Coordination compounds of heterocyclic bases: synthesis, characterization, computational and biological studies

摘要

In this study, the geometry, spectroscopic characteristics andcoordination patternsof threebiologically active ligands and their Co(II) and Pd(II) complexes were explored using both experimental and theoretical techniques. The heterocyclic ligands (HL1-HL3) were synthesized by condensation reactions of 2-amino-6-methoxybenzothiazole with 2-hydroxy-1,4-naphthoquinone (1), 2-hydroxynaphthaldehyde (2) and 2-hydroxy-3-methoxybenzaldehyde (3). Co(II) and Pd(II) complexes of the ligands were subsequently synthesized and characterized using spectroscopic techniques, magnetic, conductance measurement and elemental analysis. The results of thespectroscopic analysis showed that the coordination of HL1 to the metal ions was through the oxygen atom of one of the carbonyl groups and the nitrogen atom of the deprotonated amine group. However, HL2 and HL3 were coordinated to the metal ions through the nitrogen atom of the azomethine group and the oxygen atom of the deprotonated hydroxyl group, resulting in N, O chromophores around the central metal ions. The magnetic moment and electronic spectra resultsof the metal complexes were consistent with the adoption of square planar geometry for the palladium(II) complexes and octahedral geometry for the cobalt(II) complexes. The compounds displayed good antibacterial activity against some clinically isolated bacterial strains of Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus cereus. Molecular docking studies gave possible molecular targets of the variousbacterial cellsby the compounds. In most cases, the newcompounds showed better molecular bindinginteractions than the crystallographic inhibitors. The antioxidant potentials of the ligands were evaluated using DPPH radical scavenging and ferrous ion chelating assays. The Fe(II) ion chelating potentials of the ligands were in the order HL3HL2HL1, with IC50 of 85 mu g/mL, 69 mu g/mL and 41 mu g/mL, respectively. Similarly, the DPP