Synthesis and Mossbauer spectroscopy of oxo-centered mixed-valence trinuclear iron fumarate and iron malonate complexes

Oxo-centered trinuclear mixed-valence iron fumarate [Fe3O(O2CCH=CHCO2)(3)(H2O)(3)].nH(2)O and iron malonate [Fe3O(O2CCH2CO2)(3)(H2O)(3)] have been prepared and studied by variable temperature Mossbauer spectroscopy. Iron fumarate complex showed a temperature dependent valence delocalization process. At 6 K two quadrupole split doublets corresponding to high-spin Fe(III) and high-spin Fe(II) state with an area ratio of similar to2:1 were observed and at 298 K there was only an averaged singlet peak. On the other hand, malonate complex showed a localized valence state of high-spin Fe(III) and Fe(II) from low temperature to room temperature only with a slight variation in area ratio and spectral line broadening for Fe(II).