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Published on: October 18, 2018
How fast is optically induced electron transfer in organic mixed valence systems?
C Lambert1, M Moos, A Schmiedel
1Institute of Organic Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany. christoph.lambert@uni-wuerzburg.de.
Optically induced electron transfer in organic mixed valence compounds occurs on the femtosecond timescale, significantly faster than thermal processes. This study reveals ultrafast internal conversion and cooling dynamics following optical excitation.
Area of Science:
- Organic Chemistry
- Photochemistry
- Spectroscopy
Background:
- Thermally induced electron transfer (ET) in organic mixed valence compounds is well-studied.
- The dynamics of optically induced ET processes in these systems remain largely unknown.
Purpose of the Study:
- To investigate the dynamics of optically induced electron transfer in mixed valence compounds.
- To compare the rates of optical and thermal electron transfer.
Main Methods:
- Utilized near-infrared (NIR) transient absorption spectroscopy.
- Employed femtosecond (fs)-time resolution to capture ultrafast dynamics.
- Studied mixed valence compounds featuring triphenylamine redox centers bridged by conjugated spacers.
Main Results:
- Observed an internal conversion (IC) process occurring within 50–200 fs.
- Identified ultrafast cooling to the ground state within 1 picosecond (ps).
- Found optically induced ET to be 3-4 orders of magnitude faster than thermally induced ET.
Conclusions:
- Optically induced electron transfer in these systems is extremely rapid.
- Internal conversion and subsequent cooling are key ultrafast processes following optical excitation.
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