Jiang J, Renshaw J C, Sarsfield M J, Livens F R, Collison D, Charnock J M, Eccles H
Department of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.,
Inorg Chem. 2003 Feb 24;42(4):1233-40. doi: 10.1021/ic020460o.
The solution chemistry of uranyl ion with iminodiacetate (IDA) and oxydiacetate (ODA) was investigated using NMR and EXAFS spectroscopies, potentiometry, and calorimetry. From the NMR and EXAFS data and depending on stoichiometry and pH, three types of metal:ligand complex were identified in solution in the pH range 3-7: 1:1 and 1:2 monomers; a 2:2 dimer. From NMR and EXAFS data for the IDA system and previous studies, we propose the three complex types are [UO(2)(IDA)(H(2)O)(2)], UO(2)(IDA)(2)(-), and (UO(2))(2)(IDA)(2)(mu-OH)(2)(-). From EXAFS spectroscopy, similar 1:1, 2:2, and 1:2 complexes are found for the ODA system, although (13)C NMR spectroscopy was not a useful probe in this system. For the 1:1 and 1:2 complexes in solution, EXAFS spectroscopy is ambiguous because the data can be fitted with either a long U-N/O(ether) value (ca. 2.9 A) suggesting 1,7-coordination of the ligand or a U-C interaction at a similar distance, consistent with terminal bidentate coordination. However, the NMR data of the IDA system suggest that 1,7-coordination is the more likely. The stability constants of the three complexes were determined by potentiometric titrations; the log beta values are 9.90 +/-, 16.42 +/-, and 10.80 +/- for the 1:1, 1:2, and 2:2 uranyl-IDA complexes, respectively, and 5.77 +/-, 7.84 +/-, and 4.29 +/- for the 1:1, 1:2, and 2:2 uranyl-ODA complexes, respectively. The thermodynamic constants for the complexes were calculated from calorimetric titrations; the enthalpy changes (kJ mol(-)(1)) and entropy changes (J K(-)(1) mol(-)(1)) of complexation for the 1:1, 1:2, and 2:2 complexes respectively are the following. IDA: 12 +/- 2, 230 +/- 8; 8 +/- 2, 151 +/- 9; -33 +/- 3, -283 +/- 11. ODA: 26 +/- 2, 198 +/- 12; 20 +/- 2, 106 +/- 8; -24 +/- 2; -219 +/- 8.
采用核磁共振（NMR）、扩展X射线吸收精细结构（EXAFS）光谱、电位滴定法和量热法研究了铀酰离子与亚氨基二乙酸（IDA）和氧化二乙酸（ODA）的溶液化学。根据NMR和EXAFS数据，并取决于化学计量比和pH值，在3 - 7的pH范围内，溶液中鉴定出三种类型的金属:配体配合物：1:1和1:2单体；2:2二聚体。根据IDA体系的NMR和EXAFS数据以及先前的研究，我们提出这三种配合物类型分别为[UO(2)(IDA)(H(2)O)(2)]、UO(2)(IDA)(2)(-)和(UO(2))(2)(IDA)(2)(μ-OH)(2)(-)。通过EXAFS光谱，在ODA体系中也发现了类似的1:1、2:2和1:2配合物，尽管(13)C NMR光谱在该体系中不是一个有用的探针。对于溶液中的1:1和1:2配合物，EXAFS光谱存在歧义，因为数据可以用长的U-N/O(醚)值（约2.9 Å）拟合，表明配体的1,7配位，或者在相似距离处的U-C相互作用，这与末端双齿配位一致。然而，IDA体系的NMR数据表明1,7配位更有可能。通过电位滴定法测定了三种配合物的稳定常数；1:1、1:2和2:2铀酰-IDA配合物的logβ值分别为9.90±、16.42±和10.80±，1:1、1:2和2:2铀酰-ODA配合物的logβ值分别为5.77±、7.84±和4.29±。通过量热滴定法计算了配合物的热力学常数；1:1、1:2和2:2配合物的络合焓变（kJ mol(-)(1)）和熵变（J K(-)(1) mol(-)(1)）分别如下。IDA：12±2，230±8；8±2，151±9；-33±3，-283±11。ODA：26±2，198±12；20±2，106±8；-24±2；-219±8。
