Complexation of the cesium cation with lithium ionophore VIII: extraction and DFT study

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Cs+(aq) + 1·Na+ (nb) = 1·Cs+(nb) + Na+(aq) taking place in the two-phase water-nitrobenzene system (1 = lithium ionophore VIII; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (Cs+, 1·Na+) = −0.5 ± 0.1. Further, the stability constant of the 1·Cs+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Cs+) = 4.8 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structure of the cationic complex species 1·Cs+ was derived. In the resulting complex, the “central” cation Cs+ is bound by six bond interactions to the corresponding six oxygen atoms of the parent ligand 1.