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Special Issue "Advances in Molecular Magnets and related Phenomena"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (15 December 2016)

Special Issue Editor

Guest Editor
Prof. Dr. Wolfgang Linert

Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-AC, A-1060 Wien, Austria
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Fax: +43 1588 01916 3613
Interests: Transition metal chemistry, molecular magnesium, spin crossover, coordination chemistry related bioinorganic chemistry, redox-kinetics

Special Issue Information

Dear Colleagues,

Molecular magnets, spin-crossover compounds, molecular photomagnetism, among others, are interdisciplinary research fields, bringing the knowledge of chemists, physicists and material sciences together. Although this area has been investigated for decades, the last few years have seen advances due to the preparation of new areas (for example multifunctional molecular magnets), the involvement and combination of new experimental techniques (for example advances in temperature dependent Raman spectroscopy and other related methods), and advances in the direction of actual application of available substances for technological use (for example the preparation of stable thin films, showing write and readable properties for data storage).

The aim of the present Special Issue is to bring scientists from different fields together to report about their latest findings in original papers, review articles or short communications. We look forward to receiving your submissions.

Prof. Dr. Wolfgang Linert
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 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

  • magnetochemistry
  • molecular magnets
  • spin crossover
  • high spin–low spin transition
  • photomagnetism
  • cooperativity in magnetic systems

Published Papers (8 papers)

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Research

Open AccessArticle Magnetic Anisotropy and Field‐induced Slow  Relaxation of Magnetization in Tetracoordinate CoII Compound [Co(CH3‐im)2Cl2]
Materials 2017, 10(3), 249; doi:10.3390/ma10030249
Received: 13 January 2017 / Accepted: 27 February 2017 / Published: 28 February 2017
Cited by 3 | PDF Full-text (2949 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Static and dynamic magnetic properties of the tetracoordinate CoII complex [Co(CH3‐im)2Cl2], (1, CH3‐im = N‐methyl‐imidazole), studied using thorough analyses of magnetometry, and High‐Frequency and ‐Field EPR (HFEPR) measurements, are reported. The study was supported by ab initio complete active space self‐consistent field (CASSCF)
[...] Read more.
Static and dynamic magnetic properties of the tetracoordinate CoII complex [Co(CH3‐im)2Cl2], (1, CH3‐im = N‐methyl‐imidazole), studied using thorough analyses of magnetometry, and High‐Frequency and ‐Field EPR (HFEPR) measurements, are reported. The study was supported by ab initio complete active space self‐consistent field (CASSCF) calculations. It has been revealed that 1 possesses a large magnetic anisotropy with a large rhombicity (magnetometry: D = −13.5 cm−1, E/D = 0.33; HFEPR: D = −14.5(1) cm−1, E/D = 0.16(1)). These experimental results agree well with the theoretical calculations (D = −11.2 cm−1, E/D = 0.18). Furthermore, it has been revealed that 1 behaves as a field‐induced single‐ion magnet with a relatively large spin‐reversal barrier (Ueff = 33.5 K). The influence of the Cl–Co–Cl angle on magnetic anisotropy parameters was evaluated using the CASSCF calculations. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
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Open AccessFeature PaperArticle Synthesis, Crystal Structure, and Magnetic Properties of a New Mixed Metal (Co(II), Ni(II)) Cubane
Materials 2017, 10(2), 178; doi:10.3390/ma10020178
Received: 8 January 2017 / Revised: 3 February 2017 / Accepted: 4 February 2017 / Published: 14 February 2017
Cited by 2 | PDF Full-text (1688 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The mixed Co(II)/Ni(II) complex, [Co2.67Ni1.33L4(CH3COO)2][BPh4]2·0.75H2O where HL = 4-(salicylaldimine)antipyrine, was isolated as an orange solid from the reaction of 4-(salicylaldimine)antipyrine, with mixed cobalt(II) acetate and nickel(II) acetate
[...] Read more.
The mixed Co(II)/Ni(II) complex, [Co2.67Ni1.33L4(CH3COO)2][BPh4]2·0.75H2O where HL = 4-(salicylaldimine)antipyrine, was isolated as an orange solid from the reaction of 4-(salicylaldimine)antipyrine, with mixed cobalt(II) acetate and nickel(II) acetate in ethanol. The complex was characterized by Frustrated Total Internal Reflection (FTIR), UltraViolet Visible spectroscopy (UV-Vis), X-ray single crystal diffraction, and by elemental analysis. The complex is composed of two symmetry independent cationic units, A and B. The two units are essentially isostructural; nevertheless, small differences exist between them. The units contain four metal atoms, arranged at the corners of a distorted cubane-like core alternately with phenoxy oxygen of the Schiff base. The overall eight corners occupied by metal ions in the asymmetric unit are shared between cobalt and nickel in a 5.33:2.67 ratio. Each metal divalent cation binds three coordinated sites from the corresponding tridentate Schiff base ligand, the fourth one is bound by the acetate oxygen, the fifth and the sixth donor sites come from the phenolate oxygens of other Schiff base ligands. Intermolecular hydrogen bonds join the complexes to the water molecules present in the crystal packing. The magnetic characterization was carried out for this new complex and for its isostructural counterpart containing only cobalt ions. The magnetic measurements for the cobalt(II)/nickel(II) mixed compound indicate either antiferromagnetic interactions among the two cubanes or an anisotropic contribution, whereas a ferromagnetic interaction is observed within the cubane, for both the complexes, as expected by geometrical considerations. A comparison between the magnetic properties of the pure cobalt(II) derivative and similar systems discussed in literature, is presented. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
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Open AccessArticle Cooperativity of Spin Crossover Complexes: Combining Periodic Density Functional Calculations and Monte Carlo Simulation
Materials 2017, 10(2), 172; doi:10.3390/ma10020172
Received: 10 January 2017 / Accepted: 8 February 2017 / Published: 13 February 2017
PDF Full-text (3415 KB) | HTML Full-text | XML Full-text
Abstract
The total enthalpies of the 16 different spin configurations that can be realized in the unit cell of the archetype spin crossover complex [Fe(phen)2(NCS)2] (phen = 1,2-phenanthroline) were calculated, applying periodic density functional theory combined with the Hubbard model and the Grimme-D2 dispersion
[...] Read more.
The total enthalpies of the 16 different spin configurations that can be realized in the unit cell of the archetype spin crossover complex [Fe(phen)2(NCS)2] (phen = 1,2-phenanthroline) were calculated, applying periodic density functional theory combined with the Hubbard model and the Grimme-D2 dispersion correction (DFT+U+D2). The obtained enthalpy differences between the individual spin configurations were used to determine spin couplings of an Ising-like model, and subsequent Monte Carlo simulations for this model allowed the estimation of the phenomenological interaction parameter Γ of the Slichter–Drickamer model, which is commonly used to describe the cooperativity of the spin transition. The calculation procedure described here-which led to an estimate of about 3 kJ·mol-1 for Γ, in good agreement with experiment—may be used to predict from first principles how modifications of spin crossover complexes can change the character of the spin transition from gradual to abrupt and vice versa. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
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Open AccessArticle Metal-Organic Framework of Lanthanoid Dinuclear Clusters Undergoes Slow Magnetic Relaxation
Materials 2017, 10(1), 81; doi:10.3390/ma10010081
Received: 3 December 2016 / Revised: 12 January 2017 / Accepted: 16 January 2017 / Published: 20 January 2017
PDF Full-text (3497 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Lanthanoid metal-organic frameworks (Ln-MOFs) can adopt a variety of new structures due to the large coordination numbers of Ln metal ions, and Ln-MOFs are expected to show new luminescence and magnetic properties due to the localized f electrons. In particular, some Ln metal
[...] Read more.
Lanthanoid metal-organic frameworks (Ln-MOFs) can adopt a variety of new structures due to the large coordination numbers of Ln metal ions, and Ln-MOFs are expected to show new luminescence and magnetic properties due to the localized f electrons. In particular, some Ln metal ions, such as Dy(III) and Tb(III) ions, work as isolated quantum magnets when they have magnetic anisotropy. In this work, using 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic acid (H3TATB) as a ligand, two new Ln-MOFs, [Dy(TATB)(DMF)2] (1) and [Tb(TATB)(DMF)2] (2), were obtained. The Ln-MOFs contain Ln dinuclear clusters as secondary building units, and 1 underwent slow magnetic relaxation similar to single-molecule magnets. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
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Open AccessFeature PaperArticle Spray-Drying to Get Spin-Crossover Materials
Materials 2017, 10(1), 60; doi:10.3390/ma10010060
Received: 15 December 2016 / Revised: 3 January 2017 / Accepted: 5 January 2017 / Published: 11 January 2017
Cited by 1 | PDF Full-text (3612 KB) | HTML Full-text | XML Full-text
Abstract
Spin-crossover (SCO) triazole-based coordination polymers can be synthesized by micelle techniques, which almost always lead to rod-shaped nanoparticles. In order to notably reach new morphologies, we explore here the potentiality of the spray-drying (SD) method to get SCO materials. Three SCO coordination polymers
[...] Read more.
Spin-crossover (SCO) triazole-based coordination polymers can be synthesized by micelle techniques, which almost always lead to rod-shaped nanoparticles. In order to notably reach new morphologies, we explore here the potentiality of the spray-drying (SD) method to get SCO materials. Three SCO coordination polymers and a mononuclear complex are investigated. In all cases, the SD method obtains particles definitely showing SCO. The features of the latter are yet always different from those of the referenced materials, in the sense that SCO is more gradual and incomplete, in adequacy with the poor crystallinity of the powders obtained by SD. In the case of coordination polymers, the particles are preferentially spherical. Indications of possible polymorphism and/or new materials induced by the use of the SD method are evidenced. In the case of the mononuclear complex, the SD method has allowed reproducing, in a quick and easy way, the well-known bulk compound. This exploratory work demonstrates the relevance of the concept and opens the way to a systematic scrutiny of all the experimental parameters to tune the size, morphology, and properties of the SD-synthesized SCO particles. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
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Open AccessArticle Dysprosium Acetylacetonato Single-Molecule Magnet Encapsulated in Carbon Nanotubes
Materials 2017, 10(1), 7; doi:10.3390/ma10010007
Received: 25 October 2016 / Revised: 9 December 2016 / Accepted: 20 December 2016 / Published: 23 December 2016
Cited by 1 | PDF Full-text (2053 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Dy single-molecule magnets (SMMs), which have several potential uses in a variety of applications, such as quantum computing, were encapsulated in multi-walled carbon nanotubes (MWCNTs) by using a capillary method. Encapsulation was confirmed by using transmission electron microscopy (TEM). In alternating current magnetic
[...] Read more.
Dy single-molecule magnets (SMMs), which have several potential uses in a variety of applications, such as quantum computing, were encapsulated in multi-walled carbon nanotubes (MWCNTs) by using a capillary method. Encapsulation was confirmed by using transmission electron microscopy (TEM). In alternating current magnetic measurements, the magnetic susceptibilities of the Dy acetylacetonato complexes showed clear frequency dependence even inside the MWCNTs, meaning that this hybrid can be used as magnetic materials in devices. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
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Open AccessFeature PaperArticle Solvent-Induced Polymorphism of Iron(II) Spin Crossover Complexes
Materials 2016, 9(7), 585; doi:10.3390/ma9070585
Received: 30 June 2016 / Revised: 13 July 2016 / Accepted: 14 July 2016 / Published: 19 July 2016
Cited by 5 | PDF Full-text (1702 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two new mononuclear iron(II) compounds (1) and (2) of the general formula [Fe(L)2](BF4)2·nCH3CN (L = 4-(2-bromoethyn-1-yl)-2,6-bis(pyrazol-1-yl)pyridine, n = 1 for (1) and n = 2 for
[...] Read more.
Two new mononuclear iron(II) compounds (1) and (2) of the general formula [Fe(L)2](BF4)2·nCH3CN (L = 4-(2-bromoethyn-1-yl)-2,6-bis(pyrazol-1-yl)pyridine, n = 1 for (1) and n = 2 for compound (2)), were synthesized. The room temperature crystallization afforded concomitant formation of two different solvent analogues: compound (1) exhibiting triclinic P-1 and compound (2) monoclinic C2/c symmetry. Single-crystal X-ray studies confirmed the presence of the LS (low-spin) state for both compounds at 180 K and of the HS (high-spin) state for compound (2) at 293 K, in full agreement with the magnetic investigations for both solvent polymorphs. Compound (1) exhibits spin transition above 293 K followed by subsequent solvent liberation, while the spin transition of (2) takes already place at 237 K. After complete solvent removal from the crystal lattice, compound (1d) (the desolvated polymorph derived from (1)) exhibits spin transition centered at 342 K accompanied by a thermal hysteresis loop, while the analogous compound (2d) (the desolvated derivate of compound (2)) remains blocked in the HS state over all the investigated temperature range. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
Open AccessArticle In Situ AFM Imaging of Microstructural Changes Associated with The Spin Transition in [Fe(Htrz)2(Trz)](Bf4) Nanoparticles
Materials 2016, 9(7), 537; doi:10.3390/ma9070537
Received: 6 June 2016 / Revised: 23 June 2016 / Accepted: 28 June 2016 / Published: 30 June 2016
Cited by 6 | PDF Full-text (2645 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Topographic images of [Fe(Htrz)2(trz)](BF4) nanoparticles were acquired across the first-order spin transition using variable-temperature atomic force microscopy (AFM) in amplitude modulation mode. These studies revealed a complex morphology of the particles consisting of aggregates of small nanocrystals, which expand,
[...] Read more.
Topographic images of [Fe(Htrz)2(trz)](BF4) nanoparticles were acquired across the first-order spin transition using variable-temperature atomic force microscopy (AFM) in amplitude modulation mode. These studies revealed a complex morphology of the particles consisting of aggregates of small nanocrystals, which expand, separate and re-aggregate due to the mechanical stress during the spin-state switching events. Both reversible (prompt or slow recovery) and irreversible effects (fatigue) on the particle morphology were evidenced and correlated with the spin crossover properties. Full article
(This article belongs to the Special Issue Advances in Molecular Magnets and related Phenomena)
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