Zhang Zhicheng, Helms Gregory, Clark Sue B, Tian Guoxin, Zanonato PierLuigi, Rao Linfeng
Chemistry Department, Washington State University, Pullman, Washington 99164, USA.
Inorg Chem. 2009 Apr 20;48(8):3814-24. doi: 10.1021/ic8018925.
Within the pC(H) range of 2.5 to 4.2, gluconate forms three uranyl complexes UO(2)(GH(4))(+), UO(2)(GH(3))(aq), and UO(2)(GH(3))(GH(4))(-), through the following reactions: (1) UO(2)(2+) + GH(4)(-) = UO(2)(GH(4))(+), (2) UO(2)(2+) + GH(4)(-) = UO(2)(GH(3))(aq) + H(+), and (3) UO(2)(2+) + 2GH(4)(-) = UO(2)(GH(3))(GH(4))(-) + H(+). Complexes were inferred from potentiometric, calorimetric, NMR, and EXAFS studies. Correspondingly, the stability constants and enthalpies were determined to be log beta(1) = 2.2 +/- 0.3 and DeltaH(1) = 7.5 +/- 1.3 kJ mol(-1) for reaction (1), log beta(2) = -(0.38 +/- 0.05) and DeltaH(2) = 15.4 +/- 0.3 kJ mol(-1) for reaction (2), and log beta(3) = 1.3 +/- 0.2 and DeltaH(3) = 14.6 +/- 0.3 kJ mol(-1) for reaction (3), at I = 1.0 M NaClO(4) and t = 25 degrees C. The UO(2)(GH(4))(+) complex forms through the bidentate carboxylate binding to U(VI). In the UO(2)(GH(3))(aq) complex, hydroxyl-deprotonated gluconate (GH(3)(2-)) coordinates to U(VI) through the five-membered ring chelation. For the UO(2)(GH(3))(GH(4))(-) complex, multiple coordination modes are suggested. These results are discussed in the context of trivalent and pentavalent actinide complexation by gluconate.
在pC(H)为2.5至4.2的范围内，葡萄糖酸盐通过以下反应形成三种铀酰配合物UO₂(GH₄)⁺、UO₂(GH₃)(aq)和UO₂(GH₃)(GH₄)⁻：(1) UO₂²⁺ + GH₄⁻ = UO₂(GH₄)⁺，(2) UO₂²⁺ + GH₄⁻ = UO₂(GH₃)(aq) + H⁺，以及(3) UO₂²⁺ + 2GH₄⁻ = UO₂(GH₃)(GH₄)⁻ + H⁺。这些配合物是通过电位滴定、量热、核磁共振和扩展X射线吸收精细结构研究推断出来的。相应地，在I = 1.0 M NaClO₄且t = 25℃时，反应(1)的稳定常数和焓分别确定为logβ₁ = 2.2 ± 0.3和ΔH₁ = 7.5 ± 1.3 kJ mol⁻¹，反应(2)的logβ₂ = -(0.38 ± 0.05)和ΔH₂ = 15.4 ± 0.3 kJ mol⁻¹，反应(3)的logβ₃ = 1.3 ± 0.2和ΔH₃ = 14.6 ± 0.3 kJ mol⁻¹。UO₂(GH₄)⁺配合物通过双齿羧酸盐与U(VI)结合形成。在UO₂(GH₃)(aq)配合物中，羟基去质子化的葡萄糖酸盐(GH₃²⁻)通过五元环螯合与U(VI)配位。对于UO₂(GH₃)(GH₄)⁻配合物，提出了多种配位模式。这些结果在葡萄糖酸盐与三价和五价锕系元素络合的背景下进行了讨论。
