Experimental and Theoretical Study on the Complexation of the Thallium Cation with Dibenzo-18-crown-6.

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Tl+(aq) + 1.Na+(nb) <-> 1.Tl+(nb) + Na+(aq) taking place in the two-phase water-nitrobenzene system (1 = dibenzo-18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex(Tl+, 1.Na+) = 2.1. Further, the stability constant of the complex 1.Tl+ in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1.Tl+) = 6.6. Finally, by using quantum mechanical DFT calculations, the most probable structure of the resulting complex 1.Tl+ was solved.