Anisotropy barrier enhancement via ligand substitution in tetranuclear {CoIII2LnIII2} single molecule magnets

2013 ◽  
Vol 49 (62) ◽  
pp. 6965 ◽  
Author(s):  
Stuart K. Langley ◽  
Nicholas F. Chilton ◽  
Boujemaa Moubaraki ◽  
Keith S. Murray
Keyword(s):  
Single Molecule ◽  
Ligand Substitution ◽  
Single Molecule Magnets

scholarly journals Influence of ligand substitution on magnetic hyperfine interaction in Dy6-based single-molecule magnets/toroics

2019 ◽  
Vol 240 (1) ◽  
Author(s):  
Lena Scherthan ◽  
Thomas Ruppert ◽  
Yan Peng ◽  
Amer Baniodeh ◽  
Hendrik Auerbach ◽  
...  
Keyword(s):  
Hyperfine Interaction ◽  
Single Molecule ◽  
Ligand Substitution ◽  
Magnetic Hyperfine ◽  
Single Molecule Magnets ◽  
Magnetic Hyperfine Interaction

scholarly journals Energy-Barrier Enhancement by Ligand Substitution in Tetrairon(III) Single-Molecule Magnets

2004 ◽  
Vol 116 (9) ◽  
pp. 1156-1159 ◽  
Author(s):  
Andrea Cornia ◽  
Antonio C. Fabretti ◽  
Pierfrancesco Garrisi ◽  
Cecilia Mortalò ◽  
Daniele Bonacchi ◽  
...  
Keyword(s):  
Single Molecule ◽  
Energy Barrier ◽  
Ligand Substitution ◽  
Single Molecule Magnets

scholarly journals Energy-Barrier Enhancement by Ligand Substitution in Tetrairon(III) Single-Molecule Magnets

2004 ◽  
Vol 43 (9) ◽  
pp. 1136-1139 ◽  
Author(s):  
Andrea Cornia ◽  
Antonio C. Fabretti ◽  
Pierfrancesco Garrisi ◽  
Cecilia Mortalò ◽  
Daniele Bonacchi ◽  
...  
Keyword(s):  
Single Molecule ◽  
Energy Barrier ◽  
Ligand Substitution ◽  
Single Molecule Magnets

scholarly journals Insensitivity of Magnetic Coupling to Ligand Substitution in a Series of Tetraoxolene Radical-Bridged Fe2 Complexes

2019 ◽  
Author(s):  
Agnes Thorarindottir ◽  
Ragnar Bjornsson ◽  
T. David Harris
Keyword(s):  
Single Molecule ◽  
Magnetic Measurements ◽  
Variable Temperature ◽  
Magnetic Coupling ◽  
Ligand Substitution ◽  
X Ray Diffraction ◽  
Single Molecule Magnets ◽  
Susceptibility Data ◽  
Bridging Ligand ◽  
Exchange Constants

<p>The elucidation of magnetostructural correlations between bridging ligand substitution and strength of magnetic coupling is essential to the development of high-temperature molecule-based magnetic materials. Toward this end, we report the series of tetraoxolene-bridged Fe<sup>II</sup><sub>2</sub> complexes [(Me<sub>3</sub>TPyA)<sub>2</sub>Fe<sub>2</sub>(<sup>R</sup>L)]<i><sup>n</sup></i><sup>+</sup> (Me<sub>3</sub>TPyA = tris(6-methyl-2-pyridylmethyl)amine; <i>n</i> = 2: <sup>OMe</sup>LH<sub>2</sub> = 3,6-dimethoxy-2,5-dihydroxo-1,4-benzoquinone, <sup>Cl</sup>LH<sub>2</sub> = 3,6-dichloro-2,5-dihydroxo-1,4-benzoquinone, Na<sub>2</sub>[<sup>NO2</sup>L] = sodium 3,6-dinitro-2,5-dihydroxo-1,4-benzoquinone; <i>n</i> = 0: <sup>SMe2</sup>L = 3,6-bis(dimethylsulfonium)-2,5-dihydroxo-1,4-benzoquinone diylide) and their one-electron-reduced analogues. Variable-temperature dc magnetic susceptibility data reveal the presence of weak ferromagnetic superexchange between Fe<sup>II</sup> centers in the oxidized species, with exchange constants of <i>J</i> = +1.2(2) (R = OMe, Cl) and +0.3(1) (R = NO<sub>2</sub>, SMe<sub>2</sub>) cm<sup>−1</sup>. In contrast, X-ray diffraction, cyclic voltammetry, and Mössbauer spectroscopy establish a ligand-centered radical in the reduced complexes. Magnetic measurements for the radical-bridged species reveal the presence of strong antiferromagnetic metal–radical coupling, with <i>J</i> = −57(10), −60(5), −58(6), and −65(8) cm<sup>−1</sup> for R = OMe, Cl, NO<sub>2</sub>, and SMe<sub>2</sub>, respectively. The minimal effects of substituents in the 3- and 6-positions of <sup>R</sup>L<i><sup>x</sup></i><sup>−•</sup> on the magnetic coupling strength is understood through electronic structure calculations, which show negligible spin density on the substituents and associated C atoms of the ring. Finally, the radical-bridged complexes are single-molecule magnets, with relaxation barriers of <i>U</i><sub>eff </sub>= 50(1), 41(1), 38(1), and 33(1) cm<sup>−1</sup> for R = OMe, Cl, NO<sub>2</sub>, and SMe<sub>2</sub>, respectively. Taken together, these results provide the first examination of how bridging ligand substitution influences magnetic coupling in semiquinoid-bridged compounds, and they establish design criteria for the synthesis of semiquinoid-based molecules and materials. </p>

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

2018 ◽  
Vol 9 (45) ◽  
pp. 8492-8503 ◽  
Author(s):  
K. Randall McClain ◽  
Colin A. Gould ◽  
Khetpakorn Chakarawet ◽  
Simon J. Teat ◽  
Thomas J. Groshens ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Magnetic Properties ◽  
High Temperature ◽  
Single Molecule ◽  
Ligand Substitution ◽  
Single Molecule Magnets

Subtle changes in ligand substitution result in substantial changes in molecular structure and magnetic properties in a series of dysprosium(iii) metallocenium salts.

scholarly journals Effect of Ligand Substitution on the Exchange Interactions in {Mn12}-Type Single-Molecule Magnets

2010 ◽  
Vol 49 (23) ◽  
pp. 10902-10906 ◽  
Author(s):  
Danil W. Boukhvalov ◽  
Viatcheslav V. Dobrovitski ◽  
Paul Kögerler ◽  
Mohammad Al-Saqer ◽  
Mikhail I. Katsnelson ◽  
...  
Keyword(s):  
Single Molecule ◽  
Exchange Interactions ◽  
Ligand Substitution ◽  
Single Molecule Magnets

scholarly journals Insensitivity of Magnetic Coupling to Ligand Substitution in a Series of Tetraoxolene Radical-Bridged Fe2 Complexes

2019 ◽  
Author(s):  
Agnes Thorarindottir ◽  
Ragnar Bjornsson ◽  
T. David Harris
Keyword(s):  
Single Molecule ◽  
Magnetic Measurements ◽  
Variable Temperature ◽  
Magnetic Coupling ◽  
Ligand Substitution ◽  
X Ray Diffraction ◽  
Single Molecule Magnets ◽  
Susceptibility Data ◽  
Bridging Ligand ◽  
Exchange Constants

<p>The elucidation of magnetostructural correlations between bridging ligand substitution and strength of magnetic coupling is essential to the development of high-temperature molecule-based magnetic materials. Toward this end, we report the series of tetraoxolene-bridged Fe<sup>II</sup><sub>2</sub> complexes [(Me<sub>3</sub>TPyA)<sub>2</sub>Fe<sub>2</sub>(<sup>R</sup>L)]<i><sup>n</sup></i><sup>+</sup> (Me<sub>3</sub>TPyA = tris(6-methyl-2-pyridylmethyl)amine; <i>n</i> = 2: <sup>OMe</sup>LH<sub>2</sub> = 3,6-dimethoxy-2,5-dihydroxo-1,4-benzoquinone, <sup>Cl</sup>LH<sub>2</sub> = 3,6-dichloro-2,5-dihydroxo-1,4-benzoquinone, Na<sub>2</sub>[<sup>NO2</sup>L] = sodium 3,6-dinitro-2,5-dihydroxo-1,4-benzoquinone; <i>n</i> = 0: <sup>SMe2</sup>L = 3,6-bis(dimethylsulfonium)-2,5-dihydroxo-1,4-benzoquinone diylide) and their one-electron-reduced analogues. Variable-temperature dc magnetic susceptibility data reveal the presence of weak ferromagnetic superexchange between Fe<sup>II</sup> centers in the oxidized species, with exchange constants of <i>J</i> = +1.2(2) (R = OMe, Cl) and +0.3(1) (R = NO<sub>2</sub>, SMe<sub>2</sub>) cm<sup>−1</sup>. In contrast, X-ray diffraction, cyclic voltammetry, and Mössbauer spectroscopy establish a ligand-centered radical in the reduced complexes. Magnetic measurements for the radical-bridged species reveal the presence of strong antiferromagnetic metal–radical coupling, with <i>J</i> = −57(10), −60(5), −58(6), and −65(8) cm<sup>−1</sup> for R = OMe, Cl, NO<sub>2</sub>, and SMe<sub>2</sub>, respectively. The minimal effects of substituents in the 3- and 6-positions of <sup>R</sup>L<i><sup>x</sup></i><sup>−•</sup> on the magnetic coupling strength is understood through electronic structure calculations, which show negligible spin density on the substituents and associated C atoms of the ring. Finally, the radical-bridged complexes are single-molecule magnets, with relaxation barriers of <i>U</i><sub>eff </sub>= 50(1), 41(1), 38(1), and 33(1) cm<sup>−1</sup> for R = OMe, Cl, NO<sub>2</sub>, and SMe<sub>2</sub>, respectively. Taken together, these results provide the first examination of how bridging ligand substitution influences magnetic coupling in semiquinoid-bridged compounds, and they establish design criteria for the synthesis of semiquinoid-based molecules and materials. </p>

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

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

<p><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 S2<sup>0</sup> 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 S<sub>tun</sub> corresponding to the axial coordination bond angles.<br></p>

Correlating Blocking Temperatures in Single Molecule Magnets with Raman Relaxation

2018 ◽  
Author(s):  
Marcus J. Giansiracusa ◽  
Andreas Kostopoulos ◽  
George F. S. Whitehead ◽  
David Collison ◽  
Floriana Tuna ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Single Molecule ◽  
Energy Barrier ◽  
Thermal Relaxation ◽  
Relaxation Mechanism ◽  
Blocking Temperature ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Key Parameter

We report a six coordinate DyIII single-molecule magnet<br>(SMM) with an energy barrier of 1110 K for thermal relaxation of<br>magnetization. The sample shows no retention of magnetization<br>even at 2 K and this led us to find a good correlation between the<br>blocking temperature and the Raman relaxation regime for SMMs.<br>The key parameter is the relaxation time (𝜏<sub>switch</sub>) at the point where<br>the Raman relaxation mechanism becomes more important than<br>Orbach.

A Combined Spin-Flip and IP/EA Approach for Handling Spin and Spatial Degeneracies: Application to Double Exchange Systems

2018 ◽  
Author(s):  
Shannon Houck ◽  
Nicholas Mayhall
Keyword(s):  
Single Molecule ◽  
Double Exchange ◽  
Computational Effort ◽  
Strongly Correlated ◽  
Single Molecule Magnets ◽  
New Approach ◽  
Spin Flip ◽  
Model Hamiltonian ◽  
Simultaneous Existence ◽  
Exchange Parameters

<div>Many multiconfigurational systems, such as single-molecule magnets, are difficult to study using traditional computational methods due to the simultaneous existence of both spin and spatial degeneracies. In this work, a new approach termed n-spin-flip Ionization Potential/Electron Affinity (<i>n</i>SF-IP or <i>n</i>SF-EA) is introduced which combines the spin-flip method of Anna Krylov with particle-number changing IP/EA methods. We demonstrate the efficacy of the approach by applying it to the strongly-correlated N<sub>2</sub><sup>+</sup> as well as several double exchange systems. We also demonstrate that when these systems are well-described by a double exchange model Hamiltonian, only 1SF-IP/EA is required to extract the double exchange parameters and accurately predict energies for the low-spin states. This significantly reduces the computational effort for studying such systems. The effects of including additional excitations (using a RAS-<i>n</i>SF-IP/EA scheme) are also examined, with particular emphasis on hole and particle excitations.</div>

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