Complex formation equilibria, DFT, docking, antioxidant and antimicrobial studies of iron(III) complexes involving Schiff bases derived from glucosamine or ethanolamine

Abstract

Acid-base equilibria of the iron(III) complexes of Schiff base synthesized from 2,6-diacetylpyridine and amino alcohol as, glucosamine or ethanolamine were investigated. These complexes are abbreviated as [Fe(dapGH2)(H2O)2]3+ and [Fe(dapEH2)(H2O)2]3+ for glucosamine and ethanolamine respectively. The pKa for induce ionization of the alcohol hydrogen atoms and the coordinated water molecules were also determined. The hepta-coordination mode of Fe(III) ion is evidenced by the hydrolysis data. The equilibrium constants were measured by potentiometric titration at 25 °C and ionic strength 0.1 M NaNO3 using the non linear least-squares program MINIQUAD-75. The speciations of the various complex species were obtained as a function of pH. DFT calculations were carried out for Schiff base that derived from ethanolamine (dapEH2) and its ferric complex. Molecular docking studies have proved that dapEH2 and [Fe(dapEH2)(H2O)2]3+ interact with ribosyltransferase (code: 3GEY) through the amino acids active sites. All suggested ligands and their ferric complexes were screened in vitro against some selected bacteria. The antioxidant properties of the ferric complexes were examined by the DPPH test. [Fe(dapEH2)(H2O)2]3+ showed higher antioxidant activity than the [Fe(dapGH2)(H2O)2]3+. The IC50 values of [Fe(dapEH2)(H2O)2]3+ complex and [Fe(dapGH2)(H2O)2]3+ complex were found to be 160.18 and 394.3 µg/ml respectively.