Munasinghe Vihanga K, Tay Hui Min, Manawadu Dilhan, Pancholi Jessica, Zhang Zongyao, Beer Paul D
Department of Chemistry, University of Oxford, Chemistry Research Laboratory Mansfield Road, Oxford OX1 3TA, UK.
Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, OX1 3QZ, UK.
Dalton Trans. 2024 Aug 27;53(34):14219-14225. doi: 10.1039/d4dt01807a.
The first heteroditopic [2]rotaxane host systems capable of strong and selective binding of lithium chloride ion-pair species are described. Importantly, a cooperative 'switch on' mechanism was found to operate, in which complexation of a lithium metal cation enhances the halide anion affinity of the rotaxanes a combination of favourable proximal electrostatic and preorganised allosteric effects. The mechanically bonded rotaxane host design features a macrocycle component possessing a 2,6-dialkoxy pyridyl cation binding motif and an isophthalamide anion binding group, as well as an axle component functionalised with either a halogen bonding (XB) iodotriazole or hydrogen bonding (HB) prototriazole moiety. Extensive quantitative H NMR titration studies in CDCN/CDCl solvent mixtures determined enhanced ion-pair binding affinities for lithium halides over the corresponding sodium or potassium halide salts, with the axle prototriazole-containing HB rotaxane in particular demonstrating a marked selectivity for lithium chloride. Solid-state X-ray crystallographic studies and computational DFT investigations provide evidence for a [2]rotaxane host axle-separated ion-pair binding mode, in which complementary cation and anion binding motifs from both the macrocycle and axle components act convergently to recognise each of the charged guest species.
本文描述了首个能够对氯化锂离子对物种进行强且选择性结合的异双位点[2]轮烷主体体系。重要的是，发现了一种协同“开启”机制，其中锂金属阳离子的络合增强了轮烷对卤化物阴离子的亲和力，这是有利的近端静电效应和预组织变构效应共同作用的结果。机械键合的轮烷主体设计具有一个大环组分，该组分具有一个2,6-二烷氧基吡啶基阳离子结合基序和一个间苯二甲酰胺阴离子结合基团，以及一个用卤素键合（XB）碘三唑或氢键合（HB）质子三唑部分功能化的轴组分。在CDCN/CDCl溶剂混合物中进行的广泛定量1H NMR滴定研究确定，卤化锂对离子对的结合亲和力高于相应的卤化钠或卤化钾盐，特别是含轴质子三唑的HB轮烷对氯化锂表现出显著的选择性。固态X射线晶体学研究和计算DFT研究为[2]轮烷主体轴分离离子对结合模式提供了证据，其中大环和轴组分的互补阳离子和阴离子结合基序共同作用以识别每个带电客体物种。
