Magnetic Exchange Interactions in Oxo-Bridged Diiron(III) Systems: Density Functional Calculations Coupling the Broken Symmetry Approach

Abstract

The calculations on magnetic exchange interaction of Cl3FeOFeCl32- and the related modeling compounds were performed by using the density functional theory coupling the broken symmetry approach. The calculated results show the absence of a direct Cl3Fe---FeCl3 magnetic coupling and the effect of the terminal Cl ligands on magnetic exchange interaction in [Fe−O−Fe]4+, while the protonation of μ-oxo bridge reduces significantly the magnetic coupling constant J value. On the other hand, the J value is insensitive to variation of the Fe−O−Fe angle; however, the dependence of the J value on the Fe−O distance can be expressed as an exponential function, while the J value keeps a constant to the variation of the O−H distance in the μ-hydroxo and μ-aqua bridges. Molecular orbital interaction is applied to explain the magnetic exchange interaction in μ-oxo bridged iron(III) dimers. The validity of qualitative magneto−structural correlation for the models used is further confirmed by full geometry optimization.