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

Here, we report the molecular self-assembly of hydroxido-bridged {Ln 5 Ni 6 } ((Ln 3+ = Dy 3+ , Y 3+ ) metal clusters by the reaction of enantiopure chiral ligands, namely, ( R / S )-(2-hydroxy-3-methoxybenzyl)-serine), with Ni II and Ln III 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 {Dy 5 Ni 6 } indicates ferromagnetic coupling between Dy III and Ni II centers, whereas those on {Y 5 Ni 6 } denote that the Ni II centers are antiferromagnetically coupled and/or magnetically anisotropic. Magneto-chiral dichroism (MChD) measurements on {Dy 5 Ni 6 } and its comparison to that of {Y 5 Ni 6 } 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 II d-d transitions are mostly driven by natural optical activity and those associated with the Dy III f-f transitions are driven by magnetic optical activity.