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Title: Maximizing Electron Exchange in a [F 3] Cluster

Abstract

The one-electron reduction of ( tbsL)Fe 3(thf) 1 furnishes [M][( tbsL)Fe 3] ([M] + = [(18-C-6)K(thf) 2] + (1, 76%) or [(crypt-222)K] + (2, 54%)). Upon reduction, the ligand tbsL 6- rearranges around the triiron core to adopt an almost ideal C 3-symmetry. Accompanying the ( tbsL) ligand rearrangement, the THF bound to the neutral starting material is expelled, and the Fe–Fe distances within the trinuclear cluster contract by ~0.13 Å in 1. Variable-temperature magnetic susceptibility data indicates a well-isolated spin ground state that persists to room temperature. Slow magnetic relaxation is observed at low temperature as evidenced by the out-of-phase component of the alternating current (ac) magnetic susceptibility data and by the appearance of hyperfine splitting in the zero-field 57Fe Mössbauer spectra at 4.2 K. Analysis of the ac magnetic susceptibility yields an effective spin reversal barrier (U eff) of 22.6(2) cm -1, nearly matching the theoretical barrier of 38.7 cm -1 calculated from the axial zero-field splitting parameter (D = -1.29 cm -1) extracted from the reduced magnetization data. A polycrystalline sample of 1 displays three sextets in the Mössbauer spectrum at 4.2 K (H ext = 0) which converge to a single six-line pattern in a frozenmore » 2-MeTHF glass sample, indicating a unique iron environment and thus strong electron delocalization. The spin ground state and ligand rearrangement are discussed within the framework of a fully delocalized cluster exhibiting strong double and direct exchange interactions.« less

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Harvard Univ., Cambridge, MA (United States)
Publication Date:
Research Org.:
Harvard Univ., Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1467658
Grant/Contract Number:  
SC0008313
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 138; Journal Issue: 7; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Hernández Sánchez, Raúl, Bartholomew, Amymarie K., Powers, Tamara M., Ménard, Gabriel, and Betley, Theodore A.. Maximizing Electron Exchange in a [F 3] Cluster. United States: N. p., 2016. Web. doi:10.1021/jacs.5b12181.
Hernández Sánchez, Raúl, Bartholomew, Amymarie K., Powers, Tamara M., Ménard, Gabriel, & Betley, Theodore A.. Maximizing Electron Exchange in a [F 3] Cluster. United States. doi:10.1021/jacs.5b12181.
Hernández Sánchez, Raúl, Bartholomew, Amymarie K., Powers, Tamara M., Ménard, Gabriel, and Betley, Theodore A.. Fri . "Maximizing Electron Exchange in a [F 3] Cluster". United States. doi:10.1021/jacs.5b12181. https://www.osti.gov/servlets/purl/1467658.
@article{osti_1467658,
title = {Maximizing Electron Exchange in a [F 3] Cluster},
author = {Hernández Sánchez, Raúl and Bartholomew, Amymarie K. and Powers, Tamara M. and Ménard, Gabriel and Betley, Theodore A.},
abstractNote = {The one-electron reduction of (tbsL)Fe3(thf)1 furnishes [M][(tbsL)Fe3] ([M]+ = [(18-C-6)K(thf)2]+ (1, 76%) or [(crypt-222)K]+ (2, 54%)). Upon reduction, the ligand tbsL6- rearranges around the triiron core to adopt an almost ideal C3-symmetry. Accompanying the (tbsL) ligand rearrangement, the THF bound to the neutral starting material is expelled, and the Fe–Fe distances within the trinuclear cluster contract by ~0.13 Å in 1. Variable-temperature magnetic susceptibility data indicates a well-isolated spin ground state that persists to room temperature. Slow magnetic relaxation is observed at low temperature as evidenced by the out-of-phase component of the alternating current (ac) magnetic susceptibility data and by the appearance of hyperfine splitting in the zero-field 57Fe Mössbauer spectra at 4.2 K. Analysis of the ac magnetic susceptibility yields an effective spin reversal barrier (Ueff) of 22.6(2) cm-1, nearly matching the theoretical barrier of 38.7 cm-1 calculated from the axial zero-field splitting parameter (D = -1.29 cm-1) extracted from the reduced magnetization data. A polycrystalline sample of 1 displays three sextets in the Mössbauer spectrum at 4.2 K (Hext = 0) which converge to a single six-line pattern in a frozen 2-MeTHF glass sample, indicating a unique iron environment and thus strong electron delocalization. The spin ground state and ligand rearrangement are discussed within the framework of a fully delocalized cluster exhibiting strong double and direct exchange interactions.},
doi = {10.1021/jacs.5b12181},
journal = {Journal of the American Chemical Society},
number = 7,
volume = 138,
place = {United States},
year = {2016},
month = {1}
}

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