Nickel (II) and Copper (II) Schiff Base Derivatives: Design, Characterization, Biological Activity

Abstract

This work presents the designing and characterization of two novel metal complexes derived from a Schiff base, N,N’-ethane-1,2-diylbis[1-(2-chloroquinolin-3-yl)methanimine] (EBCQ), coordinated with Ni (II) (NiEBCQ), and Cu (II) (CuEBCQ). Structures of the metal complex derivatives were proposed utilizing a variety of analytical methods having elemental analysis, ultraviolet-visible spectroscopy, mass spectroscopy, infrared spectroscopy, magnetic properties, conductivity measurement, and thermal analysis. The obtained data revealed octahedral geometries for both NiEBCQ and CuEBCQ complexes, denoted as [Ni(EBCQ)(H₂O)₂(Cl)₂] and [Cu(EBCQ)(H₂O)₂(Cl)₂], respectively. Density functional theory computations were employed for confirming the molecular structures and exploring quantum chemical parameters of both EBCQ and its metal complex derivatives. The anti-inflammatory results reveal that the EBCQ ligand and its metal complexes, NiEBCQ, and CuEBCQ, exhibit varying degrees of inhibition, with CuEBCQ showing the highest potency. CuEBCQ achieved 89.80% inhibition at 300 µM, with an IC₅₀ value of 86.38 µM, indicating its superior anti-inflammatory activity compared to NiEBCQ (IC₅₀ of 92.33 µM) and the ligand EBCQ (IC₅₀ of 169.07 µM). In the antioxidant assays, the CuEBCQ complex again showed the most pronounced activity, achieving an IC₅₀ of 74.16 µM, outperforming both NiEBCQ (IC₅₀ of 89.06 µM) and the EBCQ ligand (IC₅₀ of 101.58 µM). The antibacterial tests confirmed the metal complexes' superiority, particularly CuEBCQ, which displayed excellent inhibition against Bacillus cereus compared to the ligand. Molecular docking studies targeting specific proteins (5IKT for human cyclo-oxygenase-2, and 5IJT for human peroxiredoxin 2) were performed to assess the binding affinities and interactions of EBCQ and its metal complex derivatives. The results propose promising potential for the application of EBCQ and its metal complexes as novel therapeutic agents with diverse biological activities. Finally, antibacterial effectiveness of the ligand and its complexes were monitored opposed to several Gram-positive and Gram-negative bacteria.