Stability Constants of Cesium Complexes with 18-Crown-6 in Ionic Liquids

摘要

The stability constants of the complex[Cs(18C6)]~+(18C6 is 18-crown-6(L))in N-butylpyridinium methyl sulfate(I)and of the complex[Cs(18C6)2]~+ in l-butyl-3-methylimidazolium bis(trifluoromethylsulfo-nyl)imide(II)were measured by using ~(133)Cs NMR spectroscopy at 23°C.It was found that logK(Cs + L)in solvent I is 1.20±0.13 and logK(CsL + L)in solvent II is 1.18 + 0.05.For the complex[Cs(l 8C6)2]~+,the dependence of its stability constant on the temperature in the 23-50°C range was obtained and the enthalpy change in the complexation was determined:DLETA H(CsL + L)=-47 kJ/mol.It was demonstrated that the enthalpy change is favorable for the formation of[Cs(18C6)2]~+,while the entropy change hinders the complexation.