Structural architectures and biological properties of main group bismuth(III) iodide complexes with heterocyclic thioamides

Abstract

A series of mononuclear, dinuclear and polynuclear bismuth(III) iodide complexes (1–5) bearing heterocyclic thioamide ligands, 2-mercapto-3,4,5,6-tetrahydro-pyrimidine (tHPMT), 2-mercapto-benzimidazole (MBZIM), 2-mercapto-1-methylimidazole (MMI), 2-mercaptobenzothiazole (MBZT) and 2-mercaptopyridine (PYT), have been synthesized and characterized by melting point, elemental analysis, FT-IR spectroscopy, Raman spectroscopy, 1H, 13C NMR spectroscopy, UV–Vis spectroscopy and Thermal Gravimetry-Differential Thermal Analysis (TG-DTA). Moreover, the crystal structures of 1–5 have been also determined with single crystal X-ray diffraction analysis. The use of the above mentioned heterocyclic thioamide ligands have allowed synthesis of the first examples of bismuth(III) iodide thioamide complexes. {[BiI3(tHPMT)3]} (1) is the first structural example of a neutral mononuclear bismuth(III) iodide complex with octahedral geometry around the bismuth(III) ion with meridional conformation. {[BiI2(µ2-I)(MBZIM)2]2} (2) is the first example of a dinuclear bismuth(III) iodide complex with octahedral geometry around the bismuth(III) ion with trans-S/cis-I arrangement. {[BiI(µ2-I)2(MMI)]n} (3) and {[BiI(µ2-I)2(MBZT)]n·CH3OH} (4) are the first examples of the polynuclear bismuth(III) iodide complexes with octahedral geometry around the bismuth(III) ions. The ligand molecules are coordinated via the thione sulfur atoms in both complexes but in complex 3, ligand molecules are trans to each other in polymeric chain while, in complex 4, ligand molecules are cis to each other in polymeric chain. {[BiI(µ2-S,N-PYT)2]n} (5) is the first example of a polynuclear bismuth(III) iodide complex with pentagonal bipyramidal geometry around the bismuth(III) ions. The seven coordinate bismuth(III) atom has a N2S4I-donor set consisting of one iodine atom and two chelating and bridging μ2-S,N (η2-S:η1-N) pyridine-2-thionate anions.Complexes 1–5 were evaluated for their in vitro cytotoxic activity against human adenocarcinoma cervix (HeLa) and breast (MCF-7) cancer cells. The toxicity of the complexes was studied against human fetal lung fibroblast cells (MRC-5). The influence of 1–5, upon the catalytic peroxidation of the linoleic acid by the enzyme lipoxygenase (LOX), was evaluated experimentally.