Asymmetric Assembly of Chiral Lanthanide(III) Tetranuclear Cluster Complexes Using Achiral Mixed Ligands: Single-molecule Magnet Behavior and Magnetic Entropy Change.

It is challenging to use achiral ligands to spontaneously construct chiral molecular magnets. In this work, two new Ln 4 cluster complexes based on N , N '-(1,3-propanediyl)bis[ N -[1,1-bis(hydroxymethyl)-2-hydroxyethyl]amine] (H 6 L) have been assembled, which are crystallized in a chiral space group due to the asymmetric distribution of acetate (OAc - ) groups and hexafluoroacetylacetonate (F 6 acac - ) groups on both sides of the parallelogram-like Ln 4 core. Complex 1 , [Dy 4 (H 3 L) 2 (OAc) 3 (F 6 acac) 3 ]·5MeOH·2H 2 O, exhibits single-molecule magnet properties at the zero field with the U eff / k value of 48.4 K; notably, besides the Orbach process, the Raman process is also prominent for the magnetic relaxation of 1 . Complex 2 , [Gd 4 (H 3 L) 2 (OAc) 3 (F 6 acac) 3 ]·4MeOH·2.5H 2 O, displays a large magnetocaloric effect, whose largest -Δ S m value is 21.88 J kg -1 K -1 (when T = 2 K and Δ H = 5 T); it thus can be utilized as a good magnetic refrigeration molecular material.