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 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.