Unidirectional Rotation in Catenanes

In this work, two different catenane based molecular motors were reviewed. These motor molecules consist of two interlocked rings, one of which has binding sites for the other ring. The smaller ring without the binding sites can rotate over the other macrocycle when the affinities of the binding sites are changed. If the rotation is unidirectional the molecule could in principle perform work. In the two systems investigated, unidirectionality was achieved but it was not shown that the molecules could indeed perform work. The molecular motors showed good unidirectionality, but the speed of rotation was quite poor. Therefore, these motors are still far from ideal. In the last section some possible improvements are suggested.