Raucci Umberto, Weir Hayley, Bannwarth Christoph, Sanchez David M, Martínez Todd J
Department of Chemistry and The PULSE Institute, Stanford University, Stanford, CA, 94305, USA.
SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.
Nat Commun. 2022 Apr 19;13(1):2091. doi: 10.1038/s41467-022-29662-1.
Chirality is a molecular property governed by the topography of the potential energy surface (PES). Thermally achiral molecules interconvert rapidly when the interconversion barrier between the two enantiomers is comparable to or lower than the thermal energy, in contrast to thermally stable chiral configurations. In principle, a change in the PES topography on the excited electronic state may diminish interconversion, leading to electronically prochiral molecules that can be converted from achiral to chiral by electronic excitation. Here we report that this is the case for two prototypical examples - cis-stilbene and cis-stiff stilbene. Both systems exhibit unidirectional photoisomerization for each enantiomer as a result of their electronic prochirality. We simulate an experiment to demonstrate this effect in cis-stilbene based on its interaction with circularly polarized light. Our results highlight the drastic change in chiral behavior upon electronic excitation, opening up the possibility for asymmetric photochemistry from an effectively nonchiral starting point.
手性是一种由势能面（PES）的拓扑结构决定的分子特性。当两种对映体之间的互变势垒与热能相当或低于热能时，热非手性分子会迅速相互转化，这与热稳定的手性构型形成对比。原则上，激发电子态上PES拓扑结构的变化可能会减少互变，从而产生电子前手性分子，这种分子可以通过电子激发从非手性转变为手性。在此，我们报告两个典型例子——顺式二苯乙烯和顺式刚性二苯乙烯就是这种情况。由于它们的电子前手性，这两个体系对每个对映体都表现出单向光异构化。我们基于顺式二苯乙烯与圆偏振光的相互作用模拟了一个实验来证明这种效应。我们的结果突出了电子激发后手性行为的剧烈变化，为从有效非手性起点进行不对称光化学开辟了可能性。
