Rational design of single-molecule magnets: a supramolecular approach

The rationalization of single molecule magnets’ (SMMs) magnetic properties by quantum mechanical approaches represents a major task in the field of the Molecular Magnetism. The fundamental interpretative key of molecular magnetism is the phenomenological Spin Hamiltonian and the understanding of the role of its different terms by electronic structure calculations is expected to steer the rational design of new and more performing SMMs. This paper deals with the ab initio calculation of isotropic and anisotropic exchange contributions in the Fe(III) dimer [Fe2(OCH3)2(dbm)4]. This system represents the building block of one of the most studied Single Molecule Magnets ([Fe4RC(CH2O)3)2(dpm)6] where R can be an aliphatic chain or a phenyl group just to name the most common functionalization groups) and its relatively reduced size allows the use of a high computational level of theory. Calculations were performed using CASSCF and NEVPT2 approaches on the X-ray geometry as assessment of the computational protocol, which has then be used to evinced the importance of the outer coordination shell nature through organic ligand modelization. Magneto-structural correlations as function of internal degrees of freedom for isotropic and anisotropic exchange contributions are also presented, outlining for the first time the extremely rapidly changing nature of the anisotropic exchange coupling.

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Property-Oriented Rational Design of Single-Molecule Magnets: AC3-Symmetric Mn6Cr Complex based on Three Molecular Building Blocks with a Spin Ground State ofSt=21/2

Angewandte Chemie International Edition ◽

10.1002/anie.200600712 ◽

2006 ◽

Vol 45 (36) ◽

pp. 6033-6037 ◽

Cited By ~ 128

Author(s):

Thorsten Glaser ◽

Maik Heidemeier ◽

Thomas Weyhermüller ◽

Rolf-Dieter Hoffmann ◽

Holger Rupp ◽

...

Keyword(s):

Single Molecule ◽

Ground State ◽

Rational Design ◽

Building Blocks ◽

Single Molecule Magnets ◽

Molecular Building Blocks ◽

Spin Ground State

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Predesigned rigid dysprosium(III) single-molecule magnets exhibit preserved superparamagnetism in solution

10.21203/rs.3.rs-423368/v1 ◽

2021 ◽

Author(s):

Xia-Li Ding ◽

Qian-Cheng Luo ◽

Yuan-Qi Zhai ◽

Xu-Feng Zhang ◽

Yi Lyu ◽

...

Keyword(s):

Single Molecule ◽

High Performance ◽

Rational Design ◽

Magnetic Moments ◽

Low Energy ◽

Local Geometry ◽

Vibration Modes ◽

Single Molecule Magnets ◽

Single Molecule Magnet ◽

Intrinsic Magnetic Property

Abstract Molecules with long preserved magnetic moments are perceived as the smallest units for storing bytes, which could bring a new revolution for information technology. However, the rational design of such molecules remains challenging. Here we show it is possible to predesign such molecules by studying the vibration spectra. Two adamantanol based dysprosium(III) complexes with pentagonal-bipyramidal local geometry were theoretically predicted to display enhanced single-molecule magnet (SMM) behavior due to the reduced vibration modes in low energy regimes. The experimental isolation of these two complexes not only confirms this prediction, but further reveals almost unchanged large energy barriers and high blocking temperatures in solution state. This is never observed in previous studies of SMMs, indicating that the adamantanol ligand is rigid enough to make the complexes exhibiting intrinsic magnetic property in solution. As vibration spectrometer is routinely accessible in common laboratories this work provides a facile strategy to construct high-performance SMMs.

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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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Correlating Blocking Temperatures in Single Molecule Magnets with Raman Relaxation

10.26434/chemrxiv.7067669 ◽

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 (SMM) with an energy barrier of 1110 K for thermal relaxation of magnetization. The sample shows no retention of magnetization even at 2 K and this led us to find a good correlation between the blocking temperature and the Raman relaxation regime for SMMs. The key parameter is the relaxation time (𝜏switch) at the point where the Raman relaxation mechanism becomes more important than Orbach.

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

10.26434/chemrxiv.7445939.v1 ◽

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 (nSF-IP or nSF-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 N2+ 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-nSF-IP/EA scheme) are also examined, with particular emphasis on hole and particle excitations.</div>

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