Dioxo- and Oxovanadium(V) Complexes of Thiohydrazone ONS Donor Ligands:  Synthesis, Characterization, Reactivity, and Antiamoebic Activity

• Published in: Inorganic chemistry 2006-02, Vol.45 (3), p.1260-1269
• Main Authors: Maurya, Mannar R, Kumar, Amit, Bhat, Abdul R, Azam, Amir, Bader, Cerstin, Rehder, Dieter
• Format: Article
• Language: English
• Subjects: Animals; Antiprotozoal Agents - chemical synthesis; Antiprotozoal Agents - chemistry; Antiprotozoal Agents - pharmacology; Entamoeba histolytica - drug effects; Hydrazones - chemistry; In Vitro Techniques; Ligands; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Structure; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; Organometallic Compounds - pharmacology; Parasitic Sensitivity Tests; Sensitivity and Specificity; Species Specificity; Structure-Activity Relationship; Sulfhydryl Compounds - chemistry; Vanadium - chemistry
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic050811+

As a contribution to the development of novel vanadium complexes with pharmacologically interesting properties, two neutral dioxovanadium(V) complexes [VO2(Hpydx-sbdt)] (1) and [VO2(Hpydx-smdt)] (3) [H2pydx-sbdt (I) and H2pydx-smdt (II) are the Schiff bases derived from pyridoxal and S-benzyl- or S-methyldithiocarbazate] have been synthesized by the reaction of [VO(acac)2] and the potassium salts of the ligands in methanol followed by aerial oxidation. Heating of the methanolic solutions of these complexes yields the oxo-bridged binuclear complexes [{VO(pydx-sbdt)}2 μ-O] (2) and [{VO(pydx-smdt)}2 μ-O] (4). The crystals and molecular structures of 1, 3·1.5H2O, and 4·2CH3OH have been determined, confirming the ONS binding mode of the dianionic ligands in their thioenolate form. The ring nitrogen of the pyridoxal moiety is protonated in complexes 1 and 3. Acidification of 1 and 3 with HCl dissolved in methanol afforded oxohydroxo complexes, while in a methanolic KOH solution, the corresponding dioxo species K[VO2(pydx-sbdt/smdt)] are formed. Treatment of 1 and 3 with H2O2 yields (unstable) oxoperoxovanadium(V) complexes, the formation of which has been established spectrophotometrically. In vitro antiamoebic activities (against HM1:1MSS strain of Entamoeba histolytica) were established for all of the dioxo- and oxovanadium(V) complexes. The complexes 1, 2, and 4 were more effective than metronidazole, a commonly used drug against amoebiasis, suggesting that oxovanadium(V) complexes derived from thiohydrazones may open a new dimension in the therapy of amoebiasis.