Axial dysprosium cyclopentadienyl-amide single-molecule magnets with hysteresis up to 92 kelvin | ChemRxiv

Molecules showing magnetic memory effects at high temperatures could be used in high-density data storage devices. A magnetic hysteresis temperature (TH) of 100 K has been achieved for a near-linear d...

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Synthesis and Characterization of Monomeric, Dimeric, and Polymeric Rare-Earth Bis(trimethyl)silylphosphide Complexes

Rare-earth (RE) bis(trimethylsilyl)amide ({N(SiMe3)2}−, N″) chemistry is well-developed, whereas RE bis(trimethylsilyl)phosphide {P(SiMe3)2}− (P″) chemistry is immature. Here, we report a convenient protonolysis route to dimeric RE P″ complexes [RE(P″)2(μ-P″)]2 (1-RE; RE = Y, Gd, Dy, Er) from parent [RE(CH2C6H4-o-NMe2)3] and excess HP″. The reactions of 1-RE with THF gave the monomeric RE P″ complexes [RE(P″)3(THF)2] (2-RE; RE = Y, Gd, Dy, Er), and treatment of 1-RE with 2 eq. of KP″ gave the RE “ate” coordination polymers [RE(P″)2(μ-P″)2K]∞ (3-RE; Y, Gd, Dy, Er). Complexes 1-RE, 2-RE, and 3-RE were characterized by single-crystal XRD, elemental analysis, and NMR, ATR-IR, and UV–vis–NIR spectroscopy. All paramagnetic 1-RE and 2-RE were also characterized by EPR spectroscopy and SQUID magnetometry, supported by ab initio calculations. We find that weak magnetic exchange interactions persist between RE centers in dimeric 1-RE and that their principal magnetic axes are oriented between the phosphide ligands as a consequence of the diffuse crystal field (CF) associated with the long RE–P bonds. For monomeric 2-RE, the principal magnetic axes are also oriented between ligands, reflecting competition between three long RE–P bonds and two short RE–O bonds that contribute approximately equally to the crystal field anisotropy.

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Magnetic Hysteresis up to 73 K in a Dysprosium Cyclopentadienyl-Amide Single-Molecule Magnet

Single-molecule magnets (SMMs) based on dysprosocenium cations, [Dy(CpR)2]+ (CpR = substituted cyclopentadienyl), have set record effective energy barriers to magnetic reversal (Ueff) and temperatures...

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Bis(trimethylsilyl)phosphide chemistry: a half-century of advances across the periodic table

Whilst bis(trimethylsilyl)amide has been used extensively as a ligand across the periodic table, the chemistry of its heavier group 15 congeners is relatively underdeveloped. However, bis(trimethylsil...

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31P NMR Chemical Shift Anisotropy in Paramagnetic Lanthanide Phosphide Complexes

Lanthanide (Ln) magnetic resonance imaging and chiral shift reagents generally exploit 1H NMR shifts, as paramagnetic broadening tends to preclude the use of heavier, less sensitive nuclei. Here, we report the solution and solid-state 31P NMR shifts of an isostructural series of distorted trigonal bipyramidal Ln(III) tris-silylphosphide complexes, [Ln{P(SiMe3)2}3(THF)2] (1-Ln; Ln = La, Ce, Pr, Nd, Sm); 1-Ln was also characterized by elemental analysis; single-crystal and powder X-ray diffraction; multinuclear NMR, EPR, ATR-IR, and UV–vis-NIR spectroscopy; and SQUID magnetometry. Breaking assumptions, we observed paramagnetically broadened 31P NMR spectra for the Ln-bound P atoms for the 1-Ln family; in solution, 1-Nd showed the most downfield chemical shift (δ{31P} = 2570.14 ppm) and 1-Sm the most upfield value (δ{31P} = −259.21 ppm). We determined the span of the chemical shift anisotropies (CSAs) for solid 1-Ln using magic angle spinning NMR spectroscopy; the CSA was largest for 1-Pr (Ω{31P} ≈ 2000 ppm), consistent with a combination of paramagnetism and the relatively large differences in pyramidalization of the three P atoms in the solid-state. Density functional theory calculations for 1-La were in excellent agreement with the experimentally determined 31P NMR parameters. We find good agreement of experimental 1H NMR chemical shifts with ab initio-calculated values for paramagnetic 1-Ln, while the shifts of heavier 13C, 29Si, and 31P nuclei are not well-reproduced due to the current limitations of paramagnetic NMR calculations for nuclei with large contact shifts.

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