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

It is crucial to understand and elucidate the self-assembly mechanism in solution systems for the construction of DyIII-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.