Magnetic 3d-4f Chiral Clusters Showing Multimetal Site Magneto-Chiral Dichroism.

Here, we report the molecular self-assembly of hydroxido-bridged {LnNi} ((Ln = Dy, Y) metal clusters by the reaction of enantiopure chiral ligands, namely, (/)-(2-hydroxy-3-methoxybenzyl)-serine), with Ni and Ln precursors. Single-crystal diffraction analysis reveals that these compounds are isostructural sandwich-like 3d-4f heterometallic clusters showing helical chirality. Direct current magnetic measurements on {DyNi} indicates ferromagnetic coupling between Dy and Ni centers, whereas those on {YNi} denote that the Ni centers are antiferromagnetically coupled and/or magnetically anisotropic. Magneto-chiral dichroism (MChD) measurements on {DyNi} and its comparison to that of {YNi} provide the first experimental observation of intense multimetal site MChD signals in the visible-near-infrared region. Moreover, the comparison of MChD with natural and magnetic circular dichroism spectra unambiguously demonstrate for the first time that the MChD signals associated with the Ni d-d transitions are mostly driven by natural optical activity and those associated with the Dy f-f transitions are driven by magnetic optical activity.