• Use of aqueous DMSO in resolving ‘proton ambiguity’ in the formation of monocomplexes of iron(III)

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    • Keywords


      Proton ambiguity; iron(III) complexes; aqueous DMSO; temperature jump; stopped flow

    • Abstract


      The formation of FeL2+ (L=N3, SCN) in H2O-dimethylsulphoxide (DMSO) mixtures was studied by equilibrium, stopped flow and temperature jump observations. The acid dissociation constants associated with LH and Fe(H2O)63+ and the formation constants associated with FeL2+ were determined at various solvent compositions. In kinetic studies, the solvent composition dependence of the overall equilibration rate was explained in terms of equations predicted by a reaction scheme which includes DMSO coordinated species. Analysis of results on the basis of these equations identified Fe·OH2+·HN3 and Fe3+·SCN as the dominant transition states contributing to pH-independent paths of formation of FeL2+ in the cases of N3 and SCN respectively. Thus, the results which support the Eigen-Tamm-Wilkins mechanism have resolved the mechanistic ambiguity in the pH-independent paths of formation of FeL2+. It is also shown that we cannot neglect species such as FeOH·HN32+, Fe·OH·N3+ and Fe·HN33+ while accounting for the kinetic behaviour.

    • Author Affiliations


      G Krishnamoorthy1 B S Prabhananda1

      1. Chemical Physics Group, Tata Institute of Fundamental Research, Bombay - 400 005, India
    • Dates

  • Journal of Chemical Sciences | News

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