Synthesis, characterization and biological studies on Co(II), Ni(II), Cu(II) and Zn(II) complexes derived from 4-(2-amino ethyl) benzene-1,2-diol and 1,4 benzoquinone

A novel Schiff base ligand (L) has been synthesized using 4-(2-amino ethyl) benzene-1,2-diol (Dopamine) and 1,4 benzoquinone. Co(II), Ni(II), Cu(II) and Zn(II) complexes with this hexadentate ligand have been synthesized with metal:ligand (1:1) stoichiometry. The Schiff base ligand and its metal complexes have been characterized by elemental analysis, molar conductance, magnetic susceptibility, infrared and electronic spectra, ESR, NMR, Mass spectra, powder X-ray diffraction and SEM studies. Molar conductance showed that all complexes are non-electrolytic in nature. The Co(II), Ni(II), Zn(II) complexes are found to be octahedral and distorted octahedral structure for Cu(II) complex. Powder X-ray diffraction reveals that Schiff base ligand and its metal complexes are nano-crystalline in nature but Co(II) complex is amorphous. Different morphologies of synthesized compounds are identified by SEM images. Schiff base ligand and its metal complexes were screened against gram-positive bacteria, gram-negative bacteria and one fungus strain. The data show that the ligand and its metal complexes have significant activity. Copper(II) complex shows better activity than other complexes. The Schiff base ligand and its copper(II) complex are evaluated for the antiinflammatory by HRBC membrane stabilization method. The anti-cancer activity of Schiff base ligand and its copper complex was also studied against human breast cancer cell line by MTT assay method. The anti-diabetic activity of Schiff base ligand and its copper(II) complex is also studied by alpha-amylase method.