Porphyrin-stoppered [3]- and [5]-rotaxanes

A dicopper(I)-complexed [3]-rotaxane was prepared in 34% yield by a transit ion-metal-templated strategy involving a bis-chelating molecular thread, ma crocycles incorporating the complementary chelating unit, and porphyrin sto ppers as key components. A tetracopper(I)-complexed [5]-rotaxane was obtain ed as a byproduct in 8% yield. Coordination chemistry was performed either at the 2,9-diphenyl-1, 10-phenanthroline (dpp) chelates or at the porphyrin stoppers. The latter were metalated by either Zn(II), Au(III), or Zn(II) a nd Au(III). Both Cu(I) template cations could be removed by competitive com plexation with CN- when at least one porphyrin stopper was complexed with A u(III), the other one being metalated with either Au(III) or Zn(II). This p rovided two strictly defined [3]-rotaxanes, in which the macrocycle and the molecular thread are not held together by metal coordination. Rather, deth reading is prevented by the bulky metalloporphyrin stoppers. Unexpectedly, when both stoppers were complexed with Zn(II), removal of the metal templat e in the same conditions as above yielded, very selectively, a copper(I)-co mplexed [3]-rotaxane containing only one metal-free macrocycle. The demetal ated bis-dpp site could be remetalated with Ag(I), affording, in good yield , a dinuclear (Ag(I), Cu(I))-complexed [3]-rotaxane, ended by Zn(II)-porphy rin blocking groups.