Magneto-Optical Readout of a Chiral Single-Molecule Magnet at Telecom Wavelengths

In this work, the wavelength range of magneto-chiral dichroism (MChD) based optical readout of magnetic hysteresis is extended to the near-infrared (NIR) telecom communication range where optical fibers have the smallest transmission loss. To achieve this goal, we have prepared and investigated a new air-stable chiral single-molecule magnet (SMM) formulated as (<i>S</i>)- and (<i>R</i>)-[Dy(bbppn)Cl] (bbppn = <i>N,N'</i>-bis(2-hydroxybenzyl)-<i>N,N'</i>-bis(2-pyridylmethyl)-<i>X</i>-1,2-propanediamine, <i>X</i> = <i>S</i>, <i>R</i>). We demonstrate that the magnetic hysteresis of this SMM, despite exhibiting rapid quantum tunneling of magnetization (QTM) at zero field, can be optically detected using unpolarized light through MChD. Complementary to our seminal study limited to the visible spectral range, we demonstrate that the MChD-based readout is also effective for the Dy(III) <i>f</i>-<i>f</i> transitions in the NIR region, confirming the robustness of this method across a broader spectral window. These findings establish MChD as a generalizable optical readout method for molecular magnetic materials, reinforcing its potential for future applications in polarization-free optical data readout technologies and optical communication at telecom wavelengths.