Homochiral Dy2 Schiff Base Complexes Based on (R)/(S)-Chlocyphos: Single-Molecule Magnet Behaviours, Proton Conductivities and MCD Effects

Abstract

Chiral proton conductive single-molecule magnets (SMMs) are multifunctional molecular materials that can combine conductor, magnet, and chirality at the nanoscale, but there are still significant challenges to their synthesis. Herein, the hydrazone Schiff base ligand (E)-N′-(2-hydroxybenzylidene)-3-aminopyrazine-2-carbohydrazide (H₂L_Schiff) and the homochiral ligands (R)-(+)-chlocyphos/ (S)-(−)-chlocyphos (R-HL)/(S-HL) were chosen to assemble a pair of Dy₂ enantiomers [Dy₂(R-L)₂(L_Schiff)₂(DMA)₂]·2.5H₂O (R-1) (DMA = N,N-dimethylacetamide) and [Dy₂(S-L)₂(L_Schiff)₂(DMA)₂]·2.5H₂O (S-1) at room temperature. Magnetic investigation indicated that they are field-induced SMMs, with a U_eff/k value of 42.2 K at 1000 Oe, and there is ferromagnetic coupling within the molecule; these magnetic properties may be explained by the ab initio calculations. The presence of a hydrogen bonding network confers the enantiomers proton conductivities. Moreover, R-1 and S-1 show prominent magnetic circular dichroism (MCD) effects at room temperature.