{"id":{"repo_id":"maryland","oai_identifier":"oai:drum.lib.umd.edu:1903/3690"},"canonical_url":"https://search.dev.ndltd.org/etd/maryland/oai:drum.lib.umd.edu:1903/3690","repository":{"repo_id":"maryland","name":"University of Maryland","base_url":"https://api.drum.lib.umd.edu/server/oai/request"},"display":{"title":"Photolytic Studies of Aryl and Heteroaryl Nitrenium Ions: Laser Flash Photolysis Studies","abstract":"The objective of the thesis was to understand the chemical and kinetic behavior of arylnitrenium ions and a heteroaromatic nitrenium ion through photolytic studies. N-(4,4'-dichlorodiphenyl) nitrenium ion and N-(4,4'-dibromodiphenyl) nitrenium ion are the halogenated counterparts of diphenylnitrenium ions and are generated photochemically from their respective N-(4,4'-dihalogenated diphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate salts. The halogenated diarylnitrenium ions are ground state singlets that live for more than 1 x 105 ns in acetonitrile. In the absence of nucleophiles, these ions decay to form a dimerized hydrazine. These ions react with nucleophiles such as water and alcohol at a rate constant of 104 - 105M-1s-1 and at diffusion limit with chlorides. With arenes, these ions react via electron transfer mechanism and nucleophilic addition process. The rate constants for the electron transfer mechanisms are between 105 - 109 M-1 s-1 and depend on the Eox of the arenes. Arenes with Eox above 1.78 V showed no reactivity towards the ion. Unlike other diarylnitrenium ions, the halogenated diarylnitrenium ions react with hydrogen atom donors via a hydrogen atom transfer mechanism. The triplet behavior of these ions is attributed to singlet-triplet intersystem crossing facilitated by the lower singlet-triplet energy gap. Therefore, it has been concluded that substituting halogens in diphenylnitrenium ion lowers the singlet-triplet energy gap and increases the lifetime of these ions. (N-Methyl-N-4-biphenylyl) nitrenium ion generated by photolysis was reacted with amino acids and proteins to determine their reactivity with these ions. Eight amino acids were observed to react with the ion at a rate constant of 107 - 109 M-1 s-1. The rate constants depend on the nucleophilicity of the side chains of the amino acids. In addition, this ion also reacts rapidly with proteins with a rate constant of 108 M-1 s-1, comparable to their reactions with ss-DNA. Investigations on generating the quinoline N-oxide nitrenium ions showed that the transient species from the photolysis of 4-azidoquinoline N-oxide (4-AzQO) shows more characteristics of a nitrenium ion. The formation of 4-aminoquinoline N-oxide upon photolysis of 4-AzQO in acetonitrile with 10% sulphuric acid and the electron transfer reactions observed with arenes, indicate that the transient species generated could be a heteroaromatic nitrenium ion. However, more experiments are needed to confirm the assignment.","abstract_html":"The objective of the thesis was to understand the chemical and kinetic behavior of arylnitrenium ions and a heteroaromatic nitrenium ion through photolytic studies. <em>N</em>-(4,4'-dichlorodiphenyl) nitrenium ion and <em>N</em>-(4,4'-dibromodiphenyl) nitrenium ion are the halogenated counterparts of diphenylnitrenium ions and are generated photochemically from their respective <em>N</em>-(4,4'-dihalogenated diphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate salts. The halogenated diarylnitrenium ions are ground state singlets that live for more than 1 x 10<sup>5</sup> ns in acetonitrile. In the absence of nucleophiles, these ions decay to form a dimerized hydrazine. These ions react with nucleophiles such as water and alcohol at a rate constant of 10<sup>4</sup> - 10<sup>5</sup>M<sup>-1</sup>s<sup>-1</sup> and at diffusion limit with chlorides. With arenes, these ions react via electron transfer mechanism and nucleophilic addition process. The rate constants for the electron transfer mechanisms are between 10<sup>5</sup> - 10<sup>9</sup> M<sup>-1</sup> s<sup>-1</sup> and depend on the Eox of the arenes. Arenes with Eox above 1.78 V showed no reactivity towards the ion. Unlike other diarylnitrenium ions, the halogenated diarylnitrenium ions react with hydrogen atom donors via a hydrogen atom transfer mechanism. The triplet behavior of these ions is attributed to singlet-triplet intersystem crossing facilitated by the lower singlet-triplet energy gap. Therefore, it has been concluded that substituting halogens in diphenylnitrenium ion lowers the singlet-triplet energy gap and increases the lifetime of these ions. (<em>N</em>-Methyl-<em>N</em>-4-biphenylyl) nitrenium ion generated by photolysis was reacted with amino acids and proteins to determine their reactivity with these ions. Eight amino acids were observed to react with the ion at a rate constant of 10<sup>7</sup> - 10<sup>9</sup> M<sup>-1</sup> s<sup>-1</sup>. The rate constants depend on the nucleophilicity of the side chains of the amino acids. In addition, this ion also reacts rapidly with proteins with a rate constant of 10<sup>8</sup> M<sup>-1</sup> s<sup>-1</sup>, comparable to their reactions with ss-DNA. Investigations on generating the quinoline <em>N</em>-oxide nitrenium ions showed that the transient species from the photolysis of 4-azidoquinoline <em>N</em>-oxide (4-AzQO) shows more characteristics of a nitrenium ion. The formation of 4-aminoquinoline <em>N</em>-oxide upon photolysis of 4-AzQO in acetonitrile with 10% sulphuric acid and the electron transfer reactions observed with arenes, indicate that the transient species generated could be a heteroaromatic nitrenium ion. However, more experiments are needed to confirm the assignment.","abstract_has_math":false,"creators":["Thomas, Selina Ivan"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Chemistry","school":null,"contributors":[],"advisors":["Falvey, Daniel E"],"committee_chairs":[],"committee_members":[],"year":2006,"date_issued":"2006-05-07","date_published":"2006-05-07","updated_at":"2026-07-24T03:02:31Z","subjects":[],"languages":["en_US"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1903/3690","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Falvey, Daniel E"]},{"key":"dc:contributor.department","label":"Department","values":["Chemistry"]},{"key":"dc:creator","label":"Author","values":["Thomas, Selina Ivan"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2006-09-12T05:31:19Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2006-09-12T05:31:19Z"]},{"key":"dc:date.issued","label":"Date","values":["2006-05-07"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en_US"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1903/3690"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The objective of the thesis was to understand the chemical and kinetic behavior of arylnitrenium ions and a heteroaromatic nitrenium ion through photolytic studies. N-(4,4'-dichlorodiphenyl) nitrenium ion and N-(4,4'-dibromodiphenyl) nitrenium ion are the halogenated counterparts of diphenylnitrenium ions and are generated photochemically from their respective N-(4,4'-dihalogenated diphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate salts. The halogenated diarylnitrenium ions are ground state singlets that live for more than 1 x 105 ns in acetonitrile. In the absence of nucleophiles, these ions decay to form a dimerized hydrazine. These ions react with nucleophiles such as water and alcohol at a rate constant of 104 - 105M-1s-1 and at diffusion limit with chlorides. With arenes, these ions react via electron transfer mechanism and nucleophilic addition process. The rate constants for the electron transfer mechanisms are between 105 - 109 M-1 s-1 and depend on the Eox of the arenes. Arenes with Eox above 1.78 V showed no reactivity towards the ion. Unlike other diarylnitrenium ions, the halogenated diarylnitrenium ions react with hydrogen atom donors via a hydrogen atom transfer mechanism. The triplet behavior of these ions is attributed to singlet-triplet intersystem crossing facilitated by the lower singlet-triplet energy gap. Therefore, it has been concluded that substituting halogens in diphenylnitrenium ion lowers the singlet-triplet energy gap and increases the lifetime of these ions. (N-Methyl-N-4-biphenylyl) nitrenium ion generated by photolysis was reacted with amino acids and proteins to determine their reactivity with these ions. Eight amino acids were observed to react with the ion at a rate constant of 107 - 109 M-1 s-1. The rate constants depend on the nucleophilicity of the side chains of the amino acids. In addition, this ion also reacts rapidly with proteins with a rate constant of 108 M-1 s-1, comparable to their reactions with ss-DNA. Investigations on generating the quinoline N-oxide nitrenium ions showed that the transient species from the photolysis of 4-azidoquinoline N-oxide (4-AzQO) shows more characteristics of a nitrenium ion. The formation of 4-aminoquinoline N-oxide upon photolysis of 4-AzQO in acetonitrile with 10% sulphuric acid and the electron transfer reactions observed with arenes, indicate that the transient species generated could be a heteroaromatic nitrenium ion. However, more experiments are needed to confirm the assignment."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Photolytic Studies of Aryl and Heteroaryl Nitrenium Ions: Laser Flash Photolysis Studies"]}]}],"canonical_facts":{"dc:contributor.advisor":["Falvey, Daniel E"],"dc:contributor.department":["Chemistry"],"dc:creator":["Thomas, Selina Ivan"],"dc:date.accessioned":["2006-09-12T05:31:19Z"],"dc:date.available":["2006-09-12T05:31:19Z"],"dc:date.issued":["2006-05-07"],"dc:description.abstract":["The objective of the thesis was to understand the chemical and kinetic behavior of arylnitrenium ions and a heteroaromatic nitrenium ion through photolytic studies. N-(4,4'-dichlorodiphenyl) nitrenium ion and N-(4,4'-dibromodiphenyl) nitrenium ion are the halogenated counterparts of diphenylnitrenium ions and are generated photochemically from their respective N-(4,4'-dihalogenated diphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate salts. The halogenated diarylnitrenium ions are ground state singlets that live for more than 1 x 105 ns in acetonitrile. In the absence of nucleophiles, these ions decay to form a dimerized hydrazine. These ions react with nucleophiles such as water and alcohol at a rate constant of 104 - 105M-1s-1 and at diffusion limit with chlorides. With arenes, these ions react via electron transfer mechanism and nucleophilic addition process. The rate constants for the electron transfer mechanisms are between 105 - 109 M-1 s-1 and depend on the Eox of the arenes. Arenes with Eox above 1.78 V showed no reactivity towards the ion. Unlike other diarylnitrenium ions, the halogenated diarylnitrenium ions react with hydrogen atom donors via a hydrogen atom transfer mechanism. The triplet behavior of these ions is attributed to singlet-triplet intersystem crossing facilitated by the lower singlet-triplet energy gap. Therefore, it has been concluded that substituting halogens in diphenylnitrenium ion lowers the singlet-triplet energy gap and increases the lifetime of these ions. (N-Methyl-N-4-biphenylyl) nitrenium ion generated by photolysis was reacted with amino acids and proteins to determine their reactivity with these ions. Eight amino acids were observed to react with the ion at a rate constant of 107 - 109 M-1 s-1. The rate constants depend on the nucleophilicity of the side chains of the amino acids. In addition, this ion also reacts rapidly with proteins with a rate constant of 108 M-1 s-1, comparable to their reactions with ss-DNA. Investigations on generating the quinoline N-oxide nitrenium ions showed that the transient species from the photolysis of 4-azidoquinoline N-oxide (4-AzQO) shows more characteristics of a nitrenium ion. The formation of 4-aminoquinoline N-oxide upon photolysis of 4-AzQO in acetonitrile with 10% sulphuric acid and the electron transfer reactions observed with arenes, indicate that the transient species generated could be a heteroaromatic nitrenium ion. However, more experiments are needed to confirm the assignment."],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["http://hdl.handle.net/1903/3690"],"dc:language.iso":["en_US"],"dc:title":["Photolytic Studies of Aryl and Heteroaryl Nitrenium Ions: Laser Flash Photolysis Studies"],"dc:type":["Dissertation"]},"updated_at":"2026-07-24T03:02:31Z"}