A pillar[5]arene-based side-chain pseudorotaxanes and polypseudorotaxanes as novel fluorescent sensors for the selective detection of halogen ions

A pseudorotaxane and its polypseudorotaxanes formed between pillar[5]arene moieties and n-octylpyrazinium cations as novel fluorescent sensors for the selective detection of halogen ions were reported. A collapse of these pillar[5]arene-based pseudorotaxanes and polypseudorotaxanes occurred upon the addition of Cl^-, Br^-, and I^- (tetrabutylammonium salts), respectively, leading to their fluorescence recovery. The fluorescence enhancement of the pseudorotaxane and the polypseudorotaxanes increases in the order of I^- < Br^- < Cl^-, and the differences in fluorescence intensity could be easily distinguished by naked eyes under UV light illumination.