MOLECULAR MECCANO - 25 - SELF-ASSEMBLY OF FUNCTIONALIZED [2]CATENANESBEARING A REACTIVE FUNCTIONAL-GROUP ON EITHER ONE OR BOTH MACROCYCLICCOMPONENTS - FROM MONOMERIC [2]CATENANES TO POLYCATENANES

A series of mono- and difunctionalized [2]catenanes, incorporating a b ipyridinium-based cyclophane component interlocked with a dioxyarene-b ased macrocyclic polyether, have been self-assembled. The methodology relies upon the complementarity between the pi-electron-deficient and the pi-electron-rich macrocyclic components. Hydrogen-bonding interact ions between the acidic hydrogen atoms on the bipyridinium units and t he polyether oxygen atoms, as well as pi-pi stacking and edge-to-face T-type interactions between the complementary aromatic units, are resp onsible for these self-assembly processes. These [2]catenanes have bee n designed in order to locate one reactive functional group-either a h ydroxyl group or a carboxylic acid function-onto one or both macrocycl ic components. In principle, polymerization or copolymerization of the se monomeric [2]catenanes can be realized by condensations at the reac tive functional groups to generate main-chain, side-chain, and dendrit ic polycatenanes. Indeed, the versatility of this design logic has bee n demonstrated by some preliminary experiments. A main-chain oligo[2]c atenane incorporating 17 repeating units connected by urethane linkage s was synthesized by the condensation of a monomeric difunctionalized [2]catenane bearing one hydroxymethyl group on each of its two macrocy clic components with a diisocyanate derivative. The geometries adopted in the solid state by some of the monomeric [2]catenanes were examine d by single-crystal X-ray analyses. Interestingly, in the case of a mo nofunctionalized [2]catenane bearing one carboxylic acid group on its pi-electron-rich macrocyclic component, pseudobis[2]catenanes are obse rved in the solid state as a result of the formation of hydrogen-bonde d dimers between the carboxylic acid groups of adjacent molecules.