Synthesis, Spectroscopic Studies, and Biological Activity of Some New N2O2 Tetradentate Schiff Base Metal Complexes

Abstract

The new tetradentate Schiff base N,N′-ethylene bis[1-ethyl-6-fluoro-4-imine-7-(piperazine-1-yl)-quinoline-3-carboxylic acid] (Nor-en) has been synthesized. Its chelated complexes with Co(II), Ni(II), Cu(II), Zn(II), Y(III), Zr(IV), La(III), and U(VI) are characterized using molar conductivity, magnetic moment, FT-IR, UV-Vis, ¹H NMR, and mass spectra, and thermal analysis. It is determined that the complexes have monomeric structures and exist in the octahedral configuration. The molar conductance values indicate the electrolytic nature of the complexes. According to the spectroscopic data, the complexes share the same coordination environment around the metal ions, consisting of N₂O₂ and one or two water molecules. The thermodynamic parameters (activation energy, E*, entropy, ΔS*, enthalpy, ΔH*, and Gibbs free energy, ΔG*) are calculated using Coats-Redfern and Horowitz-Metzger methods. The carried out tests indicate the compounds’ high antibacterial activity against Staphylococcus aureus, Bacillus cereus, and Salmonella typhi. Anticancer activity of the ligand and its metal complexes is evaluated against HepG-2 cells (human Hepatocellular carcinoma) and determined to be very low.