Redox-Switchable Cavitands: Molecular Grippers

Key words

diquinone-based cavitands - molecular machines - resorcin[4]arenes

Significance

Here, a diquinone-based resorcin[4]arene cavitand goes from a kite to a vase form when reduced. The vase forms via hydrogen bonding between the central diols and the oxygens of the amides. This vase is stable even at –80 °C and can be used to capture the small molecule guests shown above. The molecules are shown in order of increasing association constant K _a . The vase cavitand releases the guests upon oxidation.

Comment

Both the kite and vase form are stable in deuterated chloroform, tetrahydrofuran, and mesitylene. After two to four days, the reduced form reverts into the oxidized form. A crystal structure of the reduced form has a 7.3° cavity, which allows it to encapsulate the solvent molecule mesitylene, as well as the larger guest molecules.