{"id":{"repo_id":"must-thes","oai_identifier":"oai:scholarsmine.mst.edu:doctoral_dissertations-3099"},"canonical_url":"https://search.dev.ndltd.org/etd/must-thes/oai:scholarsmine.mst.edu:doctoral_dissertations-3099","repository":{"repo_id":"must-thes","name":"Missouri University of Science and Technology","base_url":"https://scholarsmine.mst.edu/do/oai/"},"display":{"title":"The stereochemistry of selected supramolecular complexes of cucurbiturils and the effect of homogeneous equilibria and electron transfer of the guest","abstract":"\"From a practical perspective, host-guest complexes are vehicles for understanding and using supramolecular interactions for purposeful function in sensors, molecular machines and switches, while from a fundamental perspective they may lead to novel supramolecular protection schemes in basic organic reactions. This dissertation examines the interactions of cucurbiturils as barrel-shaped hosts, exhibiting a hydrophobic cavity, with substituted benzoylpyrydinium, phenypyrylium, and diazaanthraquinonediium cations as guests. In water, N-methyl-4-(p-substituted benzoyl)pyridinium cations exist in equilibrium with their hydrated forms (gem-diols), whose concentrations depend on the para substituent. In the presence of cucurbit7uril (CB[7]), the benzoyl group shows a preference for the CB[7] cavity, and the ketone to gem-diol equilibrium is shifted toward the keto form, meaning that the stabilization through hydrophobic interactions of the benzoyl group in the CB[7] cavity exceeds the hydrogen bonding stabilization of the gem-diols in the aqueous environment. In an aprotic polar solvent such as dimethylsulfoxide, 4-benzoylpyridinium cations undergo heterogeneous electron transfer simultaneously from both their free state as well as their complexes with CB[7]. In the same line of work, N,N'-dimethyl-2,6-diaza-9,10-anthraquinonediium dication in water not only exists in equilibrium with its gem-diol but also forms aggregates which cause line-broadening in ¹H NMR. At low pH (<1), the aggregates break up and the equilibrium is shifted exclusively toward the quinone form. In the presence of CB[7], the quinone form undergoes inclusion with CB[7] by slow exchange in both water and aqueous acid. Both free and CB[7]-intercalated quinone forms are observed by ¹H NMR. To gain more insight on the intercalation of monocationic guests in the cucurbituril cavity not only as a function of their hydrophobic properties but also in terms of their shape, size and the size of the cavity, 4-phenylpyrylium cation (Pylm) was chosen as a guest and both CB[7] and CB[8] as hosts. The size and shape of the guest was modified by 2,6-substitution (Me, iPr, Ph, t-Bu). In water, 2,6-disubsituted-Pylm form dimers, but they enter as such only in CB[8]. All guests insert their 4-phenyl groups in either cavity, except (iPr-Pylm)₂@CB[8] where iPr-groups are inserted. Stereochemistry is interpreted by an interplay of size and hydrophobicity of pyrylium substituents, solvation effects, and size and flexibility of the hosts\"--Abstract, page iv.","abstract_html":"&quot;From a practical perspective, host-guest complexes are vehicles for understanding and using supramolecular interactions for purposeful function in sensors, molecular machines and switches, while from a fundamental perspective they may lead to novel supramolecular protection schemes in basic organic reactions. This dissertation examines the interactions of cucurbiturils as barrel-shaped hosts, exhibiting a hydrophobic cavity, with substituted benzoylpyrydinium, phenypyrylium, and diazaanthraquinonediium cations as guests. In water, N-methyl-4-(p-substituted benzoyl)pyridinium cations exist in equilibrium with their hydrated forms (gem-diols), whose concentrations depend on the para substituent. In the presence of cucurbit7uril (CB[7]), the benzoyl group shows a preference for the CB[7] cavity, and the ketone to gem-diol equilibrium is shifted toward the keto form, meaning that the stabilization through hydrophobic interactions of the benzoyl group in the CB[7] cavity exceeds the hydrogen bonding stabilization of the gem-diols in the aqueous environment. In an aprotic polar solvent such as dimethylsulfoxide, 4-benzoylpyridinium cations undergo heterogeneous electron transfer simultaneously from both their free state as well as their complexes with CB[7]. In the same line of work, N,N&#x27;-dimethyl-2,6-diaza-9,10-anthraquinonediium dication in water not only exists in equilibrium with its gem-diol but also forms aggregates which cause line-broadening in ¹H NMR. At low pH (&lt;1), the aggregates break up and the equilibrium is shifted exclusively toward the quinone form. In the presence of CB[7], the quinone form undergoes inclusion with CB[7] by slow exchange in both water and aqueous acid. Both free and CB[7]-intercalated quinone forms are observed by ¹H NMR. To gain more insight on the intercalation of monocationic guests in the cucurbituril cavity not only as a function of their hydrophobic properties but also in terms of their shape, size and the size of the cavity, 4-phenylpyrylium cation (Pylm) was chosen as a guest and both CB[7] and CB[8] as hosts. The size and shape of the guest was modified by 2,6-substitution (Me, iPr, Ph, t-Bu). In water, 2,6-disubsituted-Pylm form dimers, but they enter as such only in CB[8]. All guests insert their 4-phenyl groups in either cavity, except (iPr-Pylm)₂@CB[8] where iPr-groups are inserted. Stereochemistry is interpreted by an interplay of size and hydrophobicity of pyrylium substituents, solvation effects, and size and flexibility of the hosts&quot;--Abstract, page iv.","abstract_has_math":false,"creators":["Thangavel, Arumugam"],"institution":"Missouri University of Science and Technology","degree_name":"Ph. D. in Chemistry","degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2016,"date_issued":"2016-02-10T08:00:00Z","date_published":"2016-02-10T08:00:00Z","updated_at":"2026-07-24T03:19:21Z","subjects":["Cucurbiturils","Chemistry"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsmine.mst.edu/doctoral_dissertations/2097","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Thangavel, Arumugam"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2016-02-10T08:00:00Z"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation - Open Access"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph. D. in Chemistry"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Missouri University of Science and Technology"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Cucurbiturils","Chemistry"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsmine.mst.edu/doctoral_dissertations/2097"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["\"From a practical perspective, host-guest complexes are vehicles for understanding and using supramolecular interactions for purposeful function in sensors, molecular machines and switches, while from a fundamental perspective they may lead to novel supramolecular protection schemes in basic organic reactions. This dissertation examines the interactions of cucurbiturils as barrel-shaped hosts, exhibiting a hydrophobic cavity, with substituted benzoylpyrydinium, phenypyrylium, and diazaanthraquinonediium cations as guests. In water, N-methyl-4-(p-substituted benzoyl)pyridinium cations exist in equilibrium with their hydrated forms (gem-diols), whose concentrations depend on the para substituent. In the presence of cucurbit7uril (CB[7]), the benzoyl group shows a preference for the CB[7] cavity, and the ketone to gem-diol equilibrium is shifted toward the keto form, meaning that the stabilization through hydrophobic interactions of the benzoyl group in the CB[7] cavity exceeds the hydrogen bonding stabilization of the gem-diols in the aqueous environment. In an aprotic polar solvent such as dimethylsulfoxide, 4-benzoylpyridinium cations undergo heterogeneous electron transfer simultaneously from both their free state as well as their complexes with CB[7]. In the same line of work, N,N'-dimethyl-2,6-diaza-9,10-anthraquinonediium dication in water not only exists in equilibrium with its gem-diol but also forms aggregates which cause line-broadening in ¹H NMR. At low pH (<1), the aggregates break up and the equilibrium is shifted exclusively toward the quinone form. In the presence of CB[7], the quinone form undergoes inclusion with CB[7] by slow exchange in both water and aqueous acid. Both free and CB[7]-intercalated quinone forms are observed by ¹H NMR. To gain more insight on the intercalation of monocationic guests in the cucurbituril cavity not only as a function of their hydrophobic properties but also in terms of their shape, size and the size of the cavity, 4-phenylpyrylium cation (Pylm) was chosen as a guest and both CB[7] and CB[8] as hosts. The size and shape of the guest was modified by 2,6-substitution (Me, iPr, Ph, t-Bu). In water, 2,6-disubsituted-Pylm form dimers, but they enter as such only in CB[8]. All guests insert their 4-phenyl groups in either cavity, except (iPr-Pylm)₂@CB[8] where iPr-groups are inserted. Stereochemistry is interpreted by an interplay of size and hydrophobicity of pyrylium substituents, solvation effects, and size and flexibility of the hosts\"--Abstract, page iv."]},{"key":"dc:title","label":"Title","values":["The stereochemistry of selected supramolecular complexes of cucurbiturils and the effect of homogeneous equilibria and electron transfer of the guest"]}]}],"canonical_facts":{"dc:creator":["Thangavel, Arumugam"],"dc:date.available":["2016-02-10T08:00:00Z"],"dc:description.abstract":["\"From a practical perspective, host-guest complexes are vehicles for understanding and using supramolecular interactions for purposeful function in sensors, molecular machines and switches, while from a fundamental perspective they may lead to novel supramolecular protection schemes in basic organic reactions. This dissertation examines the interactions of cucurbiturils as barrel-shaped hosts, exhibiting a hydrophobic cavity, with substituted benzoylpyrydinium, phenypyrylium, and diazaanthraquinonediium cations as guests. In water, N-methyl-4-(p-substituted benzoyl)pyridinium cations exist in equilibrium with their hydrated forms (gem-diols), whose concentrations depend on the para substituent. In the presence of cucurbit7uril (CB[7]), the benzoyl group shows a preference for the CB[7] cavity, and the ketone to gem-diol equilibrium is shifted toward the keto form, meaning that the stabilization through hydrophobic interactions of the benzoyl group in the CB[7] cavity exceeds the hydrogen bonding stabilization of the gem-diols in the aqueous environment. In an aprotic polar solvent such as dimethylsulfoxide, 4-benzoylpyridinium cations undergo heterogeneous electron transfer simultaneously from both their free state as well as their complexes with CB[7]. In the same line of work, N,N'-dimethyl-2,6-diaza-9,10-anthraquinonediium dication in water not only exists in equilibrium with its gem-diol but also forms aggregates which cause line-broadening in ¹H NMR. At low pH (<1), the aggregates break up and the equilibrium is shifted exclusively toward the quinone form. In the presence of CB[7], the quinone form undergoes inclusion with CB[7] by slow exchange in both water and aqueous acid. Both free and CB[7]-intercalated quinone forms are observed by ¹H NMR. To gain more insight on the intercalation of monocationic guests in the cucurbituril cavity not only as a function of their hydrophobic properties but also in terms of their shape, size and the size of the cavity, 4-phenylpyrylium cation (Pylm) was chosen as a guest and both CB[7] and CB[8] as hosts. The size and shape of the guest was modified by 2,6-substitution (Me, iPr, Ph, t-Bu). In water, 2,6-disubsituted-Pylm form dimers, but they enter as such only in CB[8]. All guests insert their 4-phenyl groups in either cavity, except (iPr-Pylm)₂@CB[8] where iPr-groups are inserted. Stereochemistry is interpreted by an interplay of size and hydrophobicity of pyrylium substituents, solvation effects, and size and flexibility of the hosts\"--Abstract, page iv."],"dc:identifier":["https://scholarsmine.mst.edu/doctoral_dissertations/2097"],"dc:subject":["Cucurbiturils","Chemistry"],"dc:title":["The stereochemistry of selected supramolecular complexes of cucurbiturils and the effect of homogeneous equilibria and electron transfer of the guest"],"dc:type":["Dissertation - Open Access"],"thesis:degree_name":["Ph. D. in Chemistry"],"thesis:institution_name":["Missouri University of Science and Technology"]},"updated_at":"2026-07-24T03:19:21Z"}