Thermodynamic Study for Dibenzo-24-crown-8 Complexes with Alkali Metal Ions in Nonaqueous Solvents

Abstract

Abstract Complex-formation constants (KML+) of dibenzo-24-crown-8 (DB24C8) with alkali metal ions in acetonitrile and the solubility of DB24C8 in methanol, acetonitrile, and propylene carbonate were determined conductometrically and spectrophotometrically at 25 °C, respectively. The KML+ value sequences of the alkali metal ions with DB24C8 are Na+>Cs+>K+=Rb+. Dibenzo-24-crown-8 shows no remarkable selectivity for the alkali metal ions in acetonitrile. Transfer activity coefficients of the DB24C8 complexes with alkali metal ions were calculated from these data and literature values of transfer activity coefficients of alkali metal ions. For the same alkali metal ion, the bulky DB24C8-alkali metal ion complex is more soluble in the aprotic solvents acetonitrile and propylene carbonate than in the protic solvent methanol as compared with the case of the alkali metal ion itself. The transfer activity coefficient of the DB24C8-alkali metal ion complex from methanol to acetonitrile is somewhat sensitive to the variation of the alkali metal ion in the DB24C8 cavity, whereas the mobility of the DB24C8-alkali metal ion complex at the same concentration in the solvents is not sensitive.