Anisotropic Magneto‐Chiral Dichroism in Lanthanide Complexes

In this work, we report the preparation of a chiral Er(III) complex specifically designed to assess the influence of the magnetic anisotropy axes orientation on its magneto-chiral dichroism (MChD). High resolution MChD measurements performed along the three principal crystallographic axes revealed pronounced anisotropic effects on both MChD signal line shapes and intensities. By combining, for the first time, angle-resolved torque magnetometry, comprehensive magneto-optical spectroscopy on oriented single crystals, absorption measurements under magnetic fields up to 30 T and theoretical calculations, we provide clear experimental insight into the anisotropic nature of the MChD in lanthanide complexes. Specifically, we evaluate the extent to which Er moderate anisotropy enables signal persistence across a wide range of crystallographic orientations. These results allow the identification of the key role played by both the orientation and the magnitude of magnetic anisotropy in the MChD response of chiral lanthanide complexes, representing a significant step toward the directional control of magneto-chiroptical responses in lanthanide-based molecular materials.