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, key examples of photoswitchable rotaxanes are discussed. The role of the position of the photoswitch, either embedded in the axle or incorporated into the macrocycle is highlighted. The major classes of photoswitches are demonstrated, 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. Several CD-based examples are covered including photoresponsive polymeric actuator utilizing [2]rotaxane units as topological cross-links in a polymer network, in which the azobenzene serves as a recognition site for an α-cyclodextrin macrocycle and stilbene trans-to-cis photoisomerization induced translocation of the cyclodextrin along the axle,

Schematic of common rotaxanes (left) and depiction of the macrocycle shuttling (right).

Matsushima, J. E.; Khushbu; Abdulsalam, Z.; Conthagamage, U. N. K.; García-López, V. Rotaxanes with integrated photoswitches: design principles, functional behavior, and emerging applications. Beilstein J. Org. Chem. 2025, 21, 2345–2366. doi:10.3762/bjoc.21.179