Synthesis of chromogenic crown ethers and liquid-liquid extraction of alkaline earth metal ions

Yoshiki Katayama, Ryuji Fukuda, Toshiharu Iwasaki, Kazuhide Nita, Makoto Takagi

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

New crown ether dyes carrying two pendent anionic side-arms were synthesized for the extraction-spectrophotometry of alkaline earth metal ions. In the extraction of alkaline earth metal ions by these dianionic reagents, size recognition by the crown ether ring was more remarkable than in the case of alkali metal ion extraction by a similar type of monoanionic reagents. Dramatic changes in metal selectivity were observed when the nature of the anionic side-arm was changed while the crown ether skeleton was kept the same. The structure/selectivity relationship is discussed in terms of "chelate" and "intramolecular ion-pair" formation. Typically, when the basicity of the pendent anions was relatively high and a six-membered chelate was structurally possible for the pendent anions and the crown-bound metal, the extraction of calcium was favored by up to a factor of 3000 in the ratio of the Ca/Ba extraction constants for reagents of the diaza-18-crown-6 type. In contrast, the reagents which had pendent anions with only poor coordination ability for metal ions seemed to form complexes of the ion-pair type, and calcium ion was 105 times less extractable than barium ion for the same diaza-18-crown-6-skeleton. Strontium ion seemed to be extracted most effectively when the extracted complex assumed properties intermediate between the chelate and intramolecular ion-pair.

Original languageEnglish
Pages (from-to)113-125
Number of pages13
JournalAnalytica Chimica Acta
Volume204
Issue numberC
DOIs
Publication statusPublished - 1988

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Biochemistry
  • Environmental Chemistry
  • Spectroscopy

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