Takao Koichiro, Ikeda Yasuhisa
Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1-N1-34, O-okayama, Meguro-ku, Tokyo 152-8550, Japan.
Inorg Chem. 2007 Mar 5;46(5):1550-62. doi: 10.1021/ic0611950. Epub 2007 Feb 7.
The molecular structures of UO2(salophen)L (L = DMF, DMSO) and a uranyl-salophen complex without any unidentate ligands (L) in solid and solution were investigated using single-crystal X-ray analysis and IR, 1H NMR, and UV-visible absorption spectroscopies. As a result, it was found that the uranyl-salophen complex without L is a racemic dimeric complex, [UO2(salophen)]2, in which the UO2(salophen) fragments are held together by bridging between one of the phenoxide oxygen atoms in salophen and the uranium in the other UO2(salophen) unit. Furthermore, it was spectrophotometrically demonstrated that [UO2(salophen)]2 retains its dimeric structure even in the noncoordinating solvents such as CH2Cl2 and CHCl3 and is in equilibrium with UO2(salophen)L {2UO2(salophen)L right arrow over left arrow [UO2(salophen)]2 + 2L}. The equilibrium constants and thermodynamic parameters of this equilibrium were evaluated from UV-visible absorption and 1H NMR spectral changes; log Kdim = -2.51 +/- 0.01 for L = DMF and solvent = CH2Cl2, log Kdim = -1.68 +/- 0.02 for L = DMF and solvent = CHCl3, log Kdim = -4.23 +/- 0.01 for L = DMSO and solvent = CH2Cl2, and log Kdim = -3.03 +/- 0.02 for L = DMSO and solvent = CHCl3. The kinetics of L-exchange reactions in UO2(salophen)L and enantiomer exchange of [UO2(salophen)]2 in noncoordinating solvents were also studied using NMR line-broadening method. As a consequence, it was suggested that the DMF-exchange reaction in UO2(salophen)DMF proceeds through two pathways (dissociative and associative paths) and that the predominant path of DMSO exchange in UO2(salophen)DMSO is the dissociative one. A sliding motion of the UO2(salophen) fragments was considered to be reasonable for the enantiomer-exchange mechanism of [UO2(salophen)]2. On the basis of the kinetic information for UO2(salophen)L and [UO2(salophen)]2, reaction mechanisms including the L-exchange reaction in UO2(salophen)L, the formation of [UO2(salophen)]2 from UO2(salophen)L, and the enantiomer exchange of [UO2(salophen)]2 are proposed.
采用单晶X射线分析以及红外光谱、核磁共振氢谱和紫外可见吸收光谱等方法，研究了UO₂(salophen)L（L = 二甲基甲酰胺、二甲基亚砜）以及不含任何单齿配体（L）的铀酰 - 水杨醛缩邻苯二胺配合物在固态和溶液中的分子结构。结果发现，不含L的铀酰 - 水杨醛缩邻苯二胺配合物是一种外消旋二聚体配合物[UO₂(salophen)]₂，其中UO₂(salophen)片段通过水杨醛缩邻苯二胺中一个酚氧原子与另一个UO₂(salophen)单元中的铀之间的桥连作用结合在一起。此外，通过分光光度法证明，即使在二氯甲烷和三氯甲烷等非配位溶剂中，[UO₂(salophen)]₂仍保持其二聚体结构，并与UO₂(salophen)L处于平衡状态{2UO₂(salophen)L ⇌ [UO₂(salophen)]₂ + 2L}。根据紫外可见吸收光谱和核磁共振氢谱的变化评估了该平衡的平衡常数和热力学参数；对于L = 二甲基甲酰胺且溶剂为二氯甲烷，log Kdim = -2.51 ± 0.01；对于L = 二甲基甲酰胺且溶剂为三氯甲烷，log Kdim = -1.68 ± 0.02；对于L = 二甲基亚砜且溶剂为二氯甲烷，log Kdim = -4.23 ± 0.01；对于L = 二甲基亚砜且溶剂为三氯甲烷，log Kdim = -3.03 ± 0.02。还使用核磁共振谱线展宽法研究了UO₂(salophen)L中L交换反应的动力学以及[UO₂(salophen)]₂在非配位溶剂中的对映体交换。结果表明，UO₂(salophen)二甲基甲酰胺中的二甲基甲酰胺交换反应通过两条途径（解离途径和缔合途径）进行，而UO₂(salophen)二甲基亚砜中二甲亚砜交换的主要途径是解离途径。认为UO₂(salophen)片段的滑动运动对于[UO₂(salophen)]₂的对映体交换机制是合理的。基于UO₂(salophen)L和[UO₂(salophen)]₂的动力学信息，提出了包括UO₂(salophen)L中的L交换反应、由UO₂(salophen)L形成[UO₂(salophen)]₂以及[UO₂(salophen)]₂的对映体交换在内的反应机制。
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