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From a Piano Stool to a Sandwich: A Stepwise Route for Improving the Slow Magnetic Relaxation Properties of Thulium

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journal contribution
posted on 29.08.2017 by Katie L. M. Harriman, Ilia Korobkov, Muralee Murugesu
Two mononuclear TmIII complexes, [Tm­(COT)­I­(THF)2] (1-Tm) and [K­(18-crown-6)­(THF)2]­[Tm­(COT)2] (2-Tm), display slow relaxation of the magnetization, making these compounds rare examples of non-Kramers TmIII single-molecule magnets (SMMs). Utilizing a stepwise synthetic approach for the installation of cyclooctatetraenide (COT) ligands, we can observe the effect of symmetry optimization at the metal center. This method results in an 85% increase in the energy barrier to magnetization reversal (Ueff) for 2-Tm (Ueff = 53.3 K) over 1-Tm (Ueff = 7.93 K). The increased local symmetry of 2-Tm reduces the need for large static fields, eliciting SMM behavior under a small field of 200 Oe. This illustrates the power of fine-tuning the ligand environment to enhance the magnetic relaxation properties of non-Kramers ions.