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A Brønsted ligand molecular switch with five accessible states

Shiga, Takuya; Saiki, Ryo; Akiyama, Lisa; Kumai, Reiji; Natke, Dominik; Renz, Franz; Cameron, Jamie; Newton, Graham; Oshio, Hiroki

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Takuya Shiga

Ryo Saiki

Lisa Akiyama

Reiji Kumai

Dominik Natke

Franz Renz

Jamie Cameron

Hiroki Oshio


A mononuclear Fe(II) complex, prepared with a Brønsted diacid ligand, H2L (H2L = 2-[5-phenyl-1H-pyrazole-3-yl] 6benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [FeII(H2L)2](BF4)2 (1A), exhibits abrupt spin transition at T1/2 = 258 K, and treatment with base yields a deprotonated analogue [FeII(HL)2] (1B), which shows gradual SCO above 350 K. A range of ferric analogues were also characterized. [FeIII(HL)(H2L)](BF4)Cl (1C) has an S = 5/2 spin state, while the deprotonated complexes [FeIII(L)(HL)], (1D), and (TEA)[FeIII(L)2], (1E) exist in the low-spin S = 1/2 state. The electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid-state. The versatility of this simple mononuclear system illustrates how proton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.


Shiga, T., Saiki, R., Akiyama, L., Kumai, R., Natke, D., Renz, F., …Oshio, H. (2019). A Brønsted ligand molecular switch with five accessible states. Angewandte Chemie International Edition, 58(17), 5658-5662.

Journal Article Type Article
Acceptance Date Feb 4, 2019
Online Publication Date Feb 12, 2019
Publication Date Apr 16, 2019
Deposit Date Mar 15, 2019
Publicly Available Date Feb 13, 2020
Journal Angewandte Chemie International Edition
Print ISSN 1433-7851
Electronic ISSN 1521-3773
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 58
Issue 17
Pages 5658-5662
Public URL
Publisher URL
Additional Information This is the peer reviewed version of the following article: Shiga, T. , Saiki, R. , Akiyama, L. , Kumai, R. , Natke, D. , Renz, F. , Cameron, J. , Newton, G. and Oshio, H. (2019), A Brønsted ligand molecular switch with five accessible states. Angew. Chem. Int. Ed. which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.


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