Modulating magnetic dynamics of three Dy2 complexes through keto-enol tautomerism of the o-vanillin picolinoylhydrazone ligand.

Complexation of dysprosium(III) with the heterodonor chelating ligand o-vanillin picolinoylhydrazone (H(2)ovph) in the presence of different bases affords three new dinuclear dysprosium(III) coordination compounds, namely, [Dy(2)(ovph)(2)(NO(3))(2)(H(2)O)(2)]·2H(2)O (1), [Dy(2)(Hovph)(ovph)(NO(3))(2)(H(2)O)(4)]·NO(3)·2CH(3)OH·3H(2)O (2), and Na[Dy(2)(Hovph)(2)(μ(2)-OH)(OH)(H(2)O)(5)]·3Cl·3H(2)O (3), where the aroylhydrazone ligand adopts different coordination modes in respective structures depending on the reaction conditions, as revealed by single-crystal X-ray analyses to be due to their tautomeric maneuver. The magnetic properties of 1-3 are drastically distinct. Compounds 1 and 2 show single-molecule-magnet behavior, while no out-of-phase alternating-current signal is noticed for 3. The structural differences induced by the different coordinate fashions of the ligand may influence the strength of the local crystal field, the magnetic interactions between metal centers, and the local tensor of anisotropy on each Dy site and their relative orientations, therefore generating dissimilar dynamic magnetic behavior.