Synthesis, Spectral Characterization and Pharmacological Evaluation of Ni(II) Complexes of 6-Nitro-benzothiazole Incorporated Azo Dyes

The present work describes the synthesis of bioactive Ni(II) complexes derived from 6-nitro-1,3-benzothiazole incorporated azo dyes. The newly synthesized azo dyes and their Ni(II) complexes are characterized by various physical and spectroscopic techniques. The IR spectral data of metal complexes revealed that the bonding sites are the nitrogen atom of the azo group and oxygen atom phenolic group of the pyridone moiety of the ligands. All the azo dyes behave as bidentate ligands with metal–ligand ratio 1:2 of the type [Ni(L)2(H2O)2], where L stands for deprotonated azo dye ligand. The TG–DTA studies showed good thermal stability and confirmed the presence of coordinated water molecules in all the metal complexes. To investigate the growth inhibitory efficiency of the metal complexes after chelation with the ligands, the synthesized compounds were examined for their antimicrobial activity by the tube dilution assay. All the synthesized compounds have shown significant activity against tested pathogenic strains. The azo dyes and their Ni(II) complexes were studied for their antimycobacterial and anti-inflammatory activity and all the complexes exhibited increased activity after chelation. The DNA cleavage efficiency of the synthesized compounds was tested against pBR322, and only the azo dye L3 and its Ni(II) complex able to cleave all forms of DNA while the rest of the compounds showed partial cleavage against pBR322.