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The synthesis and spectral and magnetic properties of some iron sulfonate compounds Haynes, John Stephen

Abstract

The work described in this thesis involved the synthesis and characterisation of a number of iron sulfonate compounds, Fe(XSO₃)[sub n], where X is CF₃, CH₃ and p-CH₃C₆H₄, and n is 2 or 3. The work is an attempt to probe the coordinating ability of the XSO₃ anion and extends previous studies in this laboratory on other divalent metal sulfonates. The physical methods of characterisation included infrared, electronic and Mossbauer spectroscopy and magnetic susceptibility measurements. These techniques have enabled a detailed picture of the structure of the iron(II) sulfonates to be envisaged. The general structure proposed involves terdentate bridging anions, each anion bridging to three different metal centres resulting in FeO₆ octahedra; the distortions from perfect octahedral geometry have also been analysed. Iron(II) methanesulfonate was found to exist in two closely related structural forms, the a-isomer containing trigonally compressed FeO₆ octahedra and the β-isomer containing trigonally elongated FeO₆ octahedra. No evidence for structural isomerism was found for Fe(CF₃SO₃)₂ or Fe(p-CH₃C₆H₄SO₃) but vibrational spectroscopy revealed structural isomerism in other (M(CH₃SO₃)₂ compounds, where M is Co and Zn. Both α- and β-Fe(CH₃SO₃)₂ showed unusual magnetic properties II and Mossbauer spectroscopy enabled an antiferromagnetic phase transition to be observed in the case of the β-isomer. Preliminary results for the iron(III) sulfonates, Fe(CF₃SO₃)₃, Fe(CH₃SO₃)₃ and Fe(p-CH₃C₆H₄SO₃)₃ indiate antiferromagnetic exchange in these compounds.

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