Specific cooperative effect of a macrocyclic receptor for metal ion transfer into an ionic liquid

Okamura, Hiroyuki ; Ikeda, Atsushi* ; Saito, Takumi*; Aoyagi, Noboru ; Naganawa, Hirochika ; Hirayama, Naoki*; Umetani, Shigeo*; Imura, Hisanori*; Shimojo, Kojiro

An intramolecular cooperative extraction system for the removal of strontium cations (Sr $^{2+}$ ) from water by use of a novel macrocyclic receptor (H $_{2}$ DA18C6) composed of diaza-18-crown-6 and two -diketone fragments in ionic liquid (IL) is reported, together with X-ray spectroscopic characterization of the resulting extracted complexes in the IL and chloroform phases. The covalent attachment of two -diketone fragments to a diazacrown ether resulted in a cooperative interaction within the receptor for Sr $^{2+}$ transfer, which remarkably enhanced the efficiency of Sr $^{2+}$ transfer relative to a mixed -diketone and diazacrown system. The intramolecular cooperative effect was observed only in the IL extraction system, providing a 500-fold increase in extraction performance for Sr $^{2+}$ over chloroform. Slope analysis and potentiometric titration confirmed that identical extraction mechanisms operated in both the IL and chloroform systems. Extended X-ray absorption fine structure spectroscopy revealed that the average distance between Sr $^{2+}$ and O atoms in the Sr $^{2+}$ complex was shorter in IL than in chloroform. Consequently, Sr $^{2+}$ was held by H $_{2}$ DA18C6 more rigidly in IL than in chloroform, representing an important factor dominating the magnitude of the intramolecular cooperative effect of H $_{2}$ DA18C6 for Sr $^{2+}$ .

Language	:	English
Journal	:	Analytical Chemistry
Volume	:	84
Number	:	21
Pages	:	p.9332 - 9339
Publication Year/Month	:	2012/11
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Paper URL	:	https://doi.org/10.1021/ac302015h
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Article of JAEA R&D Review	:	Extraction of Strontium Using a Macrocyclic Compound; Extraction Enhanced by Applying Ionic Liquid Solvents[/]
Cooperating Institute	:	金沢大学

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Registration No. : AA20120704
JAEA Abstracts No. : 41000015
Paper Submission No. : 11567

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