• Oindrila Das

      Articles written in Journal of Chemical Sciences

    • Iron and cobalt complexes of 4,4,9,9-tetramethyl-5,8-diazadodecane-2, 11-dione dioxime ligand: Synthesis, characterization and reactivity studies

      Oindrila Das Sayanti Chatterjee Tapan Kanti Paine

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      Two oximate bridged dinuclear complexes [Co$^{\text{II}}_2$ (HL)2](ClO4)2 (1) and [Fe^{text{II}}_2$ (HL)2](ClO4)2 (2), and a biomimetic iron(III)-catecholate complex [FeIII(HL)(DBC)] (3) of a dioxime ligand (H2L = 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11-dione dioxime and DBCH2 = 3,5-di-tert-butylcatechol) were synthesized and characterized. X-ray single-crystal structures of both the dinuclear complexes exhibit an out-of-plane oximate bridge where the six-membered M2(NO)2 ring adopt a boat conformation with the metal ions in a fivecoordinate distorted trigonal bipyramidal geometry. Complexes 1 and 2 react with dioxygen at ambient condition to form the corresponding hydroxo- or oxo-bridged dinuclear cobalt(III) or iron(III) complexes. On the other hand, the iron(III)-catecholate complex (3) activate dioxygen to undergo oxidative C-C bond cleavage of catechol. The selective formation of extradiol catechol cleavage products in the reaction of 3 with dioxygen mimics the functional aspect of extradiol-cleaving catechol dioxygenases. The flexibility of ligand backbone is proposed to control the dioxygen reactivity of metal complexes.

    • Mechanistic studies of copper(II)-mediated oxidation of vic-dioxime to furoxan

      Oindrila Das Tapan Kanti Paine

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      The oxidation of vic-dioximes to furoxans by copper(II) perchlorate in acetonitrile as the oxidant has been discussed. This method was found to be applicable for a broad range of vic-dioximes. Copper complexes of 1,10-phenanthroline derived furoxans were isolated by oxidation of the corresponding copper(II) complexes of 1,10-phenanthroline based dioximes. In exploring the mechanism of copper(II)-mediated oxidative cyclization of vic-dioxime, a transient blue species was observed in the reaction pathway. Based on the spectroscopic signatures and reactivity patterns, the intermediate was proposed to be a dioximatecopper(II)-dinitrosoalkene complex. These results along with the role of metal ion and solvent in the oxidative transformation reaction are discussed in this review.

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