Molecular structure and electrochemical behavior of uranyl(VI) complex with pentadentate Schiff base ligand: prevention of uranyl(V) cation-cation interaction by fully chelating equatorial coordination sites.
Molecular structure and electrochemical behavior of uranyl(VI) complex with pentadentate Schiff base ligand: prevention of uranyl(V) cation-cation interaction by fully chelating equatorial coordination sites.
复制标题
DOI：
10.1021/ic902225f
复制
发表时间：
2010-01
影响因子：
4.6
通讯作者：
Koichiro Takao;Masaru Kato;Shinobu Takao;A. Nagasawa;G. Bernhard;C. Hennig;Y. Ikeda
中科院分区：
文献类型：
--
作者：
Koichiro Takao;Masaru Kato;Shinobu Takao;A. Nagasawa;G. Bernhard;C. Hennig;Y. Ikeda
以五齿Schiff碱（N，N '-二亚甲基二乙烯三胺盐= saldien（2-））为配体，合成了U（VI）配合物，并以此为原料合成了稳定的U（V）配合物. U（V）O（2）（+）阳离子-阳离子相互作用，并发现在三个不同的晶相。其中两个在正交晶系和单斜晶系中具有相同的组成U（VI）O（2）（saldien）xDMSO（DMSO =二甲基亚砜，分别为1a和1c）。1a和1c中的DMSO分子没有显示出与U（VI）O（2）（saldien）的任何配位，但它只是作为溶剂存在于晶体结构中。其他分离的晶体仅由U（VI）O（2）（saldien）组成，没有掺入溶剂分子（1b，正交晶系）。在1c中观察到与1a和1b不同的配位saldien（2-）构象。构象异构体在溶液中通过苯环的翻转运动相互交换。U（VI）O（2）（saldien）的五角赤道配位即使在强路易斯碱溶剂DMSO和N，N-二甲基甲酰胺中也保持不变。U（VI）O（2）（saldien）在DMSO中的循环伏安法表明，U（VI）O（2）（saldien）的氧化还原反应是准可逆的，没有任何后续反应。紫外-可见-近红外光谱电化学技术测定的电子化学计量比接近1，表明U（VI）O（2）（saldien）的还原产物为[U（V）O（2）（saldien）]（-），在DMSO中稳定。[U（V）O（2）（saldien）]（-）/U（VI）O（2）（saldien）在DMSO中的标准氧化还原电位为-1.584 V vs Fc/Fc（+）。该U（V）配合物具有5 f（1）组态的f-f跃迁和轴向氧向U（5+）的电荷转移的特征吸收带。
The U(VI) complex with a pentadentate Schiff base ligand (N,N'-disalicylidenediethylenetriaminate = saldien(2-)) was prepared as a starting material of a potentially stable U(V) complex without any possibility of U(V)O(2)(+)...U(V)O(2)(+) cation-cation interaction and was found in three different crystal phases. Two of them had the same composition of U(VI)O(2)(saldien) x DMSO in orthorhombic and monoclinic systems (DMSO = dimethyl sulfoxide, 1a and 1c, respectively). The DMSO molecule in both 1a and 1c does not show any coordination to U(VI)O(2)(saldien), but it is just present as a solvent in the crystal structures. The other isolated crystals consisted only of U(VI)O(2)(saldien) without incorporation of solvent molecules (1b, orthorhombic). A different conformation of the coordinated saldien(2-) in 1c from those in 1a and 1b was observed. The conformers exchange each other in a solution through a flipping motion of the phenyl rings. The pentagonal equatorial coordination of U(VI)O(2)(saldien) remains unchanged even in strongly Lewis-basic solvents, DMSO and N,N-dimethylformamide. Cyclic voltammetry of U(VI)O(2)(saldien) in DMSO showed a quasireversible redox reaction without any successive reactions. The electron stoichiometry determined by the UV-vis-NIR spectroelectrochemical technique is close to 1, indicating that the reduction product of U(VI)O(2)(saldien) is [U(V)O(2)(saldien)](-), which is stable in DMSO. The standard redox potential of [U(V)O(2)(saldien)](-)/U(VI)O(2)(saldien) in DMSO is -1.584 V vs Fc/Fc(+). This U(V) complex shows the characteristic absorption bands due to f-f transitions in its 5f(1) configuration and charge-transfer from the axial oxygen to U(5+).