Lipophilic 14-crown-4 derivatives incorporating nitrophenol substituent are excellent lithiumionophores for proton-driven cation transport, in which extremely high selectivity ratios of lithium over sodium are realized.
Lipophilic 14-crown-4 derivatives bearing a chromogen such as nitrophenol and azophenol residues prove to be excellent extraction-photometric reagents for lithium ion. The lithium selectivities are extremely high, the extraction equilibrium constants for lithium being increased about two orders of magnitude over those for sodium.