The molecular magnetism of 4f- and 5f-block complexes has undergone explosive development in recent years due especially to an interest in molecules comprising lanthanide and actinide cations that exhibit slow paramagnetic relaxation. The magnetic properties of such compounds depend heavily on the symmetry and strength of the ligand fields at the metal cations. In this context, tetraazaannulene (C22H22N42-) (tmtaa2-) compounds of lanthanides will be discussed to better understand the chemistry and magnetic properties of this system. The resulting [Ln(tmtaa)2]� Ln = Dy, Tb compounds have superior solubility properties and demonstrate interesting magnetic behavior, including single ion magnetism. The magnetic properties of the system can also be modulated through choice of counter ion, which produces an effective symmetry lowering at the rare earth cations. In addition to the largely electrostatic contributions to magnetic behavior for the 4f congeners, new efforts to describe axial, high valent uranium paramagnets will also be described. In particular, the small but important role of 5f metal-axial ligand covalency will be used as a starting point for elaboration of new molecular magnetic materials.

Adaptable ligand fields for exploring the molecular magnetism of the f-block elements

246th National Meeting (2013)

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