Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
Int J Mol Sci. 2021 Oct 5;22(19):10754. doi: 10.3390/ijms221910754.
A 4-nitro-L-phenylalanine scaffold was used to construct effective ion pair receptors capable of binding anions in an enhanced manner with the assistance of alkali metal cations. A benzocrown ether was linked to a receptor platform the amide function so as to support the squaramide function in anion binding and to allow all three NHs to act simultaneously. The binding properties of the receptors were determined using UV-vis, H NMR, 2D NMR, and DOSY spectroscopy in MeCN and in the solid state by X-ray measurements. Ion pair receptor was found to interact with the most strongly with salts, and the removal of its key structural elements was shown to hinder the receptor action. The amide proton was recognized to switch from having involvement in an intramolecular hydrogen bond to interacting with anions upon complexation. Apart from carboxylates, which promote deprotonation, and other monovalent salts creating 1:1 complexes with the receptor, more complex equilibria were established upon the complexation of with sulfates. Receptor was shown to be capable of the extraction of ion pairs from the aqueous to organic phase and of the cation-enhanced transport chloride and sulfate anions across a bulk chloroform membrane. These features may open the door for its use in regulating ion concertation under interfacial conditions and acting as a potential drug to treat channelopathies.
采用 4-硝基-L-苯丙氨酸骨架构建了有效的离子对受体，在碱金属阳离子的辅助下，能够以增强的方式结合阴离子。苯并冠醚连接到受体平台上的酰胺官能团上，以支持阴离子结合中的 squaramide 官能团，并允许所有三个 NH 同时起作用。使用 UV-vis、1H NMR、2D NMR 和 DOSY 光谱在 MeCN 中和通过 X 射线测量在固态中确定了受体的结合性质。发现离子对受体与盐的相互作用最强，并且去除其关键结构元件会阻碍受体的作用。酰胺质子被识别为在络合时从参与分子内氢键转变为与阴离子相互作用。除了促进去质子化的羧酸根和与受体形成 1:1 配合物的其他单价盐外，与硫酸盐络合时还建立了更复杂的平衡。受体被证明能够从水相萃取离子对到有机相，并能够增强阳离子输送氯离子和硫酸盐阴离子穿过氯仿膜。这些特性可能为其在界面条件下调节离子浓度和作为治疗通道病的潜在药物的用途开辟了道路。
