2026-09-22T08:06:29Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/129594 2026-02-05 col_2142_5131 col_2142_14789 com_2142_5130 com_2142_14788 com_2142_8903

application/pdf en text Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-05-01 The student, Lauren Boedicker, accepted the attached license on 2025-04-28 at 18:03. The student, Lauren Boedicker, submitted this Dissertation for approval on 2025-04-28 at 18:18. This Dissertation was approved for publication on 2025-04-29 at 16:00. DSpace SAF Submission Ingestion Package generated from Vireo submission #22037 on 2025-10-19 at 19:16:25 Ultrafast dynamics of [NiFe] hydrogenase models Boedicker, Lauren 2025-04-29 Vura-Weis, Joshua Vura-Weis, Joshua Mirica, Liviu M Olshanksy, Lisa Girolami, Gregory S [NiFe] Hydrogenase Mimics Ultrafast Dynamics Transient Spectroscopy Donor-Acceptor Charge Transfer eng The [NiFe] hydrogenase mimic [Ni(dppe)(pdt)Fe(CO)3] ([NiFe-1]) was one of the first to be capable of catalyzing dihydrogen generation. When [NiFe-1] is converted to [Ni(dppe)(pdt)-µH-Fe(CO)3]+ ([NiFeH]), in which a hydride group bridges the Ni-Fe bond, the geometry at the Ni center changes from tetrahedral to square planar.1 Some of the proposed short lived intermediates in the catalytic cycle, such as the Ni(II)Fe(0) pseudo- square planar state, have not been isolated or observed. [NiFe-1] was examined with ultrafast transient spectroscopy to learn more about its geometry change and the resulting effect on its electron transfer mechanism. Visible pump techniques were used to probe changes in the excited state of [NiFe-1] in response to light, by tracking changes in the IR and UV-visible absorption spectra. [NiFe-1] relaxes through its singlet manifold to the lowest energy singlet excited state within the time resolution of the instrument (<100 fs). Intersystem crossing to the triplet excited state occurrs in 7 ps, and it relaxes back to the ground state within 40 ps. [NiFe-1] relaxes faster than the [FeFe] mimics2–6 due to its lower lying triplet state (~ 1.6 eV lower than [FeFe(pdt)(CO)6]). [NiFe-1] also undergoes photolytic CO-loss and the product is stabilized by coordination of a THF solvent molecule. The chromophore perylene diimide (PDI) was tethered to [NiFe-1] through a phosphine linker group coordinated to the iron center. Excitation of the PDI at 530 nm resulted in a charge transfer from the [NiFe] center, observable in the transient UV-vis spectrum. The charge transfer state formed within a lifetime of 2 ps, and disappeared through charge recombination occurring in around 40 ps. A long-lived 5.7 ns absorption observed during these measurements could be a long lived *PDI based excited state, a CO loss product, or potentially a longer lived charge transfer state. Further studies with more metal centered techniques are needed elucidate the identity of the long-lived state. 2025-05 Thesis https://hdl.handle.net/2142/129594 Copyright 2025 Lauren Boedicker Chemistry Chemistry University of Illinois Urbana-Champaign Ph.D. Dissertation