Manipulating the Relaxation of Quasi-D4d Dysprosium Compounds through Alternation of the O-Donor Ligands

Three mononuclear Dy III complexes with the same auxiliary ligand Lz (2,4-diamino-6-pyridyl-1,3,5-triazine), [Dy(TTA) 3 Lz] ( 1Dy ) (TTA = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionate), [Dy(acac) 3 Lz]·CH 3 OH·0.5H 2 O ( 2Dy ) (acac = acetylacetonate), and [Dy(MQ) 2 Lz 2 ]Br·CH 3 OH ( 3Dy ) (HMQ = 2-methyl-8-quinolinol), have been synthesized through alteration of the ligands containing O donors. In all three complexes, the Dy III ions are eight-coordinate and submitted to pseudo- D 4 d symmetry in the first coordination sphere. It is noteworthy that the TTA ligands in 1Dy are easily substituted by other bidentate capping ligands with O donors, leading to distinct magnetic properties, which were studied experimentally and via ab initio calculations. All three complexes were found to exhibit single-molecule magnet behavior with U eff of 22 cm –1 ( 1Dy ), 112 cm –1 ( 2Dy ), and 56 cm –1 ( 3Dy ) under zero applied dc field. Complex 1Dy demonstrates inferior SIM properties compared with 2Dy and 3Dy, which can be attributed to the strong electron-withdrawing effects of TTA ligands, as confirmed by theoretical calculations. However, butterfly-shaped magnetic hysteresis in 1Dy and 3Dy was observed at 1.9 K, while not in 2Dy .