Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States.
Yale Quantum Institute, Yale University, P.O. Box 208334, New Haven, Connecticut 06520-8263, United States.
J Phys Chem Lett. 2022 Sep 8;13(35):8254-8263. doi: 10.1021/acs.jpclett.2c02037. Epub 2022 Aug 26.
Proton-coupled electron transfer (PCET) is the underlying mechanism governing important reactions ranging from water splitting in photosynthesis to oxygen reduction in hydrogen fuel cells. The interplay of proton and electronic charge distribution motions can vary from sequential to concerted schemes, with elementary steps occurring on ultrafast time scales. We demonstrate with a simulation study that femtosecond soft-X-ray spectroscopy provides key insights into the PCET mechanism of a photoinduced intramolecular enol* → keto* tautomerization reaction. A full quantum treatment of the electronic and nuclear dynamics of 2-(2'-hydroxyphenyl)benzothiazole upon electronic excitation reveals how spectral signatures of local excitations from core to frontier orbitals display the distinctly different stages of charge relocation for the H atom, donating, and accepting sites. Our findings indicate that ultraviolet/X-ray pump-probe spectroscopy provides a unique way to probe ultrafast electronic structure rearrangements in photoinduced chemical reactions essential to understanding the mechanism of PCET.
质子耦合电子转移（PCET）是一种基本机制，它控制着从光合作用中的水分解到氢燃料电池中的氧还原等重要反应。质子和电子电荷分布运动的相互作用可以从顺序到协同方案变化，基本步骤发生在超快时间尺度上。我们通过模拟研究证明，飞秒软 X 射线光谱为光诱导分子内烯醇*→酮*互变异构反应的 PCET 机制提供了关键的见解。电子激发后，对 2-（2'-羟基苯基）苯并噻唑的电子和核动力学进行全量子处理，揭示了从核心到前沿轨道的局部激发的光谱特征如何显示 H 原子、供体和受体位点的电荷重新定位的明显不同阶段。我们的研究结果表明，紫外/X 射线泵浦探测光谱提供了一种独特的方法来探测光诱导化学反应中超快电子结构重排，这对于理解 PCET 的机制至关重要。
