Special Issue "Synthesis and Applications of New Spin Crossover Compounds"

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: 30 September 2018

Special Issue Editor

Guest Editor
Prof. Dr. Takafumi Kitazawa

1. Department of Chemistry, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan
2. Research Centre for Materials with Integrated Properties, Toho University, 2-2-1 Miyama, Funabashi,Chiba 274-8510, Japan
Website | E-Mail
Phone: +81-47-472-5077
Interests: Spin Crossover Compounds, Inclusion Compounds, Clathrate, Mineralomimetic Chemistry, Mössbauer Spectroscopy, Molecular Magnetism; Coordnination Polymer

Special Issue Information

Dear Colleagues,

The magnetochemistry research area of spin crossover (SCO) behavior in coordination compounds might be potentially associated with smart materials, promising materials for applications as components of memory devices, displays and sensors. 3-d block transition metal coordination compounds with d4-d7 configuration in an octahedral crystal field have a possibility of SCO phenomena between the low spin (LS) and the high spin (HS) states, being accompanied by color changes. Octahedral iron(II) SCO systems with 3d6, which can be transited between the diamagnetic (t2g)6 and the paramagnetic (t2g)4(eg)2 configuration might be widely and deeply investigated as smart materials.

Coordination materials with bistable systems between the LS and the HS states, usually triggered by external stimuli, such as temperature, light, pressure and guest molecule inclusion, are a family of potential candidates for smart materials because the change of the crystal cell volume between the HS and LS states is very large. Various SCO iron(II) coordination compounds, especially those with polymeric 1D, 2D and 3D frameworks, have been intensively investigated because their polymeric linked framework structures enhance cooperative effects which work among the SCO species resulting in SCO behavior with large hysteresis and transition temperature ranges near RT.

The interdisciplinary regions chemistry related to spin crossover phenomena are also welcome.

We are hoping to offer a portal for some of this exciting new research associated with molecular magnetism, spin crossover phenomena, coordination polymers, metallosupramolecular chemistry, multiproperty materials and functional materials with an attractive and valuable Special Issue of the open access journal, Crystals.

Prof. Dr. Takafumi Kitazawa
Guest Editor

Manuscript Submission Information

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Keywords

  • Spin crossover
  • High spin
  • Low spin
  • Switching magnetic materials
  • Sensor
  • Smart materials
  • Supuramolecular coordination polymer
  • Inclusion compounds with magnetism

Published Papers (2 papers)

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Research

Open AccessArticle Mosaicity of Spin-Crossover Crystals
Crystals 2018, 8(9), 363; https://doi.org/10.3390/cryst8090363
Received: 28 August 2018 / Revised: 11 September 2018 / Accepted: 11 September 2018 / Published: 13 September 2018
PDF Full-text (1767 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Real crystals are composed of a mosaic of domains whose misalignment is evaluated by their level of “mosaicity” using X-ray diffraction. In thermo-induced spin-crossover compounds, the crystal may be seen as a mixture of metal centres, some being in the high-spin (HS) state
[...] Read more.
Real crystals are composed of a mosaic of domains whose misalignment is evaluated by their level of “mosaicity” using X-ray diffraction. In thermo-induced spin-crossover compounds, the crystal may be seen as a mixture of metal centres, some being in the high-spin (HS) state and others in the low spin (LS) state. Since the volume of HS and LS crystal packings are known to be very different, the assembly of domains within the crystal, i.e., its mosaicity, may be modified at the spin crossover. With little data available in the literature we propose an investigation into the temperature dependence of mosaicity in certain spin-crossover crystals. The study was preceded by the examination of instrumental factors, in order to establish a protocol for the measurement of mosaicity. The results show that crystal mosaicity appears to be strongly modified by thermal spin-crossover; however, the nature of the changes are probably sample dependent and driven, or masked, in most cases by the characteristics of the crystal (disorder, morphology …). No general relationship could be established between mosaicity and crystal properties. If, however, mosaicity studies in spin-crossover crystals are conducted and interpreted with great care, they could help to elucidate crucial crystal characteristics such as mechanical fatigability, and more generally to investigate systems where phase transition is associated with large volume changes. Full article
(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)
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Figure 1

Open AccessArticle Cobalt(II) Terpyridin-4′-yl Nitroxide Complex as an Exchange-Coupled Spin-Crossover Material
Crystals 2018, 8(4), 155; https://doi.org/10.3390/cryst8040155
Received: 2 March 2018 / Revised: 26 March 2018 / Accepted: 29 March 2018 / Published: 2 April 2018
PDF Full-text (3672 KB) | HTML Full-text | XML Full-text
Abstract
Spin-crossover (SCO) was studied in [Co(L)2](CF3SO3)2, where L stands for diamagnetic 2,2′:6′,2′′-terpyridine (tpy) and its paramagnetic derivative, 4′-{4-tert-butyl(N-oxy)aminophenyl}-substituted tpy (tpyphNO). The X-ray crystallographic analysis clarified the Co-N bond length change (Δ
[...] Read more.
Spin-crossover (SCO) was studied in [Co(L)2](CF3SO3)2, where L stands for diamagnetic 2,2′:6′,2′′-terpyridine (tpy) and its paramagnetic derivative, 4′-{4-tert-butyl(N-oxy)aminophenyl}-substituted tpy (tpyphNO). The X-ray crystallographic analysis clarified the Co-N bond length change (Δd) in high- and low-temperature structures; Δdcentral = 0.12 and Δddistal = 0.05 Å between 90 and 400 K for L = tpy and Δdcentral = 0.11 and Δddistal = 0.06 Å between 90 and 300 K for L = tpyphNO. The low- and high-temperature structures can be assigned to approximate low- and high-spin states, respectively. The magnetic susceptibility measurements revealed that the χmT value of [Co(tpyphNO)2](CF3SO3)2 had a bias from that of [Co(tpy)2](CF3SO3)2 by the contribution of the two radical spins. The tpy compound showed a gradual SCO around 260 K and on cooling the χmT value displayed a plateau down to 2 K. On the other hand, the tpyphNO compound showed a relatively abrupt SCO at ca. 140 K together with a second decrease of the χmT value on further cooling below ca. 20 K. From the second decrease, Co-nitroxide exchange coupling was characterized as antiferromagnetic with 2JCo-rad/kB = −3.00(6) K in the spin-Hamiltonian H = −2JCo-rad(SCo·Srad1 + SCo·Srad2). The magnetic moment apparently switches double-stepwise as 1 μB 3 μB 5 μB by temperature stimulus. Full article
(This article belongs to the Special Issue Synthesis and Applications of New Spin Crossover Compounds)
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