Three-Step Spin State Transition and Hysteretic Proton Transfer in the Crystal of an Iron(II) Hydrazone Complex

Takumi Nakanishi, Yuta Hori, Shuqi Wu, Hiroyasu Sato, Atsushi Okazawa, Norimichi Kojima, Yusuke Horie, Hajime Okajima, Akira Sakamoto, Yoshihito Shiota, Kazunari Yoshizawa, Osamu Sato*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


A proton–electron coupling system, exhibiting unique bistability or multistability of the protonated state, is an attractive target for developing new switchable materials based on proton dynamics. Herein, we present an iron(II) hydrazone crystalline compound, which displays the stepwise transition and bistability of proton transfer at the crystal level. These phenomena are realized through the coupling with spin transition. Although the multi-step transition with hysteresis has been observed in various systems, the corresponding behavior of proton transfer has not been reported in crystalline systems; thus, the described iron(II) complex is the first example. Furthermore, because proton transfer occurs only in one of the two ligands and π electrons redistribute in it, the dipole moment of the iron(II) complexes changes with the proton transfer, wherein the total dipole moment in the crystal was canceled out owing to the antiferroelectric-like arrangement.

Original languageEnglish
Pages (from-to)14781-14787
Number of pages7
JournalAngewandte Chemie - International Edition
Issue number35
Publication statusPublished - 2020 Aug 24
Externally publishedYes


  • hydrazone complexes
  • proton transfer
  • solid-state chemistry
  • spin crossover
  • switchable materials

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)


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