Nashreen S. Islam

Polymer-Anchored Peroxo Compounds of Vanadium(V) and Molybdenum(VI): Synthesis, Stability, and Their Activities with Alkaline Phosphatase and Catalase

We generated a series of new polymer-bound peroxo complexes of vanadium(V) and molybdenum(VI) of the type [VO(O(2))(2)(sulfonate)]-PSS [PSS = poly(sodium 4-styrene sulfonate)] (PV(3)), [V(2)O(2)(O(2))(4)(carboxylate)VO(O(2))(2)(sulfonate)]-PSSM [PSSM = poly(sodium styrene sulfonate-co-maleate)] (PV(4)), [Mo(2)O(2)(O(2))(4)(carboxylate)]-PA [PA = poly(sodium acrylate)] (PMo(1)), [MoO(O(2))(2)(carboxylate)]-PMA [PMA = poly(sodium methacrylate)] (PMo(2)), and [MoO(O(2))(2)(amide)]-PAm [PAm = poly(acrylamide)] (PMo(3)) by reacting V(2)O(5) (for PV(3) and PV(4)) or H(2)MoO(4) (for PMo(1), PMo(2), and PMo(3)) with H(2)O(2) and the respective water-soluble macromolecular ligand at pH 5-6. The compounds were characterized by elemental analysis (CHN and energy-dispersive X-ray spectroscopy), spectral studies (UV-vis, IR, (13)C NMR, (51)V NMR, and (95) Mo NMR), thermal (TGA) as well as scanning electron micrographs (SEM), and EDX analysis. It has been demonstrated that compounds retain their structural integrity in solutions of a wide range of pH values and are approximately 100 times weaker as substrate to the enzyme catalase relative to H(2)O(2), its natural substrate. The effect of the title compounds, along with previously reported compounds [V(2)O(2)(O(2))(4)(carboxylate)]-PA (PV(1)) and [VO(O(2))(2)(carboxylate)]-PMA (PV(2)) on rabbit intestine alkaline phosphatase (ALP) has been investigated and compared with the effect induced by the free diperoxometallates viz. Na[VO(O(2))(2)(H(2)O)] (DPV), [MoO(O(2))(2)(glycine)(H(2)O)] (DMo(1)), and [MoO(O(2))(2)(asparagine)(H(2)O)] (DMo(2)). It has been observed that although all the compounds tested are potent inhibitors of the enzyme, the polymer-bound and neat complexes act via distinct mechanisms. Each of the macromolecular compounds is a classical noncompetitive inhibitor of ALP. In contrast, the action of neat pV and heteroligand pMo compounds on the enzyme function is consistent with a mixed type of inhibition.

Synthesis, characterisation and physicochemical properties of peroxo-vanadium(v) complexes with glycine as the hetero-ligand

Abstract The first glycineperoxo complexes of vanadium- (V), NH4[VO(O2)2GlyH]·H2O (1), K[VO(O2)2- GlyH]·H2O (2)and [V2O2(O2)3(GlyH)2(H2O)2] (3) have been synthesised from the reaction of V2O5 with hydrogen peroxide and glycine (GlyH) at pH 3–4 (1 and 2) and pH 2 (3), respectively. The compounds have been characterised by elemental analysis, magnetic susceptibility and ESR, UVVis and IR spectroscopy. While glycine, occurring in its zwitterionic form, is coordinated to the V(V) centre in a monodentate fashion through its carboxylic oxygen, the peroxides in 1 and 2 occur as terminal bidentate ones. In compound 3 one of the peroxide ligands is present as a μ-peroxo group. Typically, an aqueous solution of 2 exhibits peroxoV(V) LMCT bands at 328 and in the 200–190 nm region, whereas complex 3 shows only one broad LMCT band at 310–330 nm.

Reactivity of metal-bound peroxides; alkali triperoxovanadate(V) trihydrates, A[V(O2)3]·3H2O (A = Na or K), as oxidants resembling alkali—H2O2 reagent for some organic substrates

Abstract The efficacy of the triperoxovanadium(V) complexes, A[V(O2)3]·3H2O (A = Na or K), as potential oxidants with respect to certain organic substrates has been investigated. Aqueous solutions of the complexes are basic (pH ca. 11) in nature. The complexes efficiently oxidise an α,β-unsaturated ketone to the corresponding epoxide and benzonitrile to benzamide. Such reactions are usually accomplished using alkaline-H2O2 reagent. The complexes are also capable of bringing about Bayer-Villiger-type oxidation and oxidise benzil to benzoic acid. The peroxo-depleted vanadium product, isolated after the oxidations, has been identified as a diperoxovanadate(V) complex, [VO(O2)2(H2O)]−.

Reactions of vanadium(V) with alkali sulphate or thiocyanate. Evidence for the formation of oxodiperoxovanadate(V) complexes containing ionic sulphate

SummaryVanadium pentoxide (1 mol) reacts with alkali sulphate (2 mol) or alkali thiocyanate (2 mol) and an excess of hydrogen peroxide at pH 7–8, maintained by the addition of the corresponding alkali hydroxide, to produce yellow oxodiperoxovanadate(V) complexes containing sulphate. The compounds were characterised by elemental analyses, molar conductance measurements, and i.r. and laser Raman spectroscopic studies. The compounds are formulated as M[VO(O2)2] · M2SO4 (M=alkali metal). The peroxide has been shown to be bonded to the vanadium(V) centre in a triangular bidentate (C2v) manner.

Reaction of sodium bismuthate with fluoride in an aqueous medium to give fluoro compounds of bismuth(III)

Abstract Bismuth(V) as sodium bismuthate, NaBiO 3 , is quantitativelyreduced to bismuth(III) in aqueous hydrofluoric acid at theexpense of water oxidation. NaBiO 3 , with aqueous hydrofluoricacid and a solution of ammonium fluoride in aqueous hydrofluoricacid, gave trifluorobismuth(III) monohydrate, BiF 3 .H 2 O, andammonium tetrafluorobismuthate(III), NH 4 BiF 4 , respectively.BiF 3 .H 2 O undergoes dehydrofluoridation (-2HF) at 350-400°C inthe presence of air to produce BiOF. The results of chemicalanalyses and infrared and laser Raman studies have been used tocharacterise the compounds.

Newer manifestations of reactivity of coordinated peroxide at metal and non-metal centres

Newer reactions of coordinated peroxide at metal and non-metal centres are described. Reactions of peroxo-metal complexes with SO2(g), NO2(g), and CO2(g) have been carried out in aqueous medium. Typically, reactions of a highly peroxygenated metal complex, A[V(O2)3]·3H2O (A=Na,K), follow an unprecedented sequence. The deep blue ESR-silent solution of A[V(O2)3]·3H2O reacts to produce a yellow, ESR-inactive solution that on further reaction with the chosen substrate affords a green-blue ESR-active (cf. VO2+) solution. The reaction proceeds through distinct steps such that, first, one of the coordinated peroxides undergoes a two-electron irreversible cleavage of the O-O bond leading to a diperoxy-mono(sulphato)vanadate(V) intermediate, [(O2)2V-O-SO3]−, that readily undergoes hydrolysis to produce H2SO4 and an aquaoxo-diperoxovanadate(V) complex, [VO(O2)2H2O]−. The latter complex reacts with more SO2(g) causing reduction of vanadium (V) to vanadium (IV) and conversion of coordinated peroxide to coordinated sulphate producing the bis(sulphato)vanadyl complex, [VO(SO2)2(H2O)2]2−.Further, the reaction of A[V(O2)3]·3H2O with SO2(g) in the presence of AF, yielding a ternary fluoro(sulphato)oxovanadate (IV) complex A4[VO(SO4)2F2(H2O)]·2H2O, serves as a paradigm for the synthesis of ternary complexes of vanadyl, VO2+. It is also evidentinteralia that the [V(O2)3]− species offers potential as a novel synthon.Some recent developments in the peroxo-chemistry of B, C, P and As are highlighted. Heretofore unreported salts of peroxo phosphoric acid, viz. (NH4)3[PO3(O2)]·3H2O and Na3[PO3(O2)]·3H2O, have been synthesized and their potential as oxidants explored. Their role in oxidising organic substances is highlighted, especially as a substitute for the alkaline-H2O2 reagent.