Magnetostructural correlations in exchange coupled phenoxo-, alkoxo-, and hydroxo-bridged dinuclear iron(III) compounds

A new semi-empirical magnetostructural correlation for exchange coupled dinuclear asymmetrically phenoxo-, alkoxo-, and hydroxo-bridged iron(III) complexes has been established. Based on an extensive comparison of the magnetic and structural parameters of 34 compounds, a strong correlation between the exchange coupling constant J and the averaged iron–oxygen distance, d, over the phenoxo-, alkoxo-, and hydroxo-bridge, could be demonstrated. This bridge provides much more efficient exchange pathway than every bridges over three atoms, e.g. acetate, phosphate, sulfate. The empirical relationship could be quantified in the form J=−107 exp(−6.8d). The magnitude of the FeO(X)Fe-bridging angle has no noticeable influence on the exchange coupling neither in case of complexes with identical nor in case of such with different bridging ligands.