Metal(II) binding by natural ionic glycosides: A solution study on 2,2 '-bipyridine containing ternary systems of Cu(II) and Ni(II) with lactobionic acid

The stability constants of the complexes formed between CU2+ or Ni2+ and lactobionic acid in binary and ternary 2,2'-bipyridine containing systems, were determined by potentiometric pH titrations in aqueous solution (25 degrees C, I = 0.1M, NaNO3). The pH dependence of the electronic spectra of these systems is also reported. Lactobionic acid reacts as chelating agent towards metal ions via carboxylic and alpha-hydroxylic oxygens; the total amount of free ions at physiological pH is less than 10%, in both binary and ternary systems. The general tendency to form complexes less stable than those of Cu(II) persists in the case of Ni(II) complexes solid compounds were also isolated and characterized by FT-IR and UV-VIS spectroscopies. (C) 1998 Elsevier Science Inc. All rights reserved.