Dynamic donor–acceptor [2]catenanes

Donor-acceptor [2]catenanes based on cyclobis(paraquat-p-phenylene) as the pi-acceptor ring have been used prominently in the construction of functional molecular devices. We report here their thermodynamically controlled synthesis from isolated pi-donor and pi-acceptor rings under the catalytic influence of tetra butylammonium iodide. The initial nucleophilic attack of iodide ion, which opens up the pi-acceptor ring, is followed by complexation to the pi-donor ring and the subsequent catenation of the pi-donor ring by the pi-acceptor ring [2]catenane. The reaction is general in scope and proceeds in high yields, without giving rise to side-products.