Self-assembly of functionalized [2]catenanes bearing a reactive functional group on either one or both macrocyclic components - From monomeric [2]catenanes to polycatenanes

Abstract

A series of mono- and difunctionalized [2]catenanes, incorporating a bipyridinium-based cyclophane component interlocked with a dioxyarene-based macrocyclic polyether, have been self-assembled. The methodology relies upon the complementarity between the π-electron-deficient and the π-electron-rich macrocyclic components. Hydrogen-bonding interactions between the acidic hydrogen atoms on the bipyridinium units and the polyether oxygen atoms, as well as π-π stacking and edge-to-face T-type interactions between the complementary aromatic units, are responsible for these self-assembly processes. These [2]catenanes have been designed in order to locate one reactive functional group-either a hydroxyl group or a carboxylic acid function - onto one or both macrocyclic components. In principle, polymerization or copolymerization of these monomeric [2]catenanes can be realized by condensations at the reactive functional groups to generate main-chain, side-chain, and dendritic polycatenanes. Indeed, the versatility of this design logic has been demonstrated by some preliminary experiments. A main-chain oligo[2]catenane incorporating 17 repeating units connected by urethane linkages was synthesized by the condensation of a monomeric difunctionalized [2]catenane bearing one hydroxymethyl group on each of its two macrocyclic components with a diisocyanate derivative. The geometries adopted in the solid state by some of the monomeric [2]catenanes were examined by single-crystal X-ray analyses. Interestingly, in the case of a monofunctionalized [2Jcatenane bearing one carboxylic acid group on its π-electron-rich macrocyclic component, pseudobis[2]catenanes are observed in the solid state as a result of the formation of hydrogen-bonded dimers between the carboxylic acid groups of adjacent molecules.