Extraction behavior of copper(II) ion by calixarene carboxylate derivatives preorganized by sodium ion

The extraction equilibrium of sodium ion with 25,27-bis(carboxymethoxy)-26,28-bis(carboxypropoxy)-5,11,17,23-tetrakis(1,1,3,3-tetramethylbutyl)calix[4]arene and 25,26,27, 28-tetrakis(carboxymethoxy)-5,11,17,23-tetrakis(1,1,3,3-tetramethylbutyl)calix[4]arene has been studied by means of H-1-NMR spectrometry. The extraction equilibria of copper (II) ion with the above extractants have also been investigated in the absence or presence of sodium ion to clarify the extraction mechanism and the effect of the coexisting sodium ion on copper ion. The extraction of copper ion was found to be accompanied with co-extraction of coexisting sodium ion. The extraction behavior of copper ions with the extractants was strongly influenced by coexisting sodium ions. The coextracted sodium ion shifts the pH region, at which the extraction of copper (II) ion takes place, to lower pH one for both extractants. Based on the result, it was deduced that the sodium ion, which was extracted prior to copper(II) ion, preorganized the extractants to accept the copper (II) ion. The preorganized calixarene has a high extractability for copper(II) ion compared to that of an ordinary calixarene.