Synthesis and study of allosteric effects on extraction behavior of novel calixarene-based dichromate anion receptors

In this study the selective derivatization of p-tert-butylcalix[4]arene was carried out and two new calix[4]arene-based azacrown ionophores, 5,17-di-tert-butyl-11, 23-di-(methyl-3,5-dioxaoctane-1,8-diimine)-25,26,27,28-tetrahydroxycalix[4]arene (), and 5,17-di-tert-butyl-11,23-di-(methyl-3,5-dioxaoctane-1,8-diimine)-25,27-diethoxyformyl-methoxy-26,28-dihydroxycalix[4]arene () have been synthesized. Treatment of 5,17-di-tert-butyl-11,23-diformylcalix[4]arene-25,26,27,28-tetrol () with 1,8-diamino-3,6-dioxaoctane gave the ionophore which was converted to its diester derivative by reaction with ethylbromoacetate in the presence of potassium carbonate. In the synthesis, the upper and lower rims of p-tert-butylcalix[4]arene were modified in order to acquire binding sites for the recognition of metal cations and dichromate anions. It was observed that receptor is a better extractant for Cr2O72− anions than receptor . The protonated alkylinium form of is an effective extractant for transferring the Cr2O72− anions from aqueous into a dichloromethane layer and failed in transferring Na+ cations due to the allosteric effect produced by the crown part of the calix moiety present at the p-position.