Magnetic Improvement and Relaxation Mechanism of the Tb-Phthalocyanine Single-Molecule Magnet by Absorbing CH₂Cl₂ Molecules

The molecular characteristics, stacking structure, and magnetic properties of Tb-phthalocyanine (TbPc 2 ) with and without the absorption of CH 2 Cl 2 molecules were systematically investigated. The first-principles calculations based on density functional theory were performed to analyze the crystal structures. The absorption of CH 2 Cl 2 can influence the crystal structure and magnetic behavior of TbPc 2 . TbPc 2 ·CH 2 Cl 2 crystallizes in orthorhombic space group Pnma, while TbPc 2 crystallizes in orthorhombic group P 2 1 2 1 2 1 . Unexpectedly, the absorption of CH 2 Cl 2 significantly varies the single-molecule magnet (SMM) properties of TbPc 2 . The hysteresis loops of TbPc 2 ·CH 2 Cl 2 exhibit obvious butterfly-shaped hysteresis loops up to 10 K, while TbPc 2 shows almost no opening even at 2 K. A much stronger antiferromagnetic interaction between the Tb ions can be observed in TbPc 2 ·CH 2 Cl 2, which is analyzed by the Curie–Weiss law using direct current susceptibility measurements. The alternating current susceptibility measurements demonstrated that the absorption of CH 2 Cl 2 can improve the U eff of TbPc 2 from 740 to 790 K. This study means that the molecular environment and stacking structure would tune the SMM behavior in mononuclear lanthanide-based SMMs.