Maitra Anwesha, Das Pratyusha, Thompson Barry C, Dawlaty Jahan M
Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States.
J Phys Chem B. 2023 Mar 23;127(11):2511-2520. doi: 10.1021/acs.jpcb.2c08030. Epub 2023 Mar 14.
Vibrational Stark probes are incisive tools for measuring local electric fields in a wide range of chemical environments. The interpretation of the frequency shift often gets complicated due to the specific interactions of the probe, such as hydrogen bonding and Lewis bonding. Therefore, it is important to distinguish between the pure electrostatic response and the response due to such specific interactions. Here we report a molecular system that is sensitive to both the Stark effect from a single ion and the explicit Lewis bonding of ions with the probe. The molecule consists of a crown ether with an appended benzonitrile. The crown captures cations of various charges, and the electric field from the ions is sensed by the benzonitrile probe. Additionally, the lone pair of the benzonitrile can engage in Lewis interactions with some of the ions by donating partial charge density to the ions. Our system exhibits both of these effects and therefore is a suitable test bed for distinguishing between the pure electrostatic and the Lewis interactions. Our computational results show that the electrostatic influence of the ion is operative at large distances, while the Lewis interaction becomes important only within distances that permit orbital overlap. Our results may be useful for using the nitrile probe for measuring electrostatic and coordination effects in complex ionic environments such as the electrode-electrolyte interfaces.
振动斯塔克探针是用于测量各种化学环境中局部电场的锐利工具。由于探针的特定相互作用，如氢键和路易斯键合，频移的解释常常变得复杂。因此，区分纯静电响应和此类特定相互作用引起的响应很重要。在这里，我们报告了一个对单个离子的斯塔克效应以及离子与探针的明确路易斯键合都敏感的分子系统。该分子由一个带有附加苯甲腈的冠醚组成。冠醚捕获各种电荷的阳离子，离子产生的电场由苯甲腈探针感知。此外，苯甲腈的孤对电子可以通过向离子提供部分电荷密度与一些离子发生路易斯相互作用。我们的系统展示了这两种效应，因此是区分纯静电相互作用和路易斯相互作用的合适测试平台。我们的计算结果表明，离子的静电影响在远距离起作用，而路易斯相互作用仅在允许轨道重叠的距离内才变得重要。我们的结果可能有助于使用腈探针测量复杂离子环境（如电极 - 电解质界面）中的静电和配位效应。
