Department of Chemistry, Stanford University, Stanford, California 94305, United States.
Chemistry, School of Natural and Computational Sciences, Massey University Auckland, Private Bag 102904, Auckland 4442, New Zealand.
J Phys Chem A. 2020 Jul 23;124(29):5999-6008. doi: 10.1021/acs.jpca.0c02732. Epub 2020 Jul 9.
Previously, it has been demonstrated that external electric fields may be used to exert control over chemical reactivity. In this study, the impact of a strong, nonresonant IR field (1064 nm) on the photoisomerization of stilbene is investigated in cyclohexane solution. The design of a suitable reaction vessel for characterization of this effect is presented. The electric field supplied by the pulsed, near-IR radiation (ε = 4.5 × 10 V/cm) enhances the → photoisomerization yield at the red edge of the absorption spectrum (wavelengths between 337 and 340 nm). Within the microliter focal volume, up to 75% of all stilbene molecules undergo isomerization to stilbene in the strong electric-field environment, indicating a significant increase relative to the 35% yield of stilbene under field-free conditions. This result correlates with a 1-3% enhancement in the stilbene concentration throughout the bulk solution. Theoretical analysis suggests that the observed change is the result of dynamic Stark shifting of the ground and first excited states, leading to a significant redshift in -stilbene's absorption spectrum. The predicted increase in the absorption cross section in this range of excitation wavelengths is qualitatively consistent with the experimental increase in -stilbene production.
先前已经证明，外部电场可以用于控制化学反应性。在这项研究中，在环己烷溶液中研究了强非共振 IR 场（1064nm）对stilbene 光异构化的影响。介绍了用于表征这种效应的合适反应容器的设计。由脉冲近红外辐射（ε=4.5×10V/cm）提供的电场增强了吸收光谱红色边缘处（337nm 至 340nm 之间的波长）的 → 光异构化产率。在微升焦体积内，高达 75%的所有 stilbene 分子在强电场环境中异构化为 stilbene，与无场条件下 35%的 stilbene 产率相比有显著增加。这一结果与整个溶液中 stilbene 浓度提高 1-3%相关。理论分析表明，观察到的变化是由于基态和第一激发态的动态 Stark 位移引起的，导致 -stilbene 吸收光谱的显著红移。在该激发波长范围内，吸收截面的预测增加与 -stilbene 产量的实际增加定性一致。
