Zero-Field Quantum Tunneling of the Magnetization in a Series of High Energy-Barrier Dysprosium (III) Single-Molecule Magnets

Energy barriers to magnetisation reversal (Ueff) in single-molecule magnets (SMMs) have vastly increased recently, but only for the dysprosocenium SMM [Dy(Cpttt)2][B(C6F5)4] (Cpttt = C5H2tBu3-1,2,4) has this translated into a considerable increase in magnetic hysteresis temperatures. The lack of concomitant increases in hysteresis temperatures with Ueff values is due to efficient magnetic relaxation at zero-field, referred to as quantum tunnelling of the magnetisation (QTM); however, the exact nature of this phenomenon is unknown. Recent hypotheses suggest that both transverse dipolar magnetic fields and hyperfine coupling play a significant role in this process for Dy(III) SMMs. Here, by studying the compounds [Dy(tBuO)Cl(THF)5][BPh4] (1), [K(18-crown-6-ether)(THF)2][Dy(BIPM)2] (2, BIPM = C{PPh2NSiMe3}2), and [Dy(Cpttt)2][B(C6F5)4] (3), we show conclusively that neither of these processes are the main contributor to zero-field QTM for Dy(III) SMMs, and suggest that its origin instead owes to molecular flexibility. By analysing the vibrational modes of the three molecules, we show that the modes that most impact the magnetic ion occur at the lowest energies for 1, at intermediate energies for 2 and at higher energies for 3, in correlation with their ability to retain magnetisation. Therefore, we conclude that SMM performance could be improved by employing more rigid ligands with higher-energy metal-ligand vibrational modes.

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See-Saw Shaped Dy(III) Single-Molecule Magnets with High Anisotropy Barriers

10.26434/chemrxiv.11673927 ◽

2020 ◽

Author(s):

Katie L. M. Harriman ◽

Jesse Murillo ◽

Elizaveta A. Suturina ◽

Skye Fortier ◽

Muralee Murugesu

Keyword(s):

Magnetic Susceptibility ◽

Single Molecule ◽

Molecular Geometry ◽

High Energy ◽

Zero Field ◽

Relaxation Dynamics ◽

Single Molecule Magnets ◽

Ancillary Ligands ◽

Spin Reversal ◽

Magnetic Spin

Utilizing a terphenyl bisanilide ligand, two Dy(III) complexes [K(DME)x][LArDy(X)2] (LAr = {C6H4[(2,6-iPrC6H3)NC6H4]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 complex with near-linear N-Dy-N (avg. 159.9° for1 and avg. 160.3o for 2) bond angles. These complexes exhibit Single-Molecule Magnet (SMM) behavior with significant uniaxial magnetic anisotropy as a result of the transverse coordination of the bisanlide ligand which yields high energy barriers to magnetic spin reversal of Ueff = 1334 K/ 927cm-1 (1) and 1299 K/ 903 cm-1 (2) in zero field. Magneto-structural correlations are discussed with the goal of finding a link between halide ancillary ligands in the structurally analogous complexes and the through barrier relaxation dynamics observed in the ac magnetic susceptibility, despite the similar dc magnetic susceptibility for compounds 1 and 2. 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, and defines the height of the energy barrier. Thus, further validating the use of transverse ligands to enhance the SMM properties of Dy(III) ions.

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Molecular Engineering of High Energy Barrier in Single-Molecule Magnets Based on [MoIII(CN)7]4− and V(II) Complexes

Inorganics ◽

10.3390/inorganics6020058 ◽

2018 ◽

Vol 6 (2) ◽

pp. 58 ◽

Cited By ~ 3

Author(s):

Vladimir Mironov

Keyword(s):

Single Molecule ◽

Energy Barrier ◽

High Energy ◽

Molecular Engineering ◽

Single Molecule Magnets ◽

High Energy Barrier

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See-Saw Shaped Dy(III) Single-Molecule Magnets with High Anisotropy Barriers

10.26434/chemrxiv.11673927.v1 ◽

2020 ◽

Author(s):

Katie L. M. Harriman ◽

Jesse Murillo ◽

Elizaveta A. Suturina ◽

Skye Fortier ◽

Muralee Murugesu

Keyword(s):

Magnetic Susceptibility ◽

Single Molecule ◽

Molecular Geometry ◽

High Energy ◽

Zero Field ◽

Relaxation Dynamics ◽

Single Molecule Magnets ◽

Ancillary Ligands ◽

Spin Reversal ◽

Magnetic Spin

Utilizing a terphenyl bisanilide ligand, two Dy(III) complexes [K(DME)x][LArDy(X)2] (LAr = {C6H4[(2,6-iPrC6H3)NC6H4]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 complex with near-linear N-Dy-N (avg. 159.9° for1 and avg. 160.3o for 2) bond angles. These complexes exhibit Single-Molecule Magnet (SMM) behavior with significant uniaxial magnetic anisotropy as a result of the transverse coordination of the bisanlide ligand which yields high energy barriers to magnetic spin reversal of Ueff = 1334 K/ 927cm-1 (1) and 1299 K/ 903 cm-1 (2) in zero field. Magneto-structural correlations are discussed with the goal of finding a link between halide ancillary ligands in the structurally analogous complexes and the through barrier relaxation dynamics observed in the ac magnetic susceptibility, despite the similar dc magnetic susceptibility for compounds 1 and 2. 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, and defines the height of the energy barrier. Thus, further validating the use of transverse ligands to enhance the SMM properties of Dy(III) ions.

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New members of the polynuclear manganese family: MnII2MnIII2 single-molecule magnets and MnII3MnIII8 antiferromagnetic complexes. Synthesis and magnetostructural correlations

Dalton Transactions ◽

10.1039/d0dt02652b ◽

2020 ◽

Vol 49 (40) ◽

pp. 13970-13985

Author(s):

Nuno Reis Conceição ◽

Oksana V. Nesterova ◽

Cyril Rajnák ◽

Roman Boča ◽

Armando J. L. Pombeiro ◽

...

Keyword(s):

Single Molecule ◽

Energy Barrier ◽

High Energy ◽

Single Molecule Magnets ◽

New Members ◽

High Energy Barrier ◽

Tetranuclear Complexes

Three novel Mn4 and Mn11 complexes were synthesized and characterized. Tetranuclear complexes behave as single-molecule magnets with a high energy barrier.

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Seeking Magneto-Structural Correlations in Easily Tailored Pentagonal Bipyramid Dy(III) Single-Ion Magnets

10.26434/chemrxiv.11475291 ◽

2019 ◽

Author(s):

Guo-Zhang Huang ◽

Ze-Yu Ruan ◽

Jie-Yu Zheng ◽

Yan-Cong Chen ◽

Si-Guo Wu ◽

...

Keyword(s):

Single Molecule ◽

Structural Engineering ◽

Magnetic Hysteresis ◽

Sweep Rate ◽

Coordination Bond ◽

Pentagonal Bipyramid ◽

Single Molecule Magnets ◽

Crystal Field Theory ◽

Bond Angles ◽

Axial Coordination

<a></a>Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating, especially for single-molecule magnets (SMMs). Herein a family of dysprosium single-ion magnets (SIMs) sitting in pentagonal bipyramid geometry have been synthesized with the variable-size terminal ligands and counter anions, through which the subtle coordination geometry of Dy(III) can be finely tuned based on the size effect. The effective energy barrier (Ueff) successfully increases from 439 K to 632 K and the magnetic hysteresis temperature (under a 200 Oe/s sweep rate) raises from 11 K to 24 K. Based on the crystal-field theory, a semi-quantitative magneto-structural correlation deducing experimentally for the first time is revealed that the Ueff is linearly proportional to the structural-related value S20 corresponding to the axial coordination bond lengths and the bond angles. Through the evaluation of the remanent magnetization from hysteresis, quantum tunneling of magnetization (QTM) is found to exhibit negative correlation with the structural-related value Stun corresponding to the axial coordination bond angles.

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Slow magnetic relaxation in dinuclear dysprosium and holmium phenoxide bridged complexes: a Dy2 single molecule magnet with a high energy barrier

Inorganic Chemistry Frontiers ◽

10.1039/d1qi00152c ◽

2021 ◽

Author(s):

Matilde Fondo ◽

Julio Corredoira-Vázquez ◽

Ana M. Garcia-Deibe ◽

Jesus Sanmartin Matalobos ◽

Silvia Gómez-Coca ◽

...

Keyword(s):

Crystal Structures ◽

Single Molecule ◽

Energy Barrier ◽

Magnetic Relaxation ◽

High Energy ◽

Single Molecule Magnet ◽

High Energy Barrier ◽

Slow Magnetic Relaxation

Dinuclear [M(H3L1,2,4)]2 (M = Dy, Dy2; M = Ho, Ho2) complexes were isolated from an heptadentate aminophenol ligand. The crystal structures of Dy2·2THF, and the pyridine adducts Dy2·2Py and Ho2·2Py,...

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Strictly linear trinuclear Dy–Ca/Mg–Dy single-molecule magnets: the impact of long-range f–f ferromagnetic interactions on suppressing quantum tunnelling of magnetization leading to slow magnetic relaxation

Dalton Transactions ◽

10.1039/c7dt01395g ◽

2017 ◽

Vol 46 (25) ◽

pp. 8259-8268 ◽

Cited By ~ 6

Author(s):

Wan-Ying Zhang ◽

Yong-Mei Tian ◽

Hong-Feng Li ◽

Peng Chen ◽

Yi-Quan Zhang ◽

...

Keyword(s):

Long Range ◽

Single Molecule ◽

Magnetic Relaxation ◽

Single Molecule Magnets ◽

Quantum Tunnelling ◽

Trinuclear Complexes ◽

Slow Magnetic Relaxation ◽

Ferromagnetic Interactions ◽

The Impact

A series of linear trinuclear complexes Ln2M(OQ)8 [Ln(iii) = Dy and Er, M(ii) = Ca and Mg] were structurally and magnetically investigated.

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New Silver(I) Coordination Polymer with Fe4 Single-Molecule Magnets as Long Spacer

Magnetochemistry ◽

10.3390/magnetochemistry4040043 ◽

2018 ◽

Vol 4 (4) ◽

pp. 43 ◽

Cited By ~ 1

Author(s):

Luca Rigamonti ◽

Manuela Vaccari ◽

Fabrizio Roncaglia ◽

Carlo Baschieri ◽

Alessandra Forni

Keyword(s):

Coordination Polymer ◽

Single Molecule ◽

Building Blocks ◽

Zero Field ◽

Single Molecule Magnets ◽

Long Distance ◽

Linear Arrangement ◽

Thermally Activated ◽

Supramolecular Architectures ◽

Donor Nitrogen

In continuation of our work on supramolecular architectures of single-molecule magnets (SMMs) as a promising strategy in developing their magnetic performance, in this paper we report the synthesis and single crystal X-ray structure of the centered triangular tetrairon(III) SMM, [Fe4(PhpPy)2(dpm)6], Fe4 (Hdpm = dipivaloylmethane, H3PhpPy = 2-(hydroxymethyl)-2-(4-(pyridine-4-yl)phenyl)propane-1,3-diol), and its assembly in the coordination polymer {[Fe4(PhpPy)2(dpm)6Ag](ClO4)}n, Fe4Ag, upon reaction with silver(I) perchlorate. Thanks to the presence of the pyridyl rings on the two tripodal ligands, Fe4 behaves as divergent ditopic linker, and due to the Fe4:AgClO4 1:1 ratio, Fe4Ag probably possesses a linear arrangement in which silver(I) ions are linearly coordinated by two nitrogen atoms, forming 1D chains whose positive charge is balanced by the perchlorate anions. The stabilization of such a polymeric structure can be ascribed to the long distance between the two donor nitrogen atoms (23.4 Å) and their donor power. Fe4Ag shows slow relaxation of the magnetization which follows a thermally activated process with Ueff/kB = 11.17(18) K, τ0 = 2.24(17) 10−7 s in zero field, and Ueff/kB = 14.49(5) K, τ0 = 3.88(8) 10−7 s in 1-kOe applied field, in line with what reported for tetrairon(III) SMMs acting as building blocks in polymeric structures.

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Vibrational Coherences in Manganese Single-molecule Magnets after Ultrafast Photoexcitation

10.26434/chemrxiv.7485011.v1 ◽

2018 ◽

Author(s):

Florian Liedy ◽

Robbie McNab ◽

Julien Eng ◽

Ross Inglis ◽

Thomas Penfold ◽

...

Keyword(s):

Data Storage ◽

Single Molecule ◽

Optical Data Storage ◽

Transient Absorption Spectroscopy ◽

Optical Data ◽

Zero Field ◽

Zero Field Splitting ◽

Single Molecule Magnets ◽

Teller Distortion ◽

Jahn Teller

Single-Molecule Magnets (SMMs) are metal complexes with two degenerate magnetic ground states arising from a non-zero spin ground state and a zero-field splitting. SMMs are promising for future applications in data storage, however, to date the ability to manipulate the spins using optical stimulus is lacking. Here, we have explored the ultrafast dynamics occurring after photoexcitation of two structurally related Mn(III)-based SMMs, whose magnetic anisotropy is closely related to the Jahn-Teller distortion, and demonstrate coherent modulation of the axial anisotropy on a femtosecond timescale. Ultrafast transient absorption spectroscopy in solution reveals oscillations superimposed on the decay traces with corresponding energies around 200 cm−1, coinciding with a vibrational mode along the Jahn-Teller axis. Our results provide a non-thermal, coherent mechanism to dynamically control the magnetisation in SMMs and open up new molecular design challenges to enhance the change in anisotropy in the excited state, which is essential for future ultrafast magneto-optical data storage devices.

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