Electronic Structure of Oxo-Bridged Iron(III) Dimers

Harvey J. Schugar1, George R. Rossman2, Collin G. Barraclough3, Harry B. Gray2

 1Rutgers University
 2California Institute of Technology
3University of Melbourne


Magnetic susceptibility results and extensive electronic, infrared, and Mossbauer spectral data are presented for enH2[(FeHEDTA)2O]ˇ6H2O, Na4[(FeEDTA)2O]ˇ12 H2O, FeHEDTAˇ H2O, and NaFeEDTAˇ3H2O (HEDTA = N-hydroxoethylethylenediaminetriacetate, EDTA = ethylenediaminetetraacetate, and enH22+ = ethylenediammonium cation). The magnetic and spectral data establish an electronic structural model for the oxo-bridged dimers in which pairs of S = 5/2 Fe(III) ions interact antiferromagnetically, with J ≈ -95 cm-1. The oxo-bridged dimers show marked intensity enhancement of the one-center Fe(III) ligand-field bands. There are also several uv bands which are interpreted as arising from simultaneous electronic excitations of Fe(III) pairs. A simple high-spin ligand-field model modified by spin-spin interaction is judged to be considerably more appropriate than the Dunitz-Orgel molecular orbital approach as a vehicle for describing oxo-bridged Fe(III) dimers.

Magnetic susceptibility

Gram magnetic susceptibilities of enH2[(FeHEDTA)2O]ˇ6H2O (a) and Na4[(FeEDTA)2O]ˇ12 H2O (b) as a function of temperature

last updated: 28-Jul-2023