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Interrogating conformationally dependent electron-transfer dynamics via ultrafast visible pump/IR probe spectroscopy
Igor V Rubtsov1, Naomi P Redmore, Robin M Hochstrasser
1Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
Journal of the American Chemical Society
|March 5, 2004
Summary
Time-resolved visible pump/mid-infrared (IR) probe spectroscopy reveals conformational dynamics in photoinduced electron transfer (ET) and charge-separated (CS) states. This technique offers unique insights into structural evolution for donor-spacer-acceptor systems.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Photochemistry
Background:
- Understanding photoinduced electron transfer (ET) dynamics and the structural evolution of charge-separated (CS) states is crucial for designing efficient artificial photosynthetic systems.
- Donor-spacer-acceptor (D-Sp-A) systems are widely studied for their potential in solar energy conversion and molecular electronics.
- Characterizing the conformational changes that accompany ET is essential for elucidating reaction mechanisms.
Purpose of the Study:
- To demonstrate the utility of time-resolved visible pump/mid-infrared (IR) probe spectroscopy for investigating conformationally dependent photoinduced ET dynamics.
- To provide unique information on the structural evolution of CS states in D-Sp-A systems.
- To assess the mean interplanar torsional angle of electronically excited structural conformers undergoing ET.
Main Methods:
- Utilizing polarized visible pump/mid-IR probe spectroscopy to study photoinduced ET dynamics.
- Employing time-resolved transient spectroscopy to track structural evolution.
- Analyzing vibrational transition moments to interrogate molecular structure in excited and CS states.
Main Results:
- Demonstrated the ability to assess the mean donor-to-acceptor interplanar torsional angle in sub-picosecond timescales for D-Sp-A systems.
- Showcased the capability to determine the time evolution of this torsional angle.
- Confirmed that vibrational transition moments are localized, enabling structural interrogation.
Conclusions:
- Polarized visible pump/IR probe spectroscopy is a valuable tool for interrogating structure in electronically excited and CS states.
- The technique's ultrafast time resolution and high sensitivity are ideally suited for probing mechanistic issues in charge-transfer reactions.
- This spectroscopic approach offers unique insights into the conformational dynamics governing photoinduced ET.
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