Selective Detection of Fe(3+), F(–), and Cysteine by a Novel Triazole-Linked Decaamine Derivative of Pillar[5]arene and Its Metal Ion Complex in Water

[Image: see text] Appropriately functionalized pillar[n]arenes are elegant supramolecular hosts for ion and molecule sensing. A water-soluble decaamine derivative of pillar[5]arene (APA) bearing triazole and amide moieties is synthesized. The ion and molecular recognition properties of APA are studied by fluorescence, UV–visible, and (1)H nuclear magnetic resonance (NMR) spectroscopy. The APA selectively detects Fe(3+) among 11 studied ions, which are important in several biological processes. Moreover, the in situ prepared Fe(3+) complex of APA (FeAPA) exhibits the highest responsiveness toward F(–) (∼12-fold) among 11 anions and cysteine (∼120-fold) among the 20 naturally occurring amino acids by a fluorescence turn-on mechanism.