Special Issue "Transition Metal Magnetism"

A special issue of Magnetochemistry (ISSN 2312-7481).

Deadline for manuscript submissions: closed (28 February 2018).

Special Issue Editor

Guest Editor
Prof. Dr. Coen De Graaf

Affiliation: ICREA (Catalan Institution for Research and Advanced Studies), Dept. Physical and Inorganic Chemistry, Universitat Rovira i Virgili, Marcel•lí Domingo, s/n, 43007 Tarragona, Spain
Website | E-Mail
Interests: light-induced spin crossover; magnetic anisotropy; wave function analysis; magnetic coupling; Effective Hamiltonians; extended metal atom chains; highly correlated materials

Special Issue Information

Dear Colleagues,

Despite the very long-standing history of magnetic interactions in transition metal (TM) compounds—the magnetic susceptibility curve of the copper acetate complex was published more than sixty years ago—the research field remains as lively as ever. Interest have changed over the years, but the strong interaction of experiment and theory still makes possible to advance in our understanding of the exciting properties of the transition metal complexes with unpaired electrons.

Among the topics that have gained importance in the last years one can highlight the multiferroic properties of certain TM oxides, where the interplay of magnetic interactions and electric polarization can give rise to unexpected properties. Other recent discoveries in solid state materials with TM ions comprise the superconductivity in iron pnictides and the subtle interplay of isotropic exchange and spin-orbit interaction in 4d and 5d oxides, such as the iridates.

In the early days of single molecular magnetism, a great deal of effort has been invested in designing large polynuclear 3d transition metal complexes to maximize the total spin moment. Nowadays, attention has shifted to the lanthanides because of their intrinsic larger magnetic anisotropy. However, large anisotropy can also be attained in TM-3d complexes by using rigid polydentate ligands to avoid the quenching of the orbital angular moment. Complexes with a lanthanide and a TM-3d ion are also interesting candidates to combine large magnetic moments with large magnetic anisotropy.

Another topic of interest concerns the light induced magnetism in spin crossover complexes. The ultrafast relaxation of the excited state is not easily followed in experiment and theory is also having a hard time to give an accurate description of the process. Magnetic exchange interactions are traditionally studied in complexes with unpaired electrons in the 3d orbitals, but recently these interactions have also been subject of study in second and third row TM complexes. Furthermore, the incorporation of TM metal-organic frameworks (MOFs) and graphene sheets can also serve as examples of the continuing interest of the magnetism in systems due to presence of transition metals.

Prof. Dr. Coen de Graaf
Guest Editor

Manuscript Submission Information

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Keywords

  • multiferroics
  • spin-orbit coupling
  • magnetic anisotropy
  • spin crossover
  • light-induced magnetism
  • 3d-4f coupling
  • transition metals in MOFs
  • TM doping in graphene
  • TM-4d and 5d interactions

Published Papers (5 papers)

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Research

Open AccessArticle
Magnetic Characterization of Chromium Intermediates in the Reduction of Chromium (VI) by Glutathione in Acidic Solutions
Magnetochemistry 2018, 4(2), 23; https://doi.org/10.3390/magnetochemistry4020023
Received: 26 April 2017 / Revised: 2 May 2018 / Accepted: 3 May 2018 / Published: 17 May 2018
Cited by 1 | PDF Full-text (957 KB) | HTML Full-text | XML Full-text
Abstract
Chromium (VI) is carcinogenic through intermediates formed in the cellular milieu by reduction with small reductants like glutathione (GSH), ascorbate, cysteine, and NADPH. Although the reduction of chromate by thiols has been investigated, the participation of Cr(IV) intermediates has been inferred only indirectly [...] Read more.
Chromium (VI) is carcinogenic through intermediates formed in the cellular milieu by reduction with small reductants like glutathione (GSH), ascorbate, cysteine, and NADPH. Although the reduction of chromate by thiols has been investigated, the participation of Cr(IV) intermediates has been inferred only indirectly due to the Cr(IV) refractive behavior towards EPR spectroscopy. Biological data from numerous reports indicate that Cr(IV) is the species most likely responsible for the carcinogenicity of Cr(VI). Our kinetic studies suggested that in acidic solutions, glycine buffer at pH 2.8, the reduction of chromate with GSH involves mostly a chromium(IV) intermediate. As a step towards the full characterization of the paramagnetic species involved in the reduction of chromate by thiols at neutral pH, we embarked on an investigation of the reduction of chromate with GSH in glycine buffer at pH 2.8 using a Superconducting QUantum Interference Device (SQUID) magnetometer. Our results indicate a strong influence of temperature and confirm the presence of Cr(IV). At 2 K, the saturation magnetization method was applied to the frozen reaction when it reached the peak of formation of intermediates and the contributions were calculated to be 30% of Cr(IV) and 69% of Cr(V). When the Curie–Weiss method was applied to determine the effective magnetic moment, the use of the linear portion of the curve, 100–200 K, yielded 58% Cr(IV) and 42% Cr(V); when data from the region below the temperature of liquid N2 (77 K) is employed, the intermediate is exclusively Cr(IV). Full article
(This article belongs to the Special Issue Transition Metal Magnetism)
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Open AccessArticle
The Role of Self-Interaction Corrections, Vibrations, and Spin-Orbit in Determining the Ground Spin State in a Simple Heme
Magnetochemistry 2017, 3(4), 31; https://doi.org/10.3390/magnetochemistry3040031
Received: 14 September 2017 / Revised: 10 October 2017 / Accepted: 12 October 2017 / Published: 17 October 2017
Cited by 4 | PDF Full-text (536 KB) | HTML Full-text | XML Full-text
Abstract
Without self-interaction corrections or the use of hybrid functionals, approximations to the density-functional theory (DFT) often favor intermediate spin systems over high-spin systems. In this paper, we apply the recently proposed Fermi–Löwdin-orbital self-interaction corrected density functional formalism to a simple tetra-coordinated Fe(II)-porphyrin molecule [...] Read more.
Without self-interaction corrections or the use of hybrid functionals, approximations to the density-functional theory (DFT) often favor intermediate spin systems over high-spin systems. In this paper, we apply the recently proposed Fermi–Löwdin-orbital self-interaction corrected density functional formalism to a simple tetra-coordinated Fe(II)-porphyrin molecule and show that the energetic orderings of the S = 1 and S = 2 spin states are changed qualitatively relative to the results of Generalized Gradient Approximation (developed by Perdew, Burke, and Ernzerhof, PBE-GGA) and Local Density Approximation (developed by Perdew and Wang, PW92-LDA). Because the energetics, associated with changes in total spin, are small, we have also calculated the second-order spin–orbit energies and the zero-point vibrational energies to determine whether such corrections could be important in metal-substituted porphins. Our results find that the size of the spin–orbit and vibrational corrections to the energy orderings are small compared to the changes due to the self-interaction correction. Spin dependencies in the Infrared (IR)/Raman spectra and the zero-field splittings are provided as a possible means for identifying the spin in porphyrins containing Fe(II). Full article
(This article belongs to the Special Issue Transition Metal Magnetism)
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Open AccessArticle
Mapping the Magnetic Anisotropy inside a Ni4 Cubane Spin Cluster Using Polarized Neutron Diffraction
Magnetochemistry 2017, 3(3), 25; https://doi.org/10.3390/magnetochemistry3030025
Received: 24 April 2017 / Revised: 1 June 2017 / Accepted: 3 July 2017 / Published: 13 July 2017
Cited by 1 | PDF Full-text (3928 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this publication, we report on the study of the magnetic anisotropy of the cubane type tetranuclear cluster of Ni(II), [Ni4(L)4(MeOH)4] (H2L = salicylidene-2-ethanolamine; MeOH = methanol), by the means of angular-resolved magnetometry and polarized [...] Read more.
In this publication, we report on the study of the magnetic anisotropy of the cubane type tetranuclear cluster of Ni(II), [Ni4(L)4(MeOH)4] (H2L = salicylidene-2-ethanolamine; MeOH = methanol), by the means of angular-resolved magnetometry and polarized neutron diffraction (PND). We show that better than other usual characterization techniques—such as electron paramagnetic resonance spectroscopy (EPR) or SQUID magnetometry—only PND enables the full determination of the local magnetic susceptibility tensor of the tetranuclear cluster and those of the individual Ni(II) ions and the antiferromagnetic pairs they form. This allows highlighting that, among the two antiferromagnetic pairs in the cluster, one has a stronger easy-axis type anisotropy. This distinctive feature can only be revealed by PND measurements, stressing the remarkable insights that they can bring to the understanding of the magnetic properties of transition metals clusters. Full article
(This article belongs to the Special Issue Transition Metal Magnetism)
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Open AccessArticle
Neutral Low-Dimensional Assemblies of a Mn(III) Schiff Base Complex and Octacyanotungstate(V): Synthesis, Characterization, and Magnetic Properties
Magnetochemistry 2017, 3(2), 16; https://doi.org/10.3390/magnetochemistry3020016
Received: 1 February 2017 / Revised: 13 March 2017 / Accepted: 17 March 2017 / Published: 24 March 2017
Cited by 4 | PDF Full-text (2747 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two novel low-dimensional molecular magnetic materials were prepared by the self-assembly of 3d- and 5d-metal complexes. These are the first neutral heterobimetallic cyanobridged compounds involving one anisotropic Mn(III) Schiff base complex and one octacyanotungstate(V) per molecular unit. A slow diffusion of the constituents’ [...] Read more.
Two novel low-dimensional molecular magnetic materials were prepared by the self-assembly of 3d- and 5d-metal complexes. These are the first neutral heterobimetallic cyanobridged compounds involving one anisotropic Mn(III) Schiff base complex and one octacyanotungstate(V) per molecular unit. A slow diffusion of the constituents’ solutions leads to the formation of the 0D crystalline complex 1, due to coordination of a water molecule to the Mn center, which prevents polymer formation. A rapid mixing of reagents results in the precipitation of the microcrystalline powder of complex 2, which based on the totality of experimental data, possesses a 1D polymeric structure. The magnetic studies have shown that antiferromagnetic exchange interactions prevail in 1 (J/kB = −13.1(7) K, D = −3.0(1.3) K, zJ' = −0.16(20) K and gav = 2.00(1)); while the presence of the significant intramolecular Mn(III)–W(V) ferromagnetic coupling through cyanide bridge is characteristic for 2 (J/kB = 46.1(5) K, gMn = 2.11(3), fixed gW = 2.0). Due to the weak interchain interactions, zJ′/kB = −0.8(2) K, and compound 2 is a metamagnet with the Néel temperature of 9.5 K undergoing a spin-flip transition at 2 kOe. The slow magnetization dynamics of 2 were investigated at a DC field of 0 and 2 kOe, giving the values of τ0 32(15) and 36(15) ps, respectively, well within the range typical for single-chain magnets (SCMs). The respective ∆τ/kB values were 48.4(1.2) and 44.9(1.0) K. Full article
(This article belongs to the Special Issue Transition Metal Magnetism)
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Open AccessFeature PaperCommunication
Synthesis, Characterization and Copper(2+) Coordination Chemistry of a Polytopic Paramagnetic Ligand
Magnetochemistry 2017, 3(1), 15; https://doi.org/10.3390/magnetochemistry3010015
Received: 28 October 2016 / Revised: 26 January 2017 / Accepted: 7 February 2017 / Published: 14 March 2017
PDF Full-text (2123 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We describe the synthesis of a new tetratopic phenoxyl radical ligand based on the previously reported ditopic “baqp” radical. The tetratopic ligand is prepared in five steps from 4-tert-butylphenol. Coordination of the ligand with Cu(OAc)2 produced a tetranuclear complex with [...] Read more.
We describe the synthesis of a new tetratopic phenoxyl radical ligand based on the previously reported ditopic “baqp” radical. The tetratopic ligand is prepared in five steps from 4-tert-butylphenol. Coordination of the ligand with Cu(OAc)2 produced a tetranuclear complex with an S = ½ ground state featuring a coordinated hexa-anion radical with very strong intramolecular antiferromagnetic exchange coupling. Full article
(This article belongs to the Special Issue Transition Metal Magnetism)
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