Chromene Lock, Thiol Key, and Mercury(II) Ion Hand: A Single Molecular Machine Recognition System

A regenerative, molecular machine-like ON-OFF-ON chemosensor based on a chromene molecule with the pyran ring OFF-ON-OFF cycle is reported for the first time. It behaves as a molecular lock that requires a thiol key to open the lock and a mercury(II) ion hand that unlatches the key for unsheathing the key to close the lock.