Synthesis of chromogenic crown ethers and liquid-liquid extraction of alkali metal ions

Separation and purification of lithium by solvent extraction and supported liquid membrane, analysis of their mechanism: a review

“…Katayama et al reported the synthesis of crown ethers carrying a pendant phenolic chromophore for recovery of lithium . The phenolic protons of these crown ethers after dissociation provide lipophilic anions which can extract alkali metal cations into 1,2‐dichloroethane by forming highly‐colored neutral metal complexes.…”

Crown ether derivatives of anthraquinone as ionophores in ion‐selective electrodes

“…Specifically, Dix and Vogtle synthesized anthraquinonophanes by reacting alizarin with poly(ethy1ene glycol) ditosylates [61, Further, Buhleier and Vogtle bridged the l,&position of the anthraquinone system with a 1, o-dithiolate to yield a dithia-anthraquinonophane [71. Takagi and coworkers prepared similar reagents by coupling alizarin to monoaza-crown ethers by the Mannich reaction [8]. The resulting chromogenic crown ethers are potentially useful as ion-specific dyes (chromoionophores), and were used for the selective extraction and photometric determination of alkali metal cations.…”

Metal cation-induced multifluorescence of azacrown-substituted (tetrafluorophenyl)imidazo[1,2-a]pyridine

“…Addition of Li þ cation to an acetonitrile solution of 1 did not cause the appreciable change in the absorption but enhanced the fluorescence around the 388 nm wavelength ( Figure 3). Although Li þ cation did not affect the 1 H NMR spectra of 1 distinctly, this fluorescence enhancement would be ascribed to the association of Li þ cation with the azacrown site from the fact that a similar fluorescence enhancement was not observed in the case of 3 and from the consideration of the size-matching of Li þ cation with the 12-azacrown ring (16). The curve fitting of the fluorescence intensity of 1 supported the formation of a 1:1 complex of 1 and Li þ cation, its binding constant being estimated to be K ¼ (4.7^0.7) £ 10 2 M 21 ( Figure 11).…”