Molecular Magnetism of Transition Metal Complexes

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 December 2019) | Viewed by 6480

Special Issue Editor


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Guest Editor
Department of Inorganic Chemistry, Faculty of Science, Palacký University Olomouc, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic
Interests: ccoordination chemistry; transition metal complexes (Mn, Fe, Co, Ni, etc.); spin-crossover; molecular magnets; chemistry of contrast agents for Magnetic Resonance Imaging (Mn2+ and Gd3+ complexes)

Special Issue Information

Dear Colleagues,

The field of molecular magnetism has become an important part of coordination chemistry. Single-molecule magnets (SMMs), mononuclear SMMs, so-called single-ion magnets (SIMs), and single-chain magnets (SCMs) are compounds exhibiting slow relaxation of magnetization based on a pure molecular origin (without any long-range ordering typical for “bulk” magnets). The interest in this class of complexes is driven by their promising application potential in ultradense information storage, quantum computing and spintronics. Nevertheless, they operate at very low temperatures (currently up to 80 K) so far. In order to overcome this problem, it is necessary to tune/increase the magnetic anisotropy of complexated metal ions by a rational ligand design and to understand all parameters governing the process of relaxation of magnetization. Unfortunately, this is still a challenge for coordination chemists and therefore more magneto-structural correlations, as well as in-depth investigation of dynamic magnetic processes, are required.

Other important sub-class in molecular magnetism represents complexes showing spin crossover (SCO), which is the spin transition between high-spin and low-spin state usually induced by different external constraints (e.g., temperature, pressure or light). Such compounds can find many interesting applications including molecular switches, sensors, or display technologies, etc. Seeking for new systems with adequate abruptness, temperature and other characteristics of the spin transition is still in the center of attention in order to reveal structural parameters responsible for the concrete SCO behavior consequently providing information how to fabricate advanced SCO materials.

Thus, it is a great pleasure for me to invite you to participate in this Special Issue, which should provide the most recent developments and advances in the above-mentioned topics concerning SMMs, SIMs, SCMs, tuning of magnetic anisotropy, investigation of relaxation processes in molecular magnets, and also new SCO systems. 

Dr. Bohuslav Drahos
Guest Editor

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Keywords

  • Single-molecule magnet (SMM)
  • Single-ion magnet (SIM)
  • Single-chain magnet (SCM)
  • Magnetic anisotropy
  • Zero-field splitting (ZFS)
  • Relaxation of magnetization
  • Spin crossover (SCO)
  • Transition metal complex

Published Papers (2 papers)

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Research

13 pages, 2352 KiB  
Article
Magnetic Properties of Fe(II) Complexes of Cyclam Derivative with One p-Aminobenzyl Pendant Arm
by Bohuslav Drahoš, Peter Antal, Ivan Šalitroš and Radovan Herchel
Metals 2020, 10(3), 366; https://doi.org/10.3390/met10030366 - 12 Mar 2020
Cited by 3 | Viewed by 2319
Abstract
In order to prepare an Fe(II) spin crossover (SCO) complex that could be consequently modified to a bimetallic coordination compound that possesses another magnetic property of interest, a specially designed ligand L-NH2 (1-(4-aminobenzyl)-4,11-bis(pyridine-2-ylmethyl)- 1,4,8,11-tetraazacyclotetradecane) was prepared. This ligand consists of a macrocyclic [...] Read more.
In order to prepare an Fe(II) spin crossover (SCO) complex that could be consequently modified to a bimetallic coordination compound that possesses another magnetic property of interest, a specially designed ligand L-NH2 (1-(4-aminobenzyl)-4,11-bis(pyridine-2-ylmethyl)- 1,4,8,11-tetraazacyclotetradecane) was prepared. This ligand consists of a macrocyclic cyclam part containing two 2-pyridylmethyl pendant arms (expecting SCO upon Fe(II) complexation) and one p-aminobenzyl pendant arm with an NH2 group. The presence of this group enables the consequent transformation to various functional groups for the selective complexation of other transition metals or lanthanides (providing the second property of interest). Furthermore, the performed theoretical calculations (TPSSh/def2-TZVP) predicted SCO behavior for the Fe(II) complex of L-NH2. Thus, Fe(II) complexes [Fe(L-NH2)](ClO4)2 (1) and [Fe(L-NH2)]Cl2·6H2O (2) were synthesized and thoroughly characterized. Based on the crystal structure of an isostructural analogous Ni(II) complex [Ni(L-NH2)]Cl2·6H2O (3), the coordination number six was confirmed with an octahedral coordination sphere and a cis-arrangement of the pyridine pendant arms. The measured magnetic data confirmed the high-spin behavior of both compounds with large magnetic anisotropy (D = 17.8 for 1 and 20.9 cm−1 for 2 complemented in both cases also with large rhombicity), though unfortunately without any indication of the SCO behavior with decreasing temperature. The lack of SCO can be ascribed to the crystal packing and/or the non-covalent intermolecular interactions stabilizing the high-spin state in the solid state. Full article
(This article belongs to the Special Issue Molecular Magnetism of Transition Metal Complexes)
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11 pages, 1521 KiB  
Article
Spin Crossover in Three Mononuclear Iron (III) Schiff Base Complexes
by Ivan Nemec, Ingrid Svoboda and Radovan Herchel
Metals 2019, 9(8), 849; https://doi.org/10.3390/met9080849 - 02 Aug 2019
Cited by 5 | Viewed by 3678
Abstract
The synthesis, crystal structure, and magnetic properties of three new mononuclear complexes [Fe(R-LA)(L1)](BPh4), where R-LA2− is a doubly deprotonated pentadentate Schiff base ligand and L1 is a monodentate benzimidazole or furopyridine ligand, are reported. Ligand- and anion-driven changes in crystal structures and [...] Read more.
The synthesis, crystal structure, and magnetic properties of three new mononuclear complexes [Fe(R-LA)(L1)](BPh4), where R-LA2− is a doubly deprotonated pentadentate Schiff base ligand and L1 is a monodentate benzimidazole or furopyridine ligand, are reported. Ligand- and anion-driven changes in crystal structures and magnetic behavior were investigated in terms of the magnetic susceptibility measurements and theoretical calculations. Full article
(This article belongs to the Special Issue Molecular Magnetism of Transition Metal Complexes)
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