title: Dioxo- and oxovanadium(V) complexes of thiohydrazone ONS donor ligands: synthesis, characterization, reactivity, and antiamoebic activity.
abstract: 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)}2mu-O] (2) and [{VO(pydx-smdt)}2mu-O] (4). The crystals and molecular structures of 1, 3 x 1.5H2O, and 4 x 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.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247 667, India. mannarfcy@yahoo.co.in
authors.forename: Mannar R
authors.initials: MR
authors.lastname: Maurya
authors.forename: Amit
authors.initials: A
authors.lastname: Kumar
authors.forename: Abdul R
authors.initials: AR
authors.lastname: Bhat
authors.forename: Amir
authors.initials: A
authors.lastname: Azam
authors.forename: Cerstin
authors.initials: C
authors.lastname: Bader
authors.forename: Dieter
authors.initials: D
authors.lastname: Rehder
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D004748:Entamoeba histolytica / Q000187:drug effects*; D006835:Hydrazones / Q000737:chemistry*; D066298:In Vitro Techniques; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D021261:Parasitic Sensitivity Tests; D012680:Sensitivity and Specificity; D013045:Species Specificity; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D014639:Vanadium / Q000737:chemistry*
chemical_list: D000981:Antiprotozoal Agents; D006835:Hydrazones; D008024:Ligands; D009942:Organometallic Compounds; D013438:Sulfhydryl Compounds; D014639:Vanadium