[Study on D-glucosamine-zn (II) complexes by IR spectral analysis].

In this paper, a series of glucosamine-Zn(II) complexes were synthesized by the reaction of D-glucosamine hydrochloride with ZnSO4 at different pH values. The physical properties and the IR spectra of glucosamine-ZnSO4 complexes were investigated. The absorption at 3346 and 3292 cm(-1) shifted to 3300 cm(-1) due to O--H and N--H stretching, one at 1617 cm(-1) shifted to 1530 cm(-1) due to N-H stretching, and one at 1094 cm(-1) disappeared due to secondary alcohol --OH stretching. But 1033 cm(-1) with primary alcohol --OH did not shift, suggesting that both the amino and secondary hydroxyl groups of glucosamine are coordinated to Zn(II). The results showed that the coordination ability of Zn(II) to glucosamine was enhanced with the pH value increasing, however, the coordination ability weakened when pH value was more than 6.5. So pH 6.5 is an optimal coordination condition for glucosamine-ZnSO4 complexes. The complexes of D-glucosamine with different zinc salts (zinc sulfate, zinc nitrate, zinc acetate, and zinc chloride) were also synthesized at the same pH value, and zinc chloride had weaker coordination ability than other zinc salts. Their IR spectra indicated that glucosamine-Zn(II) complexes with different zinc salts had different coordination model, and only glucosamine-ZnSO4 complex had fixed ratio of coordination under the condition of pH 6.5. The structure of the complex seems to correspond to [Zn(glucosamine)]SO4 7H2O at pH 6.5.