Antimony(III) halide compounds of thioureas: Structures and biological activity

Abstract

Antimony(III) halide compounds (SbX3, X=Cl and Br) of thioureas; tetramethylthiourea (TMTU), N,N′-diethylthiourea (DETU) and 1,3-diisopropyl-2-thiourea (DIPTU) of formulae {[SbCl3(TMTU)]n} (1), {[SbBr3(TMTU)]n} (2), {[mer-SbCl3(DIPTU)3] [fac-SbCl3(DIPTU)3] C6H6} (3) and {[SbBr2(DETU)2]+·Br−}n (4) were synthesized. The complexes were characterized by their melting point, elemental analysis, FT-IR spectroscopy, FT-Raman spectroscopy, 1H and 13C NMR spectroscopy and Thermal Gravimetry-Differential Thermal Analysis (TG-DTA). The crystal and molecular structures of complexes 2–4 were determined with single crystal X-ray diffraction analysis. Compounds 1 and 2 are polymers with pseudotrigonal–bipyramidal (ψ-TBP) geometry in each monomeric unit. Compound 3 is a monomer with octahedral (Oh) geometry around Sb(III). Two different coordination modes of the ligands around antimony ions are observed in 3 forming two units. One with meridional orientation and the other with facial one. This complex is the first example of polymeric antimony(III) where two sequential antimony atoms have two different coordination modes. Two sulfur atoms and two bromines form a pseudotrigonal–bipyramidal cationic [SbBr2(L)2]+ part with a bromide as counter anion in complex 4. Complexes 1–4 and their ligands were evaluated for their in vitro cytotoxic activity against human breast adenocarcinoma (MCF-7) and human cervical adenocarcinoma (HeLa) cells. Principal components analysis (PCA) was performed to discriminate the significant physicochemical molecular descriptors while regression analysis successfully relates the experimental inhibitory concentrations, (IC50) to the independent variables indexed by PCA.