Stability constants: comparative study of fitting methods. Determination of second‐order complexation constants by 23Na and 7Li NMR chemical shift titration
Stability constants: comparative study of fitting methods. Determination of second‐order complexation constants by 23Na and 7Li NMR chemical shift titration
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稳定性常数：23Na 和 7Li NMR 化学位移滴定法测定二级络合常数的比较研究。
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
E. Eyring
中科院分区：
文献类型：
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作者：
Marilyn C. Masiker;C. Mayne;E. Eyring
核磁共振化学位移滴定法作为一种测定稳定常数的方法已被广泛应用。涉及金属配体络合的体系已经用许多方法进行了研究。通过不同的实验方法（如量热法和离子选择电极滴定法）获得的稳定性常数报告值存在显着差异；核磁共振化学位移滴定也不总是产生一致的结果。不同的研究人员对同一系统得到了不同的结果，结果相差多达一个数量级。化学位移数据通常是根据一组溶液中金属和配体的浓度比绘制的。在本研究中使用了一种非线性最小二乘拟合方法，该方法使用三次方程的解析解来计算自由配体的平衡浓度，并与文献中使用的方法进行了比较。报道了LiClO4:12‐crown‐4体系在乙腈中的二级缔合常数和NaClO4:12‐crown‐4体系在甲醇中的二级缔合常数。考虑了1:1和1:2金属配体配合物的形成。LiClO4:12‐crown‐4乙腈体系之前已经通过核磁共振滴定法进行了研究，但在该研究中只考虑了1:1的络合。这项研究提供了令人信服的证据，证明1:1和1:2的配合物至少在锂体系中是重要的。用蒙特卡罗方法对从化学位移到稳定常数的误差传播进行了研究，结果表明，数据分析方法的选择可能在一定程度上导致差异，而且模型的非线性性质会极大地影响稳定常数的误差极限。版权所有©2006约翰威利父子有限公司
NMR chemical shift titration has been widely used as a method for the determination of stability constants. Systems involving metal‐ligand complexation have been investigated using a number of methodologies. There are significant differences in the values reported for stability constants obtained by different experimental methods, such as calorimetry and ion selective electrode (ISE) titrations; nor has NMR chemical shift titration always yielded consistent results. Different researchers have obtained different results for the same system with results differing by as much as an order of magnitude. The chemical shift data are generally plotted against the concentration ratio of the metal and ligand for a set of solutions. A nonlinear least squares fitting method using an analytical solution of the cubic equation for the equilibrium concentration of the free ligand is used in this study and compared with methods used in the literature. Second‐order association constants for the LiClO4:12‐crown‐4 system in acetonitrile and the NaClO4:12‐crown‐4 system in methanol are reported. Formation of both 1:1 and 1:2 metal‐ligand complexes are considered. The LiClO4:12‐crown‐4 acetonitrile system had been investigated previously by NMR titration but only 1:1 complexation was considered in that study. This study provides convincing evidence that both 1:1 and 1:2 complexes are important, at least, in the lithium system. A Monte Carlo investigation of the propagation of errors from the chemical shifts to the stability constants shows that the choice of data analysis methods may, in part, contribute to discrepancies and that the nonlinear nature of the model can dramatically affect the error limits on the stability constants. Copyright © 2006 John Wiley & Sons, Ltd.
影响因子：
3.8
作者：
Huang, CY;Zhou, RX;Chock, PB
通讯作者：
Chock, PB