Polyether ionophores with redox-functional thiol groups were synthesized: they are a diaza-18-crown-6 with a disulfide cap that exhibits redox-responsive interconversion between crown(1red) and cryptand(1ox) and tri- and tetra(oxyethylene)s having a mercapto and an 8-quinolyl group as their terminal groups that feature redox-responsive interconversion between monopodands (2red) and dipodands (2ox). For Na+ 1red and 1ox showed a similar ion affinity, but 1ox bound K+, Rb+, and Cs+ more efficiently than 1red because of the coordination of the cap oxygens to the complexed metal cations. The difference was rationalized by such that “K+ Rb+ and Cs+ also) perches on the crown ring whereas Na+ nests in it,” 2ox showed, in most cases, the ion affinity significantly higher than corresponding 2red, indicating the cooperative action of the two poly(oxyethylene) chains on the ion-binding. The rate of K+ transport with 2red across a liquid membrane was very slow but 2ox carried K+ more efficiently. It was found that the rate of K+ transport started with is efficiently accelerated by the addition of I2. This is due to the redox-switch of the carrier from 2red to 2ox. These results suggest that the redox-functionalized ionophores provide novel applications of ion-extraction and ion-transport.
合成了带有红
氧反应功能的多醚
离子载体:它们是具有二
硫化物帽的二
氮-
18-冠-6,能够在
冠(1red)和隐蔽剂(1ox)之间进行红
氧反应的相互转化,以及带有巯基和8-
喹啉基作为末端基团的三和四(
氧乙烯)化合物,它们在单
配体(2red)和双
配体(2ox)之间也能进行红
氧反应的相互转化。对于Na+,1red和1ox表现出相似的离子亲和力,但1ox对K+、Rb+和Cs+的结合效率高于1red,这归因于帽
氧与配位
金属阳离子的配位。这个差异可以理解为“K+、Rb+和Cs+也停留在
冠环上,而Na+则嵌入其中。”在大多数情况下,2ox的离子亲和力显著高于相应的2red,表明两个聚(
氧乙烯)链在离子结合中的协同作用。2red通过液体膜传输K+的速率非常慢,但2ox则更高效地携带K+。研究发现,K+的运输速率在添加I2后得到了有效加速。这是因为载体的红
氧开关从2red转变为2ox。这些结果表明,具有红
氧功能的
离子载体在离子提取和离子运输方面提供了新的应用。