Synthesis, characterization, antimicrobial, and DNA cleavage studies of metal complexes of coumarin Schiff bases

Co(II), Ni(II), Cu(II), and Zn(II) complexes of the Schiff bases formed by the condensation of 8-formyl-7-hydroxy-4-methyl-coumarin with 3-amino-pyridine (L (1) ) and 3-amino-2-chloro-pyridine (L (2) ) are synthesized and characterized by various physico-chemical methods. The FAB-mass spectra of the ligand L (1) and its Zn(II) complex are reported herewith. Thermal studies with Co(II) and Ni(II) complexes of both the ligands L (1) and L (2) are also reported. From the above studies, it is concluded that the ligand L (1) acts as a bidentate ligand coordinating through azomethine nitrogen and phenolic oxygen of coumarin moiety via deprotonation, and ligand L (2) acts as a tridentate ligand coordinating through azomethine nitrogen, phenolic oxygen of coumarin, and chlorine of pyridine moiety. All the complexes showed an octahedral geometry with a slight distortion in Cu(II) complexes. The fluorescence studies are carried out for ligand L (1) with its Co(II), Ni(II), Cu(II), and Zn(II) complexes. The ligands and the complexes were screened for antibacterial and antifungal activities in vitro. The antitubercular activities are carried out by middle Brook method for all the compounds. The MIC values, cytotoxicity properties, and DNA cleavage studies are carried out for most active ligand L (2) , Co(II), and Cu(II) complexes.