Electron paramagnetic resonance studies of metal–metal interactions in manganese(II) complexes. The 10/3 effect

Abstract

A multi-frequency e.p.r. study has revealed six Mn(II) complexes, Mn(CH₃COO)₂4H₂O, Mn(CHOO)₂2H₂O, Mn(C₄H₄O₆), Mn₃(PO₄)₂, MnSO₄H₂O and MnBr₂ for which the linewidth changes as a function of observation frequency. These changes, associated with the 10/3 effect, have provided a basis for the estimation of the isotropic spin-spin exchange constant, J, at room temperature. In all cases where a comparison was possible, the J values derived from the e.p.r. studies are in good agreement with the values obtained by low temperature techniques. In addition, an assessment of the precision of the determination is made, which includes both experimental and theoretical contributions.

These six new examples include nearly half of the total known metal ion complexes which exhibit this effect in the usual e.p.r. frequency range.