Self-assembly of a [2]pseudorota[3]catenane in water.

A donor-acceptor [3]catenane incorporating two cyclobis(paraquat-p-phenylene) rings linked together by a dinaphtho[50]crown-14 macrocycle possesses a π-electron-deficient pocket. Contrary to expectation, negligible binding of a hexaethylene glycol chain interrupted in its midriff by a π-electron-rich 1,5-dioxynaphthalene unit was observed in acetonitrile. However, a fortuitous solid-state superstructure of the expected 1:1 complex revealed its inability to embrace any stabilizing [C-H···O] interactions between the clearly unwelcome guest and the host reluctantly accommodating it. By contrast, in aqueous solution, the 1:1 complex becomes very stable thanks to the intervention of hydrophobic bonding.