Pumps through the Ages

Artificial molecular machines (AMMs) have profoundly enhanced scientists' capability to manipulate the relative movements of components within molecules. Mechanically interlocked molecules (MIMs) with movable components have contributed to the design and synthesis of AMMs. The operation of these wholly synthetic molecular machines away from equilibrium is governed by ratchetmechanisms that require a supply of energy. In this review, we discuss the emergence of pumps, both natural and crafted through the ages, focusing on recent advances toward the design and synthesis of artificial molecular pumps (AMPs) that are capable of creating local concentrations of rings on collecting chains. We conclude our discussion by considering a recently reported catalysis-driven AMM and the ramifications for exploiting catalysis to control non-equilibriumbehavior.