Rotaxanes with Chiral Stoppers and Photoresponsive Central Unit

All articles of this category Two new chiral and photoisomerizable rotaxanes ( 9m , 9p ) have been prepared, bearing the longest non-polymeric axle known so far: the axles ( 6m , 6p ) are polyether chains made of alternating triethyleneglycol/hydroquinone units, bearing a central meta- or para -azobenzoyl moiety and terminal tetraacetylglucoside stopper groups, while the wheel is the cyclobis( p -xylylene)bis(4,4′-bipyridinium) salt. Temperature dependent 1 H NMR measurements reveal that the translational process of the wheel across the azobenzene unit in the E -configuration is favoured for the para-rotaxane 9p compared to the meta isomer 9m . The azobenzene core of the free axles ( 6m , 6p ) and rotaxanes ( 9m , 9p ) undergo photochemical E/Z -isomerisation: from ( E ) to ( Z ) by irradiation at low wavelength and back from ( Z ) to ( E ) at high wavelength. Complete ( Z ) to ( E ) conversion was achieved by thermal isomerization. rotaxane - azobenzene isomerization - molecular recognition - chirality - supramolecular chemistry