Synthesis, Characterization and Bioassay of Some Antimony V Organometallics

To better understand the biological/medicinal potential of the antimonial agents we synthesized complexes of pentavalent antimony with a variety of aliphatic, aromatic and heterocyclic carboxylic acids of established biological importance. Different series of antimony(V) organometallics of the general formula [M(O 2 CR) 2 R'' 3 ], where M = Sb, R = pendent groups of carboxylate moiety, and R''= aryl, p-tolyl, o-tolyl, m-tolyl, cyclohexyl, benzyl and 2,5-dimethylphenyl. These complexes have been synthesized, purified and characterized by m.p., elemental analysis, FT-IR, multinuclear ( 1 H, 13 C) NMR spectroscopy and single crystal X-ray diffraction analysis. The structural analysis reveals that these complexes are mononuclear in solution and solid state. In these metallic species, the carboxylates ligands bind to the antimony(V) atom using oxygen atoms and occupy axial position.The spectroscopic data suggest that the ligands are attached to the central metal atom through oxygen atoms and achieve slightly distorted trigonal bipyramidal geometry as confirmed by X-ray crystallographic analysis. Some of the antimonials have also been initially examined for their leishmanicidal properties and shown significant activity against promastigotes and macrophages or primary human fibroblasts. Cell viability was assessed spectrophotometrically at 550 nm with the reference wavelength of 630 nm. The complexes have been screened for their in vitro cytotoxicity in human cell lines carcinomas A498 (renal), EVSA-T (breast), H226 (lung), IGROV (ovarian), M19 (melanoma-skin), MCF-7 (breast) and WIDR (colon). They show a good to moderate cytotoxicity against these seven human cancer cell lines in comparison to that of the less active standard chemotherapeutic drugs.