One-pot synthesis of donor-acceptor [2]rotaxanes based on cryptand-paraquat recognition motif.

Two novel cryptand-based [2]rotaxanes were synthesized by a facile one-pot reaction from three neutral precursors: easily accessible cryptand host 1 and commercially available 4,4'-bipyridine and 3,5-di-tert-butylbenzyl bromide. Their structures were confirmed by (1)H NMR, 2D NMR, HRMS and X-ray analysis. Moreover, two [2]pseudorotaxanes based on the same cryptand hosts and dibenzyl viologen guest 3 were also demonstrated both in solution and in the solid state, which are different from previously reported [3]pseudorotaxane-like complexes formed by dimethyl viologen guest 2 and the cryptands.