Chloride recognition in aqueous media by a rotaxane prepared via a new synthetic pathway.

The preparation of a novel rotaxane, which consists of a pyridyl macrocycle wheel and pyridinium axle components, by a new synthetic pathway that involves anion templation in combination with favorable π-π stacking interactions was studied. The synthesis of new rotaxane 6-Cl was achieved by the addition of 3,5-bis(chlorocarbonyl) pyridine to a mixture of bis-amine, Et3N, and the stoppered axle component 5-Cl in CH2Cl2. Simple variation of the nature of the acid chloride can lead to a range of rotaxanes being prepared which contain interlocked cavities of variable dimensions and rotaxane was isolated in 32% yield following preparative thin-layer chromatography. The new rotaxane's impressive selective recognition of chloride in aqueous solvent media highlights the real potential such interlocked molecular host systems might have in anion chemical sensor technological applications