Novel dual-motor nanorotator assembled by cyclo[18]carbon and figure-eight carbon hoop

Two unique nanorings recently generated, namely cyclo[18]carbon (C18) and oligoparaphenylene (OPP), were theoretically designed to assemble an extraordinary dual-motor supramolecular rotator (2C18@OPP) with large included angle. The size adaptability and shape complementarity of guest C18 to host OPP as well as the thermodynamic analysis of 2C18@OPP showed that the complex can form easily and exist stably below 404 K. Energy decomposition and various real-space function analyses of host-guest interaction revealed the characteristic and nature of the non-covalent interaction in this supramolecule. The scanning results of the potential energy surface (PES) showed that the rotational barrier of C18 in OPP is extremely small, implying the possibility of the supramolecular complex as an ultrafast molecular rotator. Molecular dynamics (MD) simulations confirmed that C18 and OPP can spontaneously assemble into up to 1:2 ring-in-ring host-guest complexes, and C18 can rotate at an ultrahigh speed in OPP at ambient temperature. The thermodynamic parameters of the nanorotator at different temperatures were also investigated to determine the thermal stability of 2C18@OPP. Such assemble is the first example of two C18 molecules being encapsulated simultaneously to realize a dual-motor nanorotator and promises to open new avenues for the construction of complicated molecular machines as well as the controllable storage of C18.