Open and closed states of a porphyrin based molecular turnstile

Abstract

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.