Dissertations / Theses on the topic 'Chirality'

Depuis des dizaines d’années, les chimistes organiciens ont accru leurs capacités à synthétiser des molécules complexes de manière exponentielle par le développement de nouvelles méthodes toujours plus élaborées. Malgré ces accomplissements, le challenge de synthétiser de nouvelles molécules toujours plus complexes de manière sélective et efficace reste toujours d’actualité. Dans le premier chapitre, nous introduirons la notion de chiralité de manière générale. Ensuite, les différentes stratégies pour contrôler la chiralité en synthèse organique seront exposées, en se focalisant plus particulièrement sur l’organocatalyse énantiosélective. Ensuite, dans le deuxième et troisième chapitre, le contrôle de la chiralité centrale sera étudié d’une part dans une synthèse de tetrahydropyranes et d’autre part dans l’addition de Michael impliquant les 1,3-cetoamides α,β-insaturés. Dans le quatrième chapitre, d’autres types de chiralité moins conventionnelles seront examinées. Tout d’abord, une étude portant sur la racemization des furanes atropisomères sera menée. Ensuite, des stratégie innovantes seront mises en œuvre pour la synthèse [4]- et [5] helicènes via notamment des phénomènes de conversion de chiralité
In the last century, the ability of organic chemists to build complex molecules has grown exponentially. Despite these achievements, the challenge of synthesizing new molecules efficiently and selectively remains open. In the first chapter, we will discuss the definition of chirality as a transversal topic in science. Subsequently we will discuss the different strategies to control chirality in organic synthesis, with a special attention to organocatalysis. In the second and third chapter we will focus on the attempt to control central chirality for the synthesis of substituted tetrahydropyrans and the investigation of the reactivity of α,β-unsaturated 1,3-ketoamides in Michael addition. In the fourth chapter, other less conventional types of chirality will be examined. First, a study on the racemization of atropisomer furans will be conducted. Then, innovative strategies will be implemented for the synthesis [4] - and [5] helicenes via, in particular, chirality conversion approaches

Depuis des dizaines d’années, les chimistes organiciens ont accru leurs capacités à synthétiser des molécules complexes de manière exponentielle par le développement de nouvelles méthodes toujours plus élaborées. Malgré ces accomplissements, le challenge de synthétiser de nouvelles molécules toujours plus complexes de manière sélective et efficace reste toujours d’actualité. Dans le premier chapitre, nous introduirons la notion de chiralité de manière générale. Ensuite, les différentes stratégies pour contrôler la chiralité en synthèse organique seront exposées, en se focalisant plus particulièrement sur l’organocatalyse énantiosélective. Ensuite, dans le deuxième et troisième chapitre, le contrôle de la chiralité centrale sera étudié d’une part dans une synthèse de tetrahydropyranes et d’autre part dans l’addition de Michael impliquant les 1,3-cetoamides α,β-insaturés. Dans le quatrième chapitre, d’autres types de chiralité moins conventionnelles seront examinées. Tout d’abord, une étude portant sur la racemization des furanes atropisomères sera menée. Ensuite, des stratégie innovantes seront mises en œuvre pour la synthèse [4]- et [5] helicènes via notamment des phénomènes de conversion de chiralité
In the last century, the ability of organic chemists to build complex molecules has grown exponentially. Despite these achievements, the challenge of synthesizing new molecules efficiently and selectively remains open. In the first chapter, we will discuss the definition of chirality as a transversal topic in science. Subsequently we will discuss the different strategies to control chirality in organic synthesis, with a special attention to organocatalysis. In the second and third chapter we will focus on the attempt to control central chirality for the synthesis of substituted tetrahydropyrans and the investigation of the reactivity of α,β-unsaturated 1,3-ketoamides in Michael addition. In the fourth chapter, other less conventional types of chirality will be examined. First, a study on the racemization of atropisomer furans will be conducted. Then, innovative strategies will be implemented for the synthesis [4] - and [5] helicenes via, in particular, chirality conversion approaches

Electromagnetic metamaterials are artificial media that derive novel properties from periodic structuring on the sub-wavelength scale. Here, the consequences of two-dimensional (2D) and three-dimensional (3D) chirality for the electromagnetic properties of metamaterials are investigated. The focus of this work is on new ways of achieving circular conversion dichroism, optical activity and negative refraction in highly symmetric structures. In the theoretical part of this work, fundamental constraints on polarization effects in planar metamaterials are established based on symmetry and energy conservation considerations. Through the experimental study of 2D chirality, I have first observed circular conversion dichroism (i) in non-chiral structures and (ii) due to 2D-chiral arrangement of non-chiral elements. (iii) I have first seen enantiomerically sensitive reflection, yielding the experimental demonstration that circular conversion dichroism results in simultaneous directional asymmetries in transmission, reflection and absorption. In particular, a tunable transmission asymmetry of up to 21 % has been observed when extrinsic 2D chirality was associated with oblique incidence onto a non-chiral meandering wire pattern. At normal incidence circular conversion dichroism was seen for non-chiral split ring elements assembled into a 2D-chiral double-periodic array. Simultaneous directional and enantiomeric asymmetries in transmission (16 %), reflection (16 %) and absorption (32 %) were observed for normal incidence onto a double-periodic array of 2D-chiral split rings. Regarding 3D chirality, I have (i) realized the first material with a negative refractive index due to chirality and (ii) observed optical activity in the first stereometamaterial. (iii) I have discovered that optical activity can be observed in non-chiral metamaterials and (iv) I have demonstrated that optical activity in such structures is tunable and occurs in transmission and reflection. In particular polarization rotation reaching 81± and circular dichroism of up to 26 dB have been observed for non-chiral arrays of split rings, when an extrinsically 3D-chiral experimental arrangement was formed by metamaterial and direction of incidence. Based on a previously-studied meta-molecule consisting of mutually twisted metal patterns in parallel planes, microwave and photonic stereometamaterials with optical activity have been realized in this thesis and such a structure has been shown to have a negative refractive index of -1.7 for right-handed circularly polarized microwaves.

- Alicyclic diols can hydrogen bond in many different ways and yield most interesting structures. In this thesis, eight C2-symmetric diols 48-50, 78, 79 and 81-83 were synthesized and their crystal structures were determined. No less than seven of these show unusual solid state behaviour: 48 and 78 are inclusion hosts; 49, 50 and 78 form doubly-stranded hydrogen-bonded ladder structures, where there is a strong preference for each strand to be homochiral; 78, 81 and 82 undergo self-resolution during recrystallization; and 83 forms chirally pure crystals (but the material is still racemic). - One of the favourable supramolecular synthons for hydroxy compounds is the (O-H)6 cycle of hydrogen bonds. When this cycle is formed by a racemic compound, its enantiomers alternate down-up-down etc. around the cycle. No case of an (O-H)6 cycle involving chirally pure hydroxy compounds is known. These observations indicate a strong preference for the (O-H)6 cycle being constructed from achiral or racemic molecules rather than from chirally pure hydroxyl compounds. Racemic (??)-48 and (??)-92 which are already known to form (O-H)6 cycles in the solid state were prepared in chirally pure form and their X-ray crystal structures determined. No (O-H)6 cycles were observed for these homochiral diols. These findings confirm that the (O-H)6 motif occurs only for achiral or racemic compounds. - Similarly, the edge-to-edge eight-membered aryl C-H???N dimer involves either achiral molecules or those of opposite chirality. No chirally pure dimers of this type are reported. Racemic compounds 42-44 that are known to pack using the C-H???N dimer were synthesized in chirally pure form. No edge-to-edge eight-membered aryl C-H???N dimers were formed in the solid state. Hence this supramolecular synthon is only favoured for achiral or racemic compounds only. - Other major conclusions are that the cause of self-resolution is due to packing energy. In some cases it is likely that solvent choice, or solvent plus temperature selection, can be used to control self-resolution.

The chirality of biological systems can be probed using highly emissive lanthanide complexes with the aid of circularly polarised luminescence and emission spectroscopy. Such chirality probes can be synthesised through the incorporation of a remote chiral centre within the ligand framework, which can preferentially stabilise a particular stereoisomer giving an enantiopure complex of well-defined helicity. Alternatively, lanthanide chirality probes can be derived from achiral or dynamically racemic ligands, where the selective induction of a CPL signal can be monitored as a function of the nature and concentration of a selected chiral analyte. A series of chiral lanthanide complexes has been synthesised. Each complex is based on an amide substituted 1,4,7-triazacyclononane system derived from either R-(+) or S-(-)-α-methylbenzyl amine. The stereochemistry of the amide moiety controls the helicity of the complex, and one major diastereoisomer is formed for each lanthanide metal. The absolute stereochemistry of the major diastereoisomer was determined by X-ray crystallography (S-Δ-λλλ and R-Λ-δδδ). Inclusion of an aryl-alkynyl chromophore generated complexes that exhibited large extinction coefficients (up to 55,000 M-1 cm-1) and high quantum yields (up to 37%) in water. A second set of bright Eu (III) complexes has been prepared based on an achiral heptadentate ligand system, which vary in the nature of the pyridyl donor (phosphinate, carboxylate and amide). The binding of a number of chiral acids including lactate, mandelate and cyclohexylhydroxyacetate was monitored by a change in the emission spectrum and the induction of strong CPL. Empirical analysis of the ΔJ = 4 region of each of the Eu (III) complexes allows an assignment of the complex-anion adducts as R-Δ and S-Λ. Furthermore, variations in the sign and magnitude of CPL allow the enantiomeric purity of samples with unknown enantiomeric composition to be assessed. Finally, several dynamically racemic lanthanide chirality probes have been synthesised and characterised. Induced CPL has been assessed, which arises as a result of the change in complex constitution upon binding to important chiral biomolecules such as, sialic acid, O-phosphono-amino acids and peptides and oleoyl-L-lysophosphatidic acid (LPA). This work presents the first example of induced CPL in the detection of cancer biomarkers, sialic acid and LPA, and demonstrates the utility of this class of dynamically racemic Eu (III) complexes as chirality probes.

En esta tesis ha estudiado la influencia de la geometría de las moléculas en las monocapas de autoensamblaje (SAM) de ácidos quirales, se ha presentado la síntesis de la familia de anfifílicos quirales. Cada compuesto se ha medido con STM en la interfaz grafito-1-phenyloctanano como un único enantiómero y como una mezcla racémica para comprobar la transferencia de quiralidad de molécula a SAM a dos dimensiones. Se ha encontrado que las moléculas con geometría curvada - 1,3Ph y 2,7Naph, forman dominios muy regulares en el caso de enantiómero puro y conglomerado en el caso de la mezcla racémica. Los otros compuestos forman diversos polimorfos (hasta cuatro en el caso de 1,5Naph) o cristales 2D irregulares (2,6Naph), y cuando se ha estudiado la mezcla racémica, se han encontrado las SAM desordenadas o un pseudoracemato para 4,4'Biph. Las mezclas de los derivados de naftaleno se han estudiado en la interfaz grafito-1-phenyloctano para comprobar si los compuestos son capaces de formar monocapas mixtas, por otra parte las mismas mezclas se han medido con calorimetría de barrido diferencial (DSC) y difracción de rayos X (DRX) para comparar el comportamiento en los sistemas de dos y tres dimensiones. Se ha descubierto que los ácidos forman monocapas mixtas estables, y en un caso se ha observado un comportamiento de solución sólida. El reconocimiento quiral entre los ácidos anfifílicos se ha comprobado con un amina quiral modelo trans-1,2-diaminociclohexano (DACH) - para descubrir que, en caso del ácido 1,3Ph y 2,7Naph, hay un reconocimiento quiral y la formación diastereoselectiva de un complejo en la interfaz de grafito-1-phenyloctane. En el caso del ácido 2,7Naph and DACH también se ha observado la formación de multicapas. Se ha utilizado el modelado molecular para obtener mejor idea de las fuerzas y el ensamblaje de las moléculas. El ácido 1,3Ph fue elegido para estudiar su capacidad de reconocimento con diversas aminas quirales y aquirales incluyendo compuestos utilizados como medicamentos: Metoprolol, Antenolol y Verpamil. Se ha encontrado, en el caso de Metoprolol que hay una complejación preferencial de uno de los enantiómeros en la interfaz grafito-1-phenyloctano. Se han usado mezclas de ácidos para comprobar su capacidad para actuar como un agente de resolución en dos sistemas dimensionales, pero no se ha encontrado una evidencia clara de mejoras con respecto a los enatiomeros puros, debido a la adsorción competitiva. Además se ha llevado a cabo la serie de experimentos de mezclas en masa de ácido 1,3Ph y DACH para comprobar si había un reconocimiento quiral en sistemas tres dimensionales. Las muestras se han comprobado con DSC, XRD y en microscopio óptico polarizado (POM) en un rango de temperaturas para descubrir el comportamiento de fase y el ensamblaje de las moléculas. La quiralidad del compuesto juega un papel determinante en el comportamiento de fase de los materiales.
In this thesis study of influence of geometry of the molecules on self-assembly monolayers (SAM) of chiral acids was studied, the synthesis of family of chiral amphiphiles was presented. Each compound was measured with STM at the graphite-1-phenyloctane interface as a single enatiomer and as a racemic mixture to check the transfer of chirality from molecule to two dimensional SAM. It was found that the bent-core molecules – 1,3Ph and 2,7Naph form very regular domains in the case of pure enatiomer and conglomerate in the case of racemic mixture. The other compounds form various polymorphs (up to four in the case of 1,5Naph) or irregular 2D crystals (2,6Naph), and when the racemic mixture was studied, the SAM was disordered or a pseudoracemate was found for 4,4´Biph. The mixtures of the naphthalene derivatives were studied at the graphite-1-phenyloctane interface to check if compounds are capable of forming mixed monolayers, moreover the same mixtures were measured with differential scanning calorimetry (DSC) and X-ray diffraction (XRD) to compare behaviour in two and three dimensional systems. It was discovered that the acids form stable mixed monolayers, and in one case a solid solution behaviour was observed. The chiral recognition between amphiphilic acids was checked with a model chiral amine -1,2 trans-diaminocyclohexane (DACH) - to discover that in case of acid 1,3Ph and 2,7Naph there is a chiral recognition and diastereselective formation of a complex at the graphite-1-phenyloctane interface. In the case of acid 2,7Naph and DACH also formation of multilayers was observed. The molecular modelling was used to get insight into the forces and packing of the molecules. The acid 1,3Ph was chosen to study its capability of binding various chiral and achiral amines including compounds used as medicaments: Metoprolol, Antenolol and Verpamil. It was found in the case of Metoprolol that there is preferential binding of one of the enantiomers at the graphite-1-phenyloctane interface. Also mixtures of acids was checked for their capability to act as a resolving agent in two dimensional systems, but no clear evidence of improvements over the pure were observed because of competitive adsorption. Also the series of experiments of bulk mixtures of acid 1,3Ph and DACH was performed to check if there is a chiral recognition in three dimensional systems. The samples were checked with DSC, XRD and in polarized optical microscope (POM) in a range of temperatures to discover the phase behaviour and packing of molecules. The chirality of the component plays a determining role in the phase behaviour of the materials.

Les microcavités en semiconducteurs, définis par une cavité Fabry Pérot planaire contenant un puits quantique, permettent de confiner fortement à la fois la lumière et les excitations électroniques. Dans ces hétérostructures, la lumière et la matière interagissent si fortement que les excitations fondamentales du système sont décrites par des quasi-particules hybrides lumière-matière appelées polaritons excitoniques. Les polaritons héritent les propriétés de leurs deux constituants élémentaires : la partie photonique peut être structurée spatialement en sculptant à l’échelle micrométrique l’indice de réfraction du matériau par lithographie et gravure ; la composante excitonique donne au système une très forte non-linéarité Kerr. Dans cette thèse, nous avons utilisé ces deux propriétés pour réaliser une ingénierie du mode photonique grâce à des micropiliers couplés, et sonder plusieurs facettes de leurs propriétés non-linéaires. Dans une première partie du travail, nous étudions des microcavités couplées disposées en anneau. Tirant profit d’un couplage spin-orbite synthétique et de la possibilité de polariser en spin le gain optique, nous avons démontré une émission laser dans des modes présentant un moment orbital angulaire (OAM) fini, dont la chiralité peut être contrôlée optiquement. De plus, nous mettons en évidence un comportement bistable original du microlaser, qui implique des modes présentant des valeurs différentes du OAM ainsi que des textures de polarisation différentes. Dans la deuxième partie de la thèse, nous explorons la dynamique non-linéaire du système sous pompage cohérent. Nous déclenchons une instabilité paramétrique dans des résonateurs couplés, et analysons en détails le mécanisme physique sous-jacent. Dans le régime instable, nous observons l’établissement d’oscillations paramétriques qui donnent lieu à des bandes latérales très brillantes et contrastées dans le spectre d’émission. Enfin dans la dernière partie du travail, nous étudions un régime de métastabilité optique dans un résonateur fortement non-linéaire. Ce régime se manifeste par l’apparition de sauts aléatoires entre deux valeurs du nombre moyen de photons dans le résonateur. Pour certaines conditions de pompage, nous observons un ralentissement critique de la dynamique métastable, signature d’une transition de phase dissipative. Par des expériences d’hystérésis dynamique, nous évaluons les exposants critiques de cette transition de phase. Finalement, nous proposons une correspondance (“mapping”) entre la dynamique métastable d’un résonateur Kerr, et les renversements aléatoires dans le temps d’un bit logique. Nous pouvons alors définir et mesurer la production d’entropie lors d’une trajectoire unique d’une expérience d’hystérésis dynamique. Ces mesures nous ont permis de valider, dans le cadre de cette correspondance, le théorème intégral de fluctuations pour la production d’entropie hors équilibre. Ce travail couvre une grande variété de sujets, d’aspects les plus fondamentaux de la dynamique non linéaire dans un système photonique, à des idées innovantes pour réaliser des dispositifs photoniques, qui pourraient dans le futur être optimisés pour un fonctionnement à température ambiante
Semiconductor microcavities, defined by a planar Fabry-Perot cavity embedding a quantum well, allow tightly confining both optical and electronic excitations. In these heterostructures, light and matter interact so rapidly that the fundamental excitations of the system can be effectively described as hybrid light-matter quasiparticles, called exciton-polaritons. Polaritons inherit properties from both their elementary constituents: the photonic modes can be tailored by molding the refractive index landscape via dry etching processing, while the excitonic component endows the system with a large Kerr nonlinearity. In this thesis, we take advantage of these two key features to engineer the photon modes using coupled micropillar resonators, and probe diverse non-linear phenomena. In the first part of this work, we consider coupled microcavities arranged in a ring geometry. Harnessing an analogue spin-orbit coupling and the ability to spin-polarize the optical gain, we demonstrate lasing in modes carrying a net orbital angular momentum (OAM), with a chirality which can be optically controlled. In addition, we evidence a bistable behaviour of the microlaser, involving modes presenting distinct OAM values and polarization patterns. In the second part of the thesis, we concentrate on the nonlinear dynamics of the system under resonant pumping. We trigger a parametric instability in coupled nonlinear resonator, and investigate the underlying mechanism. In the unstable regime, we observe the onset of sustained parametric oscillations, which presence is revealed by the appearance of bright and contrasted sidebands in the emission spectrum. In the last part of the thesis, we investigate the optical metastability a highly nonlinear single micropillar cavity, which manifests in stochastic jumps of the cavity occupation between the two -otherwise stable- branches of the classical bistability. For specific driving conditions, we observe a critical slowing down of the metastable dynamics, which is associated to the onset of a dissipative phase transition. Using a scaling analysis involving dynamical hysteresis experiments, we retrieve the critical exponents of the phase transition. Finally, we propose a mapping of the metastable dynamics of a Kerr resonator onto a logical bit subject to random bit-flip events. We can define and measure the entropy production at a single trajectory level during dynamical hysteresis experiments. These measurements allow validating an integral fluctuation theorem for the non-equilibrium entropy production. This work covers a variety of topics, from fundamental non-linear dynamics in a photonic system, to novel ideas for realizing optical devices, which could eventually operate at room temperature

Le mode d’excitation collective exotique appelé chiralité a été étudié et des isomères de longue durée de vie ont été recherchés dans les noyaux ¹³⁶Nd et ¹³⁵Nd. Cinq paires de bandes Δ I=1 presque dégénérées et de même parité ont été identifiées à des spins élevés dans ¹³⁶Nd Les bandes observées ont été étudiées en utilisant la théorie de la fonctionnelle de densité covariante contrainte et rotation autour d'une axe incliné, et par un nouveau modèle de rotor plus particules développé pour décrire le couplage de particules dans quatre couches j à un rotor triaxial. Les propriétés de ces bandes doublet sont en bon accord avec les résultats des calculs théoriques. Par conséquent, l'existence de bandes chirales multiples (MχD) dans le noyau ¹³⁶Nd a été établie. Il s'agit de la première preuve expérimentale de l'existence de bandes chirales dans des noyaux pairs. Les cinq paires de bandes chirales constituent le plus grand ensablé de bandes chirales observé jusqu'à présent dans un seul noyau. De plus, le schéma de niveaux de ¹³⁶Nd a été considérablement étendu aux spins bas, moyens et très élevés. Les configurations possibles de toutes les bandes rotationnelles ont été attribuées á l'aide du modèle Nilsson-Strutinsky en rotation. La structure de ¹³⁶Nd a été clarifiée et les divers types d'excitations uni-particule et collectives ont été bien compris. Une nouvelle paire de bandes chirales á parité positive a été identifiée dans. Les caractéristiques des bandes soutiennent leur interprétation en termes de bandes chirales. Des bandes chirales à parité négative ayant été identifiées précédemment, la présence de multiple bandes chirales dans ¹³⁵Nd est ainsi établie. Les bandes chirales observées ont été étudiées en utilisant la théorie avec fonctionnelle de densité covariante contrainte et avec le modèle rotor plus particules; elles reproduisent fidèlement les données expérimentales, confirmant ainsi le phénomène MχD dans ce noyau. Les bandes chirales nouvellement observées dans ¹³⁵Nd représentent une étape importante dans la confirmation de l'existence du phénomène MχD dans les noyaux. La recherche d'états isométriques à longue durée de vie dans ¹³⁵Nd et ¹³⁶Nd a été aussi effectuée, mais n'a pas permis d'identifier de nouveaux isomères. Cependant, nous avons pu confirmer la présence des isomères déjà identifiés dans les noyaux ¹³⁸Nd, ¹³⁴Ce, ¹³⁶Pr, et ¹³⁷Pr dans nos données
The exotic collective excitation mode called chirality has been investigated and long-lived isomers have been searched for in the ¹³⁶Nd and ¹³⁵Nd nuclei. Five pairs of nearly degenerate Δ I=1 bands with the same parity have been identified at high spins in ¹³⁶Nd. The observed bands were investigated by the constrained and tilted axis cranking covariant density functional theory and a new developed four single-j shells particle-rotor model. It was found that the properties of these doublet bands are in good agreement with results of the model calculations. Therefore, the multiple chiral doublets (MχD) phenomenon in the nucleus ¹³⁶Nd was confirmed. This was the first experimental evidence for the MχD bands in even-even nuclei. The five pairs of chiral doublet bands is the largest observed in a single nucleus until now. In addition, the level scheme of the ¹³⁶Nd has been extended significantly at low, medium, and very high spins. Possible configurations of all rotational bands have been assigned by using the cranked Nilsson-Strutinsky model. The band structure of ¹³⁶Nd was clarified and the various types of single-particle and collective excitations were well understood. A new pair of positive-parity chiral doublet bands has been identified in ¹³⁵Nd. The characteristics of the doublet bands support the chiral interpretation. Together with the previously reported negative-parity chiral doublet bands show the presence of MχD bands in ¹³⁵Nd. The observed doublet bands were compared with constrained covariant density functional theory and particle-rotor model calculations which nicely reproduce the experimental data, confirming the MχD phenomenon in this nucleus. The newly observed MχD bands in ¹³⁵Nd represent an important milestone in supporting the existence of MχD in nuclei. The search for long-lived isomeric states in ¹³⁵Nd and ¹³⁶Nd has also been performed. This did not lead to the identification of new isomers, but we could confirm the existence of the previously reported isomers in the nuclei ¹³⁸Nd, ¹³⁴Ce, ¹³⁶Pr, and ¹³⁷Pr in our data

Thesis (Ph. D.)--University of Adelaide, Dept. of Clinical and Experimental Pharmacology, 1993?
Copies of author's previously published articles in back-cover pocket. Includes bibliographical references (leaves 180-205).

Sur la base des travaux antérieurs du laboratoire, nous avons développé une nouvelle approche synthétique énantiosélective, en deux étapes, pour l’accès à des glutarimides fonctionnalisés à partir de cyclobutanones facilement accessibles, selon deux directions: une stratégie impliquant une extension de cycle à deux atomes et une stratégie basée sur une contraction de cycle à deux atomes. En parallèle, nous avons démontré que les arynes porteurs de la chiralité axiale en position ortho de la triple liaison réactive peuvent être générés à partir des précurseurs iodo/triflate de type Suzuki et réagissent in situ avec divers substrats. Leur stabilité configurationnelle et leur grande réactivité nous ont permis de proposer une nouvelle méthode de synthèse pour introduire un fragment biaryle à chiralité axiale au sein de pratiquement toutes molécules organiques réactives vis-à-vis des arynes
Based on the previous work in our laboratory, we have developed a new enantioselective two-step synthetic approach to access functionalized glutarimide derivatives using readily available cyclobutanones following two directions: a two-atom ring expansion strategy and a two-atom ring contraction strategy. Meanwhile, we have demonstrated that arynes bearing axial chirality ortho to their reactive triple bond can be generated from the corresponding iodo/triflate Suzuki-type precursors and trapped in situ by various substrates. Their configurational stability and high reactivity allow us to propose a new synthetic method for the facile introduction of an axially chiral biaryl unit onto virtually any organic molecule reacting with arynes

When chiral molecules are added to an achiral nematic liquid crystalline solvent, they can transmit their molecular chirality to the whole system over distances many times their molecular length. The helical twisting power, βm, is a measure of the degree of twist a chiral molecule can induce in a nematic liquid crystal. The work in this thesis is primarily concerned with calculating helical twisting powers for a variety of chiral molecules using computational and theoretical methods. The first technique used to calculate βm employed Monte Carlo simulations of an atomistic chiral dopant molecule in a chiral liquid crystal phase composed of generic liquid crystalline molecules. The method was found to be computationally expensive, but provided reasonable predictions of when compared with experimental results. Prior to these calculations, a liquid crystal solvent for use in this method was studied. Computer simulations of L/D = 4 soft repulsive spherocylinder (SRS) molecules were performed and two liquid crystalline phases were found in the SRS phase diagram. The scaled chiral index and the chirality order parameter are quantitative measures of molecular chirality. Both of these methods have been found to show a good correlation with experimentally determined helical twisting powers of relatively rigidchiral molecules. The chiral measures have also been incorporated in Monte Carlo simulations of flexible chiral molecules. This method has been successful in predicting βm for flexible chiral dopants, in predicting the temperature dependence of βm, has demonstrated a temperature induced helical twist inversion, and has been used in a predictive study to aid in future synthetic strategies. The final part of the thesis uses Monte Carlo simulations of a chiral molecule in an achiral liquid crystal phase. These simulations have shown that it is possible to relate the torque the chiral molecule induces in the solvent to βm.

An important group of inherited metabolic disorders in man produce abnormal excretion of organic acids in the urine. Diagnosis is usually based on identification of the abnormal metabolites, working back from there to characterise the defect at enzymatic level. The chirality of these metabolites may be significant in that the different enantiomers of a substance usually have different metabolic origins. Thus, knowledge of the chirality of a metabolite aids in the understanding of the mechanism of the disorder. The chirality of a number of urinary metabolites in inherited metabolic disease was examined using gas chromatography-mass spectrometry, most of the analyses being performed using single ion monitoring. This analytical method requires the use of chiral reference compounds of known configuration. Chiral lactic and glyceric acids are available commercially, but a range of chiral beta-hydroxy acids were prepared by the reduction of the corresponding beta-ketocarboxylic acid esters with fermenting baker's yeast. After hydrolysis of the esters, separation of the enantiomers is based on their reaction with a suitable chiral reagent to form a volatile mixture of the diastereoisomers which are resolved by gas-liquid chromatography using a capillary column with a non-chiral stationary phase. Information from the analysis of the chiral standards was used to assign the absolute configuration of the following urinary metabolites; lactic acid in an unusual case of lactic aciduria, glyceric acid in the glyceric acidurias, beta-hydroxybutyrate in ketonuria, beta-hydroxyvalerate in propionic acidaemia, 2-methyl beta-hydroxybutyrate in beta-ketothiolase deficiency and beta-hydroxyadipic acid in hydroxydicarboxylic aciduria. The biochemical significance of the chirality of each of these metabolites is discussed. The assigning of configuration to urinary beta-hydroxyvalerate in propionic acidaemia, 2-methyl beta-hydroxybutyrate in beta-ketothiolase deficiency and beta-hydroxyadipic acid in hydroxydicarboxylic aciduria represents original work and has helped to elucidate the metabolic origins of these compounds.

Pendant ma thèse je me suis intéressé aux signatures de la chiralité dans les systèmes mésoscopiques. Cela m'a conduit à étudier les propriétés de symétrie en champ magnétique du transport non linéaire. J'ai montré que même dans des dispositifs électroniques à deux contacts les propriétés de symétrie sont très riches avec la possibilité d'observer des coefficients transport nonlineaire antisymétrique en champ magnétique. Néanmoins ces propriétés de symétrie ne sont pas déterminées par la chiralité seule. Pour cette raison j'ai proposé d'utiliser le photo-magnétisme comme une sonde sensible à la chiralité, j'ai donc conçu une expérience pour détecter dans des billards mésoscopiques à l'aide de magnétomètres à effet Hall. Cette expérience a mis en évidence des effets dynamiques subtils dans les sondes de Hall balistiques sous irradiation et ont inspiré une recherche théorique et expérimentale sur les états de résistance nulle dans ces systèmes. J'ai aussi cherché des signatures de la chiralité dans le transport à travers des molécules uniques chirales. Ceci m'a conduit à mettre au point des expériences difficiles pour sonder le transport dans des molécules d'ADN qui ont permis de montrer que les proprietés de transport électrique à travers ces molécules peuvent être grandement améliorées lorsqu'elles sont en contact avec un réseau de nanoparticules déconnectées électriquement. Enfin j'ai développé une technique de mesure de photo-transport sans contact adaptée pour sonder un faible nombre de molécules. Cette expérience peut être sensible à la chiralité si une lumière polarisée circulairement est utilisée comme excitation
During my thesis I investigated the signatures of chiraIity in the electrical transport of mesoscopic systems. This led me to study the magnetic field symmetry of nonlinear transport. I showed that even for two terminal devices, nonlinear transport has rich magnetic field symmetry properties, with possible completely antisymmetric behavior. However the symmetry properties are not determined by chirality alone. For this reason I proposed photo-magnetism as a more selective probe for chirality and started a new experiment to detect this effect in quantum dots using a Hall magnetometer. This research exhibited subtle dynamical effects of transport in ballistic Hall bars under irradiation and inspired later research on zero resistance states. I also looked for signatures of chirality in the transport properties of single chiral molecules. This led me to realize technically challenging experiments on transport through DNA, showing that conduction in DNA could be enhanced by connecting the molecules to a disconnected array of nanoparticles. Finally I developed a contact-Iess experiment to probe photo-transport in nanowires under visible illumination. This experiment can also probe chirality by detecting photo-transport under circularly-polarized Iight

The diploma thesis is concerned with switching of vortex circulation in magnetic nanodisks. The results of micromagnetic simulations of hysteresis loops of individual disks with different degrees of asymmetry are presented. The influence of geometric asymmetry of the disk on the shape of the hysteresis loop is discussed as well as switching of vortex circulation in asymmetric nanodisks by external in-plane magnetic field. Simulations of pairs of magnetostatically coupled nanodisks were carried out for different interdisk distances and degrees of asymmetry. By analysing the results of the simulations, the effects of magnetostatic coupling and the asymmetry on resultant circulation of individual vortices were compared and the range of magnetostatic interaction between nanodisks of given dimensions and asymmetry was estimated. Experimental techniques used for fabrication and measurement of the samples are briefly summarized.

Memory of chirality (MOC) is an emerging strategy in asymmetric synthesis. It has been applied to enolate chemistry, reactions involving carbocation intermediates, and to radical systems. In this strategy the chirality of an enantiopure reactant is transferred to the dynamic chirality of a reactive intermediate to produce stereospecific product. 1,4-Benzodiazepin-2-ones have been described as a â privilegedâ structure in medicinal chemistry. In addition to their uses as anxiolytics (Valium ®) and anti-epileptic agents (Clonopin ®), they have shown activity as HIV Tat antagonist, ras farnesyltransferase inhibitors in cancer cells, and antiarrhythmic agents. Because of the utility of this scaffold in the area of medicinal chemistry, it has served as a template in libraries for tens of thousands of compounds. Despite the vast diversity of 1,4-benzodiazepin-2-ones, there are few routes to enantiomerically enriched 3,3-disubstituted benzodiazepines containing a â quaternaryâ stereogenic center. This research will discuss the stereochemical properties of 1,4-benzodiazepin-2-ones, and provide a novel approach to synthesize enantiomerically enriched â quaternaryâ benzodiazepines with stereogenic centers through MOC, without the use of external chiral sources.
Ph. D.

Au cours de ce travail de doctorat, nous avons d'abord étudié un aspect fondamental de la chiralité au niveau moléculaire visant à observer des différences d'énergie entre deux énantiomères provenant d'effets de violation de la parité (PV). Nous avons en particulier examiné les complexes oxorhénium chiraux dont les deux énantiomères présentent théoriquement des énergies d'absorption infrarouge différentes. Leur propriétés chiroptiques, en particulier leur dichroïsme circulaire vibrationnel (VCD), ont été examinées. D'autres complexes métalliques chiraux comme des complexes de platine portant un carbone asymétrique fluoré ont été préparés. Par ailleurs, nous avons étudié la chiralité hélicoïdale provenant de la fusion en ortho de plusieurs cycles aromatiques. Ainsi, des hélicènes portant des fonctionnalités bi-pyridines ont été synthétisés et ont montré des propriétés photophysiques et chiroptiques intéressantes. La présence d'unité chélatantes de type N^N’ ou N-C nous a permis d'étudier l'influence de la coordination de divers métaux de transition (Re(I) et Pt(II)) sur les propriétés et de concevoir de nouveaux commutateurs chiroptiques acido-basiques
In this PhD work, we first investigated a fundamental aspect of chirality at the molecular level aiming to determine the parity violation (PV) energy difference between two enantiomers. We focused on chiral oxorhenium complexes for which the two corresponding enantiomers show theoretically different infrared absorption energies. Their chiroptical properties and especially their vibrational circular dichroism (VCD) were examined. Other chiral metal complexes such as platinum complexes bearing an asymmetric fluorinated carbon have also been prepared. Furthermore, we have investigated the helical chirality derived from the skew shape of ortho-fused aromatic ring. Indeed, helicenes bearing 2,2’-bipyridine functionalities were synthesized and they showed interesting photophysical and chiroptical properties. The presence of N^N’ or N-C chelating moieties enabled us to study the coordination effect of different transition metals (Re(I) and Pt(II)) on their properties and to conceive new acid-base triggered chiroptical switches

2014 - 2015
In 2010, the Prof. Neri’s group showed that the calix[6]arene hosts were able to recognize dialkylammonium axles when they were coupled with the weakly coordinating Tetrakis[3,5 bis(triFluoromethyl)Phenyl]Borate (TFPB−) “superweak anion” that gives very loose ion-pairs with dialkylammonium cations in solution.1 These interpenetrated structures have been defined in supramolecular chemistry as pseudorotaxane and can be considered as synthetic precursors of catenane and rotaxane architectures2 which have showed appealing properties as molecular machines3. Interestingly, the threading of directional alkylbenzylammonium guests with calix[6]arene wheels, led to the stereopreference for the endo-alkyl complexation over the endo-benzyl one and this observed stereo-selectivity brought to the definition of the so called “endo-alkyl rule”4. On these basis we have studied the recognition abilities of calix[6]arene derivatives toward alkylbenzylammonium guests bearing aliphatic chains with different shape and length. In particular, we studied the validity of the endo-alkyl rule with alkylbenzylammonium axles bearing alkyl chains with different lengths and using guests bearing branched alkyl chains. Then the thesis work has been extended to the threading of chiral systems. Special attention was paid to the possibility of obtaining, after threading, the chiral recognition of chiral alkylbenzylammonium ions using chiral calix[6]arene derivatives. The investigation techniques chosen for this purpose have been NMR spectroscopy and Mass Spectrometry by means of the "Enantiomer Labelled Method". Finally the search for new and attractive potential chiral hosts resulted in the application of the "p-bromodienone route" for the first time on calix[6]arene derivatives5 and the study of the optical and electronic properties of inherently chiral resorcin[4]arene derivatives. [edited by author]
XIV n.s.

Hierarchical self-assembly is a process in which molecular building blocks form intermediate structures that self organise at macroscopic level. Remarkable examples can be found in nature, like, for instance, DNAs or viruses. Self-assembly offers interesting strategies to build new complex materials: Therefore, it is very important to understand its mechanism to design and control molecular architectures and to build structures with desired properties and morphologies. A major question is how the shape of the building blocks influences self- assembly. In this context, chirality plays a crucial role: It is extremely sensitive to subtleties on the molecular scale and can guide self-assembly; furthermore, chirality can act as an amplifier of changes that occur at the molecular level. From the theoretical point of view, the difficulty derives from the need of multiscale methods and models, able to connect the different length scales. To take into account the relationship among the building blocks, their supramolecular organization, and the properties of the aggregates, a detailed representation of intermolecular interactions is needed: This description has to be integrated into a suitable modeling of the system behaviour on a much longer length scale. This thesis deals with the development and implementation of models for chirality propagation from the molecular to the meso- and macroscopic levels in self-assembling systems. In particular, the research has been carried out along three lines. The first deals with self-assembly of hard helices, leading to the formation of anisotropic phases of vari- ous symmetry. The second topic is the linear aggregation and formation of liquid crystal phases by double-stranded nucleic acid oligomers (dsNA): The relationship between the sequence of oligonucleotides, their self-assembly and the properties of their cholesteric phase is investigated. The last topic is the aggregation of porphyrin-polypeptide conjugates in water. Depending on the problem and the length scale, we used different theoretical and com- putational methods, in particular: Statistical theories of liquids and molecular dynamics simulations (both atomistic and coarse-grained). The first and third topics have been carried out in collaboration with experimentalists, while for the second other groups of theoreticians have been involved. This thesis is organized in three parts. In Chapter 1, the concepts of self-assembling, chi- rality propagation and multiscale modeling are introduced. Moreover this Chapter presents an outline of the main properties of liquid crystals. The first Part, from Chapter 2 to Chapter 4, presents the study on the anisotropic phases formed by hard helices. Chapter 2 presents a study of the nematic phase, using an Onsager- like theory. The theoretical results are compared with Monte Carlo simulations. In Chapter 3, a theoretical model for the cholesteric phase is presented and used to investigate the relationship between the helical shape and the properties of the cholesteric phase. In Chapter 4, the complete phase diagram of hard helices is presented, together with the characterization of a novel chiral nematic phase. The second Part deals with liquid crystal phases formed by dsNA. Chapter 5 focuses on the relation between the sequence of oligonucleotides and their organization in the cholesteric phase, using a molecular theory and coarse-grained modelling based on sequence dependent structural data. Chapter 6 describes the theoretical model for the cholesteric phase formed by self-assembling oligomers, which integrates the theory for cholesteric order presented in Chapter 3 with that for linear aggregation in the nematic phase. The last Part, from Chapter 7 to Chapter 9, deals with the aggregation of porphyrin- peptide conjugates in water. In Chapter 7 the main concepts of circular dichroism are introduced and the state-of-the-art of self-assembly of porphyrins is reviewed. Chapter 8 describes atomistic molecular dynamics simulation of aggregates of porphyrin-peptide conjugates. Chapter 9 presents a study of the same systems by coarse-grained molecular dynamics simulations, using the MARTINI model. Finally, Chapter 10 presents a summary, which highlights the relevant results obtained in this Thesis, and three Appendices follow.
L’autoassemblaggio gerarchico è un processo nel quale "building block" molecolari formano strutture intermedie che si auto-organizzano a livello macroscopico. Molti esempi possono essere trovati in natura, come il DNA o i virus. L’autoassemblaggio offre interessanti strategie per costruire nuovi materiali complessi: di conseguenza, risulta molto importante capirne i meccanismi per disegnare e controllare le architetture molecolari e per costruire strutture con proprietà e morfologie desiderate. Uno dei principali quesiti cui dare risposta è come la forma del building block influenzi l’autoassemblaggio. In questo contesto, la chiarità svolge un ruolo cruciale: è estremamente sensibile ai dettagli molecolari e può guidare l’autoassemblaggio; inoltre, essa può amplificare le differenze che avvengono su scala molecolare. Dal punto di vista teorico, la difficoltà deriva dalla necessità di metodi e modelli mul- tiscala, capaci di connettere le differenti scale di lunghezza. Per tenere in considerazione la relazione tra i building blocks, la loro organizzazione supramolecolare e le proprietà degli aggregati, si rende necessaria una rappresentazione dettagliata delle interazioni inter- molecolari: questa descrizione deve poi essere integrata in una modellizazione opportuna del comportamento del sistema su scale di lunghezza più grandi. Il tema di questa tesi è lo sviluppo e l’implementazione di modelli per la propagazione di chiralità dalla scala molecolare alla scala meso e macroscopica in sistemi autoassem- blati. Tre diverse linee di ricerca sono state portate avanti. La prima si è concentrata sull’autoassemblaggio di eliche dure, ed in particolare sulla formazione di fasi anisotrope di diversa simmetria. Il secondo argomento riguarda l’aggregazione lineare e la formazione di fasi liquido-cristalline a partire da oligomeri di acidi nucleici a doppio filamento prendendo in considerazione le relazioni tra la sequenza di oligonucleotidi, l’autoassemblaggio e le proprietà della loro fase colesterica. L’ultimo argomento è dedicato all’autoassemblaggio di coniugati porfirina-peptide in acqua. In base al problema e alla scala di lunghezza, sono stati utilizzati diversi metodi teorici e computazionali, in particolare: teorie statistiche dei liquidi e simulazioni di dinamica molecolare (sia atomistica che a grana grossa). La prima e la terza linea di ricerca sono stati condotte in collaborazione con sperimentali, mentre la seconda ha coinvolto altri gruppi teorici. La tesi è organizzata in tre parti. Nel Capitolo 1, il processo di autoassemblaggio, la propagazione di chiralità e il concetto di modellizzazione multiscala vengono descritti. Inoltre in questo Capitolo si presentano le principali proprietà dei cristalli liquidi. Nella prima Parte, dal Capitolo 2 al Capitolo 4, viene presentato il lavoro svolto sulle fasi anisotrope di eliche dure. Il Capitolo 2 presenta lo studio della fase nematica usando una teoria Onsager-like. I risultati teorici sono confrontati con simulazioni Monte Carlo. Nel Capitolo 3, viene presentato un modello teorico per la fase colesterica utilizzato poi per studiare l’effetto della forma elicoidale sulle proprietà della fase colesterica. Nel Capitolo 4 viene presentato l’intero diagramma di fase delle eliche dure, assieme alla caratterizzazione di una nuova fase nematica chirale. La seconda Parte concerne le fasi liquido-cristalline formate da dsNA. Il Capitolo 5 si focalizza sulla relazione tra la sequenza di oligonucleotidi e la loro organizzazione nella fase colesterica utilizzando una teoria molecolare e la modellizzazione a grana grossa, basata su dati strutturali dipendenti dalla sequenza. Nel Capitolo 6, viene descritto il modello teorico per la fase colesterica formata da oligomeri autoassemblati, che mette assieme la teoria per l’ordine colesterico presentata nel Capitolo 3 con quella dell’aggregazione lineare in fase nematica. L’ultima Parte, dal Capitolo 7 al Capitolo 9, si concentra sull’aggregazione di coniugati porfirina-peptide in acqua. Nel Capitolo 7, vengono introdotti i principali concetti relativi al dicroismo circolare e viene commentato lo stato dell’arte dell’autoassemblaggio di porfirine. Il Capitolo 8 descrive le simulazioni atomistiche di dinamica molecolare di aggregati porfirina- peptide . Capitolo 9 presente uno studio degli stessi sistemi condotto attraverso simulazioni di dinamica molecolare a grana grossa, che utilizzano il modello MARTINI. Infine, il Capitolo 10 presenta un sommario delle tre linee di ricerca, mettendo in evidenza i risultati notevoli ottenuti in questa tesi. Seguono poi tre Appendici.

Sur la base des travaux antérieurs du laboratoire, nous avons développé une nouvelle approche synthétique énantiosélective, en deux étapes, pour l’accès à des glutarimides fonctionnalisés à partir de cyclobutanones facilement accessibles, selon deux directions: une stratégie impliquant une extension de cycle à deux atomes et une stratégie basée sur une contraction de cycle à deux atomes. En parallèle, nous avons démontré que les arynes porteurs de la chiralité axiale en position ortho de la triple liaison réactive peuvent être générés à partir des précurseurs iodo/triflate de type Suzuki et réagissent in situ avec divers substrats. Leur stabilité configurationnelle et leur grande réactivité nous ont permis de proposer une nouvelle méthode de synthèse pour introduire un fragment biaryle à chiralité axiale au sein de pratiquement toutes molécules organiques réactives vis-à-vis des arynes
Based on the previous work in our laboratory, we have developed a new enantioselective two-step synthetic approach to access functionalized glutarimide derivatives using readily available cyclobutanones following two directions: a two-atom ring expansion strategy and a two-atom ring contraction strategy. Meanwhile, we have demonstrated that arynes bearing axial chirality ortho to their reactive triple bond can be generated from the corresponding iodo/triflate Suzuki-type precursors and trapped in situ by various substrates. Their configurational stability and high reactivity allow us to propose a new synthetic method for the facile introduction of an axially chiral biaryl unit onto virtually any organic molecule reacting with arynes

La conception de nouvelles molécules chirales est depuis plusieurs décennies un enjeu majeur. Ces travaux ont porté sur la synthèse ainsi que la caractérisation de diverses molécules à base d’hélicènes. En effet, les hélicènes sont chiraux et présentent des propriétés chiroptiques exceptionnelles. Ainsi, la combinaison de ces entités chirales associées à divers motifs permet la modulation de ces propriétés. Dans une première partie de ce manuscrit, nous nous sommes intéressés à l’association des hélicènes avec le motif tétrathiafulvalène (TTF) associant ainsi les propriétés redox du TTF à la chiralité des hélicènes. Une seconde partie concerne la préparation d’hélicènes luminescents à base de benzothiadiazole et de BODIPY avec pour objectif l’émission de lumière circulairement polarisée (CPL). Dans une troisième partie, nous avons étudié l’autoassemblage et la réactivité des motifs hélicéniques sur différentes surfaces de cuivre ou d’or. Enfin, nous avons réalisé des jonctions moléculaires à base d’hélicènes comme molécules uniques. En conclusion, nous avons développé différents motifs chiraux redox et photo-actifs ainsi que la formation de domaines auto-assemblés et des jonctions moléculaires à base d’hélicènes
The development of new chiral molecules is a major challenge since few decades. This PhD work focuses on the synthesis and the characterisation of a variety of molecules based on helicenes. Indeed, helicenes are chiral and show exceptional chiroptical properties. Therefore, combining these chiral entities with various motifs allow the modulation of their properties. In a first part of this manuscript, we were interested in the association of helicenes with tetrathiafulvalene (TTF), thus combining the redox properties of TTF with the chirality of helicenes. The second part concerns the preparation of luminescent helicenes based on benzothiadiazole and BODIPY for circularly polarised light luminescence (CPL). In a third part we investigated the self-assembly and the reactivity of helicenes on gold and copper surfaces. Finally, we have prepared single molecule junctions based on helicenes. In Conclusion, we developed different redox and photoactive helicenes with applications towards the self-assembly on surfaces and single molecular junctions

This thesis deals with the design and synthesis of ligands for asymmetric catalysis: palladium catalyzed allylic alkylations, and rho-dium and iridium catalyzed hydrogenations of olefins. Chirally flexible phosphepine ligands based on biphenyl were synthesized and their properties were studied. The rotation barrier for configurationally flexible phosphepines was determined by NMR spectroscopy. The ratio of the atropisomers was shown to depend on the group bound to phosphorus. Only complexes with two homochiral ligands bound to the metal center were observed upon complexation with Rh(I). It was shown that one diastereomer of the flexible ligand exhibits higher activity but lower selectivity than its diastereomer in the rhodium catalyzed hydrogenation of methyl alfa-acetamidocinnamate. These ligands were also tested in nickel catalyzed silabora-tions. Chiral P,N-ligands with pseudo-C2 and pseudo-CS symmetry based on pyrrolidines-phospholanes or azepines-phosphepines were synthesized and studied in palladium catalyzed allylic alkylations. Semi-flexible azepine-phosphepine based ligands were prepared and their ability to adopt pseudo-C2 or pseudo-CS symmetry depending on the substrate in allylic alkylations was studied. It was shown on model allyl systems with flexible N,N-ligands that the ligand prefers CS-symmetry in compexes with anti-anti as well as syn-syn allyl moieties, but that for the latter type of complexes, according to computations, the configuration of the ligand is R*,R* in the olefin complexes formed after addition of a nucleophile to the allylic group. A preliminary investigation of the possibilities to use a su-pramolecular approach for the preparation of P,N-ligands with pseudo-C2 and pseudo-S symmetry was made. An N,N-ligand with C2 symmetry was prepared and its activity in palladium catalyzed ally-lic alkylation was studied. Pyridine-based P,N-ligands were tested in iridium catalyzed hy-drogenations of unfunctionalized olefins with good activities and se-lectivities. In order to attempt to improve the selectivity, ligands with a chirally flexible phosphepine fragment were prepared and applied in catalysis with promising results.
QC 20100929

This thesis conducts a systematic study on the chirality of light and its interaction with chiral matter. In the theory section, we introduce a measure of local density of chirality, applying to arbitrary electromagnetic fields. This optical chirality suggests the existence of superchiral modes, which are more selective than circularly polarized light (CPL) in preferentially exciting single enantiomers in certain regions of space. Experimentally, we demonstrate an 11-fold enhancement over CPL in discriminating chiral fluorophores of single handedness in a precisely sculpted superchiral field. This result agrees to within 15% with theoretical predictions. Any chiral configuration of point charges is beyond the scope of our theory on optical chirality. To address chiroptical excitations at nanoscale, we develop a model of twisted dipolar oscillators. We design a simple tunable chiral nanostructure and observe localized chiroptical “hot spots” with dramatically enhanced circular differential scattering. Our work on superchiral light and 3D chiral metamaterials establishes optical chirality as a fundamental and tunable property of light, with implications ranging from plasmonic sensors, absolute asymmetric synthesis to new strategies for fabricating three-dimensional chiral metamaterials. This thesis is organized as such: Chapter 1 provides a background on previous studies of chiroptical phenomena, and recent efforts in preparing chiral metamaterials. Chapter 2 derives theory on optical chirality, superchiral modes and coupled-dipolar oscillators at nanoscale. Chapter 3 introduces material, apparatus, and pitfalls in chiroptical experiments. Chapter 4 is an overview of the experimental procedure and results on generating and observing superchiral enhancement. Chapter 5 describes the experiments on using spectroscopic polarization microscopy to study chiral 3D chiral metamaterials. Finally in Chapter 6, I discuss quantization of optical chirality and perspectives on future directions.
Physics

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, June 2015.
"May 2015." Cataloged from PDF version of thesis.
Includes bibliographical references (pages 105-114).
Single Walled Carbon Nanotubes are of great interest as a semiconducting material with diameters around 1nm and length in the 100s of nm to mm range. The large aspect ratio, near-infrared wavelength bandgap and a high conductivity enable a large number of optical and optoelectronic applications inaccessible by other materials. However, carbon nanotubes as produced are heterogeneous in electronic properties that are dependent on their chirality. Small changes in geometry of the tube dramatically change the bandgap of the tube, and whether it is metallic or semiconducting. This thesis establishes the first reproducible method by which to separate a single electronic type of carbon nanotube, i.e. a single chirality. The mechanism by which this separation occurs is explored experimentally and via quantitative modelling. The thesis ends with a demonstration of the first near infrared single chirality carbon nanotube solar cell.
by Rishabh M. Jain.
Ph. D.

Les résultats décrits dans cette thèse démontrent une relation complexe entre le confinement géométrique de molécules à 2D et les propriétés de chiralité. Il a été démontré qu’une chiralité multimodale peut être observée pour des systèmes non chiraux par le biais du confinement 2D. Les molécules H5T forment, sur Au(111), des domaines pour lesquels deux types de chiralité peuvent être observés. Les études sur le système H5T/Au(111) ont prouvé que des interactions simples, de type van der Waals sont susceptibles de créer des chiralités complexes, ce qui donne un caractère générique a ce type de phénomène. Une autre question importante est l’apparition, pour les molécules C-12, des domaines chiraux induits par des interactions intermoléculaires spécifiques: les liaisons hydrogène entre les groupements azobenzènes de molécules voisines. L’orientation des deux domaines chiraux est déterminée par l’orientation de l’un des deux dimères d’azobenzène stable par rapport à l’Au(111).La seconde partie de la thèse est dédiée à l’étude de l’influence du confinement 3D sur la chiralité de gouttes de cristal liquide cholestérique (CLC). Grâce à la nature photo-sensible du dopant chiral utilisé, nous avons été capables de modifier le pas choléstérique du mélange de CLC et par conséquent de déterminer l’expression de la chiralité pour un ratio rayon/pas choléstérique variable. Nous sommes parvenus à contrôler le pas choléstérique au sein de gouttes par irradiation UV et nous avons étudié les variations structurelles que l’irradiation induite. Nous avons observé que le confinement 3D d’un mélange de CLC photo-sensible a une influence positive sur l’inversion de l’hélice dans la goutte
The first part of the thesis is devoted to studies of the self-assembled monolayers of discotic liquid crystals by the STM measurements at the liquid/solid interface. For the case of a model H5T molecule the self-assembled monolayers have evidenced both: point and organizational types of chirality, despite of the fact that neither the molecule nor the substrate was chiral. For another molecular system, C-12 - a triphenylene peripherally substituted with azobenzene moieties, self-assemblies bearing the chiral nature were also evidenced. Chirality was induced by formation of six dimers of azobenzene subunits coming from the neighboring molecules, which formed “rosettes” of clockwise or counter-clockwise rotation. For the H5T, the chirality was mediated by classical van der Waals interactions between molecules and between molecules and substrate. In the case of C-12 it was shown that the self-assembly originates from the substrate-mediated hydrogen bonding between the azobenzene moieties of neighboring molecules. The second part of the thesis presents studies of the influence of the 3D confinement on the chirality of the photoactive cholesteric liquid crystal (CLC) droplets. Due to the photo-responsive character of a chiral dopant we were able to modify the cholesteric pitch of the CLC mixture and thus to map the expression of chirality for a varying geometrical confinement parameter: radius-to-pitch. We evidenced a successful control of the droplets structure by UV irradiation and we studied the induced structural changes. In particular, the 3D confinement of a photo-responsive CLC mixture was shown to positively support the helix inversion within the cholesteric droplets

Les chirosciences étudient la préparation, les propriétés et les interactions des molécules chirales. La chromatographie chirale est une technique répandue pour analyser et produire des énantiomères. Son principe réside dans les interactions entre un sélecteur chiral et chaque énantiomère pour donner des complexes diastéréomères labiles avec différentes énergies et une rétention si différente.Cependant, les mécanismes de reconnaissance chirale ne sont pas bien connus, en particulier pour les sélecteurs chiraux les plus efficaces, qui sont à base de polysaccharides (en particulier de la cellulose et des carbamates d'amylose). Par exemple, le rôle du modificateur de phase mobile (co-solvant tel que l'alcool mélangé avec de l'heptane dans HPLC et avec du CO2 dans SFC) n'est pas expliqué dans la plupart des cas. Sur des phases stationnaires chirales à base de polysaccharide, l'effet du modificateur ne peut pas être restreint à la différence de polarité, ce qui entraîne une variation attendue des temps de rétention: plusieurs exemples ont rapporté la perte d'une énantioséparation ou même une inversion de l'ordre d'élution des énantiomères par changer le modificateur alcoolique.Notre travail vise à décrire les effets sur la rétention, l'ordre d'élution et l'enthalpie des complexes, lors de l'utilisation de mélanges de co-solvants dans la phase mobile. La description de ces comportements chromatographiques inhabituels peut aider à améliorer notre compréhension des mécanismes de reconnaissance chirale
Chirosciences study the preparation, the properties and the interactions of chiral molecules. Chiral chromatography is a widespread technique to analyse and produces enantiomers. Its principle lies in the interactions between a chiral selector and each enantiomer to give labile diastereomeric complexes with different energies and so different retention.However, chiral recognition mechanisms are not well known, particularly for the most efficient chiral selectors, which are based on polysaccharides (especially cellulose and amylose carbamates). For instance, the role of the mobile phase modifier (co-solvent like the alcohol mixed with heptane in HPLC and with CO2 in SFC) is not explained in most case.On polysaccharide-based chiral stationary phases, the effect of the modifier can not be restricted to the difference of polarity, resulting in expected variation of retention times: several examples reported the loss of an enantioseparation or even a reversal of elution order of the enantiomers by changing the alcoholic modifier.Our work aims to describe the effects on retention, elution order and enthalpy of the complexes, when using mixtures of co-solvents in the mobile phase. The description of such unusual chromatographic behaviours may help to improve our understanding of the chiral recognition mechanisms

Les complexes de coordination supramoléculaires constitués de briques moléculaires chirales sont bien décrits dans la littérature. En revanche, les systèmes combinant briques moléculaires chirales et chiralité inhérente restent encore très peu explorés. C'est dans ce contexte que s'inscrit ce travail de recherche. Nous avons étudié de nouveaux ensembles supramoléculaires de coordination tridimensionnels chiraux pour des applications potentielles en catalyse. La synthèse a été développée par auto-assemblage de briques moléculaires différentes : ligands azotés bitopiques, ligands tritopiques et complexes de coordination. Neuf auto-assemblages différents ont été réalisés avec les ligands bitopiques dérivés de l'imidazole et de complexes de Pd (II) et de Pt (II). Les auto-assemblées triangulaires T-7, T-9, T-10, T-12, T-13 et T-15 ont été obtenues majoritairement alors que les structures T-11, C-11a et C-11b ou encore T-14 et C-14, ont été obtenues sous la forme d'un mélange triangle-carré dont les proportions dépendent de la concentration et de la nature du solvant. Leur caractérisation et l'étude de leur structure en solution ont permis de mettre en évidence une chiralité inhérente à leur structure. A notre connaissance, l'auto-assemblée T-7 est la première structure triangulaire chirale, composée de briques moléculaires achirales, complètement caractérisée en solution. A partir de l'auto-assemblage ligand tritopique / ligand bitopique / complexe métallique, trois structures prismatiques chirales ont été synthétisées grâce à l'encapsulation d'un invité pyrènecarboxaldéhyde (I-8). La structure Prism-2 a été obtenue avec un excellent rendement et une très bonne pureté. Sa caractérisation par spectroscopie RMN en solution et son analyse en DFT ont permis de déterminer la chiralité inhérente de la structure obtenue comme un racémique P-(Prism-2⊃(I-8)2) et M-(Prism-2⊃(I-8)2). L'analogue énantiopur Prism-3 est obtenu par l'auto-assemblage de L4Me, 4tpt et du complexe énantiopur Pd-5 en présence de I-8. La spectroscopie RMN en solution a permis de déterminer la configuration de l'énantiomère obtenu, (λ,P)-(Prism-3⊃(I-8)2), et confirme la chiralité inhérente de ces structures prismatiques
Supramolecular coordination complexes, constituted of chiral molecular bricks, are well described in the literature. However, supramolecular complexes combining chiral building blocks and inherent chirality are underexplored. In this context, we have undertaken the synthesis of novel chiral three-dimensional supramolecular coordination complexes for their potential uses in catalysis. Their synthesis have been carried out by self-assembly of different molecular bricks: ditopic and tritopic nitrogen-ligands, and coordination complexes. Nine different self-assemblies have been synthesized with imidazole-based ditopic ligands and palladium(II), or platinum(II), coordination complexes. On the one hand, the triangular self-assemblies T-7, T-9, T-10, T-12, T-13 and T-15 have been obtained as the major component. On the other hand, structures T-11, C-11a-b or T-14 and C-14 have been obtained as a mixture of triangular and square structures in a ratio depending on the concentration and the solvent. The full characterization of these structures in solution has shown their inherent chirality. To our knowledge T-7 is the first triangular supramolecular coordination complex constituted of achiral components shown to be chiral in solution. Self-assembly syntheses of tritopic and ditopic ligands as well as palladium(II) coordination complexes were carried out, in the presence of pyrenecarboxaldehyde (I-8). Three chiral prismatic structures have been obtained. Prism-2 has been characterized by NMR spectroscopy in solution and DFT analysis which supports its inherent chirality. The racemic (P-(Prism-2⊃(I-8)2) / M-(Prism-2⊃(I-8)2)) has been isolated with an excellent yield and a very good purity. Prism-3, an enantiopure analog of Prism-2, was obtained by self-assembly synthesis of L4Me, 4tpt and the enantiopure coordination complex Pd-5 in the presence of I-8. The configuration of the isolated enantiomer was carried out by NMR spectroscopy in solution and assigned to (λ,P)-(Prism-3⊃(I-8)2), confirming the inherent chirality of the different prismatic structures

Les polymères conjugués forment une nouvelle classe de matériaux avec un fort potentiel pour des applications en optoélectronique, grâce à leurs propriétés facilement modifiables et leur transformabilité. Un moyen proposé d’influencer leurs performances est d’introduire de la chiralité. Le point central de cette thèse est la synthèse de nouveaux polymères conjugués chiraux statistiques dont les performances dans des dispositifs photovoltaïques sont supérieures à leurs homologues racémiques ou à l’homopolymère correspondant. Ainsi, la valeur ajoutée de la chiralité est démontrée. Des modifications structurales additionnelles ont été proposées afin d’obtenir des gammes de polymères plus variées : soit en changeant le monomère principal (indacenodithiophene ou benzodithiophene), soit en changeant l’hélicène servant de co-monomère. Finalement, les copolymérisations résultent en la formation de petits oligomères. Ces derniers présentent des propriétés chiroptiques intéressantes, telles qu’un dichroïsme circulaire électronique plus élevé que la moyenne. L’émission de lumière polarisée circulairement est également observée, ce qui n’est pas le cas dans les polymères statistiques
Conjugated polymers are an emergent class of materials with an exceptional potential for optoelectronic applications, thanks to their highly tunable properties and their processability. One of the ways to enhance their performances is to introduce chirality. The highlight of this thesis is the synthesis of novel chiral statistical conjugated polymers that were incorporated into photovoltaic devices. It was found that they outperform both their racemic counterparts and the homopolymer used for comparison. Structural modifications were proposed to obtain more diverse chiral conjugated polymers, either by changing the main building block (indacenodithiophene or benzodithiophene), or the helicene comonomer. Finally, by performing a co- polymerization, we obtained small oligomers that presented interesting chiroptical properties such as electronic circular dichroism with higher-than-average absorption dissymmetry factors and emission of circularly polarized luminescence; the latter is interestingly not observed in the statistical polymers

Les acides α-aminés non protéinogènes sont des composés riches d’applications et peuvent donner accès à des composés possédant des propriétés biologiques intéressantes ou à des analogues de peptides. Ainsi, de nombreuses méthodes de synthèse asymétrique ont été développées. Parmi celles-ci, seulement quelques méthodes utilisent la chiralité d’acides α -aminés tertiaires naturels pour accéder à des acides α -aminés quaternaires et il n’existe que peu de synthèses asymétriques absolues d’acides α -aminés tertiaires.Notre équipe a précédemment développé une méthode de synthèse d’acides α-aminés quaternaires reposant sur le concept de la mémoire de chiralité. Cette méthode utilise la chiralité axiale d’amides aromatiques tertiaires pour l’alkylation stéréoselective d’énolates d’acides aminés. Lors de ma thèse, nous avons souhaité appliquer cette méthode d’alkylation stéréosélective d’énolate à d’autres types de réaction tels que la réaction d’aldolisation (utilisant un aldéhyde comme électrophile, et dans ce cas il est nécessaire de contrôler un second centre asymétrique), la réaction d’arylation (utilisant un sel de diaryliodonium comme électrophile) ou à la synthèse totale des composés biologiques intéressants. Des résultats préliminaires encourageants obtenus dans des réactions d’aldolisation (dans le cas avec du benzaldéhyde), d’arylation ainsi que dans la synthèse du précurseur de la L-Méthyl DOPA seront présentés.D’autre part, nous exposerons également la stratégie de synthèse des dérivés d’acides α-aminés tertiaires et des aminoalcools, qui utilise le concept de la chiralité gelée. Cette méthode repose sur l’emploi de la chiralité axiale dynamique des amides aromatiques tertiaires, qui est gelée dans un cristal chiral, et une réaction d’alkylation stéréosélective d’énolate conduisant à des acides aminés énantiomériquement enrichis. En effet, en partant de la glycine, nous avons réussi à trouver un composé de départ qui cristallise dans un groupe d’espace chiral, qui donne donc des cristaux chiraux après la cristallisation. Après avoir trouvé des conditions optimales pour la réaction d’allylation, plusieurs autres électrophiles ont été employés avec succès. Les produits alkylés sont obtenus avec des rendements allant jusqu’à 80% et des excès énantiomériques allant jusqu’à 96% sans utiliser d’autre source de chiralité externe que celle du cristal. L’ouverture de ces composés conduit à la formation des acides α-aminés tertiaires énantiomériquement enrichis. Il s’agit donc d’une synthèse asymétrique absolue d’acides α-aminés
Non proteinogenic α-amino acids can lead to compounds which exhibit interesting biological properties, or peptides analogues. Numerous methods for asymmetric synthesis of these compounds have been developed. However, few examples have used the chirality of natural tertiary α-amino acids for the synthesis of quaternary α-amino acids, and few examples of asymmetric absolute synthesis to access to tertiary α -amino acids have been described so far. Our research group has previously developed a synthesis of enantioenriched quaternary α-amino acids, based on memory of chirality and using the axial chirality of tertiary aromatic amides for stereoselective alkylation of an enolate of an amino acid.This thesis focuses on expending this methodology to other type of reactions, for example, aldolisation reactions (using an aldehyde as electrophile, in this case it is necessary to control the second asymmetric center), arylation reactions (using a diaryliodonium salt as electrophile) or to the the total synthesis of compounds exhibiting interesting biological properties. Herein, we will show our preliminary results in aldolisation reactions (with benzaldehyde), in arylation reactions and also in the total synthesis of L-Methyl DOPA.On the other hand, we will also present an enantioselective synthesis of tertiary α-amino acids derivatives and of amino alcohols based on the principle of frozen chirality. The strategy uses the dynamic axial chirality of tertiary aromatic amides, which is frozen in chiral crystal, and a stereoselective alkylation reaction of enolate leads to enantioenriched α-amino acids. A compound synthesized from glycine has been finally selected to optimise the asymmetric allylation reaction. These optimales conditions were then successfully employed with various electrophiles. Alkylated products were obtained in yield up to 80% and enantiomeric excesses up to 96% using only chirality of crystal. The deprotection of alkylated products leads to the formation of enantienriched α-amino acids

Le travail présenté dans ce mémoire est consacré à la synthèse de cycles pseudopeptidiques construits à partir d'aza-β³-aminoacides, et à la détermination des conformations adoptées par ces cycles. Le travail réalisé a permis de montrer que les cycles obtenus à 8, 16 et 24 liaisons adoptent des conformations privilégiées dans lesquelles la configuration relative des atomes d'azote chiraux est fixée en dépit du phénomène d'inversion pyramidale associé à la structure électronique de cet élément chimique, en réponse à des contraintes structurelles qui varient selon la taille du macrocycle. Ces cycles existent alors sous la seule forme de deux invertomères en équilibre. La constante de vitesse de cet équilibre, qui est indiscernable de la barrière d'inversion pyramidale des atomes d'azote, est maintenue à des valeurs étonnamment faibles par les contraintes conformationnelles. L'étude de ces macrocycles originaux dans le domaine de la chiralité a permis d'apporter en particulier des résultats nouveaux concernant l'influence de l'encombrement stérique des chaînes latérales sur la vitesse d'inversion pyramidale des atomes d'azote, mais aussi sur le transfert de chiralité d'éléments d'asymétrie exocycliques vers la séquence chirale du squelette, et enfin de montrer également l'intérêt des nouveaux cycles à 8 chaînons à travers l'étude de leur conformation
The work depicted here is devoted to the synthesis of pseudopeptides built from aza-β³-aminoacid units, and to their conformational analysis. The results show that the cycles with 8, 16, and 24 bonds each adopt a ground conformation where the relative configuration of the chiral nitrogen atom is fixed in response to specific structural constraints, and despite the nitrogen pyramidal inversion phenomenon. The cycles just undergo equilibrium between two invertomeric forms, and the energetic barrier associated with the macrocycle inversion reveals surprisingly slow considering the size of the compounds. The influence of steric crowding of the side chains on the inversion rate has been carefully studied, but also the transfer of chirality from exocylic elements towards chirotopic nitrogen atoms inside the backbone. A specific chapter is devoted to the 8-membered rings, that reveal the interest of these newly described compounds in the domain of nitrogen chirality

In this work mesoporous organisilica materials are synthesized through the silica sol-gel process. For this a new class of precursors which are also surfactant are synthesized and self-assembled. This leads to a high surface area functionality which is analysized with copper (II) and water adsorption.
Im Rahmen dieser Arbeit werden mesoporöse Amin-funktionalisierte Organo-Silikate durch den Silika Sol-Gel Prozess hergestellt. Dabei werden neue Alkoxysilyl-Precursoren synthetisiert und condensiert die die gewünschte Funktion auf die Oberfläche dirigieren. Herstellt werden primäre, secundäre und chirale Amine. Die Oberflächenfunktionalität wird mit Kupfer (II) und Wasser Adsorption analysiert.