Complexation of metal ions with dioxime of dialdehyde starch

Dialdehyde starch (30%) from periodate-oxidized potato starch was converted into its dioxime (DASOX). The dioxime was coordinated to the Ca, Cd, Co (II), Cu (II), Fe (II), Mg, Mn (II), Ni (II), Pb (II), and Zn ions. Particular metal ions were chelated to a different extent. In the complexes, one mole of a metal ion was coordinated on from 9 to 80 moles of the DASOX units. Similarly as pure DASOX, the metal complexes decomposed thermally in four steps. The coordination to all metal ions except Fe (II) increased temperature of the thermal decomposition and, except Cu (II), they also increased the rate of the first decomposition stage. After coordination the ligand decomposed more profoundly than in the free stage. Computational simulations pointed to the nitrogen atoms of the dioxime CN moiety and the oxygen atom of the former pyranose ring as the coordination sites.