Molecular docking, DNA binding, thermal studies and antimicrobial activities of Schiff base complexes

Metal(II) complexes of 3-[(2-hydroxy-3-methoxybenzylidene)hydrazo]-1,3-dihydroindol-2-one (HL) were prepared, their compositions and physicochemical properties were characterized on the basis of elemental analysis, molar conductivity, ¹H NMR, UV–Vis, IR, mass spectroscopy, X-ray, magnetic measurements and thermogravimetric analysis (TGA). All results confirm that the novel complexes have 1:1 metal-to-ligand stoichiometric formulae [M(HL)(OAc)₂(OH₂)₂] (M

Cu(II)(1), Co(II)(2), Ni(II)(3) and Cd(II)(4)), octahedral configuration and the ligand behaves as a neutral bidentate forming six-membered chelating ring towards the metal ions, bonding through azomethine nitrogen and ketonic oxygen atoms. The molecular structures of the ligand and its metal complexes were also studied using quantum chemical calculations and shows that the keto form with hydrogen bond is more stable than other forms. The coordination geometry around all complexes (1–4) exhibits an octahedral geometry. The XRD studies show that both the ligand and Cu(II) complex show polycrystalline with Triclinic crystal system. The activation thermodynamic parameters, such as activation energy (E_a), enthalpy (ΔH), entropy (ΔS), and Gibbs free energy change of the decomposition (ΔG) are calculated using Coats–Redfern and Horowitz–Metzger methods. The ligand and its metal complexes (1–4) showed antimicrobial activity against bacterial species, Gram positive (Staphylococcus aureus), Gram negative (Escherichia coli) bacteria and yeast (Candida albicans), the ligand exhibited higher activity than the complexes. All investigated compounds were screened in vitro for their antioxidant, cytotoxic and antitumor activity. Molecular docking was used to predict the binding between HL ligand and the receptors of crystal structure of E. coli (3T88), crystal structure of S. aureus (3q8u) and crystal structure of C. albicans (1Q40).