Strong NIR-II Magneto-Optical Activity of a Chiral SmCu Cage.

The magneto-optical response of chiral materials holds significant potential for applications in physics, chemistry, and biology. However, exploration of the near-infrared (NIR) magneto-optical response remains limited. Herein, we report the synthesis and strong NIR-II magneto-optical activity of three pairs of chiral 34 clusters of (Ln = Sm, Gd, and Dy). Structural analysis reveals that features a triangular prism cage with symmetry. Interestingly, magnetic circular dichroism (MCD) spectra exhibit remarkable magneto-optical response in the NIR-II region, driven by the transition. The maximum -factor of reaches 5.5 × 10 T around 1300-1450 nm, surpassing values associated with Dy and Cu ions. This remarkable NIR-II magneto-optical activity may be attributed to strong magnetic-dipole-allowed transitions and helix chirality of the structure. This work not only presents the largest Ln-Cu clusters to date but also demonstrate the key role of magnetic-dipole-allowed transitions on magneto-optical activity.