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207 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Organic Chemistry, 1981

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 193-199). Available also in a digital version from Dissertation Abstracts.

published_or_final_version / Chemistry / Master / Master of Philosophy

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

An empirical approach to the study of phosphine compounds was completed using Molecular Mechanics 2 (MM2), and several computer programs written to descibe and analyze the final geometric orientations of the molecules. The calculations were performed on 64 conformers of 16 different phosphines. Results from these calculations were compared to those previously obtained for MNDO and MINDO/3 calculations, and to experimental data. Cone angles calculated from the MM2 optimized geometries, were compared to Tolman's original work, and to values obtained from semiempirical calculations, and to experimental results. In general, it was found that weighted average cone angles best represent the size of phosphine ligands. / Department of Chemistry

Thesis (Ph.D.) -- University of Adelaide, Department of Organic Chemistry, 1981.

Thesis (Ph. D.)--Michigan State University. Dept. of Chemistry, 2008. / Title from PDF t.p. (viewed July 31, 2009). Includes bibliographical references (p. 179-187). Also issued in print.

Thesis (M. S.)--Biomedical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Zhu, Cheng; Committee Member: Babensee , Julia; Committee Member: Garcia, Andres; Committee Member: McIntire, Larry; Committee Member: Selvaraj, Periasamy; Committee Member: Springer, Timothy

This thesis concerns the construction, use and modulation of various host–guest systems, from small bispidines for binding of inorganic ions to bisporphyrin clips for supramolecular systems. Small flexible molecules undergo fast conformational movements when in solution. These conformational movements generate time-averaged population-weighted chemical shifts, coupling constants and NOEs when analysed by NMR spectroscopy. A bisporphyrin clip was designed to be used as a host for restriction of conformational movements of small flexible molecules by ditopic metal-ligand binding. Based on conformational analysis in combination with NMR analysis of molecular flexibility in solution (NAMFIS), the relative stereochemistry of flexible alditol-derived diamines containing three or four consecutive stereocentres could be determined. To further explore the idea of conformational deconvolution via host–guest binding, two flexible molecular tweezers with photoswitchable moieties were developed. Upon photoswitching cis/trans isomerisation facilitates the opening and closing of these bisporphyrin hosts. A guest molecule could then be exposed to a “catch and stretch” or “catch and release” effect. Preliminary studies have shown that photoisomerisation of the constructed systems is possible without photodecomposition and preliminary binding studies have been conducted. Controlled modulation of molecular conformations is of interest especially if the conformational steering activates a unit working as a nucleator in a larger structure or facilitates a reaction. The protonation-triggered modulation of bispidine conformations has been investigated. In addition to previously reported conformations we have observed that upon diprotonation a bispidine derivative can be driven into the unusual boat-boat conformation. Finally, the unexpected formation of persistent organic radicals with a cyclophane motif from the reaction of N,N´-diphenyl-1-5-diazacyclooctane and AgBF4 is described. Interestingly, these diradicals exhibit features such as intramolecular π-stacking without lateral displacement and also intramolecular spin pairing.