Complex Formation of Thorium(IV) Ion with Glycyl−Glycine and Glycyl−Valine

The protonation equilibria of glycyl−glycine and glycyl−valine and their complex formation with thorium(IV) ions in aqueous solution were studied over a wide range of pH values (2 to 12) using a combination of potentiometric, cyclic voltametric, and spectrophotometric methods at constant temperature (25 °C) and constant ionic strength (0.1 mol·dm−3 sodium perchlorate). The redox properties of the species obtained by the cyclic voltametry technique have confirmed the spectrophotometric results. Least-squares regression calculations are consistent with the formation of the ThL3+, ThHL23+, and ThL22+ species for the studied systems, where L represents each peptide. Finally, the species concentrations were plotted at different pH values and discussed.

本研究在恒温（25 ℃）、恒定离子强度（0.1 mol·dm⁻³高氯酸钠）条件下，采用电位法、循环伏安法与分光光度法联用的方式，在宽pH范围（2~12）内，探究了甘氨酰-甘氨酸与甘氨酰-缬氨酸的质子化平衡，以及二者与四价钍离子在水溶液中的配位配合物形成过程。通过循环伏安技术得到的各物种氧化还原性质，验证了分光光度法的实验结果。最小二乘回归计算结果与所研究体系中ThL³⁺、ThHL₂³⁺及ThL₂²⁺配合物的形成情况相符，其中L代表各肽配体。最后，绘制了不同pH条件下各物种的浓度分布曲线并展开讨论。