Thiacalix[4]arene derivatives bearing imidazole units : a ditopic hard/soft receptor for Na⁺ and K⁺/Ag⁺ with an allosteric effect and a reusable extractant for dichromate anions

Abstract

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Two novel receptors 5,11,17,23-tetra-tert-butyl-25,27-bis[(ethoxycarbonyl)methoxy]-26,28-bis-[1-methyl-(imidazole)meth-oxy] -2,8,14,20-tetra-thiacalix[4]arene (L1) and 5,11,17,23-tetra-tert-butyl-25,27-bis-[(benzyl)methoxy] -26,28-bis-[1-methyl-(imidazole)-methoxy]-2,8,14,20-tetrathiacalix[4] arene (L2) possessing imidazole moieties based on thiacalix[4]arene in the 1,3-alternate conformation have been synthesized and characterized. The crystal structures of L1 and L2 have been determined. The binding behaviour towards Li + , Na + , K + and Ag + ions has been examined by 1 H NMR titration experiments in (CDCl 3 /CD 3 CN; 10:1, v/v) solution. The exclusive formation of mononuclear complexes of L1 with metal cations is of particular interest revealing a negative allosteric effect in the thiacalix[4]arene family. Liquid-liquid extraction experiments indicate that synthesized L2 can be utilized as an efficient reusable extractant for dichromate anion by controlling the pH of the aqueous solution