Construction of rotacatenanes using rotaxane and catenane frameworks
The construction of novel mechanically interlocked structures has become a topic of great current interest due to the requirements of topology and their potential application in molecular machines and devices. Rotaxane and catenane as two basic topological frameworks can be used to construct the fused structures. In the current investigation, a class of novel ammonium backbones were synthesized. The ammonium group incorporated in the linear part of the molecule can be used for templating rotaxane formation while the macrocyclic part of the molecule can be used for templating catenane formation. Accordingly, they were subjected to dynamic covalent chemistry, resulting in a series of [n]rota[n]catenane structures (n = 2, 3, 4). In this process, the N-hetero crown ethers were installed on ammonium template sites of linear and macrocyclic components all at once by a template-directed clipping reaction. The results showed that these novel building blocks could be assembled with high efficiencies. Finally, this investigation provides a foundation for future studies aimed at constructing complicated integrated structures or polymers with multiple topological units.