Hydrazone exchange: a viable route for the solid-tethered synthesis of [2]rotaxanes

Controlled and complete assembly of supramolecular systems on solid supports is a challenge that would elevate the function of interlocked architectures. Building on the success of other dynamic covalent synthetic methods, we present hydrazone exchange as a strategy to improve the formation of rotaxanes in solution and on solid surfaces. Solution-state analogues containing naphthalenediimide (NDI) or bipyridinium motifs and 1,5-dinaphtho[38]crown-10 were initially prepared to establish ideal conditions for maintaining thermal equilibrium throughout the exchange reaction. Solid-state rotaxanes were synthesised on hydrazide-functionalised TentaGel™ polymer resins and analysed with HR MAS 1H NMR spectroscopy. Surface rotaxane functionalisation of 80% was achieved for the NDI rotaxane, which is significantly higher than previously reported with either dynamic covalent or traditional irreversible synthetic strategies.