A synthetic approach to a molecular crank mechanism: toward intramolecular motion transformation between rotation and translation.

A molecular crank mechanism that enables transformation between rotational and translational motions was designed and synthesized. This molecule consists of a molecular ball bearing as the rotational part in which two disk-shaped rotors can rotate relative to each other through ligand exchange and flipping motion, and a [2]rotaxane as a translational part in which an axle molecule can move back-and-forth through the cavity of a crown ether-based macrocycle. (1)H NMR analysis revealed that these two motions influence each other.