Accidentally on purpose: construction of a ferromagnetic, oxime-based [Mn-2(III)] dimer

The serendipitous self-assembly of the complex [(Mn2Zn2II)-Zn-III(Ph-sao)(2)(Ph-saoH)(4)(hmp)(2)] (1), whose magnetic core consists solely of two symmetry equivalent Mn(III) ions linked by two symmetry equivalent -N-O-moieties, provides a relatively simple model complex with which to study the magneto-structural relationship in oxime-bridged Mn(III) cluster compounds. Dc magnetic susceptibility measurements reveal ferromagnetic (J = +2.2 cm(-1)) exchange resulting in an S = 4 ground state. Magnetisation measurements performed at low temperatures and high fields reveal the presence of significant anisotropy, with ac measurements confirming slow relaxation of the magnetisation and Single-Molecule Magnetism behaviour. Simulations of high field, high frequency EPR data reveal a single ion anisotropy, D-(MnIII) = -3.83 cm(-1). DFT studies on a simplified model complex of 1 reveal a pronounced dependence of the exchange coupling on the relative twisting of the oxime moiety with respect to the metal ion positions, as suggested previously in more complicated [Mn-3(III)] and [Mn-6(III)] clusters.