Ligand Design Principle for Molecular Recognition and the Application to Separation Chemistry

离子大小识别与传统的有机配体被证明是由几个因素。第一种是基于施主原子之间的距离，即咬合尺寸。在6元环如β-二酮中的咬位大小不仅控制选择性，还控制配体的酸度。决定离子大小识别的第二个因素是螯合环的刚性。第三是由于配体的末端基团庞大而导致的配体间接触导致的螯合物的不稳定性，将这三个要求应用于稀土和13族金属离子的分离：采用大体积4-甲基吡啶对13族金属离子进行了有效的萃取分离，取代的酰基吡唑啉酮证实了这些因素对咬合大小和空间因素的作用的有效性。因此，上述结果证明了通过控制配体的咬合尺寸和/或产生配体内和配体间接触来设计对目标金属离子具有高选择性的配体的可能性。

Ion size recognition with conventional organic ligands was proved to be governed by several factors. The first is based on the distance between the donor atoms, that is, the bite size. Bite size in a 6-membered ring such as beta-diketone also governs not only the selectivity, but the acidity of the ligand. The second factor governing ion size recognition is the chelate ring rigidity. The third is the unstabilization of chelates based on the inter ligand contact, which is caused by bulky terminal group of the ligand.The application of the three requirments to the separation of rare earth and Group 13 metal ions was performed : The efficient extraction-separation of each metal ion in Group 13 by bulky 4-substituted acylpyrazolones confirms the validity of the factors on the role of the bite size and steric factors. The above results thus have proved the possibility of designing ligands of high selectivity for target metal ions by controlling the bite size of the ligand and/or creating intra- and interligand contacts.