Open and closed states of a porphyrin based molecular turnstile

The molecular turnstile 1 composed of a stator based on an Sn(IV)-porphyrin bearing two sets of monodentate coordinating sites (pyridyl and benzonitrile) and a handle bearing a 2,6-pyridinediamide moiety as a tridentate unit was synthesised. In the absence of metal behaving as a blocking agent, the handle freely rotates around the stator (open state). In the presence of Pd(II), the closed state of the turnstile 1-Pd resulting from the simultaneous binding of the metal centre by both the dianionic tridentate site and one of the two pyridyl units is generated. The reaction of 1-Pd with the organometallic 2,6-diphenylpyridine Pt(II) complex 11 leads to the heterotrinuclear (Pt, Sn, Pd) species 13, resulting from the binding of the platinum complex by 1-Pd.