Dipartimento di Chimica Generale, Università di Pavia via Taramelli 12, Pavia, Italy.
Chemistry. 2011 May 16;17(21):5972-81. doi: 10.1002/chem.201003411. Epub 2011 Apr 6.
In this work, we compare the anion-binding capabilities of receptors 1-5, characterized by similar structures, but possessing different hydrogen-bond-donor moieties (urea, squaramide, and sulfonamide). The presence of chromophoric substituents on the receptor's skeleton allowed the determination of association constants by performing UV/Vis titrations with the investigated anions on solutions of the receptors in pure acetonitrile. Additional quantitative studies of the anion-binding properties of receptors 1-5 were performed by isothermal titration calorimetry (ITC). The experimental results indicated that 1 and 2 formed 1:1 hydrogen-bonded complexes with most of the anions investigated. In the case of receptors 3-5, the formation of the 1:1 adduct was observed only with anions of low basicity (i.e., chloride, bromide, iodide, and hydrogen sulfate). With more basic anions (i.e., acetate and dihydrogen phosphate), both spectrophotometric and ITC titrations accounted for the deprotonation of the sulfonamide group, involving the formation of the conjugated base of the receptor.
在这项工作中，我们比较了受体 1-5 的阴离子结合能力，它们具有相似的结构，但具有不同的氢键供体部分（脲、脒和磺酰胺）。受体骨架上的发色取代基的存在允许通过在纯乙腈溶液中进行受体与研究阴离子的 UV/Vis 滴定来确定结合常数。通过等温滴定量热法 (ITC) 对受体 1-5 的阴离子结合性质进行了额外的定量研究。实验结果表明，1 和 2 与大多数研究的阴离子形成了 1:1 的氢键复合物。对于受体 3-5，仅观察到与低碱性阴离子（即氯、溴、碘和硫酸氢根）形成 1:1 加合物。对于更碱性的阴离子（即醋酸盐和磷酸二氢盐），分光光度法和 ITC 滴定都表明磺酰胺基团发生去质子化，涉及受体共轭碱的形成。
