Two Pairs of Homochiral Parallelogram-like Dy₄ Cluster Complexes with Strong Magneto-Optical Properties

Two pairs of homochiral Dy(III) tetranuclear cluster complexes derived from (+)/(-)-3-trifluoroacetyl camphor (D-Htfc/L-Htfc), [Dy-4(OH)(2)(L1)(4)(D-tfc)(2)(DMF)(2)]4DMF (D-1) [H(2)L1 = (E)-2-(2-hydroxy-3-methoxybenzylideneamino)phenol)]/[Dy-4(OH)(2)(L1)(4)(L-tfc)(2)(DMF)(2)]4DMF (L-1) and [Dy-4(OH)(2)(L2)(4)(D-tfc)(2)(DMF)(2)]2H(2)O3MeCN (D-2) [H(2)L2 = (E)-3-(2-hydroxy-3-methoxybenzylideneamino)naphthalen-2-ol]/[Dy-4(OH)(2)(L2)(4)(L-tfc)(2)(DMF)(2)]2H(2)O3MeCN (L-2), were synthesized at room temperature, which have a Dy-4 parallelogram-like core. The magnetic studies revealed that D-1 exhibits single-molecule magnet (SMM) behavior under zero dc magnetic field, and its magnetic relaxation has a distinct Raman process in addition to the Orbach process, with the U-eff/k value of 57.5 K and the C value of 28.27 s(-1)K(-2.14); while D-2 displays dual magnetic relaxation behavior at 0 Oe field, with the U-eff/k value 114.8 K for the slow relaxation process (SR) and the C value of 10.656 s(-1)K(-5.80) for the fast relaxation process (FR), respectively. Theoretical calculations indicated that the conjugated groups (phenyl vs naphthyl) of the Schiff base bridging ligands (H(2)L1 and H(2)L2) significantly affect the intramolecular magnetic interactions between the Dy3+ ions and ultimately lead to different relaxations. Furthermore, magnetic circular dichroism (MCD) measurements showed that these two pairs of Dy-4 enantiomers exhibit strong room temperature magneto-optical Faraday effects; notably, increasing the conjugated group on the Schiff base bridging ligand is beneficial to enhancing the magneto-optical Faraday effects.