Formation of a Dicopper Platform Based Polyrotaxane Whose “<i>String</i>” and “<i>Bead</i>” Are Constructed from the Same Components

The combination of the dicopper platform [Cu2(L)2(THF)2] (1·2THF), where H2L is 1,1′-(1,3-phenylene)-bis-4,4-dimethylpentane-1,3-dione, and 1,4-bis­(4-pyridyl)­piperazine (bpp), afforded the first example of a one-dimensional polyrotaxane {[(1)­(μ2-bpp)]­[(1)2(bpp)2]}n whose “string” and “bead” are constructed from the same components. The bead of stoichiometry [(1)2(bpp)2] has a large rectangular cavity of dimensions 7.40 × 15.64 Å and is threaded onto a stair-like string of composition [(1)­(μ2-bpp)]n. The formation of the polyrotaxane is driven by π–π stacking between the string and the beads with precise electronic and steric complementarity between these components. A pathway for the formation of the polyrotaxane is proposed.