Center for Supramolecular Chemistry & Catalysis and Department of Chemistry College of Science, Shanghai University, Shanghai, 200444, P. R. China.
Skaggs Institute for Chemical Biology and Department of Chemistry The Scripps Research Institute, La Jolla, California, 92037, USA.
Chem Asian J. 2022 Aug 1;17(15):e202200466. doi: 10.1002/asia.202200466. Epub 2022 Jun 15.
Groups on the upper rim of cavitands can play major roles in the recognition of small molecules. Water-soluble deep cavitands 1, 2 or 3 bearing the walls upper rim of imidazole, urea, and methyl urea, respectively, were synthesized and characterized as hosts of small-molecule guests. The vase forms of 1 or 2 are stabilized through H-bonding to solvent water molecules between adjacent walls. Various small alkyl organic molecules - alcohols, halides, cycloalkane derivatives and heterocycles - are efficiently bound in 1. For n-alcohols (C5 to C12), the -OH end is fixed at the upper rim and the alkyl parts are in the hydrophobic cavity. The longer alcohol guests (C7-C12) show coiling. Cycloalkane guests rotate rapidly on all 3 axes within the host cavity, while heterocycles show orientations placing their heteroatoms near the cavitand rim. Competition studies between alkyl chlorides, bromides and iodides showed preference for binding of iodides in 1. Competition between cavitands for hexyl halide guests halide showed the order 2>1>3.
主体上部边缘的基团在识别小分子方面起着重要作用。分别带有咪唑、脲和甲基脲的壁上部边缘的水溶性深穴状主体 1、2 和 3 被合成并表征为小分子客体的主体。通过相邻壁之间溶剂水分子的氢键，1 或 2 的花瓶形式得到稳定。各种小的烷基有机分子——醇、卤化物、环烷烃衍生物和杂环——在 1 中有效地结合。对于正醇（C5 至 C12），-OH 末端固定在上部边缘，烷基部分位于疏水性腔内。较长的醇客体（C7-C12）呈现卷曲。环烷烃客体在主体腔内绕所有 3 个轴快速旋转，而杂环则呈现出将其杂原子置于主体边缘附近的取向。在烷基氯化物、溴化物和碘化物之间的竞争研究中，发现 1 中碘化物的结合具有优先性。对于己基卤化物客体，主体之间的竞争显示出 2>1>3 的顺序。
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