Observation of Proton Transfer Coupled Spin Transition and Trapping of Photoinduced Metastable Proton Transfer State in an Fe(II) Complex

Takumi Nakanishi, Yuta Hori, Hiroyasu Sato, Shu Qi Wu, Atsushi Okazawa, Norimichi Kojima, Takashi Yamamoto, Yasuaki Einaga, Shinya Hayami, Yusuke Horie, Hajime Okajima, Akira Sakamoto, Yoshihito Shiota, Kazunari Yoshizawa, Osamu Sato

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

An important technique to realize novel electron- and/or proton-based functionalities is to use a proton-electron coupling mechanism. When either a proton or electron is excited, the other one is modulated, producing synergistic functions. However, although compounds with proton-coupled electron transfer have been synthesized, crystalline molecular compounds that exhibit proton-transfer-coupled spin-transition (PCST) behavior have not been reported. Here, we report the first example of a PCST Fe(II) complex, wherein the proton lies on the N of hydrazone and pyridine moieties in the ligand at high-spin and low-spin Fe(II), respectively. When the Fe(II) complex is irradiated with light, intramolecular proton transfer occurs from pyridine to hydrazone in conjunction with the photoinduced spin transition via the PCST mechanism. Because the light-induced excited high-spin state is trapped at low temperatures in the Fe(II) complex-a phenomenon known as the light-induced excited-spin-state trapping effect-the light-induced proton-transfer state, wherein the proton lies on the N of hydrazone, is also trapped as a metastable state. The proton transfer was accomplished within 50 ps at 190 K. The bistable nature of the proton position, where the position can be switched by light irradiation, is useful for modulating proton-based functionalities in molecular devices.

Original languageEnglish
Pages (from-to)14384-14393
Number of pages10
JournalJournal of the American Chemical Society
Volume141
Issue number36
DOIs
Publication statusPublished - 2019 Sep 11

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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    Nakanishi, T., Hori, Y., Sato, H., Wu, S. Q., Okazawa, A., Kojima, N., Yamamoto, T., Einaga, Y., Hayami, S., Horie, Y., Okajima, H., Sakamoto, A., Shiota, Y., Yoshizawa, K., & Sato, O. (2019). Observation of Proton Transfer Coupled Spin Transition and Trapping of Photoinduced Metastable Proton Transfer State in an Fe(II) Complex. Journal of the American Chemical Society, 141(36), 14384-14393. https://doi.org/10.1021/jacs.9b07204