Pyrazole-based azo-metal(II) complexes as potential bioactive agents: synthesis, characterization, antimicrobial, anti-tuberculosis, and DNA interaction studies

Abstract

In the present investigation, the bioactive azo-dye ligand 1,5-dimethyl-4-[(3-methyl-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-4-yl)diazenyl]-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (L) and its transition metal complexes have been synthesized and characterized by various physical and spectroscopic techniques to elucidate their geometrical structures. The molar conductivity measurements confirmed the non-electrolytic nature of the complexes. EPR spectroscopy indicated that the metal complexes are monomeric in nature and exhibited octahedral geometry. The redox behavior of the copper complex was studied by the cyclic voltammetric technique in DMF solution and the complex showed well-established redox behavior at a scan rate of 0.05 V s⁻¹. The antimicrobial activity of the ligand and its metal complexes were screened against Escherichia coli, Bacillus subtilis, Aspergillus niger, and Candida albicans, and the results indicated increased activity after coordination of the ligand to the metal ions. The metal complexes exhibited enhanced antitubercular activity after chelation against M. tuberculosis. The DNA-binding experiments showed that the ligand and its metal complexes showed effective binding properties through intercalative mode against CT-DNA. All the synthesized molecules showed partial cleavage of supercoiled plasmid pUC18 DNA.

Graphical Abstract

Keywords:

• Pyrazole
• azo dyes
• metal(II) complexes
• anti-tuberculosis
• DNA interactions

Acknowledgements

Authors are thankful to the Department of Chemistry, Kuvempu University, Shivamogga for providing laboratory facility. Authors are also grateful to SAIF and CIL Panjab University for providing spectral data and Maratha Mandal’s Central research lab, Belagavi for anti-tuberculosis results.