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] (H6L) 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(H3L)(2)(OAc)(3)(F(6)acac)(3)]center dot 5MeOH center dot 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(H3L)(2)(OAc)(3)(F(6)acac)(3)]center dot 4MeOH center dot 2.5H(2)O, displays a large magnetocaloric effect, whose largest -Delta S-m value is 21.88 J kg(-1) K-1 (when T = 2 K and Delta H = 5 T); it thus can be utilized as a good magnetic refrigeration molecular material.