• Nashreen S Islam

      Articles written in Journal of Chemical Sciences

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

      Manish Bhattacharjee Mihir K Chaudhuri Nashreen S Islam

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      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.

    • Macromolecular peroxo complexes of Vanadium(V) and Molybdenum(VI): Catalytic activities and biochemical relevance

      Nashreen S Islam Jeena Jyoti Boruah

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      Our recent achievements concerning the synthesis and characterization of water soluble peroxo complexes of V(V) and Mo(VI) in macroligand environment, as well as some key features of biological relevance of these compounds, such as their hydrolytic stability, activity with phosphohydrolase enzyme vis-à-vis free peroxovanadium (pV) or peroxomolybdenum (pMo) complexes, and their activity in biomimetic oxidative bromination are presented here. Immobilization of pMo species on insoluble polymer matrices viz., amino acid functionalized Merrifield resins and poly(acrylonitrile) on the other hand, afforded a set of heterogeneous catalysts highly effective in facile organic transformations such as selective oxidation of organic sulfides and oxidative bromination of aromatic substrates by H2O2, at ambient temperature. The methodologies are straightforward, high-yielding, halogen-free and the catalysts afford easy regeneration. Our findings illustrate the various features which make the procedures sustainable and synthetically useful.

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