Molecular crystal structure of a rotaxane. A rotaxane is a chemical compound composed of a linear molecular chain passing through a chainlike molecular ring. The entities that form rotaxanes, the linear and cyclic molecules, are bonded mechanically rather than chemically in what is called a topological bond. Rotaxane-based molecular compounds or molecular machines, have been interesting potential uses in molecular electronics, molecular switching elements and molecular shuttles. Shown is a crystal structure with an cyclodextrin macrocycle.