The influence of reaction parameters on complexation of Zn(II) complexes with biopolymeric Schiff bases prepared from chitosan and salicylaldehyde.

Influence of some reactional parameters as mol ratio (Schiff base:metal), solvent, temperature and reaction time were evaluated in order to improve the extension of complexation during the preparation of zinc complexes of biopolymeric Schiff base from chitosan and salicylaldehyde. Zinc(II) complex was used as a model system in order to improve the degree of complexation for further synthesis of different Schiff bases complexes from other aldehydes and metallic centers. The complexation yields for each synthesis were estimated on the basis of the zinc oxide formed after thermal degradation. Thus thermogravimetry was used to determine the experimental percentage of metal that interact with the free biopolymeric Schiff base. In conclusion, complexation reaction of zinc(II) with biopolymeric Schiff bases was more effective at 40 °C in ethanol as a solvent with intermediary dielectric constant, which resulted in higher metallic contents. Other experimental conditions that resulted in highest degree of complexation were mol ratio 1.0:1.0 (mol/mol, Schiff base:metal), reaction temperature 40 °C and reaction time of 8 h in ethanol. Biological activity of free ligand and its Zn(II) complex obtained under optimized conditions were evaluated against tumor cells.