Metformin-Derived Water-Soluble Cobalt Complexes: Thermal, Spectroscopic, DNA Interaction, and Molecular Docking Studies.

Novel three water-soluble cobalt (II) complexes of type [Co(metf)(o-phen)2]Cl2 (1), [Co(metf)(opda)2]Cl2 (2), and [Co(metf)(2-2'bipy)2]Cl2 (3) (Metf, metformin; o-phen, ortho-phenanthroline; opda, ortho-phenylenediamine; 2,2'-bipy, 2,2'-bipyridine) were synthesized and characterized by various analytical and spectral techniques. Based on these studies, octahedral geometry is assigned to these complexes. The stability of the complexes has been calculated from quantum chemical parameters using HOMO-LUMO energies. Thermal degradation pattern of the compounds was studied and Coats-Redfern method is used to determine kinetic parameters for complexes 1, 2, and 3 from thermal studies. The DNA interaction of these complexes was investigated by absorption, emission, and viscosity studies. From the spectral data, it was concluded that the complexes bind to DNA through groove mode of binding. The intrinsic binding constants (Kb) from absorption spectroscopy were 2.49 × 104, 2.48 × 104, and 2.64 × 104 M-1 for 1, 2, and 3, respectively, and Stern-Volmer quenching constants (Ksv) from emission spectroscopy were 0.21, 0.20, and 0.13, respectively. These complexes were screened for nuclease activity of pUC19 DNA, in the presence of H2O2. Discovery studio 2.1 software was used to evaluate binding affinity and interaction pattern of complexes with B-DNA receptor protein and the maximum dock score is seen for complex 2.