School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA.
Chemistry. 2022 Feb 21;28(10):e202104332. doi: 10.1002/chem.202104332. Epub 2022 Jan 22.
A unique trend in the binding affinity between cationic metal-organic cages (MOCs) and external counteranions in aqueous media was observed. Similar to many macroions, two MOCs, sharing similar structures but carrying different number of charges, self-assembled into hollow spherical single-layered blackberry-type structures through counterion-mediated attraction. Dynamic and static light scattering and isothermal titration calorimetry measurements confirm the stronger interactions among less charged MOCs and counteranions than that of highly charged MOCs, leading to larger assembly sizes. DOSY NMR measurements suggest the significance of thick hydration shells of highly charged MOCs, inhibiting the MOC-counterion binding and weakening the interaction between them. This study demonstrates that the greater role played by hydration shell on ion-pair formation comparing with charge density of MOCs.
在水相介质中，观察到阳离子金属有机笼 (MOC) 与外部抗衡阴离子之间结合亲和力的独特趋势。与许多大分子类似，两个具有相似结构但带有不同电荷数的 MOC 通过抗衡阴离子介导的吸引力自组装成中空球形单层黑莓型结构。动态和静态光散射以及等温热滴定测量证实了带较少电荷的 MOC 与抗衡阴离子之间的相互作用比带高电荷的 MOC 更强，导致更大的组装尺寸。DOSY NMR 测量表明，高电荷 MOC 的厚水合壳的重要性，抑制了 MOC-抗衡离子的结合并削弱了它们之间的相互作用。这项研究表明，与 MOC 的电荷密度相比，水合壳在离子对形成中起更大的作用。
