PerspectiveCHEMICAL PHYSICS

Following photoexcited electrons in reactions

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Science  07 Apr 2017:
Vol. 356, Issue 6333, pp. 31
DOI: 10.1126/science.aan0354

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Summary

Light provides a flexible energy source that can precisely manipulate material systems on size scales ranging from the molecular to the macroscopic, with both spatial and temporal control. Photoinduced electronic excitation can induce molecular motion by changing the shape of a molecule through isomerization around a central bond (see the figure) or through the opening and closing of a ring. Molecular motors have been developed that rely on a unidirectional cis-trans isomerization (1), and optical switches and memory rely on cis-trans isomerization or reversible ring-opening reactions (2, 3). On page 54 of this issue, Attar et al. (4) followed the fundamental dynamics of electrons moving during the photoinduced opening of a 1,3-cyclohexadiene ring with ultrafast soft x-ray spectrometry. This kind of transformation is a core element in many photoactive systems and a paradigm for the electronic evolution of polyenes (hydrocarbons with alternating single and double bonds).