Arun Arya, Docker Andrew, Beer Paul D
Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK.
Chemistry. 2024 Dec 10;30(69):e202402731. doi: 10.1002/chem.202402731. Epub 2024 Oct 29.
The first examples of bis-squaramide axle containing [2]rotaxanes linked via rigid aryl and flexible alkyl spacers synthesised using copper(I) catalysed active metal template methodology are reported. The halide and oxoanion binding properties of the [2]rotaxanes in aqueous-organic solvent media are examined through extensive H-NMR titration experiments to investigate the impact of integrating multiple squaramide motifs on the anion binding capabilities of the interlocked receptors. These studies reveal that the bis-squaramide rotaxane host systems exhibit enhanced halide anion binding capabilities relative to a mono-squaramide axle functionalised rotaxane, demonstrating a rare anti-Hofmeister bias halide anion selectivity trend in aqueous-organic mixtures and highlighting the efficacy of the potent solvent shielded hydrophobic interlocked binding pocket created upon mechanical bond formation. Notably, employing a rigid aryl linker between the two squaramide motifs in the axle component enables the rotaxane host to exhibit strong and selective binding of tetrahedral oxoanions. Conversely, a flexible alkyl spacer facilitates trigonal oxoanion selective recognition by the bis-squaramide [2]rotaxane.
报道了首例通过铜（I）催化的活性金属模板法合成的、含有通过刚性芳基和柔性烷基间隔基连接的[2]轮烷的双方酰胺轴。通过广泛的氢核磁共振滴定实验，研究了[2]轮烷在水-有机溶剂介质中的卤化物和含氧阴离子结合性能，以考察整合多个方酰胺基序对互锁受体阴离子结合能力的影响。这些研究表明，相对于单一方酰胺轴功能化的轮烷，双 方酰胺轮烷主体体系表现出增强的卤化物阴离子结合能力，在水-有机混合物中显示出罕见的反霍夫迈斯特偏向卤化物阴离子选择性趋势，并突出了机械键形成时产生的有效溶剂屏蔽疏水互锁结合口袋的功效。值得注意的是，在轴组件的两个方酰胺基序之间采用刚性芳基连接体，能使轮烷主体对四面体含氧阴离子表现出强选择性结合。相反，柔性烷基间隔基有利于双 方酰胺[2]轮烷对三角含氧阴离子的选择性识别。
