Crystal engineering: Design, syntheses and characterization of a family of compounds demonstrating liquid crystalline properties

Persistent Link:
http://hdl.handle.net/10150/279831
Title:
Crystal engineering: Design, syntheses and characterization of a family of compounds demonstrating liquid crystalline properties
Author:
Wells, Kirk Edward
Issue Date:
2001
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Intermolecular interactions govern molecular self-recognition and self-assembly, giving rise to 3-dimensional solids. Thus, independent intermolecular interactions should result in a predictable crystal packing. Our working hypothesis is the crystal packing of symmetrically substituted tetra-n-alkoxy-bis-indane-piperazinediones of H-shaped topography will be governed by three factors: First, assembly of molecules into "one-dimensional" tapes through establishment of reciprocal amide hydrogen bonds. Second, assembly of the tapes into "two-dimensional" grooved sheets through establishment of edge-to-face arene interactions. Third, assembly of the sheets into "three-dimensional" solids by "tongue-in-groove" interdigitation of the n-alkyl "tails" in extended conformations independent of chain length. Liquid crystal properties are anticipated for molecules with hydrocarbon chains of sufficient length. Rupture of one or more of the three structure-determining interactions may be independent of the others and observable. "Dissection" of the melting process by correlation of crystallographic data with thermochemical data would permit formulation of a mechanism for melting. Compounds of this homologous series with methoxy, ethoxy, butoxy, hexyloxy, octyloxy and nonyloxy substituents have been synthesized, crystallized, and studied by X-ray crystallography, differential scanning calorimetry (DSC) and optical microscopy. The solid-state structures for the first three in the series were determined and each engaged in intermolecular amide-to-amide hydrogen bonding interactions that established "ladder-like" parallel tapes. Intertape organization was governed by the development of arene and/or van der Waals contact interactions. The melting behaviors of the series were remarkable in that these were not only high melting solids but most also demonstrate transitions by DSC at lower temperatures and magnitude consistent with liquid crystalline behavior. Also remarkable and consistent with liquid crystalline behavior are the optical properties of the longer alkoxy substituted compounds of the series, demonstrating birefringence of cross-polarized fight. In the case of the tetra-n-hexyloxy compound a transition was observed by optical microscopy that correlates with DSC data. Design, syntheses and characterizations of this new family of compounds, which are highly ordered at the molecular level, supporting our hypothesis of liquid crystalline behavior, are discussed. Using these data a mechanism of melting is postulated and discussed.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Chemistry, Organic.; Engineering, Materials Science.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemistry
Degree Grantor:
University of Arizona
Advisor:
Mash, Eugene A., Jr.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleCrystal engineering: Design, syntheses and characterization of a family of compounds demonstrating liquid crystalline propertiesen_US
dc.creatorWells, Kirk Edwarden_US
dc.contributor.authorWells, Kirk Edwarden_US
dc.date.issued2001en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractIntermolecular interactions govern molecular self-recognition and self-assembly, giving rise to 3-dimensional solids. Thus, independent intermolecular interactions should result in a predictable crystal packing. Our working hypothesis is the crystal packing of symmetrically substituted tetra-n-alkoxy-bis-indane-piperazinediones of H-shaped topography will be governed by three factors: First, assembly of molecules into "one-dimensional" tapes through establishment of reciprocal amide hydrogen bonds. Second, assembly of the tapes into "two-dimensional" grooved sheets through establishment of edge-to-face arene interactions. Third, assembly of the sheets into "three-dimensional" solids by "tongue-in-groove" interdigitation of the n-alkyl "tails" in extended conformations independent of chain length. Liquid crystal properties are anticipated for molecules with hydrocarbon chains of sufficient length. Rupture of one or more of the three structure-determining interactions may be independent of the others and observable. "Dissection" of the melting process by correlation of crystallographic data with thermochemical data would permit formulation of a mechanism for melting. Compounds of this homologous series with methoxy, ethoxy, butoxy, hexyloxy, octyloxy and nonyloxy substituents have been synthesized, crystallized, and studied by X-ray crystallography, differential scanning calorimetry (DSC) and optical microscopy. The solid-state structures for the first three in the series were determined and each engaged in intermolecular amide-to-amide hydrogen bonding interactions that established "ladder-like" parallel tapes. Intertape organization was governed by the development of arene and/or van der Waals contact interactions. The melting behaviors of the series were remarkable in that these were not only high melting solids but most also demonstrate transitions by DSC at lower temperatures and magnitude consistent with liquid crystalline behavior. Also remarkable and consistent with liquid crystalline behavior are the optical properties of the longer alkoxy substituted compounds of the series, demonstrating birefringence of cross-polarized fight. In the case of the tetra-n-hexyloxy compound a transition was observed by optical microscopy that correlates with DSC data. Design, syntheses and characterizations of this new family of compounds, which are highly ordered at the molecular level, supporting our hypothesis of liquid crystalline behavior, are discussed. Using these data a mechanism of melting is postulated and discussed.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectChemistry, Organic.en_US
dc.subjectEngineering, Materials Science.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMash, Eugene A., Jr.en_US
dc.identifier.proquest3026561en_US
dc.identifier.bibrecord.b42177480en_US
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