SELF-ASSEMBLY OF NOVEL [2]CATENANES AND [2]PSEUDOROTAXANES INCORPORATING THIACROWN ETHERS OR THEIR ACYCLIC ANALOGS

A series of pi electron rich macrocyclic polythioethers and their acyc lic analogues have been synthesized in good yields. The association co nstants for the complexation of the pi electron deficient bis(hexafluo rophosphate) bipyridinium-based salt, paraquat, by these macrocycles, as well as those for the complexation of corresponding acyclic compoun ds by the bipyridinium-based tetracationic cyclophane, cyclobis(paraqu at-p-phenylene), are significantly low-er than those observed in the c ase of the ''all-oxygen'' analogues. Nonetheless, yields as high as 86 % were recorded in the template-directed syntheses of [2]catenanes com posed of cyclobis(paraquat-p-phenylene) and the macrocyclic polythioet hers. Single-crystal X-ray crystallographic analyses of the [2]catenan es incorporating constitutionally unsymmetrical pi electron rich macro cyclic polythioethers revealed that, in all cases, the dioxyaromatic u nits are located inside the cavity of the tetracationic cyclophane com ponent in preference to the dithiaaromatic units. A similar selectivit y was observed in solution by variable-temperature H-1 NMR spectroscop y. However, inversion of the ratio between the two translational isome rs of the two [2]catenanes bearing 1,5-dithianaphthalene, as one of th eir pi electron rich ring systems, and either 1,4-dioxybenzene or 1,5- dioxynaphthalene, as the other, occurs upon increasing the temperature from -30 to +30 degrees C. These [2]catenanes fan be viewed as temper ature-responsive molecular snitches.