Direct Synthesis of an Oligomeric Series of Interlocked, Cyclodextrin-Based [c2]Daisy Chains

Despite their anticipated utility and aesthetic appeal, attempts to prepare extended molecular daisy chains have been thwarted by preferential formation of cyclic dimers ([c2]-rotaxanes). Previously, to circumvent this limitation, an alternative type of molecular chain has been synthesized by linking pre-prepared [c2]rotaxanes already interlocked with bulky capping groups. Instead of this stepwise approach, here we describe the direct self-assembly of dimeric complexes and their in situ oligomerization, which simultaneously interlocks the dimers so that no prior capping of the complexes is required. Eight individual supramolecular species, including a tetramer, hexamer, octamer and decamer series, have been isolated and characterized. The decamer is derived from 16 molecular components, through ten highly selective reactions of six equivalents of the bifunctional linking reagent with five self-assembled dimeric cyclodextrin inclusion complexes, all in one pot.