Counterion-Assisted Assembled Robust π–π Interaction-Stacked Organic Frameworks of Dysprosium Single-Ion Magnets

Dysprosium-based single-ion magnets (Dy-SIMs) are regarded as an ideal kind of molecular-based magnetic materials owing to their outstanding magnetic performance. However, most of them suffer from poor stability. Improving their stability has become an urgent task in this field. To this end, we propose a novel strategy that involves assembling Dy-SIM-based π–π interactions-stacked organic frameworks (πOFs) with the assistance of π-conjugated counterions. Two Dy-SIM-based πOFs, [Hacd]3[Dy(ana)2(NO3)2(H2O)2]2(NO3) (πOF-1) and [Hacd][Dy(ana)4(CH3OH)2] (πOF-2) have been synthesized successfully ([Hacd]+ = acridine cation, ana– = anthracene-9-carboxylate anion). As expected, the introduced [Hacd]+ counterions are sandwiched between adjacent Dy-SIM anions to form sandwich-like π–π stacking structures, which assemble the Dy-SIM anions into desired πOFs. To our knowledge, this is the first time that π-conjugated counterions have been used synergistically to construct Dy-SIM based πOFs. Both πOFs exhibit good air, thermal, and solvent stability. Compared to πOF-1, πOF-2 exhibits structural stability across a wider range of organic solvents and solutions. Both πOFs exhibit dual magnetic relaxation behaviors. Theoretical calculations suggest that they are associated with the DyIII···DyIII interactions mediated by π–π interactions. The effective energy barriers (Ueff) for the slow relaxation process of πOF-1 and πOF-2 are 50.5 and 48.4 K, respectively. This work provides a new approach to developing high-stability Dy-SIM systems by utilizing π-conjugated counterions to assist the assembly of πOF structures.