Towards the Stepwise Assembly of Molecular Borromean Rings: A Donor-Acceptor Ring-in-Ring Complex

the assembly of molecular borromean rings from constitutionally independent rings in a stepwise manner depends on the preparation of robust "ring-in-ring" complexes. the π-electron rich macrocycle bis-1,5-dinaphtho[50]crown-14 (1) is shown to form a donor-acceptor ring-in-ring complex with the π-electron poor cyclophane cyclobis(paraquat-4,4'-biphenylene) (24 + ) in solution. in the crystal superstructure of [12]·4pf6, ch···o interactions between the polyether loops of 1 and the bipyridinium units of 24 + could disfavor the threading of dialkylammonium components of a third ring.