Metallacrowns are large polymetallic complexes, making them promising candidates as single-molecule magnets (SMMs). SMMs have easy-axis anisotropy and an energy barrier between the two directions of magnetization. The goal of SMM research is to maximize this energy barrier so that SMMs can be used in magnetic data storage. Mixed 3d-4f SMMs are complicated by the large spin-orbit coupling of 4f ions. To understand how the 3d ion spin couples with the large anisotropy of the 4f lanthanide ions, we synthesized a series of 3d-4f metallacrowns with the formula Ln2M4(shi3-)4(Hshi2-)2(H2shi-)2 (H3shi = Salicylhydroxamic acid, Ln = Dy3+, Tb3+, Gd3+, Er3+, M = Fe3+, Ga3+). The lanthanides have been varied to test whether the ligand field supports SMM behavior for oblate (Dy3+, Tb3+) or prolate (Er3+) lanthanides. The Fe3+ analogues provide extra spin, whereas the Ga3+ analogues provide no additional spin. We found that only the Dy2Ga4 and Dy2Fe4 materials display SMM behavior. The Dy2Ga4 compound has an energy barrier of 22.2 K, whereas the Dy2Fe4 does not have a blocking temperature above 2 K. We can conclude that there is an axial geometry supporting SMM behavior for oblate lanthanides (Dy3+), and that residual spin from the outer Fe3+ ions has a negative effect on the energy barrier. The aim of this project is to understand the magnetic interactions in 3d-4f ions in order to develop design strategies for higher performing SMMs. Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/239nm/uploads/12192_thiol_paper_star.jpg' alt='' />

Systematic study of 3d-4f metallacrowns for use as single-molecule magnets (SMMs)

246th National Meeting (2013)

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