A molecular turnstile T1 based on a luminescent pyridyl-benzimidazole stator and a rotor containing a pyridyl coordinating site is designed and its multi-step synthesis described. The turnstile T1 undergoes free rotation of the rotor around the stator. In the presence of Ag+ cation as an effector, the rotational movement is locked through simultaneous binding of the cation by both pyridyl coordinating sites. The dynamic reversible behaviour of the turnstile in solution was investigated by 1- and 2D-NMR spectroscopy and by absorption and emission spectroscopies.