Magneto-optical Properties of Chiral Co 2 Ln and Co 3 Ln 2 (Ln = Dy and Er) Clusters.

A series of chiral heterometallic Ln-Co clusters, denoted as Co 2 Ln and Co 3 Ln 2 (Ln = Dy and Er), were synthesized by reacting the chiral chelating ligand ( R / S )-2-(1-hydroxyethyl)pyridine (Hmpm), CoAc 2 ·4H 2 O, and Ln(NO 3 ) 3 ·6H 2 O. Co 2 Ln and Co 3 Ln 2 exhibit perfect mirror images in circular dichroism within the 320-700 nm range. Notably, the Co 2 Er and Co 3 Er 2 clusters display pronounced magnetic circular dichroism (MCD) responses of the hypersensitive f-f transitions 4 I 15/2 - 4 G 11/2 at 375 nm and 4 I 15/2 - 2 H 11/2 at 520 nm of Er III ions. This study highlights the strong magneto-optical activity associated with hypersensitive f-f transitions in chiral 3d-4f magnetic clusters.