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Published on: February 4, 2017
Excess dynamic Stokes shift of molecular probes in solution
Mohsen Sajadi1, Nikolaus P Ernsting
1Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany. sajadi@fhi-berlin.mpg.de
The Journal of Physical Chemistry. B
|June 1, 2013
Summary
Molecular probes show dynamic Stokes shifts in polar solvents, reaching equilibrium via a slower blue shift. Nonpolar solutes exhibit red shifts, suggesting complex solvation dynamics influenced by excitation energy and solvent polarity.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Chemical Physics
Background:
- Solvation dynamics govern molecular probe behavior in different environments.
- Understanding time-resolved spectral shifts is crucial for chemical and biological processes.
Purpose of the Study:
- To investigate the time-dependent solvation dynamics of molecular probes using advanced spectroscopic techniques.
- To elucidate the influence of solvent polarity and excitation energy on spectral shifts.
Main Methods:
- Broad-band fluorescence upconversion spectroscopy with high time (~80 fs) and spectral (~10 cm(-1)) resolution.
- Excitation of polar and nonpolar molecular probes in various solvents (acetonitrile, acetone, methanol).
Main Results:
- Polar solutes exhibited dynamic Stokes shifts extending to the red, followed by a slower blue shift to equilibrium.
- Nonpolar solutes showed excess red shifts in both polar and nonpolar solvents.
- Methanol did not display the dynamic Stokes shift effect even with high vibrational energy.
Conclusions:
- Solvation dynamics are complex, influenced by transient heating, conformational changes, and molecular cavity size.
- Optimal optical excitation for solvation studies should be near the band origin to avoid artifacts.
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