Measurement of Extreme hyperfine fields in two-coordinate high-spin Fe2+ complexes by mössbauer Spectroscopy: Essentially Free-Ion Magnetism in the Solid State

Aimee M. Bryan, Chun Yi Lin, Michio Sorai, Yuji Miyazaki, Helen M. Hoyt, Annelise Hablutzel, Anne Lapointe, William M. Reiff, Philip P. Power, Charles E. Schulz

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10 Citations (Scopus)

Abstract

Mössbauer studies of three two-coordinate linear high-spin Fe2+ compounds, namely, Fe{N(SiMe3)(Dipp)}2 (1) (Dipp = C6H3-2,6-iPr2), Fe(OAr′)2 (2) [Ar′ = C6H3-2,6-(C6H3-2,6-iPr2)2], and Fe{C(SiMe3)3}2 (3), are presented. The complexes were characterized by zero- and applied-field Mössbauer spectroscopy (1-3), as well as zero- and applied-field heat-capacity measurements (3). As 1-3 are rigorously linear, the distortion(s) that might normally be expected in view of the Jahn-Teller theorem need not necessarily apply. We find that the resulting very large unquenched orbital angular momentum leads to what we believe to be the largest observed internal magnetic field to date in a high-spin iron(II) compound, specifically +162 T in 1. The latter field is strongly polarized along the directions of the external field for both longitudinal and transverse field applications. For the longitudinal case, the applied field increases the overall hyperfine splitting consistent with a dominant orbital contribution to the effective internal field. By contrast, 2 has an internal field that is not as strongly polarized along a longitudinally applied field and is smaller in magnitude at ca. 116 T. Complex 3 behaves similarly to complex 1. They are sufficiently self-dilute (e.g., Fe···Fe distances of ca. 9-10 Å) to exhibit varying degrees of slow paramagnetic relaxation in zero field for the neat solid form. In the absence of EPR signals for 1-3, we show that heat-capacity measurements for one of the complexes (3) establish a geff value near 12, in agreement with the principal component of the ligand electric field gradient being coincident with the z axis.

Original languageEnglish
Pages (from-to)12100-12107
Number of pages8
JournalInorganic Chemistry
Volume53
Issue number22
DOIs
Publication statusPublished - 2014 Nov 17

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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