Abstract

The stability constants cobalt(II) glycylglycinate complexes in a water–DMSO solvent of variable composition have been determined by the potentiometric titration method at 298 K and a solution ionic strength of 0.1 M against the background of sodium perchlorate. It has been established that an increase in the content of DMSO in solution leads to an increase in the stability of cobalt(II) glycylglycinate complexes. Using literature data, we calculated the change in the Gibbs energy of the Co²⁺ ion transfer from water to its mixtures with DMSO and estimated the contributions of the transsolvation of the reagents in a water–DMSO solvent to the change in the Gibbs energy of the reaction of cobalt(II) glycylglycinate formation. It has been shown that a change in the Gibbs energy of transsolvation of a metal ion in a water–DMSO solution counteracts an increase in the equilibrium constant of the complex formation reaction, while a change in the solvation state of the ligand and the complex species, on the contrary, contributes to an increase in the stability of the complex.

中文翻译：

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钴 (II) 配合物与甘氨酸离子的稳定性随水-二甲亚砜溶剂组成的变化

摘要

已通过电位滴定法在 298 K 和 0.1 M 的溶液离子强度以高氯酸钠为背景下测定了可变组成的水-DMSO 溶剂中的稳定常数甘氨酰甘氨酸钴 (II) 配合物。已经确定溶液中 DMSO 含量的增加会导致甘氨酰甘氨酸钴 (II) 复合物的稳定性增加。利用文献数据，我们计算了Co ^{2+的吉布斯能量变化}离子从水转移到其与 DMSO 的混合物中，并估计了试剂在水-DMSO 溶剂中的转移对甘氨酰甘氨酸钴 (II) 形成反应的吉布斯能量变化的贡献。已经表明，金属离子在水-DMSO 溶液中的转移溶剂化吉布斯能的变化抵消了络合物形成反应的平衡常数的增加，而配体和络合物物质的溶剂化状态的变化，相反，有助于增加复合物的稳定性。