Studies on some 3d metal complexes - Synthesis, spectroscopic characterization and biological studies

A novel tridentate Schiff base ligand was prepared from 3-acetylcoumarin and 2-aminobenzoic acid. This ligand is versatile in forming complexes with manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) ions. The ligand and the metal complexes were characterized through various physicochemical and spectral studies. These studies include elemental analysis, molar conductance, magnetic susceptibility, UV-Vis, IR, H-1 NMR, C-13 NMR and ESR spectral studies wherever possible and applicable. The spectral data revealed that the ligand acted as monobasic tridentate, coordinating to the metal ion through the azomethine nitrogen, lactone carbonyl oxygen and carboxylate oxygen. The fluorescence spectra of the ligand and its metal complexes in DMSO were also recorded. The powder X-ray diffraction pattern showed the crystalline nature of the ligand and its copper(II) complex. The ligand possessed an orthorhombic crystal structure and on complexation the crystal system is changed to tetragonal. The ligand and the metal complexes were screened for their antibacterial and antifungal activities and it has been observed that the metal complexes are more potent bactericides and fungicides than the ligand. The alpha-amylase inhibitory activity of the ligand and metal complexes was also examined. In this case also chelation enhanced the alpha-amylase inhibitory activity.