H. Sakamoto et al., BENZOCROWN ETHER HYDRAZONES AS EXTRACTANTS FOR ALKALI-METAL IONS, Bulletin of the Chemical Society of Japan, 66(10), 1993, pp. 2907-2914
Four types of benzo-15-crown-5 and benzo-18-crown-6 derivatives bearin
g a substituted hydrazone moiety as a proton-dissociable chromogenic g
roup were synthesized and the solvent extraction behaviors of these co
mpounds for alkali metal ions were evaluated spectrophotometrically. B
enzo-15-crown-5 and -18-crown-6 hydrazones with 2,4-dinitro-6-(trifluo
romethyl)phenyl or 2,6-dinitro-4-(trifluoromethyl)phenyl groups extrac
ted alkali metal ions predominantly as 2:1 and 1:1 (crown ether: metal
ion) complexes, respectively, from an aqueous alkaline solution into
1,2-dichloroethane and these ligands exhibited high K+-selectivity. Th
e composition of the extracted species and the K+-selectivity depended
on the polarity of the extraction solvent used. In particular, 2:2 co
mplexes of several alkali metal ions with benzo-15-crown-5 and -18-cro
wn-6 hydrazones bearing a 2,4-dinitro-6-(trifluoromethyl)phenyl group
were readily extracted from an aqueous solution into chloroform.