Preparation of transition metal 2-hydroxy-1-naphthoate complexes with hydrazine, their thermal characterization and use as precursors of nano metal oxides

Author(s): N.Arunadevi, S.Vairam

Reaction of aqueousmetal (Ni(II),Co(II), Cd(II), Zn(II), Cu(II) andMn(II)) nitrate/ acetate solution with an aqueous solution mixture of hydrazine and 2-hydroxy - 1- naphthoic acid yielded the complexes with formula, (N2H5)2[M{C10H6(COO)(O)}2(H2O)2] whereM(II) = Ni, Co, Cd, Zn, Cu and Mn in the pHrange of 4-7 and [M(N2H4){C10H6(COO)(O)}(H2O)2]whereM(II) = Ni, Co, Cd and Zn at the pH 9. They were characterized by the spectroscopic methods, IR, UV- visible and ESR,magnetic measurements, simultaneous TG–DTA methods and XRD. Hydrazinium metal naphthoate complexes undergo endothermic dehydration from105°C to 200°C and a strong exothermic decomposition between 336°C and 465°C, forming the respective metal oxides via unstable intermediate [M{C10H6(COO)(O)}], while neutral hydrazine complexes losewater and hydrazine exothermally in the range 192- 230°C, and then undergo strong exothermic decomposition above 230°C upto 451 °C to form metal oxides with no stable intermediates. Incineration of all the complexes at their decomposition temperatures gives metal oxides with the particle size in the range of 25 - 50 nm. The electronic spectra of the Ni, Co and Cu complexes reveal their probable geometry distorted octahedral with CN 6 which was further substantiated by magnetic susceptibility measurement and ESRstudy. The kinetic parameters for their decomposition have been evaluated by using integrated Coats-Redfern equation from TG data.

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