2価金属イオンのイオン対抽出選択性に及ぼす含ペンダントアーム型ジシッフ塩基配位子の構造効果

概要

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The structural effect of di-Schiff base ligands having pendant arms on ion-pair extraction selectivity of divalent transition metal cations was investigated by changing the ligand structure systematically. A di-Schiff base ligand, N,N'-bis(2-pyridylmethylidene)-1,2-diiminoethane (BPIE), and its analogues were used as complexation reagents. These ligands acted mainly as imine-N bidentate ones in the extraction systems, except for several cases. The effects of substituents around imine-N donor atoms, the imine-N distance, the steric restriction and the pendant arms were evaluated by comparing to extraction behavior of the BPIE analogues. (i) The introduction of substituents onto imine-C atoms led to a change in the extraction selectivity, whereas that onto ethylene-C atoms only caused an enhancement of the extractability without any change of the selectivity. (ii) A closer imine-N distance led to a higher mutual selectivity between each metal cation, whereas a longer distance decreased the selectivity. (iii) The effects of a steric restriction by geometrical and resonance structure resulted in the differences of the shield effect in extracted species and the steric distortion on the complexation, and these contributed the extraction selectivity. (iv) The pendant arms affected only the extractabiliby in the system. Furthermore, a selective extraction of capper (II) from other metal cations was achieved.
社団法人日本分析化学会の論文
2004-10-05