Paul Suranjan K, Herbert John M
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States.
J Am Chem Soc. 2021 Jul 14;143(27):10189-10202. doi: 10.1021/jacs.1c03131. Epub 2021 Jun 29.
Liquid microjet photoelectron spectroscopy is an increasingly common technique to measure vertical ionization energies (VIEs) of aqueous solutes, but the interpretation of these experiments is subject to questions regarding sensitivity to bulk versus interfacial solvation environments. We have computed aqueous-phase VIEs for a set of inorganic anions, using a combination of molecular dynamics simulations and electronic structure calculations, with results that are in excellent agreement with experiment regardless of whether the simulation data are restricted to ions at the air/water interface or to those in bulk aqueous solution. Although the computed VIEs are sensitive to ion-water hydrogen bonding, we find that the short-range solvation structure is sufficiently similar in both environments that it proves impossible to discriminate between the two on the basis of the VIE, a conclusion that has important implications for the interpretation of liquid-phase photoelectron spectroscopy. More generally, analysis of the simulation data suggests that the surface activity of soft anions is largely a second or third solvation shell effect, arising from disruption of water-water hydrogen bonds and not from significant changes in first-shell anion-water hydrogen bonding.
液体微射流光电子能谱是一种越来越常用的测量水溶性溶质垂直电离能（VIE）的技术，但这些实验的解释存在一些问题，即对本体溶剂化环境与界面溶剂化环境的敏感性。我们使用分子动力学模拟和电子结构计算相结合的方法，计算了一组无机阴离子的水相VIE，无论模拟数据是限于空气/水界面处的离子还是本体水溶液中的离子，结果都与实验结果非常吻合。尽管计算得到的VIE对离子 - 水氢键敏感，但我们发现两种环境中的短程溶剂化结构足够相似，以至于无法根据VIE区分两者，这一结论对液相光电子能谱的解释具有重要意义。更一般地说，对模拟数据的分析表明，软阴离子的表面活性在很大程度上是第二或第三溶剂化壳层效应，是由水 - 水氢键的破坏引起的，而不是由第一壳层阴离子 - 水氢键的显著变化引起的。
