Magneto‐Chiral Dichroism of Chiral Lanthanide Complexes in the Context of Richardson's Theory of Optical Activity

Here we report on the Magneto-Chiral Dichroism (MChD) detected through visible and near-infrared light absorption of two enantiomeric pairs of ErIII and TmIII chiral complexes featuring a propeller-like molecular structure. The magnetic properties show typical features of isolated paramagnetic ions associated with 4I15/2 and 3H6 ground state terms. MChD spectroscopy shows high gMChD dissymmetry factors of ca. 0.12 T−1 and 0.05 T−1 (T=4.0 K and B=1.0 T) for ErIII and TmIII, respectively, associated with the magnetic-dipole allowed 4I13/2 ← 4I15/2 and 3H5 ← 3H6 transitions. MChD signals of the two complexes were detected up to room temperature and under magnetic fields up to 5.0 T. For the first time, the MChD results are discussed in the context of the Richardson theory of lanthanide optical activity and provide clear indications on the strongest MChD-active electronic transitions of lanthanide complexes.