Symmetry and Geometry, Key Parameters in 3d and 4f Molecular Magnetism

A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Molecular Magnetism".

Deadline for manuscript submissions: closed (10 January 2024) | Viewed by 5120

Special Issue Editors


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Departamento de Matemáticas y Ciencias de la Ingeniería (DMCI), Facultad de Ingeniería, Ciencia y Tecnología (FICyT), Universidad Bernardo O’Higgins (UBO), Santiago 8370993, Chile
Interests: lanthanide coordination chemistry; molecular magnetism; single Ion magnets; magnetic nanomaterials; luminescent materials; DFT calculations

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Guest Editor
1. Molecular Magnetism and Molecular Materials Laboratory - LM4 (@Lm4Usach). Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Universidad de Santiago de Chile (USACH), Santiago, Chile
2. Faculty of Chemistry and Biology, Universidad de Santiago de Chile (USACH), Santiago, Chile
Interests: molecular magnetism; mixed valence; polyoxometalates (POMs); molecular and nanostructural materials

Special Issue Information

Dear Colleagues,

In molecular magnetism, 3d and/or 4f complexes are usually associated with a specific geometry, which is then linked to a particular symmetry. The definition of correct geometry has been an important aspect of molecular magnetism, since the arrangement of ligands in a given geometry determines their magnetic properties. For polynuclear systems, the experimental data have shown that adequate geometry of the 3d ion, together with geometrical distortions of the bridging ligands, affects the magnetic overlap and therefore superexchange interactions, as reflected by Kahn–Briat theory. An interesting system is that of triangular 3d complexes, whose magnetic properties can change depending on their geometrical arrangements and, moreover, anisotropic effects appear at low temperature due to existence of distortions in C3 symmetry. Moreover, the discovery by Gatteschi et al. of single molecule magnets (SMMs) with the Mn12 complex revolutionized the molecular magnetism community. These SMMs present slow relaxation of the magnetization, and this is the origin of the anisotropy found to exist in MnIII ions due to Jahn–Teller distortion. 

Almost 10 years later, Ishikawa et al. presented the existence of coordination compounds based on a single 4f ion, which also present slow relaxation of magnetization. These are the so-called single ion magnets (SIMs) based on lanthanides (Ln), which can be defined as the second generation of this type of magnetic materials. The slow magnetic relaxation is due to the anisotropy of the 4f orbitals, and the relaxation mechanisms are defined by thermal processes (Orbach, Raman, and direct) and by quantum phenomena (quantum tunnelling of magnetization (QTM)), which is thermally independent. For these types of complexes, geometry (and, therefore, symmetry) plays a key role in the design of high performance LnIII-SIMs, since changes in the geometry of LnIII ions will modify their crystal field parameters and thereby influence the dynamic magnetic properties. In this sense, heptacoordinated DyIII systems with pentagonal bipyramidal geometry (D5h symmetry) with negatively charged ligands in the axial positions present the highest energy barriers reported in the literature. By comparison, octacoordinated complexes can present large Ueff values, but not as high as the ones reported for pentagonal bipyramidal geometry complexes. This clearly shows that geometry and therefore symmetry play a key role in the magnetic properties of these types of materials.

This Special Issue of Magnetochemistry aims to publish a collection of research contributions highlighting the recent achievements in the relation of geometry and symmetry with the magnetic properties of 3d and/or 4f complexes. 

Dr. Walter Alberto Cañón Mancisidor
Prof. Dr. Diego Venegas Yazigi
Guest Editors

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Keywords

  • molecular magnetism
  • 3d complexes
  • 4f complexes
  • single molecule magnets (SMMs)
  • single ion magnets (SIMs)

Published Papers (3 papers)

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Research

14 pages, 3227 KiB  
Article
Novel Linear Trinuclear CuII Compound with Trapped Chiral Hemiaminal Ligand: Magnetostructural Study
by Carlos Cruz, Nathalie Audebrand, Dayán Páez-Hernández and Verónica Paredes-García
Magnetochemistry 2023, 9(7), 175; https://doi.org/10.3390/magnetochemistry9070175 - 06 Jul 2023
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Abstract
A new trinuclear CuII compound {[Cu3(HL′)2(H2O)2](ClO4)4}·(H2O)4 (1) was obtained and presented a trapped chiral hemiaminal (HL2′ = [(5-amino-4H-1,2,4-triazol-3-yl)amino](1H-imidazol-4-yl)methanol)). Compound 1 shows an almost flat [...] Read more.
A new trinuclear CuII compound {[Cu3(HL′)2(H2O)2](ClO4)4}·(H2O)4 (1) was obtained and presented a trapped chiral hemiaminal (HL2′ = [(5-amino-4H-1,2,4-triazol-3-yl)amino](1H-imidazol-4-yl)methanol)). Compound 1 shows an almost flat cationic structure [Cu3(HL′)2(H2O)2]4+ with a Cu3 linear core reached by the double Cu-OR/NN-Cu triazole/alkoxo bridge of the hemiaminal molecule. The CuII spin carriers are antiferromagnetically coupled, presenting a spin doublet ground state (S = 1/2) with a magnetic coupling constant of −179 cm−1. Moreover, DTF calculations show that the planarity of the compound permits a sigma-type overlapping between the unpaired electrons of the spin carriers and the p-type orbitals of the coordinated N and O atoms producing an electronic delocalization through the bridging ligand responsible for the strong antiferromagnetic interactions observed experimentally. Full article
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16 pages, 2583 KiB  
Article
Spin Frustrated Pyrazolato Triangular CuII Complex: Structure and Magnetic Properties, an Overview
by Walter Cañón-Mancisidor, Patricio Hermosilla-Ibáñez, Evgenia Spodine, Verónica Paredes-García, Carlos J. Gómez-García and Diego Venegas-Yazigi
Magnetochemistry 2023, 9(6), 155; https://doi.org/10.3390/magnetochemistry9060155 - 11 Jun 2023
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Abstract
The synthesis and structural characterization of a new triangular Cu3–μ3OH pyrazolato complex of formula, [Cu33−OH)(pz)3(Hpz)3][BF4]2 (1−Cu3), Hpz = pyrazole, is presented. The triangular unit forms [...] Read more.
The synthesis and structural characterization of a new triangular Cu3–μ3OH pyrazolato complex of formula, [Cu33−OH)(pz)3(Hpz)3][BF4]2 (1−Cu3), Hpz = pyrazole, is presented. The triangular unit forms a quasi-isosceles triangle with Cu–Cu distances of 3.3739(9), 3.3571(9), and 3.370(1) Å. This complex is isostructural to the hexanuclear complex [Cu33−OH)(pz)3(Hpz)3](ClO4)2]2 (QOPJIP). A comparative structural analysis with other reported triangular Cu3–μ3OH pyrazolato complexes has been carried out, showing that, depending on the pyrazolato derivative, an auxiliary ligand or counter-anion can affect the nuclearity and/or the dimensionality of the system. The magnetic properties of 1−Cu3 are analyzed using experimental data and DFT calculation. A detailed analysis was performed on the magnetic properties, comparing experimental and theoretical data of other molecular triangular Cu3–μ3OH complexes, showing that the displacement of the μ3−OH from the Cu3 plane, together with the type of organic ligands, influences the nature of the magnetic exchange interaction between the spin-carrier centers, since it affects the overlap of the magnetic orbitals involved in the exchange pathways. Finally, a detailed comparison of the magnetic properties of 1−Cu3 and QOPJIP was carried out, which allowed us to understand the differences in their magnetic properties. Full article
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12 pages, 3039 KiB  
Article
A 3D Coordination Polymer Based on Syn-Anti Bridged [Mn(RCOO)2]n Chains Showing Spin-Canting with High Coercivity and an Ordering Temperature of 14 K
by Soumen Kumar Dubey, Maxcimilan Patra, Kajal Gupta, Subham Bhattacharjee, Rajat Saha and Carlos J. Gómez-García
Magnetochemistry 2023, 9(2), 55; https://doi.org/10.3390/magnetochemistry9020055 - 10 Feb 2023
Cited by 1 | Viewed by 1465
Abstract
A new 3D manganese(II) coordination polymer, formulated as [Mn3(HL)6] (1) (where H2L = 6-hydroxypicolinic acid), has been hydrothermally synthesized and characterized by single-crystal X-ray crystallographic analysis along with other spectroscopic and magnetic techniques. Structural analysis [...] Read more.
A new 3D manganese(II) coordination polymer, formulated as [Mn3(HL)6] (1) (where H2L = 6-hydroxypicolinic acid), has been hydrothermally synthesized and characterized by single-crystal X-ray crystallographic analysis along with other spectroscopic and magnetic techniques. Structural analysis shows that the compound crystallizes in the monoclinic C2/c space group and is a non-porous 3D coordination polymer formed by three different Mn(II) centres connected by 6-hydroxypicolinic acid ligands in their keto form. Each Mn(II) centre shows a distorted octahedral coordination environment. Neighbouring Mn(II) centres are connected by two different syn-anti bridging carboxylate groups to form regular coordination chains. There are two different [Mn2(RCOO)2] units along the chain, formed by two crystallographically independent Mn centres (Mn1 and Mn2). These chains are further connected by HL ligands to form a 3D coordination network. Interestingly, both the hydroxy and the carboxylate groups of the ligands are deprotonated and coordinated to the metal centres, whereas the pyridyl group is protonated and uncoordinated, although it participates in strong hydrogen bonding interactions with oxygen atoms of the HL ligand, as shown by the Hirshfeld surface analysis. Both the absorption and emission spectra of the compound have also been measured. Variable temperature magnetic studies reveal the presence of a spin-canted antiferromagnetic behaviour with a high coercivity of 40 mT at 2 K and an ordering temperature of 14 K. Full article
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