Ferromagnetic exchange in a twisted, oxime-bridged [Mn III2] dimer

Abstract

The dimeric complex [Mn III2(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 Mn III 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(Mn III) = -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 Mn III ion and the Jahn-Teller axis of the second Mn III ion. © The Royal Society of Chemistry 2012.