This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/129594
Description
Title
Ultrafast dynamics of [NiFe] hydrogenase models
Author(s)
Boedicker, Lauren
Issue Date
2025-04-29
Director of Research (if dissertation) or Advisor (if thesis)
Vura-Weis, Joshua
Doctoral Committee Chair(s)
Vura-Weis, Joshua
Committee Member(s)
Mirica, Liviu M
Olshanksy, Lisa
Girolami, Gregory S
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
[NiFe] Hydrogenase Mimics
Ultrafast Dynamics
Transient Spectroscopy
Donor-Acceptor
Charge Transfer
Abstract
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.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
