Min Tay Hui, Docker Andrew, Cheong Tse Yuen, Beer Paul D
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA, UK.
Current address: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China.
Chemistry. 2023 Aug 1;29(43):e202301316. doi: 10.1002/chem.202301316. Epub 2023 Jun 21.
A series of heteroditopic halogen bonding (XB) [2]rotaxanes were prepared via a combination of passive and active metal template-directed strategies. The ability of the [2]rotaxanes to bind alkali metal halide ion-pairs was investigated by extensive H NMR titration studies, wherein detailed analysis of cation, anion and ion-pair affinity measurements indicate dramatic positive cooperative enhancements in halide anion association upon either Na or K pre-complexation. This study demonstrates that careful consideration of multiple, parallel and competing binding equilibria is essential when interpreting observed H NMR spectral changes in ion-pair receptor systems, especially those which exhibit dynamic behaviour. Importantly, in comparison to XB [2]catenane analogues, these neutral XB heteroditopic [2]rotaxane host systems demonstrated that despite their relatively weaker cation and anion binding affinities, they exhibit a notably higher level of positive cooperativity for alkali metal halide ion-pair binding, highlighting the role of greater co-conformational adaptive behaviour in mechanically-bonded hosts for the purposes of charged species recognition.
通过被动和主动金属模板导向策略相结合的方式，制备了一系列异双位点卤键（XB）[2]轮烷。通过广泛的¹H NMR滴定研究，考察了[2]轮烷结合碱金属卤化物离子对的能力，其中对阳离子、阴离子和离子对亲和力测量的详细分析表明，在钠或钾预络合后，卤化物阴离子缔合存在显著的正协同增强效应。这项研究表明，在解释离子对受体系统中观察到的¹H NMR光谱变化时，尤其是那些表现出动态行为的系统，仔细考虑多个、平行和竞争的结合平衡至关重要。重要的是，与XB [2]连环烷类似物相比，这些中性XB异双位点[2]轮烷主体系统表明，尽管它们对阳离子和阴离子的结合亲和力相对较弱，但它们对碱金属卤化物离子对结合表现出明显更高水平的正协同性，突出了在机械键合主体中更大的共构象适应性行为在带电物种识别中的作用。
