What we have achieved and what we are expecting
Unlike the molecular axle of the first generation of pumps (Nat. Nanotechnol. 2015, 10, 70), the axles developed in the first period of the LEAPS project can be functionalized while maintaining their photoinduced pumping functionality (Angew. Chem. 2019, 2020; Chem. Eur. J. 2021). The construction of autonomous light driven rotary motors based on catenanes, and of rotaxane-type systems in which macrocyclic rings can be transferred and stored in a molecular reservoir under light irradiation are underway. The new molecular pumps are also being modified for incorporation in membranes or in polymers. Significant progress on photoswitchable molecules and materials has also been achieved (Angew. Chem. 2018, JACS 2018, 2020).
Another significant result of the project is the demonstration that the ring shuttling motion in rotaxanes can lead to new and potentially useful functions, such as the transfer of chemical information between two distant sites (PNAS 2018), the control of mechanical chirality and chiral anion recognition (JACS 2019), and frustrated ring-axle systems (JACS 2021). Possibilities emerge not only for the rational design of species with tailor-made functional and structural properties, but also for the development of model systems to understand some of Nature’s most effective regulatory mechanisms, namely, allostery, proton-coupled electron transfer and enantioselective molecular recognition.