Characterization of a slippage stopper for the 1,2-bis(pyridinium)ethane–[24]crown-8 ether [2]pseudorotaxane motif

Comparison of 1,2-bis(pyridinium)ethane axles containing iso-nicotinate esters (R=ethyl, iso-propyl, cyclohexyl, cycloheptyl) as the pyridinium unit shows that the cyclohexyl group provides a stopper size that allows slippage to be used as a method for pseudorotaxane/rotaxane formation employing dibenzo-24-crown-8 ether (DB24C8) as the wheel. Rates of complexation and decomplexation were measured in a number of solvent systems and the kinetic and thermodynamic parameters associated with the process reported.