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Frontiers in Molecule-Based Magnets
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Frontiers in Molecule-Based Magnets

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Physical Chemistry".

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 10717

Special Issue Editor

Dr. Constantina Papatriantafyllopoulou

E-Mail Website
Guest Editor
School of Chemistry, National University of Ireland Galway, Galway, Ireland
Interests: magnetic sensors; single-molecule magnets; multifunctional materials; metal–organic frameworks; drug carriers
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Molecule-based magnets have witnessed an enormous development over the past few decades due to an intense focus on the discovery of new materials and phenomena and the need for a deeper understanding of the origin of their properties. It is an interdisciplinary field that combines several categories of fascinating species, including single molecule/chain/ion magnets, ferromagnets, spin crossover systems, thermal/photo/pressure-induced magnetic switches, spintronics, etc., which have the potential to be used in a wide range of technological and biomedical applications. This Special Issue aims to present research that spans the entire landscape of molecule-based magnets and identify and review the recent developments and breakthroughs in this field.

Dr. Constantina Papatriantafyllopoulou
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Single-molecule magnets
  • Ferromagnets
  • Single-chain magnets
  • Spin crossover
  • Single ion magnets
  • Magnetocaloric effect

Published Papers (4 papers)

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Research

14 pages, 2347 KiB  
Article
Novel Co5 and Ni4 Metal Complexes and Ferromagnets by the Combination of 2-Pyridyl Oximes with Polycarboxylic Ligands
by Foteini Dimakopoulou, Costantinos G. Efthymiou, Ciaran O’Malley, Andreas Kourtellaris, Eleni Moushi, Anastasios Tasiopooulos, Spyros P. Perlepes, Patrick McArdle, Ernesto Costa-Villén, Julia Mayans and Constantina Papatriantafyllopoulou
Molecules 2022, 27(15), 4701; https://doi.org/10.3390/molecules27154701 - 22 Jul 2022
Cited by 1 | Viewed by 1446
Abstract
The use of 2-pyridyl oximes in metal complexes chemistry has been extensively investigated in the last few decades as a fruitful source of species with interesting magnetic properties. In this work, the initial combination of pyridine-2-amidoxime (pyaoxH2) and 2-methyl pyridyl ketoxime [...] Read more.
The use of 2-pyridyl oximes in metal complexes chemistry has been extensively investigated in the last few decades as a fruitful source of species with interesting magnetic properties. In this work, the initial combination of pyridine-2-amidoxime (pyaoxH2) and 2-methyl pyridyl ketoxime (mpkoH) with isonicotinic acid (HINA) and 3,5-pyrazole dicarboxylic acid (H3pdc) has provided access to three new compounds, [Ni4(INA)2(pyaox)2(pyaoxH)2(DMF)2] (1), [Co5(mpko)6(mpkoH)2(OMe)2(H2O)](ClO4)6 (2), and [Co5(OH)(Hpdc)5(H2pdc)] (3). 1 displays a square-planar metal topology, being the first example that bears simultaneously HINA and pyaoxH2 in their neutral or ionic form. The neighbouring Ni4 units in 1 are held together through strong intermolecular hydrogen bonding interactions, forming a three-dimensional supramolecular framework. 2 and 3 are mixed-valent Co4IIICoII and Co2IIICoII3 compounds with a bowtie and trigonal bipyramidal metal topology, accordingly. Direct current and alternate current magnetic susceptibility studies revealed that the exchange interactions between the NiII ions in 1 are ferromagnetic (J = 1.79(4) cm−1), while 2 exhibits weak AC signals in the presence of a magnetic field. The syntheses, crystal structures, and magnetic properties of 1–3 are discussed in detail. Full article
(This article belongs to the Special Issue Frontiers in Molecule-Based Magnets)
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23 pages, 4410 KiB  
Article
Asymmetric Dinuclear Lanthanide(III) Complexes from the Use of a Ligand Derived from 2-Acetylpyridine and Picolinoylhydrazide: Synthetic, Structural and Magnetic Studies
by Diamantoula Maniaki, Panagiota S. Perlepe, Evangelos Pilichos, Sotirios Christodoulou, Mathieu Rouzières, Pierre Dechambenoit, Rodolphe Clérac and Spyros P. Perlepes
Molecules 2020, 25(14), 3153; https://doi.org/10.3390/molecules25143153 - 10 Jul 2020
Cited by 8 | Viewed by 3282
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Frontiers in Molecule-Based Magnets)
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16 pages, 2636 KiB  
Article
Trinuclear NiII-LnIII-NiII Complexes with Schiff Base Ligands: Synthesis, Structure, and Magnetic Properties
by Anastasia N. Georgopoulou, Michael Pissas, Vassilis Psycharis, Yiannis Sanakis and Catherine P. Raptopoulou
Molecules 2020, 25(10), 2280; https://doi.org/10.3390/molecules25102280 - 12 May 2020
Cited by 5 | Viewed by 2262
Abstract
The reaction of the Schiff base ligand o-OH-C6H4-CH=N-C(CH2OH)3, H4L, with Ni(O2CMe)2·4H2O and lanthanide nitrate salts in a 4:2:1 ratio lead to the formation of the trinuclear [...] Read more.
The reaction of the Schiff base ligand o-OH-C6H4-CH=N-C(CH2OH)3, H4L, with Ni(O2CMe)2·4H2O and lanthanide nitrate salts in a 4:2:1 ratio lead to the formation of the trinuclear complexes [Ni2Ln(H3L)4(O2CMe)2](NO3) (Ln = Sm (1), Eu (2), Gd (3), Tb (4)). The complex cations contain the strictly linear NiII-LnIII-NiII moiety. The central LnIII ion is bridged to each of the terminal NiII ions through two deprotonated phenolato groups from two different ligands. Each terminal NiII ion is bound to two ligands in distorted octahedral N2O4 environment. The central lanthanide ion is coordinated to four phenolato oxygen atoms from the four ligands, and four carboxylato oxygen atoms from two acetates which are bound in the bidentate chelate mode. The lattice structure of complex 4 consists of two interpenetrating, supramolecular diamond like lattices formed through hydrogen bonds among neighboring trinuclear clusters. The magnetic properties of 1–4 were studied. For 3 the best fit of the magnetic susceptibility and isothermal M(H) data gave JNiGd = +0.42 cm−1, D = +2.95 cm−1 with gNi = gGd = 1.98. The ferromagnetic nature of the intramolecular Ni···Gd interaction revealed ground state of total spin S = 11/2. The magnetocaloric effect (MCE) parameters for 3 show that the change of the magnetic entropy (−ΔSm) reaches a maximum of 14.2 J kg−1 K−1 at 2 K. A brief literature survey of complexes containing the NiII-LnIII-NiII moiety is discussed in terms of their structural properties. Full article
(This article belongs to the Special Issue Frontiers in Molecule-Based Magnets)
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16 pages, 3834 KiB  
Article
4f-Metal Clusters Exhibiting Slow Relaxation of Magnetization: A {Dy7} Complex with An Hourglass-like Metal Topology
by Konstantinos N. Pantelis, Panagiota S. Perlepe, Spyridon Grammatikopoulos, Christos Lampropoulos, Jinkui Tang and Theocharis C. Stamatatos
Molecules 2020, 25(9), 2191; https://doi.org/10.3390/molecules25092191 - 07 May 2020
Cited by 7 | Viewed by 2970
Abstract
The reaction between Dy(NO3)3∙6H2O and the bulky Schiff base ligand, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in the presence of the organic base NEt3 has led to crystallization and structural, spectroscopic and magnetic characterization of a [...] Read more.
The reaction between Dy(NO3)3∙6H2O and the bulky Schiff base ligand, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in the presence of the organic base NEt3 has led to crystallization and structural, spectroscopic and magnetic characterization of a new heptanuclear [Dy7(OH)6(OMe)2(NO3)1.5(nacb)2(nacbH)6(MeOH)(H2O)2](NO3)1.5 (1) compound in ~40% yield. Complex 1 has a unique hourglass-like metal topology, among all previously reported {Dy7} clusters, comprising two distorted {Dy4(μ3-OH)3(μ3-OMe)}8+ cubanes that share a common metal vertex (Dy2). Peripheral ligation about the metal core is provided by the carboxylate groups of four η1:η1:η1:μ single-deprotonated nacbH− and two η1:η1:η2:η1:μ3 fully-deprotonated nacb2− ligands. Complex 1 is the first structurally characterized 4f-metal complex bearing the chelating/bridging ligand nacbH2 at any protonation level. Magnetic susceptibility studies revealed that 1 exhibits slow relaxation of magnetization at a zero external dc field, albeit with a small energy barrier of ~5 K for the magnetization reversal, most likely due to the very fast quantum-tunneling process. The combined results are a promising start to further explore the reactivity of nacbH2 upon all lanthanide ions and the systematic use of this chelate ligand as a route to new 4f-metal cluster compounds with beautiful structures and interesting magnetic dynamics. Full article
(This article belongs to the Special Issue Frontiers in Molecule-Based Magnets)
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