Enhanced Li+ ion-selective ionophoric properties of double armed diaza-12-crown-4 derivatives

A variety of double armed crown ethers were prepared in which amine, amide, ester, nitrile and pyridine moieties were attached as cation-ligating sidearms to diaza-12-crown-4 ring. FAB-MS and 7Li/13C/23Na NMR binding and liquid membrane transport studies revealed that most of them exhibited Li+ cation selectivity, though corresponding single armed lariat ethers showed Na+ cation selectivity. Among them, amine-armed diaza-12-crown-4 derivative offered the highest Li+ ion-selective ionophoric property. Its transport efficiency and selectivity were particularly superior to those of commercially available Li+ ion-selective ionophores.