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1. Trends in trigonal prismatic Ln-[1]ferrocenophane complexes and discovery of a Ho ³⁺ single-molecule magnet

   https://doi.org/10.1039/D0SC01197E  

   Latendresse, Trevor P.; Vieru, Veacheslav; Upadhyay, Apoorva; Bhuvanesh, Nattamai S.; Chibotaru, Liviu F.; Nippe, Michael (April 2020, Chemical Science)

   Lanthanide metallocenophanes are an intriguing class of organometallic complexes that feature rare six-coordinate trigonal prismatic coordination environments of 4f elements with close intramolecular proximity to transition metal ions. Herein, we present a systematic study of the structural and magnetic properties of the ferrocenophanes, [LnFc 3 (THF) 2 Li 2 ] − , of the late trivalent lanthanide ions (Ln = Gd ( 1 ), Ho ( 2 ), Er ( 3 ), Tm ( 4 ), Yb ( 5 ), Lu ( 6 )). One major structural trend within this class of complexes is the increasing diferrocenyl (Fc 2− ) average twist angle with decreasing ionic radius ( r ion ) of the central Ln ion, resulting in the largest average Fc 2− twist angles for the Lu 3+ compound 6 . Such high sensitivity of the twist angle to changes in r ion is unique to the here presented ferrocenophane complexes and likely due to the large trigonal plane separation enforced by the ligand (>3.2 Å). This geometry also allows the non-Kramers ion Ho 3+ to exhibit slow magnetic relaxation in the absence of applied dc fields, rendering compound 2 a rare example of a Ho-based single-molecule magnet (SMM) with barriers to magnetization reversal ( U ) of 110–131 cm −1 . In contrast, compounds featuring Ln ions with prolate electron density ( 3–5 ) don't show slow magnetization dynamics under the same conditions. The observed trends in magnetic properties of 2–5 are supported by state-of-the-art ab initio calculations. Finally, the magneto-structural relationship of the trigonal prismatic Ho-[1]ferrocenophane motif was further investigated by axial ligand (THF in 2 ) exchange to yield [HoFc 3 (THF*) 2 Li 2 ] − ( 2-THF* ) and [HoFc 3 (py) 2 Li 2 ] − ( 2-py ) motifs. We find that larger average Fc 2− twist angles (in 2-THF* and 2-py as compared to in 2 ) result in faster magnetic relaxation times at a given temperature. 

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2. Direct Observation of Magnetic Transitions in a Nickel(II) Complex with Large Anisotropy

   https://doi.org/10.11862/CJIC.2020.126  

   Chelsea N. Widener, Alexandria N. (June 2020, Wuji huaxue xuebao)

   Trigonal bipyramidal Ni(II) complex [Ni(Me6tren)Cl](ClO4) (1, Me6tren = tris[2-(dimethylamino)ethyl]amine) has recently been shown by Ruamps and coworkers to possess large, uniaxial magnetic anisotropy (J. Am. Chem. Soc. 2013, 135, 3017). Their HF-EPR studies gave rhombic zero-field-splitting (ZFS) parameter E = 1.56(5) cm-1 for 1. However, the axial ZFS parameter D has not been determined. We have used far-IR magnetic spectroscopy (FIRMS) at 0-17.5 T and 5 K to probe the magnetic transitions between the MS = 1 and MS = 0 states of the ground spin state S = 1 in 1. Direct observation of the transitions between Zeeman-split states in FIRMS give axial ZFS parameter D = -110.7(3) cm-1. Hirshfeld surface analysis of the crystal structure of 1 has been performed, revealing the interactions between the cation and anion in a molecule of 1 as well as among the molecules of 1 in crystals. 

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3. Axial Elongation of Mononuclear Lanthanide Metallocenophanes: Magnetic Properties of Dysprosium‐ and Terbium‐[1]Ruthenocenophane Complexes

   https://doi.org/10.1002/anie.202003759  

   Risica, Gabrielle M.; Vieru, Veacheslav; Wilkins, Branford O.; Latendresse, Trevor P.; Reibenspies, Joseph H.; Bhuvanesh, Nattamai S.; Wylie, Gregory P.; Chibotaru, Liviu F.; Nippe, Michael (May 2020, Angewandte Chemie International Edition)

   Abstract We report the first f‐block‐ruthenocenophane complexes1(Dy) and2(Tb) and provide a comparative discussion of their magnetic structure with respect to earlier reported ferrocenophane analogues. While axial elongation of the rare trigonal‐prismatic geometry stabilizes the magnetic ground state in the case of Dy³⁺and results in a larger barrier to magnetization reversal (U), a decrease inUis observed for the case of Tb³⁺. 

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4. An Investigation into the Role of Dislocation Climb During Intermediate Temperature Flow of Mg Alloys

   https://doi.org/10.1007/978-3-030-36647-6_19  

   Ritzo, Michael A; Bhattacharyya, Jishnu J; Lebensohn, Ricardo A; Agnew, Sean R (January 2020, Magnesium Technology 2020)

   Textured Mg alloy sheet samples were tensile tested parallel to the transverse direction, at Zener–Hollomon parameter values ranging from Z ~ 50 at room temperature and 10−3 s−1 down to Z ~ 18 at 350 °C and 10−5 s−1. At high Z, the samples exhibit strong texture evolution indicative of significant prismatic slip of dislocations with  Burgers vectors. Correspondingly, the plastic anisotropy is high, r ~ 4. At low Z, the texture evolution is minimal and the response is nearly isotropic, r ~ 1. Previously, it has been asserted that the high ductility and low plastic anisotropy observed at low Z conditions is due to enhanced activity of non-basal slip modes, including prismatic slip of  dislocations and pyramidal slip of  and  dislocations. The present results call this understanding into question and suggest that the enhanced ductility is more closely associated with the climb of  dislocations. 

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5. Colossal Optical Anisotropy from Atomic‐Scale Modulations

   https://doi.org/10.1002/adma.202303588  

   Mei, Hongyan; Ren, Guodong; Zhao, Boyang; Salman, Jad; Jung, Gwan_Yeong; Chen, Huandong; Singh, Shantanu; Thind, Arashdeep_S; Cavin, John; Hachtel, Jordan_A; et al (September 2023, Advanced Materials)

   Abstract Materials with large birefringence (Δn, wherenis the refractive index) are sought after for polarization control (e.g., in wave plates, polarizing beam splitters, etc.), nonlinear optics, micromanipulation, and as a platform for unconventional light–matter coupling, such as hyperbolic phonon polaritons. Layered 2D materials can feature some of the largest optical anisotropy; however, their use in most optical systems is limited because their optical axis is out of the plane of the layers and the layers are weakly attached. This work demonstrates that a bulk crystal with subtle periodic modulations in its structure—Sr_9/8TiS₃—is transparent and positive‐uniaxial, with extraordinary indexn_e= 4.5 and ordinary indexn_o= 2.4 in the mid‐ to far‐infrared. The excess Sr, compared to stoichiometric SrTiS₃, results in the formation of TiS₆trigonal‐prismatic units that break the chains of face‐sharing TiS₆octahedra in SrTiS₃into periodic blocks of five TiS₆octahedral units. The additional electrons introduced by the excess Sr form highly oriented electron clouds, which selectively boost the extraordinary indexn_eand result in record birefringence (Δn> 2.1 with low loss). The connection between subtle structural modulations and large changes in refractive index suggests new categories of anisotropic materials and also tunable optical materials with large refractive‐index modulation. 

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