Homochiral Dy2Zn2 zero-field single-molecule magnets derived from (R)/(S)-2-methoxy-2-phenylacetic acids

Abstract

Despite the unique advantages of multifunctional integration at the nanoscale, chiral zero-field single-molecule magnets (SMMs), especially those based on homochiral carboxylic acids, are still difficult to obtain. Herein, homochiral (R)/(S)-2-methoxy-2-phenylacetic acids (R-HMPA)/(S-HMPA) were selected as the bridging ligands to assemble a pair of Dy₂Zn₂ enantiomers based on the Schiff base ligand (E)-2-((2-hydroxy-3-methoxybenzylidene)amino)phenol (H₂L_Schiff), [Dy₂Zn₂(S-MPA)₂(L_Schiff)₄(DMF)₂]·2DMF (S-1) (DMF = N,N-dimethylformamide) and [Dy₂Zn₂(R-MPA)₂(L_Schiff)₄(DMF)₂]·2DMF (R-1), which possess a [Dy₂Zn₂O₆] defective dicubane core. The CD spectra of R-1 and S-1 confirmed their enantiomeric nature and chiral optical activities. Magnetic studies revealed that they are good zero-field SMMs, with a relatively large U_eff/k value of 234.6 K at 0 Oe and an obvious hysteresis loop at 3.0 K; notably, these magnetic properties could be explained using ab initio calculations.