Department of Physical Chemistry, Center for Research in Biological Chemistry and Molecular Materials (CIQUS), University of Santiago 15782 Santiago (Spain), Fax: (+34) 981595012.
Chemistry. 2013 Dec 23;19(52):17809-20. doi: 10.1002/chem.201302365. Epub 2013 Dec 9.
A microcalorimetric study on the inclusion of monovalent and divalent metal cations by p-sulfonatocalix[4]arene was performed. The thermodynamic parameters for the complexation of alkali metal cations and Ag(+) were obtained for the first time at neutral pH. The Na(+) cation is routinely present as counterion of the calixarene in neutral aqueous solution, and this must be taken into account in the determination of the thermodynamic parameters for the complexation of Na(+) and the other cations by considering a sequential or a competitive binding scheme. The ΔH° and ΔS° values show that the inclusion process is entropically driven, although an influence of the temperature on the complexation reaction indicates that the enthalpic term is also an important contributor. The results also reveal that enthalpy/entropy compensation balances the gain in one contribution against a corresponding loss in the other. The obtained thermodynamic data are in contrast to the results from previous microcalorimetric studies, which showed binding constants that were orders of magnitude smaller and complexations, which were in part enthalpically driven but which neglected the influence of the alkali metal counterions.
采用微量量热法研究了单价和二价金属阳离子与对磺酰基杯[4]芳烃的包合作用。首次在中性 pH 值下获得了碱金属阳离子与 Ag(+)络合的热力学参数。在中性水溶液中，Na(+)阳离子通常作为杯芳烃的抗衡离子存在，因此在确定 Na(+)和其他阳离子与杯芳烃络合的热力学参数时，必须考虑顺序或竞争结合方案，以考虑这一点。ΔH°和 ΔS°值表明，包合过程是熵驱动的，尽管温度对络合反应的影响表明焓项也是一个重要的贡献者。结果还表明，焓/熵补偿平衡了一个贡献的收益与另一个贡献的相应损失。获得的热力学数据与以前微量量热研究的结果形成对比，以前的研究表明，结合常数小几个数量级，部分络合是焓驱动的，但忽略了碱金属抗衡离子的影响。
