Crystal structure and solution dynamics of the lutetium(III) chelate of DOTA
Crystal structure and solution dynamics of the lutetium(III) chelate of DOTA
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DOI：
10.1016/0020-1693(96)05130-4
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发表时间：
1996-05-01
影响因子：
2.8
通讯作者：
Bombieri, G
中科院分区：
文献类型：
--
作者：
Aime, S;Barge, A;Bombieri, G
Na[Lu(DOTA)(H2O)]的X射线结构。 4H(2)O 由由钠阳离子平衡的 (-1) 复合阴离子组成。九配位 Lu(III) 以方形反棱镜排列方式与大环配体 DOTA 的四个氮原子和四个氧原子连接，并在封端位置配位水分子。在水溶液中，复合物以两种异构体形式存在，相对比例为 10:1，根据低温限制 C-13 NMR 谱进行评估。可变温度行为与两个动态过程的存在一致。一种方法是交换两种异构体的对映体对，并涉及大环烯基的协同构象变化和乙酸酯臂的旋转。另一个对应于两种异构体之间的相互转化。 LuDOTA 的变温 C-13 NMR 谱的完整线形分析可以对这两个过程进行定量评估。对映体化比异构化慢：相应计算的活化自由能分别为 65.9 +/- 1.2、62.7 +/- 2.0（交换主要可逆箭头次要）和 58.7 +/- 2.1 kJ mol(-1)（交换次要可逆箭头主要）。
The X-ray structure of Na[Lu(DOTA)(H2O)]. 4H(2)O consists of (-1) complex anions balanced by sodium cations. The nine-coordinate Lu(III) is linked to the four nitrogen and to four oxygen atoms of the macrocyclic ligand DOTA in a square antiprismatic arrangement with a coordinated water molecule in capping position. In aqueous solution the complex is present under two isomeric forms in the relative ratio of 10:1, as evaluated from the low temperature limiting C-13 NMR spectrum. The variable temperature behavior is consistent with the presence of two dynamic processes. One exchanges enantiomeric pairs for both isomers and involves concerted conformational changes of the ethylenic groups of the macrocyclic ring and rotation of the acetate arms. The other corresponds to the interconversion between the two isomers. Complete line-shape analysis of the variable-temperature C-13 NMR spectra of LuDOTA allowed a quantitative evaluation of the two processes. The enantiomerization is slower than the isomerization: the corresponding calculated free energies of activation are 65.9 +/- 1.2, 62.7 +/- 2.0 (exchange major reversible arrow minor) and 58.7 +/- 2.1 kJ mol(-1) (exchange minor reversible arrow major), respectively.