Rational design of ion-pair receptors for selective binding of hazardous salts

离子对受体，即阳离子和阴离子具有不同结合位置的分子，已经成为结合盐的有效材料。结合电子中和离子对的能力使离子对受体成为废物净化应用的候选对象。尽管在这类受体分子的合成方面取得了进展，但受体的合理设计、功能的展示及其在可持续离子去除方面的应用仍然具有挑战性。这些挑战既与缺乏严格的结构-功能关系有关，也与获得受体介导的离子对形成的直接实验证据有关。在这里，我们提出了一种通过离子对受体介导的离子对形成的协作性合成化学和物理化学研究。利用电偶极矩--离子对的一种固有性质--我们将为受体介导的离子配对提供直接证据。通过阳离子、阴离子和受体的系统变化以及溶液中离子对形成的同时光谱测定，本研究旨在得出一般的结构-功能关系。这些信息将允许预测离子对受体的结合效率和选择性，从而启动从反复试验的方法向任务特定受体分子的合理设计的转变。所获得的关系将用于预测和测试结合两种典型有毒盐--氯化铊和砷酸钠--的最佳受体结构。最后，我们将对具有最佳受体结构的聚合物树脂进行功能化处理，并测试其在选择性去除有害盐类方面的应用。

Ion-pair receptors, i.e. molecules with disparate binding sites for a cation and an anion, have emerged as efficient materials for binding salts. The ability of binding an electroneutral ion-pair renders ion-pair receptors promising candidates for waste purification applications. Despite the advances in synthesis of such receptor molecules, a rational design of the receptors, demonstration of their function, and their application for a sustainable removal of ions has remained challenging. These challenges are related to both the absence of stringent structure-function relationships and to challenges in obtaining direct experimental evidence for the receptor-mediated ion-pair formation. Here we propose a collaborative synthetic-chemical and physico-chemical study of ion-pair formation mediated via ion-pair receptors. Using the electrical dipole moment - an intrinsic property of ion-pairs - we will provide direct evidence for receptor mediated ion-pairing. Via systematic variation of the cation, the anion, and the receptor and simultaneous spectroscopic determination of the ion-pair formation in solution, the proposed study aims at deriving general structure-function relationships. Such information will allow predicting the binding efficiency and selectivity of ion-pair receptors and thus initiate a transition from trial-and-error approaches towards a rational design of task-specific receptor molecules. The obtained relationships will be used to predict and test the optimum receptor structure for binding two prototypical toxic salts, thallium chloride and sodium arsenate. Finally, we will functionalize a polymer resin with the optimum receptor structure and test its application for selective removal of hazardous salts.