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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Outside the box: quantifying interactions of anions with the exterior surface of a cationic coordination cage
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Outside the box: quantifying interactions of anions with the exterior surface of a cationic coordination cage

机译：盒子外：量化阴离子的相互作用与阳离子协调笼的外表面

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We describe a study of the binding of anions to the surface of an octanuclear coordination cage H-W, which carries a 16+ charge, in aqueous solution. Anionic aromatic fluorophores such as fluorescein (and derivatives) and hydroxypyrene tris-sulfonate (HPTS) bind strongly to an extent depending on their charge and hydrophobicity. Job plots indicated binding of up to six such fluorescent anions to H-W, implying that one anion can bind to each face of the cubic cage, as previously demonstrated crystallographically with small anions such as halides. The quenching of these fluorophores on association with the cage provides the basis of a fluorescence displacement assay to investigate binding of other anions: addition of analyte (organic or inorganic) anions in titration experiments to an H-W/fluorescein combination results in displacement and restoration of the fluorescence from the bound fluorescein, allowing calculation of 1 : 1 binding constants for the H-W/anion combinations. Relative binding affinities of simple anions for the cage surface can be approximately rationalised on the basis of ease of desolvation (e.g. F- < Cl- < Br-), electrostatic factors given the 16+ charge on the cage (monoanions < dianions), and extent of hydrophobic surface. The interaction of a di-anionic pH indicator (bromocresol purple) with H-W results in a pK(a) shift, with the surface-bound di-anionic form stabilised by approximately 1 pK(a) unit compared to the non-bound neutral form due to the charge on the cage.
机译：我们描述了在水溶液中阴离子与八核配位笼H-W表面结合的研究，该笼携带16+电荷。阴离子芳香族荧光团，如荧光素（及其衍生物）和羟基芘三磺酸酯（HPTS），根据其电荷和疏水性在一定程度上结合强烈。工作曲线图显示，多达六个此类荧光阴离子与H-W结合，这意味着一个阴离子可以与立方笼的每个面结合，正如之前用小阴离子（如卤化物）从晶体学上证明的那样。这些荧光团与笼结合时的猝灭为荧光置换分析提供了基础，以研究其他阴离子的结合：在滴定实验中，将分析物（有机或无机）阴离子添加到H-W/荧光素组合中，可置换并恢复结合荧光素的荧光，允许计算H-W/阴离子组合的1:1结合常数。简单阴离子对笼表面的相对结合亲和力可以根据脱溶剂的容易程度（例如F-

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