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

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.