Aqueous Assembly of Zwitterionic Daisy Chains

The synthesis and characterization of zwitterionic molecular [c2]- and [a2]-daisy chains are described, relying on recognition of a positively charged cyclophane and a negatively charged oligo(phenylene-ethynylene) (OPE) rod in aqueous medium. For this purpose, syntheses of an acetylene-functionalized macrocyclic receptor and a water-soluble OPE-rod as the guest component are presented, from which a heteroditopic daisy chain monomer was prepared. This monomer aggregated strongly in water/methanol 4:1 and formed molecular daisy chains, which were isolated as interlocked species from a stoppering reaction at 1 mm concentration. The cyclic dimer [c2] was the main product with an isolated yield of 30 % and consisted of a mixture of diastereomers, as evidenced by H-1 NMR spectroscopy.