Branched [n]rotaxanes (n = 2–4) from multiple dibenzo-24-crown-8 ether wheels and 1,2-bis(4,4′-dipyridinium)ethane axles

To investigate the possibility of incorporating the 1,2-bis(pyridinium)ethane[subset or is implied by]24C8 [2]pseudorotaxane motif into dendrimer like macromolecules, a series of branched [n]rotaxanes were prepared employing multiple dibenzo-24-membered crown ether wheels with various aromatic core structures and the 1,2-bis(4,4'-dipyridinium)ethane axle. Yields of branched [2]-, [3]- and [4]rotaxanes were dependent on the size of the core and the relative proximity of the crown ethers arranged around the core unit.