Hg(II)-coordination by sugar-acids: Role of the hydroxy groups

A solution study on the ability of some derivatised sugars [glucuronic acid (GluA), galacturonic acid (GalA) and glucosaminic acid (GlNA)] to complex the Hg(II) ion is reported. The stability constants of the complex species were determined by potentiometric measurements while H-1 NMR experiments allow to define the coordination sites of sugar molecules. GluA coordinates the metal ion through the carboxylic oxygen and the O-4 hydroxyl group and is found to form more stable complexes with respect to GalA in which metal ligation is from the carboxylic oxygen and the O-5 ring oxygen. GlNA forms stable complexes chelating Hg(II) ion through carboxylic oxygen and the a-amino group. The ternary 2,2´-bipyridine containing systems were also investigated by means of potentiometric studies. The ML2 complexes were also isolated in the solid state and characterised by IR spectroscopy.