Slow Magnetic Relaxation in Mono‐ and Bimetallic Lanthanide Tetraimido‐Sulfate S(NtBu)₄²⁻ Complexes

Abstract

Lanthanide ions are particularly well-suited for the design of single-molecule magnets owing to their large unquenched orbital angular momentum and strong spin-orbit coupling that gives rise to high magnetic anisotropy. Such nanoscopic bar magnets can potentially revolutionize highdensity information storage and processing technologies, if blocking temperatures can be increased substantially. Exploring non-classical ligand scaffolds with the aim to boost the barriers to spin-relaxation are prerequisite. Here, the syn-thesis, crystallographic and magnetic characterization of a series of each isomorphous mono-and dinuclear lanthanide (Ln = Gd, Tb, Dy, Ho, Er) complexes comprising tetraimido sulfate ligands are presented. The dinuclear Dy complex [{(thf) 2 Li(NtBu) 2 S(tBuN) 2 DyCl 2 } 2 • ClLi(thf) 2 ] (1c) shows true signatures of single-molecule magnet behavior in the absence of a dc field. In addition, the mononuclear Dy and Tb complexes [{(thf) 2 Li(NtBu) 2 S(tBuN) 2 LnCl 2 (thf) 2 ] (2b,c) show slow magnetic relaxation under applied dc fields.

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

“…1 H NMR (500 MHz, benzene-d 6 , ppm) δ: 2.38 (m, 4H, CH 2 ), 2.13 (s, 12H, N(CH 3 ) 2 ), 1.45 (s, 27H, NC(CH 3 ) 3 )), 1.16 (s, 18H, NC(CH 3 ) 3 ), 1.08 (s, 9H, NHC(CH 3 ) 3 ). 13 C NMR (125 MHz, benzene-d 6 , ppm) δ: 57.56 (2 C, CH 2 ), 52.77 (2 C, NC(CH 3 ) 3 ), 52.33 (3 C, NC(CH 3 ) 3 ), 45.26 (4 C, N(CH 3 ) 2 ), 51.20 (1 C, NHC(CH 3 ) 3 ), 34.74 (9 C, NC(CH 3 ) 3 ), 33.79 (6 C, NC(CH 3 ) 3 ), 30.90 (3 C, NHC(CH 3 ) 3 ). 15 N-HMBC NMR (40 MHz, benzene-d 6 , ppm) δ: À 227.65 (tmeda), À 230.84 (-NHC(CH 3 ) 3 ), À 235.37 (À NC(CH 3 ) 3 ), À 240.31 (NC(CH 3 ) 3 , 18 H), Anal.…”

“…1 H NMR (500 MHz, thf-d 8 , ppm) δ: 63.97 (br, 36H, NC(CH 3 ) 3 ), 27.24 (br, 1H, NHCH 3 ), 2.51 (s, 4H, CH 2 ), 2.35 (s, 12H, N(CH 3 ) 2 ), À 7.06 (br, 18H, -NC(CH 3 ) 3 ). 13 [ClDy{Na(thf)} 2 {(NtBu) 3 S} 2 ] (6): To 2 in thf (100 mg, 91.5 μmol, 1.0 eq.) DyCl 3 (25 mg, 91.5 μmol, 1.0 eq.)…”

“…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.…”

“…[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. [13,16,18] The tetraimido sulfate ligand family also represents a platform to investigate d-metal exchange coupling, which was applied for Co II and Mn II . [15] Sulfur offers great flexibility in the complex geometry while the harder nitrogen atoms ensure an optimal coordination mode around the metal center, resulting in a great synergy.…”