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.
Herein, an electrochemical oxidative cross-coupling reaction between terminal alkynes and sulfonylhydrazides has been developed. Tetrabutylammonium iodide is used as the electrolyte and redox medium. The significant advantages of this method are high atom efficiency, functional group tolerance, and transition metal-and oxidantfree conditions. Most of the compounds exhibit good inhibitory activity on tumor cell lines, and one of the compounds can inhibit cell migration and induce apoptosis in HeLa cells.
Four endo-functionalized molecular tubes with urea/thiourea groups in the deep cavities have been synthesized, and their binding ability to neutral molecules studied. Very high binding affinity and selectivity have been achieved, which are rationalized by invoking the shape and electrostatic complementarity and dipole alignment.
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