Chiral Dysprosium Single-Molecule Magnets Displaying Circular Polarized Luminescence and Magneto-Chiral Dichroism

The combination of single-molecule magnet (SMM) behavior with chiroptical and magneto-(chiro)optical properties allows for the preparation of functional materials responsive to light and magnetic fields. Herein, we report on novel enantiopure chiral lanthanide (Ln) SMMs derived from the [Ln(bbpen)]⁺ scaffold (bbpen = N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl)ethylenediamine), formulated as [Dy(bbpen)((1S,2S)/(1R,2R)-chxn)](BPh₄) (Dy-S/R) (chxn = 1,2-diaminocyclohexane). These chiral complexes exhibit SMM behavior associated with effective energy barriers over 800 K and strong room-temperature NCD and MCD responses, as evidenced by the g_NCD and g_MCD dissymmetry factors. CPL measurements at room temperature reveal |g_lum| values of 0.23(2) for the ⁴F_9/2→⁶H_11/2 magnetic dipole-allowed transition, setting a new record value in the realm of chiral SMMs. Furthermore, variable-temperature and variable-field MChD spectroscopy measurements reveal among the strongest magneto-chiral optical responses reported so far for Dy^III chiral complexes, despite the electric-dipole induced nature of the Dy^III f-f electronic transitions. Dynamic MChD measurement at low temperature allowed us to optically trace the magnetic hysteresis cycles for both enantiomers and for different electronic transitions. Overall, this study establishes the bbpen scaffold as an ideal building block for the preparation of multifunctional materials and open great perspectives for the preparation of novel chiral materials with enhanced magneto-(chiro)optical responses by chemical design.