Synthesis, characterization, electrochemical and in-vitro antimicrobial studies of Co(II), Ni(II), and Cu(II) complexes with Schiff bases of formyl coumarin derivatives

Abstract

A series of Co(II), Ni(II), and Cu(II) complexes have been synthesized with Schiff bases (H₂L^I and H₂L^II) derived from 8-formyl-7-hydroxy-4-methylcoumarin or 5-formyl-6-hydroxycoumarin and o-aminophenol. Structures have been proposed from elemental analyses, spectral (IR, UV-Vis, FAB-mass, and Fluorescence), magnetic, and thermal studies. The measured low molar conductance values in DMF indicate that the complexes are non-electrolytes. Elemental analyses indicate ML · 3H₂O [M = Co(II), Ni(II), and Cu(II)] stoichiometry. Spectroscopic studies suggest coordination through azomethine nitrogen, phenolic oxygen of o-aminophenol, and the coumarin via deprotonation. The Schiff bases and their complexes have been screened for antibacterial (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella typhi) and antifungal (Aspergillus niger, Aspergillus flavus, and Cladosporium) activities by minimum inhibitory concentration (MIC) method. The redox behavior of the complexes was investigated using cyclic voltammetry (CV).

Keywords:

• Antibacterial
• Antifungal
• Coumarin
• Electrochemical
• Spectral

Acknowledgements

The authors are grateful to the Chairman, Department of Chemistry, Karnatak University, Dharwad, for the laboratory facilities. Authors are thankful to University Scientific Instrumentation Centre, Karnatak University, Dharwad, for getting the spectral data.