Probing the Influence of the Ligands on the Magnetism of Dinuclear Manganese, Iron, and Chromium Complexes Supported by Aroylhydrazone

The influence of aroylhydrazone and bridging ligands on the exchange coupling constant (J) of five dinuclear metal complexes is analyzed through ab initio calculations. The complete active space second-order perturbation theory with localized orbitals offers not only estimates of J but also detailed information about the contributions of the molecular regions to the overall magnetism. This computational strategy is first validated for two previously reported ferromagnetic Mn-III/Mn-III and antiferromagnetic Fe-III/Fe-III complexes. Such calculations are extended to three new dinuclear complexes of Mn-IV, Fe-III and Cr-III constructed with a chemically simpler ligand (HL). We provide the synthesis and structural characterization (X-ray diffraction crystallography) of these three new compounds. The HL ligand exhibits little electronic influence over the J value, but it directs the magnetic properties of the compound by conditioning the relative arrangement of the metal centres.