine sont liées de manières covalentes. Pour ces hybrides, l'hexaphyrine peut être chapeautée par une à deux cyclodextrines, via six pontages. Dans un premier temps, les études de coordination menées sur la version triplement pontée ont permis de mettre en avant la forte rigidité du système, empêchant une éventuelle adaptation pour l'incorporation d'ions métalliques tels que le ZnII, CdII, HgII, PdII. Dès lors, la synthèse, inédite, des édifices doublement pontés a permis d'avoir accès au premier anneau de Möbius ponté par une cavité. De surcroit, des complexes de ZnII et HgII ont été obtenus. Curieusement, ces ligands présentent 3 sources de chiralité tel un totem. Nous avons réussi à obtenir un excès diastéréoisomérique de 94%, pour la communication en interne entre la chiralité planaire et l'anneau de Möbius, sur les complexes obtenus. De plus, ces complexes ont permis d'avoir une communication de la cyclodextrine quantifiée avec un e.d. de 60%. Par la suite, la fonctionnalisation a été encore plus élaborée en modifiant le cœur de l'hexaphyrine, les positions méso, et la cyclodextrine. Ces hybrides ont ainsi une sphère de coordination plus favorable à la coordination d'ions métalliques. Les premiers essais sont très encourageants. Finalement, ces ligands hybrides pourraient être des récepteurs allostériques ou des catalyseurs, ce qui est en cours de développement au laboratoireHexaphyrins are constituted by six pyrrole units and present different types of aromaticity at the origin of their remarkable coordination properties. However, complexes are mainly described on “naked” hexaphyrins. Besides, the induction of chirality on a Möbius ring is still in its infancy. In this context, we explore the coordination properties of ''capped'' hexaphyrins. More particularly, our objective consist to develop hybrid ligands, where hexaphyrin and cyclodextrin units are covalently linked. For these hybrids, the hexaphyrin can be capped by one or two cyclodextrins, until six linkages. First, coordination studies realized on the triply linked ligands, enabled to show the strong rigidity of the system, avoiding any adaptation for the incorporation of metal ions such as ZnII, CdII, HgII, PdII. Thus, the unprecedented synthesis, of the doubly linked ligands, enabled to have access to the first Möbius ring capped by a cavity. Moreover, complexes of ZnII and HgII were obtained. Interestingly, these ligands present three sources of chirality as a totem. We succeeded to obtain a diastereomeric exces of 94%, for the communication between the planar chirality and the Möbius ring, on the complexes. Besides, these complexes enabled to have a communication from the cyclodextrin quantified by a d.e. of 60%. Then, the functionalisation became more sophisticated by modifiying the hexaphyrin core, the meso positions, and the cyclodextrin. These hybrids have hence a coordination sphere which is more favorable to metal ions coordination. These first tests are really encouraging. Ultimately, these hybrid ligands would lead to allosteric receptors and catalysts, which is the concern of our researches
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Deyris, Pierre-Alexandre. „Convergent assembly of natural benzophenanthridines and the chemistry of stable all-metal aromatic complexes“. Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS109/document.
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Depuis plusieurs décennies, la chimie du palladium a connu un véritable essor. Afin de de continuer dans cette optique, plusieurs axes de recherche ont été investigués dans le cadre de cette thèse. Grâce aux récents développements de la catalyse duale palladium/norbornène, la réaction de couplage entre des triflates aryliques et des partenaires bromobenzylamines nous a permis d’accéder à des motifs benzophénanthridines naturels. En parallèle, une nouvelle famille de complexes triangulaires de palladium a été isolée dans notre groupe. Cette espèce arborant 44 électrons de valence et une charge positive délocalisée sur son cœur tri-métallique, est la première molécule stable qui présente un caractère métallo-aromatique de type δ. Après l’optimisation d’une nouvelle voie de synthèse, nous avons pu accéder à des analogues de platine mais aussi à des composés hétéro-métalliques possédant des unités asymétriques similaires. Le caractère base de Lewis de ces complexes ont permis l’isolation de composés tétraédriques de type [M”(M₃)(Ln)]²⁺ malgré la répulsion des charges positives. Ces espèces triangulaires aromatiques ont aussi prouvé leur habileté en tant que catalyseur pour la réaction de semi-hydrogénation d’alcynes. En effet, ce complexe transforme chimiosélectivement les alcynes en alcènes de configuration Z sans présence de produit doublement réduitRecent developments on dual palladium/norbornene catalytic reactions led to one-pot synthesis of complexes polyheterocyclic molecules. By extension of this reaction, the coupling of aryl triflates and bromobenzylamines permitted us to synthesize natural benzophenanthridine. In parallel, a new family of triangular palladium complexes has been isolated in our research group. These 44 valence electrons complexes possessing a positive charge delocalized on the trimetallic core were the first stable compounds which presented δ-type aromaticity. After optimization of a new synthetic route, we could be able to isolate platinum analogues and also heterometallic clusters which interestingly had the same asymmetric unit than their homonuclear peers. Despite the unavoidable charge repulsion, the Lewis basic character revealed to be strong enough to bind other cationic species. Indeed, we reached to synthesize tetrahedral [M”(M₃)(Ln)]²⁺ complexes. In another side, we wondered if the stability and special properties of [Pd₃]⁺ clusters could confer to it some catalytic activities. Our studies were focused on semi-reduction reactions of alkynes. After optimization process, the catalyst [Pd₃(SMe)₃{P(C₇H)₃)₃}]⁺ showed results beyond our greatest expectations. Indeed, this cluster selectively produced thermodynamically less stable Z-alkene without traces of over-reduced compound. Total chemioselectivity towards alkynes was proved by the reaction on several molecules bearing functional groups which are sensitive to hydrogenation conditions
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Cocq, Kévin. „Synthèse et propriétés de nouvelles molécules carbo-mères : carbo-quinoïdes et carbo-benzénoïdes“. Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30212/document.
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A la suite de nombreuses illustrations et validations au niveau fondamental, la chimie de molécules carbo-mères s'est récemment orientée vers des cibles fonctionnelles en termes de perspectives d'applications (" carbo-matériaux " moléculaires). C'est ainsi que de telles molécules expansées en carbone ont récemment montré des propriétés remarquables dans les domaines de la conductivité sur molécule unique (SMC) ou de l'absorption à deux photons (TPA). La considération de cibles de types fondamentalement nouveaux " reste cependant nécessaire en préliminaire à l'étude de propriétés nouvelles aussi. Le travail décrit dans ce manuscrit présente essentiellement les résultats concernant la synthèse de carbo-quinoïdes et de carbo-benzénoïdes, deux types de structures carbo-mères qui n'avaient jamais été envisagées expérimentalement auparavant. Le premier chapitre est un résumé bibliographique décrivant notamment la synthèse et les propriétés de molécules carbo-mères aromatiques, et plus généralement hautement pi-conjuguées (carbo-benzènes, carbo-cyclohexadiènes, carbo-oligoacétylènes...) Le second chapitre porte sur l'étude complète des trois régioisomères, " ortho ", " para ", et " meta " du tétraphényl-carbo-benzène, dont les deux premiers représentants avaient été partiellement décrits. Le troisième chapitre décrit la synthèse et l'étude du premier exemple de carbo-quinoïde, ainsi que sa transformation rédox réversible en carbo-benzènes, illustrant ainsi la " pro-aromaticité redox " des carbo-quinoïdes vis-à-vis de leurs analogues oxydés carbo-benzènes. Le quatrième et dernier chapitre est consacré à la synthèse et l'étude d'un carbo-benzénoïde, le carbo-naphtalène, pouvant être considéré comme le plus petit fragment polycyclique condensé d'alpha-graphyne, un matériau largement étudié au niveau théorique mais encore inconnu expérimentalement à ce jour. Les propriétés physico-chimiques et spectroscopiques de carbo-naphtalène sont comparées à celle du carbo-benzène monocyclique correspondant, dont la synthèse est aussi détailléeFollowing numerous illustrations and validations at the fundamental level, the chemistry of carbo-meric molecules was recently directed towards functional targets in terms of application prospects (molecular "carbo-materials'). Such carbon-expanded molecules have indeed recently been shown to exhibit remarkable properties in the areas of single molecule conductivity (SMC) or two-photon absorption efficiency (TPA). The consideration of target of fundamentally "new types" remains necessary in view of the study of new properties as well. The work described in this manuscript focus mainly on results concerning the synthesis of carbo-quinoids and carbo-benzenoids, two types of carbo-meric structures that had not been considered hitherto. The first chapter is a bibliographic summary describing the synthesis and properties of carbo-meric molecules, either aromatic or, more generally, highly pi-conjugated (carbo-benzenes, carbo-cyclohexadienes, carbo-oligoacetylenes...) The second chapter focuses on the complete study of the three regioisomers, "ortho", "para" and "meta" of tetraphenyl-carbo-benzene, the first two representatives having been partly described previously. The third chapter describes the synthesis and study of the first example of carbo-quinoid and its reversible redox transformation to carbo-benzenes, illustrating the "redox pro-aromaticity" of carbo-quinoid with respect to their oxidized carbo-benzenic analogues. The fourth and final chapter is devoted to the synthesis and study of a carbo-benzenoid, carbo-naphthalene, which can be regarded as the smallest condensed polycyclic fragment of alpha-graphyne, a material widely studied at the theoretical level but remaining unknown experimentally to date. The physicochemical and spectroscopic properties of carbo-naphthalene are compared to that of the corresponding monocyclic carbo-benzene, the synthesis of which is also detailed
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Szücs, Rózsa. „Phosphorus modified PAHs : tunable π-systems for optoelectronic applications“. Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S022/document.
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Les Hydrocarbures Polycycliques Aromatiques (abréviés PAHs en anglais) sont des synthons importants du point de vue expérimental et théorique en raison de leurs potentielles applications dans des dispositifs optoélectroniques tels que les diodes électroluminescentes organiques, les cellules solaires ou les transistors à effet de champs. Les propriétés des PAHs peuvent être modifiées par l'insertion d'hétéroatomes dans le squelette carboné sp2. Cependant, les exemples de PAHs modifiés par un atome de P sont très rares. Nous avons démontré expérimentalement et théoriquement que l'insertion d'un atome de P en périphérie du PAH a un impact important sur la structure électronique de l'ensemble du système π-étendu, comme le montre l'étude des orbitales frontières HO (Haute Occupée) et BV (Basse Vacante). Ces deux orbitales moléculaires gardent les caractéristiques spatiales du phosphole parent. Cependant l'écart HO-BV est fortement diminué en raison de l'interaction du phosphole et du système π-conjugué bidimensionnel. En effet, la densité électronique est délocalisée sur l'ensemble de la structure carbonée. L'effet de la modification chimique de l'atome de P (dont la complexation par des métaux de transition) sur les propriétés électroniques a été étudié et il a été démontré qu'elle permet de modifier finement les propriétés optiques. L'aromaticité est également un paramètre fondamental des systèmes π-conjugués (poly)cycliques. L'aromaticité locale de chaque cycle des PAHs a été étudiée grâce au calcul du paramètre NICS(1). La modification de l'aromaticité locale de l'hétérocycle à 5 chainons (par variation de l'hétéroatome) a un fort impact sur l'aromaticité locale des cycles adjacents. Il a également été montré que la cyclo-addition sur les PAHs phosphorés a lieu sur l'hétérocycle de plus faible aromaticité et permet de préparer des PAHs inéditsPolycyclic aromatic hydrocarbons (PAHs) are important targets of experimental and theoretical studies, because of their potential use in optical and electronic devices, such as light-emitting diodes, field-effect transistors or photovoltaics. The properties of PAH systems can be modified by embedding heteroatoms into the sp2 backbone, however for P-modified PAHs, only a few examples exist. During my PhD research, I studied the properties of P-containing extended π-systems. It has been revealed by density functional calculations that the incorporation of phosphorus at the edge position of a PAH has a significant effect on the electronic structure of the entire π-system, as can be seen through the HOMO and LUMO. On the one hand, both orbitals keep the spatial characteristics of the parent heterocycle, on the other hand, the reduced HOMO-LUMO gap compared to the parent heterocycle is a consequence of the interaction between the phosphole unit and the extended aromatic system, as the molecular orbitals are delocalized through the sp2 carbon skeleton. We investigated the effect of chemical modification (including complexation) at the phosphorus atom, and found that due to the variation of the hyperconjugative interaction it can be used to fine-tune the optical properties. Aromaticity is one of the key characteristics of π-systems. During its investigation we have established that the local aromaticities in the investigated ring system could be best described by the NICS(1) values. The modification of the local aromaticity of the five-membered ring (by the variation of the heteroatom) has a significant impact on the local aromaticities of some of the other rings as well. It has been shown that the Diels-Alder cycloaddition of the P-embedded PAHs proceeds at those rings which exhibit the lowest aromaticity
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El, Bakouri El Farri Ouissam. „Electronic structure, chemical bonding, and electronic delocalization of organic and inorganic systems with three-dimensional or excited state aromaticity“. Doctoral thesis, Universitat de Girona, 2017. http://hdl.handle.net/10803/565444.
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Aromaticity is a key concept in chemistry, used by chemists to explain the structure, stability, and reactivity of many compounds. Aromatic compounds are present in industrial processes as well as in living systems. Initially, the realm of aromatic molecules was limited to cyclic benzenoid systems. Over the years, this concept has been expanded to heterosystems, metal clusters, fullerenes, and more exotic molecules. In this thesis, the analysis of electronic structure, chemical bonding, and electronic delocalization of organic and inorganic systems that possess three-dimensional or excited state aromaticity is studied in detail using state-of-the-art computational tools. We mainly focus our attention on the study of the aromaticity of different polycyclic conjugated hydrocarbons, fullerenes and small inorganic clusters. Yet, we also analyze the chemical bonding of different inorganic clustersL'aromaticitat és un concepte clau en química, utilitzat pels químics per explicar l'estructura, l'estabilitat i la reactivitat de molts compostos. Els compostos aromàtics estan presents tant en els processos industrials com en sistemes vius. Al principi, l’àmbit de les molècules aromàtiques estava limitat a sistemes benzenoids cíclics. Amb el pas del temps, aquest concepte s'ha ampliat a sistemes heterocíclics, clústers metàl·lics, ful·lerens i altres molècules més exòtiques. En aquesta tesi, l'anàlisi de l'estructura electrònica, l'enllaç químic i la deslocalització electrònica de sistemes orgànics i inorgànics que posseeixen aromaticitat tridimensional o en estat excitat són estudiats amb detall utilitzant eines computacionals d'última generació. Ens centrem principalment en l’estudi de l'aromaticitat de diferents hidrocarburs policíclics conjugats, ful·lerens i petits clústers inorgànics. Tanmateix, també analitzem l'enllaç químic dels diferents clústers inorgànics
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Inoue, Mitsunori. „Studies on Möbius Aromaticity of Hexaphyrins“. 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142391.
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Matito, i. Gras Eduard. „Development, implementation and application of electronic structural descriptors to the analysis of the chemical bonding, aromaticity and chemical reactivity“. Doctoral thesis, Universitat de Girona, 2006. http://hdl.handle.net/10803/7940.
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En la literatura sobre mecànica quàntica és freqüent trobar descriptors basats en la densitat de parells o la densitat electrònica, amb un èxit divers segons les aplicacions que atenyin. Per tal de que tingui sentit químic un descriptor ha de donar la definició d'un àtom en una molècula, o ésser capaç d'identificar regions de l'espai molecular associades amb algun concepte químic (com pot ser un parell solitari o zona d'enllaç, entre d'altres). En aquesta línia, s'han proposat diversos esquemes de partició: la teoria d'àtoms en molècules (AIM), la funció de localització electrònica (ELF), les cel·les de Voroni, els àtoms de Hirshfeld, els àtoms difusos, etc.L'objectiu d'aquesta tesi és explorar descriptors de la densitat basats en particions de l'espai molecular del tipus AIM, ELF o àtoms difusos, analitzar els descriptors existents amb diferents nivells de teoria, proposar nous descriptors d'aromaticitat, així com estudiar l'habilitat de totes aquestes eines per discernir entre diferents mecanismes de reacció.
In the literature, several electronic descriptors based in the pair density or the density have been proposed with more or less success in their pratical applications. In order to be chemically meaningful the descriptor must give a definition of an "atom" in a molecule, or instead be able to identify some chemical interesting regions (such as lone pair, bonding region, among others). In this line, several molecular partition schemes have been put forward: atoms in molecules (AIM), electron localization function (ELF), Voronoi cells, Hirshfeld atoms, fuzzy atoms, etc.
The goal of this thesis is to explore the density descriptors based on the molecular partitions of AIM, ELF and fuzzy atom, analyze the existing decriptors at several levels of theory, propose new aromaticity descriptors, and study its ability to discern between different mechanisms of reaction.
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Poater, i. Teixidor Jordi. „Índexos de localització i deslocalització derivats de la densitat bielectrònica: anàlisi i aplicacions en estructura molecular, reactivitat química i aromaticitat“. Doctoral thesis, Universitat de Girona, 2003. http://hdl.handle.net/10803/8029.
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La present tesi doctoral s'emmarca dins el camp de la química teòrica icomputacional. El primer objectiu, que va ser el de partida, consistia a veure si els índexos
bielectrònics derivats de la teoria AIM podien ser útils per estudiar la reorganització
electrònica al llarg d'una reacció. De forma paral·lela es va plantejar un objectiu
metodològic, el càlcul dels índexos mencionats a altres nivells de teoria, com podia ser
DFT o CI. CI. Aquests dos objectius varen portar a molts d'altres, tot i que els principals són:
Objectiu 1. Estudi de la reorganització de parells d'electrons al llarg d'una
reacció.
Objectiu 2. Efecte de la solvatació sobre l'estructura de parells d'electrons d'una
molècula.
Objectiu 3. Càlcul dels índexos de localització i deslocalització als nivells de teoria
del funcional de la densitat i post-Hartree-Fock.
Objectiu 4. Caracterització de l'enllaç per pont d'hidrogen per mitjà de
l'estructura dels parells d'electrons.
Objectiu 5. L'índex de deslocalització: nou criteri electrònic d'aromaticitat.
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Jardali, Fatme. „New exotic nanostructured materials : Theoretical predictions and experimental verifications“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX022.
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Cette thèse est consacrée à l'étude approfondie de formes exotiques de matériaux nano-structurés qui pourraient conduire à une avancée significative dans les nano-composants. Deux thèmes distincts ont été ainsi abordés. Le premier concerne les nano-clusters aromatiques de silicium synthétisés par plasma (SiNCs), tandis que le second est dédié aux structures silicium et germanium bi-dimensionnelles. Grâce à des simulations de type dynamique moléculaire et des calculs ab initio, ainsi que sur des recherches expérimentales, nous nous proposons d’explorer les propriétés intrigantes, mais à fort potentiel, de ces matériaux exotiques.Dans la première partie, nous commençons par des études théoriques et montrons qu'il est possible d'obtenir un comportement aromatique pour des SiNCs hydrogénés ayant une taille de ~1nm. Nous démontrons que les plasmas silane/hydrogène à basse température, proches de la formation de particules de poussière, présentent l'environnement idéal pour exploiter la tendance naturelle du silicium à la sur-coordination et donc pour la synthèse de structures à liaisons déficitaires en électrons. Ces nano-clusters qui se forment spontanément par auto-assemblage dans le plasma, ne possèdent pas de structure tétraédrique, sont plus stables que tous les autres SiNCs connus de cette taille et ont de fortes propriétés aromatiques dues à leur forte délocalisation électronique. Nous montrons également que les SiNCs non tétraédriques, présentent des modes de liaison à caractère métallique qui ressemblent fortement à celui d'un gaz d'électrons homogène dans des nano-clusters de métaux. Les SiNCs tétraédriques standards de cette taille ne peuvent absorber que dans l'ultraviolet, alors que nos calculs ont montré que des SiNCs purs, mais sur-coordonnés, absorbent dans la région spectrale ultraviolette, mais aussi dans le visible et l’infrarouge. Nous présentons ensuite une première preuve expérimentale pour nos prédictions théoriques. Nous avons mesuré in situ, dans un réacteur plasma l'absorption de la lumière visible des SiNCs. De plus, nos mesures réalisées en présence d'un champ électrique ont prouvées clairement que les SiNCs aromatiques possèdent un moment dipolaire permanent, que nous avons estimé entre 2 et 2,5 Debye, en excellent accord avec les calculs ab initio. Enfin, nos images de microscopie électronique à transmission des SiNCs, déposés dans des conditions de plasma optimisées, ont révélé la présence d'une autre forme exotique de silicium à structure hexagonale. Une telle structure se forme habituellement à des pressions extrêmement élevées appliquées sur des structures cubiques (diamant) de silicium. Nous souhaitons affirmer que c’est grâce à la «chimie au marteau» que ces conditions ont été atteintes.Dans la seconde partie, nous avons entrepris des études théoriques et expérimentales approfondies sur la croissance d'une nouvelle forme allotropique de silicium et de germanium: le silicène et le germanène, à savoir, une mono-couche d'atomes intégrée dans un réseau hexagonal qui ressemble fortement au graphène. Afin d'exclure tout mélange entre les atomes de silicium ou de germanium avec le substrat et de conserver leurs caractéristiques prometteuses comme de nouveaux matériaux de Dirac, nous avons effectué nos dépôts, sur un substrat de graphite chimiquement inerte. Une de nos découvertes cruciales est que les mono-couches de silicène ou de germanène interagissent avec le substrat de graphite uniquement via des forces de van der Waals. Cette interaction est suffisamment forte pour stabiliser les mono-couches, déposées même au-dessus de la température ambiante, mais suffisamment faible pour empêcher toute hybridation ou alliage entre le silicium ou le germanium et les atomes de carbone du substrat. Par conséquent, les propriétés électroniques exceptionnelles du silicène et du germanène, tels que les cônes de Dirac et les électrons sans masse, sont préservées même après leur dépôt sur les surfaces de graphiteThis thesis is devoted to the study of advanced, exotic forms of nanostructured materials that could lead to the next big advance for nanodevices. Two distinct topics have been considered. The first one is related to plasma-born aromatic silicon nanoclusters (SiNCs), while the second is dedicated to two-dimensional silicon and germanium materials. Based on molecular dynamics simulations and ab initio calculations, as well as, on experimental investigations, we explore a variety of intriguing properties of those exotic materials that are expected to be far superior to those of their conventional counterparts.In the first part of the thesis, we begin with theoretical studies and show that it is possible to obtain aromatic behavior in simple hydrogenated SiNCs with size of ~1nm. We demonstrate that low-temperature silane/hydrogen plasmas close to dust formation present the ideal environment to exploit the natural tendency of silicon to over-coordination for the construction of structures with electron-deficient bonds. Those nanoclusters form spontaneously by self-assembly in plasmas, do not possess tetrahedral structures, are more stable than any other known SiNCs of this size, and have strong aromatic-like properties due to their high electron delocalization. We demonstrate that non-tetrahedral SiNCs exhibit metallic-like bonding schemes that strongly resemble the one of a homogeneous electron gas in small metal clusters. Standard tetrahedral SiNCs of this size can absorb light only in the ultraviolet, while our calculations have shown that pure, but over-coordinated SiNCs absorb light in the ultraviolet, visible, and infrared spectral region. In this thesis, we present first experimental evidence that supports our theoretical predictions. Using incoherent broadband cavity enhanced absorption spectroscopy, we have measured the absorption of SiNCs, in situ, in a plasma reactor and found that they do absorb light in the visible region. In addition, our absorption measurements in the presence of an applied electric field have provided clear evidence that aromatic SiNCs possess a permanent dipole moment, and we have measured it to be between 2 and 2.5 Debye, in excellent agreement to prior ab initio calculations. Finally, our transmission electron microscopy images of such SiNCs, after their deposition under optimized plasma conditions, have revealed the presence of another exotic form of silicon with a primitive hexagonal structure. Such a structure usually forms after exposing diamond-cubic silicon to extremely high pressures. We tentatively claim that those conditions were, actually, achieved in our experiments due to the “chemistry with a hammer”.In the second part of the thesis, we have undertaken in-depth theoretical and experimental studies on the growth of a new allotropic form of silicon and germanium: a single layer of silicon or germanium atoms, only one atom thick and packed in a hexagonal lattice that closely resembles the lattice of graphene, namely silicene and germanene. In order to rule out any intermixing between silicon or germanium atoms and the underneath substrate atoms, as it was the case for metallic substrates, and to maintain their promising features to be new Dirac materials, we have performed our depositions on a chemically inert graphite substrate. One of our crucial findings is that the silicene or germanene monolayers interact with the graphite substrate via van der Waals forces only. The van der Waals interaction is strong enough to stabilize the deposited monolayers even above room temperature, but weak enough to prevent any hybridization or alloying between silicon or germanium and carbon atoms. Consequently, the outstanding electronic properties of free-standing silicene and germanene, such as Dirac cones and massless electrons, are preserved even after their deposition on graphite surfaces
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Doerksen, Robert J. „Geometries, polarizabilities, and aromaticity of ring molecules“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0026/NQ38345.pdf.
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Bean, David Edward. „Aromaticity in molecular systems with multiple ring currents“. Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531195.
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Hill, John Grant. „A theoretical investigation into aromaticity in perocyclic reactions“. Thesis, University of York, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428440.
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Child, Brandon. „AROMATICITY RULES IN THE DEVELOPMENT OF NEGATIVE IONS“. VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3355.
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Organic molecules are known for their stability due to aromaticity. Superhalogens, on the other hand, are highly reactive anions, whose electron affinity is larger than that of chlorine. This thesis, using first principles calculations, explores possible methods for creation of superhalogen aromatic molecules while attempting to also develop a fundamental understanding of the physical properties behind their creation. The first method studied uses anionic cyclopentadienyl and enhances its electron affinity through ligand substitution or ring annulation in combination with core substitutions. The second method studies the possibilities of using benzene, which has a negative electron affinity (EA), as a core to attain similar results. These cases resulted in EAs of 5.59 eV and 5.87 eV respectively, showing that aromaticity rule can be used to create strong anionic organic molecules. These studies will hopefully lead to new advances in the development of organic based technology.
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Arias, Olivares David. „Relation Among Localization, Delocalization and Physicochemical Properties. From Electron Density Databases to Magnetic Properties Effects of the acceptor unit in dyes with acceptor–bridge–donor architecture on the electron photo-injection mechanism and aggregation in DSSCs The role of Cr, Mo and W in the electronic delocalization and the metal–ring interaction in metallocene complexes“. Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS015.
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Tout d'abord, nous évoquerons un aperçu général de l'analyse topologique basée sur la densité d'électronique, le trou d'échange-corrélation et la densité de paires. Une fois la densité électronique rappelée, l'analyse topologique de la densité électronique est expliquée, ainsi que la procédure de calcul des points critiques de la densité électronique, le calcul de la matrice hessienne de la densité électronique et la définition des points critiques à la surface. Tous ces outils topologiques permettent de caractériser la nature des liaisons chimiques parallèlement à l'indice basé sur la délocalisation. Afin de comprendre la nature des énergies et des interactions dans les systèmes, l'analyse d'interaction non covalente est expliquée et combinée à l'analyse de décomposition d?énergie. De plus, les états de transition seront étudiés en appliquant les orbitales naturelles pour la valence chimique (ETS-NOCV). Les concepts clés du magnétisme moléculaire sont abordés. Nous nous concentrons sur l'aimantation et la susceptibilité magnétique, les composants diamagnétiques et paramagnétiques provenant de toute réponse magnétique dans les systèmes. Les propriétés de champs magnétiques induits sont étudiés dans le but de comprendre l'aromaticité à travers de deux descripteurs, les déplacements chimiques indépendants du noyau et les densités de courant induit. En annexe à la théorie, l'interaction isotrope dans les composés dinucléaires est introduite pour expliquer et mesurer certaines erreurs trouvées dans la théorie de la fonctionnelle de densité (TFD). [...]The first property here analysed and related with electronic localization/delocalization is the aromaticity. Aromaticity is an important concept introduced by Kekulé; since then, theoreticians and experimentalist have tried to understand it in different groups of molecules analogues to benzene. The importance of this concept and how the aromaticity is affected by the chemical environment is important to understand and link some physicochemical properties. i.e., reactivity, stability, magnetic response. The physicochemical properties of interest are the electronic structure, the nature of bonds and organometallic interactions(differentiation between metallocenes and metallabencenes). Furthermore, the magnetic response and the study of building blocks as possible candidates to make nano-wires or new low-dimension magnetic materials. Finally, we try to understand the interaction and the errors involved in some properties theoretically computed like, the isotropic coupling between metals through aromatic (or organic) units that have become important benchmark molecules to study magnetic properties in inorganic as well as metal-organic systems [...]
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Bagga, Amit. „Femtosecond Laser Mass Spectroscopy of Cyclic Aromatic Hydrocarbons“. Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37098.
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Cyclic Aromatic molecules are the subject of continued research due to their highly advantageous characteristics which can be exploited in the areas of pharmaceuticals, material science and nano-electronics. While the defining properties and criteria for a molecule to be considered aromatic are very specific and well established, the degree of aromaticity of these molecules and their corresponding ordering remains a source of continued debate. Given that the macroscopic aromatic properties are fundamentally rooted in the underlying electronic structure and molecular dynamics, these properties can be probed in numerous ways. One such method is to exploit the strong laser field as it pertains to non-linear light-matter interaction. More specifically, the study of photoionization, as a direct resultant effect of strong field light-matter interaction, gives us direct insight into electronic and spatial properties as captured via mass spectroscopy. As a strong-field process, photoionization is effective because the variables that influence its results are also the ones that define aromaticity thus a correlation can be postulated. Other strong field advanced techniques to probe aromacity such as High Harmonic Generation (HHG) have already been successful shown by our group to be effective spectroscopic tools. In this way, photoionization provides supporting evidence to enhance the understanding of these novel spectroscopic tools. This thesis demonstrates that photoionization mass spectroscopy can be used as a probe into the aromaticity order of 5-membered cyclic aromatic molecules. Furthermore, the thesis will show that photoionization results correlate with the previously conducted HHG studies in this area thus further supporting these techniques as sensitive spectroscopic tools into aromaticity. The first part of this thesis describes the characterization of aromatic molecules and the corresponding process to obtain photoionization results that can be correlated to aromaticity. In the second part, these results are compared to the theoretical model and HHG demonstrating consistent results. The third and final component of this thesis describes future work, namely two-colour control of photoionization which is intended to provide greater resolution and variation of photoionization spectra thereby providing a more comprehensive and conclusive understanding of the proposed correlation with aromaticity.
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Nendel, Maja. „Computations in organic chemistry : from pericyclic reactions to aromaticity“. Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/30563.
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Lillington, Mark Andrew Edwin. „Current-density maps and the magnetic criterion of aromaticity“. Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487604.
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On the magnetic criterion, an aromatic system is one that sustains a diatropic ring current. Once this definition is accepted, calculation of current density induced in a molecule by an external magnetic field gives a direct way of determining aromaticity from ab initio calculation. The ipsocentric treatment of molecular magnetic response, in which each point is the origin for the local current-density, offers an accurate, economical and conceptually transparent approach to the calculation of ring currents. The distribution of origin uniquely leads to physically non-redundant orbital contributions· that can be used to interpret (or predict) currents in terms of orbital symmetries, energies and nodal character. Diatropic and paratropic currents obey translational and rotational selection rules, respectively, leading to a 'spectroscopic', 'frontier-orbital' theory of ring currents and magnetic aromaticity. This thesis reports investigations of the nature and origin of ring currents in 1t-, (j- and homo-aromatic systems. Rules developed for annulenes extend to heterocycles and account for retention of ring-current aromaticity in perfluorobenzenes in which argon atoms are progressively inserted in the CF bonds. Currents in benzenoid and nonbenzenoid polycyclic aromatic hydrocarbons give varied patterns which can be rationalised in terms of Kekule structures and Pauling bond orders. These concepts are used to explain rim-and-hub currents in circulenes and design molecules with fully paramagnetic 1t currents, verified by ab initio calculation. Studies of heteropolycycles with carbocyclic cores demonstrate the aromaticity of mellitic trianhydride, the non-aromaticity of 'quasi-rings' closed by hydrogen- and lithium-bonds, and rationalise the magnetic properties of the new 'sulflowers' . Calculations on model rings of silicon atoms with tangential p-p bonding show the possibility of (j ring currents governed by modified versions of the ipsocentric 1t selection rules. Saturated cyclopropane also supports (j ring current. The homotropylium cation illustrates the association of a ring current of modified topology with homoaromaticity.
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Mauksch, Michael. „Excursions into chemical topology topomerisations, chiral enantiomerisations and Möbius aromaticity /“. Erlangen, 1999. http://www.opus.ub.uni-erlangen.de/opus/volltexte/2007/679/index.html.
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Duffy, Anne Merete. „Students' ways of understanding aromaticity and electrophilic aromatic substitution reactions“. Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3210647.
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Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2006.Title from first page of PDF file (viewed June 7, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 280-290).
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Olguin, Marco Augusto. „The isotopological homodesmotic reaction a further refinement to the quantification of aromaticity /“. To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Kimball, David Brian. „(Alkynylphenyl)triazenes and phenylacetylene macrocycles for the synthesis of heterocycles and aromaticity probes /“. view abstract or download file of text, 2002. http://wwwlib.umi.com/cr/uoregon/fullcit?p3055694.
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Thesis (Ph. D.)--University of Oregon, 2002.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 249-278). Also available for download via the World Wide Web; free to University of Oregon users.
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Lamm, Ashley, und Ashley Lamm. „Fundamental Chemistry of 1,2-Dihydro-1,2-Azaborines“. Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12514.
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Benzene and its derivatives are ubiquitous in chemical research, with applications ranging from material science to biomedical research. 1,2-Dihydro-1,2-azaborine is a benzene mimic which replaces a CC bond with a BN bond. The basic science and applications of 1,2-azaborines is relatively underdeveloped. This thesis expands the fundamental understanding of 1,2-azaborines. Chapter I describes the air and moisture stability of 1,2-azaborines. Chapter II introduces nucleophilic aromatic substitution reactions that the parent 1,2-dihydro-1,2-azaborine will undergo. Chapter III discusses a trimerization reaction that 1,2-dihydro-1,2-azaborine can perform, which is unique from benzene. Chapter IV examines a novel protection free synthesis of 1,2-azaborines, which provides a more direct route to functionalized 1,2-azaborines. Chapter V discusses the novel deprotection of the N-silicon using an amide, giving one of the first 1,2-azaborine pharmaceutical mimics. Finally, chapter VI summarized miscellaneous contributions I have made to the basic science of 1,2-azaborines.
This dissertation includes previously published and unpublished co-authored material.10000-01-01
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Rombolà, Alessandro Girolamo. „Determinazione di idrocarburi policiclici aromatici in carboni vegetali (biochar)“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2355/.
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Michálková, Renata. „Návrh na zlepšení úrovně spokojenosti zákazníka firmy Aromatica cz“. Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2013. http://www.nusl.cz/ntk/nusl-224184.
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In my diploma thesis I deal with the issue of a customer satisfaction, which is an important factor of the company success. Customer is the most important part of the market, and if the customer is not sufficiently satisfied, he usually goes to another competitor. Than, if the company really wants to be successful in the market, they must try to provide an adequate care and attention to the customer. The aim of this thesis is then to propose a project for increasing the customer satisfaction and thereby also increasing an awareness of the company. I will survey the customer satisfaction in a company dealing with the production and distribution of herbal products. My survey will be based on the method of questioning using interviewing questionnaires, where both pharmacists and final customers are respondents.. Based on the survey and data provided within the survey, I will evaluate the customer satisfaction and provide the company a recommendation, which would result in increasing of the customer satisfaction.
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Dahlstrand, Christian. „Ground and Excited State Aromaticity : Design Tools for π-Conjugated Functional Molecules and Materials“. Doctoral thesis, Uppsala universitet, Fysikalisk-organisk kemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173115.
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The main focus of this thesis is on the aromaticity of the ground state and electronically excited states of π-conjugated molecules and polymers, as well as how aromaticity is connected to their properties. The electronic structures of polybenzenoid hydrocarbons (PBHs) were explored through density functional theory (DFT) calculations and the π-component of the electron localization function (ELFπ). The study revealed how the π-electronic structure is influenced by the fusion of double bonds or benzene rings to the PBHs. We also demonstrated that the π-electrons of benzene extend to accommodate as much aromaticity as possible when bond length distorted. The aromatic chameleon property displayed by fulvenes, isobenzofulvenes, fulvalenes, bis(fulvene)s, and polyfulvenes were investigated using DFT calculations. The tria-, penta-, and heptafulvenes were shown to possess ionization energies and electron affinities which can be tuned extensively by substitution, some of which even outperform TTF and TCNQ, the prototypical electron donor and acceptor, respectively. The singlet-triplet energy gap of pentafulvenes can be tuned extensively by substitution to the point that the triplet state is lower than the singlet state and thus becomes the ground state. The ELFπ of isobenzofulvene shows that the benzene ring in an electronically excited state can be more aromatic than the corresponding ring in the ground state. We have shown that the 6-ring of [5.6.7]quinarene is influenced by a Hückel aromatic resonance structure with 4n+2 π-electrons in the excited quintet state. The bis(fulvene)s which are composed of a donor type heptafulvene and an acceptor type pentafulvene, retain the basic donor-acceptor properties of the two fragments and could function as compact donor-acceptor dyads. A few of the designed polyfulvenes were found to have band gaps below 1 eV at the PBC-B3LYP/6-31G(d) level. Various 2,7-disubstituted fluorenones and dibenzofulvenes were synthesized and their excited state properties were investigated by absorption spectroscopy and time-dependent DFT calculations. It was found that the 1A → 1B transition of ππ* character can be tuned by substitution in the 2,7-positions. The 2,7-bis(N,N-dimethyl) derivatives of fluorenone and dibenzofulvene displayed low energy transitions at 2.18 and 1.61 eV, respectively, in toluene.
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Tanaka, Yasuo. „Studies on Structures and Aromaticity of meso-Aryl Expanded Porphyrins and their Metal Complexes“. 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124437.
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Pecorari, Daniel. „α-Funzionalizzazione organocatalitica enantioselettiva di aldeidi con eterocicli aromatici azotati“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13897/.
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In this work, two enantioselective syntheses catalyzed by diphenyl prolinol silyl ethers to alfa-functionalized aldehydes are presented. In the first project, N-benzylpyridinium bromides activated at the C3 position by an electron-withdrawing group (nitro or cyano) are used. The pyridine portion added to the aldehyde losing aromaticity and forming a dihydropyridine derivative. The optimization of the reaction parameters as solvent, base, catalyst, acid co-catalyst and temperature has been reported. Moreover, the generality of the reaction has been proved varying both the pyridiuum salts and the aldehydes. Finally, the relative and absolute configuration of the products were determined and explained assuming a reaction mechanism through the syncline transition state. In the second project, the enantioselective alfa-arylation of aldehydes with isquinoline N-oxides, catalyzed by diphenyl prolinol silyl ethers, has been studied. The activation of the isquinoline N-oxide has been achieved with the use of bromotripyrolidinodiphosphonium hexafluorophosphate (PyBroP). A preliminary study of the optimal reaction conditions has been carried out, which is still underway. Currently, good enantiomeric excesses and moderate to good conversions of reagents have been obtained.
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Lolli, Elisa. „il pet food: analisi della frazione aromatica e valutazione sensoriale“. Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21684/.
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Negli ultimi anni il settore del pet food ha registrato un forte incremento di interesse, spingendo le aziende produttrici ad indagare sulle variabili che incidono maggiormente sul gradimento, da parte degli animali domestici, degli alimenti a loro destinati. Si è riscontrato come, per cani e gatti, l’olfatto sia determinante per l’apprezzamento di un prodotto. Tale elaborato di tesi ha lo scopo di indagare alcuni prodotti destinati all’alimentazione degli animali, le crocchette per gatti, attraverso metodi analitici per la valutazione quali-quantitativa del profilo aromatico ed elementi di analisi sensoriale. L’elaborazione congiunta dei risultati strumentali (profilo in composti volatili) con quelli sensoriali (gradimento olfattivo da parte degli animali) risulta fondamentale per ottenere una valutazione complessiva dell’aroma del prodotto, consentendo di individuare quali possano essere i composti volatili che influenzano le preferenze alimentari dei gatti. La ricerca bibliografica iniziale è stata propedeutica per la realizzazione di una ricerca sperimentale focalizzata su 42 campioni commerciali di crocchette per gatti. Dalle analisi effettuate mediante metodologia HS-SPME-GC-MS sono stati identificati un totale di 52 composti volatili. Grazie ad un’elaborazione statistica dei risultati mediante PCA è stato possibile selezionare 36 variabili (composti volatili) maggiormente discriminanti nella caratterizzazione dei campioni. Infine, sono state esaminate le principali analogie e differenze nel profilo in composti volatili tra i campioni analizzati, anche in relazione agli ingredienti, sono state identificate le molecole caratterizzanti i campioni e, per alcune di queste, sono stati ricercati in letteratura i relativi sentori aromatici. Per questo motivo risulta essenziale continuare questi studi al fine di formulare alimenti sempre più appetibili, sostenibili e competitivi.
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Engberg, André. „Exploiting excited-state aromaticity for the design of efficient molecular motors : A quantum chemical study“. Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-162675.
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In this work, a study of a recent approach in the design of light-driven molecular motors is presented. The approach involves enabling part of the motor to obtain aromatic-like properties through photoexcitation, and is found to significantly facilitate the rotary motion by reducing the barriers normally present in the excited-state potential energy surfaces of rotary motors.
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Zheng, Pinguan. „Deantiaromatization as a driving force in an electrocyclization of cyclopentadienone and the total synthesis of 1-epi-esco-pseudopteroxazole“. Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4669.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed Mar. 4, 2008). Vita. Includes bibliographical references.
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Omatsu, Yamato. „Synthetic Study on Functionalized Oligosilanes toward Aromatic Silicon Clusters“. Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263483.
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Banella, Maria Barbara. „Sintesi e caratterizzazione di nuovi biopoliesteri aromatici a base di resorcinolo“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7316/.
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Il lavoro di tesi si inserisce in un contesto di ricerca molto attuale, che studia la preparazione di nuovi materiali polimerici ad elevate prestazioni e derivabili da fonti rinnovabili. Partendo dal resorcinolo, una molecola che può essere ottenuta da biomassa, e dall’etilene carbonato sono state ottimizzate la sintesi e la purificazione di un diolo,
l’1,3-bis(2-idrossietossi)benzene (HER), senza l’impiego di solventi e con l’utilizzo di modeste quantità di catalizzatore. L’HER è conosciuto in letteratura ma è poco studiato e non viene attualmente impiegato come monomero. In questo lavoro L’HER è stato polimerizzato in massa con una serie di diacidi (alcuni derivati da biomassa, altri
provenienti da fonti fossili) sia di natura alifatica (lineari e ciclici) che di natura aromatica. Sono state analizzate la struttura chimica e le proprietà termiche dei nuovi poliesteri, in modo da definire correlazioni fra struttura e prestazioni finali. E’ stata infine messa a punto una procedura one-pot per la preparazione dei suddetti poliesteri; essa prevede la sintesi diretta dei polimeri senza lo stadio intermedio di purificazione
dell’HER.
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Gambatesa, Antonio <1980>. „Nuovi catalizzatori per l'idrogenazione, l'idrogenolisi/ring-opening di composti aromatici policiclici“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1353/.
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The removal of aromatic hydrocarbons from diesel has received considerable attention after environmental regulations that require petroleum reï¬ners to raise cetane number and to limit aromatics in diesel fuel in order to improve combustion efficiency and reduce particulate and NOx emissions. An alternative is blending with FischerâTropsch (FT) gas-to-liquid diesel fuel; however, this option may not be economically viable solution in case of extensive blend. Another alternative is to incorporate in the diesel pool a greater fraction of the so-called light cycle oil (LCO). Due to its high aromatics content and its low cetane number (typically between 20 and 30), the incorporation of LCO may have a negative impact on the quality of diesel. Current technologies for LCO improvement are based on hydrogenation to adjust both sulphur and cetane number but while an important fraction of the aromatics present in LCO can be saturated in a deep hydrogenation process, the cetane number may still be lower than the target values specified in diesel legislations, so further upgrading is needed. An interesting technology for improving the cetane number of diesels and maintaining meanwhile high diesel yields is achieved by combining a complete hydrogenation process with a selective ring opening (SRO) reaction of the naphthenic rings. The SRO can be defined as naphthene ring-opening to form compounds with high cetane number, but without any carbon losses. Controlling the interconversion of six- and five- membered rings via an acid-catalyzed ring-contraction step is also of great importance, since selective conversion of six-membered to five-membered naphthene rings greatly inï¬uences ring-opening rates and selectivity. High intrinsic activity may be enhanced by deposition of noble metals on acidic, high surface area supports, because it is possible to arrange close proximity of the metal and acid sites. Moreover, in large-pore supports, the diffusion resistance of liquid reactants into the pores is minimized. In addition to metal centres, the acid sites of support also plays role in aromatics hydrogenation. However, the functions of different kinds of acid sites (Brønsted vs. Lewis acidity), and their optimal concentrations and strengths, remain unclear.
In the present study we investigated the upgrading of an aromatic-rich feedstock over different type of metal supported on mesoporous silica-alumina. The selective hydrogenolysis and ring opening of tetrahydronaphthalene (THN or tetralin) was carried out as representative of LCO fractions after deep hydrogenation process. In this regards the aim of this study is to evaluate both the effect of metals and that of the supports characterized by different acid distribution and strength, on conversion and selectivity. For this purpose a series of catalysts were prepared by impregnation. The catalysts were characterized and conversion tests of THN were performed in a lab-scale plant operating in the pressure range from 7.0-5.0 MPa and in the temperature range from 300 to 360°C.
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Porf?rio, Kennedy de Paiva. „Germina??o, estaquia e micropropaga??o de Xylopia aromatica (Lam.) Mart“. UFVJM, 2016. http://acervo.ufvjm.edu.br/jspui/handle/1/1383.
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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
Este trabalho teve como objetivo desenvolver procedimentos de germina??o, estaquia e micropropaga??o de Xylopia aromatica. Os experimentos foram conduzidos na Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), em diamantina ? MG, cujos trabalhos foram divididos em dois cap?tulos. No primeiro cap?tulo foram realizados oito experimentos. A germina??o foi avaliada em quatro experimentos, onde sementes de Xylopia aromatica, separadas em lotes distintos quanto ? densidade, foram submetidas ? quebra de dorm?ncia utilizando GA3 em diferentes concentra??es (0; 25; 50; 100; 250; 500; e 1000 mg L-1), nos tempos de imers?o 24 e 48 horas. N?o ocorreu germina??o durante os 210 dias de avalia??o. Foram realizados quatro experimentos de estaquia, onde segmentos caulinares (com e sem folhas) e radiculares com classes de di?metros distintas, foram imersos por 30 segundos em solu??o de AIB (0; 2000; 4000; 6000; 8000 e 10.000 mg L-1) a fim de induzir o enraizamento advent?cio. Foi avaliado o percentual de enraizamento durante 140 dias. N?o houve enraizamento em nenhum dos experimentos, porem ocorreu brota??es nas estacas caulinares que foram imersas nas concentra??es de 2000, 4000 e 6000 mg L-1 de AIB. No segundo cap?tulo, foram realizados seis experimentos, que envolveram etapas de multiplica??o, alongamento e enraizamento in vitro. Explantes foram submetidos a diferentes meios de cultura (MS e WPM), e concentra??es de BAP (0,5 e 0,8 mg L-1), objetivando determinar o melhor meio de cultura e concentra??o de BAP para a multiplica??o da esp?cie. Avaliou-se tamb?m, o alongamento em explantes com o uso de combina??es de ANA e BAP e GA3, e enraizamento com o uso de AIB e ANA. O meio MS acrescido de 0,8 mg L-1 de BAP foi o que apresentou melhores resultados para a multiplica??o de Xylopia aromatica. Na fase de alongamento, o GA3 na concentra??o de 5,0 mg L-1 foi o regulador de crescimento que apresentou melhor resultado em altura e n?mero de folhas. No enraizamento, o AIB e o ANA n?o foram eficazes na indu??o de ra?zes, necessitando mais estudos relacionados ? etapa de enraizamento para a esp?cie.
Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Ci?ncia Florestal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2016.
This study aimed to develop germination procedures, cutting and micropropagation Xylopia aromatica. The experiments were conducted in Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM) in Diamantina - MG, whose works were divided into two chapters. In the first chapter were carried out eight experiments. Germination was evaluated in four experiments where aromatica Xylopia seeds, separated into separate lots for density, were submitted to dormancy breaking using GA3 at different concentrations (0, 25, 50, 100, 250, 500, and 1000 mg L-1) under immersion for 24 and 48 hours. Not germinated during the 210 days of evaluation. Four cutting experiments were carried out where segments shoot (with and without leaves) and root with different diameter classes were immersed for 30 seconds in AIB solution (0; 2000; 4000; 6000; 8000 and 10,000 mg L-1) to induce adventitious roots. Rooting percentage was evaluated during 140 days. There was no rooting experiments, however sprouting occurred in the cuttings were dipped in concentrations of 2000, 4000 and 6000 mg L-1 AIB. In the second chapter, we were conducted six experiments, involving multiplication steps, stretching and in vitro rooting. Explants were subjected to different culture medium (MS and WPM) and BAP (0,5and 0,8mg L-1), in order to determine the best medium and concentration of BAP for the multiplication of the species. It also evaluated the elongation explants using combinations of ANA and BAP and GA3 and rooting using AIB and ANA. The MS medium plus 0.8 mg L-1 BAP showed the best results for the multiplication of Xylopia aromatica. In the stretching step, the concentration of GA3 at 5,0 mg L-1 was the growth regulator showed better results in height and leaf number. Rooting, AIB and ANA were not effective in inducing roots, requiring more studies related to the rooting stage for the species.
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Baggett, Andrew William. „New Strategies Enabling Diverse Functionalization of Aromatic 1,2-Azaborine Motifs“. Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:105027.
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Thesis advisor: Shih-Yuan LiuDescribed herein are four projects focused on the elaboration of aromatic 1,2-azaborine core structures through late-stage functionalization strategies. In the first chapter, the gram scale, protecting group-free synthesis of the direct BN isostere of benzene is developed. This protocol is used to produce large quantities of pure 1,2-azaborine suitable for use in fundamental investigations. Second, the first general solution for the functionalization of the C4, C5, and C6 ring positions of 1,2-azaborines is described, featuring iridium catalyzed C-H borylation as the key strategy. Azaborine boronates produced via this method are successfully elaborated through cross coupling and oxidation to access azaborines that serve as N,N-ligands for electrophilic boron sources. The third project is an extension of the borylation/cross coupling project, and introduces the first polymer consisting of repeating azaborine units that displays highly efficient extension of conjugation along the azaborine chain. Finally, a copper catalyzed radical process is developed that enables removal of azaborine boron protecting groups during synthetic routes to simple azaborine targets of high interest
Thesis (PhD) — Boston College, 2016
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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Soya, Takanori. „Studies on Novel Gigantic Expanded Porphyrins“. Kyoto University, 2019. http://hdl.handle.net/2433/242632.
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Higashino, Tomohiro. „Chemistry of Novel Expanded Porphyrins with Main Group Elements“. 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/189635.
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Yoneda, Tomoki. „Novel π-Conjugation Circuits and Coordination Structures of Metalated Expanded Porphyrins“. 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199132.
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Junqueira, João Gabriel Moraes. „Estudo químico de Annona coriacea Mart. E Xylopia aromatica (Lam.) Mart. (Annonaceae)“. Universidade Federal de Goiás, 2015. http://repositorio.bc.ufg.br/tede/handle/tede/5169.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
CHAPTER 01: CHEMICAL STUDY OF VOLATILE ORGANIC COMPOUNDS Annona coriacea Mart. AND Xylopia aromatica (Lam.) Mart (Annonaceae) - In this research was performed the study of the chemical profile of the volatile organic compounds (VOCs) of flowers and leaves of species Annona coriacea and Xylopia aromatica (Annonaceae) by means of extraction in vivo and in vitro, through the techniques headspace-solid phase microextraction (HS-SPME), hydrodistillation and characterization by gas chromatography-mass spectrometry (GC-MS). By the analysis of the volatile fraction of flowers and leaves of A. coriacea it was observed different VOCs, according to the coatings utilized, since the selection of the fiber becomes one of the main factors for VOCs analysis in different vegetables parts. The chemical profile of the flowers of X. aromatica was obtained through HS-SPME, which compared the efficiency of in vivo and in vitro extractions, due to the higher number of VOCs present in the floral aroma. Once were obtained various chemical data, the multivariate analysis of the data was performed, which provided relevant information, contributing to the optimization of some conditions, such as selection of fiber, extraction time and extraction temperature yielded the characterization of the most number of VOCs. In this context, the conditions that presented the most promising results were: fibers CAR/PDMS and PA, extraction time equal the 60 min and extraction temperature of 29 °C. The essential oil of the flowers of X. aromatica was obtained by hydrodistillation and chemically characterized by GC-MS. The major compound present was the pentadecan-2-one (16.38%). The extraction techniques utilized were helpful, however there was qualitative and quantitative variation of VOCs, which is expected due to the extraction process be different. Thus, it is observed that depending on the objective of the survey or that searches for in the volatile fraction, it is necessary to use the technique to give the most promising results for the investigation held or in order to complement each other. In this way, the study of A. coriacea and X. aromatica contributed to the knowledge of the chemical profile of VOCs present in these species, seen from these investigations that the same can be applied in several industrial areas, for example cosmetic, food, among others.
CAPÍTULO 01: ESTUDO QUÍMICO DOS COMPOSTOS ORGÂNICOS VOLÁTEIS DE Annona coriacea Mart. E Xylopia aromatica (Lam.) Mart (Annonaceae) - Nesta pesquisa realizou-se o estudo do perfil químico dos compostos orgânicos voláteis (COVs) das flores e folhas das espécies Annona coriacea e Xylopia aromatica (Annonaceae), por meio da extração in vivo e in vitro, através das técnicas de headspace-microextração em fase sólida (HS-SPME), hidrodestilação e caracterização via cromatografia gasosa acoplada à espectrometria de massas (CG-EM). Pela análise da fração volátil das flores e folhas de A. coriacea observou-se COVs diferentes, de acordo com os revestimentos usados, visto que a seleção da fibra se torna um dos principais fatores para a análise de COVs em partes vegetais diferentes. O perfil químico das flores de X. aromatica foi obtido via HS-SPME, em que se comparou a eficiência das extrações in vivo e in vitro, em função do maior número de COVs presentes no aroma floral. Uma vez que foram obtidos vários dados químicos, foi realizada a análise multivariada dos mesmos, a qual forneceu informações relevantes, contribuindo para a otimização de algumas condições, tais como seleção da fibra, tempo de extração e temperatura de extração que rendessem a caracterização do maior número de COVs. Neste contexto, as condições que apresentaram os resultados mais promissores foram: fibras de CAR/PDMS e PA, tempo de extração igual a 60 min e temperatura de extração de 29 oC. O óleo essencial das flores de X. aromatica foi obtido por hidrodestilação e caracterizado quimicamente por CG-EM. O composto majoritário presente foi a pentadecan-2-ona (16,38%). As técnicas de extração utilizadas foram úteis, entretanto houve variação quali e quantitativa dos COVs, o que é esperado devido ao processo de extração ser diferente. Assim, observou-se que dependendo do objetivo da pesquisa ou do que se procura na fração volátil, faz-se necessária a utilização da técnica que dê os resultados mais promissores para a investigação realizada ou de forma que se complementem. Desta maneira, o estudo de A. coriacea e X. aromatica contribuiu para o conhecimento do perfil químico dos COVs presentes nestas espécies, visto que a partir destas investigações os mesmos podem ser aplicados em várias áreas industriais, por exemplo cosmético, alimentos, dentre outros.
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Métivier, Pascal. „Synthese organique assistee par ordinateur : l'approche synthetique“. Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13190.
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Deux programmes fonctionnant dans le sens synthetique, c'est a dire permettant de simuler les reactions, ont ete realises l'un a l'universite louis pasteur a strasbourg (france), et l'autre, a l'universite john purdue (usa). Ce memoire decrit les choix developpes lors de la realisation de ces programmes ainsi que leur fonctionnement. Differents aspects, tels la reconnaissance des caracteristiques d'interet synthetique d'une molecule, un modele de la chimie nucleophile ainsi qu'un modele des reactions de reductions, correspondant au travail d'interet chimique effectue sont particulierement detaillees. Ce memoire se termine par un etude comparative des deux programmes quant aux aspects chimiques et informatiques qui y sont impliques
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Zubarev, Dmitry Yu. „Analysis of Chemical Bonding in Clusters by Means of The Adaptive Natural Density Partitioning“. DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/13.
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Models of chemical bonding are essential for contemporary chemistry. Even the explosive development of the computational resources including, both hardware and software, cannot eliminate necessity of compact, intuitive, and efficient methods of representing chemically relevant information. The Lewis model of chemical bonding, which was proposed eleven years before the formulation of quantum theory and preserves its pivotal role in chemical education and research for more than ninety years, is a vivid example of such a tool. As chemistry shifts to the nanoscale, it is becoming obvious that a certain shift of the paradigms of chemical bonding is inescapable. For example, none of the currently available models of chemical bonding can correctly predict structures and properties of sub-nano and nanoclusters. Clusters of main-group elements and transition metals are of major interest for nanotechnology with potential applications including catalysis, hydrogen storage, molecular conductors, drug development, nanodevices, etc. Thus, the goals of this dissertation were three-fold. Firstly, the dissertation introduces a novel approach to the description of chemical bonding and the algorithm of the software performing analysis of chemical bonding, which is called Adaptive Natural Density Partitioning. Secondly, the dissertation presents a series of studies of main-group element and transition-metal clusters in molecular beams, including obtaining their photoelectron spectra, establishing their structures, analyzing chemical bonding, and developing generalized model of chemical bonding. Thirdly, the dissertation clarifies and develops certain methodological aspects of the quantum chemical computations dealing with clusters. This includes appraisal of the performance of several computational methods based on the Density Functional Theory and the development of global optimization software based on the Particle Swarm Optimization algorithm.
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Ruffin, Hervé. „Influence d'un habillage sur les propriétés de coordination d'hexaphyrines : vers des nouveaux récepteurs moléculaires à conformation et aromaticité modulables“. Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S086/document.
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Les hexaphyrines sont des macrocycles constitués de six unités pyrroliques, elles possèdent des propriétés physico-chimiques intéressantes, dont notamment leur capacité à exister sous deux états oxydés stables, à 26 et 28 électrons π délocalisés. Elles peuvent coordonner jusqu’à deux cations métalliques au sein du macrocycle, cependant elles souffrent d’un manque de réactivité et de prédictibilité quant à la nature des complexes formés. Pour pallier à ces problèmes, nous avons décidé de suivre une stratégie de post-modification du macrocycle, mettant en jeu l’incorporation sans précédent d’un habillage périphérique ou apical fonctionnel. Nous avons cherché à diversifier la nature de l’habillage, en travaillant dans un premier temps sur des fonctions acides carboxyliques portées par un bras, puis par une anse dans le but d’augmenter la préorganisation du système. Cette stratégie s’est montrée fructueuse et durant les études de coordination, quatre cations métalliques, le ZnII, le CdII, le PbII ainsi que le HgII ont montré des réactions de métallations instantanées et inédites à température ambiante. Dans un second temps, nous avons étudié l’influence d’un habillage tripodal sur les propriétés de coordination du macrocycle hexaphyrinique. La métallation dans des conditions spécifiques de ces nouvelles hexaphyrines, a mis en évidence la première synthèse hautement diastéréosélective d’un complexe aromatique avec une topologie en anneau de Möbius. Cette synthèse nous à servi de preuve de concept sur le développement de potentiels détecteurs chiroptiques, basés sur un changement de topologie et d’aromaticité du ligand après métallation induit par l’analyteHexaphyrins are six-pyrrole member macrocycles, which possess several interesting physico-chemical properties, and specially their abilities to exist as two stable oxidation states. They also can coordinate two metallic cations, unfortunately they suffer from a lack of reactivity and from unpredictable behaviors regarding the nuclearity of the complexes. To overcome these problems, we decided to follow a macrocycle post-modification strategy, using the unprecedented peripheral dressing of the hexaphyrin. We tried to explore few functions and started working with carboxylic acid groups on a piquet and then on a strap to extend the preorganization of the coordinated function. This strategy showed good results and instantaneous metalation with four metalics cations, ZnII, CdII, PbII and HgII at room temperature. Meanwhile we studied the behavior in coordination chemistry of novel tren-capped hexaphyrin. Thus we highlight the first diastereoselective synthesis, involving the formation of complexes showing Möbius strip topology. This system was used as proof of concept for the development of potential chiroptical sensors, based on a topology switch after metalation triggered by the analyte
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Gon, Rikhi. „Identification of Genes Induced under Anaerobic Benzene-Oxidizing Conditions in Dechloromonas aromatica strain RCB“. OpenSIUC, 2010. https://opensiuc.lib.siu.edu/dissertations/242.
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Benzene (C 6H6) is the simplest member of the aromatic hydrocarbon group of chemical compounds. Minute amounts of benzene are naturally released into the environment during volcanic eruptions and forest fires. This extremely stable aromatic compound is also an important industrial chemical and is an integral component of many petroleum products. In fact, benzene is amongst the top 20 in production volume for chemicals produced in the United States. Therefore, it is not surprising that the major reason for environmental contamination through benzene is by anthropogenic sources. Benzene is relatively soluble in water and migrates very quickly in the soil after its entry. The Environmental Protection Agency (EPA) has classified benzene as a Class A carcinogen. Microorganisms play an integral role in the natural attenuation of benzene from the environment. Biodegradation of benzene by oxidation can occur under aerobic, anaerobic and microaerophilic conditions. Biooxidation of benzene under aerobic conditions is well-studied. However, oxygen is scarce in contaminated subsurface environments, and after the aerobic breakdown of benzene, oxygen is quickly depleted from the most heavily contaminated regions leading to the development of extensive anaerobic zones. As a result, there is increased focus on anaerobic benzene degradation as a potential bioremediation technique in anoxic subsurface environments. In aerobic and microaerophilic environments, monooxygenase and dioxygenase enzyme systems have been established to be involved in the breakdown of the benzene ring. However, the genes and enzymes involved in anaerobic benzene oxidation pathway are still unknown. In the present study, Dechloromonas aromatica strain RCB, capable of benzene oxidation with nitrate as the electron acceptor, was used as a model system to investigate the initial steps of the anaerobic benzene oxidation pathway. Strain RCB is capable of completely mineralizing benzene to carbon dioxide in denitrifying conditions. RNA-arbitrarily primed polymerase chain reaction (RAP-PCR), a differential gene expression technique used to randomly reverse-transcribe RNA into cDNA, was conducted to identify genes exclusively expressed during nitrate-dependent benzene oxidation. A total of seven genes were identified as differentially expressed in the presence of benzene using the RAP-PCR approach. Four differentially expressed genes were confirmed by a second method, semiquantitative reverse transcriptase PCR (RT-PCR). Microarray analysis was the second expression analysis technique conducted to identify genes expressed during benzene-oxidizing conditions. Based on fold induction and potential function, six genes were selected from the microarray data and their differential expression was confirmed by using semiquantitative RT-PCR. Interestingly, Daro1556, encoding a hypothetical protein, was identified by both RAP-PCR and microarray analysis. In order to verify the functions of the genes (selected from RAP-PCR and microarray analysis) in nitrate-dependent benzene oxidation, six deletion mutants were constructed in which the target gene was replaced by a tetracycline cassette. The correct insertion of the tetracycline cassette in the mutant genome was confirmed by PCR and Southern blotting. Microarray results were further analyzed by using an unsupervised clustering approach, k-means. A couple of genes (Daro1358 and Daro1359) obtained from cluster analysis were also verified by semiquantitative RT-PCR. These two genes, part of the same operon, encode a two-component monooxygenase system, which is a member of the Rieske non-heme iron aromatic ring-hydroxylating oxygenase family of proteins. In the present investigation, for the first time, involvement of a monooxygenase system (Daro1358 and Daro1359) during benzene oxidation with nitrate reduction was observed. Based on the results obtained from k-means cluster analysis, a model was hypothesized for anaerobic benzene oxidation with nitrate as the electron acceptor in Dechloromonas aromatica strain RCB.
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Chatterjee, Mohor. „Identification and Characterization of Two Thauera aromatica Strain T1 Genes Induced by p-Cresol“. Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1343934518.
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Pittman, Eddie LaReece. „Computed NMR shielding values of unsaturated five-membered-heterocyclic ring compounds and their benzo-analogs as a measure of aromaticity“. View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-2/r1/pittmane/eddiepittman.pdf.
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Culberson, Lori. „Molecular Electronic Structure via Photoelectron Imaging Spectroscopy“. Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301677.
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This dissertation explores the use of photoelectron imaging spectrometry to probe the molecular electronic structure of various chemical systems, with an emphasis on photoelectron angular distributions. Experimental ion generation, mass selection, laser photodetachment, and photoelectron ion imaging were all done in a photoelectron imaging spectrometer described in detail. Results from simplistic systems, OH- and CH-, are used to illustrate the general and fundamental capabilities of imaging spectroscopy and angular distributions. This illustration is then expanded when both qualitative and quantitative analyses of photoelectron angular distributions are used to aid in the understanding of the electronic structure of several heterocyclic aromatic systems. First a qualitative analysis aids in the exploration of the electronic structure of thiophenide, C₄H₃S⁻, and furanide, C₄H₃O⁻. Ground and excited C₄H₃S and C₄H₃O radical states are observed, and bond dissociation energies are defined. Next, a new model used to qualitatively analyze photoelectron angular distributions resulting from mixed s - p hybrid states is presented and applied to detachment from pyridinide, C₅H₄N⁻; as a benchmark system. Before further exploring this model, the synthesis of several deuterated heterocyclic compounds is presented in order to determine the experimentally produced systems in our experimental setup. The electronic structure of the resultant molecules oxazolide, C₃H₂NO⁻, and thiazolide, C₃H₂NS⁻; are then investigated. Using this new qualitative model, the mixed s - p states model, to evaluate the angular distributions of the systems, the hybridization of the anion molecular orbitals is probed. Comparison of the photoelectron angular distributions that are modeled for each heterocyclic aromatic system yields several trends relating aromatic stabilization, molecular hybridization, and bond dissociation energies. A new qualitative model is then presented to evaluate photoelectron angular distributions resulting from mixed p - d states and applied to detachment from NO⁻. Finally, new ideas and directions are proposed.
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Maynor, Marc Steven. „SYNTHESIS, PROPERTIES, STRUCTURAL CHARACTERIZATION, AND REACTIVITY OF LOW-VALENT TITANIUM (BISDIIMINE) COMPLEXES“. UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_theses/210.
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The synthesis, structure, and reactivity of titanium bis(diimine) complexes supported by 1,2-alternate dimethylsilyl-bridged p-tert-butylcalix[4]arene dianion and 2,2' methylene-bridged 4-methyl, 6-tertbutyl phenol ligands is reported. The molecular structure of [(DMSC)Ti(bpy)2] (28) and [(MBMP)Ti(bpy)2] (55) was characterized by X-ray crystallography. Complexes [(DMSC)Ti(bpy)2] (28), [(DMSC)Ti(dmbpy)2] (29), and [(DMSC)Ti(phen)2] (30) undergoes light-assisted reactions with two or more equivalents of (C6H5)2CO or (p-MeC6H4)2CO to give the corresponding 1-aza-5-oxa-titanacyclopentene complexes 37-42. Similar reactivity was observed with [(MBMP)Ti(bpy)2] (55), [(MBMP)Ti(dmbpy)2] (56), and [(MBMP)Ti(phen)2] (57). The molecular structure of [(MBMP)Ti{kappa-3-OC(C6H5)2C10H7N2}{OCH(C6H5)2}] (58) was characterized by 1H and 13C NMR as well as X-Ray crystallography.