Two small molecular propellers and their rotational potential energy surfaces

Molecular propellers based upon the twisting of a disulfide bond are analyzed here as the locomotion source for fullerene nanoparticles. The HC(CCHSSHCC)(3)CH and related HC(CCHSSNC)(3)CH bicyclic compounds are optimized and linked to pyracyclene functioning as a model fullerene surface. It is shown that steric hinderance from the hydrogen atoms on both the bottom of the propeller blade and the linker to the fullerene surface can have significant effects on the rotational potential energy surface. Replacing the bottom CH groups on the molecular propeller with nitrogen atoms not only reduces these barriers significantly, but this action creates a strongly dipolar molecule in HC(CCHSSNC)(3)CH. Such a system would be responsive to and controllable with an external, rotating, magnetic or electric field. Endohedral fullerenes have known applications for targeted delivery, especially in nanomedicine. Providing further control with molecular propellers could enhance the feasibility and use of these technologies.