scholarly journals Analysis of Exchange Interactions in Dimers of Mn3 Single-Molecule Magnets, and Their Sensitivity to External Pressure

2020 ◽  
Vol 124 (27) ◽  
pp. 14768-14774
Author(s):  
Jie-Xiang Yu ◽  
George Christou ◽  
Hai-Ping Cheng
Keyword(s):  
Single Molecule ◽  
Exchange Interactions ◽  
External Pressure ◽  
Single Molecule Magnets

Mixed valency in polynuclear Mn II /Mn III , Mn III /Mn IV and Mn II /Mn III /Mn IV clusters: a foundation for high-spin molecules and single-molecule magnets

2007 ◽  
Vol 366 (1862) ◽  
pp. 113-125 ◽  
Author(s):  
Theocharis C Stamatatos ◽  
George Christou
Keyword(s):  
Single Molecule ◽  
Exchange Interactions ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Single Molecule Magnets ◽  
Zero Field Splitting Parameter ◽  
Jahn Teller ◽  
Splitting Parameter ◽  
Molecular Spin ◽  
Molecular Compounds

Mixed-valent Mn/O dinuclear and polynuclear molecular compounds containing Mn III are almost without exception trapped valence. Large differences between the strengths of the exchange interactions within Mn II Mn III , Mn III Mn III and Mn III Mn IV pairs lead to situations where Mn III Mn IV interactions, the strongest of the three mentioned and antiferromagnetic in nature, dominate the intramolecular spin alignments in trinuclear and higher nuclearity mixed-valent complexes and often result in molecules that have large, and sometimes abnormally large, values of molecular spin ( S ). When coupled to a large molecular magnetoanisotropy of the easy-axis-type (negative zero-field splitting parameter, D ), also primarily resulting from individual Jahn–Teller distorted Mn III centres, such molecules will function as single-molecule magnets (molecular nanomagnets). Dissection of the structures and exchange interactions within a variety of mixed-valent Mn x cluster molecules with metal nuclearities of Mn 4 , Mn 12 and Mn 25 allows a ready rationalization of the observed S , D and overall magnetic properties in terms of competing antiferromagnetic exchange interactions within triangular subunits, resulting spin alignments and relative orientation of Mn III JT axes. Such an understanding has provided a stepping stone to the identification of a ‘magnetically soft’ Mn 25 cluster whose groundstate spin S value can be significantly altered by relatively minor structural perturbations. Such ‘spin tweaking’ has allowed this cluster to be obtained in three different forms with three different groundstate S values.

Ferromagnetic [Mn3] Single-Molecule Magnets and Their Supramolecular Networks

2009 ◽  
Vol 62 (9) ◽  
pp. 1108 ◽  
Author(s):  
Ross Inglis ◽  
Giannis S. Papaefstathiou ◽  
Wolfgang Wernsdorfer ◽  
Euan K. Brechin
Keyword(s):  
Single Molecule ◽  
Quantum Physics ◽  
Three Dimensional ◽  
Exchange Interactions ◽  
Molecular Magnets ◽  
Single Molecule Magnets ◽  
Spin Networks ◽  
Quantum Tunnelling ◽  
Field Bias ◽  
Supramolecular Networks

The complexes [MnIII3O(Et-sao)3(O2CPh(Cl)2)(MeOH)3(H2O)] (1), [MnIII3O(Et-sao)3(ClO4)(MeOH)3] (2), [MnIII3O(Et-sao)3(O2Ph(CF3)2)(EtOH)(H2O)3] (3), and [MnIII3O(Ph-sao)3(O2C-anthra)(MeOH)4]·Ph-saoH2 (4·Ph-saoH2) display dominant ferromagnetic exchange interactions leading to molecules with S = 6 ground states. The molecules are single molecule magnets (SMM) displaying large effective energy barriers for magnetization reversal. In each case their crystal structures reveal multiple intermolecular H-bonding interactions. Single crystal hysteresis loop measurements demonstrate that these interactions are strong enough to cause a clear field bias, but too weak to transform the spin networks into classical antiferromagnets. These three-dimensional networks of exchange coupled SMMs demonstrate that quantum tunnelling magnetization can be controlled using exchange interactions, suggesting supramolecular chemistry can be exploited to modulate the quantum physics of molecular magnets.

scholarly journals Asymmetric Dinuclear Lanthanide(III) Complexes from the Use of a Ligand Derived from 2-Acetylpyridine and Picolinoylhydrazide: Synthetic, Structural and Magnetic Studies

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3153
Author(s):  
Diamantoula Maniaki ◽  
Panagiota S. Perlepe ◽  
Evangelos Pilichos ◽  
Sotirios Christodoulou ◽  
Mathieu Rouzières ◽  
...  
Keyword(s):  
Single Molecule ◽  
Metal Ion ◽  
Ac Susceptibility ◽  
Solvent Molecule ◽  
Exchange Interactions ◽  
Experimental Fact ◽  
Anisotropy Axis ◽  
Magnetic Studies ◽  
Single Molecule Magnets ◽  
Magnetization Relaxation

A family of four Ln(III) complexes has been synthesized with the general formula [Ln2(NO3)4(L)2(S)] (Ln = Gd, Tb, Er, and S = H2O; 1, 2 and 4, respectively/Ln = Dy, S = MeOH, complex 3), where HL is the flexible ditopic ligand N’-(1-(pyridin-2-yl)ethylidene)pyridine-2-carbohydrazide. The structures of isostructural MeOH/H2O solvates of these complexes were determined by single-crystal X-ray diffraction. The two LnIII ions are doubly bridged by the deprotonated oxygen atoms of two “head-to-head” 2.21011 (Harris notation) L¯ ligands, forming a central, nearly rhombic {LnIII2(μ-OR)2}4+ core. Two bidentate chelating nitrato groups complete a sphenocoronal 10-coordination at one metal ion, while two bidentate chelating nitrato groups and one solvent molecule (H2O or MeOH) complete a spherical capped square antiprismatic 9-coordination at the other. The structures are critically compared with those of other, previously reported metal complexes of HL or L¯. The IR spectra of 1–4 are discussed in terms of the coordination modes of the organic and inorganic ligands involved. The f-f transitions in the solid-state (diffuse reflectance) spectra of the Tb(III), Dy(III), and Er(III) complexes have been fully assigned in the UV/Vis and near-IR regions. Magnetic susceptibility studies in the 1.85–300 K range reveal the presence of weak, intramolecular GdIII∙∙∙GdIII antiferromagnetic exchange interactions in 1 [J/kB = −0.020(6) K based on the spin Hamiltonian Ĥ = −2J(ŜGd1∙ ŜGd2)] and probably weak antiferromagnetic LnIII∙∙∙LnIII exchange interactions in 2–4. Ac susceptibility measurements in zero dc field do not show frequency dependent out-of-phase signals, and this experimental fact is discussed for 3 in terms of the magnetic anisotropy axis for each DyIII center and the oblate electron density of this metal ion. Complexes 3 and 4 are Single-Molecule Magnets (SMMs) and this behavior is optimally observed under external dc fields of 600 and 1000 Oe, respectively. The magnetization relaxation pathways are discussed and a satisfactory fit of the temperature and field dependencies of the relaxation time τ was achieved considering a model that employs Raman, direct, and Orbach relaxation mechanisms.

scholarly journals Exchange Interactions at the Origin of Slow Relaxation of the Magnetization in {TbCu3} and {DyCu3} Single-Molecule Magnets

2014 ◽  
Vol 53 (17) ◽  
pp. 8970-8978 ◽  
Author(s):  
Fraser J. Kettles ◽  
Victoria A. Milway ◽  
Floriana Tuna ◽  
Rafael Valiente ◽  
Lynne H. Thomas ◽  
...  
Keyword(s):  
Single Molecule ◽  
Exchange Interactions ◽  
Slow Relaxation ◽  
Single Molecule Magnets

Enhancing the Blocking Temperature in Single-Molecule Magnets by Incorporating 3d-5d Exchange Interactions

2010 ◽  
Vol 16 (45) ◽  
pp. 13458-13464 ◽  
Author(s):  
Kasper S. Pedersen ◽  
Magnus Schau-Magnussen ◽  
Jesper Bendix ◽  
Høgni Weihe ◽  
Andrei V. Palii ◽  
...  
Keyword(s):  
Single Molecule ◽  
Exchange Interactions ◽  
Blocking Temperature ◽  
Single Molecule Magnets

scholarly journals Some new trends in the design of single molecule magnets

2017 ◽  
Vol 89 (8) ◽  
pp. 1119-1143 ◽  
Author(s):  
Sergey M. Aldoshin ◽  
Denis V. Korchagin ◽  
Andrew V. Palii ◽  
Boris S. Tsukerblat
Keyword(s):  
Magnetic Anisotropy ◽  
Metal Ions ◽  
Single Molecule ◽  
Exchange Interactions ◽  
Structural Factors ◽  
Single Molecule Magnets ◽  
Crystal Fields ◽  
Angular Momenta ◽  
Isotropic Exchange

AbstractIn this review we briefly discuss some new trends in the design of single molecule magnets based on transition (3d, 4d, 5d) and rare-earth (4f) metal ions. Within this broad theme the emphasis of the present review is placed on the molecules which exhibit strong magnetic anisotropy originating from the unquenched orbital angular momenta in the ground orbitally degenerate (or quasi-degenerate) states. Along with the general concepts we consider selected examples of the systems comprising orbitally-degenerate metal ions and demonstrate how one can benefit from strong single-ion anisotropy arising from the first-order orbital angular momentum. The role of crystal fields, spin-orbit coupling and structural factors is discussed. Some observation stemming from the analysis of the isotropic exchange interactions, magnetic anisotropy and strongly anisotropic orbitally-dependent superexchange are summarized as guiding rules for the controlled design of single molecule magnets exhibiting high barriers for magnetization reversal and, consequently, high blocking temperatures.

scholarly journals Smart Ligands for Efficient 3d-, 4d- and 5d-Metal Single-Molecule Magnets and Single-Ion Magnets

Inorganics ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 39 ◽  
Author(s):  
Panagiota S. Perlepe ◽  
Diamantoula Maniaki ◽  
Evangelos Pilichos ◽  
Eugenia Katsoulakou ◽  
Spyros P. Perlepes
Keyword(s):  
Metal Ions ◽  
Electron Density ◽  
Single Molecule ◽  
Metal Ion ◽  
Decisive Role ◽  
Exchange Interactions ◽  
Antiferromagnetic Coupling ◽  
Single Molecule Magnets ◽  
Crystal Fields ◽  
Interdisciplinary Field

There has been a renaissance in the interdisciplinary field of Molecular Magnetism since ~2000, due to the discovery of the impressive properties and potential applications of d- and f-metal Single-Molecule Magnets (SMMs) and Single-Ion Magnets (SIMs) or Monometallic Single-Molecule Magnets. One of the consequences of this discovery has been an explosive growth in synthetic molecular inorganic and organometallic chemistry. In SMM and SIM chemistry, inorganic and organic ligands play a decisive role, sometimes equally important to that of the magnetic metal ion(s). In SMM chemistry, bridging ligands that propagate strong ferromagnetic exchange interactions between the metal ions resulting in large spin ground states, well isolated from excited states, are preferable; however, antiferromagnetic coupling can also lead to SMM behavior. In SIM chemistry, ligands that create a strong axial crystal field are highly desirable for metal ions with oblate electron density, e.g., TbIII and DyIII, whereas equatorial crystal fields lead to SMM behavior in complexes based on metal ions with prolate electron density, e.g., ErIII. In this review, we have attempted to highlight the use of few, efficient ligands in the chemistry of transition-metal SMMs and SIMs, through selected examples. The content of the review is purely chemical and it is assumed that the reader has a good knowledge of synthetic, structural and physical inorganic chemistry, as well as of the properties of SIMs and SMMs and the techniques of their study. The ligands that will be discussed are the azide ion, the cyanido group, the tris(trimethylsilyl)methanide, the cyclopentanienido group, soft (based on the Hard-Soft Acid-Base model) ligands, metallacrowns combined with click chemistry, deprotonated aliphatic diols, and the family of 2-pyridyl ketoximes, including some of its elaborate derivatives. The rationale behind the selection of the ligands will be emphasized.

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
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