Analysis of Equilibria in the Extraction of Cesium Nitrate by Calix[4]arene-bis(t-Octylbenzo- Crown-6) in 1,2-Dichloroethane

The extraction of CsNO3 by the highly lipophilic calixarene-crown ether calix[4]arene-bis(t-octylbenzo-crown-6) (CABOBC6) in 1,2-dichloroethane (1,2-DCE) at 25 °C has been shown to be consistent with the formation of both 1 : 1 and 2 : 1 metal : ligand species. Variation of the aqueous-phase CsNO concentration up to 1.0 M and variation of the organic-phase calixarene concentration up to 0.10∼M was modeled by the program SXLSQI. Formation of the organic-phase species CsBNO3 (B = calixarene) was confirmed as well as the organic-phase dissociation products CsB+ and NO3-. Good evidence for the 2 : 1 metal : ligand organic-phase species Cs2B(NO3)2 was also found, although the dissociation of nitrate from this complex was not observed. Binding of the second Cs+ cation by the ligand is approximately two orders of magnitude weaker than binding of the first Cs+ cation. The logarithm of the apparent partition ratio (log PB) of the calixarene between water and 1,2-DCE was found by 1H-NMR techniques to be > 5.1.