2rotaxanes

Rotaxanes are a class of mechanically interlocked molecular architectures. They consist of at least two components: a linear or macrocyclic molecule that is threaded through a ring-shaped molecule. The ring molecule is typically a macrocycle such as a cyclodextrin or a porphyrin, while the linear molecule, often referred to as the "axle," possesses bulky end groups or stopper units that prevent the ring from dissociating. This threading creates a unique structure where the ring is free to move along the axle, but cannot be removed without breaking covalent bonds.

The term "rotaxane" is derived from the Latin word "rota" meaning wheel and "axis" meaning axle. The synthesis of rotaxanes often involves templating or statistical methods. In templating, the macrocycle is pre-organized around the axle molecule, facilitating the threading process. Statistical synthesis relies on a high concentration of reactants, increasing the probability of threading before the stopper groups are attached.

The functional properties of rotaxanes stem from the relative motion of their components. This controlled movement allows them to be used as molecular switches, sensors, and even as components in molecular machines. For instance, the position of the ring on the axle can be altered by external stimuli such as changes in pH, light, or redox potential, leading to a change in the rotaxane's properties or function. Research in this area focuses on designing new rotaxane structures with tailored properties for applications in nanotechnology, materials science, and supramolecular chemistry.