Enhancing Steric Hindrance via Ligand Design in Dysprosium Complexes: From Induced Slow Relaxation to Zero-Field Single-Molecule Magnet Properties

Abstract

The synthesis and magnetic characterization of three novel Dy compounds, [Dy{PPh 2 S((2), and [Dy{MeS(N t Bu) 3 } 2 (μ-Cl 2 )Li(THF) 2 ] (3), based on the sulfur−nitrogen ligands RS(N t Bu) x − (where R = PPh 2 , x = 2 for (1); R = Ph, x = 2 for (2); and R = Me, x = 3 for (3)) are reported. They represent rare examples of lanthanide-based complexes containing sulfur−nitrogen ligands, whose suitability to enhance the magnetic anisotropy in 3d metals was only recently established. Changes in the ligand field environment drastically affect the magnetic properties, with compounds 1 and 2 displaying field-induced singlemolecule magnet (SMM) behavior, while compound 3 shows slow relaxation at zero field. These trends strongly suggest that ligand engineering strategies toward linear dysprosium complexes, similar to those for dysprosocenium complexes, should enhance the SMM performances of SN-based lanthanide compounds.

Alkali Metal Based Triimidosulfite Cages as Versatile Precursors for Single‐Molecule Magnets

“…Lanthanide complexes are easily accessible through metathesis reactions and for that purpose, lithium precursors are convenient to use. However, our recent work showed that the successful optimization of the magnetic properties is limited by LiHal co‐complexation [13–15,17] …”

“…The SN ligands,[ 24 , 25 ] however, have recently shown their potential for SMM design for the following reasons (Scheme 1 ):[ 12 , 13 , 14 , 15 , 16 , 17 , 18 ] First, acute bite angles of the SN motif provide access to interesting and promising geometries. [ 12 , 14 ] Further, tuning the SN ligands served as model systems to find the ideal bite angles for tetrahedral Co II SMMs and allowed an increase of linearity in f‐metal SMMs.…”

“…However, our recent work showed that the successful optimization of the magnetic properties is limited by LiHal co‐complexation. [ 13 , 14 , 15 , 17 ]…”

“…However, our recent work showed that the successful optimization of the magnetic properties is limited by LiHal cocomplexation. [13][14][15]17] Consequently, we exchanged lithium with the heavier homologs potassium (1) and sodium (2,3) to prevent additional LiHal-co-complexation during metathesis reactions. [30] The resulting Dy III -complexes exhibit SMM properties and were characterized by X-ray diffraction and magnetic experiments.…”

“…[22] This breakthrough resulted in the design of many similar SMMs, partially neglecting other alternatives and ligand systems, such as p-block donating ligands or SN ligands. [23] The SN ligands, [24,25] however, have recently shown their potential for SMM design for the following reasons (Scheme 1): [12][13][14][15][16][17][18] First, acute bite angles of the SN motif provide access to interesting and promising geometries. [12,14] Further, tuning the SN ligands served as model systems to find the ideal bite angles for tetrahedral Co II SMMs and allowed an increase of linearity in f-metal SMMs.…”