Mossbauer spectroscopic study of oxo-centered mixed-valence trinuclear iron fumarate

Oxo-centered wmixed-valence trinuclear iron dicarboxylic acid complex iron fumarate [Fe3O(O2CCH=CHCO2)(3)(H2O)(3)].nH(2)O (n = 18-19), have been synthesized firstly. Variable temperature Mossbauer spectroscopy has been carried out to elucidate the rate of intramolecular electron transfer. It was found that the complex showed a temperature dependent mixed-valence state. At low temperature two quadrupole split doublets were observed corresponding to high spin Fe(III) and high spin Fe(II) state and a complete averaged valence state was observed at about 270 K At temperatures between 200 and 270 K the spectra showed relaxation effect as the electron transfer rate was comparable to the Mossbauer timescale (similar to10(-7) s).