Rotaxanes with integrated photoswitches: design principles, functional behavior, and emerging applications

Integrating molecular photoswitches into rotaxanes offers unique opportunities for precise control over their structural, dynamic, and functional properties. By harnessing light as a non-invasive stimulus with high spatial and temporal resolution, these photoswitches allow for the modulation of the rotaxanes' intra- and intermolecular interactions, optoelectronic properties, and shuttling dynamics. In this review, we discuss key examples of photoswitchable rotaxanes, organized according to the position of the photoswitch, either embedded in the axle or incorporated into the macrocycle. We examine the major classes of photoswitches used, including their switching mechanisms and the resulting influence on rotaxane operation. Due to their architectural versatility and precise light control, photoswitchable rotaxanes hold promise for a broad range of applications, including light-responsive molecular machines, smart materials, and biofunctional systems. However, emerging applications increasingly require rethinking and developing new structural designs that incorporate more efficient and advanced photoswitches to fully realize their potential.