Extraction and DFT study on the complexation of the cesium cation with dibenzo-21-crown-7 |
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Authors: | E Makrlík P Toman P Vaňura |
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Institution: | 1.Faculty of Applied Sciences,University of West Bohemia,Pilsen,Czech Republic;2.Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic,Prague 6,Czech Republic;3.Department of Analytical Chemistry,Institute of Chemical Technology,Prague 6,Czech Republic |
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Abstract: | From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium
\textCs + ( \textaq ) + \textA - ( \textaq ) + 1( \textnb )\underset \rightleftharpoons 1·\textCs + ( \textnb ) + \textA - ( \textnb ) {\text{Cs}}^{ + } \left( {\text{aq}} \right) + {\text{A}}^{ - } \left( {\text{aq}} \right) + {\mathbf{1}}\left( {\text{nb}} \right)\underset {} \rightleftharpoons {\mathbf{1}}\cdot{\text{Cs}}^{ + } \left( {\text{nb}} \right) + {\text{A}}^{ - } \left( {\text{nb}} \right) taking place in the two-phase water-nitrobenzene system (A− = picrate, 1 = dibenzo-21-crown-7; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K
ex (1·Cs+, A−) = 4.4 ± 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+) = 6.3 ± 0.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the resulting cationic
complex species 1·Cs+ was solved. |
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