Ferroelectric liquid crystals (FLCs) exhibit a bulk electric polarization (PS) that can be coupled to an electric field to produce an ON-OFF light shutter, and are being investigated as an alternative to nematic liquid crystals in display applications. Commercial FLC mixtures normally consist of a small amount of chiral dopant in an achiral smectic C (SmC) liquid crystal host. Because the switching time of FLC display is inversely proportional to the induced polarization, the design of chiral dopants with high polarization powers (p) is a key aspect of FLC research. Such work requires an understanding of the relationship between molecular structure and polar order in the chiral SmC* phase. Previous work in the Lemieux group focused on 2,2’-spirobiindan-1,1’-diones dopants, and a conformational model was proposed to explain the observed host dependence of the polarization power (p) of these dopants. In order to test this model, the 2,2’-spirobiindan-1,1’-dione core has been modified by introducing polar substituents and by modifying the functional groups linking the core to the alkyl side-chains. Specifically, this thesis focuses on implementing this approach via the synthesis and characterization of chloro- and methyl-substituted 2,2’-spirobiindan-1,1’-dione dopants. Four chiral dopants (2.1a, 2.1b, 2.2a and 2.2b) were synthesized, resolved and their absolute configurations assigned by CD spectroscopy. Their polarization powers were measured in four SmC hosts with different core structures. For both the ether-linked and ester-linked dopants, the addition of a substituent at the 6-position of one indanone ring results in lower polarization powers regardless of the size and polarity of the substituent, which is contrary to the original conformational distribution model. A comparative study of the data suggests that the ester-linked dopants exert much stronger perturbations on the host environment than the ether-linked dopants, especially when the 6-position is substituted. We postulate that this perturbation is chiral in nature, and that the feedback effect of chirality transfer causes a shift in the conformational distribution of the dopant favoring conformers with negative polarity. Probe experiments were performed to detect the effect of chirality transfer feedback (CTF) in the case of the chloro-substituted diester dopant (2.1b), showing consistent results with the postulate. / Thesis (Master, Chemistry) -- Queen's University, 2007-09-28 12:26:06.486

Chirality can be induced in achiral solvent molecules located near a chiral molecule or surface, but there have been very few systematic studies in this field either experimentally or theoretically. The focus of this thesis is to study the chirality transfer from chiral molecules to achiral solvents. To capture the chirality transfer in solvent molecules, a solvent model that is sensitive to the changes in the environment is needed. We developed new polarizable and flexible models based on an extensive series of ab initio calculations and molecular dynamics simulations. The models include electric field dependence in both the atomic charges and the intramolecular degrees of freedom. Modified equations of motion are required and we have implemented a multiple time step algorithm to solve these equations. Our methodology is general and has been applied to ethanol as a test. For other solvents in our simulations, such as 2-propanol, limited models are used. The chirality transfer from chiral solutes to achiral solvents and its dependence on the solute and solvent characteristics are then explored using the new polarizable models in molecular dynamics simulations. The chirality induced in the solvent is assessed based on a series of related chirality indexes originally proposed by Osipov[Osipov et al., Mol. Phys.84, 1193(1995)]. Two solvents are considered: Ethanol and benzyl alcohol. The solvation of three chiral solutes is examined: Styrene oxide, acenaphthenol, and n-(1-(4-bromophenyl)ethyl)pivalamide (PAMD). All three solutes have the possibility of hydrogen-bonding with the solvent, the last two may also form π-π interactions, and the last has multiple hydrogen bonding sites. The chirality transfer from chiral surfaces to achiral solvents is also explored. Emphasis is placed on the extent of this chirality transfer and its dependence on the surface and solvent characteristics is explored. Three surfaces employed in chiral chromatography are examined: The Whelk-O1 interface; a phenylglycine-derived chiral stationary phase (CSP); and a leucine-derived CSP. The solvents consist of ethanol, a binary n-hexane/ethanol solvent, 2-propanol, and a binary n-hexane/2-propanol solvent. Molecular dynamics simulations of the solvated chiral interfaces form the basis of the analysis and position dependent chirality indexes are analyzed in detail. / Thesis (Ph.D, Chemistry) -- Queen's University, 2009-09-24 00:25:15.174

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Les polyoxométallates (POMs) dendritiques constituent une catégorie de catalyseursrelativement nouvelle. L’association d’un dendrimère avec un polyoxométallate permet debénéficier des propriétés catalytiques intéressantes des POMs et de pouvoir modifier cespropriétés en variant la structure du dendrimère. Une variété de composés hybrides POMsdendritiques a été préparée par formation de liaisons ioniques entre une unité POM anioniqueachirale et des cations dendritiques énantiopurs. Ces composés se sont montrés très efficacespour la catalyse d’oxydation asymétrique, avec une stéréosélectivité significative. Cesrésultats ont démontré pour la première fois un transfert de chiralité d’une structure organiqueénantiopure vers une unité POM achirale. Ces composés sont stables et recyclables dans desconditions douces, sans perte significative de réactivité et de stéréosélectivité. / Polyoxometalates (POMs) represent a new generation of catalysts. Association of dendrimersand POMs allows modification of POM catalytic properties by modifying the dendrimerstructure. Several dendritic POM hybrid compounds have been prepared by ionic bondformation between an anionic POM unit and enantiopure dendritic cations. These compoundsare efficient for asymmetric oxidation catalysis with significant stereoselectivity. Theseresults have shown, for the first time, a chirality transfer from an enantiopure organicstructure to an achiral POM unit. These compounds are stable and recoverable under mildconditions without any significant loss of reactivity and stereoselectivity.

La synthèse asymétrique d’aza-hétérocycles (tétrahydro-isoquinoléines et naphtodiazépines) a été réalisée grâce à la mise en œuvre d’un processus faisant intervenir des réactions radicalaires et polaires en cascade à partir des ènediynes portant un centre stéréogène. Ce processus implique successivement : la formation d’un ényne-allène (via une migration-1,3 de proton, une réaction d’un alcyne terminal avec un carbénoïde de cuivre, ou encore une réaction d’homologation de Crabbé)/ la cyclisation de Saito-Myers/ le transfert-1,5 d’un atome d’hydrogène/ la recombinaison du biradical résultant. Les deux dernières étapes élémentaires de ce réarrangement étaient idéalement adaptées à l’application d’une stratégie basée sur le phénomène de mémoire de chiralité. Des études mécanistiques basées sur des expériences de marquage isotopique et des calculs théoriques ont permis de mieux comprendre les paramètres qui contrôlent la régio- et la stéréosélectivité de la réaction. L’ambition de contrôler par cette voie, via une double mémoire de chiralité, deux centres stéréogènes nous a conduits à étudier le transfert de la chiralité axiale d’un motif allénique judicieusement substitué. Cette étude a permis de découvrir une cycloisomérisation originale catalysée par le cuivre (I) conduisant à des fulvènes chiraux via un double transfert de chiralité (centrique-axial-centrique). / The asymmetric synthesis of azaheterocycles (tetrahydorisoquinolines and naphthodiazepines) was successfully achieved via the polar/radical cross-over rearrangement of enediynes bearing a stereogenic center. This process involves successively : enyne-allene formation (via 1,3-proton shift, reaction of a terminal alkyne group with carbenoids or Crabbé homologation)/Saito-Myers cyclization/1,5-hydrogen atom transfer/biradical recombination. It was ideally suited to apply a strategy based on the memory of chirality phenomenon. Mechanistic studies based on isotopic labelling and theoretical calculations enabled to go deeper into the understanding of the parameters controlling the regio- and the stereoselectivity of the reaction. The ambition to control two stereogenic centers via double memory of chirality, led us to investigate the transfer of the axial chirality of a designed allenic moiety. This study led to the discovery of an original copper (I)-mediated cycloisomerization leading to chiral fulvenes and proceeding via central-to-axial-to-central double chirality transfer.