Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK 5230 Odense M, Denmark.
Org Biomol Chem. 2019 Feb 27;17(9):2432-2441. doi: 10.1039/c9ob00085b.
The rate at which the macrocyclic cyclobis(paraquat-p-phenylene) ring of a bistable [2]rotaxane moves from a tetrathiafulvalene station to an oxyphenylene station upon oxidation of the tetrathiafulvalene station is found to be increased in the presence of added salts. Compared to the salt-free case, 0.1 M solutions of a series of tetraalkylammonium hexafluorophosphate salts (R4N·PF6, R = H, Me, Et or n-Bu) and of tetrabutylammonium perchlorate (n-Bu4N·ClO4) all afford an increased switching rate, which is largest in the case of n-Bu4N·ClO4 with smaller anions. Variation in the size of the ammonium cation has no significant effect. These results indicate that the addition of excess ions can be used as an accelerator to speed up shuttling processes in rotaxanes and catenanes based on the mobile cyclobis(paraquat-p-phenylene) ring, and that the choice of anion offers a convenient means of controlling the extent of this effect.
双稳态[2]轮烷中环双（对亚甲基-paraquat-p-亚苯基）大环从四硫富瓦烯站迁移到氧亚苯基站的速率在氧化四硫富瓦烯站时会加快，在添加盐的情况下发现这一速率会加快。与无盐情况相比，一系列四烷基铵六氟磷酸盐（R4N·PF6，R = H、Me、Et 或 n-Bu）和四丁基高氯酸盐（n-Bu4N·ClO4）的 0.1 M 溶液都提供了更快的切换速率，其中以具有较小阴离子的 n-Bu4N·ClO4 情况的速率增加最大。铵阳离子的大小变化没有明显影响。这些结果表明，添加过量离子可用作加速剂，以加快基于可移动环双（对亚甲基-paraquat-p-亚苯基）大环的轮烷和索烃中的穿梭过程，并且阴离子的选择提供了控制这种效应程度的便捷手段。
