Acid-base actuation of [c2]daisy chains

Abstract

A versatile synthetic strategy, which was conceived and employed to prepare doubly threaded, bistable [c2]dalsy chain compounds, Is described. Propargyl and 1-pentenyl groups have been grafted onto the stoppers of [c2]dalsy chain molecules obtained using a template-directed synthetic protocol. Such [c2]dalsy chain molecules undergo reversible extension and contraction upon treatment with acid and base, respectively. The dialkyne-functionalized [c2]dalsy chain (AA) was subjected to an [AA+BB] type polymerization with an appropriate diazide (BB) to afford a linear, mechanically Interlocked, main-chain polymer. The macromolecular properties of this polymer were characterized by chronocoulometry, size exclusion chromatography, and static light-scattering analysis. The acid-base switching properties of both the monomers and the polymer have been studied In solution, using H NMR spectroscopy, UV/vls absorption spectroscopy, and cyclic voltammetry. The experimental results demonstrate that the functionalized [c2]daisy chains, along with their polymeric derivatives, undergo quantitative, efficient, and fully reversible switching processes In solution. Kinetics measurements demonstrate that the acid/base-promoted extension/contraction movements of the polymeric [c2]daisy chain are actually faster than those of Its monomeric counterpart. These observations open the door to correlated molecular motions and to changes In material properties. 2009 American Chemical Society.