Structural Motifs and Biological Studies of New Antimony(III) Iodide Complexes with Thiones

Eight new antimony(III) iodide complexes of the heterocyclic thioamides, 2-mercapto-1-methylimidazole (MMI), 2-mercaptobenzimidazole (MBZIM), 5-ethoxy-2-mercaptobenzimidazole (EtMBZIM), 2-mercaptothiazolidine (MTZD), 3-methyl-2-mercaptobenzothiazole (NMeMBZT), 2-mercapto-3,4,5,6-tetrahydropyhmidine (tHPMT), 2-mercaptopyridine (PYT), and 2-mercaptopyrimidine (PMT) of formulas {[Sbl(3)(MMl)(2)]center dot MeOH} (1), (Sbl(3)(MBZIM)(2)] (2), {[Sbl(2)(mu(2)-l)- (EtMBZIM)(2)](2)center dot H2O} (3), [Sbl(3)(MTZD)] (4), [(NMeMBZT)Sbl(2)(mu(2)-l)(2)(mu(2)-S-NMeMBZT)Sbl(2) (NMeMBZT)] (5), {[Sbl(3)(tHPMT)(3)]center dot MeOH} (6), [Sbl(3)(PYT)] (7), and [Sbl(3)(PMT)(2)] (8), have been synthesized and characterized by elemental analysis, FPR spectroscopy, FT-Raman spectroscopy, and TG-DTA analysis. The crystal structures of 3, 4, 5, 6, and 7 were also determined by X-ray diffraction. The complexes show interesting structural motifs. Complex 6 is a monomer, With octahedral (Oh) geometry around the metal ion formed by three sulfur and three iodide atoms. Complexes 3 and 5 are dimers, with a square pyramidal (SP) geometry in each monomeric unit, while complexes 4 and 7 are polymers with pseudotrigonal bipyramidal (psi-TBP). Two or three sulfur atoms from thioamide ligands and three iodide atoms are bound to Sb atoms forming building blocks for the dimers and polymers. Strong intramolecular interactions between mu(2)(-)l and/or mu(2)-S and Sb atoms stabilize both structures. In dimer complex 5, two terminal iodide and one terminal sulfur atom are bonded to the Sb ion, while two mu(2)-1 and one mu(2)-S bridging atoms bridge the metal ions forming psi-Oh geometry. Computational studies using multivariant linear regression (MLR) and artificial neural networks (ANN) and considering biological results (50% inhibitory concentration, IC50) as dependent variables derived a theoretical equation for IC50 values of the complexes studied. The calculated IC50 values are compared satisfactorily with the experimental inhibitory activity of the complexes measured. Complexes 3-7 were used to study their influence upon the catalytic peroxidation of linoleic acid by the enzyme Lipoxygenase (LOX). Compounds 1-8 were also tested for in vitro cytotoxicity, and they showed mostly a moderate cytostatc activity against a variety of tumor cell lines but comparable With those found for the antimony(III) chloride and bromide complexes, reported earlier [Ozturk et al. Inorg. Chem. 2007, 46, 2861-2866; Ozturk et al. Inorg. Chem. 2009, 48, 2233-2245].