Chemical Modifications of Cyclodextrins for Ion Conduction, Sensing and Metal Sequestration
Committee MemberDerksen, Darren J.
Shimizu, George K. H.
Subjectcyclodextrin, self-assembly, liquid crystals, ionic conductivity, contrast agent
MetadataShow full item record
AbstractSupramolecular assemblies generally consist of molecules held together via non-covalent interactions of various strengths. These assemblies possess an astonishing variety of potential applications in numerous fields. In this thesis, several families of new cyclodextrin (CD) derivatives were synthesized, characterized and discussed. The novel derivatives were prepared with the intention to study their supramolecular assembly in solid states and solutions and develop novel applications. In the solid states, studies on structure-property relationships uncovered the influence of substitution patterns of amphiphilic CDs on their ability to form various liquid crystalline mesophases. A novel family of amphiphilic CD-based liquid crystals bearing O-acetylated oligoethylene glycol (OEG) chains at the secondary face is presented in Chapter Three. Unlike most of the previously reported liquid crystals based on chemically modified CDs which rely on H-bonding as the primary intermolecular force, the present CD derivatives self-assemble into highly ordered smectic liquid crystal phases via the weaker dipole-dipole intermolecular forces. The obtained materials were found to possess much improved properties, such as improved thermostability, reduced clearing temperatures and better fluidity. Chapter Four reports another family of amphiphilic CDs bearing O-acetylated oligoethylene glycol chain by inverting the substitution patterns on β-CDs by simply placing hydrophobic chains to the secondary face and O-acetylated OEG groups at the primary face; we showed that it is possible to transform the nature of mesophases from smectic to columnar. This investigation reveals some intriguing properties of CD scaffolds as a unique class of host mesogens. In addition to introducing OEG groups to CDs, we also attempted to introduce an OEG linker to the known cholesterol mesogen in Chapter Five to obtain either monomeric or dimeric cholesterol mesogens which showed interesting LC properties. A portion of this monograph focused on the potential applications of amphiphilic CD-based liquid crystalline materials. To this aim, we extended the design of our systems by introducing different functional groups at the end of OEG chains. For example, in Chapters Six to Eight, a group amphiphilic CD bearing non-polar alkyl chains at the primary face while multiple OEG groups of different lengths, terminated with a polar nitrile group, was developed; the addition of a nitrile functionality at the end of each OEG chain was found to increase the stability and temperature range of the mesophases; we found the smectic mesophases formed by these novel amphiphilic CDs have great ability to act as electrolytes for the conduction of lithium (Chapter Six and Eight) as well as sodium (Chapter Seven). Furthermore, when the terminal nitrile functionality was replaced with a carboxylic acid, a new family of amphiphilic CD polycarboxylic acids was obtained which constitutes the main topic of Chpater Nine; the introduction of numerous carboxylic acid functionalities at the secondary face of CD serves as a preorganization, that facilitate the formation of complex intra- and intermolecular hydrogen-bond networks in the formed smectic mesophases; introducing water molecules in the mesophases further strengthen H-bond networks by bridging adjacent carboxylic acids groups. We investigate the ability of this novel system for proton conduction and have found very encouraging results. Following our work using different amphiphilic CD-based LC materials for ion-conductions, we noticed that the room temperature crystalline phase can significantly affect the conductive properties of the material. Thus, we designed novel CD heptols displaying liquid crystalline phases at room temperature by inserting unconventional alkyl groups such as those containing cis-alkenic or/and branches at the secondary face. The newly synthesized series of amphiphilic CD derivatives were estimated to have crystal-liquid crystalline transitions below -40 °C. This research is the first to shed light on how to affect the mesomorphic properties of amphiphilic CDs with alkyl groups of bent conformation or containing branches. Copper (I)-mediated alkyne-azide 1,3-dipolar cycloaddition (CuAAC) reaction was used as the key reaction for the prepartion of all amphiphilc CD derivatives mentioned above. By taking adavantage of the methodology, Chapter Eleven reports an extension of my thesis work by investigating the synthesis of a novel chemically modified polyaminocarboxylate based on beta-CD scaffold using CuAAc and its coordination chemistry for lanthanides. A 1,2,3-triazolmethyl residue was created from each CuAAc reaction that advantageously serves as a competent chelating group while displacing the metal coordination center away from the primary rim of β-CD. With the participation of four N-acetate groups from two adjacent glucopyranosyl units of β-CD, a unique octavalent coordination sphere was created to bind each lanthanide with high affinity, while the lanthanide metal still has one open site available for dynamic water coordination. Furthermore, the CuAAC chemistry allowed us the synthesize another pyrene-appended β-CD fluorescent probe (Chapter Twelve), which self-assembles into nanoaggregates in water driven by hydrophobic π–π interactions. The formed fluorescent nanoaggregates were found to exhibit an efficient and selective ratiometric detection of pirimicarb, a potent toxic carbamate pesticide as well as differentiating nitro-aromatic explosives such as 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB) and picric acid (PA).
CitationChampagne, P.-L. (2019). Chemical Modifications of Cyclodextrins for Ion Conduction, Sensing and Metal Sequestration (Unpublished doctoral thesis). University of Calgary, Calgary, AB.
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