Cage Size Effects on the Rotation of Molecular Gyrotops with 1,4-Naphthalenediyl Rotor in Solution

1,4-Naphthalenediyl-bridged macrocages (2, 3, and 4) were synthesized as novel molecular gyrotops. Compound 2 (C14 chains) does not show rotation of the naphthalene ring about an axis in solution. The 1,4-naphthalenediyl moieties of compounds 3 (C16 chains) and 4 (C18 chains) show restricted and rapid rotation inside the cage in solution, respectively. Therefore, steric protective effects on the rotation of the rotor in molecular gyrotops can be controlled by changing the size of the cage.