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1. Switching on single-molecule magnet properties of homoleptic sandwich tris(pyrazolyl)borate dysprosium( iii ) cations via intermolecular dipolar coupling

   https://doi.org/10.1039/c9dt00597h  

   Alexandropoulos, Dimitris I.; Vignesh, Kuduva R.; Xie, Haomiao; Dunbar, Kim R. (July 2019, Dalton Transactions)

   Two new homoleptic Dy III compounds [Dy(Tp Me2 ) 2 ][DyCl 3 (Tp Me2 )]·CH 2 Cl 2 ( 1 ) and [Dy(Tp Me2 ) 2 ]I ( 3 ) as well as a heteroleptic (NMe 4 )[DyCl 3 (Tp Me2 )] ( 2 ) (Tp Me2 = tris(3,5-dimethylpyrazolyl)borate) species are reported. Magnetic studies revealed that 1 is a single-molecule magnet (SMM) with an energy barrier of U eff = 80.7 K with τ 0 = 6.2 × 10 −7 s under a zero applied field. Compound 3 exhibits a U eff of 13.5 K with τ 0 = 1.6 × 10 −6 s under a 0.08 T applied field. Ab initio CASSCF + RASSI-SO calculations were performed to further investigate the magnetic behavior of complexes 1–3 . The results support experimental magnetic data for 1 and 3 and indicate that an intermolecular dipolar interaction of ( zJ = −0.1 cm −1 ) is responsible for the SMM behavior of 1 . 

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2. Six-coordinate mononuclear dysprosium( iii ) single-molecule magnets with the triphenylphosphine oxide ligand

   https://doi.org/10.1039/d0dt00801j  

   Vignesh, Kuduva R.; Alexandropoulos, Dimitris I.; Xie, Haomiao; Dunbar, Kim R. (April 2020, Dalton Transactions)

   Structural, magnetic and theoretical studies of three octahedral mononuclear Dy III complexes with triphenylphosphine oxide and halide ligands are reported. The Cl − and Br − analogues exhibit SMM behavior with energy barriers of 49.1 K and 70.9 K, respectively under a small dc field. Ab initio calculations were performed, the results of which predict higher energy barriers for iodide containing SMMs. 

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3. Relaxation dynamics in see-saw shaped Dy( iii ) single-molecule magnets

   https://doi.org/10.1039/D0QI01007C  

   Harriman, Katie L.; Murillo, Jesse; Suturina, Elizaveta A.; Fortier, Skye; Murugesu, Muralee (December 2020, Inorganic Chemistry Frontiers)

   null (Ed.)

   Utilizing a terphenyl bisanilide ligand, two Dy( iii ) compounds [K(DME) n ][L Ar Dy(X) 2 ] (L Ar = {C 6 H 4 [(2,6- i PrC 6 H 3 )NC 6 H 4 ] 2 } 2− ), X = Cl ( 1 ) and X = I ( 2 ) were synthesized. The ligand imposes an unusual see-saw shaped molecular geometry leading to a coordinatively unsaturated metal complex with near-linear N–Dy–N (avg. 159.9° for 1 and avg. 160.4° for 2 ) angles. These compounds exhibit single-molecule magnet (SMM) behavior with significant uniaxial magnetic anisotropy as a result of the transverse coordination of the bisanilide ligand which yields high energy barriers to magnetic spin reversal of U eff = 1334 K/927 cm −1 ( 1 ) and 1278 K/888 cm −1 ( 2 ) in zero field. Ab initio calculations reveal that the dominant crystal field of the bisanilide ligand controls the orientation of the main magnetic axis which runs nearly parallel to the N–Dy–N bonds, despite the identity of the halide ligand. Analysis of the relaxation dynamics reveals a ca. 14-fold decrease in the rate of quantum tunneling of the magnetisation when X = I ( 2 ). Most notably, the relaxation times were on average 5.6× longer at zero field when the heavier group 17 congener was employed. However, no direct evidence of a heavy atom effect on the Orbach relaxation was obtained as the height of the barrier is defined by the dominant bisanilide ligand. 

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4. High-temperature magnetic blocking and magneto-structural correlations in a series of dysprosium( iii ) metallocenium single-molecule magnets

   https://doi.org/10.1039/c8sc03907k  

   Randall McClain, K.; Gould, Colin A.; Chakarawet, Khetpakorn; Teat, Simon J.; Groshens, Thomas J.; Long, Jeffrey R.; Harvey, Benjamin G. (November 2018, Chemical Science)

   A series of dysprosium( iii ) metallocenium salts, [Dy(Cp iPr4R ) 2 ][B(C 6 F 5 ) 4 ] (R = H ( 1 ), Me ( 2 ), Et ( 3 ), iPr ( 4 )), was synthesized by reaction of DyI 3 with the corresponding known NaCp iPr4R (R = H, iPr) and novel NaCp iPr4R (R = Me, Et) salts at high temperature, followed by iodide abstraction with [H(SiEt 3 ) 2 ][B(C 6 F 5 ) 4 ]. Variation of the substituents in this series results in substantial changes in molecular structure, with more sterically-encumbering cyclopentadienyl ligands promoting longer Dy–C distances and larger Cp–Dy–Cp angles. Dc and ac magnetic susceptibility data reveal that these structural changes have a considerable impact on the magnetic relaxation behavior and operating temperature of each compound. In particular, the magnetic relaxation barrier increases as the Dy–C distance decreases and the Cp–Dy–Cp angle increases. An overall 45 K increase in the magnetic blocking temperature is observed across the series, with compounds 2–4 exhibiting the highest 100 s blocking temperatures yet reported for a single-molecule magnet. Compound 2 possesses the highest operating temperature of the series with a 100 s blocking temperature of 62 K. Concomitant increases in the effective relaxation barrier and the maximum magnetic hysteresis temperature are observed, with 2 displaying a barrier of 1468 cm −1 and open magnetic hysteresis as high as 72 K at a sweep rate of 3.1 mT s −1 . Magneto-structural correlations are discussed with the goal of guiding the synthesis of future high operating temperature Dy III metallocenium single-molecule magnets. 

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5. Luminescence of Lanthanide Complexes with Perfluorinated Alkoxide Ligands

   https://doi.org/10.1021/acs.inorgchem.0c00782  

   Kotyk, Christopher M.; Weber, Jeremy E.; Hyre, Ariel S.; McNeely, James; Monteiro, Jorge H.; Domin, Marek; Balaich, Gary J.; Rheingold, Arnold L.; de Bettencourt-Dias, Ana; Doerrer, Linda H. (July 2020, Inorganic Chemistry)

   Four groups of rare-earth complexes, comprising 11 new compounds, with fluorinated O-donor ligands ([K(THF)6][Ln(OC4F9)4(THF)2] (1-Ln; Ln = Ce, Nd), [K](THF)x[Ln(OC4F9)4(THF)y] (2-Ln; Ln = Eu, Gd, Dy), [K(THF)2][Ln(pinF)2(THF)3] (3-Ln; Ln = Ce, Nd), and [K(THF)2][Ln(pinF)2(THF)2] (4-Ln; Ln = Eu, Gd, Dy, Y) have been synthesized and characterized. Single-crystal X-ray diffraction data were collected for all compounds except 2-Ln. Species 1-Ln, 3-Ln, and 4-Ln are uncommon examples of six-coordinate (Eu, Gd, Dy, and Y) and seven-coordinate (Ce and Nd) LnIII centers in all-O-donor environments. Species 1-Ln, 2-Ln, 3-Ln, and 4-Ln are all luminescent (except where Ln = Gd and Y), with the solid-state emission of 1-Ce being exceptionally blue-shifted for a Ce complex. The emission spectra of the six Nd, Eu, and Dy complexes do not show large differences based on the ligand and are generally consistent with the well-known free-ion spectra. Time-dependent density functional theory results show that 1-Ce and 3-Ce undergo allowed 5f → 4d excitations, consistent with luminescence lifetime measurements in the nanosecond range. Eu-containing 2-Eu and 4-Eu, however, were found to have luminescence lifetimes in the millisecond range, indicating phosphorescence rather than fluorescence. The performance of a pair of multireference models for prediction of the Ln = Nd, Eu, and Dy absorption spectra was assessed. It was found that spectroscopy-oriented configuration interaction as applied to a simplified model in which the free-ion lanthanide was embedded in ligand-centered Löwdin point charges performed as well (Nd) or better (Eu and Dy) than canonical NEVPT2 calculations, when the ligand orbitals were included in the treatment. 

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