Enantioselective Self-Assembly of Triangular Dy-3 Clusters with SingleMolecule Magnet Behavior

Three pairs of enantiopure chiral triangular Ln(3) clusters, [Ln(3)L(RRRRRR/SSSSSS)((3)-OH)(2)(H2O)(2)(SCN)(4)]xCH(3)OHyH(2)O (R-Dy-3, Ln=Dy, x=6, y=0; S-Dy-3, Ln=Dy, x=6, y=1; R-Ho-3, Ln=Ho, x=6, y=1; S-Ho-3, Ln=Ho, x=6, y=1; R-Er-3, Ln=Er, x=6, y=0; S-Er-3, Ln=Er, x=6, y=1), have been successfully synthesized by a rational enantioselective synthetic strategy. The core of triangular Ln(3) is bound in the central N6O3 of the macrocyclic ligand, and the coordination spheres of Ln ions are completed by four SCN- anions and two H2O molecules in axial positions of the macrocycle. The circular dichroism (CD) and vibrational circular dichroism (VCD) spectra of the enantiomers demonstrate that the chirality is successfully transferred from the ligands to the resulting Ln(3) clusters. Ac susceptibility measurements reveal that single-molecule magnet behavior occurs for both enantiopure clusters of R-Dy-3 and S-Dy-3. This work is one of the few examples of the successful design of a pair of triangular Dy-3 clusters showing simultaneously slow magnetic relaxation and optical activity, and this might open up new opportunities to develop novel multifunctional materials