Macromolecular ionophore II. Metal cation-binding property of (1→6)-2,5-anhydro-D-glucitol

Abstract

The cation-binding property has been studied for polymer 1 consisting of 3,4-di-O-methyl-D-glucitol units, (1→6)-2,5-anhydro-3,4-di-O-methyl-D-glucitol, and polymer 2 with a mole fraction of cyclized units of 0.52 synthesized by the polymerization of 1,2:5,6-dianhydro-3,4-O-isopropylidene-D-mannitol. Polymer 1 exhibited cation-binding selectivity in the order of K+>Rb+>Cs+>Na+> Li+, which was estimated using both liquid-liquid extraction and liquid-membrane transport methods. On the other hand, 2 showed an extremely low cation-binding characteristic in both extraction yield and selectivity, and the yield of K+ for 2 was ca. one-eighth of that for 1. There was a need for ca. 21-25 and ca. 200-400 repeating units in the complexes of 1 and 2 with K+, respectively. The binding ability of 1 strongly depended on the radius of the metal cations, and the extraction yields were relatively low for a cation with a radius of 1.12 angstroms and below (Mg2+, Li+, Ni2+, Co2+, Cu2+, Zn2+, Cd2+, Na+, Ca2+, and Sr2+) and high for a cation with a radius of 1.20 angstroms and above (Pb2+, Ag+, K+, Ba2+, Rb+, and Cs+).