Artificial molecular devices and machines driven by light

Light-induced processes are at the basis of fundamental natural phenomena as well as of a variety of applications. Since the functions that can arise from the interaction between light and matter depend on the degree of complexity and organization of the receiving ‘matter’, the research on these processes has progressively moved from molecular to supramolecular (multicomponent) systems, thereby originating the field of supramolecular photochemistry. In this context, examples of photochemical molecular devices and machines—that is, multicomponent chemical systems capable to perform specific functions under light stimulation—have been developed. Here we describe two recent examples of such systems based on pseudorotaxane and rotaxane species. These studies are of interest not only for the growth of nanoscience, but also for increasing the basic understanding and testing current theoretical treatments of photoinduced processes.