Structures and Single-Molecule Magnet Behavior of Dy 3 and Dy 4 Clusters Constructed by Different Dysprosium(III) Salts.

Using the Schiff base ligand H 2 L-pyra ( N '-(2-hydroxybenzoyl)pyrazine-2-carbohydrazonamide) with multiple dentate sites, the trinuclear Dy III -based complex [Dy 3 (HL-pyra) 2 (L-pyra) 2 (CH 3 COO) 3 ]·2H 2 O ( 1 ) was synthesized. By analyzing the fragmented assembly process and fine-tuning the bridging anions, complex [Dy 4 (HL-pyra) 2 (L-pyra) 4 (NO 3 ) 2 (H 2 O) 2 ]·8H 2 O ( 2 ) with different nuclear numbers was successfully synthesized. Magnetic studies demonstrated that 1 did not exhibit magnetic relaxation behavior under the external field; however, 2 exhibited zero-field single-molecule magnetic relaxation behavior with an effective energy barrier ( U eff ) of 197.44 K. This is attributed to the improved anisotropy of the single ion after the normalization of the crystal structure, thus realizing the molecular magnetic switching. Moreover, magnetic dilution analysis of 2 demonstrated that the weak magnetic interaction between metal ions inhibited the occurrence of quantum tunneling of magnetization (QTM), resulting in high-performance single-molecule magnet (SMM) behavior. The reasons for the magnetic difference between these two complexes were analyzed using ab initio calculation and magneto-structural correlations. This study provides a reasonable prediction of the ideal configuration of the approximately parallelogram Dy III -based SMMs, thus offering an effective approach for synthesizing Dy 4 complexes with excellent properties.