Click‐coupling of anthraquinone dyes with β ‐cyclodextrin: formation of polymeric superstructures

Two novel cyclodextrin‐modified anthraquinone dyes were synthesized and investigated for their complexation behaviour and formation of superstructures. Therefore, 1‐fluoro‐4‐ N ‐(propargylamino)anthraquinone and 1,4‐bis(propargyloxy)anthraquinone were prepared via nucleophilic aromatic displacement and subsequently covalently ‘click‐coupled’ in a copper(I)‐catalysed azide–alkyne cycloaddition with β ‐cyclodextrin monoazide. Both the propargyl‐modified precursor and the click‐coupled anthraquinone dyes were evaluated as hosts and guests, respectively, in β ‐cyclodextrin interactions. The anthraquinone dye bearing two cyclodextrins, 1,4‐bis((1‐ β ‐cyclodextrin‐1 H ‐1,2,3‐triazol‐5‐yl)methoxy)anthraquinone, enables the reversible formation of supramolecular crosslinked poly[( N , N ‐dimethyl acrylamide)‐ co ‐( N ‐(ferrocenoylmethyl)acrylamide)] ( 11 ), whereas the monofunctionalized compound 1‐fluoro‐4‐(((1‐ β ‐cyclodextrin‐1 H ‐1,2,3‐triazol‐5‐yl)methyl)amino)anthraquinone can be supramolecularly linked to 11 resulting in coloured polymers. These features of β ‐cyclodextrin‐linked anthraquinone dyes can be verified with either 1 H 1 H NMR rotating frame nuclear Overhauser effect spectroscopy or the naked eye. © 2016 Society of Chemical Industry