Magneto-Chiral Dichroism of a chiral Prussian Blue Analog
[MnII(X–pnH)(H2O)][CrIII (CN)6]·H2O (X = S, R; pn = 1,2-propanediamine) is a 2D chiral molecular ferrimagnet with a Curie temperature of 38 K first synthesized in Prof. Inoue’s group in Hiroshima, Japan. Single crystals suitable for magneto-optical measurements were grown by M. Atzori starting from enantiopure chiral ligands. Absorption and Magneto-Chiral Dichroism (MChD) spectra of these single-crystals were measured by M. Atzori in the visible range on a dedicated set-up renewed in the lab by I. Brestlavetz and K. Paillot. At 4 K the electronic spectrum becomes very rich, featuring spin-allowed and spin-forbidden transitions of CrIII centers, spin-forbidden transitions of the MnII centers and metal-to-metal charge transfer bands. It appears that the most intense MChD signal is associated to the Mn(II) absorber which is the closest from the chiral source. Moreover, it was shown that the MChD signal abruptly increases below the Curie temperature of the material. Pushing the observation of MChD in an ordered magnet from 6 K to 38 K is an important step towards the use of MChD for the optical detection of magnetization using unpolarized light. More details here: J. Am. Chem. Soc. 141, 20022 (2019).