Solvent Extraction of Transition Metal Cations by Calixarene-Based Cyclic Ligands
作者:Takeshi Nagasaki、Seiji Shinkai
DOI:10.1246/bcsj.65.471
日期:1992.2
Calix[n]arenes (n = 4 and 6) bearing carboxyl groups (1n), hydroxamate groups (2n), and dimethylamino groups (3n) on the lower rim and their monomeric analogs (11, 21, and 31) were synthesized to estimate selective extraction of transition metal cations from the aqueous phase to the organic (chloroform) phase. 14 and 16 showed the selectivity toward Fe3+, Cu2+, Zn2+, and Pd2+. In particular, 16 showed the unusually high extractability toward Fe3+. 24 and 26 showed the selectivity toward Fe3+, Cu2+, and Pd2+, but only Fe3+ was extracted to a significant extent at pH 2.2, the order of the extractability being 26 > 24 > 21. 34 and 36 showed the selectivity toward Pd2+ and Pt4+. The detailed examination of the extraction mechanism established that the ion-pair extraction mechanism is operative in Pt4+ (i.e., extracted as [PtCl6]2−) whereas both the ion-pair extraction mechanism and the chelatecomplex extraction mechanism are operative in Pd2+ (i.e., extracted as [PdCl4]2− in the ion-pair extraction mechanism). The results indicate that the ligand groups circularly arranged on the lower rim of the calixarene cavity form novel binding sites for transition metal cations.
我们合成了下缘带有羧基(1n)、羟基(2n)和二甲基氨基(3n)的钙[n]烯(n = 4 和 6)及其单体类似物(11、21 和 31),以估计它们对过渡金属阳离子从水相萃取到有机相(氯仿)的选择性。14 和 16 对 Fe3+、Cu2+、Zn2+ 和 Pd2+ 具有选择性。其中,16 对 Fe3+ 的萃取率异常高。24 和 26 显示了对 Fe3+、Cu2+ 和 Pd2+ 的选择性,但在 pH 值为 2.2 时,只有 Fe3+ 被大量萃取,萃取率的顺序为 26 > 24 > 21。34 和 36 对 Pd2+ 和 Pt4+ 具有选择性。对萃取机理的详细研究表明,离子对萃取机理在 Pt4+ 中起作用(即以 [PtCl6]2- 的形式萃取),而离子对萃取机理和螯合物萃取机理在 Pd2+ 中都起作用(即在离子对萃取机理中以 [PdCl4]2- 的形式萃取)。结果表明,在卡利卡尼空腔下缘环形排列的配体基团形成了过渡金属阳离子的新型结合位点。