Self-assembling cyclobis(paraquat-4,4'-biphenylene)

Abstract

The template-directed syntheses of the bipyridinium-based cyclophanes cyclobis(paraquat-p-phenylene) and cyclobis(paraquat-4,4'-biphenylene) can be achieved by employing π-electron rich hydroquinone-based and ferrocene-based templates. By employing macrocyclic hydroquinone-based polyether templates, [2]catenanes and [3]catenanes, in which the bipyridinium-based cyclophane is mechanically-interlocked with the macrocyclic template(s), can be self-assembled in solution. The introduction of ester functions within these polyether chains of the macrocyclic templates provides the possibility of degrading the catenated structure via ester hydrolysis, thus, releasing the tetracationic cyclophane originally trapped within the catenane. The use of ferrocene-based templates provides a more efficient way to synthesise the bipyridinium-based cyclophane incorporating bitolyl spacers. In particular, the use of a 1,1'-disubstituted polyether ferrocene derivative provides the possibility of obtaining the tetracationic cyclophane, cyclobis(paraquat-4,4'-biphenylene) - accessible only in very low yields, without the use of a template - on a preparative scale.