Dependence of the rate of intramolecular electron transfer on crystal form in mixed-valence trinuclear iron phenylacetate complex

Abstract A dependence of the rate of intramolecular electron transfer on crystal form in mixed-valence trinuclear iron phenylacetate, [Fe 2 III Fe II O(O 2 CCH 2 Ph) 6 (py) 3 ](py=pyridine), was found. This complex was obtained in two different crystal forms: a columnar and a needle crystal form. Mo¨ssbauer spectra of the columnar crystals showed a temperature-dependent valence detrapping, whereas the needle crystals showed a trapped mixed-valence state from a lower temperature up to room temperature. The structure of the columnar crystal was determined by single-crystal X-ray diffraction. The complex is located on the C 2 axis passing through central O Fe; thus, there are two crystallography inequivalent iron sites. The Fe Fe distances are 3.305(1) and 3.311(1)A˚, in agreement with their being indistinguishable on the 57 Fe Mo¨ssbauer time-scale (∼10 −7 –10 −8 s). There is no evidence indicating intermolecular π-π interactions through the phenyl groups and/or pyridine ligands.