Abstract

Some new podands containing phenyl(B), benzyl(Bz), pyridine(Py), quinoline(Q) and naphthalene(Np) as end-groups, and oxygen(O) and sulfur(S) in ether chains as donor atoms have been synthesized. The univalent cation binding characteristics of these podands have been studied by NMR titration and solvent extraction. By NMR titration we have found that the most of podands form 1:1 complexes with <TEX>$Ag^+$</TEX> ion. Especially, the substituted sulfur atoms in ether chains show the effects to enhance the stabilities. We also carried out the extractions of univalent cation picrates including alkaline metal, <TEX>$Ag^+$</TEX>, <TEX>$Tl^+$</TEX> and <TEX>$NH_4{^-}$</TEX> ions from aqueous to chloroform layer by using these podands. We found that the extractabilities of <TEX>$Ag^+$</TEX> ion with the quinoline-containing podands such as, <TEX>$Q_2O_4$</TEX>, <TEX>$Q_2O_5$</TEX> and <TEX>$BQO_5$</TEX> were 86.8, 86.6 and 48.0% respectively, but the naphthalene-containing podands such as, <TEX>$Np_2O_4$</TEX> and <TEX>$Np_2O_5$</TEX> extracted quite small amount. Otherwise, in cases of <TEX>$Bz_2O_3S_2$</TEX>(89.4%), <TEX>$B_2O_2S_2$</TEX>(96.8%), <TEX>$B_2O_3S_2$</TEX>(58.9%), <TEX>$Py_2O_2S_2$</TEX>(58.8%), <TEX>$Py_2O_3S_2$</TEX>(42.1%), and <TEX>$B_2O_4S$</TEX>(15.0%), interestingly, <TEX>$Bz_2O_3S_2$</TEX> which have sulfur atoms and benzyl groups showed the highest extraction selectivity for <TEX>$Ag^+$</TEX> ion. This result seems due to not only the strong interaction of <TEX>$Ag^+$</TEX> ion with sulfur donors according to the HSAB theory, but also the effective <TEX>${\pi}-{\pi}$</TEX> stacking interaction between two aromatic end-groups which is enhanced by the flexible methylene spacing group in benzyl groups instead of phenyl groups. The extraction coefficients gave the similar tendency as the extractabilities and the stabilities. From these results, it could be concluded that the predominant factor affected to extraction coefficients is the stabilities, which are strongly influenced by the structures of podands.