Two novel bipyridine-based cobalt (II) complexes: synthesis, characterization, molecular docking, DNA-binding and biological evaluation

Abstract

Bipyridine derivatives have shown different applications in chemistry such as electron transfer, catalysis, biological systems and artificial photosynthesis. Two cobalt(II) complexes with formula [Co(5,5′-dmbipy)₂(NCS)₂]₁ and [Co(5,5′-dmbipy)₃] [Co(NCS)₄]₂ were prepared. The metal complexes 1 and 2 were characterized through FT-IR, electronic absorption, elemental analysis and ¹H-NMR. The interaction of complexes 1 and 2 with FS-DNA was investigated by fluorescence, UV–Vis and gel electrophoresis. The antibacterial properties have been studied in vitro against two gram-negative and two gram-positive standard bacterial strains. The synthesized complexes were further investigated against MCF-7 cells at 25, 50, 100 and 200 µM. The results revealed that the metal complexes can bind effectively to FS-DNA. The measured thermodynamic factors (ΔH°, ΔS° and ΔG°) displayed that hydrogen bonding, van der Waals forces (for DNA-compound 1) and electrostatic binding (for DNA-compound 2) are the most important interactions. The binding forces in metal complexes 1 and 2 are spontaneous as suggested by the negative ΔG°. Specific viscosity of FS-DNA remained without significant changes while the concentration of complexes 1 and 2 increased. The results of molecular docking with FS-DNA illustrate the binding sites and binding modes that are in acceptable agreement with experimental results. The biological results determined that complexes 1 and 2 exhibit antibacterial activities that are better than those shown for their corresponding metal salt and free ligand. The target compounds showed low-to-moderate cytotoxicity activities. The obtained results revealed that the synthesized complexes are stronger antibacterial agents against the gram-positive than gram-negative bacteria. In the present study, for the first time we reported two Co(II) complexes bearing 5,5′-dimethyl-2,2′-bipyridine ligands.

Communicated by Ramaswamy H. Sarma

Keywords:

• Co(II) complex
• 5,5′-dimethyl-2,2′-bipyridine
• DNA-binding
• cytotoxicity
• antibacterial activity

Acknowledgment

This study was part of the PhD thesis of Tahere Kondori.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors sincerely thank the University of Sistan and Baluchestan for providing financial support of this work.