{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/20110"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/20110","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Dynamics and mechanism of spin-state interconversion in transition metal complexes. (Volumes I and II)","abstract":"The kinetics of the $\\Delta$S = 2 spin-state interconversion in d$\\sp6$ transition metal complexes are examined. A series of compounds having a polypyridyl-based ligand framework are described which allow for systematic modification of molecular geometry. A nanosecond time-resolved laser spectrometer was constructed to measure the kinetics of spin-state interconversion as a function of temperature in an attempt to probe the molecular mechanism of $\\rm\\sp5T\\sb2$ $\\to$ $\\rm\\sp1A\\sb1$ relaxation in Fe$\\sp{\\rm II}$ complexes. The data establish an empirical correlation between the flexibility of the ligand framework and the activation energy for the process, suggesting a smaller barrier to spin-state interconversion for those molecules having a greater tendency to distort along torsional coordinates. In addition, a correlation is noted that suggests conformational preferences of the ligand structure may influence the intrinsic rate of spin-state interconversion by modulating the extent to which a system proceeds along the reaction coordinate. The importance of torsional modes in controlling the kinetics of $\\rm\\sp5T\\sb2$ $\\to$ $\\rm\\sp1A\\sb1$ relaxation is further supported by theoretical analyses. Fitting of variable-temperature kinetic data to classical, semi-classical, and quantum-mechanical theories of electron transfer give identical results, indicating that the quantum nature of the vibrational mode coupled to spin-state interconversion does not manifest itself in the 160-300 K range. This observation is inconsistent with coupling to a metal-ligand stretching mode and strongly suggests the involvement of low-frequency mode(s) $($10$\\sp{12}$ s$\\sp{-1}$ is interpreted in terms of direct $\\rm\\sp1MLCT$ $\\to$ $\\rm\\sp5T\\sb2$ conversion from the Franck-Condon state following excitation. The excited-state dynamics of several Co$\\sp{\\rm III}$ complexes are also discussed. The biphasic kinetics observed are attributed to decay from singlet and quintet ligand-field states, suggesting a $\\sp1$LMCT state lifetime of $<$1 ps and internal conversion rates that are kinetically competitive with intersystem crossing.","abstract_html":"The kinetics of the $\\Delta$S = 2 spin-state interconversion in d$\\sp6$ transition metal complexes are examined. A series of compounds having a polypyridyl-based ligand framework are described which allow for systematic modification of molecular geometry. A nanosecond time-resolved laser spectrometer was constructed to measure the kinetics of spin-state interconversion as a function of temperature in an attempt to probe the molecular mechanism of $\\rm\\sp5T\\sb2$ $\\to$ $\\rm\\sp1A\\sb1$ relaxation in Fe$\\sp{\\rm II}$ complexes. The data establish an empirical correlation between the flexibility of the ligand framework and the activation energy for the process, suggesting a smaller barrier to spin-state interconversion for those molecules having a greater tendency to distort along torsional coordinates. In addition, a correlation is noted that suggests conformational preferences of the ligand structure may influence the intrinsic rate of spin-state interconversion by modulating the extent to which a system proceeds along the reaction coordinate. The importance of torsional modes in controlling the kinetics of $\\rm\\sp5T\\sb2$ $\\to$ $\\rm\\sp1A\\sb1$ relaxation is further supported by theoretical analyses. Fitting of variable-temperature kinetic data to classical, semi-classical, and quantum-mechanical theories of electron transfer give identical results, indicating that the quantum nature of the vibrational mode coupled to spin-state interconversion does not manifest itself in the 160-300 K range. This observation is inconsistent with coupling to a metal-ligand stretching mode and strongly suggests the involvement of low-frequency mode(s) $($10$\\sp{12}$ s$\\sp{-1}$ is interpreted in terms of direct $\\rm\\sp1MLCT$ $\\to$ $\\rm\\sp5T\\sb2$ conversion from the Franck-Condon state following excitation. The excited-state dynamics of several Co$\\sp{\\rm III}$ complexes are also discussed. The biphasic kinetics observed are attributed to decay from singlet and quintet ligand-field states, suggesting a $\\sp1$LMCT state lifetime of $&lt;$1 ps and internal conversion rates that are kinetically competitive with intersystem crossing.","abstract_has_math":true,"creators":["McCusker, James Kenneth"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":["Brown, Theodore L."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T12:29:07Z","date_published":"2011-05-07T12:29:07Z","updated_at":"2026-07-22T22:25:15Z","subjects":["Chemistry, Inorganic","Chemistry, Physical"],"languages":["eng"],"rights":["Copyright 1992 McCusker, James Kenneth"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9305618","(UMI)AAI9305618"],"render_values":[{"text":"AAI9305618","href":null,"code":true},{"text":"(UMI)AAI9305618","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/20110","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Brown, Theodore L."]},{"key":"dc:creator","label":"Author","values":["McCusker, James Kenneth"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T12:29:07Z","10000-01-01","1992"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chemistry, Inorganic","Chemistry, Physical"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1992 McCusker, James Kenneth"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9305618","(UMI)AAI9305618","http://hdl.handle.net/2142/20110"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The kinetics of the $\\Delta$S = 2 spin-state interconversion in d$\\sp6$ transition metal complexes are examined. A series of compounds having a polypyridyl-based ligand framework are described which allow for systematic modification of molecular geometry. A nanosecond time-resolved laser spectrometer was constructed to measure the kinetics of spin-state interconversion as a function of temperature in an attempt to probe the molecular mechanism of $\\rm\\sp5T\\sb2$ $\\to$ $\\rm\\sp1A\\sb1$ relaxation in Fe$\\sp{\\rm II}$ complexes. The data establish an empirical correlation between the flexibility of the ligand framework and the activation energy for the process, suggesting a smaller barrier to spin-state interconversion for those molecules having a greater tendency to distort along torsional coordinates. In addition, a correlation is noted that suggests conformational preferences of the ligand structure may influence the intrinsic rate of spin-state interconversion by modulating the extent to which a system proceeds along the reaction coordinate. The importance of torsional modes in controlling the kinetics of $\\rm\\sp5T\\sb2$ $\\to$ $\\rm\\sp1A\\sb1$ relaxation is further supported by theoretical analyses. Fitting of variable-temperature kinetic data to classical, semi-classical, and quantum-mechanical theories of electron transfer give identical results, indicating that the quantum nature of the vibrational mode coupled to spin-state interconversion does not manifest itself in the 160-300 K range. This observation is inconsistent with coupling to a metal-ligand stretching mode and strongly suggests the involvement of low-frequency mode(s) $($10$\\sp{12}$ s$\\sp{-1}$ is interpreted in terms of direct $\\rm\\sp1MLCT$ $\\to$ $\\rm\\sp5T\\sb2$ conversion from the Franck-Condon state following excitation. The excited-state dynamics of several Co$\\sp{\\rm III}$ complexes are also discussed. The biphasic kinetics observed are attributed to decay from singlet and quintet ligand-field states, suggesting a $\\sp1$LMCT state lifetime of $<$1 ps and internal conversion rates that are kinetically competitive with intersystem crossing.","Made available in DSpace on 2011-05-07T12:29:07Z (GMT). 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(Volumes I and II)"]}]}],"canonical_facts":{"dc:contributor":["Brown, Theodore L."],"dc:creator":["McCusker, James Kenneth"],"dc:date":["2011-05-07T12:29:07Z","10000-01-01","1992"],"dc:description":["The kinetics of the $\\Delta$S = 2 spin-state interconversion in d$\\sp6$ transition metal complexes are examined. A series of compounds having a polypyridyl-based ligand framework are described which allow for systematic modification of molecular geometry. A nanosecond time-resolved laser spectrometer was constructed to measure the kinetics of spin-state interconversion as a function of temperature in an attempt to probe the molecular mechanism of $\\rm\\sp5T\\sb2$ $\\to$ $\\rm\\sp1A\\sb1$ relaxation in Fe$\\sp{\\rm II}$ complexes. The data establish an empirical correlation between the flexibility of the ligand framework and the activation energy for the process, suggesting a smaller barrier to spin-state interconversion for those molecules having a greater tendency to distort along torsional coordinates. In addition, a correlation is noted that suggests conformational preferences of the ligand structure may influence the intrinsic rate of spin-state interconversion by modulating the extent to which a system proceeds along the reaction coordinate. The importance of torsional modes in controlling the kinetics of $\\rm\\sp5T\\sb2$ $\\to$ $\\rm\\sp1A\\sb1$ relaxation is further supported by theoretical analyses. Fitting of variable-temperature kinetic data to classical, semi-classical, and quantum-mechanical theories of electron transfer give identical results, indicating that the quantum nature of the vibrational mode coupled to spin-state interconversion does not manifest itself in the 160-300 K range. This observation is inconsistent with coupling to a metal-ligand stretching mode and strongly suggests the involvement of low-frequency mode(s) $($10$\\sp{12}$ s$\\sp{-1}$ is interpreted in terms of direct $\\rm\\sp1MLCT$ $\\to$ $\\rm\\sp5T\\sb2$ conversion from the Franck-Condon state following excitation. The excited-state dynamics of several Co$\\sp{\\rm III}$ complexes are also discussed. The biphasic kinetics observed are attributed to decay from singlet and quintet ligand-field states, suggesting a $\\sp1$LMCT state lifetime of $<$1 ps and internal conversion rates that are kinetically competitive with intersystem crossing.","Made available in DSpace on 2011-05-07T12:29:07Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9305618.pdf: 18087581 bytes, checksum: 035668f3580715186a4907feabc19b50 (MD5) Previous issue date: 1992","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:41:38Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:18:02-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"],"dc:identifier":["AAI9305618","(UMI)AAI9305618","http://hdl.handle.net/2142/20110"],"dc:language":["eng"],"dc:rights":["Copyright 1992 McCusker, James Kenneth"],"dc:subject":["Chemistry, Inorganic","Chemistry, Physical"],"dc:title":["Dynamics and mechanism of spin-state interconversion in transition metal complexes. (Volumes I and II)"],"dc:type":["text"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:15Z"}