Versatile applications of cobalt and copper complexes of biopolymeric Schiff base ligands derived from chitosan

In the present study, biopolymeric Schiff base (SB) ligands were synthesized from chitosan and isatin. Consequently, their earth abundant transition metal complexes of cobalt and copper were synthesized. All compounds were extensively characterized using FTIR and UV spectroscopy, thermo-gravimetric (TG) analysis, X-ray powder diffraction (XRD) and FESEM (field emission scanning electron microscopy). The impetus of this study was to explore different applications of the same transition metal complexes, thereby converting them to broad spectrum antimicrobial drugs and to useful chemical catalysts. Thus, these cobalt and copper complexes were applied as anti-bacterial and anti-fungal agents and in reductive degradation of common pollutants. Specifically, chitosan, and all synthesized compounds were investigated against fungal species, namely, Candida and Aspergillus, and bacterial species, like Pseudomonas syringae, Escherichia coli, Staphylococcus aureus and Staphylococcus epidermis. All compounds demonstrated promising antimicrobial activity. Chitosan-modified compounds demonstrated a high antifungal activity against Candida albicans and possessed superior antibacterial action than free chitosan. Additionally, catalytic ability in reductive degradation of common dyes, methylene blue (MEB), Congo red (CR) and methyl orange (MO), was investigated. These dyes were conveniently degraded in presence of metal complexes, whereas neither chitosan nor the Schiff base ligand derived from it could carry out similar reaction.