Binding ability of aldaric acid toward metal(II). X-ray study and solution state investigation on Cu(II)-galactaric acid system and its 2,2 '-bypiridine adduct

The interaction of Cu2+ with galactaric acid leads to the formation, at acidic pH, of the complex species [CuGala] (Gala = galactaric dianion), while at physiological pH the prevailing species is [Cu(GalaH(-2))](2-) where the carbohydrate acts as chelating agent toward the metal ion through the carboxylic groups and the deprotonated ct-hydroxylic oxygens. The crystal structures of galactaric acid (1) and of the ternary complex [CuGala(bpy)](n). 2nH(2)O (2) (bpy = 2,2'-bipyridine) are also reported. A comparison of the coordinative behavior of galactaric acid and other aldonic and alduronic acids is also discussed. (C) 1999 Elsevier Science S.A. All rights reserved.