Development of [2]-Catenane with Orthogonal Binding Chloride Template

Abstract

Developing a multi ion acceptor such as catenane, rotaxane and pseudorotaxane was carried out in an effort to overcome the number of binding sites in an ionic receptors that is composed of a single molecule. More than two supramolecules can form molecular complex through selfassembly by coordination. When the anion binding sites in each supramolecules form orthogonal complex, the binding sites provide three dimensional spaces. Anions of spherical, linear, triogonal planar and tetrahedral shapes can selectively form complex in such binding sites. Quite often the catenane and rotaxane were not obtained through a planned strategy. They were obtained as byproducts while synthesizing some other compounds. Since the structures of catenane and rotaxane are similar to DNA, they are drawing much attention in the study of biochemical structure. They can be utilized in the newly emerging field of controlling molecules in nano-scale such as molecular electronics, molecular mechanics and molecular self-assembly. But, due to the difficulties in their synthetic work, no much progress has been accomplished until recently. Anionic substrates have received little attention as potential templates in the formation of interlocked molecules, due to their varying geometries, low charge/radius ratios and pH dependence. Recently complexes with orthogonal ion binding sites were synthesized by coordinating derivatives of pyridinium chloride and isophthalamide from the fact that isophthalamide derivatives can recognize chloride. This study showed that rotaxanes and catenanes can be synthesized using anion templates. Beer and co-workers reported more advanced design of the anion template from the fact which the electron deficient and electron rich components are arranged so that π-π stacking is possible. Although catenanes were synthesized using other types of anion templates, still more research needs to be developed. Herein, we are reporting [2]-catenane using anion template and RCM reaction. The anion templation forms a pseudorotaxane assembly and a subsequent clipping reaction using RCM affords the catenane structure.