COORDINATION OF CD(II) BY N-ALKYLAMINO SUGARS IN AQUEOUS-SOLUTION AS STUDIED BY POTENTIOMETRY AND NMR-SPECTROSCOPY

The Cd(II) coordination of 1-(2-aminoethylamino)-1-deoxy-D-alditols (1 a-b) and of 1-(2-aminopropylamino)-1-deoxy-D-alditols (2a-b) was inves tigated by means of Cd-113 NMR spectroscopy and potentiometry. The inf luence of the sugar chains on the basicity of the amino groups was det ermined with C-13 chemical shift pH titration curves. It appears that the inductive effects of the sugar moieties give rise to a decrease in pK(a) of the secondary amino function. The Cd(II) stability constants for Ligands 1a-b and 2a-b and the Ni(II) stability constants for 1a w ere determined by potentiometry. Cd-113 NMR spectroscopy was employed to study the structures of the Cd(II) complexes of 1a-b and 2b. From t he Cd-113 chemical shifts for CdL and CdL(2), it could be concluded th at at neutral pH both primary and secondary nitrogen atoms are involve d in coordination. C-13 NMR shows that additional coordination of a hy droxyl group of the carbohydrate chain occurs at high pH (pH 12). (C) 1996 Elsevier Science Ltd.