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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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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)
- Mini-symposium: High-Harmonic Generation and XUV Spectroscopy
- 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
- Language
- English
- Permalink
- http://hdl.handle.net/2142/104383
- DOI
- 10.15278/isms.2019.RK03
- Copyright and License Information
- Copyright 2019 Kaili Zhang
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