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1. Exchange-biased quantum tunnelling of magnetization in a [Mn 3 ] 2 dimer of single-molecule magnets with rare ferromagnetic inter-Mn 3 coupling

   https://doi.org/10.1039/d0cp06611g  

   Ghosh, Tuhin ; Marbey, Jonathan ; Wernsdorfer, Wolfgang ; Hill, Stephen ; Abboud, Khalil A. ; Christou, George ( April 2021 , Physical Chemistry Chemical Physics)

   null (Ed.)

   A covalently-linked dimer of two single-molecule magnets (SMMs), [Mn 6 O(O 2 CMe) 6 (1,3-ppmd) 3 ](ClO 4 ) 2 , has been synthesized from the reaction of [Mn 3 O(O 2 CMe) 6 (py) 3 ](ClO 4 ) with 1,3-phenylene- bis (pyridin-2-ylmethanone) dioxime (1,3-ppmdH 2 ). It contains two [Mn III 3 O] +7 triangular units linked by three 1,3-ppmd 2− groups into an [Mn 3 ] 2 dimer with D 3 symmetry. Solid-state dc and ac magnetic susceptibility measurements showed that each Mn 3 subunit retains its properties as an SMM with an S = 6 ground state. Magnetization vs. dc field sweeps on a single crystal reveal hysteresis loops below 1.3 K exhibiting exchange-biased quantum tunnelling of magnetization (QTM) steps with a bias field of +0.06 T. This is the first example of a dimer of SMMs showing a positive exchange bias of the QTM steps in the hysteresis loops, and it has therefore been subjected to a detailed analysis. Simulation of the loops determines that each Mn 3 unit is exchange-coupled with its neighbour primarily through the 1,3-ppmd 2− linkers, confirming a weak ferromagnetic inter-Mn 3 interaction of J 12 ≈ +6.5 mK ( Ĥ = −2 JŜ i · Ŝ j convention). High-frequency EPR studies of a microcrystalline powder sample enable accurate determination of the zero-field splitting parameters of the uncoupled Mn 3 SMMs, while also confirming the weak exchange interaction between the two SMMs within each [Mn 3 ] 2 dimer. The combined results emphasize the ability of designed covalent linkers to generate inter-SMM coupling of a particular sign and relative magnitude, and thus the ability of such linkers to modulate the quantum physics. As such, this work supports the feasibility of using designed covalent linkers to develop molecular oligomers of SMMs, or other magnetic molecules, as multi-qubit systems and/or other components of new quantum technologies. 

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2. Crystal Growth of New Germanate Framework Structures: Impact of the Presence of Square Planar Copper Species and Mixed Ge/Mn Sites on the Overall Structures of Rb 2 Cu 3 Ge 5 O 14 , Cs 2 Cu 3 Ge 5 O 14 , Cs 7 Cu 2 Ge 11 O 27 F, and [(Cs 6 F)(Cs 3 AgF)][Ge 12 Mn 2 O 32 ]

   https://doi.org/10.1021/acs.cgd.2c00133  

   Carone, Darren ; Morrison, Gregory ; Smith, Mark D. ; zur Loye, Hans-Conrad ( May 2022 , Crystal Growth & Design)
3. Applying Unconventional Spectroscopies to the Single‐Molecule Magnets, Co(PPh 3 ) 2 X 2 (X=Cl, Br, I): Unveiling Magnetic Transitions and Spin‐Phonon Coupling

   https://doi.org/10.1002/chem.202100705  

   Bone, Alexandria N. ; Widener, Chelsea N. ; Moseley, Duncan H. ; Liu, Zhiming ; Lu, Zhengguang ; Cheng, Yongqiang ; Daemen, Luke L. ; Ozerov, Mykhaylo ; Telser, Joshua ; Thirunavukkuarasu, Komalavalli ; et al ( August 2021 , Chemistry – A European Journal)

   Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single‐molecule magnets (SMMs). Spin‐phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits. Direct observation of magnetic transitions and spin‐phonon coupling in molecules is challenging. We have found that far‐IR magnetic spectra (FIRMS) of Co(PPh₃)₂X₂(Co‐X; X=Cl, Br, I) reveal rarely observed spin‐phonon coupling as avoided crossings between magnetic andu‐symmetry phonon transitions. Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero‐field split (ZFS) levels of theS=3/2 electronic ground state were probed by INS, high‐frequency and ‐field EPR (HFEPR), FIRMS, and frequency‐domain FT terahertz EPR (FD‐FT THz‐EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) andgvalues. Ligand‐field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities inCo‐X, showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude. The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin‐phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling.

    

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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. Hexagonal Bipyramidal Dy(III) Complexes as a Structural Archetype for Single-Molecule Magnets

   https://doi.org/10.1021/acs.inorgchem.8b03206  

   Li, Jing ; Gómez-Coca, Silvia ; Dolinar, Brian S. ; Yang, Li ; Yu, Fei ; Kong, Ming ; Zhang, Yi-Quan ; Song, You ; Dunbar, Kim R. ( February 2019 , Inorganic Chemistry)