Progress toward a rationally designed molecular motor.

A retrospective overview of the work in the author's laboratory leading to a prototype (43a) of a chemically powered molecular motor is provided. Beginning with a molecular brake (23) and then proceeding through a molecular "ratchet" (31), the development of a rationally designed molecular motor is described. The thermodynamic underpinnings of the concept are outlined, the synthetic routes to 23, 31, and 43a, are summarized, and the data documenting the function of 23, 31, and 43a are presented.