A novel azo dye ligand, 7-hydroxy-4-methyl-8-[(E)-(6-nitro-1,3-benzothiazol-2-yl)diazenyl]-2H-chromen-2-one ligand (MNB)was synthesized, and has been used to synthesise Co(II), Ni(II), Cu(II) complexes. The synthesized compounds were characterized using various physicochemical and spectroscopic techniques.The biological investigation of the synthesized Schiff base ligand and its metal complexes have been determined against the bacteria (Staphylococcus aureus and Escherichia coli), fungal (A. flavous and P. anomala) and antioxidant activity using Iron chelating assay by using standard assay method.Analysis of the absorbance data revealed degradation percentages of 83%, 64% and 61% for Co(II), Ni(II) and Cu(II) complexes, respectively. These results indicate that Co(II) complex exhibit superior photodegradation efficiency compared to the Ni(II) and Cu(II) complexes for methylene blue dye.