Theoretical design of an ultrafast supramolecular rotor composed of carbon nano-rings.

The design of molecular rotors that can rotate at ultrahigh speeds is important for the development of artificial molecular machines. Based on theoretical calculations, we demonstrate that two kinds of carbon nano-rings, i.e. [n]cycloparaphenylenes ([n]CPP) and cyclo[18]carbon (C), can form an ultrafast ring-in-ring nano-rotor through π-π interaction. As a high-symmetry and low-barrier rotator, the rotational frequency of C in [11]CPP is close to the THz regime. At low temperatures, the motion of the [11]CPP:C system is purely rotational. As temperature increases, precession movements start to be observed and the motion resembles the behaviour of a gyroscope. The [11]CPP:C rotor can serve as a building block for bottom-up construction of more complex molecular machines.