University of Illinois Urbana-Champaign

Identifying the triplet intermediate state in the ultrafast photoinduced spin-transition of low-spin iron(II) compounds using femtosecond m2,3-edge absorption spectroscopy

Zhang, Kaili

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1448916.pptx
3948.pdf

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https://hdl.handle.net/2142/104383

Description

Title
Identifying the triplet intermediate state in the ultrafast photoinduced spin-transition of low-spin iron(II) compounds using femtosecond m2,3-edge absorption spectroscopy
Author(s)
Zhang, Kaili
Contributor(s)
  • Vura-Weis, Josh
  • Girolami, Gregory S.
  • de Groot, Frank
  • Lin, Ming-Fu
  • Verkamp, Max A.
  • Benke, Kristopher
  • Ryland, Elizabeth S.
  • Ash, Ryan T.
Issue Date
2019-06-20
Keyword(s)
High-harmonic generation and XUV spectroscopy
Date of Ingest
  • 2019-07-15T22:16:49Z
  • 2020-01-25T19:30:43Z
Abstract
In this work, we perform femtosecond M$_{2,3}$-edge XANES on low-spin iron complexes using a high harmonic generation (HHG) light source. Low-spin iron complexes hold promise as affordable alternatives to ruthenium-based photosensitizers. Conventional iron complexes with polypyridyl ligands are unsuitable because the excitation energy is dissipated in 200 fs by ultrafast population of the low-lying quintet metastable state. This formally $\Delta$S=2 process is conjectured to proceed through a metal-centered triplet intermediate state, but spectroscopic evidence of such an intermediate has remained elusive. Here we use femtosecond M$_{2,3}$-edge XANES to elucidate the role of metal-centered intermediate states. The transient response of Fe(phen)$_{3}$(SCN)$_{2}$ following excitation in the MLCT band clearly shows the presence of a metal-centered $^{3}$T$_{1}$ state. The transient response also shows oscillations consistent with the evolution of a vibrational wave-packet on the quintet surface. We also recorded the M$_{2,3}$-edge transient response of Fe[(CF$_{3}$)$_{2}$bpca]$_{2}$, a complex with a weaker ligand field. A comparison of the photophysical behaviors of Fe(phen)$_{3}$(SCN)$_{2}$ and Fe[(CF$_{3}$)$_{2}$bpca]$_{2}$ sheds light on the influence of crystal field strength on the relaxation mechanism of the MLCT state. Our findings add a hitherto missing piece to the existing picture of photophysics of iron complexes.
Publisher
International Symposium on Molecular Spectroscopy
Type of Resource
text
Genre of Resource
Conference Paper / Presentation
Language
eng
Permalink
http://hdl.handle.net/2142/104383
DOI
https://doi.org/10.15278/isms.2019.RK03
Copyright and License Information
Copyright 2019 Kaili Zhang

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Abstracts & Presentations - 2019 International Symposium on Molecular Spectroscopy PRIMARY