Synthesis, structure, and biological activities of mixed-ligand nickel(II) and cobalt(II) complexes of benzoylhydrazone 2-(N-tosylamino)benzaldehyde and benzimidazole derivatives

Abstract

The synthesis of four new nickel(II) and cobalt(II) complexes based on 2-(N-tosylamino)benzaldehyde benzoylhydrazone (H2L), with additional heterocyclic donor ligands Ln, NiHLLn and CoHLLn(Ac) (n = 1, 2), has been carried out (where L1 = 1-propyl-2-aminobenzimazole, L2 = 1-hexyl-2-aminobenzimidazole, and Ac = acetate). The compositions and structures of these compounds were determined using elemental analysis, 1H NMR spectroscopy, and IR spectroscopy. Single-crystal X-ray diffraction was used to determine the molecular structures of the nickel(II) and cobalt(II) complexes. It has been found that in NiHLLn, the ions of nickel(II) have a distorted flat-square environment, whereas the coordination sphere of the cobalt(II) in CoHLLn(Ac) can be described as a strongly distorted square pyramid due to additional coordination with the acetate group. The biological activity of the compounds has been investigated. The results showed that all complexes exhibited significantly higher antiprotozoal activity compared to the reference drug chloroquine.