As-Se Pentagonal Linkers to Induce Chirality and Polarity in Mixed-Valent Fe-Se Tetrahedral Chains Resulting in Hidden Magnetic Ordering

Eranga H Gamage; Saeed Kamali; Judith K Clark; Yongbin Lee; Philip Yox; Padraic Shafer; Alexander A Yaroslavtsev; Liqin Ke; Michael Shatruk; Kirill Kovnir

doi:10.1021/jacs.2c02936

As-Se Pentagonal Linkers to Induce Chirality and Polarity in Mixed-Valent Fe-Se Tetrahedral Chains Resulting in Hidden Magnetic Ordering

J Am Chem Soc. 2022 Jun 29;144(25):11283-11295. doi: 10.1021/jacs.2c02936. Epub 2022 Jun 14.

Authors

Eranga H Gamage^{1

2}, Saeed Kamali^{3

4}, Judith K Clark⁵, Yongbin Lee², Philip Yox^{1

2}, Padraic Shafer⁶, Alexander A Yaroslavtsev⁷, Liqin Ke², Michael Shatruk^{5

8}, Kirill Kovnir^{1

2}

Affiliations

¹ Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States.
² Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, United States.
³ Mechanical, Aerospace & Biomedical Engineering Department, University of Tennessee Space Institute, Tullahoma, Tennessee 37388, United States.
⁴ Department of Physics and Astronomy, Middle Tennessee State University, Murfreesboro, Tennessee 37132, United States.
⁵ Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.
⁶ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
⁷ Department of Physics and Astronomy, Uppsala University, Uppsala 75120, Sweden.
⁸ National High Magnetic Field Laboratory, 1800 E Paul Dirac Dr, Tallahassee, Florida 32310, United States.

PMID: 35700396
DOI: 10.1021/jacs.2c02936

Abstract

A novel mixed-valent hybrid chiral and polar compound, Fe₇As₃Se₁₂(en)₆(H₂O), has been synthesized by a single-step solvothermal method. The crystal structure consists of 1D [Fe₅Se₉] chains connected via [As₃Se₂]-Se pentagonal linkers and charge-balancing interstitial [Fe(en)₃]²⁺ complexes (en = ethylenediamine). Neutron powder diffraction verified that interstitial water molecules participate in the crystal packing. Magnetic polarizability of the produced compound was confirmed by X-ray magnetic circular dichroism (XMCD) spectroscopy. X-ray absorption spectroscopy (XAS) and ⁵⁷Fe Mössbauer spectroscopy showed the presence of mixed-valent Fe²⁺/Fe³⁺ in the Fe-Se chains. Magnetic susceptibility measurements reveal strong antiferromagnetic nearest neighbor interactions within the chains with no apparent magnetic ordering down to 2 K. Hidden short-range magnetic ordering below 70 K was found by ⁵⁷Fe Mössbauer spectroscopy, showing that a fraction of the Fe³⁺/Fe²⁺ in the chains are magnetically ordered. Nevertheless, complete magnetic ordering is not achieved even at 6 K. Analysis of XAS spectra demonstrates that the fraction of Fe³⁺ in the chain increases with decreasing temperature. Computational analysis points out several competing ferrimagnetic ordered models within a single chain. This competition, together with variation in the Fe oxidation state and additional weak intrachain interactions, is hypothesized to prevent long-range magnetic ordering.