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 CoII 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
CoII ions are prevented from superexchange magnetic coupling.
Ac/dc magnetic and EPR studies demonstrated that individual CoII 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.