Synthesis and coordinating ability of chitosan dithiocarbamate and analogs towards Cu(II) ions

Potassium chitosan dithiocarbamate (ChitDTC) was synthesized and characterized by elemental analysis and solid-state (13)C NMR spectroscopy. The degree of substitution (DS) (number of substituents per 100 2-amino-2-deoxyglucopyranoside units) and molalities of the groups were calculated for acetylamino, amino and dithiocarbamate substituents in chitin, chitosan and ChitDTC. A comparative study of the retention and exchange of Cu(II) was performed with chitin, chitosan and ChitDTC at 30degreesC, pH 6.0 (0.1 M succinate). The stability constants, K(X), for the heterogenous equilibrium ChitX + Cu(II) reversible arrow(KX) ChitXCu(II) were calculated assuming that complexing of Cu(II) ions was largely in a 1:1 ratio with respect to each group. The values of K(X) for each group were NHAc 45.1, DTC 3.14 x 10(3), and NH(2) 1.12 x 10(4). It is proposed that in the presence of succinate, the main species of aqua Cu(II) ion present in solution must be the uncharged Cu(II)-succinate complex that prevents the acetylamino, amino and DTC groups from forming complexes higher than 1: 1. Also, this may explain the fact that the stability constant for DTC was lower than for the amino group. The method allows the characterization of the chelating ability of each group in ChitDTC with respect to metal ions. Copyright (C) 2002 John Wiley Sons, Ltd.