Self‐Assembly of Novel [2]Catenanes and [2]Pseudorotaxanes Incorporating Thiacrown Ethers or Their Acyclic Analogues

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Abstract
A series of π electron rich macrocyclic polythioethers and their acyclic analogues have been synthesized in good yields. The association constants for the complexation of the π electron deficient bis(hexafluorophosphate) bipyridinium‐based salt, paraquat, by these macrocycles, as well as those for the complexation of corresponding acyclic compounds by the bipyridinium‐based tetracationic cyclophane, cyclobis(paraquat‐p‐phenylene), are significantly lower than those observed in the case of the “all‐oxygen” analogues. Nonetheless, yields as high as 86% were recorded in the template‐directed syntheses of [2]catenanes composed of cyclobis(paraquat‐p‐phenylene) and the macrocyclic polythioethers. Single‐crystal X‐ray crystallographic analyses of the [2]catenanes incorporating constitutionally unsymmetrical π electron rich macrocyclic polythioethers revealed that, in all cases, the dioxyaromatic units are located inside the cavity of the tetracationic cyclophane component in preference to the dithiaaromatic units. A similar selectivity was observed in solution by variable‐temperature 1H NMR spectroscopy. However, inversion of the ratio between the two translational isomers of the two [2]catenanes bearing 1,5‐dithi‐anaphthalene, as one of their π electron rich ring systems, and either 1,4‐dioxy‐benzene or 1,5‐dioxynaphthalene, as the other, occurs upon increasing the temperature from –30 to +30 πC. These [2]catenanes can be viewed as temperature‐responsive molecular switches.

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