Rotaxane-based molecular machines operated by photoinduced electron transfer

Abstract A molecular machine is an assembly of a definite number of molecular components designed to perform mechanical motions as a result of an appropriate external stimulation. Like their macroscopic counterparts, nanoscale machines need energy to operate. Energy can be supplied through (i) chemical reactions, (ii) electrochemical processes, and (iii) photoinduced processes. Although most molecular motors of the biological world are fueled by chemical reactions, for several reasons light is a very good choice to operate artificial molecular machines. Rotaxanes, owing to their peculiar architecture, are attractive candidates for the construction of artificial nanoscale machines. By adopting an incrementally staged design strategy, photoinduced electron-transfer processes have been engineered within rotaxane-type structures with the purpose of obtaining light-powered molecular machines. Such an approach is illustrated by describing the behavior of prototypes investigated in our laboratories.