Lithium ion-selective alkylphosphoric acid armed dibenzo- and benzo-14-crown-4 derivatives

Abstract

New dibenzo-2 and benzo-14-crown-4 derivatives 4a-c having an ionizable alkyl phosphoric acid moiety as an additional pendant arm binding site have been synthesized. Their complexing abilities have been measured by solvent extraction and transport experiments. It is shown that introduction of the pendant group into the dibenzo- and benzo-14-crown-4 derivatives significantly enhances their ability to extract and transport Li⁺ ion. IR spectroscopy, fast atom bombardment (FAB) mass spectrometry and ¹³C NMR spectroscopy were used to study the structure of the complex of 2 with Li⁺ ion. From these results, it was suggested that Li⁺ ion is strongly bound by both the crown oxygen and the phosphate anion of the side arm and is predominantly coordinated by the phosphate anion and the nearest oxygen atoms to the pendant site of the crown ring.