{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/109507"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/109507","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Probing the reaction coordinate of photoinduced spin-crossover with femtosecond M-edge XANES","abstract":"Photoinduced spin-crossover is studied using femtosecond M-edge XANES with a tabletop instrument based on a high-harmonic generation source. This technique probes the oxidation state, spin state and ligand field of the metal center with sub-50 fs time resolution, making it a powerful tool to study the ultrafast photophysics of transition metal complexes. Experimental spectra are interpreted with ligand field multiplet (LFM) simulations to extract information about the electronic structure of the metal center. General trends in the spectra of d0-d9 octahedral complexes with changing ligand field strengths are first presented to demonstrate the information contained in each M-edge spectrum. This framework is then used to study the ultrafast dynamics of a series of iron(II) complexes with varying ligand geometries. Key regions in the M-edge spectra are shown to indicate the presence of singlet, triplet and quintet metal-centered states, and a triplet intermediate state is identified in the relaxation cascade in Fe(phen)32+, Fe(tpy)22+, and Fe[(4-CF3)2bpca]2. Coherent oscillations are observed as a modification of the quintet spectrum and are shown to arise from modifications of the ligand field strength of the complex. NEVPT2 calculations are employed to show how different vibrational modes imprint a unique signature in the M-edge spectra and unravel a difference between the nuclear dynamics of Fe(tpy)22+ and Fe[(4-CF3)2bpca]2. Ongoing work is shown for the photophysics of a macrocyclic Fe(II) complex which has potential to afford long-lived metal-to-ligand charge transfer lifetimes with judicious choice of the axial ligand. Ultrafast valence tautomerism in a cobalt dioxolene complex is also studied. The transient M-edge XANES spectra show the involvement of a low-spin Co(II) before ultrafast intersystem crossing. Two relaxation pathways from the vibrationally hot and cold high-spin Co(II) state are also identified. Finally, the development of a thin-film cryostat suitable for transient M-edge XANES experiments is presented. The challenges of minimizing radiative heat transfer and cooling thin-film samples are shown and the cryostat’s operation is demonstrated for the complex Fe[(H2B(pz)2]2(bpy), which undergoes both thermal and photoinduced spin-crossover.","abstract_html":"Photoinduced spin-crossover is studied using femtosecond M-edge XANES with a tabletop instrument based on a high-harmonic generation source. This technique probes the oxidation state, spin state and ligand field of the metal center with sub-50 fs time resolution, making it a powerful tool to study the ultrafast photophysics of transition metal complexes. Experimental spectra are interpreted with ligand field multiplet (LFM) simulations to extract information about the electronic structure of the metal center. General trends in the spectra of d0-d9 octahedral complexes with changing ligand field strengths are first presented to demonstrate the information contained in each M-edge spectrum. This framework is then used to study the ultrafast dynamics of a series of iron(II) complexes with varying ligand geometries. Key regions in the M-edge spectra are shown to indicate the presence of singlet, triplet and quintet metal-centered states, and a triplet intermediate state is identified in the relaxation cascade in Fe(phen)32+, Fe(tpy)22+, and Fe[(4-CF3)2bpca]2. Coherent oscillations are observed as a modification of the quintet spectrum and are shown to arise from modifications of the ligand field strength of the complex. NEVPT2 calculations are employed to show how different vibrational modes imprint a unique signature in the M-edge spectra and unravel a difference between the nuclear dynamics of Fe(tpy)22+ and Fe[(4-CF3)2bpca]2. Ongoing work is shown for the photophysics of a macrocyclic Fe(II) complex which has potential to afford long-lived metal-to-ligand charge transfer lifetimes with judicious choice of the axial ligand. Ultrafast valence tautomerism in a cobalt dioxolene complex is also studied. The transient M-edge XANES spectra show the involvement of a low-spin Co(II) before ultrafast intersystem crossing. Two relaxation pathways from the vibrationally hot and cold high-spin Co(II) state are also identified. Finally, the development of a thin-film cryostat suitable for transient M-edge XANES experiments is presented. The challenges of minimizing radiative heat transfer and cooling thin-film samples are shown and the cryostat’s operation is demonstrated for the complex Fe[(H2B(pz)2]2(bpy), which undergoes both thermal and photoinduced spin-crossover.","abstract_has_math":false,"creators":["Ash, Ryan"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":["Vura-Weis, Joshua","Eden, J G","Girolami, Gregory S","van der Veen, Renske"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-03-05T21:42:40Z","date_published":"2021-03-05T21:42:40Z","updated_at":"2026-07-22T22:24:50Z","subjects":["Physical Chemistry","M-edge XANES","Extreme Ultraviolet","Ultrafast Spectroscopy","Transition Metal Photophysics","Spin Crossover"],"languages":["en"],"rights":["Copyright 2020 Ryan Ash"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/109507","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Vura-Weis, Joshua","Eden, J G","Girolami, Gregory S","van der Veen, Renske"]},{"key":"dc:creator","label":"Author","values":["Ash, Ryan"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2021-03-05T21:42:40Z","2023-03-05T21:43:00Z","2020-11-30","2020-12"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"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":["Physical Chemistry","M-edge XANES","Extreme Ultraviolet","Ultrafast Spectroscopy","Transition Metal Photophysics","Spin Crossover"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2020 Ryan Ash"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/109507"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Photoinduced spin-crossover is studied using femtosecond M-edge XANES with a tabletop instrument based on a high-harmonic generation source. This technique probes the oxidation state, spin state and ligand field of the metal center with sub-50 fs time resolution, making it a powerful tool to study the ultrafast photophysics of transition metal complexes. Experimental spectra are interpreted with ligand field multiplet (LFM) simulations to extract information about the electronic structure of the metal center. General trends in the spectra of d0-d9 octahedral complexes with changing ligand field strengths are first presented to demonstrate the information contained in each M-edge spectrum. This framework is then used to study the ultrafast dynamics of a series of iron(II) complexes with varying ligand geometries. Key regions in the M-edge spectra are shown to indicate the presence of singlet, triplet and quintet metal-centered states, and a triplet intermediate state is identified in the relaxation cascade in Fe(phen)32+, Fe(tpy)22+, and Fe[(4-CF3)2bpca]2. Coherent oscillations are observed as a modification of the quintet spectrum and are shown to arise from modifications of the ligand field strength of the complex. NEVPT2 calculations are employed to show how different vibrational modes imprint a unique signature in the M-edge spectra and unravel a difference between the nuclear dynamics of Fe(tpy)22+ and Fe[(4-CF3)2bpca]2. Ongoing work is shown for the photophysics of a macrocyclic Fe(II) complex which has potential to afford long-lived metal-to-ligand charge transfer lifetimes with judicious choice of the axial ligand. Ultrafast valence tautomerism in a cobalt dioxolene complex is also studied. The transient M-edge XANES spectra show the involvement of a low-spin Co(II) before ultrafast intersystem crossing. Two relaxation pathways from the vibrationally hot and cold high-spin Co(II) state are also identified. Finally, the development of a thin-film cryostat suitable for transient M-edge XANES experiments is presented. The challenges of minimizing radiative heat transfer and cooling thin-film samples are shown and the cryostat’s operation is demonstrated for the complex Fe[(H2B(pz)2]2(bpy), which undergoes both thermal and photoinduced spin-crossover.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-12-01","The student, Ryan Ash, accepted the attached license on 2020-11-24 at 16:07.","The student, Ryan Ash, submitted this Dissertation for approval on 2020-11-24 at 16:14.","This Dissertation was approved for publication on 2020-11-30 at 16:35.","DSpace SAF Submission Ingestion Package generated from Vireo submission #15946 on 2021-03-04 at 16:19:50","Made available in DSpace on 2021-03-05T21:42:40Z (GMT). No. of bitstreams: 3 ASH-DISSERTATION-2020.pdf: 10043608 bytes, checksum: e9d784e40f0c182e2d18ea8522bd7339 (MD5) LICENSE.txt: 4205 bytes, checksum: d9a3e8590e9bdf006cb1a403492f4f45 (MD5) j chem phys copyright.pdf: 110564 bytes, checksum: 858527c091016d6541aa7473efdcb619 (MD5) Previous issue date: 2020-11-30","Embargo set by: Seth Robbins for item 117212 Lift date: 2023-03-05T21:43:00Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Probing the reaction coordinate of photoinduced spin-crossover with femtosecond M-edge XANES"]}]}],"canonical_facts":{"dc:contributor":["Vura-Weis, Joshua","Eden, J G","Girolami, Gregory S","van der Veen, Renske"],"dc:creator":["Ash, Ryan"],"dc:date":["2021-03-05T21:42:40Z","2023-03-05T21:43:00Z","2020-11-30","2020-12"],"dc:description":["Photoinduced spin-crossover is studied using femtosecond M-edge XANES with a tabletop instrument based on a high-harmonic generation source. This technique probes the oxidation state, spin state and ligand field of the metal center with sub-50 fs time resolution, making it a powerful tool to study the ultrafast photophysics of transition metal complexes. Experimental spectra are interpreted with ligand field multiplet (LFM) simulations to extract information about the electronic structure of the metal center. General trends in the spectra of d0-d9 octahedral complexes with changing ligand field strengths are first presented to demonstrate the information contained in each M-edge spectrum. This framework is then used to study the ultrafast dynamics of a series of iron(II) complexes with varying ligand geometries. Key regions in the M-edge spectra are shown to indicate the presence of singlet, triplet and quintet metal-centered states, and a triplet intermediate state is identified in the relaxation cascade in Fe(phen)32+, Fe(tpy)22+, and Fe[(4-CF3)2bpca]2. Coherent oscillations are observed as a modification of the quintet spectrum and are shown to arise from modifications of the ligand field strength of the complex. NEVPT2 calculations are employed to show how different vibrational modes imprint a unique signature in the M-edge spectra and unravel a difference between the nuclear dynamics of Fe(tpy)22+ and Fe[(4-CF3)2bpca]2. Ongoing work is shown for the photophysics of a macrocyclic Fe(II) complex which has potential to afford long-lived metal-to-ligand charge transfer lifetimes with judicious choice of the axial ligand. Ultrafast valence tautomerism in a cobalt dioxolene complex is also studied. The transient M-edge XANES spectra show the involvement of a low-spin Co(II) before ultrafast intersystem crossing. Two relaxation pathways from the vibrationally hot and cold high-spin Co(II) state are also identified. Finally, the development of a thin-film cryostat suitable for transient M-edge XANES experiments is presented. The challenges of minimizing radiative heat transfer and cooling thin-film samples are shown and the cryostat’s operation is demonstrated for the complex Fe[(H2B(pz)2]2(bpy), which undergoes both thermal and photoinduced spin-crossover.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-12-01","The student, Ryan Ash, accepted the attached license on 2020-11-24 at 16:07.","The student, Ryan Ash, submitted this Dissertation for approval on 2020-11-24 at 16:14.","This Dissertation was approved for publication on 2020-11-30 at 16:35.","DSpace SAF Submission Ingestion Package generated from Vireo submission #15946 on 2021-03-04 at 16:19:50","Made available in DSpace on 2021-03-05T21:42:40Z (GMT). No. of bitstreams: 3 ASH-DISSERTATION-2020.pdf: 10043608 bytes, checksum: e9d784e40f0c182e2d18ea8522bd7339 (MD5) LICENSE.txt: 4205 bytes, checksum: d9a3e8590e9bdf006cb1a403492f4f45 (MD5) j chem phys copyright.pdf: 110564 bytes, checksum: 858527c091016d6541aa7473efdcb619 (MD5) Previous issue date: 2020-11-30","Embargo set by: Seth Robbins for item 117212 Lift date: 2023-03-05T21:43:00Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/109507"],"dc:language":["en"],"dc:rights":["Copyright 2020 Ryan Ash"],"dc:subject":["Physical Chemistry","M-edge XANES","Extreme Ultraviolet","Ultrafast Spectroscopy","Transition Metal Photophysics","Spin Crossover"],"dc:title":["Probing the reaction coordinate of photoinduced spin-crossover with femtosecond M-edge XANES"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:50Z"}