• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 242
  • 56
  • 54
  • 35
  • 13
  • 8
  • 5
  • 5
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 545
  • 545
  • 108
  • 92
  • 91
  • 90
  • 87
  • 77
  • 61
  • 60
  • 59
  • 55
  • 53
  • 53
  • 49
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
351

induction de chiralité supramoléculaire : vers de nouveaux nano-objets chiro-optiques hybrides / supramolecular chirality induction : toward new hybrid chiroptical nano-objects

Scalabre, Antoine 01 October 2019 (has links)
La polarisation de la lumière, bien que connue depuis fort longtemps, pourrait être plus exploitée. Cependant, de plus en plus d’entreprises de pointe dans les domaines de la sécurité et la transmission d’information commencent à l’utiliser. Une raison de la sous-exploitation actuelle de la polarisation vient des méthodes de polarisation, qui ont une transmission de la lumière limitée (généralement jusqu’à 45%). Afin d’outrepasser cette limite physique, un moyen est d’utiliser des matériaux fluorescents émettant une lumière polarisée. Cependant, la synthèse et la purification de tels matériaux sont compliquées et obtenir les deux énantiomères n’est pas toujours possible. Ce travail se concentre sur une nouvelle méthode de synthèse, plus simple, utilisant des nano-structures hybrides ou inorganiques hélicoïdale, et des luminophores organiques pouvant interagir ensemble. L’agrégation chirale des chromophores autour des structures formera ainsi des nano-objets fluorescents chiraux. Le premier chapitre explique comment la chiralité est aujourd’hui présente dans tous les domaines et à toutes les échelles, des molécules aux objets du quotidien. Nous y étudierons également l’induction de la chiralité à différentes échelles. Le second aspect de ce travail, l’interaction lumière-matière, sera également mis en avant, aussi bien concernant l’absorption que l’émission lumineuse, mais aussi en quoi l’assemblage des molécules peut affecter ces propriétés. Nous nous pencherons également sur les cas très particuliers du dichroïsme circulaire et de la luminescence circulairement polarisée. Pour finir, nous verrons quels sont les matériaux actuels existant pour obtenir ces propriétés et quels sont leurs inconvénients. Afin d’outrepasser ces défauts, nous avons choisi d’utiliser deux systèmes. Le premier, constitué de nano-hélices organiques dans une coque de silice a pour avantage d’utiliser à la fois une induction de chiralité par assemblage des chromophores organiques, mais aussi une seconde induction de la chiralité à l’échelle moléculaire. L’inconvénient étant que ce système n’est pas très robuste à un changement d’environnement. Pour résoudre cet inconvénient, nous n’avons conservé, dans un second temps, que la coque de silice afin de l’utiliser comme patron pour supporter le greffage covalent de luminophores à sa surface. Dans le second chapitre, la méthode de synthèse des nano-structures sera présentée. De même le choix des différents luminophores utilisés dans ces travaux sera justifié, et leur voie de synthèse, expliquée. Enfin, les différentes méthodes de caractérisation seront détaillées. Le troisième chapitre portera sur les résultats obtenus lors de l’intégration de chromophores non-chiraux dans les hélices hybrides, ou leur de greffage sur les structures inorganiques. Nous y verrons l’importance à la fois de l’assemblage intermoléculaire, mais aussi de l’interaction avec un environnement chiral, pour l’induction de chiralité dans le but d’obtenir dichroïsme circulaire et luminescence circulairement polarisée. Les différents chromophores utilisés y sont présentés et comparés permettant la mise en évidence des principaux facteurs aidant à l’induction de chiralité pour chaque type de structure. Enfin, un dernier chapitre s’intéressera à des systèmes plus complexes utilisant des molécules présentant en solution des propriétés chiro-optiques, ou ayant la capacité de s’agréger en nano-structures ayant de telles propriétés, et ce afin de savoir si leurs propriétés sont ajustables grâce à l’utilisation des hélices hybrides pour leur imposer une agrégation spécifique. Une dernière approche a également été étudiée, en synthétisant des quantum-dots carbonés fluorescents à partir des nano-structures hybrides. Ces quantum-dots, s’ils conservent la forme de la structure initiale, pourraient posséder un dichroïsme circulaire et une luminescence circulairement polarisée sans besoin de les complexer avec une molécule chirale. / The polarization of light, despite being known since long time, is recently at the center of renewed interest. More and more high technology companies in the fields of safety and information transmission are starting to exploit this property. One bottleneck for their use comes from the limitation in the light transmission of current methods of polarization (typically up to 45%). In order to overpass this physical limitation, one possible approach would be to use fluorescent materials emitting polarized light. However, the synthesis and purification of such materials is complex and obtaining both enantiomers is not always possible. The current work focus on a new synthetic pathway, possibly simpler and more versatile, using chiral hybrid or inorganic nano-helices and organic fluorophores interacting together. The aggregation of chromophores around the template will form chiral fluorescent nano-objects. The first chapter explains how chirality is present in many fields and at every scale, from molecules to daily objects. We will discuss the way of inducting or transferring chirality. The second facet of this work, light-matter interactions, will also be explained, concerning both absorption and emission of light, but also on how molecular assembly can affect these properties. We will study into detail the very particular case of circular dichroism and circularly polarized luminescence. Finally, we will see the existing systems that are used to obtain these properties and the drawback of these materials. In this work, we chose to use two systems. The first, constituted of organic nano-helices in a silica shell, has the advantage of using the organic template confined in chiral nano-space to induce chirality to the organic chromophores in interaction with them molecularly, but also through aggregation due to the confinement. The disadvantage being that this system is not robust toward environmental changes. The alternative approach is to use the silica shell as an inorganic template for the covalent grafting of fluorophores onto its surface. In the second chapter, the method for the synthesis of nano-structures is described, along with an explanation on the choice and synthesis of the chromophores used in this study. Finally, the characterization processes used are detailed. The third chapter will focus on the results we obtained when integrating achiral chromophores into hybrid helices or by grafting then onto the silica surface. We will see the importance of the intermolecular assembly and of the interaction with a chiral environment to obtain circular dichroism and circularly polarized luminescence through chiral induction. Various fluorophores are presented and compared allowing the understanding of the key parameters for chirality induction of each type of structure.In the last chapter, more complex systems are studied using molecules presenting chiroptical properties in solution state or having the ability to form self-assemblies showing such properties. The objective will be to tune the chiroptical properties of these chromophores, by the use of hybrid helices to force a specific organization. The last part will focus on the synthesis of fluorescent carbon based quantum dots using hybrid structures. These quantum dots, can retain the shape of the original structure and show circular dichroism or circularly polarized luminescence without needing to form a complex with an external source of molecular chirality.
352

Supramolecular approaches to graphene : generation of functional hybrid assemblies / L'approche supramoléculaire appliquée au graphène : production d'assemblées hybrides fonctionnalisées

Haar, Sébastien 30 September 2015 (has links)
Cette thèse démontre le potentiel dont dispose l’exfoliation en phase liquide du graphite dans le but d’obtenir des feuillets de graphène dispersés dans un solvant organique. Ainsi le mécanisme d’exfoliation a été étudié en profondeur, en particulier, l’influence de plusieurs paramètres (température, puissance et solvants). Le choix de ses paramètres se montre crucial dans le contrôle du procédé, et pour l’obtention des feuillets de graphène ayant une taille ciblée. Il est donc possible de fabriquer des nano-feuillets de quelques dizaines de nanomètre qui en plus possèdent des propriétés de photoluminescence.Dans le but de comprendre le mécanisme d’exfoliation en phase liquide assistée par des molécules, une nouvelle approche a été mise au point : l’approche supramoléculaire. Cette approche se base sur l’utilisation de surfactants d’un nouveau type. En effet, les molécules sélectionnées possèdent une longue chaine alkyle. Cette chaine s’adsorbe sur la surface du graphène et permet de stabiliser les feuillets lors de l’exfoliation. L’influence de la taille de la chaine alkyle de ces molécules lors de l’exfoliation a été vérifiée. De plus, ces molécules ont été équipées de différentes fonctions supramoléculaires afin qu’elles puissent former des dimères sur la surface du graphène. L’ajout de ces molécules augmente non seulement le rendement d’exfoliation mais aussi le nombre de mono-feuillets présents dans ces dispersions. Ces dispersions présentent des propriétés conductrices lorsqu’elles sont déposées sur des substrats. Une nouvelles méthode de déposition a été mise au point afin d’améliorer et d’augmenter la conductivité mais aussi le pourcentage de transparence. / This thesis demonstrates the potential of exfoliation of the graphite in the liquid phase in order to obtain graphene sheets dispersed in an organic solvent. Thus the exfoliation mechanism has been studied, in particular, the influence of several parameters (temperature, power and solvents). The choice of parameters is actually crucial for the control of the process, and to obtain graphene sheets having a targeted size. It is therefore possible to manufacture nanosheets of several tens of nanometers, which in addition exhibit photoluminescence properties.In order to understand the exfoliation mechanism in liquid phase assisted by molecules, a new approach has been developed: the supramolecular approach. This approach is based on using a new type of surfactant. Indeed, the selected molecules carry a long alkyl chain. This chain is adsorbed on the surface of graphene and can stabilize the sheets during exfoliation. The influence of the size of the alkyl chain of these molecules during exfoliation was verified. Furthermore, these molecules have been equipped with various supramolecular functions, which can form dimers on the surface of graphene. The addition of these molecules not only increases exfoliation performance but also the number of mono-layers present in these dispersions. These dispersions have conductive properties when deposited on substrates. A new deposition method was developed to enhance and increase conductivity but also the percentage of transparency.
353

Crystal Engineering of Metal-Carboxylate Based Coordination Polymers

Lu, Jianjiang 29 April 2004 (has links)
This dissertation endeavors to delineate practical paradigms for crystal engineering based upon the understanding of supramolecular chemistry and self-assembly, i.e. the design and synthesis of novel functional crystalline materials. Two basic metal-organic building units, Zn(RCO2)2(py)2 and (L2)M2(RCO2)4 (M = Zn, Cu), as well as nano-scaled secondary building units (nSBUs) that are constructed from Cu2(RCO2)4 are researched and discussed. Design strategies have been developed to propagate these metal-organic synthons into predictable coordination polymer networks. A series of crystal structures, as well as their syntheses and characterization, are presented. This work demonstrates that supramolecular structures can be designed from pre-selected molecular precursors with the consideration of chemical functionalities and geometrical arrangements. The design strategy represents a practical paradigm for the construction of porous materials as well as interesting networks with special topologies. The modular nature of these metal-organic building units introduces a broad impact on the discovery of novel coordination compounds with potential useful properties.
354

Química supramolecular de complexos ter-imínicos de ferro(II) / Supramolecular chemistry of ter-imine Iron(II) complexes

Mangoni, Ana Paula 28 June 2019 (has links)
A química dos complexos de bis(ter-iminas) de ferro(II) contendo os ligantes tridentados fenilterpiridina (phtpy), piridilterpiridina (pytpy), fenilterpirazina (phtpz) e piridilterpirazina (pytpz) foi tratada nesta Tese. Os complexos exibem configuração de spin baixo, exibindo coloração violeta intensa decorrentes de transições de transferência de carga do ferro(II) para a ter-imina, dπ − pπ*. Suas configurações lineares rígidas mostram-se adequadas para a realização de montagens supramoleculares com íons de metais de transição, explorando a ligação entre os grupos piridina e pirazina, e este aspecto distinto foi especialmente focado neste trabalho. A química sintética dos ligantes, obtidos a partir do método de Kröhnke modicado, e dos complexos bis-substituídos foi aqui elaborada com excelentes resultados. A caracterização dos ligantes e dos complexos foi realizada a partir de análises de CHN, espectroscopia eletrônica, RMN e Raman, espectrometria de massas e voltametria cíclica. Os estudos teóricos foram realizados utilizando métodos semi-empíricos ZINDO/S. Todos os complexos exibem forte efeito Raman ressonante associado ao cromóforo ferro(II)ter-imínico. Os grupos piridil e pirazil (L) podem ser protonados em soluções fortemente ácidas, e também podem atuar como ligantes pontes formando uma série de sucessivos complexos de bi à heptanucleares, com o íon pentacianidoferrato(II). Tais complexos exibem novas bandas de transferência de carga no visível, refletindo as propriedades eletrônicas do cromóforo periférico {FeII(CN)5L}. Seus espectros de Raman ressonante foram investigados em comparação com os complexos mononucleares correspondentes. Na presença de íons de metais de transição, Mn(II), Co(II), Ni(II), Cu(II), Zn(II) e Fe(III), os complexos supra-moleculares de pentacianidoferrato(II) formam uma série de compostos análogos ao Azul da Prússia, produzindo filmes moleculares de grande interesse como novos materiais poliméricos e eletrocatalíticos. / The chemistry of bis(ter-imine)iron(II) complexes containing the phenylterpyridine (phtpy), pyridylterpyridine (pytpy), phenylterpyrazine (phtpz) and pyridylterpyrazine (pytpz) tridentate ligands is dealt with in this Thesis. The complexes exhibit low spin configuration, displaying strong red-violet colors arising from iron(II) to ter-imine, dπ − pπ* charge-transfer transitions. Their rigid linear configurations proved suitable for performing supramolecular assemblies with transition metal ions, by exploring the bridging pyridine and pyrazine moieties, and this distinct aspect has been specially focused on this work. The synthetic chemistry of the ligands, obtained from the Kröhnke method, and of the bis-substituted complexes was here elaborated with excellent results. Characterization of the ligands and complexes was carried out based on CHN analyses, electronic, NMR and Raman spectroscopy, mass spectrometry and cyclic voltammetry. Theoretical studies were carried out using ZINDO/S semiempirical methods. All the complexes exhibit strong resonance Raman effect associated with the iron(II) ter-imine chromophore. The pyridyl and pyrazyl groups (L) can be protonated in strongly acidic solutions, and can also act as bridging ligands forming a series of successive, bi-to-heptanuclear complexes with the pentacyanidoferrate(II) ion. Such complexes display new charge-transfer bands in the visible, reflecting the electronic properties of the {FeII(CN)5L} peripheral chromophore. Their resonance Raman spectra have been investigated in comparison with the corresponding mononuclear complexes. In the presence of transition metal ions, Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Fe(III) ions, the pentacyanidoferrate(II)-supramolecular complexes form a series of Prussian blue type of compounds, yielding molecular films of great interest as new conducting polymeric and electrocatalytic materials.
355

Supramolecular chemistry and synthesis of Cucurbit[n]uril

White, Tim, Chemistry, Australian Defence Force Academy, UNSW January 2003 (has links)
The recently discovered cucurbit[n]uril are a range of macrocyclic hosts which have enormous potential in industrial, medical and academic applications. Cucurbit[n]uril have a rigid repeating structure of methylene bridged glycouril, which give cucurbit[n]uril their gourd like shape of a cavity with two carbonyl fringed portals. In this thesis the host-guest binding abilities of three cucurbit[n]uril (n = 6, 7, 8) have been examined for a range of potential guests. These guests ranged from simple alkyl amines through globular alkyl and carboranyl amines to bipyridyl systems. In total 45 guest molecules where examined. Most of the guests examined where either cationically charged, capable of hydrogen binding, contained a substantial molecular dipole, or a combination of these. Furthermore, all of the potential guests examined had some solubility in an acidified aqueous sodium sulfate solution within which the host-guest properties were examined. It was generally found that the larger guests did have selectivity for the larger hosts. However, when the host became too large weaker complexes would form and for the range of materials examined here cucurbit[7]uril was found to be the 'best' host system. In one example, p-xylene diamine, a 2:1 complex with cucurbit[8]uril was observed. While not the focus of this work a new rapid purification method was developed for the cucurbit[n]uril using different metal ions to either solubilise or precipitate the different cucurbit[n]uril. In the second part of this work these same guest molecules where used as potential templates in the synthesis of cucurbit[n]uril. Surprisingly the guests that bound strongly to an individual host did not seem to template the cucurbit[n]uril synthesis at all. Rather these strong binders inhibited the reaction such that little or no cucurbit[n]uril formed under the reaction conditions studied. However, several examples provided excellent template results. Indeed the results indicate that guests which bound with intermediate rates of exchange are the best templates and using templates under these conditions we have been able to produce cucurbit[7]uril as 46% by mass of the total cucurbit[n]uril product. This is the highest yield ever recorded for cucurbit[7]uril and it is the first example of cucurbit[7]uril being the major product of this condensation reaction. In an another example cucurbit[8]uril formed 18% of the product an increase of 150% over the standard reaction conditions. While studying both the template reactions and the host-guest binding properties of the cucurbit[n]uril a new supramolecular form, an 'inverse rotaxane' was discovered. Inverse rotaxanes are not held in place by large blocking groups, rather the molecular structure encapsulated by the cucurbit[n]uril host prevents decomplexation of the axle.
356

Exploring Molecular Interactions : Synthesis and Studies of Clip-Shaped Molecular Hosts

Polavarapu, Anjaneya Prasad January 2007 (has links)
<p>Molecular recognition via noncovalent interactions plays a key role in many biological processes such as antigen-antibody interactions, protein folding, the bonding and catalytic transformation of substrates by enzymes, etc. Amongst these noncovalent interactions, electrostatic interactions, hydrogen bonding, π-π interactions, and metal-to-ligand bonding are the most prominent. Exploring noncovalent interactions in host-guest systems that range from small hydrocarbon systems to more complex systems is the main motivation of this thesis. The present study involves the design, synthesis and characterization of clip-shaped molecules as host structures, and an examination of their binding properties with a variety of guests using NMR spectroscopy. </p><p>Several clips with a hydrocarbon or glycoluril backbone were synthesized. The binding of cations to small, hydrocarbon-based clips suggests that binding is enhanced by the rigidity and cooperativity between the two sidewalls of the clip. Binding is also very much dependant on the solvent properties. </p><p>Glycoluril-based clips built with aromatic sidewalls provide a deep cavity for binding guest molecules. The binding properties of these hosts were studied with several guests such as cations, Lewis acids and Lewis bases. Lewis basic binding sites in the acenaphthene-terminated clip were dominating in guest binding. Complexation-induced conformational changes in the wall-to-wall distance were observed for this clip.</p><p>In contrast, for a porphyrin-terminated clip with metal centers, very strong binding to a series of Lewis basic guests of various sizes into the clip cavity was observed. Conformational locking of guests with long alkyl chains was achieved, suggesting that, this clip could be useful as a potential molecular tool for the structural characterization of acyclic molecules with several stereogenic centers. This porphyrin clip was also shown to bind substituted fullerenes in the cavity.</p>
357

Exploring Molecular Interactions : Synthesis and Studies of Clip-Shaped Molecular Hosts

Polavarapu, Anjaneya Prasad January 2007 (has links)
Molecular recognition via noncovalent interactions plays a key role in many biological processes such as antigen-antibody interactions, protein folding, the bonding and catalytic transformation of substrates by enzymes, etc. Amongst these noncovalent interactions, electrostatic interactions, hydrogen bonding, π-π interactions, and metal-to-ligand bonding are the most prominent. Exploring noncovalent interactions in host-guest systems that range from small hydrocarbon systems to more complex systems is the main motivation of this thesis. The present study involves the design, synthesis and characterization of clip-shaped molecules as host structures, and an examination of their binding properties with a variety of guests using NMR spectroscopy. Several clips with a hydrocarbon or glycoluril backbone were synthesized. The binding of cations to small, hydrocarbon-based clips suggests that binding is enhanced by the rigidity and cooperativity between the two sidewalls of the clip. Binding is also very much dependant on the solvent properties. Glycoluril-based clips built with aromatic sidewalls provide a deep cavity for binding guest molecules. The binding properties of these hosts were studied with several guests such as cations, Lewis acids and Lewis bases. Lewis basic binding sites in the acenaphthene-terminated clip were dominating in guest binding. Complexation-induced conformational changes in the wall-to-wall distance were observed for this clip. In contrast, for a porphyrin-terminated clip with metal centers, very strong binding to a series of Lewis basic guests of various sizes into the clip cavity was observed. Conformational locking of guests with long alkyl chains was achieved, suggesting that, this clip could be useful as a potential molecular tool for the structural characterization of acyclic molecules with several stereogenic centers. This porphyrin clip was also shown to bind substituted fullerenes in the cavity.
358

Solid-State Synthesis of Imide Ligands for the Self-Assembly of Metal-Organic Materials

Perman, Jason Alexander 01 January 2011 (has links)
In this research project, reduction or complete elimination of organic solvents is explored in the synthesis of cyclic imides using a technique that brings reagents into favorable position to react. Cocrystal Controlled Solid-State Synthesis (C3Sy3), takes advantage of supramolecular interactions such as hydrogen bonding and π-π stacking to form a cocrystal which can sequential be heated to complete the condensation reaction and produce a desirable product. Twenty-five successful condensation reactions result in high and clean yield. C3Sy3 of cyclic imides with auxiliary hydrogen bonding moieties like carboxylic acid, carboxylate or pyridyl groups are amenable to form additional solid-state materials. These moieties are useful in forming coordinate covalent bonds with metal cations. Using these C3Sy3 synthesized molecules as ligands, various Metal-Organic Materials (MOMs) are self-assembled. These MOMs offer unique qualities owing to the properties of the cyclic imides. With the addition of accessible carbonyl groups, they may participate as hydrogen bond acceptors or hydrophilic groups. Various degrees of rotation of N-phenyl substituents around the imide plane allow for structural flexibility as a route to supramolecular isomers in MOMs. The ease in imide synthesis may allow the fast scale-up of these ligands for industrial application. Similar ligands are generally synthesized by cross-coupling or substitution reactions that require expensive catalyst and various organic solvents. Metal-organic materials are a class of compounds amenable to crystal engineering owing to the directional coordinate covalent bonds between metal or metal clusters and organic ligands. They are characterized by X-ray diffraction, spectroscopy, volumetric and gravimetric analysis. The C3Sy3 imides were used to construct various MOMs, from discrete nanostructures to extended 3-periodic frameworks that possess viable internal space for applications pertaining to porous materials. Structural characterization by single crystal X-ray diffraction and structure-function relations are addressed. Gas sorption experiments show that many of these materials are structurally robust and retain crystallinity after evacuation. Ion exchange and guest uptake experiments using the synthesized materials demonstrate their potential as agents for sequestration. The bottom-up synthesis of metal-organics materials is leading the field of crystal engineering with built-in properties, showing promise by combining attributes from both inorganic and organic components.
359

The uses of supramolecular chemistry in synthetic methodology development

Shabbir, Shagufta Hasnain 24 February 2011 (has links)
Enantioselective indicator displacement assays (eIDAs), was transitioned to a high-throughput screening protocols, for the rapid determination of concentration and enantioselectivity (ee) of chiral diols and α-hydroxycarboxylic acid. To improve the design of our previously established receptor based on o-(N,N-dialkylaminomethyl)arylboronate scaffolds for eIDAs. The rigidity of the receptor, which pertinent from the formation of an intramolecular N-B dative bond was investigated. o-(Pyrrolidinylmethyl)phenylboronic acid its complexes with bifunctional substrates such as catechol, [alpha]-hydroxyisobutyric acid, and hydrobenzoin was studied in detail by x-ray crystallography and ¹¹B NMR. Our structural study predicts that the formation of an N-B dative bond, and/or solvolysis to afford a tetrahedral boronate anion, depends on the solvent and the complexing substrate present. To simplify the operation of eIDAs, we introduced an analytical method, which utilize a dual-chamber quartz cuvette, which reduces the number of spectroscopic measurements from two to one and introduced artificial neural networks (ANNs) which simplifies data analysis. In a second example a high-throughtput screening protocol for hydrobenzoin was developed. The method involves the sequential utilization of what we define herein as screening, training, and analysis plates. Several enantioselective boronic-acid based receptors were screened using 96-well plates, both for their ability to discriminate the enantiomers of hydrobenzoin and to find their optimal pairing with indicators resulting in the largest optical responses. The best receptor/indicator combination was then used to train an ANN to determine concentration and ee. To prove the practicality of the developed protocol, analysis plates were created containing true unknown samples of hydrobenzoin generated by established Sharpless asymmetric dihydroxylation reactions, and the best ligand was correctly identified. The system was extended to pattern recognition for the rapid determination of identity, concentration, and ee of chiral vicinal diols. A diverse enantioselective sensor array was generated with three chiral boronic acid receptors and pH indicators. The optical response produced by the sensor array, was analyzed by two pattern recognition algorithms: principal component analysis (PCA) and ANNs. The PCA plot demonstrated good chemoselective and enantioselective separation of the analytes, and ANNs was used to accurately determine the concentration and ee of five unknown samples. / text
360

Chiralinių supramolekulinių tektonų, turinčių biciklo[3.3.1]nonano fragmentą, sintezė, struktūros ir asociacijos tyrimai / Synthesis, Structural and Association studies of Chiral Supramolecular Tectones Based on Bicyclo[3.3.1]nonane Framework

Bagdžiūnas, Gintautas 27 December 2012 (has links)
Supramolekulinė chemija – tyrimų kryptis, nagrinėjanti struktūras, sudarytas iš riboto ir neriboto skaičiaus molekulių (tektonų), sąveikaujančių tarpusavyje silpnosiomis nekovalentinėmis sąveikomis. Žinoma, kad medžiagų savybės užkoduotos ne tik molekulių struktūroje, bet ir jų tarpusavio išsidėstyme. Savo ruožtu, chirališkumas yra vienas iš faktorių, leidžiančių vienoms molekulėms atpažinti kitas. Pagrindiniai disertacijos tikslai: nustatyti 1) chiralinių, konformaciškai suvaržytų bei labilių junginių, turinčių biciklo[3.3.1]nonano fragmentą, chromoforų prigimties, tarpusavio orientacijos ir atstumo įtaką chiroptinėms savybėms, 2) chiralinių tripakeistų aromatinių, turinčių biciklo[3.3.1]nonano pakaitus, ir kompleksinių paladžiociklinių junginių chirališkumo ir struktūros įtaką formuojant įvairaus lygio tvarkias supramolekulines struktūras. Naudojantis apskritiminio dichroizmo spektroskopijair teoriškai atliktais ab initio skaičiavimais charakterizuotos molekulės, turinčios įvairios elektroninės prigimties chromoforus, bei jose vykstantys elektroniniai šuoliai. Susintetinti tripakeisti aromatiniai junginiai, turintys išorinius biciklo[3.3.1]nonano ir įvairių dydžių aromatinius fragmentus. Ištirta tokių save atpažįstančių chiralinių tripakeistų aromatinių junginių struktūros įtaka supramolekulinei asociacijai tirpale ir ant paviršiaus. Nustatyta, kad susintetinti V formos chiralinis ir raceminis dialkinbiciklo[3.3.1]nonenil- ligandai, turintys koordinuojantį piridino pakaitą... [toliau žr. visą tekstą] / The supramolecular chemistry of assemblies composed of a limited or infinite number of the molecular tectons interacting with each other via noncovalent interactions was investigated with a special emphasize on the chirality of the building blocks. The following objectives were pursued in this work: 1) to determine the electronic structure of both conformationally rigid and labile chiral bicyclo[3.3.1]nonane compounds, the mutual orientation and distance of the chromophores and its impact on chiroptical properties, 2) to study the influence of chirality and structure of palladacycle and trisubstituted compounds, containing external bicyclo[3.3.1]nonanyl- and aromatic fragments of different size on the formation of various supramolecular structures. The chiral bicyclo[3.3.1]nonane compounds with chromophores of different electronic nature were synthesized. The possibilities of exciton interaction and charge transfer phenomena were studied in the obtained molecules. The influence of chirality and structure of trisubstituted compounds containing external bicyclo[3.3.1]nonanyl- and aromatic fragments of different size on supramolecular association in solution and on the surface was investigated. In solution, the trisubstituted compounds exist in the form of nanoparticles with regular supramolecular structure. It was shown that the V-shaped chiral and racemic dialkynbicyclo[3.3.1]nonenyl- ligands having coordinating pyridine moiety, form rhomb-shaped palladacycle. The racemic and... [to full text]

Page generated in 0.0839 seconds