Projekt E

A key requirement for molecules to behave as single-molecule magnets (SMMs) is the presence of magnetic anisotropy, characterized by a negative axial zero-field splitting (ZFS) parameter D, which creates an energy barrier inhibiting reversal of the magnetisation. Since SMM properties are extremely sensitive to changes in structure and bonding, they provide ideal data for the critical analysis of dynamic and static electron correlation effects. The focus of this study will be on (mostly low-coordinate) 3d SMMs with targeted variations in geometry, metal-ligand covalency, etc., translating into tunable variations of the magnetic anisotropy. Ligands will be synthesized to conformationally restrict the complex and lead to enforced coordination modes, such as macrocyclic systems with two N-heterocyclic carbene units. These will be studied by SQUID magnetometry and by a bouquet of spectroscopic methods, including high-field EPR and Mössbauer spectroscopy (where applicable); the latter also provides information about internal magnetic fields.