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 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 High-Coordinate Mononuclear Ln(III) Complexes: Synthetic Strategies and Magnetic Properties

2020 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Joydev Acharya ◽  
Pankaj Kalita ◽  
Vadapalli Chandrasekhar
Keyword(s):  
Magnetic Properties ◽  
Single Molecule ◽  
Fine Tuning ◽  
Coordination Geometry ◽  
Single Molecule Magnets ◽  
Magnetization Relaxation ◽  
Quantum Tunneling Of Magnetization ◽  
Structural Correlation ◽  
High Coordination Number ◽  
High Coordination

Single-molecule magnets involving monometallic 4f complexes have been investigated extensively in last two decades to understand the factors that govern the slow magnetization relaxation behavior in these complexes and to establish a magneto-structural correlation. The prime goal in this direction is to suppress the temperature independent quantum tunneling of magnetization (QTM) effect via fine-tuning the coordination geometry/microenvironment. Among the various coordination geometries that have been pursued, complexes containing high coordination number around Ln(III) are sparse. Herein, we present a summary of the various synthetic strategies that were used for the assembly of 10- and 12-coordinated Ln(III) complexes. The magnetic properties of such complexes are also described.

Single-Molecule Magnets:  Two-Electron Reduced Version of a Mn12Complex and Environmental Influences on the Magnetization Relaxation of (PPh4)2[Mn12O12(O2CCHCl2)16(H2O)4]

2003 ◽  
Vol 125 (12) ◽  
pp. 3576-3588 ◽  
Author(s):  
Monica Soler ◽  
Wolfgang Wernsdorfer ◽  
Khalil A. Abboud ◽  
John C. Huffman ◽  
Ernest R. Davidson ◽  
...  
Keyword(s):  
Single Molecule ◽  
Environmental Influences ◽  
Single Molecule Magnets ◽  
Magnetization Relaxation

scholarly journals Leveraging Surface Siloxide Electronics to Enhance Relaxation Properties of a Single-Molecule Magnet

2020 ◽  
Author(s):  
Maciej Korzynski ◽  
Zachariah Berkson ◽  
Boris Le Guennic ◽  
Olivier Cador ◽  
Christophe Copéret
Keyword(s):  
Single Molecule ◽  
Relaxation Times ◽  
Device Fabrication ◽  
Information Storage ◽  
Commercial Application ◽  
Surface Immobilization ◽  
Single Molecule Magnets ◽  
Magnetization Relaxation ◽  
Surface Deposition ◽  
Magnitude Increase

Single-molecule magnets (SMMs) hold promise for unmatched information storage density as well as applications in quantum computing and spintronics. To date, the most successful SMMs are organometallic lanthanide complexes. However, their surface immobilization, one of the requirements for device fabrication and commercial application, remains challenging due to sensitivity of magnetic properties to small changes in the electronic structure of the parent SMM. Thus, finding controlled approaches to SMM surface deposition is a timely challenge. In this contribution we apply the concept of isolobality to identify siloxides present at the surface of partially dehydroxylated silica as a suitable replacement for archetypal ligand architectures in organometallic SMMs. We demonstrate theoretically and experimentally that isolated siloxide anchorages not only enable successful immobilization, but also lead to two-orders-of-magnitude increase in magnetization relaxation times and provide magnetic site dilution.

scholarly journals 3d single-ion magnets

2015 ◽  
Vol 44 (8) ◽  
pp. 2135-2147 ◽  
Author(s):  
Gavin A. Craig ◽  
Mark Murrie
Keyword(s):  
Magnetic Properties ◽  
Transition Metal ◽  
Single Molecule ◽  
Metal Ion ◽  
Ligand Field ◽  
Single Molecule Magnets ◽  
Transition Metal Ion ◽  
Recent Approach

This review describes the recent approach to obtain single-molecule magnets where the magnetic properties arise from just one first row transition metal ion in a suitable ligand field.

Heterometallic 3d–4f Single-Molecule Magnets: Ligand and Metal Ion Influences on the Magnetic Relaxation

2015 ◽  
Vol 54 (7) ◽  
pp. 3631-3642 ◽  
Author(s):  
Stuart K. Langley ◽  
Crystal Le ◽  
Liviu Ungur ◽  
Boujemaa Moubaraki ◽  
Brendan F. Abrahams ◽  
...  
Keyword(s):  
Single Molecule ◽  
Magnetic Relaxation ◽  
Metal Ion ◽  
Single Molecule Magnets

Magnetic Exchange Effects in {CrIII2DyIII2} Single Molecule Magnets Containing Alcoholamine Ligands

2014 ◽  
Vol 67 (11) ◽  
pp. 1581 ◽  
Author(s):  
Stuart K. Langley ◽  
Daniel P. Wielechowski ◽  
Boujemaa Moubaraki ◽  
Brendan F. Abrahams ◽  
Keith S. Murray
Keyword(s):  
Single Molecule ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Magnetic Studies ◽  
Single Molecule Magnets ◽  
Magnetic Exchange ◽  
Bridging Ligands ◽  
Metallic Core ◽  
Ligand Coordination ◽  
Magnetic Hysteresis Loops

The synthesis and magnetic characterisation of four new heterometallic {CrIII2DyIII2} complexes 2–5 are described. The present work follows on from a recently isolated complex [CrIII2DyIII2(OMe)2(O2CPh)4(mdea)2(NO3)2] (1) (mdeaH2 = N-methyldiethanolamine), which displayed impressive single molecule magnet (SMM) properties, notably highly coercive magnetic hysteresis loops below 3.5 K. Compounds 1–5 all display a planar butterfly type metallic core arrangement, with the DyIII ions occupying the central body positions and the CrIII ion the outer wing positions. The core is stabilized by the amine–diolate, and carboxylate bridging ligands. Variation of the amine–diolate ligand resulted in several structural analogues which maintain the same metallic core, but differ from the parent 1 in the outer ligand coordination environment. Magnetic studies reveal complexes 2–5 also display SMM behaviour, unambiguously confirmed via low temperature magnetic hysteresis loops, each displaying wide coercive fields, a rare occurrence for lanthanoid-based SMMs.

scholarly journals Bis-cyclooctatetraenyl Thulium(II): Highly Reducing Lanthanide Sandwich Single Molecule Magnets

2020 ◽  
Author(s):  
Jules Moutet ◽  
jules Schleinitz ◽  
Leo La Droitte ◽  
Maxime Tricoire ◽  
Frédéric Gendron ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Single Molecule ◽  
Single Electron Transfer ◽  
Small Molecule Activation ◽  
Sandwich Complex ◽  
Magnetic Studies ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Divalent Lanthanide ◽  
Reliable Basis

Divalent lanthanide organometallics are well known highly reducing compounds usually used for single electron transfer reactivity and small molecule activation. Thus, their very reactive nature prevented for many years the study of their physical properties, such as magnetic studies on a reliable basis. In this article, the access to rare organometallic sandwich compounds of Tm<sup>II</sup> with the cyclooctatetraenyl (Cot) ligand impacts on the use of divalent organolanthanide compounds as an additional strategy for the design of performing Single Molecule Magnets (SMM). Herein, the first divalent thulium sandwich complex with f<sup>13</sup> configuration behaving as a Single Molecule Magnet in absence of DC field is highlighted.

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