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Updated: May 14, 2026
Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
Published on: June 9, 2023
Bis[(E)-2,6-bis(1H-pyrazol-1-yl)-4-styrylpyridine]iron(II) complex: relationship between thermal spin crossover and
Yuta Hasegawa1, Ryota Sakamoto, Kazuhiro Takahashi
1Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract:
The crystal structures and thermal spin-crossover (SCO) behavior of [Fe(E-dpsp)(2)](BF(4))(2)·X [E-dpsp = (E)-2,6-bis(1H-pyrazol-1-yl)-4-styrylpyridine; X = crystal solvent] are investigated. The titled iron(II) complex features polymorphology induced by crystal solvents, which is identified by means of single-crystal X-ray diffraction analysis: For [Fe(E-dpsp)(2)](BF(4))(2)·acetone and [Fe(E-dpsp)(2)](BF(4))(2)·4MeNO(2), detailed analyses at various temperatures are conducted. The magnetic properties of bulk microcrystalline samples of [Fe(E-dpsp)(2)](BF(4))(2)·X are assessed using a SQUID magnetometer. Among the series, only [Fe(E-dpsp)(2)](BF(4))(2)·acetone undergoes peculiar thermal SCO, such as a precipitous and hysteretic spin-state change (T(1/2↑) = 179 K, T(1/2↓) = 164 K, and ΔT(1/2) = 15 K) and frozen-in effect. All single crystals of [Fe(E-dpsp)(2)](BF(4))(2)·X are free from intermolecular interaction except for [Fe(E-dpsp)(2)](BF(4))(2)·acetone: One of the phenyl rings in [Fe(E-dpsp)(2)](BF(4))(2)·acetone is twisted appreciably and features an intermolecular H-H short contact with one of the neighboring complexes to form a one-dimensional network. The twisted phenyl group also participates in π-π stacking with one of the pyrazolyl rings of another neighboring molecule, constructing a dimeric couple. These intermolecular interactions would induce cooperative effects, which leads to the good thermal SCO phenomenon of [Fe(E-dpsp)(2)](BF(4))(2)·acetone.
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