Ferromagnetic exchange in a twisted, oxime-bridged [MnIII2] dimer

The dimeric complex [MnIII2(Naphth-sao)2(Naphth-saoH)2(MeOH)2]·4MeOH (1·4MeOH), acts as a simple model complex with which to examine the magneto-structural relationship in polymetallic, oxime-bridged MnIII complexes. Dc magnetic susceptibility studies reveal that ferromagnetic exchange is mediated through the heavily twisted Mn–O–N–Mn moiety (J = +1.24 cm−1) with magnetisation measurements at low temperatures and high fields suggesting significant anisotropy. Simulations of high field, high frequency EPR data reveal a single ion anisotropy, D(MnIII) = −3.94 cm−1. Theoretical studies on simplified model complexes of 1 reveal that calculated values of the exchange coupling and the anisotropy are in excellent agreement with experiment, with the weak ferromagnetism resulting from an accidental orthogonality between the Mn–N–O plane of the first MnIII ion and the Jahn–Teller axis of the second MnIII ion.