Phosphorus(V) Porphyrin-Based Molecular Turnstiles

A new cationic molecular turnstile based on a P­(V) porphyrin backbone bearing two pyridyl interaction sites, one at the meso position of the porphyrin and the other on the handle connected to the porphyrin through P–O bonds, was designed and synthesized. The dynamic behavior of the turnstile 2, investigated by 1D and 2D 1H NMR techniques, showed that in the absence of an effector, the turnstile is in its open state and undergoes a free rotation of the rotor (the handle) around the stator (the porphyrin backbone). In the presence of an external effector such as Ag+ cation or H+, the turnstile is switched to its closed states 2-Ag+ and 2-H+, respectively. The locking/unlocking process is reversible and may be achieved by precipitation of AgBr upon addition of Et4NBr in the case of the silver-locked turnstile or by addition of Et3N in the case of the proton-locked turnstile.