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Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
Published on: May 29, 2018
Solvent dependent structural perturbations of chemical reaction intermediates visualized by time-resolved x-ray
Jonathan Vincent1, Magnus Andersson, Mattias Eklund
1Department of Photochemistry and Molecular Science, Uppsala University, P.O. Box 523, S-751 20 Uppsala, Sweden.
The Journal of Chemical Physics
|April 25, 2009
Summary
Ultrafast X-ray scattering reveals how photoexcited molecules change structure in solvents. Transient intermediates form faster and have longer lifetimes in nonpolar solvents, showing X-ray diffraction
Area of Science:
- Chemical Dynamics
- Photochemistry
- Structural Biology
Background:
- Ultrafast time-resolved wide-angle X-ray scattering (TR-WAXS) is a powerful technique.
- It determines structural dynamics of transient photochemical species.
- Understanding solvent effects on reaction pathways is crucial.
Purpose of the Study:
- To examine the structural evolution of photoexcited diiodomethane (CH(2)I(2)) in cyclohexane.
- To compare these dynamics with those in methanol.
- To demonstrate the capability of TR-WAXS in resolving solvent-dependent structural perturbations.
Main Methods:
- Ultrafast time-resolved wide-angle X-ray scattering (TR-WAXS).
- Photoexcitation of CH(2)I(2) in cyclohexane and methanol.
- Analysis of structural changes and intermediate lifetimes.
Main Results:
- Common initial dissociation pathway (CH(2)I(2) -> CH(2)I* + I*) observed in both solvents.
- Transient isomer CH(2)I-I lifetime is ~30 times longer in cyclohexane than in methanol.
- Iodine-iodine bond in CH(2)I-I is shorter in cyclohexane than in methanol due to H-bonding in methanol.
Conclusions:
- TR-WAXS accurately determines the structure of transient intermediates.
- Solvent polarity significantly influences the lifetime and structure of transient species.
- Time-resolved X-ray diffraction is sensitive to solvent-dependent structural perturbations.
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