Metal-Metal-Bonded Fe4 Clusters with Slow Magnetic Relaxation

Phoebe R Hertler; Linus Kautzsch; Alexander J Touchton; Guang Wu; Trevor W Hayton

doi:10.1021/acs.inorgchem.2c00865

Metal-Metal-Bonded Fe₄ Clusters with Slow Magnetic Relaxation

Inorg Chem. 2022 Jul 4;61(26):9997-10005. doi: 10.1021/acs.inorgchem.2c00865. Epub 2022 Jun 16.

Authors

Phoebe R Hertler¹, Linus Kautzsch², Alexander J Touchton¹, Guang Wu¹, Trevor W Hayton¹

Affiliations

¹ Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States.
² Materials Department and Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California 93106, United States.

PMID: 35709487
DOI: 10.1021/acs.inorgchem.2c00865

Abstract

Reaction of FeBr₂ with Li(N═C^tBu₂) (0.5 equiv) and Zn⁰ (2 equiv) results in the formation of the formally mixed-valent cluster [Fe₄Br₂(N═C^tBu₂)₄] (1) in moderate yield. The subsequent reaction of 1 with Na(N═C^tBu₂) results in formation of [Fe₄Br(N═C^tBu₂)₅] (2), also in moderate yield. Both 1 and 2 were characterized by zero-field ⁵⁷Fe Mössbauer spectroscopy, X-ray crystallography, and superconducting quantum interference device magnetometry. Their tetrahedral [Fe₄]⁶⁺ cores feature short Fe-Fe interactions (ca. 2.50 Å). Additionally, both 1 and 2 display S = 7 ground states at room temperature and slow magnetic relaxation with zero-field relaxation barriers of U_eff = 14.7(4) and 15.6(7) cm^-1, respectively. Moreover, AC magnetic susceptibility measurements were well modeled by assuming an Orbach relaxation process.