Selective lithium halide ion-pair sensing by a dynamic metalloporphyrin [2]rotaxane

Abstract

A dynamic zinc(II) metalloporphyrin axle-containing [2]rotaxane with a heteroditopic macrocycle component is shown to selectively recognise and optically sense lithium halide (LiX) ion-pair species. ¹H NMR and UV-visible absorption experiments demonstrate a strong macrocycle pyridyl⋯Zn(II) metalloporphyrin axle interaction which results in a marked co-conformational bias in the free [2]rotaxane host system. Extensive ¹H NMR cation, anion and ion-pair titration experiments demonstrate the binding of lithium halide ion-pairs disrupts the inter-component mechanical bond interaction, wherein dynamic macrocycle shuttling to an axle triazole station enables co-operative axle-separated LiX ion-pair recognition and the selective optical sensing of lithium halide salts.