Controlled dethreading/rethreading of a scorpion-like pseudorotaxane and arelated macrobicyclic self-complexing system

A scorpion-like pseudorotaxane (1 . H2+), composed of a macrocyclic polyeth er containing a 1,5-dioxynaphthalene (1,5-DON) and a 1,3-dioxybenzene (1,3- DOB) electron-donor unit, the latter bearing a 4,4'-bipyridinium electron-a cceptor tail, underwent threading/dethreading motions under control of (i) solvent polarity and (ii) solution acidity. Furthermore, the complexation o f 1 . H2+ with the trans-1,2-bis(1-benzyl-4-pyridinio)ethylene electron acc eptor can be acid/base controlled. The spectroscopic properties of a relate d macrobicyclic compound 2(4+) (comprised of an electron-donor and an elect ron-acceptor macrocycle that share a benzene ring) have also been investiga ted. The results obtained for 2(4+) are consistent with the presence of int ramolecular self-complexed species where the electron-donor macrocycle is t hreaded through the electron-acceptor one. Electrochemical experiments conf irm the self-complexing structures of 1 . H2+ and 2(4+). It seems likely th at both compounds undergo decomplexation upon electrochemical stimulation.