DNA Binding, Molecular Docking and Antimicrobial Studies of Co(III) Polypyridyl Complexes

Three new cobalt(III) polypyridyl complexes [Co(phen)₂(TIPB)]³⁺(1) {TIPB = 5-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)thiophene-2-yl-2-boronic acid}, (phen = 1,10-Phenanthroline), [Co(bpy)₂(TIPB)]³⁺(2) (bpy = 2,2'bipyridyl), [Co(dmb)₂(TIPB)]³⁺(3) (dmb = 4, 4'-dimethyl 2, 2'-bipyridine) have been synthesized and characterized by spectral studies FTIR, UV-vis, ¹H, ¹³C-NMR, Mass Spectroscopy and Elemental analysis. The binding properties of all three complexes towards calf-thymus DNA (CT-DNA) have been investigated using UV-visible, emission spectroscopy and viscosity measurements, indicating that all the complexes bind to CT-DNA predominantly through intercalation, but with different affinities. The binding strength of these complexes were 1 > 2 > 3. These complexes cleaved the pBR322 DNA into different forms when irradiated under UV light. The binding studies of Co(III) polypyridyl complexes with ds-DNA were carried out by molecular modeling (MM) studies to identify the binding interactions. The molecular mechanics studies were performed on metal complexes to obtain stable 3D conformers. Double-stranded DNA was docked to metal complexes' energy-minimized three-dimensional structures. Through intercalation, the aromatic ligand TIPB makes it easier for the metal complex to bind to DNA. The necessary characteristics for metal complexes to be regarded as DNA intercalators are their substantial interactions with DNA. The available experimental data provides strong support for the molecular docking data. The binding selectivity and strength of the metal complex with DNA show that the preferred binding mode involves guanine rich site. It reveals that complexes will bind in between base pairs of DNA and gives information about the binding residues and strength. The antimicrobial studies of these complexes give considerable activity with different bacteria like Staphylococcus aureus, and Bacillus subtilis.