A family of complexes with N-scorpionate-type and other N-donor ligands obtained in situ from pyrazole derivative and zerovalent cobalt. Physicochemical and cytotoxicity studies

Abstract

In situ syntheses and X-ray structures of three novel cationic–anionic complexes: [CoL¹Br][ZnL²L³ZnBr₅] (1), and [CoL¹Cl][ZnL³Br₃] (2) and [CoL¹Cl][ZnL³Cl₃] (3) L¹ = N,N,N-tris(3,5-dimethylpyrazol-1-ylmethyl)amine, L² = hexamethylenetetramine (urotropine), L³ = 3,5-dimethylpyrazole, have been reported. The presence of three different organic ligands (L¹, L² and L³) in isolated complexes results from various reactions taking place in the system which contains zerovalent cobalt and 1-hydroxymethyl-3,5-dimethylpyrazole as starting materials, in the presence of Zn(II) ions. The scorpionate-type ligand (L¹) formed in situ, possesses four potential donor sites, specifically three nitrogen donor atoms from the pyrazole rings, and one from tertiary amine, all of which coordinate to Co(II). They form a distorted trigonal bipyramidal [CoL¹X]⁺ cation whereas anionic parts include tetrahedrally coordinated zinc(II). The crystal structures and electronic (UV-Vis), infrared (FT-IR) spectra and thermal investigation of the isolated complexes have been analysed and discussed. Finally, the biological activity of 1–3 complexes was assessed. All the tested complexes expressed higher selectivity towards human cancer cells than towards human normal cells and showed a substantial antitumor activity against: colorectal adenocarcinomas Caco-2 and SW 620, hepatocellular carcinoma Hep G2 and lung carcinoma A549.