Synthesis, Structure, and Biological Activity of Cu(II), Ni(II), and Co(II) Complexes of N-[2-[(E)-2-Furylmethyliminomethyl)phenyl]-4-methylbenzenesulfonamide

N-[2-[(E)-2-Furylmethyliminomethyl)phenyl]-4-methylbenzenesulfonamide (HL) and Cu(II), Ni(II), and Co(II) complexes ML₂ based on HL were synthesized. The composition, structure, and spectral properties of the products were studied by elemental analysis and ¹H NMR (for HL), IR, and UV/Vis spectroscopy. The crystal structures of the Cu(II), Ni(II), and Co(II) complexes were determined by X-ray diffraction (CCDC nos. 2420740, 2420738, and 2420739, respectively). It was shown that two deprotonated ligands are chelated to metal ions via the nitrogen atoms of the tosylamine and azomethine moieties. The coordination geometry of copper(II), nickel(II), and cobalt(II) ions corresponds to a strongly distorted tetrahedron. The UV/Vis spectra of HL and the metal complexes were studied. The azomethine HL and the metal complexes were tested for the antibacterial, protistocidal, and fungistatic activities. All compounds were found to have no fungistatic activity against Penicillium italicum and no antibacterial activity against Staphylococcus aureus or Escherichia coli, and only HL showed a protistoidal activity against Colpoda steinii at the level of the reference compound chloroquine.