Magneto-structural correlations in arsenic- and selenium-ligated dysprosium single-molecule magnets

• Published in: Chemical science (Cambridge) 2016-03, Vol.7 (3), p.2128-2137
• Main Authors: Pugh, Thomas, Vieru, Veacheslav, Chibotaru, Liviu F, Layfield, Richard A
• Format: Article
• Language: English
• Subjects: Arsenic; Barriers; Chemistry; Dilution; Dysprosium; Exchange; Ion exchangers; Magnetization; Magnets
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c5sc03755g

The structures and magnetic properties of the arsenic- and selenium-ligated dysprosium single-molecule magnets (SMMs) [Cp′ 3 Dy(AsH 2 Mes)] ( 3-Dy ), [(η 5 -Cp′ 2 Dy){μ-As(H)Mes}] 3 ( 4-Dy ), [Li(thf) 4 ] 2 [(η 5 -Cp′ 2 Dy) 3 (μ 3 -AsMes) 3 Li] ([Li(thf) 4 ] 2 [ 5-Dy ]), and [(η 5 -Cp′ 2 Dy){μ-SeMes}] 3 ( 6-Dy ) are described. The arsenic-ligated complexes 4-Dy and 5-Dy are the first SMMs to feature ligands with metalloid elements as the donor atoms. The arsenide-ligated complex 4-Dy and the selenolate-ligated complex 6-Dy show large anisotropy barriers in the region of 250 cm −1 in zero d.c. field, increasing to 300 cm −1 upon 5% magnetic dilution. Theoretical studies reveal that thermal relaxation in these SMMs occurs via the second-excited Kramers' doublet. In contrast, the arsinidene-ligated SMM 5-Dy gives a much smaller barrier of 23 cm −1 , increasing to 35 cm −1 upon dilution. The field-dependence of the magnetization for 4-Dy and 5-Dy at 1.8 K show unusual plateaus around 10 kOe, which is due to the dominance of arsenic-mediated exchange over the dipolar exchange. The effects of the exchange interactions are more pronounced in 5-Dy , which is a consequence of a small but significant increase in the covalent contribution to the predominantly ionic dysprosium-arsenic bonds. Whereas the magnetically non-dilute dysprosium SMMs show only very narrow magnetization versus field hysteresis loops at 1.8 K, the impact of magnetic dilution is dramatic, with butterfly-shaped loops being observed up to 5.4 K in the case of 4-Dy . Our findings suggest that ligands with heavier p-block element donor atoms have considerable potential to be developed more widely for applications in molecular magnetism. A series of arsine-, arsenide, arsinidene and selenium-ligated dysprosium single-molecule magnets (SMMs) are described. The arsenide- and selenolate-ligated SMMs show anisotropy barriers up to 300 cm −1 upon magnetic dilution.