Synthesis of crescent aromatic oligoamides with preorganized chelating groups and their extraction towards transition metal ions

Abstract

Three crescent aromatic oligoamides 1-3 with their backbones rigidified by intramolecular hydrogen bonds were designed and synthesized. The liquid-liquid extraction by these compounds has been investigated using UV-vis spectrometry towards Pb(2+) picrate and some transition metal picrates including Ag(+), Hg(2+), Cd(2+), Zn(2+), Cu(2+), Co(2+), Ni(2+) salts. The results revealed higher selectivity and efficiency towards Hg(2+) over other metal cations; pentameric ligand 1 with six oxygen donor atoms provided the highest extractability of 83.3%, while dimeric ligand 3 extracted almost exclusively Hg(2+). The stoichiometry of the extracted complex between ligand 1 and Hg(2+), and the extraction constant (logK(ex)) were determined in solvent extraction.