Fine-Tuning of the Coordination Environment To Regulate the Magnetic Behavior in Solvent/Anion-Dependent Dy^III Compounds: Synthesis, Structure, Magnetism, and Ab Initio Calculations

Abstract

It is crucial to understand and elucidate the self-assembly mechanism in solution systems for the construction of Dy^III-based single-molecule magnets (SMMs). Herein, through fine-tuning of the anion and solvent, we prepared three nine-coordinate mononuclear dysprosium compounds, [Dy(2,3'-pcad)(NO₃)₂(CH₃OH)₂] (1), [Dy(2,3'-Hpcad)₂(H₂O)₃]·3Cl·5H₂O (2), and [Dy(2,3'-pcad)(NO₃)(H₂O)₄]·NO₃·H₂O (3) [2,3'-Hpcad = N³-(2-pyridoyl)-3-pyridinecarboxamidrazone]. The reactions of formation for 1-3 are in situ thermodynamically monitored by isothermal titration calorimetry. Magnetic data analysis reveals that 2 shows SMM behavior under a zero direct-current (dc) field, whereas 1 and 3 exhibit distinct slow magnetic relaxation processes upon a 1200 Oe dc field. To deeply understand the different magnetic behaviors, the magnetic anisotropy of 1-3 has been systematically studied by ab initio calculations, which is consistent with the experimental observations. Moreover, the semiconductor behaviors of 1-3 have been investigated by experimental measurements of UV-vis spectroscopy.