Max Born Institute, Max-Born-Straße 2A, 12489 Berlin, Germany.
Department of Biotechnology, Chemistry and PharmacyUniversity of Siena, Via A. Moro 2, I-53100 Siena, Italy.
J Phys Chem Lett. 2023 Jul 6;14(26):6061-6070. doi: 10.1021/acs.jpclett.3c00828. Epub 2023 Jun 26.
XUV photoelectron spectroscopy (XPS) is a powerful method for investigating the electronic structures of molecules. However, the correct interpretation of results in the condensed phase requires theoretical models that account for solvation. Here we present experimental aqueous-phase XPS of two organic biomimetic molecular switches, NAIP and -HDIOP. These switches are structurally similar, but have opposite charges and thus present a stringent benchmark for solvation models which need to reproduce the observed ΔeBE = 1.1 eV difference in electron binding energy compared to the 8 eV difference predicted in the gas phase. We present calculations using implicit and explicit solvent models. The latter employs the average solvent electrostatic configuration and free energy gradient (ASEC-FEG) approach. Both nonequilibrium polarizable continuum models and ASEC-FEG calculations give vertical binding energies in good agreement with the experiment for three different computational protocols. Counterions, explicitly accounted for in ASEC-FEG, contribute to the stabilization of molecular states and reduction of ΔeBE upon solvation.
X 射线光电子能谱（XPS）是一种研究分子电子结构的强大方法。然而，在凝聚相下正确解释结果需要考虑溶剂化的理论模型。在这里，我们展示了两种有机仿生分子开关 NAIP 和 -HDIOP 的实验水相 XPS。这些开关在结构上相似，但电荷相反，因此为溶剂化模型提供了严格的基准，这些模型需要复制观察到的电子结合能的 ΔeBE = 1.1 eV 差异，而在气相中预测的差异为 8 eV。我们使用隐式和显式溶剂模型进行了计算。后者采用平均溶剂静电构型和自由能梯度（ASEC-FEG）方法。两种非平衡极化连续体模型和 ASEC-FEG 计算都为三种不同的计算方案提供了与实验很好吻合的垂直结合能。在 ASEC-FEG 中明确考虑的抗衡离子有助于稳定分子状态并降低溶剂化时的 ΔeBE。
