Ring-Closing Reaction in Diarylethene Captured by Femtosecond Electron Crystallography

The photoinduced ring-closing reaction in diarylethene, which serves as a model system for understanding reactive crossings through conical intersections, was directly observed with atomic resolution using femtosecond electron diffraction. Complementary ab initio calculations were also performed. Im...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2013-12, Vol.117 (49), p.15894-15902
Main Authors: Jean-Ruel, Hubert, Gao, Meng, Kochman, Michal A, Lu, Cheng, Liu, Lai Chung, Cooney, Ryan R, Morrison, Carole A, Miller, R. J. Dwayne
Format: Article
Language:English
Subjects:
Atomic properties
Carbon
Carbon - chemistry
Chain dynamics
Cyclization
Electrons
Ethylenes - chemistry
Femtosecond
Formations
Intersections
Models, Molecular
Quantum Theory
Sampling
Thermal conductivity
Thiophenes - chemistry
Time Factors
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Summary:The photoinduced ring-closing reaction in diarylethene, which serves as a model system for understanding reactive crossings through conical intersections, was directly observed with atomic resolution using femtosecond electron diffraction. Complementary ab initio calculations were also performed. Immediately following photoexcitation, subpicosecond structural changes associated with the formation of an open-ring excited-state intermediate were resolved. The key motion is the rotation of the thiophene rings, which significantly decreases the distance between the reactive carbon atoms prior to ring closing. Subsequently, on the few picosecond time scale, localized torsional motions of the carbon atoms lead to the formation of the closed-ring photoproduct. These direct observations of the molecular motions driving an organic chemical reaction were only made possible through the development of an ultrabright electron source to capture the atomic motions within the limited number of sampling frames and the low data acquisition rate dictated by the intrinsically poor thermal conductivity and limited photoreversibility of organic materials.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp409245h