A Conductance Study of 1:1 Complexes of Glyme-5, 18 Crown 6 and Tetraethylene Glycol bis Quinoline Ether with Alkali Metal Ions in Methanol/Water

Abstract

Conductivities of alkali metal picrates in the presence of glyme-5, 18 crown 6 and tetraethylene glycol bis quinoline ether (TEGBQE) were measured at 25ºC in methanol water mixture. Formation constants and molar conductivities of the 1 : 1 complexes of these ligands with alkali metal ions in 70% methanol were determined. The log K_ML+ sequences of the alkali metal ions with pentaglyme, 18 C6 and bis quinoline ether are K⁺ > Na⁺ > Rb⁺ ≈ Cs⁺ > Li⁺, K⁺ » Na⁺ > Rb⁺ > Cs⁺, Na⁺ > K⁺ > Rb > CS⁺ > Li⁺ respectively. This sequence for G 5 is consistent entirely with 18 C 6, but the order is different with TEGBQE. The complexes are less stable in case of non-cyclic ligands and selectivity is lost in going from cyclic to non-cyclic ligand. The TEGBQE complex may be entropy destablised due to the two flexible arms.