Calix[4]arene-bis(coumarin-crown-6) as an extraordinarily effective macrocyclic receptor for Cs + , Ag + , and Tl +

On the basis of extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium \( \begin{aligned} {\text{M}}^{\,+\,} \left( {\text{aq}} \right){\,+\,{\bf{1}}} \cdot {\text{Cs}}^{ + } \left( {\text{nb}} \right)\; \rightleftarrows \; {\bf{1}}\cdot {\text{M}}^{ + } \left( {\text{nb}} \right){\text{ + Cs}}^{\,+\,} \left( {\text{aq}} \right) \hfill \\ \hfill \\ \end{aligned} \) occurring in the two–phase water–nitrobenzene system (M+=NH4 +, K+, Rb+, Ag+, Tl+; 1 = calix[4]arene-bis(coumarin-crown-6); aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the proved 1·M+ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the sequence of \( \text{NH}_{\text{4}}^{ + } < {\text{ K}}^{ + } < {\text{ Rb}}^{ + } < {\text{ Cs}}^{ + } < {\text{ Ag}}^{ + } < {\text{ Tl}}^{ + } . \)