A rationally designed prototype of a molecular motor

A proof of principle of the first rationally designed, chemically powered, molecular-scale motor is described. The thermodynamic considerations leadin g to the choice of 6a and 7a as the initial prototypes are provided, and th e synthesis of 6a and 7a and the separation of them from their atropisomers are detailed. The phosgene-powered unidirectional rotation of 6a to its ro tamer 6b is demonstrated. It is further established that shortening the len gth of the tether (-->7a) changes the rate-limiting step and accelerates th e speed of rotation.