Selective Recognition of Highly Hydrophilic Molecules in Water by Endo-Functionalized Molecular Tubes

Selective recognition of neutral hydrophilic molecules in water is a challenge for supramolecular chemistry but commonplace in nature. By mimicking the binding pocket of natural receptors, endo-functionalized molecular tubes are proposed to meet this challenge. We found that two molecular tubes with inwardly directed hydrogen-bond donors recognize highly hydrophilic solvent molecules in water with high selectivity. In the complexes, hydrogen bonding occurs in the deep and hydrophobic cavity. The cooperative action between hydrogen bonding and hydrophobic effects accounts for the high affinity and selectivity. The molecular receptor is fluorescent and can detect concentrations of 1,4-dioxane-a known carcinogen and persistent environmental contaminant-in water at a limit of 119 ppb. The method simplifies the analytic procedure for this highly hydrophilic molecule.