Supramolecular Control over Molecular Magnetic Materials: γ‑Cyclodextrin-Templated Grid of Cobalt(II) Single-Ion Magnets

Single-ion magnets (SIMs) are potential building blocks of novel quantum computing devices. Unique magnetic properties of SIMs require effective separation of magnetic ions and can be tuned by even slight changes in their coordination sphere geometry. We show that an additional level of tailorability in the design of SIMs can be achieved by organizing magnetic ions into supramolecular architectures, resulting in gaining control over magnetic ion packing. Here, γ-cyclodextrin was used to template magnetic Co^II and nonmagnetic auxiliary Li⁺ ions to form a heterometallic {Co, Li, Li}₄ ring. In the sandwich-type complex [(γ-CD)₂Co₄Li₈(H₂O)₁₂] spatially separated Co^II ions are prevented from superexchange magnetic coupling. Ac/dc magnetic and EPR studies demonstrated that individual Co^II ions with positive zero-field splitting exhibit field-induced slow magnetic relaxation consistent with the SIMs’ behavior, which is exceptional in complexes with easy-plane magnetic anisotropy.