Controlling Translational Isomerism in [2]Catenanes

摘要

The recognition processes that lead to the self-assembly of [2]catenanes are controlled by the information stored in the molecular components which are constructed from "preprogramed" starting materials. This information is trapped within the [2]catenanes molecules whose properties are quite different from those of their individual molecular components. The study of phenomena such as translational isomerism, a structural characteristic of many of these intriguing molecules, rnay provide insight intothe recognition processes that operate during their formation and subsequently in their molecular states. Furthermore, the control of the translational isomerism in catenanes is important in demcnstrating their chemical properties and for predicting possible applications. Some recent examples illustrate the progress that has been made already toward the construction of controllable catenanes and rotax-anes. In our own research laboratory, after the [2]catenane 1-4PF_6 had been self-assembled, the [2]catenane 2-4 PF_6 was also synthesized by a template-directed approach in the belief that the different it-donating abilities of the 1,5-dioxynaph-thalene unit and the hydroquinone ring would influence strongly the relative populations of the rapidly equilibrating transla-tional isomers. In the event, the position of the equilibrium was found to be highly dependent on the dielectric constant of the medium in which the [2]catenane was dissolved.