Stabilities and transfer activity coefficients from water to polar nonaqueous solvents of 1,2-bis[2-(2-methoxyethoxy)ethoxy]benzene- and benzo-18-crown-6-cation complexes

ACE applied to the quantitative characterization of benzo‐18‐crown‐6‐ether binding with alkali metal ions in a methanol–water solvent system

“…It is essential that the constituents of the BGE do not interact with the ligand. According to the data presented in the literature, the Li + ion does not interact with B18C6 in methanol and forms only a very weak complex with this ligand in water 27, 28, 30. In our preliminary experiments in the mixed binary methanol–water (50/50 v/v) solvent system, interactions of the Li + or H 2 BO ions with B18C6 were not observed.…”

“…The binding constants of the complexes above in the mixed methanol–water solvent system determined in this study were found to be about two orders lower than in methanol and about one order higher than in water, see Table 1. The low stabilities of the B18C6–alkali metal ion complexes in water have been attributed to the strong hydrogen bonding between the ether oxygen atoms of the uncomplexed B18C6 and water molecules 27. The same effect is probably responsible for the substantially reduced values of K b in the mixed methanol–water solvent system as compared to those in pure methanol.…”

“…The binding constants of B18C6 with several metal cations in different solvents ( e.g . water, methanol, ACN, propylene carbonate, DMSO, DMF) have been determined by various analytical methods, such as conductometry 27, spectrophotometry 28, LC 29, 30 and CE 31. However, most of the data were obtained in pure solvents and only a few articles have reported the binding constants of the B18C6 complexes with alkali metal ions (Na + , K + , Cs + ) in the mixed aqueous–methanolic (8/92, v/v) solvent 26.…”

Up to 4 Orders of Magnitude Enhancement of Crown Ether Complexation in an Aqueous Phase Coexistent with Ice

“…Thus, the complexation should primarily occur in the WPI phase. The complexation constants of crown ethers in water (log K c bulk ) have been reported as 0.45 for B15C5–Na + , 0.38 for B15C5–K + , 0.81–1.38 for B18C6–Na + , , 1.66–1.74 for B18C6–K + , , −0.3 to 1.1 for DB24C8–Na + , and 0.63–0.91 for DB24C8–K + . As is well-known, the complexation of crown ethers is suppressed in water relative to that in polar organic solvents because of the strong hydration to cations .…”

“… a Determined from the dependence of k on c salt in the ice stationary phase. b Range of c salt used for the determination of K c . c Determined by solvent extraction at −10 °C. d Literature values − determined at 25 °C are shown in parentheses. …”